WO2025227014A1

WO2025227014A1 - In-vessel sheath dilator

Info

Publication number: WO2025227014A1
Application number: PCT/US2025/026333
Authority: WO
Inventors: Michael C. MURAD; Jennifer Marie REITMAJER; Allison Nicole RABIN; Roy SHITRIT
Original assignee: Edwards Lifesciences Corp
Current assignee: Edwards Lifesciences Corp
Priority date: 2024-04-26
Filing date: 2025-04-25
Publication date: 2025-10-30
Anticipated expiration: 2026-10-26

Abstract

A sheath for minimizing trauma to the patient's vasculature by including a dilator (300) comprising a shaft (302) with a tapered distal end (304) to reduce the push forces required to insert the dilator shaft (302) and reduce axial shortening associated with sheath expansion. The dilator shaft (302) includes the tapered distal end (304) with a ridge (306) projecting from an outer surface of the tapered distal end, where the ridge defines a maximum outer diameter of the introducer shaft. The dilator shaft can have at least one dilating portion that defines a maximum outer diameter of the dilator shaft, where the diameter of the dilating portion is greater than a diameter of the elongated body portion of the dilator shaft. The dilator shaft can have a first distal end and a second distal end, with a first and second dilating portion proximal to each end.

Description

IN- VESSEL SHEATH DILATOR

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/639,043, filed April 26, 2024, which is incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

[0002] The present application is directed to an expandable sheath and dilator system for use with catheter-based technologies for repairing and/or replacing heart valves, as well as for delivering an implant, such as a prosthetic valve to a heart via the patient’s vasculature.

BACKGROUND OF THE INVENTION

[0003] Endovascular delivery catheter assemblies are used to implant prosthetic devices, such as a prosthetic valve, at locations inside the body that are not readily accessible by surgery or where access without invasive surgery is desirable. For example, aortic, mitral, tricuspid, and/or pulmonary prosthetic valves can be delivered to a treatment site using minimally invasive surgical techniques.

[0004] Percutaneous interventional medical procedures utilize the large blood vessels of the body to reach target destinations rather than surgically opening a target site. There are many types of diseases or states that can be treated via interventional methods including coronary blockages, valve replacements (TAVR) and brain aneurysms. These techniques involve using wires, catheters, balloons, electrodes and other thin devices to travel down the length of the blood vessels from the access site to the target site. The devices have a proximal end which the clinician controls outside of the body and a distal end inside the body, which is responsible for treating the disease state. Percutaneous interventional procedures offer several advantages over open surgical techniques. First, they require smaller incision sites, which reduces scarring and bleeding as well as infection risk. Procedures are also less traumatic to the tissue, so recovery times are reduced. Finally, interventional techniques can usually be performed much faster, and with fewer clinicians participating in the procedure, so overall costs are lowered. In some cases, the need for anesthesia is also eliminated, further speeding up the recovery process and reducing risk.

[0005] A single procedure typically uses several different guidewires, catheters, and balloons to achieve the desired effect. One at a time, each tool is inserted and then removed from the access site sequentially. For example, a guidewire is used to track to the correct location within the body. Next a balloon may be used to dilate a section of narrowed blood vessel. Last, an implant may be delivered to the target site. Because catheters are frequently inserted and removed, introducer sheaths are used to protect the local anatomy and simplify the procedure.

[0006] An introducer sheath can be used to safely introduce a delivery apparatus into a patient’s vasculature (for example, the femoral artery). Introducer sheaths are conduits that seal onto the access site blood vessel to reduce bleeding and trauma to the vessel caused by catheters with rough edges. An introducer sheath generally has an elongated sleeve that is inserted into the vasculature and a housing that contains one or more sealing valves that allow a delivery apparatus to be placed in fluid communication with the vasculature with minimal blood loss. Once the introducer sheath is positioned within the vasculature, the shaft of the delivery apparatus is advanced through the sheath and into the vasculature, carrying the prosthetic device. Expandable introducer sheaths, formed of highly elastomeric materials, allow for the dilating of the vessel to be performed by the passing prosthetic device.

[0007] One method to reduce push forces through the blood vessel and minimize vessel trauma, is to provide a sheath and introducer with as minimal diameter as possible. However, very thin delivery sheaths present challenges of strength and durability. Additionally or alternatively, thicker layered sheaths can be provided but necessitate high push forces to advance the delivery device/implant through the sheath. One method to reduce push forces through the sheath is to pre-dilate the sheath by passing a relatively large dilator (for example, 22 French dilator) into the sheath. This is done during sheath prep, prior to sheath insertion into the patient and/or with the sheath at least partially inserted into the patient. The challenge with this method is that it can be difficult with regard to physical strength of the user (for example, grip and arm strength) to advance the dilator into sheath, the possible trauma to the patient’s blood vessel during sheath advancement and dilation, and damage to the sheath caused by the dilator. This procedure requires a series of steps utilizing several different components (the introducer, the sheath, and the dilator). Additionally, it does not address the issue of reducing the push forces needed to advance the delivery system through the blood vessel. Accordingly, there remains a need for improvements to the devices, systems and methods of introducing and dilating sheaths, for example by reducing the number of components and the steps of the procedure. SUMMARY OF THE INVENTION

[0008] Aspects of the present expandable sheath and dilator system can minimize trauma to the vessel and damage to the sheath and medical device by reducing the push force required to advance the medical device through the sheath and/or blood vessel and reducing the number of components and steps of the procedure. Aspects ensure that neither the sheath nor blood vessel are damaged during efforts to advance the medical device therethrough. Furthermore, certain implementations can reduce the length of time a procedure takes, as well as reduce the risk of a longitudinal or radial vessel tear, or plaque dislodgement, because lower push force is required for sheath dilation in challenging patient anatomy.

[0009] An example of the present disclosure provides a dilator system including a shaft and a tapered distal end, wherein the tapered distal end defines a maximum diameter of the dilator shaft.

[0010] In one of its basic configurations, the present disclosure provides a dilator system including a dilator shaft including having a tapered distal end including a ridge projecting from an outer surface of the tapered distal end. This basic configuration can preferably be provided with any one or more of the features described elsewhere herein, in particular with those of the examples described hereafter. However, it should be understood that the basic configuration can preferably also be provided with any one or more of the features shown in the figures and/or described in conjunction with the figures, either in addition to or alternatively to the features of the examples described hereafter.

[0011] In some examples, the dilator shaft includes an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft.

[0012] In some examples, the dilator system includes a dilator hub coupled to the proximal end of the dilator shaft.

[0013] An example of the present disclosure provides a sheath system including: a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion. In some examples, the sheath system further includes a dilator system for expanding at least a portion of the sheath. In some examples, the dilator system includes: a dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft. In some examples, at least a portion of the sheath is optionally configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration.

[0014] An example of the present disclosure provides a method of dilating a sheath including providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is optionally configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen. In some examples, the method further includes providing a dilator shaft for expanding at least a portion of the sheath, the dilator shaft including a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter of the dilator shaft (for example,, the ridge reducing the contact area of the dilator shaft it is advanced through the sheath, thereby reducing the needed push force); an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; where a dilator hub is coupled to the proximal end of the dilator shaft. In some examples, the method further includes introducing the dilator shaft (for example, the tapered distal end of the dilator shaft and at least a portion of the elongated body portion) into the central lumen of the sheath. In some examples, the method further includes advancing the tapered distal end through a portion of the central lumen of the sheath such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration. In some examples, the method further includes removing the dilator shaft/dilator system from the sheath.

[0015] An example of the present disclosure provides a method of inserting a medical device into a blood vessel of a patient, the method including inserting a radially expandable sheath at least partially into the blood vessel of a patient, the sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is optionally configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen. In some examples, the method further includes removing an introducer from the central lumen of the sheath. In some examples, the method further includes introducing the dilator shaft into the central lumen of the sheath, the dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter of the dilator shaft; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; where a dilator hub is coupled to the proximal end of the dilator shaft. In some examples, the method further includes advancing the tapered distal end through a portion of the central lumen of the sheath such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration. In some examples, the method further includes removing the dilator shaft from the sheath; introducing a medical device into a proximal end of the central lumen of the sheath. In some examples, the method further includes advancing the medical device through the sheath; and advancing the medical device beyond a distal opening in the sheath to a treatment site within the blood vessel.

[0016] An example of the present disclosure provides a bi-directional dilator system including: a dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft. In some examples, the dilator shaft further includes a first dilating portion adjacent the first tapered end and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion. In some examples, the a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion (and/or the dilator shaft).

[0017] An example of the present disclosure provides a method of dilating a sheath including providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is optionally configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen. In some examples, the method further includes providing a dilator system for expanding at least a portion of the sheath, the dilator system including: the dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion, and the diameter of the second dilating portion is greater than the diameter of the first dilating portion. In some examples, the method further includes introducing the dilator shaft (for example, the first tapered end or the second tapered end) into the central lumen of the sheath. In some examples, the method further includes advancing the dilator shaft through a portion of the central lumen of the sheath such that at least one of the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration. In some examples, the method further includes removing the dilator shaft from the sheath. [0018] An example of the present disclosure provides a method of inserting a medical device into a blood vessel of a patient, the method including: inserting a radially expandable sheath at least partially into the blood vessel of a patient, the sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is optionally configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen. In some examples, the method further includes removing an introducer from the central lumen of the sheath. In some examples, the method further includes introducing the dilator shaft into the central lumen of the sheath, the dilator shaft including a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion, and the diameter of the second dilating portion is greater than the diameter of the first dilating portion. In some examples, the method further includes advancing the dilator shaft through a portion of the central lumen of the sheath such that at least one of the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration. In some examples, the method further includes removing the dilator shaft from the sheath. In some examples, the method further includes introducing a medical device into a proximal end of the central lumen of the sheath. In some examples, the method further includes advancing the medical device through the sheath. In some examples, the method further includes advancing the medical device beyond a distal opening in the sheath to a treatment site within the blood vessel.

[0019] Various aspects of the examples described above can be combined based on desired sheath system characteristics.

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is an elevation view of an expandable sheath along with an endovascular delivery apparatus for implanting a prosthetic implant.

[0021] FIG. 2 is an elevation view of an expandable sheath including an introducer locking hub, a sheath locking sleeve, and an introducer.

[0022] FIG. 3 is an elevation view of the expandable sheath of FIG. 2 along with an endovascular delivery apparatus for implanting a prosthetic implant.

[0023] FIG. 4 is an elevation view of an expandable sheath a sheath hub, an introducer hub, and a sheath locking sleeve of FIG. 2.

[0024] FIG. 5 is a is a cross sectional view of the sheath hub, introducer hub, and sheath locking sleeve of FIG. 2.

[0025] FIG. 6 is a cross sectional view of the introducer cap, sheath hub, introducer hub, and sheath locking sleeve of FIG. 2.

[0026] FIG. 7 A is a distal end view of the sheath locking sleeve of FIG. 2.

[0027] FIG. 7B is a first elevation view of the sheath locking sleeve of FIG. 2. [0028] FIG. 7C is a proximal end view of the sheath locking sleeve of FIG. 2. [0029] FIG. 7D is a first perspective view of the sheath locking sleeve of FIG. 2. [0030] FIG. 7E is a second elevation view of the sheath locking sleeve of FIG. 2. [0031] FIG. 7F is a second perspective view of the sheath locking sleeve of FIG. 2. [0032] FIG. 8 is a first elevation view of the introducer locking hub of FIG. 2 coupled to an introducer.

[0033] FIG. 9 is a second (rotated) elevation view of the introducer locking hub of FIG. 2 coupled to the introducer.

[0034] FIG. 10A is a distal end view of the introducer hub of FIG. 2.

[0035] FIG. 10B is a first elevation view of the introducer hub of FIG. 2.

[0036] FIG. 10C is a proximal end view of the introducer hub of FIG. 2.

[0037] FIG. 10D is a first perspective view of the introducer hub of FIG. 2.

[0038] FIG. 10E is a second elevation view of the introducer hub of FIG. 2.

[0039] FIG. 10F is a second perspective view of the introducer hub of FIG. 2.

[0040] FIG. 11 is a side elevation cross-sectional view of a portion of the expandable sheath of FIGS. 1 and 2.

[0041] FIG. 12 is a magnified view of a portion of the expandable sheath of FIGS. 1 and 2. [0042] FIG. 13 is a magnified view of a portion of the expandable sheath of FIGS. 1 and 2 with the outer layer removed for purposes of illustration.

[0043] FIG. 14 is a magnified view of a portion of the braided layer of the sheath of FIGS. 1 and 2.

[0044] FIG. 15 is a magnified view of a portion of the expandable sheath of FIGS. 1 and 2 illustrating expansion of the sheath as a prosthetic device is advanced through the sheath. [0045] FIG. 16 is a cross-sectional view of an example sheath in an unexpanded configuration.

[0046] FIG. 17 is an additional cross-sectional view of the example sheath of FIG. 16 in an unexpanded configuration.

[0047] FIG. 18 is an additional cross-sectional view of the example sheath of FIG. 16 in an expanded configuration.

[0048] FIG. 19 is a perspective view of an example dilator with a tapered distal end.

[0049] FIG. 20 is a side view of the example dilator of FIG. 19.

[0050] FIG. 21 is an end view of the distal end of the example dilator of FIG. 19.

[0051] FIG. 22 is a side view of the tapered distal end of the example dilator of FIG. 19.

[0052] FIG. 23 is a cross-sectional view of the tapered distal end of the example dilator of FIG. 19.

[0053] FIG. 24 is a cross-sectional view of an example dilator hub.

[0054] FIG. 25 is a side view of an example dilator tapered distal end.

[0055] FIG. 26 is a side view of an example dilator tapered distal end. [0056] FIG. 27 is a cross-sectional view of an example dilator tapered distal end. [0057] FIG. 28 is a side view of an expandable sheath and example dilator.

[0058] FIG. 29 is a side cross-sectional view of an expandable sheath with an example dilator disposed in the central lumen of the expandable sheath.

[0059] FIG. 30 is a side view of an example bi-directional dilator.

[0060] FIG. 31 is a side view of an example dilator with an adaptor at the proximal end.

DETAILED DESCRIPTION OF THE INVENTION

[0061] The following description of certain examples of the inventive concepts should not be used to limit the scope of the claims. Other examples, features, aspects, implementations, and advantages will become apparent to those skilled in the art from the following description. As will be realized, the device and/or methods are capable of other different and obvious aspects, all without departing from the spirit of the inventive concepts. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive.

[0062] For purposes of this description, certain aspects, advantages, and novel features of the aspects of this disclosure are described herein. The described methods, systems, and apparatus should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed aspects, alone and in various combinations and sub-combinations with one another. The disclosed methods, systems, and apparatus are not limited to any specific aspect, feature, or combination thereof, nor do the disclosed methods, systems, and apparatus require that any one or more specific advantages be present or problems be solved.

[0063] Features, integers, characteristics, compounds, chemical moieties, or groups described in conjunction with a particular aspect or example of the present disclosure are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The present disclosure is not restricted to the details of any foregoing aspects. The present disclosure extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. [0064] It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0065] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0066] "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0067] The terms “proximal” and “distal” as used herein refer to regions of a sheath, catheter, or delivery assembly. “Proximal” means that region closest to handle of the device, while “distal” means that region farthest away from the handle of the device.

[0068] “Axially” or “axial” as used herein refers to a direction along the longitudinal axis of the sheath.

[0069] Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises," means "including but not limited to," and is not intended to exclude, for example, other additives, components, integers or steps. "Exemplary" means "an example of" and is not intended to convey an indication of a preferred or ideal aspect. "Such as" is not used in a restrictive sense, but for explanatory purposes.

[0070] Example expandable introducer sheaths are disclosed, for example, in U.S. Patent No. 8,690,936, entitled “Expandable Sheath for Introducing an Endovascular Delivery Device into a Body,” U.S. Patent No. 8,790,387, entitled “Expandable Sheath for Introducing an Endovascular Delivery Device into a Body,” U.S. Patent No. 10,639,152, entitled “Expandable Sheath and Methods of Using the Same,” U.S. Patent No. 10,792,471, entitled “Expandable Sheath,” U.S. Patent No. Application No. 16/407,057, entitled “Expandable Sheath with Elastomeric Cross Sectional Portions,” U.S. Patent No. 10,327,896, entitled “Expandable Sheath with Elastomeric Cross Sectional Portions,” U.S. Patent No. 11,273,062, entitled “Expandable Sheath,” Application No. PCT/US2021/019514, entitled “Expandable sheath for introducing an endovascular delivery device in to a body,” Application No. PCT/US2021/031227, entitled “Expandable sheath for introducing an endovascular delivery device into a body,” Application No. PCT/US2021/031275, entitled “Expandable sheath for introducing an endovascular delivery device into a body,” U.S. Application No. 17/113,268, entitled “Expandable Sheath and Method of Using the Same,” Application No.

