WO2023192800A1

WO2023192800A1 - Enhanced polymer liner for catheter

Info

Publication number: WO2023192800A1
Application number: PCT/US2023/064891
Authority: WO
Inventors: Cormac O’KEEFFE; Chloe BOWEN
Original assignee: Stryker European Operations Ltd; Stryker Corp
Current assignee: Stryker European Operations Ltd; Stryker Corp
Priority date: 2022-03-29
Filing date: 2023-03-23
Publication date: 2023-10-05
Anticipated expiration: 2024-09-29

Abstract

An intravascular catheter comprises an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body. The intravascular catheter further comprises an inner polymer liner disposed within the tubular body lumen, the inner polymer liner having an elongated seamless polymer tube with a proximal section composed of polytetrafluoroethylene (PTFE) and a distal section composed of expanded polytetrafluoroethylene (ePTFE), and a liner lumen extending through the polymer tube.

Description

ENHANCED POLYMER LINER FOR CATHETER

FIELD

[1] The present disclosure relates generally to medical devices, and, more particularly, to polymer liners for medical catheters.

BACKGROUND

[2] The use of intravascular catheters for accessing and treating various types of diseases, such as vascular defects, is well-known. For example, a suitable intravascular catheter may be inserted into the vascular system of a patient. A commonly used vascular application to access a target site in a patient involves inserting a guidewire through an incision in the femoral artery near the groin, and advancing the guidewire until it reaches the target site. Then, a catheter is advanced over the guidewire via a lumen in the catheter until an open distal end of the catheter is disposed at the target site. Simultaneously or after placement of the distal end of the catheter at the target site, an intravascular implant is advanced through the lumen of the catheter via a delivery wire.

[3] In certain applications, such as neurovascular treatment, the catheters are required to navigate tortuous and intricate vasculature. By using an appropriately sized device having the requisite performance characteristics, such as “pushability,” “steerability,” and “torqueability,” and most important, distal tip flexibility, virtually any target site in the vascular system may be accessed, including that within the tortuous cerebral and peripheral vasculature. The forces applied at the proximal end of these catheters should be transferred to the distal ends for suitably pushability (axial rigidity) and torqueability (rotation). Achieving a balance between these features is highly desirable, but difficult.

[4] Presently, there are numerous microcatheter designs with hypotubes that achieve this balance. In general, a hypotube is a long thin-walled tube formed from a metal or a metal alloy, such stainless steel, nickel titanium alloy (e.g., nitinol), rigid plastics, or the like. A hypotube often has micro-engineered features along its length. The distal end of a hypotube may have a slotted pattern that enhances its flexibility, while providing sufficient axial rigidity to maintain the pushability of the hypotube through the vasculature of a patient. In some instances, a polymer jacket may be applied to the outer diameter of the slotted hypotube to provide a seal and to also minimize any exterior surface roughness imparted by the slots of the hypotube while still providing flexibility. This outer jacket may fill the aperture/slots in the hypotube, and even coat the internal surface of the hypotube.

[5] For applications, such as applications of neurovascular treatment, that involve passing various other devices, agents, and/or fluids into a body lumen or cavity in a patient by the catheter, the properties of the inner surface of the lumen(s) of the catheter may significantly impact the performance of the catheter. In particular, the lubricity of the inner surface may affect the ability to pass other devices, agents, and/or fluids through the lumen(s) of the catheter.

[6] To enhance lubricity, a low friction inner polymer liner (e.g., polytetrafluoroethylene (PTFE)) can surround the lumen of a catheter. The inner polymer liner may provide a lubricious inner surface to facilitate passing guidewires, pacing leads, or other devices through the lumen of the catheter. Such a liner may be slightly undersized so that it slides inside the slotted hypotube during manufacturing. In other examples, the slotted hypotube tube may have a reinforcement that may give the inner polymer liner more support and integrity as the catheter navigates the vasculature to a treatment location. Examples of inner polymer liners are described in U.S. Patent Nos. 10,953,193 and 6,622,367, and PCT Publication WO2021/025814. To prevent delamination between the inner liner and the hypotube structure, a tie layer in the form of an ultrathin thermoplastic coating may be applied over an inner polymer liner during catheter construction. This tie layer creates a melt-bondable substrate that improves adhesion to both the inner polymer liner and the hypotube structure of the catheter. Alternately, another form of adhesive could be used, such as a liquid, dispersion, or solid.