PCT/US 2021/058247, entitled “Self-Expanding, Two Component Sheath,” Application No. PCT/US2022/012785, entitled “Expandable Sheath,” U.S. Patent No. 11,051,939, entitled “Active Introducer Sheath System,” Application No. PCT/US2022/012684, entitled “Introducer with Sheath Tip Expander,” U.S. Application No. 17/078,556, entitled “Advanced Sheath Patterns,” Application No. PCT/US2021/025038, entitled “Low temperature hydrophilic adhesive for use in expandable sheath for introducing an endovascular delivery device into a body,” Application No. PCT/US2021/050006, entitled “Expandable Sheath Including Reversible Bayonet Locking Hub,” Application No. PCT/US2022/049968, entitled “Expandable Sheath Gasket to Provide Hemostasis,” U.S. Provisional Application No. 63/530,144, entitled “Introducer/Dilator with Folded Balloon,” and U.S. Provisional Application No. 63/502,907, entitled “Lead Screw Driven Sheath Dilator,” the disclosures of which are herein incorporated by reference.

[0071] The expandable introducer sheaths and related componentry described herein can be used to deliver a prosthetic device through a patient’s vasculature to a procedure site within the body. The sheath can be constructed to be radially expandable and collapsible. Disclosed examples of an expandable sheath can minimize trauma to the vessel by allowing for temporary expansion of a portion of the introducer sheath to accommodate the delivery apparatus, followed by a return to the original diameter once the device passes through. Disclosed aspects of the present expandable sheath and dilator system can be used to predilate the sheath and/or patient’s blood vessel. This can minimize trauma to the vessel and damage to the sheath by reducing the push forces required to advance the medical device and/or delivery system through the sheath, and the medical device through the blood vessel. [0072] As described herein, the dilator is provided with a tapered distal end/dilating portion provided on an elongated shaft. In some examples, the dilator includes a tapered distal end and/or a radially projecting dilating portion that acts as a dilating portion having a diameter greater than the diameter of the elongated shaft. The tapered distal end/dilating portion can be used to dilate and/or expand the sheath and/or patient’s blood vessel as the dilator is passed therethrough. In some examples, the tapered distal end/dilating portion defines the maximum outer diameter of the dilator shaft and localizes the expansion of the sheath and/or blood vessel to the maximum outer diameter portion of the tapered distal end/dilating portion. As described herein, the sheath and/or blood vessel can be dilated (pre-dilated) before the medical device/delivery system is advanced through the sheath. Pre-dilating the sheath and/or blood vessel reduces the push forces needed to advance the medical device/delivery system through the sheath and to the treatment site. Pre-dilating the blood vessel reduces the degree to which extreme constriction in patient anatomy limits or prevents sheath expansion, or otherwise makes sheath expansion more difficult.

[0073] In some implementations, the sheath can be pre-dilated prior to delivery of the medical device/delivery system. This can be done during sheath prep, prior to sheath insertion into the patient and/or with the sheath at least partially inserted into the patient. Various aspects of the sheath system structure provide for an expandable sheath and corresponding dilator that can be safely and predictably advanced through the patient’s blood vessel and expand prior to medical device/delivery system delivery. This reduces the length of time a procedure takes, as well as reduces the risk of a longitudinal or radial vessel tear, and the risk of damage to the expandable sheath.

[0074] FIG. 1 illustrates an exemplary sheath 8 in use with a representative delivery apparatus 10, for delivering an implant 12, or other type of implantable (for example, tissue heart valve), to a patient. The delivery apparatus 10 can include a steerable guide catheter 14 (also referred to as a flex catheter) and a balloon catheter 16 extending through the guide catheter 14, and a nose catheter 17 extending through the balloon catheter 16. The guide catheter 14, balloon catheter 16, and nose catheter 17 in the illustrated example are adapted to slide longitudinally relative to each other to facilitate delivery and positioning of the implant 12 at an implantation site in a patient’s body as described in detail herein. It is contemplated that the sheath 8 can be used with any type of elongated delivery apparatus used for implanting balloon-expandable prosthetic valves, self-expanding prosthetic valves, and other prosthetic devices. [0075] As described in more detail herein, in general, the sheath 8 comprises an elongate expandable tube that, in use, is inserted into a vessel (for example, transfemoral vessel, femoral artery, iliac artery) by passing through the skin of patient, such that the distal end of the sheath 8 is inserted into the vessel. Sheath 8 includes a hemostasis valve and/or sealing features at the proximal end of the sheath, for example, in the sheath hub 20, that provide hemostasis and prevents blood leakage from the patient through the sheath 8. The sheath 8, including an introducer 6, is advanced into the patient’s vasculature. Once positioned the introducer 6 is removed and the delivery apparatus 10 is inserted into/through the sheath 8, and the prosthetic device (implant 12) then be delivered and implanted within patient.

[0076] FIG. 2 illustrates a side view of the delivery apparatus 10 where the introducer 6 is received within the central lumen 9 of the sheath 8 for placement within the patient’ s blood vessel. FIG. 3 illustrates a side view of the sheath assembly with the introducer 6 removed and the balloon catheter 16 advanced within the central lumen 9 of the sheath 8. As shown in FIGS. 2 and 3, the sheath assembly includes a sheath hub 20 at a proximal end of the device and the expandable sheath 8 extending distally from the sheath hub 20.

[0077] FIG. 4 is an enlarged side view of the proximal end of the delivery apparatus 10 of FIG. 2. FIG. 5 provides a cross-sectional view of the portion of the delivery apparatus 10 illustrated in FIG. 4 and FIG. 6 provides a cross-sectional without with the elongated introducer 6 and seal assembly included within the sheath hub 20.

[0078] It is contemplated that the sheath hub 20 can optionally function as a handle for the sheath assembly/delivery apparatus 10. Sheath hub 20 also provides a housing for necessary seal assemblies and an access point for a secondary lumen (for example, fluid lumen) in fluid communication with the central lumen of the sheath hub 20. As shown in FIG. 5, the seal assembly included in the sheath hub 20 includes a proximal seal 24a, an intermediate seal 24b, and a distal seal 24c. When assembled, the introducer 6 passes through the seal assembly and extends through the distal opening of the sheath 8. The proximal seal 24a, the intermediate seal 24b, and the distal seal 24c are each formed to prevent unwanted fluid from advancing in the proximal direction through the sheath hub 20.

[0079] As illustrated in FIGS. 5 and 6, the distal end of the sheath hub 20 optionally includes threads for coupling to a threaded sheath hub cap 22. The proximal end of the sheath 8 is positioned between the sheath hub 20 and the sheath hub cap 22 such that coupling/tightening the sheath hub cap 22 to the sheath hub 20 fixes the sheath 8 to the sheath hub 20. The sheath hub cap 22 is a cylindrical cap having a cap body having a proximal end and a distal end and defining a central lumen extending longitudinally between the proximal end and the distal end. The sheath hub cap 22 has a larger diameter at its proximal end than at its distal end. [0080] FIGS. 2 and 4-6 illustrate the delivery apparatus 10 of FIG. 1 including an optional sheath locking system 18 for removably coupling the introducer 6 and sheath 8, particularly, for coupling the introducer locking hub 30 with the sheath hub 20. When the introducer locking hub 30 is coupled to the sheath hub 20, axial and rotational movement of the introducer 6 with respect to the sheath 8 is limited. That is, when engaged, the sheath locking system 18 fixes the introducer 6 with respect to the sheath 8 during insertion without requiring a physician or technician to hold the introducer 6 and the sheath 8 in place at the distal end. Example locking systems are disclosed in PCT/US2021/050006, entitled “Expandable Sheath Including Reverse Bayonet Locking Hub,” the disclosure of which is incorporated herein by reference. It is contemplated that the locking system 18 disclosed herein can also be used to couple the sheath 8/sheath hub 20 with other delivery apparatus components, catheters, dilators, etc. including the same mating features.

[0081] As illustrated in FIGS. 2 and 4-6, and described in more detail herein, the sheath locking system 18 includes a locking sleeve 28 that couples the sheath hub 20 to the introducer locking hub 30. As described in more detail herein, the sheath locking system 18 keeps the introducer 6 from separating from the sheath 8 and prevents gaps from forming that can cause patient abrasions and unintended fluid flow between the introducer 6 and the sheath 8 during insertion through the patient’s blood vessel.

[0082] As provided in FIGS. 5 and 6, the distal end of the locking sleeve 28 is received within the sheath hub 20. The sheath hub 20 includes optional receiving slots 48/openings which extend around a portion of the diameter of the sheath hub 20 and are sized and configured to accept a projection (interference diameters 66) extending radially from the locking sleeve 28. Coupling between the receiving slots 48 and the interference diameters 66 axially and rotationally fixes the locking sleeve 28 and the sheath hub 20 relative to each other.

[0083] Similarly, the introducer locking hub 30 engages the locking sleeve 28 and is moveable between a locked and unlocked position, thereby fixing the position of the introducer 6 and the sheath 8 and preventing movement therebetween. As illustrated in FIGS. 2, 5, and 6, and described in more detail herein, the locking sleeve 28 includes a guide 31 that engages a locking channel 38 provided on the introducer locking hub 30. The guide 31 moves within the locking channel 38 between an unlocked position, where the locking sleeve 28 is rotationally and axially movable with respect to the introducer locking hub 30, and a locked position (FIG. 2), where the locking sleeve 28 is axially fixed with respect to the introducer locking hub 30.

[0084] The locking sleeve 28 is illustrated, for example, in FIGS. 7A-7F. The locking sleeve 28 includes an elongated sleeve body 29 with a central lumen 56 extending longitudinally between the proximal end 58 and distal end 60 of the sleeve body 29. As provided in FIG. 6, the central lumen 56 defines a generally cylindrical inner surface 62 of the sheath locking sleeve 28. The distal end 60 of the sleeve body 29 optionally has a frustoconical outer surface 64 that tapers about the distal end 60 to help with positioning the locking sleeve 28 within the sheath hub 20 and abutting the seal assembly 24 (FIG.6). The locking sleeve 28 also optionally has a plurality of interference diameters 66 that extend radially from the outer surface of the sleeve body 29 around (all or a portion of) the circumference of the locking sleeve 28. As illustrated in FIG. 4 and 6, the distal interference diameters 66 are sized and configured to engage corresponding recesses and/or receiving slots 48 provided in the sheath hub 20 for securing the locking sleeve 28 to the sheath hub 20, and the distal interference diameter 66 seat against the proximal end of the sheath hub 20.

[0085] As provided in FIGS. 7A-7F, the locking sleeve 28 includes an optional guide 31 projecting from the outer surface 68 of the locking sleeve 28. The guide 31 engages a corresponding shaped locking channel 38 in the introducer locking hub 30, as shown, for example, in FIG. 2. The guide 31 extends radially from the outer surface 68 and at least partially around the circumference of the outer surface 68. As provided in FIG. 6, the top surface of the guide 31 does not extend beyond the outer surface of the introducer locking hub 30 when the sheath locking sleeve 28 and the introducer locking hub 30 are coupled. [0086] As illustrated in FIGS. 7D-7F, the guide 31 is a cylindrically shaped projection. However, it is contemplated that the guide 31 may have any other regular or irregular shape that would facilitate movement of the guide 31 within the locking channel 38 of the introducer locking hub 30. For example, the guide 31 may have an elongated hexagon shape. [0087] In general, the locking sleeve 28 can optionally be formed from polycarbonate, but in other aspects, the locking sleeve 28 can be formed from rigid plastic, or any other material suitable for providing a strong locking connector for an introducer 6 (metal, composite, etc.). [0088] FIGS. 8-9 illustrate the introducer 6 with the introducer locking hub 30 coupled to its proximal end. As illustrated in FIG. 2, when the introducer locking hub 30 is coupled to the sheath hub 20, the introducer 6 extends through the central lumen of the locking sleeve 28, sheath hub 20, and the sheath 8. [0089] As provided in FIGS. 8-9, the introducer 6 is formed as an elongated body with a central lumen extending therethrough. In some examples, the proximal end of the introducer 6 is received within a recessed opening 39 provided on an interior surface of the introducer locking hub 30, where the recessed opening 39 is axially aligned with the central lumen 45 of the introducer locking hub 30. The introducer 6 can be removably and/or fixedly coupled to the introducer locking hub 30 at the recessed opening 39. In an example system, the introducer 6 has a diameter corresponding to, or less than, the diameter of the recessed opening 39. In some examples, the introducer 6 is fixedly coupled to the introducer locking hub 30 at the recessed opening 39. For example, the introducer 6 is coupled to the recessed opening of the introducer locking hub 30 by at least one of a press fit, an interference fit, a snap fit, a mechanical fastener, a chemical fastener (for example, an adhesive), a weld, a thermal process, and/or any other suitable coupling process known in the art.

[0090] When assembled/coupled, the central lumen of the introducer 6 is aligned with the central lumens of the introducer locking hub 30, sheath hub 20, and the sheath 8, as illustrated in FIG. 5. This joined/continuous lumen allows for the passage of surgical equipment and/or medical devices to the treatment site (for example, a guide wire).

[0091] FIGS. 10A-10F provide multiple views of the introducer locking hub 30. As illustrated in FIGS. 10A-10F, the introducer locking hub 30 includes a hub body 32 having a proximal end 70 and a distal end 72 and defining a central lumen 45 extending therethrough. The hub body 32 has a first (middle) portion 33, a second (distal) portion 35 which extends distally from the first portion 33 and a third (proximal) portion 37 which extends proximally from the first portion 33. The first portion 33 includes the cylindrically-shaped recessed opening 39 for receiving and retaining the introducer 6 and an outer surface 43 (FIG. 6). The third (proximal) portion 37 of the introducer locking hub 30 includes the decreasing tapered portion 41 of the central lumen 45 (FIG. 6). The decreasing tapered portion 41 defining a frustoconical shape with decreasing taper/diameter from the proximal to the distal end of the sheath.

[0092] As illustrated in FIGS. 5 and 6, when coupled, the central lumen 56 of the locking sleeve 28 is aligned with the central lumen 45 of the introducer locking hub 30. In some examples, the central lumen 56 of the locking sleeve 28 is coaxial with the central lumen 45 of the introducer locking hub 30. When coupled, the proximal end of the locking sleeve 28 is received within the central lumen 45 of the introducer locking hub 30. The proximal end surface of the locking sleeve 28 is adjacent a shoulder 50 provided on an inner surface of the central lumen 45 of the introducer locking hub 30. As illustrated in FIGS. 5 and 6, the central lumen 45 of the introducer locking hub 30 includes a first portion 52 having a first diameter adjacent the proximal end of the introducer locking hub 30, and a second portion 54 having a second, larger, diameter adjacent the distal end of the introducer locking hub 30. The recessed opening 39 can be considered either a component of the first portion 52 of the central lumen 45, or a separate component of the central lumen 45 located between the (proximal) first portion 52 and the (distal) second portion 54. When the locking sleeve 28 and introducer locking hub 30 are coupled, at least a portion of the sleeve body 29 of the sheath locking sleeve 28 is received within the second portion 54 (larger portion) of the central lumen 45 of the introducer locking hub 30. The central lumen 56 of the sheath locking sleeve 28 is aligned with the central lumen 45 of the introducer locking hub 30 such that they are coaxial and form a smooth inner surface along the combined central lumens of the introducer locking hub 30 and the sheath locking sleeve 28.

[0093] As described generally above, the locking sleeve 28 couples to the introducer locking hub 30 via engagement between the guide 31 on the locking sleeve 28 and the locking channel 38 provided in the introducer locking hub 30. As provided in FIGS. 10A-10F, the introducer locking hub 30 optionally includes two locking channels 38. However, it is contemplated that the introducer locking hub 30 can include one locking channel 38 or more than two locking channels 38. The locking channel 38 can be is formed a recess or groove in a surface of the introducer locking hub 30, as a slotted opening, a clip, or as any other feature capable of receiving and securing the guide 31 projecting from the outer surface of the locking sleeve 28 with the introducer locking hub 30. Illustrated in FIG. 10B, the locking channels 38 provide an interface to secure the sheath locking sleeve 28 to the introducer locking hub 30 and ensure a fixed axial position between the introducer 6 and the sheath 8. [0094] The locking channel 38 is formed on the distal end of the introducer locking hub 30. The locking channel 38 includes an opening on the distal end surface that leads to an angled guide portion 40 that transitions to a locking portion 42. The guide portion 40 is configured to direct the guide 31 of the locking sleeve 28 in an axial and circumferential direction along the side wall of the guide portion 40 towards the locking portion 42 upon rotation of the introducer locking hub 30 and/or the sheath locking sleeve 28. The locking portion 42 is configured to securely engage the guide 31 , fixing the axial position of the introducer locking hub 30 with respect to the sheath locking sleeve 28. As illustrated in FIG. 10B, the guide portion 40 of the locking channel 38 extends from the distal end of the introducer locking hub 30 axially towards the proximal end of the introducer locking hub 30 and circumferentially around the introducer locking hub 30. For example, the guide portion 40 of the locking channel 38 can be described as extending helically around/along a length of the introducer locking hub 30 or on an angle from the distal end of the introducer locking hub 30.

[0095] As illustrated in FIGS. 10A and 10D, the locking portion 42 of the locking channel 38 extends at an angle from the end of the guide portion 40. As provided in FIG. 10B, the angle between the centerline of the guide portion 40 and the centerline of the locking portion 42 is greater than 90-degrees. In another example, the angle between the centerline of the guide portion 40 and the centerline of the locking portion 42 is about 120-degrees. In an example system, the locking portion 42 extends around a portion of the circumference of the introducer locking hub 30. The locking portion 42 can extend parallel to the distal end of the introducer locking hub 30. In an example system, the length of the guide portion 40 (measured along its centerline) is greater than a length of the locking portion 42 (measured along its centerline). In another example, the length of the guide portion 40 equals or is less than the length of the locking portion 42.

[0096] The locking portion 42 can include a catch 44 for securing the guide 31 within the locking portion 42 of the locking channel 38 and forming a partial barrier for the guide 31 within the locking portion 42. As illustrated in FIG. 10B, the catch 44 includes a projection that extends from a side wall 74 of the locking portion 42 and releasably secures the guide 31 within the locking channel 38. The catch 44 extends from the side wall 74 of the locking portion 42 in a proximal direction towards the center line of the locking portion 42 and has a height sufficient to retain the guide 31 between the catch 44 and the end of the locking portion 42.

[0097] The distal end 72 of the introducer locking hub 30 can optionally include features for biasing the guide 31 towards the locking channel 38. For example, the distal end of the introducer locking hub 30 can include a tapered surface angled toward an opening of the locking channel 38. As illustrated in FIG. 10B, the distal end 72 of the introducer locking hub 30 includes a first tapered surface 76 (angled towards a leading edge of the opening of the locking channel 38 and a second tapered surface 78 angled towards the trailing edge of the opening of the locking channel 38.

[0098] In use, engagement between the guide 31 and the guide portion 40 of the locking channel 38 is configured to bias the locking sleeve 28 in a proximal axial direction toward the proximal end 70 of the introducer locking hub 30 (towards a locked position) when the sheath locking sleeve 28 is rotated in a first axial direction. In this direction the guide 31 advances toward the locking portion 42 of the locking channel 38 into the locked position. Alternatively, engagement between the guide 31 and the locking portion 42 of the locking channel 38 is configured to bias the locking sleeve 28 in a distal axial direction toward the distal end of the introducer locking hub 30 (towards an unlocked position) when the sheath locking sleeve 28 is rotated in a second (opposite) axial direction. In the second direction, the guide 31 advances away from the locking portion 42 of the locking channel 38, to the unlocked position. When the guide 31 is in the locked position and retained with by locking portion 42 by catch 44, rotation in the second direction causes the guide 31 to bias against the catch 44 overcoming the oppositional forces of the catch 44, and moving the guide 31 from the locked to the unlocked position.

[0099] As provided in FIG. 10B, the introducer locking hub body 32 can optionally include a two recessed gripping surfaces 34 on opposite sides of the longitudinal axis of the introducer locking hub 30. When the introducer locking hub 30 is viewed from the side, the gripping surfaces 34 define a dog-bone/barbell shape to the hub body 32, i.e., a shape having a smaller diameter/width center portion and larger diameter/width end portions.

[0100] In general, the introducer locking hub 30 can optionally be formed from polycarbonate, but in other aspects the introducer locking hub 30 can be formed from rigid plastic, or any other material suitable for providing a locking mechanism for an introducer 6 (metal, composite, etc.).

[0101] Example layered structures for the expandable sheath 8 are described here. Referring to FIG. 3, the expandable sheath 8 is coupled at its proximal end to the sheath hub 20. As described herein, the introducer device/sheath assembly includes an expandable sheath 8 extending distally from the sheath hub 20. The expandable sheath 8 has a central lumen 9 to guide passage of the delivery apparatus 10 for the medical device/prosthetic heart valve. In some examples, the introducer device/sheath assembly need not include the sheath hub 20. For example, the sheath 8 can be an integral part of another component of the sheath assembly, such as the guide catheter. As described herein, the sheath 8 can have a natural, unexpanded outer diameter that will expand locally upon passage of the medical device.

[0102] In some examples, the expandable sheath 8 may optionally include a plurality of coaxial layers extending along at least a portion of the length of the sheath 8. The structure of the coaxial layers is described in more detail with respect to FIGS. 11-18. Example expandable sheaths including coaxial layers are described, for example, in U.S. Patent Application No. 16/378,417, entitled “Expandable Sheath,” and U.S. Patent Application No. 17/716,882, entitled “Expandable Sheath,” the disclosures of which are herein incorporated by reference. [0103] Various aspects of the coaxial layered structure of the sheath 8 are described herein. For example, in reference to the example sheath 8 illustrated in FIGS. 11-15, the expandable sheath 8 can include a number of layers including an inner layer 102 (also referred to as an inner layer), a second layer 104 disposed around and radially outward of the inner layer 102, a third layer 106 disposed around and radially outward of the second layer 104, and a fourth outer layer 108 (also referred to as an outer layer) disposed around and radially outward of the third layer 106. In the illustrated configuration, the inner layer 102 can define the lumen 1 12 of the sheath extending along a central axis 1 14 through which the delivery apparatus travels into the patient’s vessel in order to deliver, remove, repair, and/or replace a prosthetic device, moving in a direction along the longitudinal axis of the sheath 8.

[0104] Referring to FIG. 11, when the sheath 8 is in an unexpanded state, various layers of the sheath, for example, the inner layer 102 and/or the outer layer 108, can optionally form longitudinally-extending folds or creases such that the surface of the sheath comprises a plurality of ridges 126 (also referred to herein as “folds”). The ridges 126 can be circumferentially spaced apart from each other by longitudinally-extending valleys 128. When the sheath expands beyond its natural diameter (DI) shown in FIG. 12, the ridges 126 and the valleys 128 can level out or be taken up as the surface radially expands and the circumference increases, as further described below. When the sheath 8 collapses back to its natural diameter, the ridges 126 and valleys 128 can reform.

[0105] In some examples, the inner layer 102 and/or the outer layer 108 can comprise a relatively thin layer of polymeric material. In some examples, the inner layer 102 and/or the outer layer 108 can comprise a lubricious, low-friction, and/or relatively non-elastic material. In some examples, the inner layer 102 and/or the outer layer 108 can comprise a polymeric material having a modulus of elasticity of 400 MPa or greater. Exemplary materials can include ultra-high-molecular-weight polyethylene (UHMWPE) (for example, Dyneema®), high-molecular- weight polyethylene (HMWPE), or polyether ether ketone (PEEK). With regard to the inner layer 102 in particular, such low coefficient of friction materials can facilitate passage of the prosthetic device through the lumen 112. Other suitable materials for the inner and outer layers can include polyimide, polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), ethylene tetrafluoroethylene (ETFE), nylon, polyethylene, polyamide, polyether block amide (for example, Pebax), and/or combinations of any of the above. Some aspects the sheath 8 can include a lubricious liner on the inner surface of the inner layer 102. Examples of suitable lubricious liners include materials that can further reduce the coefficient of friction of the inner layer 102, such as PTFE, polyethylene, polyvinylidene fluoride, and combinations thereof. Suitable materials for a lubricious liner also include other materials desirably having a coefficient of friction of 0.1 or less.

[0106] Additionally, some examples of the sheath 8 can include an optional exterior hydrophilic coating on the outer surface of the outer layer 108. Such a hydrophilic coating can facilitate insertion of the sheath 8 into a patient’s blood vessel, reducing potential damage. Examples of suitable hydrophilic coatings include the Harmony™ Advanced Lubricity Coatings and other Advanced Hydrophilic Coatings available from SurModics, Inc., Eden Prairie, MN. DSM medical coatings (available from Koninklijke DSM N.V., Heerlen, the Netherlands), as well as other hydrophilic coatings (for example, PTFE, polyethylene, polyvinylidene fluoride), are also suitable for use with the sheath 8. Such hydrophilic coatings may also be optionally included on the inner surface of the inner layer 102 to reduce friction between the sheath and the delivery system, thereby facilitating use and improving safety. In some aspects, a hydrophobic coating, such as Perylene, may be used on the outer surface of the outer layer 108 or the inner surface of the inner layer 102 in order to reduce friction.

[0107] In some aspects, the second layer 104 can be a braided layer. FIGS. 13 and 14 illustrate the sheath 8 with the outer layer 108 removed to expose the elastic third layer 106. With reference to FIGS. 13 and 14, the braided second layer 104 can comprise a plurality of members or filaments 110 (for example, metallic or synthetic wires or fibers) braided together. The braided second layer 104 can have any desired number of filaments 110, which can be oriented and braided together along any suitable number of axes. For example, with reference to FIG. 14, the filaments 110 can include a first set of filaments 110A oriented parallel to a first axis A, and a second set of filaments HOB oriented parallel to a second axis B. The filaments 110A and HOB can be braided together in a biaxial braid such that filaments 110A oriented along axis A form an angle 0 with the filaments HOB oriented along axis B. In other aspects, the filaments 110 can also be oriented along three axes and braided in a triaxial braid, or oriented along any number of axes and braided in any suitable braid pattern. The braided second layer 104 can extend along substantially the entire length L of the sheath 8, or alternatively, can extend only along a portion of the length of the sheath. In some examples, the filaments 110 can be wires made from metal (for example, Nitinol, stainless steel, etc.), or any of various polymers or polymer composite materials, such as carbon fiber. In some examples, the filaments 110 can be round, have a flat cross-section or have other suitable geometries and sizes. If braided wire is used, the braid density can be varied. In other examples, the second layer 104 can be laser cut from a tube, or laser-cut, stamped, punched, etc., from sheet stock and rolled into a tubular configuration. The second layer 104 can also be woven or knitted, as desired.

[0108] The third layer 106 can be a resilient, elastic layer (also referred to as an elastic material layer). In some examples, the elastic third layer 106 can be configured to apply radially inward force to the underlying first layer (inner layer 102) and second layer 104 in a radial direction (for example, toward the central axis 114 of the sheath 8) when the sheath 8 expands beyond its natural diameter by passage of the delivery apparatus 10 through the sheath 8. Stated differently, the elastic third layer 106 can be configured to apply encircling/radially inward pressure to the layers of the sheath 8 beneath the elastic third layer 106 to counteract expansion of the sheath 8. The radially inwardly directed force is sufficient to cause the sheath 8 to collapse radially back to its unexpanded state after the delivery apparatus 10 is passed through the sheath 8.

[0109] In some examples, as illustrated in FIGS. 11-15, the elastic third layer 106 can optionally comprise one or more members configured as strands, ribbons, or bands 116 helically wrapped around the braided second layer 104. For example, in the illustrated aspect the elastic third layer 106 comprises two elastic bands 116A and 116B wrapped around the braided second layer 104 with opposite helicity, although the elastic layer may comprise any number of bands depending upon the desired characteristics. The elastic bands 116A and 116B can be made from, for example, any of a variety of natural or synthetic elastomers, including silicone rubber, natural rubber, any of various thermoplastic elastomers, polyurethanes such as polyurethane siloxane copolymers, urethane, plasticized polyvinyl chloride (PVC), styrenic block copolymers, polyolefin elastomers, etc. In some examples, the elastic third layer 106 can comprise an elastomeric material having a modulus of elasticity of 200 MPa or less. In some examples, the elastic third layer 106 can comprise a material exhibiting an elongation to break of 200% or greater, or an elongation to break of 400% or greater. The elastic third layer 106 can also take other forms, such as a tubular layer comprising an elastomeric material, a mesh, a shrinkable polymer layer such as a heat-shrink tubing layer, etc. In lieu of, or in addition to, the elastic third layer 106, the sheath 8 may also include an elastomeric or heat-shrink tubing layer around the outer layer 108. Examples of such elastomeric layers are disclosed in U.S. Publication No. 2014/0379067, U.S. Publication No. 2016/0296730, and U.S. Publication No. 2018/0008407, which are incorporated herein by reference. In other aspects, the elastic third layer 106 can also be radially outward of the polymeric outer layer 108. [0110] In some aspects, one or both of the inner layer 102 and/or the outer layer 108 can be configured to resist axial elongation of the sheath 8 when the sheath expands. More particularly, one or both of the inner layer 102 and/or the outer layer 108 can resist stretching against longitudinal forces caused by friction between a prosthetic device and the inner surface of the sheath 8 such that the length L remains substantially constant as the sheath expands and contracts. As used herein with reference to the length L of the sheath, the term “substantially constant” means that the length L of the sheath increases by not more than 1%, by not more than 5%, by not more than 10%, by not more than 15%, or by not more than 20%. Meanwhile, with reference to FIG. 14, the filaments 110A and HOB of the braided second layer 104 can be allowed to move angularly relative to each other such that the angle 0 changes as the sheath expands and contracts. This, in combination with the longitudinal folds/ridges 126 in the inner layer and outer layer 108, can allow the lumen 112 of the sheath to expand as a prosthetic device is advanced through it.

[0111] In some examples, the inner layer 102 and the outer layer 108 can be heat-bonded during the manufacturing process such that the braided second layer 104 and the elastic third layer 106 are encapsulated between the inner layer 102 and outer layer 108. More specifically, in some aspects the inner layer 102 and the outer layer 108 can be adhered to each other through the spaces between the filaments 110 of the braided second layer 104 and/or the spaces between the elastic bands 116. The inner layer 102 and outer layer 108 can also be bonded or adhered together at the proximal and/or distal ends of the sheath 8. In some aspects, the inner layer 102 and outer layer 108 are not adhered to the filaments 110. This can allow the filaments 110 to move angularly relative to each other, and relative to the inner layer 102 and outer layer 108, allowing the diameter of the braided second layer 104, and thereby the diameter of the sheath 8, to increase or decrease. As the angle 6 between the filaments 110A and HOB changes, the length of the braided second layer 104 can also change. For example, as the angle 0 increases, the braided second layer 104 can foreshorten, and as the angle 0 decreases, the braided second layer 104 can lengthen to the extent permitted by the areas where the inner layer 102 and outer layer 108 are bonded. However, because the braided second layer 104 is not adhered to the inner layer 102 and outer layer 108, the change in length of the braided layer that accompanies a change in the angle 0 between the filaments 110A and HOB does not result in a significant change in the length L of the sheath.

[0112] FIG. 15 illustrates radial expansion of the sheath 8 as a prosthetic device (for example, implant 12) and/or dilator is passed through the sheath 8 in the direction of arrow 132 (for example, distally). As the prosthetic device (implant 12) and/or dilator is advanced through the sheath 8, the sheath can resiliency expand to a second diameter (D2) that corresponds to a size or diameter of the prosthetic device or dilator. As the prosthetic device (implant 12)/dilator is advanced through the sheath 8, the prosthetic device can apply longitudinal force to the sheath in the direction of motion by virtue of the frictional contact between the prosthetic device/dilator and the inner surface of the sheath 8. However, as noted above, the inner layer 102 and/or the outer layer 108 can be optionally configured to resist axial elongation such that the length L of the sheath remains constant, or substantially constant. This can reduce or prevent the braided layer second 104 from lengthening, and thereby constricting the lumen 112.

[0113] Meanwhile, as provided in FIGS. 14 and 15, the angle 0 between the filaments 110A and 110B can increase as the sheath expands to the second diameter (D2) to accommodate the prosthetic valve/dilator. This can cause the braided second layer 104 to foreshorten. However, because the filaments 110 are not engaged or adhered to the inner layer 102 or outer layer 108, the shortening of the braided second layer 104 attendant to an increase in the angle 0 does not affect the overall length L of the sheath. Moreover, because of the longitudinally-extending folds/ridges 126 formed in the inner layer 102 and outer layer 108, the inner layer 102 and outer layer 108 can expand to the second diameter (D2) without rupturing, in spite of being relatively thin and relatively non-elastic. In this manner, the sheath 8 can resiliently expand from its natural diameter (DI) to a second diameter (D2) that is larger than the initial diameter (DI) as a prosthetic device and/or dilator is advanced through the sheath 8, without lengthening, and without constricting. Thus, the force required to push the prosthetic implant through the sheath 8 is significantly reduced.