[7] PTFE liners, even those with minimal wall thickness, contribute significantly to the overall stiffness of the distal sections of intravascular catheters containing slotted hypotubes, thereby impacting the distal navigability of catheters. In particular, in a slotted hypotube structure 1 comprising a pattern of apertures (e.g., slots) 2 and solid elements (e.g., struts) 4 illustrated in Fig. 1 , flexibility requires that apertures 2 in the hypotube structure 1 be free to open or close in response to a bending force. If an inner polymer liner 4 is intimately and continuously coupled with the inner surface of the solid elements 3 of the hypotube structure 1 via a tie layer 5, then the inner polymer liner 4 must stretch to allow the apertures 2 to open. This can require a relatively high percentage of elongation, as only the polymer spanning an aperture 2 is available to stretch. In distal regions of the slotted hypotube catheter, the inner polymer liner is by far the dominant element in terms of stiffness.

[8] Not only does the intimate/continuous coupling between an inner polymer liner and the hypotube structure detrimentally affect the flexibility of the distal region of the slotted hypotube catheter, past experience has shown that it has a detrimental effect on the torque transmission and navigability of the catheter structure. In particular, due to the relatively high strain required to bend the distal region of the slotted hypotube catheter, the inner polymer liner may plastically deform, thereby creating a permanent bend in the distal region of the catheter. Torquing of the deformed catheter may cause the distal end of the catheter to whip, thereby detrimentally affecting the steerability of the catheter.

[9] Although PTFE has a high stiffness profile, expanded PTFE (ePTFE) provides a potential solution for improving liners by introducing anisotropic properties of high tensile stretch, but reduced flexural modulus. An example of using ePTFE for producing tubular structures is described in U.S. Patent Publication No. 2009/0048657A1. The resulting properties of ePTFE provide lower distal stiffness, while retaining stretch resistance, thereby enhancing distal navigability of catheters. However, manufacturing liners composed of ePTFE can be prohibitively expensive.

[10] There, thus, is an ongoing need for a cost-effective inner polymer liner without unduly increasing the bending stiffness at the distal end of the resulting catheter.

SUMMARY

[11] In accordance with first aspect of the present inventions, an intravascular catheter comprises an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body. In one embodiment, the tubular body is a hypotube structure. For example, the hypotube structure may have a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

[12] The intravascular catheter further comprises an inner polymer liner disposed within the tubular body lumen. The inner polymer liner has an elongated seamless polymer tube with a proximal section composed of polytetrafluoroethylene (PTFE) and a distal section composed of expanded polytetrafluoroethylene (ePTFE), and a liner lumen extending through the polymer tube. If the tubular body is a hypotube structure, the distal section of the seamless polymer tube may span the hypotube pattern of the hypotube structure.

[13] In one embodiment, the intravascular catheter further comprises an outer polymer jacket disposed on an exterior surface of the tubular body. In another embodiment, the tubular body is an outer polymer jacket. In steal another embodiment, the intravascular catheter further comprises a tie layer attaching the inner polymer liner to the tubular body.

[14] In accordance with a second aspect of the present inventions, an intravascular catheter comprises an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body. In one embodiment, the tubular body is a hypotube structure. For example, the hypotube structure may have a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

[15] The intravascular catheter further comprises an inner polymer liner disposed within the tubular body lumen, the inner polymer liner having an elongated seamless polymer tube with a proximal section having a first density and a distal section having a second density less than the first density, and a liner lumen extending through the seamless polymer tube. In one embodiment, the distal section of the seamless polymer tube has a microporous structure. The microporous structure may, e.g., have fibrils and may or may not have nodes. In another embodiment, the proximal section of the seamless polymer tube has a first flexural stiffness, and the distal section of the seamless polymer tube has a second flexural stiffness less than the first flexural stiffness. In still another embodiment, the proximal end of the seamless polymer tube is composed of polytetrafluoroethylene (PTFE), and the distal end of the seamless polymer tube is composed of expanded polytetrafluoroethylene (ePTFE). If the tubular body is a hypotube structure, the distal section of the seamless polymer tube may span the hypotube pattern of the hypotube structure.

[16] In one embodiment, the intravascular catheter further comprises an outer polymer jacket disposed on an exterior surface of the tubular body. In another embodiment, the tubular body is an outer polymer jacket. In still another embodiment, the intravascular catheter further comprises a tie layer attaching the inner polymer liner to the tubular body. [17] In accordance with a third aspect of the present inventions, a method of manufacturing an intravascular catheter comprises providing an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body. In one method, the tubular body is a hypotube structure. For example, the hypotube structure may have a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

[18] The method further comprises providing a polymer tube having a proximal section, a distal section, and a tube lumen extending through the polymer tube. The proximal section and distal section of the polymer tube are composed of polytetrafluoroethylene (PTFE). In one method providing the polymer tube comprises selecting a PTFE resin and extruding the polymer tube from the PTFE resin.

[19] The method further comprises converting the distal section of the polymer tube from PTFE to expanded polytetrafluoroethylene (ePTFE), while the proximal section remains PTFE. In one method, transforming the distal section of the polymer tube from PTFE to ePTFE may comprise locally expanding the distal section of the polymer tube (e.g., by stretching the distal section of the polymer tube) at an elevated temperature (e.g., in the range of 500°F-700°F). The method may further comprise decreasing the length of the polymer tube by removing an end of the distal section of the polymer tube from the polymer tube.

[20] The method further comprises affixing the polymer tube within the tubular body lumen. Affixing the polymer tube within the tubular body lumen may comprise radially expanding the polymer tube within the tubular body lumen. If the tubular body is a hypotube structure, the polymer tube may be affixed within the tubular body lumen, such that the distal section of the polymer tube spans the hypotube pattern.

[21] One method further comprises affixing an outer polymer jacket on an exterior surface of the hypotube structure. In another method, the elongate tubular body is an outer polymer jacket.

[22] In accordance with a fourth aspect of the present inventions, a method of manufacturing an intravascular catheter comprises providing an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body. In one method, the tubular body is a hypotube structure. For example, the hypotube structure may have a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

[23] The method further comprises providing a polymer tube having a proximal section, a distal section, and a tube lumen extending through the polymer tube. The proximal section and distal section of the polymer tube are composed of polytetrafluoroethylene (PTFE). In one method providing the polymer tube comprises selecting a PTFE resin and extruding the polymer tube from the PTFE resin.

[24] The method further comprises locally expanding the distal section of the polymer tube (e.g., by stretching the distal section of the polymer tube) at an elevated temperature (e.g., in the range of 500°F-700°F), such that the distal section of the polymer tube is composed of a microporous structure, while the proximal section of the polymer is not composed of the microporous structure. The microporous structure may, e.g., have fibrils and may or may not have nodes. The microporous structure may, e.g., have fibrils and may or may not have nodes. The method may further comprise decreasing the length of the polymer tube by removing an end of the distal section of the polymer tube from the polymer tube.

[25] The method further comprises affixing the polymer tube within the tubular body lumen. Affixing the polymer tube within the tubular body lumen may comprise radially expanding the polymer tube within the tubular body lumen. If the tubular body is a hypotube structure, the polymer tube may be affixed within the tubular body lumen, such that the distal section of the polymer tube spans the hypotube pattern.

[26] One method further comprises affixing an outer polymer jacket on an exterior surface of the hypotube structure. In another method, the elongate tubular body is an outer polymer jacket.

[27] Other and further aspects and features of embodiments will become apparent from the ensuing detailed description in view of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[28] The drawings illustrate the design and utility of preferred embodiments of the disclosed inventions, in which similar elements are referred to by common reference numerals. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention, which is defined only by the appended claims and their equivalents. In addition, an illustrated embodiment of the disclosed inventions needs not have all the aspects or advantages shown. Further, an aspect or an advantage described in conjunction with a particular embodiment of the disclosed inventions is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated.