[0114] Additionally, because of the radial force applied by the elastic third layer 106, the radial expansion of the sheath 8 can be localized to the specific portion of the sheath 8 occupied by the prosthetic device and/or dilator. For example, with reference to FIG. 15, as the prosthetic device (implant 12) and/or dilator moves distally through the sheath 8, the portion of the sheath 8 immediately proximal to the prosthetic device (for example, implant 12) and/or dilator can radially collapse back to the initial diameter (DI) under the influence of the elastic third layer 106. The inner layer and outer layer 108 can also buckle as the circumference of the sheath is reduced, causing the ridges 126 and the valleys 128 to reform. This can reduce the size of the sheath 8 required to introduce a prosthetic device and/or dilator of a given size. Additionally, the temporary, localized nature of the expansion can reduce trauma to the blood vessel into which the sheath 8 is inserted, along with the surrounding tissue, because only the portion of the sheath 8 occupied by the prosthetic device and/or dilator expands beyond the sheath’ s natural unexpanded diameter and the sheath 8 collapses back to the initial diameter once the device and/or dilator has passed. This limits the amount of tissue that must be stretched in order to introduce the prosthetic device, and the amount of time for which a given portion of the vessel must be dilated.

[0115] FIGS. 16-18 provide cross-section views of another example layered structure of the expandable sheath 8 of FIG. 1. Similar reference numbers are used to describe like elements. It’s understood that the variations (for example, materials and alternate configurations) described above with reference to FIGS. 11-15 can also apply to the example shown in FIGS. 16-18. Furthermore, the variations described below with reference to FIGS. 16-18 can also be applied to the sheath described in FIGS. 11-15.

[0116] Similar to various aspects of the sheath 8 described above in reference to FIGS. I lls, the sheath 8 of FIGS. 16-18 includes a plurality of layers. For example, the sheath 8 illustrated in FIGS. 16-18, also includes an inner layer 202 and an outer layer 204 disposed around the inner layer 202. The inner layer 202 can define a central lumen 212 through which the delivery apparatus travels into the patient’s vessel in order to deliver, remove, repair, and/or replace a prosthetic device, moving in a direction along the longitudinal axis X. Similar to the sheath 8 illustrated in FIGS. 11-15, as the prosthetic device and/or dilator pass through the sheath 8, the sheath 8 locally expands from a first, resting/unexpanded diameter to a second, expanded diameter to accommodate the prosthetic device. After the prosthetic device/dilator passes through a particular location of the sheath 8, each successive expanded portion or segment of the sheath 8 at least partially returns to the smaller, resting/unexpanded diameter. In this manner, the sheath 8 can be considered self-expanding, in that it does not require use of a balloon, dilator, and/or obturator to expand.

[0117] Similar to the examples herein, the inner and outer layers 202, 204 can comprise any suitable materials. Suitable materials for the inner layer 202 include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), nylon, polyethylene, polyether block amide (for example, Pebax), and/or combinations thereof. In one specific implementation the inner layer 202 can optionally comprise a lubricious, low-friction, or hydrophilic material, such as PTFE. Such low coefficient of friction materials can facilitate passage of the prosthetic device through the lumen defined by the inner layer 202. In some examples, the inner layer 202 can have a coefficient of friction of less than about 0.1. Some examples of the sheath 8 can include an optional lubricious liner on the inner surface of the inner layer 202. Examples of suitable lubricious liners include materials that can further reduce the coefficient of friction of the inner layer 202, such as PTFE, polyethylene, poly vinylidene fluoride, and combinations thereof. Suitable materials for a lubricious liner also include other materials desirably having a coefficient of friction of about 0. 1 or less.

[0118] Suitable materials for the outer layer 204 include nylon, polyethylene, Pebax, HDPE, polyurethanes (for example, Tecoflex), and other medical grade materials. In one implementation, the outer layer 204 can comprise high density polyethylene (HDPE) and Tecoflex (or other polyurethane material) extruded as a composite. In some implementations, the Tecoflex can optionally act as an adhesive between the inner layer 202 and the outer layer 204 and may only be present along a portion of the inner surface of the outer layer 204. Other suitable materials for the inner and outer layers are also disclosed in U.S. Patent Nos.

8,690,936 and 8,790,387, which are incorporated herein by reference.

[0119] Additionally, some examples of the sheath 8 include an optionally exterior hydrophilic coating on the outer surface of the outer layer 204. Such a hydrophilic coating can facilitate insertion of the sheath 100 into a patient’s vessel. Examples of suitable hydrophilic coatings include the Harmony™ Advanced Lubricity Coatings and other Advanced Hydrophilic Coatings available from SurModics, Inc., Eden Prairie, MN. DSM medical coatings (available from Koninklijke DSM N.V., Heerlen, the Netherlands), as well as other hydrophilic coatings (for example, PTFE, polyethylene, poly vinylidene fluoride), are also suitable for use with the sheath 100.

[0120] FIGS. 16-18 show cross-sectional views of the example sheath 8 taken at different points along the sheath 8. FIG. 16 shows a cross-section of the sheath 8 near the proximal end of the sheath 8 taken along section line A-A, in FIG. 2. At this location, the sheath 8 includes the inner layer 202, outer layer 204, elastic outer layer 250/outer jacket, and the strain relief layer 26. At this location, near the proximal end of the sheath 8, the inner layer 202 and outer layer 204 are substantially tubular. Here the inner layer 202 and outer layer 204 can be formed without any slits or folded portions in the layers. By contrast, as described herein, the inner layer 202 and outer layers 204 at different locations along the sheath 8 can have a different configuration, for example, at the location of section line B-B, FIG. 2.

[0121] FIG. 17 illustrates a cross-sectional view of the example sheath taken along section lines B-B in FIG. 2, when the sheath 8 is in an unexpanded configuration. As shown in FIG. 17, the inner layer 202 can be arranged to form a substantially cylindrical central lumen 212 therethrough. Inner layer 202 can optionally include one or more folded portions 218. In the example shown in FIG. 17, inner layer 202 is arranged to have one folded portion 218 that can be positioned on either side of the inner layer 202. Inner layer 202 can be continuous, with no breaks, slits, or perforations in inner layer 202. Outer layer 204 can optionally be arranged in an overlapping fashion such that an overlapping portion 220 overlaps at least a part of the folded portion 218 of the inner layer 202. As shown in FIG. 17, the overlapping portion 220 also overlaps an underlying portion 222 of the outer layer 204. The underlying portion 222 can be positioned to underlie both the overlapping portion 220 of the outer layer 204, as well as the folded portion 218 of the inner layer 202. Thus, the outer layer 204 can be discontinuous, in that it includes a slit or a cut in order to form the overlapping portion 220 and underlying portion 222. In other words, a first edge 224 of the outer layer 204 is spaced apart from a second edge 225 of the outer layer 204 so as not to form a continuous layer. [0122] As shown in FIGS. 17 and 18, the elastic outer layer 250 can be a continuous tubular layer, without slits or other discontinuities. The elastic outer layer 250 extends between strain relief layer 26 and the outer surface of the outer layer 204. In some examples, the elastic outer layer 250 extends over the outer surface of the strain relief layer 26 and the outer surface of the outer layer 204. In some examples, the elastic outer layer 250 extends both over the strain relief layer 26 and/or between the outer layer of the sheath 8 and the strain relief layer 26. The elastic outer layer 250 can optionally comprise any pliable, elastic material(s) that expands and contracts, preferably with a high expansion ratio. Preferably, the materials used can include low durometer polymers with high elasticity, such as Pebax, polyurethane, silicone, and/or polyisoprene. Materials for the elastic outer layer 250 can be selected such that it does not impede expansion of the inner and outer layers of the sheath 8. The elastic outer layer 250 can be configured to stretch and expand as the sheath expands, as shown in the expanded configuration in FIG. 18.

[0123] As shown in FIG. 17, the sheath 8 can also optionally include a thin layer of bonding or adhesive material 228 positioned between the inner layer 202 and outer layer 204. In one example, the adhesive material 228 can comprise a polyurethane material such as Tecoflex. The adhesive material 228 can be positioned on an inner surface 230 of at least a portion of the outer layer 204 so as to provide adhesion between selected portions of the inner layer 202 and outer layer 204. For example, the outer layer 204 may only include the adhesive material 228 around the portion of the inner surface 230 that faces the lumen-forming portion of the inner layer 202. In other words, the adhesive material 228 can be positioned so that it does not contact the folded portion 218 of the inner layer 202. In some examples, the adhesive material 228 can be positioned in different configurations as desired for the particular application. For example, as shown in FIG. 17, the adhesive material 228 can be positioned along the entire inner surface 230 of the outer layer 204. In some examples, the adhesive material 228 can be applied to the outer surface of the inner layer 202 instead of the inner surface of the outer layer 204. The adhesive material 228 can be applied to all or selected portions on the inner layer 202; for example, the adhesive material 228 can be formed only on the portion of the inner layer 202 that faces the lumen-forming portion of the outer layer 204 and not on the folded portion 218. The configuration of FIG. 17 allows for radial expansion of the sheath 8 as an outwardly directed radial force is applied from within (for example, by passing a medical device such as a prosthetic heart valve and/or a dilator through the central lumen 212). As radial force is applied, the folded portion 218 can at least partially separate, straighten, and/or unfold, and/or the overlapping portion 220 and the underlying portion 222 of the outer layer 204 can slide circumferentially with respect to one another, thereby allowing the diameter of central lumen 212 to enlarge.

[0124] In this manner, the sheath 8 is configured to expand from a resting/unexpanded configuration (FIG. 17) to an expanded configuration shown in FIG. 18. FIG. 18 shows a cross-sectional view of the example sheath 8 taken along section line B-B in FIG. 2, when the sheath 8 is in an expanded configuration. In the expanded configuration, a gap 232 can form between the longitudinal edges of the overlapping portion 220 and the underlying portion 222 of the outer layer 204. As the sheath 8 expands at a particular location, the overlapping portion 220 of the outer layer 204 can move circumferentially with respect to the underlying portion 222 as the folded portion 218 of the inner layer 202 unfolds. This movement can optionally be facilitated by the use of a low-friction material for inner layer 202, such as PTFE. Further, the folded portion 218 can at least partially separate and/or unfold to accommodate a medical device having a diameter larger than that of central lumen 212 in the resting/unexpanded configuration. As shown in FIG. 18, in some examples, the folded portion of the inner layer 202 can completely unfold, so that the inner layer 202 forms a cylindrical tube at the location of the expanded configuration.

[0125] Similar to the layered structure described above with reference to FIGS. 11-15, the structure illustrated in FIGS. 16-18 is configured to locally expand at a particular location corresponding to the location of the medical device and/or dilator along the length of the central lumen 212, and then locally contracts once the medical device and/or dilator has passed that particular location. Thus, a bulge may be visible, traveling longitudinally along the length of the sheath 8 as a medical device and/or dilator is introduced through the sheath 8, representing continuous local expansion and contraction as the device travels the length of the sheath 8. Each segment of the sheath 8 will locally contract after removal of any radial outward force such that the sheath 8 at least partially returns to the original resting/unexpanded diameter of central lumen 212. Similar to the example sheath described herein, an elastic outer layer 250 can (optionally) be provided along the sheath 8, urging the inner and outer layers 202, 204 back to the unexpanded configuration.

[0126] The inner layer 202 and outer layer 204 of sheath 8 can be configured having the folded portion 218 as shown in FIG. 17 along at least a portion of the length of the sheath 8. In some examples, the inner layer 202 and outer layer 204 can be configured as shown in FIG. 17 (including the folded portion 218) along the length extending from the soft tip portion to a location at the proximal end of the sheath 8, adjacent and/or under the distal end of the strain relief layer 26. In this matter, the sheath 8 is expandable and contractable only along a portion of the length of the sheath 8 typically corresponding to the section of the sheath 8 inserted into the narrowest section of the patient’s vasculature.

[0127] As illustrated in FIGS. 2 and 5, the sheath 8 includes an optional strain relief layer 26. The strain relief layer 26/tube is provided adjacent the proximal end of the sheath 8 extends along/over the outer surface of the sheath 8. In some examples, the strain relief layer 26 is provided over and/or bonded to the outer layer 108, 204 of the sheath 8. The strain relief layer 26 forms a smooth transition between the sheath hub 20 and the sheath 8 and facilitates mating of the sheath 8 with the sheath hub 20. The strain relief layer 26 also provides a region of higher durometer or stiffness that restricts expansion of the underlying sheath layers. This helps to resist expansion of the sheath 8/strain relief layer 26 when the medical device and/or dilator is passed there through. This also helps to ensure hemostasis between the portions of the sheath 8 inside the patient and the sheath hub (external to the patient). Additionally, the strain relief layer 26 can be sized and configured to form a seal with the patient’s artery such that when the sheath 8 is fully inserted into the patient, a portion of the strain relief layer 26 extends through and seals against the arteriotomy site. Because radial expansion is limited along the strain relief layer 26, higher push forces are necessary to advance the medical device (implant 12) through the central lumen 9 of the sheath 8 along the strain relief layer 26.

[0128] As described herein, the present expandable sheath 8 and dilator system 300 can minimize trauma to the vessel and damage to the sheath 8 by reducing the push force required to advance the delivery system 10/prosthetic device (implant 12) through the sheath 8 and/or blood vessel. As described herein, aspects of the present dilator system 300 can minimize trauma to the vessel by pre-dilating the blood vessel, allowing for temporary expansion of a portion of the blood vessel, followed by a return to the original diameter once the dilating portion of the dilator system 300 has passed through the blood vessel. This pre-dilation introduces an initial elasticity to the vessel while also limiting the amount of the blood vessel that is stretched at a given time and the amount of time for which a given portion of the blood vessel must be dilated because expansion caused by the dilator system 300 is limited/localized to the dilating portion of the dilator system 300. Pre-dilating the blood vessel can also help to reduce the degree to which extreme constriction in patient anatomy (e.g., narrowed blood vessel caused by disease, medicines, or psychological conditions) limits or prevents sheath 8 expansion, or otherwise makes sheath 8 expansion or placement more difficult.

[0129] Similarly, the present dilator system 300 can optionally be used to pre-dilate the sheath 8, allowing for temporary expansion of a portion of the sheath 8 to accommodate the delivery system 10, followed by a return to the original diameter once the dilating portion of the dilator system 300 has passed through. It has been found that pre-dilating the sheath 8, or a portion thereof, can help to reduce push forces required to insert the medical device/delivery system through the central lumen 9 of the sheath 8. Pre-dilating the sheath 8 releases and/or loosens any bonding or adhesion of the sheath 8 layers that occurs during the manufacturing process, including, for example, bonding between the inner layer 202 and outer layer 204, bonding between the folded portion 218 and outer layer 204, bonding between the inner/outer layers and the strain relief layer 26. Pre-dilating the sheath 8 can also break or separate any intentional weakened portion formed in the various sheath layers (for example, a weakened portion formed in the folded portion 218 of the inner layer 202, allowing the folded portion 218 to separate/form a gap or opening when expanded). With the sheath 8 layers able to move freely with respect to the other, the medical device/delivery system 10 is pushed through the sheath 8 lumen at a much lower force.

[0130] FIGS. 19 and 20 provide side and perspective views of an example dilator system 300 according to the present disclosure. FIG. 21 provides a distal end view of the dilator system 300 and FIG. 22 provides an enlarged side view of the distal end of the example dilator system 300. The dilator system 300 includes an elongated dilator shaft 302 with a tapered distal end 304 adjacent the distal end 312 of the dilator system 300. In some examples, the tapered distal end 304 provides the dilating portion of the dilator shaft 302. For example, the tapered distal end 304 of the dilator shaft 302/tapered distal end 304 optionally defines the maximum outer diameter (Dmax) of the dilator shaft 302 (FIG. 22). In other examples, the elongated body portion 330 of the dilator shaft 302 defines the dilating portion of the dilator shaft 302, where the dilator shaft 302 defines the maximum outer diameter (Dmax) of the dilator shaft 302. [0131] As illustrated in FIGS. 19-23, in some examples, the tapered distal end 304 optionally includes a ridge or a plurality of ridges 306 projecting radially from the outer surface 308 of the tapered distal end 304. The ridge 306 reduces the contact area between the dilator system 300 and the sheath 8 when the dilator system 300 moves through the sheath 8, thereby reducing friction and the push force necessary to advance and/or withdraw the dilator system 300. In some examples, the ridges 306 can define a maximum outer diameter (Dmax) of the dilator shaft 302. Similarly, the ridges 306 can define a maximum outer diameter (Dmax) of the tapered distal end 304. In some examples, as shown in FIGS. 21 -22, the ridges 306 define the maximum outer diameter (Dmax) of both the dilator shaft 302 and tapered distal end 304. In some examples, the maximum outer diameter of the dilator shaft 302 at the apex 320 ranges from 16 Fr to 30 Fr, preferably 21 Fr. In some examples, the outer diameter/perimeter defined around the apex 320 can have a hexagonal shape.

[0132] As shown in FIGS. 19-22, the dilator system 300 can, in some examples, include a plurality of ridges 306 spaced around a circumference of the tapered distal end 304. In some examples, the dilator shaft 302 optionally includes from one to ten ridges 306. In some examples, the dilator shaft 302 includes from four to six ridges 306. In the illustrated example in FIGS. 19-22, the dilator shaft 302 includes preferably six ridges 306. The ridges 306 can be symmetrically or asymmetrically spaced around the circumference of the tapered distal end 304. As illustrated in FIG. 21, the ridges 306 have a curved and/or semi-circular shape in profile. It is contemplated that the ridges 306 can have any regular or irregular shaped profile. [0133] Spacing the ridges 306 around the circumference of the tapered distal end 304 allows for corresponding openings, referred to as valleys 318, to be formed between the ridges 306. The valleys 318 can optionally form a fluid path between the adjacent ridges 306. The fluid path formed by the valleys 318 helps to minimize trauma to the vessel by reducing back pressure during dilator system 300 retraction/retrieval by allowing the flow of blood/fluid from behind the tapered distal end 304 to the distal opening of the sheath 8. That is, when the dilator system 300 is received within the central lumen 9 of the sheath 8 as illustrated in FIG. 29, the valleys 318 allow fluid communication between the proximal portion 9a of the central lumen 9 (the portion between the tapered distal end 304 and the proximal end of the sheath 8) and the distal portion 9b of the central lumen 9 (the portion between the tapered distal end 304 and the distal end of the sheath 8). As a result, when the dilator system 300 is withdrawn within the sheath 8 (moved toward the proximal end) the fluid pathway formed by the valleys 318 reduces back pressure by allowing fluid within the central lumen 9 to flow from the proximal portion 9a of the central lumen 9, along the tapered distal end 304, through the distal portion 9b of the central lumen 9, and through the distal opening of the sheath 8. Like reducing push forces, reducing the back pressure helps to reduce the risk of trauma to the blood vessel and/or damage to the sheath 8 by reducing the amount of force needed for dilator system 300 retraction/retrieval.

[0134] In some examples, as shown in FIG. 22, the ridges 306 optionally include a leading tapered surface 314 and a trailing tapered surface 316. The leading tapered surface 314 is located adjacent the distal end 312 of the dilator shaft 302 and includes an increasing taper in the proximal direction/toward the proximal end 310 of the dilator shaft 302. The trailing tapered surface 316 extends between the leading tapered surface 314 and the proximal end 310 of the dilator shaft 302. The trailing tapered surface 316 has a decreasing taper in the distal direction/toward the distal end 312 of the dilator shaft 302. In some examples, the trailing tapered surface 316 prevents a “hard step’Vinterference when withdrawing the dilator shaft 302 through the seals in the sheath hub 20.

[0135] As illustrated in FIGS. 21-22, the leading tapered surface 314 and the trailing tapered surface 316 meet at an apex 320 of the ridge 306. The apex 320 defines the maximum outer diameter (Dmax) of the dilator shaft 302. The apex 320 provides a localized peak outer diameter of the dilator shaft 302 which results in lower push forces as the dilator shaft 302 is advanced through the sheath 8. In localizing the point of most expansion of the sheath 8 prevents the sheath 8 from shortening as happens with traditional dilators that have a constant diameter along their entire length. For example, when a conventional, uniformly formed dilator, is inserted into the introducer sheath 8, it forces the sheath 8 to assume the dilator’s diameter along its entire length, which in turn causes the sheath 8 to axially foreshorten in proportion to its expansion. In contrast, dilator system 300 disclosed herein provides localized expansion, allowing expansion/dilation of the introducer sheath 8 without negative effects on the sheath length.

[0136] As provided in FIG. 22, the leading tapered surface 314 can have an axial/longitudinal length greater than the axial/longitudinal length of the trailing tapered surface 316. As illustrated in FIG. 22, the leading tapered surface 314 can extend along a length (LI) of the dilator shaft 302 greater than a length (L2) the trailing tapered surface 316 extends along the dilator shaft 302. In some examples, because the trailing tapered surface 316 is shorter axially than the leading tapered surface 314 it reduces drag/friction between the leading tapered surface 314 and the sheath 8 when withdrawing the dilator shaft 302 from the sheath 8. [0137] As described herein, the ridges 306 project radially from the outer surface 308 of the tapered distal end 304. In some examples, the outer surface 308 has a constant outer diameter extending from the distal end 312/nose portion 322 toward the elongated body portion 330 of the dilator shaft 302. As a result, the structure and geometry of the ridges 306 defines the increasing/decreasing shape of the tapered distal end 304. In other examples, the outer surface 308 of the tapered distal end 304 extends at an increasing taper in a proximal direction (toward the elongated body portion 330). That is, the outer surface 308 extends at an increasing taper from the distal end 312/nose portion 322 toward the elongated body portion 330. The ridges 306 are provided along the (tapered) outer surface 308 and, as a result, the increasing taper shape of the outer surface 308 defines the increasing taper of the ridges 306.

[0138] As illustrated in FIGS. 21-22, some examples of the tapered distal end 304 optionally includes a nose portion 322 at the distal end 312 of the dilator shaft 302. The nose portion 322 extends between the distal end 312 of the dilator shaft 302 and the outer surface 308 of the tapered distal end 304. The outer surface of the nose portion 322 can be sized and shaped to prevent damage to the sheath 8 and/or blood vessel as the dilator shaft 302 is advanced in the sheath 8. For example, as illustrated in FIG. 22, the nose portion 322 may include a curved (convex) outer surface and/or an increasingly tapered outer surface extending between the distal end 312 of the dilator shaft 302 and the outer surface 308 of the tapered distal end 304.

[0139] In some examples, the nose portion 322 has an outer diameter less than the outer diameter of the tapered distal end 304. For example, the outer diameter of the nose portion 322 can be less than the outer diameter of the outer surface 308, less than the outer perimeter defined by the ridges 306, and/or less than the outer diameter of the elongated body portion 330. The tapered distal end 304 can include a distal end surface 324. In some examples, the distal end surface 324 includes flat surface extending generally perpendicular to the longitudinal axis of the dilator shaft 302 and/or a curved surface extending from the distal end 312 toward the tapered distal end 304. In some examples, the nose portion 322 defines a curved surface extending between the distal end surface 324 and the outer surface 308 of the tapered distal end 304.

[0140] As shown in FIGS. 19, 20, 22, and 23, the dilator shaft 302 includes an elongated body portion 330 extending between the tapered distal end 304 and the proximal end 310 of the dilator shaft 302. In some examples, the elongated body portion 330 can be substantially cylindrical. It is contemplated the that elongated body portion 330 may have any other curvilinear shape in cross-section. As described herein, the tapered distal end 304 and elongated body portion 330 of the dilator shaft 302 are sized and configured to be received within the proximal end of the sheath hub 20 and/or locking sleeve 28. In some examples, the diameter of the elongated body portion 330 ranges from 10 Fr to 20 Fr. In some examples, the diameter of the elongated body portion 330 ranges from 15 Fr to 18 Fr. In some examples, the diameter of the elongated body portion 330 is approximately 16 Fr.

[0141] FIG. 23 provides a cross-sectional view of the tapered distal end 304 taken along section line A-A in FIG. 21. As shown in FIG. 23, the dilator system 300 can include a central lumen 332 extending therethrough. In some examples, the central lumen 332 can be sized and configured for receiving a guide wire. The dilator shaft 302 can, in some examples, be composed of at least one of HDPE or LDPE.

[0142] As described herein, the dilator system 300 optionally includes a dilator hub 340 coupled to the proximal end 310 of the dilator shaft 302. The dilator hub 340 is optionally configured to be gripped by an operator, such that force may be applied to the dilator system 300/dilator shaft 302 via the dilator hub 340. In some examples, the dilator hub 340 can include similar mating features as the locking hub 30 for mating with the locking sleeve 28. [0143] FIG. 24 illustrates a cross-section view of the example dilator hub 340 and the proximal portion of the dilator shaft 302. In the illustrated example, the dilator hub 340 includes a central lumen 342 extending between a proximal end 344 and a distal end 346 of the dilator hub 340. At least a portion of the central lumen 342 is defined by a recessed opening 350 for receiving the proximal end 310 of the dilator shaft 302. The recessed opening 350 extends from the distal end 346 of the dilator hub 340 towards the proximal end 344 of the dilator hub 340. As illustrated in FIG. 24, the recessed opening 350 can be substantially axially aligned with the central lumen 342 of the dilator hub 340. In some examples, the recessed opening 350 has a cross-sectional shape corresponding to the cross- sectional shape of the dilator shaft 302. In the illustrated example, the recessed opening 350 and the dilator shaft 302 both have a circular cross-sectional shape. The dilator shaft 302 can be fixedly coupled to the dilator hub 340 at the recessed opening 350. This can be accomplished, for example, via a press fit, an interference fit, a snap fit, a mechanical fastener, a chemical fastener (for example, an adhesive), a weld, a thermal process, and/or any other suitable coupling process known in the art. In some examples, the dilator shaft 302 is removably coupled to the recessed opening 350 of the dilator hub 340. For example, the dilator shaft 302 can be removably coupled to the dilator hub 340 by a removable mechanical coupling, a threaded coupling, or similar suitable removable coupling processes known in the art. [0144] As illustrated in FIG. 24, the central lumen 342 of the dilator hub 340 includes a proximal recessed opening 352 extending from the proximal end 344 toward the distal end 346 of the dilator hub 340. In some examples, the proximal recessed opening 352 is separated from the recessed opening 350 by a shoulder 360. The central lumen 342 of the dilator hub 340 includes the opening 362 extending through the shoulder 360. That is, in some examples, the central lumen 342 is defined by the (distal) recessed opening 350, proximal recessed opening 352, and the opening 362 extending through the shoulder 360. As illustrated in FIG. 24, the recessed opening 350, proximal recessed opening 352, and opening 362 are axially aligned along the central axis of the dilator hub 340.

[0145] As illustrated in FIG. 24, the proximal recessed opening 352 includes an optional decreasing tapered portion 354 having a frustoconical shape with a diameter that decreases in the distal direction. The shape of the decreasing tapered portion 354 can help guide any medical instrument into the central lumen 332 of the dilator shaft 302.

[0146] In some examples, an outer surface 370 of the dilator hub 340 includes a large diameter portion 372 adjacent the distal end 346 and a reduced diameter portion 374 adjacent the proximal end 344. In some examples, the reduced diameter portion 374 includes a coupling member 376 (for example, a threaded surface) for engaging a corresponding medical device (for example, a Luer connection).

[0147] According to the present disclosure, the dilator shaft 302 includes a central lumen 332 extending therethrough. In some examples, the central lumen 332 is in fluid communication with a central lumen 342 of the dilator hub 340. The dilator system can optionally include a sealing member 380 positioned between the dilator shaft 302 and the dilator hub 340. For example, the sealing member 380 can be positioned between the distal end surface 234 of the dilator shaft 302 and the proximal end surface 364 of the recessed opening 350 (for example, defined by the shoulder 360), as shown in FIG. 24. The sealing member 380 can maintain a sealed connection between the central lumen 332 of the dilator shaft 302 and central lumen 342 of the dilator hub 340. For example, the sealing member 380 can prevent fluid communication into and/or out of the fluid pathway defined between the dilator shaft 302 and the dilator hub 340 and, as a result, can maintain hemostasis between them along the dilator system 300. The sealing member 380 can, for example, prevent blood loss/blood flow between the guide wire and the dilator hub 340. In some examples, the sealing member 380 can be an o-ring, a polymer o-ring, a gasketed interface, or a similar sealing member.

[0148] FIGS. 25-27 show additional examples of the tapered distal end 304 of the dilator shaft 302. The example tapered distal ends 304 illustrated in FIGS. 25-27 do not include longitudinally extending ridges 306. In each example, the illustrated tapered distal end 304 includes a relatively smooth leading tapered surface 314/ou ter surface 308 extending between the distal end 12 and the apex 320. For example, the outer surface 308 of the tapered distal end 304 can be substantially frustoconical shape. In the illustrated examples, the apex 320 defines the maximum outer diameter of the tapered distal end 304 and elongated body portion 330. In the example tapered distal end 304 illustrated in FIG. 25, the trailing tapered surface 316 defines a generally convex outer surface extending from the apex 320 to the elongated body portion 330. In the example tapered distal end 304 illustrated in FIG. 26, the trailing tapered surface 316 has a generally linear/frustoconical shape extending from the apex 320 to the elongated body portion 330. In comparing the example tapered distal ends 304 illustrated in FIGS. 25 and 26, the tapered distal end 304 illustrated in FIG. 26 has a trailing tapered surface 316 that extends along a greater length of the dilator shaft 302 than the trailing tapered surface 316 of the tapered distal end 304 illustrated in FIG. 25.

[0149] FIG. 27 illustrates a cross-sectional view of another example tapered distal end 304. As shown in FIG. 27, the apex 320 of the tapered distal end 304 can optionally include a circumferential ridge that protrudes from the outer surface 308 of the tapered distal end 304. [0150] A method of expanding a sheath 8 and/or blood vessel using the present dilator system 300 is described herein. FIG. 28 illustrates a side view of the example sheath system and dilator system 300 side-by-side. FIG. 29 provides a side cross-sectional view of the sheath 8 with the dilator system 300 received within the central lumen 9 of the sheath 8. The sheath system includes any of the example radially expandable sheath 8 configurations described herein. In the present example, the sheath 8 includes a continuous inner layer 202 including folded portion 218. As described herein, the sheath 8 is movable between an unexpanded configuration at a first diameter and an expanded configuration at a second, larger, diameter.

[0151] As described herein, the dilating portion and/or dilator shaft 302 of the dilator system 300, when received within the central lumen 9 of the sheath 8, provides an outwardly directed radial force on the central lumen 9 of the sheath 8 and/or blood vessel, causing it to expand/dilate in advance of delivery of the medical device therethrough. As described herein, pre-dilating the sheath 8 and/or blood vessel before the medical device (and any corresponding delivery system) is advanced through the sheath 8 reduces the push forces needed to advance the medical device through the sheath 8 and to the treatment site. Predilating the sheath 8 releases/loosens bonding or adhesion between the sheath 8 layers, and pre-dilating the blood vessel reduces the degree to which extreme constriction in patient anatomy limits or prevents sheath 8 expansion or otherwise makes sheath 8 expansion more difficult.

[0152] In some implementations, the sheath 8 can be pre-dilated (fully and/or partially) along all or a portion of the length of the sheath 8 prior to delivery of the medical device. This can be done during sheath 8 prep, prior to sheath 8 insertion into the patient and/or with the sheath 8 at least partially inserted into the patient. In some examples, a sheath 8 is inserted into a femoral artery of a patient.

[0153] To dilate the sheath 8, the distal end 312 of the dilator shaft 302 is first introduced into the proximal end of the sheath 8 via the sheath hub 20. The dilator shaft 302 is then advanced within the central lumen of the sheath 8.

[0154] When used to dilate the blood vessel, the sheath 8 is inserted at least partially into the patient’s blood vessel. The sheath 8 can be inserted into the patient’s blood vessel before the dilator shaft 302 is introduced into the sheath 8/sheath hub 20. In some examples, when introduced into the patient’s blood vessel the introducer 6 is received within the central lumen of the sheath 8. The introducer 6 provides axial and radial support to the sheath 8 as it is advanced within the patient. The introducer 6 is then withdrawn from the sheath 8, leaving the central lumen open/available for the dilator shaft 302 to be positioned within the sheath 8. In some examples, a guide wire can be at least partially inserted into the patient’s blood vessel and the sheath 8/introducer 6 can be advanced over the guide wire through the blood vessel to the treatment site. In some examples, the dilator shaft 302 is also advanced over the guide wire through the sheath 8.

[0155] Next, the dilating portion, for example, the tapered distal end 304 of the dilator shaft 302 (and at least a portion of the elongated body portion 330) is advanced through a portion of the central lumen 9 of the sheath 8. In some examples, the dilating portion is provided at the tapered distal end 304 where the outer diameter of the tapered distal end 304 is greater than the inner diameter of the sheath 8/diameter of the central lumen 9 of the sheath 8. As such, movement of the tapered distal end 304 within the central lumen 9 of the sheath 8 causes the sheath 8 to radially expand. For example, the tapered distal end 304 of the dilator shaft 302 is advanced through a portion of the central lumen of the sheath 8 such that the tapered distal end 304 exerts an outwardly directed radial force against the central lumen 9 of the sheath 8, causing the sheath 8 to locally expand from the unexpanded configuration at the first diameter, to the expanded configuration at the second, larger, diameter. Specifically, in some examples, advancing the tapered distal end 304 of the dilator shaft 302 through the central lumen 9 of the sheath 8 causes the inner layer 202 proximate the tapered distal end 304 to locally expand from the unexpanded configuration to the expanded configuration. The portion of the sheath 8 locally contracts at least partially back to/toward the unexpanded configuration as the tapered distal end 304 passes therethrough.

[0156] As described herein, in some examples, the dilator shaft 302 includes a plurality of ridges 306 provided along the tapered distal end 304. The ridges 306 can reduce the contact area of the dilator shaft 302 as it is advanced through the sheath 8, thereby helping to additionally reduce the push forces needed to move the dilator shaft 302 within the sheath 8. Accordingly, in some examples, expansion of the sheath 8 is directed in response to the outwardly directed radial force exerted on the central lumen 9 of the inner layer by the ridges 306 as the tapered distal end 304 including the ridges 306 passes through the sheath 8. For example, the sheath 8 will locally expand from the unexpanded configuration in which the central lumen 9 of the sheath has a first diameter to/toward the expanded configuration in which the central lumen 9 has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer 202 by the ridges 306. The portion of the sheath 8 locally contracts at least partially back to/toward the unexpanded configuration as the tapered distal end 304/ridges 306 passes therethrough.

[0157] In some examples, the sheath 8 includes multiple layers bonded together, for example the inner layer 202 bonded to the outer layer 204 bonded to the outer layer 204 via chemical and/or thermal bonding. Pre-dilating the sheath 8 can, advantageously, release and/or weaken the bond between the layers reducing the push force needed to advance the medical device through the sheath 8. Accordingly, as the sheath 208 moves from the unexpanded configuration to the expanded configuration, the bonding between the inner layer 202 and the outer layer 204 can be at least partially released.

[0158] In some examples, as described herein, the inner layer 202 of the sheath 8 includes a folded portion 218, as illustrated in FIG. 17. Locally expanding the portion of the sheath 8 causes the folded portion 218 of the inner layer 202 to at least partially unfold, as illustrated in FIG. 18. As provided in FIG. 17, in some examples, the sheath 8 includes a discontinuous outer layer 204 provided over the inner layer 202, where the outer layer 204 is discontinuous and includes an overlapping portion 220 and an underlying portion 222. As described herein in reference to FIG. 17, in the unexpanded configuration, the overlapping portion 220 overlaps the underlying portion 222 with the folded portion 218 of the inner layer 202 disposed between the overlapping portion 220 and the underlying portion 222. In the expanded configuration, as illustrated in FIG. 18, the outer layer 204 includes a gap 232 between the longitudinal edges of the overlapping portion 220 and the underlying portion 222 of the outer layer 204 (for example, first edge 224 and second edge 225). In some examples, advancing the tapered distal end 304 of the dilator shaft 302 through the portion of the central lumen of the sheath 8 causes that portion of the sheath 8 to move from the unexpanded configuration to the expanded configuration, the overlapping portion 220 of the outer layer 204 to move circumferentially with respect to the underlying portion 222, and the folded portion 218 of the inner layer 202 at least partially unfolds. In some examples, the inner layer 202 is bonded to the outer layer 204, advancing the tapered distal end 304 through the portion of the centra] lumen 9 of the sheath 8 causes bonding along the portion of the sheath 8 to at least partially release.

[0159] It is contemplated that the tapered distal end 304 of the dilator shaft 302 can be advanced partially and/or completely through the central lumen of the sheath 8. In some examples, the tapered distal end 304 is advanced along a majority of the length of the sheath 8 causing the majority of the length of the sheath 8 (and/or corresponding portion of the blood vessel) to be pre-dilated. For example, the dilator shaft 302 can be advanced into the sheath 8 until the dilator hub 340 abuts a sheath hub 20. In some examples the tapered distal end 304 is advanced up to the distal end of the sheath 8 such that the distal end of the sheath 8/distal sheath opening is not pre-dilated. In some examples the tapered distal end 304 is advanced up to and through the distal opening of the sheath 8, causing the distal opening of the sheath to be pre-dilated.

[0160] In some examples, the tapered distal end 304 is advanced only partially within the central lumen of the 8, such that only a portion of the sheath 8 is pre-dilated. For example, the tapered distal end 304 can be used to pre-dilate the strain relief layer 26 (when included). As described herein, in some examples, the strain relief layer 26 is included to limit radial expansion along a proximal portion of the sheath 8. When used to pre-dilate the strain relief layer 26, the tapered distal end 304 is advanced through the central lumen 9 of the sheath 8 along the desired length of the strain relief layer 26. The strain relief layer 26 then locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, in response to an outwardly directed radial force exerted on the central lumen of the sheath 8 by the tapered distal end 304. The strain relief layer 26 then locally contracts at least partially back to/toward the unexpanded configuration as the tapered distal end 304 passes through the strain relief layer 26.

[0161] With the desired length of the sheath 8 pre-dilated, the dilator shaft 302/dilator system 300 can then be withdrawn distally within the central lumen of the sheath 8 and removed from the sheath 8/sheath hub 20. As the dilator shaft 302/dilator system 300 is withdrawn through/from the sheath 8, the sheath 8 then locally contracts at least partially back to the unexpanded configuration as the tapered distal end 304 moves through the sheath 8.

[0162] With the central lumen of the sheath 8 free of the dilator shaft 302, the medical device is then introduced into the central lumen 9 at the proximal end of the sheath 8. The medical device is then advanced through the central lumen 9 of the sheath 8. In some examples, the movement of the medical device within the central lumen 9 of the sheath 8 causes the sheath 8 to radially expand as the medical device exerts an outwardly directed radial force against the central lumen 9 of the sheath 8, causing the sheath 8 to locally expand from the unexpanded configuration at the first diameter, to/toward the expanded configuration at the second, larger, diameter. As the medical device passes through the sheath 8, the portion of the sheath 8 locally contracts at least partially back to/toward the unexpanded configuration.

[0163] The medical device, for example implant 12, is advanced through the sheath 8 and beyond a distal opening in the sheath 8 to the treatment site within the blood vessel and/or heart tissue of the patient. The medical device is deployed beyond distal opening of the sheath 8 and delivered to the patient. Once the medical device is delivered to the patient, the delivery apparatus is removed/withdrawn from the sheath 8.

[0164] In some examples, advancing the prosthetic device through the central lumen 9 of the sheath 8 can include advancing the delivery apparatus and the prosthetic device through the lumen 9 of the sheath 8 and into the vasculature of a patient. Accessing the treatment site may require creating an opening in the heart tissue (for example, foramen ovalis) of the patient. In some examples, after the dilator shaft 302/dilator system 300 is removed from the sheath 8, a cutting instrument can be advanced through the sheath 8 to create an opening in the patient’s heart tissue. In some examples, the sheath 8 is inserted into a femoral artery of the patient.

[0165] The present disclosure also provides for a bi-directional dilator system 400 illustrated, for example, in FIGS. 30 and 31. The bi-directional dilator system 400 can include a dilator shaft 402 having a first end 412 and an opposing second end 414. The bi-directional dilator system 400 includes a first tapered end 416 provided adjacent the first end 412 of the dilator shaft 402, and a second tapered end 418 provided adjacent the second end 414 of the dilator shaft 402. As illustrated in FIG. 30, the bi-directional dilator system 400 has a first dilating portion 420 adjacent the first tapered end 416 and a second dilating portion 440 adjacent the second tapered end 418. The elongated body portion 410 of the dilator shaft 402 extends between the first dilating portion 420 and second dilating portion 440.

[0166] In some examples, the first dilating portion 420 and the second dilating portion 440 have the same diameter. In some examples, the diameter (dl) of the first dilating portion 420 varies from the diameter (d2) of the second dilating portion 440. For example, the diameter (d2) of the second dilating portion 440 is greater than the diameter (dl) of the first dilating portion 420. In some examples, as illustrated in FIG. 30, the diameter (dl) of the first dilating portion 420 and the diameter (d2) of the second dilating portion 440 are greater than the diameter (D3) of the elongated body portion 410 and/or the dilator shaft 402. In further examples, the diameter (d4) of the first body portion 422, the diameter (d5) second body portion 424, and/or the diameter (d3) elongated body portion 410 can range from 10 Fr to 16 Fr, preferably 12 Fr.

[0167] In some examples, the first dilating portion 420 is offset from the first tapered end 416 such that the first body portion 422 of the dilator shaft 402 extends between the first tapered end 416 and the first dilating portion 420. Similarly, in some examples, the second dilating portion 440 is offset from the second tapered end 418 such that the second body portion 424 of the dilator shaft 402 extends between the second tapered end 418 and the second dilating portion 440. In some examples, the length of the first body portion 422 corresponds with the length of the second body portion 424. In further examples, the length of the first body portion 422 is different from the length of the second body portion 424. For example, the length of the first body portion 422, measured between the end of the first tapered end 416 and the first dilating portion 420, can range from 10 mm to 60 mm. Similarly, the length of the second body portion 424, measured between the end of the second tapered end 418 and the second dilating portion 440, can range from 10 mm to 60 mm. In further examples, the length of the first tapered end 416 and/or the second tapered end 418 can range from 20 mm to 70 mm. In some examples, the length of the elongated body portion 410 extending between the first dilating portion 420 and the second dilating portion 440 can range from 400 mm to 600 mm.

[0168] As illustrated in the example bi-directional dilator system 400 of FIG. 30, the first dilating portion 420 has a leading tapered surface 426 having an increasing taper extending from the first body portion 422 in a direction towards the second end 414 of the dilator shaft 402. The first dilating portion 420 also includes a trailing tapered surface 428 having a decreasing taper from the leading tapered surface 426 to elongated body portion 410 extending in a direction toward the first end 412 of the dilator shaft 402. In some examples, the first dilating portion 420 includes an apex surface 430 extending between the leading tapered surface 426 and the trailing tapered surface 428, the apex surface 430 having a diameter greater than the leading tapered surface 426 and the trailing tapered surface 428. [0169] Similarly, in some examples, the second dilating portion 440 includes a leading tapered surface 442 having an increasing taper extending from the second body portion 424 in a direction towards the first end 412 of the dilator shaft 402. The second dilating portion 440 similarly includes a trailing tapered surface 444 having a decreasing taper from the leading tapered surface 442 to the elongated body portion 410 extending in a direction toward the first end 412 of the dilator shaft 402. The second dilating portion 440 similarly includes an apex surface 446 extending between the leading tapered surface 442 and the trailing tapered surface 444, the apex surface 446 having a diameter greater than the leading tapered surface 442 and the trailing tapered surface 444. In some examples, the apex surface 430 of the first dilating portion 420 and the apex surface 446 of the second dilating portion 440 can both define a generally cylindrical shape in cross section.

[0170] In some examples, the axial length of the apex surface 430 of the first dilating portion 420 corresponds with the axial length of the apex surface 446 of the second dilating portion 440. In further examples, the axial length of the apex surface 430 of the first dilating portion 420 is greater than the axial length of the leading tapered surface 426 and/or the trailing tapered surface 428 of the first dilating portion 420. In some examples, the axial length of the apex surface 446 of the second dilating portion 440 is greater than the axial length of the leading tapered surface 442 and/or the trailing tapered surface 444 of the second dilating portion 440.

[0171] In some examples, the axial length of the leading tapered surface 426 of the first dilating portion 420 is greater than the axial length of the trailing tapered surface 428 of the first dilating portion 420. In some examples, the axial length of the leading tapered surface 442 of the second dilating portion 440 is greater than the axial length of the trailing tapered surface 444 of the second dilating portion 440.

[0172] In some examples, the angle of the leading tapered surface 426 of the first dilating portion 420 is less than the angle of the trailing tapered surface 428 of the first dilating portion 420. In some examples, the angle of the leading tapered surface 442 of the second dilating portion 440 is less than the angle of the trailing tapered surface 444 of the second dilating portion 440. The angles of the leading and trailing tapered surfaces of each of the first and second dilating portions is measured between the outer surface of the dilator shaft 402 and the corresponding leading and trailing tapered surfaces of each of the first and second dilating portions. In some examples, the angle and length of the leading tapered surface 426 of the first dilating portion 420 is symmetrical with the angle and length of the trailing tapered surface 428 of the first dilating portion 420 about a midline of the apex surface 430 of the first dilating portion 420. In some examples, the angle and length of the leading tapered surface 442 of the second dilating portion 440 is symmetrical with the angle and length of the trailing tapered surface 444 of the second dilating portion 440 about a midline of the apex surface 446 of the second dilating portion 440. In further examples, the angle and length of the leading tapered surface 426 of the first dilating portion 420 is asymmetrical with the angle and length of the trailing tapered surface 428 of the first dilating portion 420 about the midline of the apex surface 430 of the first dilating portion 420. Similarly, in some examples, the angle and length of the leading tapered surface 442 of the second dilating portion 440 is asymmetrical with the angle and length of the trailing tapered surface 444 of the second dilating portion 440 about the midline of the apex surface 446 of the second dilating portion 440.

[0173] According to the present disclosure, the bi-directional dilator system 400 can be made of various materials. In some examples, the first dilating portion 420 and the second dilating portion 440 can be formed from the same material as the dilator shaft 402. For example, the first dilating portion 420 and second dilating portion 440 can both be formed from PEK, LDP, or HDP. In further examples, the first dilating portion 420 and the second dilating portion 440 can be formed from a different material as the dilator shaft 402. For example, the first dilating portion 420 and the second dilating portion 440 can be formed from PEK and the dilator shaft 402 can be formed from LDP, HDP.

[0174] In some examples, the first dilating portion 420 and the second dilating portion 440 can be integrally formed with the dilator shaft 402. In further examples, the first dilating portion 420 and/or the second dilating portion 440 can be separately formed and coupled to the dilator shaft 402. For example, the first dilating portion 420 and/or second dilating portion 440 can be overmolded to the dilator shaft 402 and/or coupled to the dilator shaft 402 by a chemical fastener (for example, an adhesive), a weld (for example, ultrasonic weld), a thermal process, and/or any other suitable coupling process known in the art.

[0175] As illustrated in FIG. 31, in some examples, the bi-directional dilator system 400 includes an adapter 450 coupled to the dilator shaft 402 providing a handle for the dilator shaft 402. In some examples, the adapter 450 can be releasably or fixedly coupled to the dilator shaft 402. In some examples, the adapter 450 is sized and configured to couple to at least one of the first dilating portion 420 and/or the second dilating portion 440. The adapter 450 can be coupled to the dilator shaft 402, first dilating portion 420 and/or second dilating portion 440 via a press fit, an interference fit, a snap fit, a mechanical fastener, a chemical fastener (for example, an adhesive), a weld, a thermal process, and/or any other suitable coupling process known in the art In further examples, the sheath 8 and/or sheath hub 20 can be releasably coupled to a coupling feature provided on the adapter 450.

[0176] A method of pre-dilating sheath 8 and/or blood vessel using the bi-directional dilator system 400 is described herein. The sheath 8 includes any of the example expandable sheath 8 configurations described herein. The method using the bi-directional dilator system 400 is similar to the method described above with reference to the dilator system 300 illustrated in FIGS. 19-29. The differences between the method using dilator system 300 and the bidirectional dilator system 400 are provided.

[0177] In the present example, the bi-directional dilator system 400 includes a first dilating portion 420 and second dilating portion 440, where the diameter of the second dilating portion 440 is greater than the diameter of the first dilating portion 420, and the diameter of both the first dilating portion 420 and the second dilating portion 440 is greater than the diameter of the dilator shaft 402.

[0178] In some examples, the user selects which of the first dilating portion 420 and/or the second dilating portion 440 should be used to pre-dilate the sheath 8 and/or blood vessel based on the sheath 8 and/or blood vessel geometry and/or composition. For example, which of the first dilating portion 420 or second dilating portion 440 is first introduced into the sheath 8 is selected based on at least one of the unexpanded diameter of the central lumen of the sheath 8, the desired expanded diameter of the central lumen of the sheath 8, the amount of bonding between the various layers of the sheath 8, and/or patient anatomy including, for example, the unexpanded diameter of the blood vessel, the desired expanded diameter of the blood vessel, tortuosity of the blood vessel, and/or health of the blood vessel. As a result, the first tapered end 416 or the second tapered end 418 with the corresponding/desired diameter is selected to be introduced first into the central lumen of the sheath 8.

[0179] In some examples, before the bi-directional dilator system 400 is inserted into the sheath 8, the adapter 450 is coupled to the first dilating portion 420, the second dilating portion 440, or the outer layer 204. For example, the adapter 450 can be coupled to the dilating portion that is not going to be used for pre-dilating the sheath 8/blood vessel. In some examples, the adapter 450 is coupled along a portion of the elongated body portion 410 of the dilator shaft 402. Once coupled, the user can utilize the adapter 450 as a handle or grip for manipulating the bi-directional dilator system 400 within the sheath 8 and/or blood vessel. [0180] The bi-directional dilator system 400 is introduced into the sheath 8 in a similar manner as described above in reference to dilator system 300. As the bi-directional dilator system 400/dilator shaft 402 is advanced through a portion of the central lumen 9 of the sheath 8 either the first dilating portion 420 or the second dilating portion 440 (whichever is introduced first/distally positioned with respect to the sheath 8) exerts an outwardly directed radial force against the central lumen 9 of the sheath 8, causing the inner layer proximate the first dilating portion 420 and/or the second dilating portion 440 to locally expand from the unexpanded configuration to/toward the expanded configuration. The sheath 8 then locally contracts at least partially back to the unexpanded configuration as the first dilating portion 420 and/or second dilating portion 440 passes through the central lumen.

[0181] In some examples, both the first dilating portion 420 and the second dilating portion 440 are advanced within the central lumen 9 of the sheath 8 for pre-dilating the sheath 8. For example, the first dilating portion 420 can be received and advanced within the central lumen 9 of the sheath 8, causing the sheath 8 to locally expand. The bi-directional dilator system 400/dilator shaft 402 is then further advanced within the sheath 8, causing the second dilating portion 440 to be received and advanced within the central lumen 9 of the sheath 8 and causing the central lumen 9 of the sheath 8 to further expand.

[0182] In some examples, the first tapered end 416, second tapered end 418, and/or the dilator shaft 402 exert an outwardly directed force against the inner layer of the sheath 8, causing the sheath 8 to radially expand toward the expanded configuration as the bidirectional dilator system 400 is introduced into and moved within the sheath 8. The sheath 8 then locally contracts at least partially back to/toward the unexpanded configuration as the first tapered end 416, second tapered end 418, and/or the dilator shaft 402 passes through the central lumen.

[0183] The bi-directional dilator system 400 can be used to dilate a desired portion of the sheath 8, including the strain relief layer 26, in a similar manner as described herein in reference to dilator system 300. The various layers of the sheath 8, including the folded portions 218, can expand/unfold in a similar manner as described herein in reference to FIGS. 17 and 18 and dilator system 300.

[0184] With the desired length of the sheath 8 pre-dilated and/or the bonds between the various layers at least partially released, the bi-directional dilator system 400/dilator shaft 402 can then be withdrawn distally within the central lumen 9 of the sheath 8 and removed from the sheath 8/sheath hub 20. As the bi-directional dilator system 400/dilator shaft 402 is withdrawn through/from the sheath 8, the sheath 8 then locally contracts at least partially back to the unexpanded configuration as the first dilating portion 420 and/or second dilating portion 440 move(s) through the sheath 8. [0185] With the central lumen 9 of the sheath 8 free of the bi-directional dilator system 400/dilator shaft 402, the medical device can then be introduced into the central lumen 9 at the proximal end of the sheath 8. As described herein, as the medical device is advanced through the central lumen 9 of the sheath 8, the sheath 8 locally radially expands in response to the outwardly directed radial force against the central lumen 9 of the sheath 8 exerted by the medical device. The sheath 8 expands from the unexpanded configuration at the first diameter, to/toward the expanded configuration at the second, larger, diameter. As the medical device passes through the sheath 8, the portion of the sheath 8 locally contracts at least partially back to/toward the unexpanded configuration.

[0186] With the distal end of the sheath 8 positioned at the treatment site, the medical device is advanced through the sheath 8 and deployed beyond distal opening of the sheath 8 and delivered to the treatment site within the blood vessel and/or heart tissue of the patient. Once the medical device is delivered to the patient, the delivery apparatus is removed from the sheath 8.

[0187] In each of the sheath 8 and dilator (dilator system 300/bi-directional dilator system 400) examples described herein, the medical device/implant may be a prosthetic device mounted in a radially crimped state on a delivery apparatus, and advancing the prosthetic device through the central lumen of the sheath 8 includes advancing the delivery apparatus and the prosthetic device through central lumen of the sheath 8 and into a vasculature of the patient. In some examples, the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient. In some examples, the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the sheath 8.

[0188] Exemplary Aspects

[0189] In view of the described processes and compositions, hereinbelow are described certain more particularly described aspects of the disclosures. These particularly recited aspects should not, however, be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language and formulas literally used therein.

[0190] Example 1: A dilator system including: a dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft. [0191] Example 2: The dilator system according to any example herein, particularly example 1, wherein the ridge defines a maximum outer diameter (Dmax) of the dilator shaft and/or the tapered distal end.

[0192] Example 3: The dilator system according to any example herein, particularly examples 1-2, wherein the ridge includes a plurality of ridges spaced around a circumference of the tapered distal end.

[0193] Example 4: The dilator system according to any example herein, particularly examples 1-3, wherein the ridge includes: a leading tapered surface adjacent the distal end of the dilator shaft and having an increasing taper; and a trailing tapered surface extending between the leading tapered surface and the proximal end of the elongated body portion/dilator shaft, the trailing tapered surface having a decreasing taper.

[0194] Example 5: The dilator system according to any example herein, particularly example 4, wherein the leading tapered surface and the trailing tapered surface meet at an apex of the ridge, the apex defining a maximum outer diameter (Dmax) of the dilator shaft.

[0195] Example 6: The dilator system according to any example herein, particularly examples 4-5, wherein the leading tapered surface extends along a length (LI) of the dilator shaft greater than a length (L2) the trailing tapered surface extends along the dilator shaft. [0196] Example 7: The dilator system according to any example herein, particularly examples 1-6, wherein the outer surface of the tapered distal end extends at an increasing taper toward the elongated body portion of the dilator shaft, where the ridge is provided along the tapered outer surface (for example, the tapered outer surface extends at an increasing tapered between the nose portion and the elongated body portion).

[0197] Example 8: The dilator system according to any example herein, particularly example

7, wherein the tapered distal end 304 includes a nose portion extending between a distal end of the dilator shaft and the (tapered) outer surface of the tapered distal end.

[0198] Example 9: The dilator system according to any example herein, particularly example

8, wherein the nose portion has an outer diameter less than an outer diameter of the outer surface of the tapered distal end.

[0199] Example 10: The dilator system according to any example herein, particularly examples 1-9, wherein the elongated body portion has a generally cylindrical shape in cross section.

[0200] Example 11 : The dilator system according to any example herein, particularly examples 1-10, wherein the dilator shaft includes a central lumen extending therethrough. [0201] Example 12: The dilator system according to any example herein, particularly examples 1-11, wherein the dilator shaft is composed of at least one of HDPE or LDPE. Hub [0202] Example 13: The dilator system according to any example herein, particularly examples 1-12, wherein the dilator hub includes a central lumen extending between a proximal end and a distal end of the dilator hub, at least a portion of the central lumen defining a recessed opening for receiving the proximal end of the dilator shaft, the recessed opening extending from a distal end of the dilator hub towards the proximal end of the dilator hub (for example, the recessed opening axially aligned with the central lumen of the dilator hub).

[0203] Example 14: The dilator system according to any example herein, particularly example 13, wherein the recessed opening has a cross-sectional shape corresponding to the cross-sectional shape of the dilator shaft.

[0204] Example 15: The dilator system according to any example herein, particularly examples 13-14, wherein the recessed opening has a circular cross-sectional shape. [0205] Example 16: The dilator system according to any example herein, particularly examples 13-15, wherein the dilator shaft is fixedly coupled to the dilator hub at the recessed opening.

[0206] Example 17: The dilator system according to any example herein, particularly examples 13-16, wherein the dilator shaft is removably coupled to the recessed opening of the dilator hub.

[0207] Example 18: The dilator system according to any example herein, particularly examples 13-17, wherein the central lumen of the dilator hub includes a proximal recessed opening extending from the proximal end toward the distal end of the dilator hub, the proximal recessed opening separated from the recessed opening by a shoulder, wherein the central lumen of the dilator hub further includes an opening extending through the shoulder. [0208] Example 19: The dilator system according to any example herein, particularly example 18, wherein the proximal recessed opening includes a decreasing tapered portion defining a frustoconical shape with decreasing taper/diameter extending in a distal direction. [0209] Example 20: The dilator system according to any example herein, particularly examples 13-19, where an outer surface of the dilator hub includes a large diameter portion adjacent the distal end and a reduced diameter portion adjacent the proximal end, where the reduced diameter portion includes a coupling member. [0210] Example 21: The dilator system according to any example herein, particularly examples 1-20, wherein the dilator shaft includes a central lumen extending therethrough, the central lumen in fluid communication with a central lumen extending through the dilator hub. [0211] Example 22: The dilator system according to any example herein, particularly example 21, further including a sealing member provided between the proximal end of the dilator shaft and the and the dilator hub, the sealing member for maintaining a sealed connection between the central lumen of the dilator shaft and central lumen of the dilator hub. [0212] Example 23: The dilator system according to any example herein, particularly examples 21-22, wherein the dilator hub includes a recessed opening for receiving a proximal end of the dilator shaft, the recessed opening extending from a distal end of the dilator hub towards the proximal end of the dilator hub, wherein the sealing member is provided between a proximal end surface of the recessed opening and the distal end surface of the dilator shaft. [0213] Example 24: A sheath system comprising: a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portions; and a dilator system for expanding at least a portion of the sheath, the dilator system including: a dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft; wherein at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration.

[0214] Example 25: The sheath system according to any example herein, particularly example 24, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the ridge (and/or the tapered distal end, dilator shaft, and/or medical device) provided on the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the ridge (and/or tapered distal end, dilator shaft and/or medical device) passes through the lumen.

[0215] Example 26: The sheath system according to any example herein, particularly examples 24-25, wherein the outer diameter of the tapered distal end is greater than an inner diameter of the sheath, as such, movement of the dilator shaft within the central lumen of the sheath causes the sheath to radially expand.

[0216] Example 27: The sheath system according to any example herein, particularly examples 24-26, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

[0217] Example 28: The sheath system according to any example herein, particularly examples 24-27, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, as the sheath moves from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer moves circumferentially with respect to the underlying portion and the folded portion of the inner layer at least partially unfolds, wherein, in the expanded configuration, the outer layer includes a gap between the longitudinal edges of the overlapping portion and the underlying portion of the outer layer (for example, first edge and second edge).

[0218] Example 29: The sheath system according to any example herein, particularly example 28, wherein the inner layer is bonded to the outer layer, wherein, as the sheath moves from the unexpanded configuration to the expanded configuration, the bonding between the inner layer and the outer layer is least partially released.

[0219] Example 30: The sheath system according to any example herein, particularly examples 28-29, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, wherein at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the tapered distal end of the dilator shaft (for example, the dilator shaft and/or a medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the tapered distal end passes through the sheath.

[0220] Example 31 : The sheath system according to any example herein, particularly examples 24-30, further including: a sheath hub fixedly coupled to the proximal end of the sheath, the sheath hub including a central lumen extending therethrough and coaxial with the central lumen of the sheath, wherein the dilator shaft is sized and configured to be received (for example, slidably and/or rotatably received) within the central lumen of the sheath hub. [0221] Example 25: A method of dilating a sheath comprising: (1) providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; (2) providing a dilator system for expanding at least a portion of the sheath, the dilator system including: the dilator shaft including a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter of the dilator shaft (for example, the ridge reducing the contact area of the dilator shaft as it is advanced through the sheath, thereby reducing the needed push force); an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft; (3) introducing the dilator shaft (for example, the tapered distal end of the dilator shaft and at least a portion of the elongated body portion) into the central lumen of the sheath; (4) advancing the tapered distal end through a portion of the central lumen of the sheath such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration; and (5) removing the dilator shaft from the sheath.

[0222] Example 33: The method according to any example herein, particularly example 32, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the ridge (and/or the tapered distal end, dilator shaft, and/or medical device) provided on the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the ridge (and/or tapered distal end, dilator shaft and/or medical device) passes through the central lumen. [0223] Example 34: The method according to any example herein, particularly examples 32-

33, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

[0224] Example 35: The method according to any example herein, particularly examples 32-

34, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between the longitudinal edges of the overlapping portion and the underlying portion of the outer layer (for example, first edge and second edge), wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

[0225] Example 36: The method according to any example herein, particularly example 35, wherein the inner layer is bonded to the outer layer, wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes bonding along the portion of the sheath to at least partially release.

[0226] Example 37: The method according to any example herein, particularly examples 32- 36, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the dilator shaft (for example, dilator shaft, tapered distal end, ridge, elongated body portion and/or a medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the tapered distal end through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration.

[0227] Example 38: The method according to any example herein, particularly examples 32- 37, further including: advancing the dilator shaft into the sheath until the dilator hub abuts a sheath hub coupled to a proximal end of the sheath.

[0228] Example 39: A method of inserting a medical device into a blood vessel of a patient, the method comprising: (1) inserting a radially expandable sheath at least partially into the blood vessel of a patient, the sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; (2) removing an introducer from the central lumen of the sheath; (3) introducing the dilator shaft into the central lumen of the sheath, the dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter of the dilator shaft; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; where a dilator hub is coupled to the proximal end of the dilator shaft; (4) advancing the tapered distal end through a portion of the central lumen of the sheath such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration; (5) removing the dilator shaft from the sheath; (6) introducing a medical device into a proximal end of the central lumen of the sheath; (7) advancing the medical device through the sheath; and (8) advancing the medical device beyond a distal opening in the sheath to a treatment site within the blood vessel.

[0229] Example 40: The method according to any example herein, particularly example 39, further including: inserting a guide wire at least partially into the blood vessel of a patient advancing the sheath over the guide wire through the blood vessel to the treatment site; and advancing the dilator shaft over the guide wire through the sheath to the treatment site. [0230] Example 41: The method according to any example herein, particularly examples 39- 40, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold. [0231] Example 42: The method according to any example herein, particularly examples 39- 41, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between the longitudinal edges of the overlapping portion and the underlying portion of the outer layer (for example, first edge and second edge), wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

[0232] Example 43: The method according to any example herein, particularly example 42, wherein the inner layer is bonded to the outer layer, wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes bonding along the portion of the sheath to at least partially release.

[0233] Example 44: The method according to any example herein, particularly examples 39- 43, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the dilator shaft (for example, dilator shaft, tapered distal end, ridge, elongated body portion and/or a medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the tapered distal end through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration. [0234] Example 45: The method according to any example herein, particularly examples 39- 44, wherein the medical device is a prosthetic device mounted in a radially crimped state on a delivery apparatus, wherein advancing the prosthetic device through the central lumen of the sheath comprises advancing the delivery apparatus and the prosthetic device through lumen of the sheath and into a vasculature of the patient.

[0235] Example 46: The method according to any example herein, particularly example 45, wherein the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient.

[0236] Example 47 : The method according to any example herein, particularly example 46, wherein the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the sheath.

[0237] Example 48: The method according to any example herein, particularly examples 39- 47, wherein the sheath is inserted into a femoral artery of the patient.

[0238] Example 49: A bi-directional dilator system including: a dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion (and/or the dilator shaft).

[0239] Example 50: The bi-directional dilator system according to any example herein, particularly example 49, wherein the diameter of the second dilating portion is greater than the diameter of the first dilating portion.

[0240] Example 51 : The bi-directional dilator system according to any example herein, particularly examples 49-50, wherein the first dilating portion is offset from the first tapered end such that a first body portion of the dilator shaft extends between the first tapered end and the first dilating portion, wherein the second dilating portion is offset from the second tapered end such that a second body portion of the dilator shaft extends between the second tapered end and the second dilating portion.

[0241] Example 52: The bi-directional dilator system according to any example herein, particularly example 51 , wherein a length of the first body portion corresponds with a length of the second body portion. [0242] Example 53: The bi-directional dilator system according to any example herein, particularly examples 51-52, wherein a diameter of the first body portion corresponds with a diameter of the second body portion, which corresponds with the diameter of the elongated body portion.

[0243] Example 54: The bi-directional dilator system according to any example herein, particularly examples 49-53, wherein: the first dilating portion includes: a leading tapered surface having an increasing taper extending from the first body portion in a direction towards the second end; a trailing tapered surface having a decreasing taper from the leading tapered surface to elongated body portion extending in a direction toward the first end; and an apex surface extending between the leading tapered surface and the trailing tapered surface, the apex surface having a diameter greater than the leading tapered surface and the trailing tapered surface; and the second dilating portion includes: a leading tapered surface having an increasing taper extending from the second body portion in a direction towards the first end; a trailing tapered surface having a decreasing taper from the leading tapered surface to the elongated body portion extending in a direction toward the first end; and an apex surface extending between the leading tapered surface and the trailing tapered surface, the apex surface having a diameter greater than the leading tapered surface and the trailing tapered surface.

[0244] Example 55: The bi-directional dilator system according to any example herein, particularly example 54, wherein the apex surface of the first dilating portion and the apex surface of the second dilating portion both define a generally cylindrical shape in cross section.

[0245] Example 56: The bi-directional dilator system according to any example herein, particularly examples 54-55, wherein an axial length of the apex surface of the first dilating portion corresponds with an axial length of the apex surface of the second dilating portion. [0246] Example 57: The bi-directional dilator system according to any example herein, particularly examples 54-56, wherein an axial length of the apex surface of the first dilating portion is greater than an axial length of the leading tapered surface and/or the trailing tapered surface of the first dilating portion, wherein an axial length of the apex surface of the second dilating portion is greater than an axial length of the trailing tapered surface and/or the leading tapered surface of the second dilating portion.

[0247] Example 58: The bi-directional dilator system according to any example herein, particularly examples 54-57, an axial length of the leading tapered surface of the first dilating portion is greater than an axial length of the trailing tapered surface of the first dilating portion, wherein an axial length of the leading tapered surface of the second dilating portion is greater than an axial length of the trailing tapered surface of the second dilating portion. [0248] Example 59: The bi-directional dilator system according to any example herein, particularly examples 54-58, wherein an angle of the leading tapered surface of the first dilating portion is less than an angle of the trailing tapered surface of the first dilating portion, wherein an angle of the leading tapered surface of the second dilating portion is less than an angle of the trailing tapered surface of the second dilating portion, wherein the angles of the leading and trailing tapered surfaces of each of the first and second dilating portions is measured between an outer surface of the dilator shaft and the corresponding leading and trailing tapered surfaces of each of the first and second dilating portions.

[0249] Example 60: The bi-directional dilator system according to any example herein, particularly examples 54-59, wherein an angle and a length of the leading tapered surface of the first dilating portion is symmetrical with an angle and a length of the trailing tapered surface of the first dilating portion about a midline of the apex surface of the first dilating portion, wherein an angle and a length of the leading tapered surface of the second dilating portion is symmetrical with an angle and a length of the trailing tapered surface of the second dilating portion about a midline of the apex surface of the second dilating portion.

[0250] Example 61: The bi-directional dilator system according to any example herein, particularly examples 54-60, wherein an angle and a length of the leading tapered surface of the first dilating portion is asymmetrical with an angle and a length of the trailing tapered surface of the first dilating portion about a midline of the apex surface of the first dilating portion, wherein an angle and a length of the leading tapered surface of the second dilating portion is asymmetrical with an angle and a length of the trailing tapered surface of the second dilating portion about a midline of the apex surface of the second dilating portion. [0251] Example 62: The bi-directional dilator system according to any example herein, particularly examples 49-61, wherein the first dilating portion and the second dilating portion are formed from the same material as the dilator shaft, (for example, all formed from PEK, LDP, HDP).

[0252] Example 63: The bi-directional dilator system according to any example herein, particularly examples 49-61, wherein the first dilating portion and the second dilating portion are formed from a different material as the dilator shaft.

[0253] Example 64: The bi-directional dilator system according to any example herein, particularly examples 49-63, wherein the first dilating portion and the second dilating portion are integrally formed with the dilator shaft. [0254] Example 65: The bi-directional dilator system according to any example herein, particularly examples 49-64, wherein the first dilating portion and the second dilating portion are coupled to the dilator shaft.

[0255] Example 66: The bi-directional dilator system according to any example herein, particularly examples 49-65, further including an adapter coupled to the dilator shaft providing a handle for the dilator shaft.

[0256] Example 67: The bi-directional dilator system according to any example herein, particularly example 66, wherein the adapter is sized and configured to coupled to at least one of the first dilating portion or the second dilating portion.

[0257] Example 68: The bi-directional dilator system according to any example herein, particularly examples 66-67, further including a radially expandable sheath and a sheath hub fixedly coupled to the proximal end of the sheath, wherein the adapter includes a coupling feature for releasable coupling to the sheath hub.

[0258] Example 69: A method of dilating a sheath comprising: (1) providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; (2) providing a dilator system for expanding at least a portion of the sheath, the dilator system including: the dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion, and the diameter of the second dilating portion is greater than the diameter of the first dilating portion, (3) introducing the dilator shaft (for example, the first tapered end or the second tapered end) into the central lumen of the sheath; (4) advancing the dilator shaft through a portion of the central lumen of the sheath such that at least one of the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration; and (5) removing the dilator shaft from the sheath.

[0259] Example 70: The method according to any example herein, particularly example 69, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer hy the first dilating portion or the second dilating portion (and/or the first tapered end, second tapered end, dilator shaft, and/or medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the first dilating portion or second dilating portion passes through the central lumen.

[0260] Example 71 : The method according to any example herein, particularly examples 69-

70, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

[0261] Example 72: The method according to any example herein, particularly examples 69-

71 , wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between the longitudinal edges of the overlapping portion and the underlying portion of the outer layer (for example, first edge and second edge), wherein advancing the dilator shaft through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

[0262] Example 73: The method according to any example herein, particularly example 72, wherein the inner layer is bonded to the outer layer, wherein advancing the dilator shaft (for example, the first tapered end or the second tapered end) through the portion of the central lumen of the sheath causes bonding along the portion of the sheath to at least partially release. [0263] Example 74: The method according to any example herein, particularly examples 69- 73, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the first dilating portion and/or the second dilating portion (for example, dilator shaft and/or a medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the first dilating portion and/or the second dilating portion through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the first dilating portion and/or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the first dilating portion and/or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration.

[0264] Example 75: A method of inserting a medical device into a blood vessel of a patient, the method comprising: (1) inserting a radially expandable sheath at least partially into the blood vessel of a patient, the sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; (2) removing an introducer from the central lumen of the sheath; (3) introducing the dilator shaft into the central lumen of the sheath, the dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion, and the diameter of the second dilating portion is greater than the diameter of the first dilating portion; (4) advancing the dilator shaft through a portion of the central lumen of the sheath such that at least one of the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration; (5) removing the dilator shaft from the sheath; (6) introducing a medical device into a proximal end of the central lumen of the sheath; (7) advancing the medical device through the sheath; and (8) advancing the medical device beyond a distal opening in the sheath to a treatment site within the blood vessel. [0265] Example 76: The method according to any example herein, particularly example 75, further including: inserting a guide wire at least partially into the blood vessel of a patient advancing the sheath over the guide wire through the blood vessel to the treatment site; and advancing the dilator shaft over the guide wire through the sheath to the treatment site.

[0266] Example 77: The method according to any example herein, particularly examples 75-

76, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

[0267] Example 78: The method according to any example herein, particularly examples 75-

77, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between the longitudinal edges of the overlapping portion and the underlying portion of the outer layer (for example, first edge and second edge), wherein advancing the first dilating portion or the second dilating portion through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

[0268] Example 79: The method according to any example herein, particularly example 78, wherein the inner layer is bonded to the outer layer, wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes bonding along the portion of the sheath to at least partially release. [0269] Example 80: The method according to any example herein, particularly example 75-

79, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the dilator shaft (for example, first dilating portion or the second dilating portion, and/or a medical device) against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the first dilating portion or the second dilating portion through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration.

[0270] Example 81: The method according to any example herein, particularly examples 75-

80, wherein the medical device is a prosthetic device mounted in a radially crimped state on a delivery apparatus, wherein advancing the prosthetic device through the central lumen of the sheath comprises advancing the delivery apparatus and the prosthetic device through lumen of the sheath and into a vasculature of the patient.

[0271] Example 82: The method according to any example herein, particularly example 81, wherein the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient.

[0272] Example 83: The method according to any example herein, particularly example 82, wherein the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the sheath.

[0273] Example 84: The method according to any example herein, particularly examples 75- 83, wherein the sheath is inserted into a femoral artery of the patient.

[0274] In view of the many possible aspects to which the principles of the disclosed disclosure can be applied, it should be recognized that the illustrated aspects are only preferred examples of the disclosure and should not be taken as limiting the scope of the disclosure. Rather, the scope of the disclosure is defined by the following claims. We, therefore, claim as our disclosure all that comes within the scope and spirit of these claims.

Claims

What is claimed:

1. A dilator system including: a dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter (Dmax) of the dilator shaft; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft.

2. The dilator system of any one of the previous claims, wherein the ridge includes: a leading tapered surface adjacent the distal end of the dilator shaft and having an increasing taper; and a trailing tapered surface extending between the leading tapered surface and the proximal end of the elongated body portion/dilator shaft, the trailing tapered surface having a decreasing taper, wherein the leading tapered surface and the trailing tapered surface meet at an apex of the ridge, the apex defining a maximum outer diameter (Dmax) of the dilator shaft.

3. The dilator system of claim 2, wherein the leading tapered surface extends along a length (LI) of the dilator shaft greater than a length (L2) the trailing tapered surface extends along the dilator shaft.

4. The dilator system of any one of the previous claims, wherein the outer surface of the tapered distal end extends at an increasing taper toward the elongated body portion of the dilator shaft, where the ridge is provided along the tapered outer surface.

5. The dilator system of claim 4, wherein the tapered distal end includes a nose portion extending between a distal end of the dilator shaft and the outer surface of the tapered distal end, where the nose portion has an outer diameter less than an outer diameter of the outer surface of the tapered distal end.

6. The dilator system of any one of the previous claims, wherein the dilator hub includes a central lumen extending between a proximal end and a distal end of the dilator hub, at least a portion of the central lumen defining a recessed opening for receiving the proximal end of the dilator shaft, the recessed opening extending from a distal end of the dilator hub towards the proximal end of the dilator hub.

7. The dilator system of claim 6, wherein the central lumen of the dilator hub includes a proximal recessed opening extending from the proximal end toward the distal end of the dilator hub, the proximal recessed opening separated from the recessed opening by a shoulder, wherein the central lumen of the dilator hub further includes an opening extending through the shoulder, wherein the proximal recessed opening includes a decreasing tapered portion defining a frustoconical shape with decreasing taper/diameter extending in a distal direction.

8. The dilator system of any one of claims 6-7, where an outer surface of the dilator hub includes a large diameter portion adjacent the distal end and a reduced diameter portion adjacent the proximal end, where the reduced diameter portion includes a coupling member.

9. The dilator system of any one of the previous claims, further including a sealing member provided between the proximal end of the dilator shaft and the and the dilator hub, the sealing member for maintaining a sealed connection between the central lumen of the dilator shaft and central lumen of the dilator hub, wherein the dilator hub includes a recessed opening for receiving a proximal end of the dilator shaft, the recessed opening extending from a distal end of the dilator hub towards the proximal end of the dilator hub, wherein the sealing member is provided between a proximal end surface of the recessed opening and the distal end surface of the dilator shaft.

10. A sheath system comprising: a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion; and a dilator system for expanding at least a portion of the sheath, the dilator system including: a dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end; and an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft; wherein at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration.

11. The sheath system of claim 10, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the ridge provided on the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the ridge passes through the lumen, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

12. The sheath system of any one of claims 10-11, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, as the sheath moves from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer moves circumferentially with respect to the underlying portion and the folded portion of the inner layer at least partially unfolds, wherein, in the expanded configuration, the outer layer includes a gap between longitudinal edges of the overlapping portion and the underlying portion of the outer layer.

13. The sheath system of claim 12, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, wherein at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the tapered distal end of the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the tapered distal end passes through the sheath.

14. A method of dilating a sheath comprising: providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; providing a dilator system for expanding at least a portion of the sheath, the dilator system including: the dilator shaft including: a tapered distal end including a ridge projecting from an outer surface of the tapered distal end, the ridge defining a maximum outer diameter of the dilator shaft; an elongated body portion extending between the tapered distal end and a proximal end and of the dilator shaft; and a dilator hub coupled to the proximal end of the dilator shaft; introducing the dilator shaft into the central lumen of the sheath; advancing the tapered distal end through a portion of the central lumen of the sheath such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration; and removing the dilator shaft from the sheath, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the ridge provided on the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the ridge passes through the central lumen, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

15. The method of claim 14, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between longitudinal edges of the overlapping portion and the underlying portion of the outer layer, wherein advancing the tapered distal end through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

16. The method of any one of claims 14-15, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the dilator shaft against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the tapered distal end through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the tapered distal end exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the tapered distal end to locally expand from the unexpanded configuration to the expanded configuration.

17. A bi-directional dilator system including: a dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion.

18. The bi-directional dilator system of claim 17, wherein the diameter of the second dilating portion is greater than the diameter of the first dilating portion, wherein the first dilating portion is offset from the first tapered end such that a first body portion of the dilator shaft extends between the first tapered end and the first dilating portion, wherein the second dilating portion is offset from the second tapered end such that a second body portion of the dilator shaft extends between the second tapered end and the second dilating portion.

19. The bi-directional dilator system of any one of claims 17-18, wherein: the first dilating portion includes: a leading tapered surface having an increasing taper extending from the first body portion in a direction towards the second end; a trailing tapered surface having a decreasing taper from the leading tapered surface to elongated body portion extending in a direction toward the first end; and an apex surface extending between the leading tapered surface and the trailing tapered surface, the apex surface having a diameter greater than the leading tapered surface and the trailing tapered surface; and the second dilating portion includes: a leading tapered surface having an increasing taper extending from the second body portion in a direction towards the first end; a trailing tapered surface having a decreasing taper from the leading tapered surface to the elongated body portion extending in a direction toward the first end; and an apex surface extending between the leading tapered surface and the trailing tapered surface, the apex surface having a diameter greater than the leading tapered surface and the trailing tapered surface.

20. The bi-directional dilator system any one of claims 17-19, wherein an axial length of the apex surface of the first dilating portion is greater than an axial length of the leading tapered surface and/or the trailing tapered surface of the first dilating portion, wherein an axial length of the apex surface of the second dilating portion is greater than an axial length of the trailing tapered surface and/or the leading tapered surface of the second dilating portion.

21. The bi-directional dilator system of any one of claims 17-20, further including an adapter coupled to the dilator shaft providing a handle for the dilator shaft, wherein the adapter is sized and configured to coupled to at least one of the first dilating portion or the second dilating portion.

22. A method of dilating a sheath comprising: providing a radially expandable sheath including: a continuous inner layer defining a central lumen extending therethrough, the inner layer having at least one folded portion, where at least a portion of the sheath is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by a dilator shaft received within the central lumen of the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft moves within the central lumen; providing a dilator system for expanding at least a portion of the sheath, the dilator system including: the dilator shaft having a first end and an opposing second end, a first tapered end provided adjacent the first end of the dilator shaft, and a second tapered end provided adjacent the second end of the dilator shaft; a first dilating portion adjacent the first tapered end; and a second dilating portion adjacent the second tapered end, where an elongated body portion of the dilator shaft extends between the first dilating portion and second dilating portion, wherein a diameter of the first dilating portion and a diameter of the second dilating portion is greater than a diameter of the elongated body portion, and the diameter of the second dilating portion is greater than the diameter of the first dilating portion, introducing the dilator shaft into the central lumen of the sheath; advancing the dilator shaft through a portion of the central lumen of the sheath such that at least one of the first dilating portion or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer proximate the first dilating portion or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration; and removing the dilator shaft from the sheath.

23. The method of claim 22, wherein the portion of the sheath is configured to locally expand from the unexpanded configuration in which the central lumen of the sheath has a first diameter to the expanded configuration in which the central lumen has a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the first dilating portion or the second dilating portion against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the first dilating portion or second dilating portion passes through the central lumen, wherein locally expanding the portion of the sheath causes the at least one folded portion of the inner layer to at least partially unfold.

24. The method of any one of claims 22-23, wherein the sheath further includes: a discontinuous outer layer provided over the inner layer, where the outer layer is discontinuous and includes an overlapping portion and an underlying portion, wherein, in the unexpanded configuration, the overlapping portion overlaps the underlying portion with the folded portion of the inner layer disposed between the overlapping portion and the underlying portion, wherein, in the expanded configuration, the outer layer includes a gap between longitudinal edges of the overlapping portion and the underlying portion of the outer layer, wherein advancing the dilator shaft through the portion of the central lumen of the sheath causes the portion of the sheath to move from the unexpanded configuration to the expanded configuration, the overlapping portion of the outer layer to move circumferentially with respect to the underlying portion, and the folded portion of the inner layer at least partially unfolds.

25. The method of any one of claims 22-24, wherein the sheath further includes: a tubular strain relief layer positioned at a proximal end of the sheath for limiting radial expansion of the sheath, the strain relief layer provided along the inner layer and extending at least partially over the outer layer, at least a portion of the strain relief layer is configured to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter, and then locally contract at least partially back to the unexpanded configuration in response to an outwardly directed radial force exerted on the central lumen of the inner layer by the first dilating portion and/or the second dilating portion against the inner layer, and then locally contract at least partially back to the unexpanded configuration as the dilator shaft passes through the sheath, wherein the method further includes: advancing the first dilating portion and/or the second dilating portion through a portion of the central lumen of the sheath corresponding to the strain relief layer such that the first dilating portion and/or the second dilating portion exerts an outwardly directed radial force against the central lumen and causes the inner layer and the strain relief layer proximate the first dilating portion and/or the second dilating portion to locally expand from the unexpanded configuration to the expanded configuration.