[29] In order to better appreciate how the above-recited and other advantages and objects of the disclosed inventions are obtained, a more particular description of the disclosed inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[30] Fig. 1 is a longitudinal-sectional view of a prior art slotted hypotube structure;

[31] Fig. 2 is a profile view of one embodiment of an intravascular catheter, particularly showing a distal end of the intravascular catheter in a straight geometry;

[32] Fig. 3 is a profile view of the intravascular catheter of Fig. 2, particularly showing the distal end of the intravascular catheter in a curved geometry

[33] Fig. 4 is a profile view of the distal end of one embodiment of a hypotube structure used in the intravascular catheter of Fig. 2;

[34] Fig. 5 is a perspective view of the distal end of the hypotube structure of Fig. 4;

[35] Fig. 6 is a cross-sectional view of the distal end of one embodiment of a catheter body of the intravascular catheter of Fig. 2;

[36] Fig. 7 is a longitudinal-sectional view of the distal end of the catheter body of Fig. 6, particularly showing one embodiment of a tie layer;

[37] Fig. 8 is a perspective view of the distal end of another embodiment of a hypotube structure used in the catheter body of Fig. 6; [38] Fig. 9 is a perspective view of one embodiment of an inner polymer liner used in the catheter body of Fig. 6;

[39] Fig. 10 is a longitudinal-sectional view of the distal end of the catheter body of Fig. 6, particularly showing another embodiment of a tie layer;

[40] Fig. 11 is a flow diagram illustrating one method of manufacturing the intravascular catheter of Fig. 2;

[41] Fig. 12 is a perspective view of one tubular body used to make the hypotube structure in accordance with the flow diagram of Fig. 11 ;

[42] Fig. 13 is a perspective view of a pattern of apertures and solid elements formed on the distal end of the tubular body of Fig. 12 to create a hypotube structure;

[43] Fig. 14 is a perspective view of one polymer tube used to make the inner liner in accordance with the flow diagram of Fig. 11 ;

[44] Fig. 15 is a perspective view of the polymer tube of Fig. 14, particularly showing the treatment of the distal section of the polymer tube in accordance with the flow diagram of Fig. 11 ;

[45] Fig. 16 is a perspective view of the treated polymer tube of Fig. 15, particularly showing removal of the end of the distal section of the polymer tube in accordance with the flow diagram of Fig. 11 ;

[46] Fig. 17 is a perspective view of the polymer tube of Fig. 16 disposed in the inner lumen of the hypotube structure of Fig. 13 in accordance with the flow diagram of Fig. 11 ;

[47] Fig. 18 is a perspective view of the polymer tube intermittently attached to the hypotube structure via a plurality of discrete adhesion regions in accordance with the flow diagram of Fig. 11 ;

[48] Fig. 19 is a plan view of one embodiment of a microporous structure of fibrils and nodes within the distal section of the treated polymer tube of Fig. 15; and

[49] Figs. 20A and 20B are plan views of alternative embodiments of microporous structures of fibrils within the distal section of the treated polymer tube of Fig. 15

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[50] Referring to Figs. 2 and 3, one embodiment of an intravascular catheter 10 will now be described. The intravascular catheter 10 has a tubular configuration, and can, e.g., take the form of a micro-catheter, a sheath, or the like. In the illustrated embodiment, the intravascular catheter 10 serves as a delivery catheter for delivering a vaso-occlusive device 12 into an aneurysm, although alternative embodiments of the intravascular catheter 10 may deliver other medical devices, e.g., another catheter, a guide member, a stent, a thrombectomy device, etc. Furthermore, other alternative embodiments of the intravascular catheter 10 may serve as a working catheter, e.g., a treatment catheter or diagnostic catheter. A pusher member 14 is detachably coupled to the vaso-occlusive device 12 via a junction 16 (e.g., mechanical, thermal, and hydraulic mechanisms). Thus, the pusher member 14 can be distally advanced to deploy the vaso-occlusive device 12 from the intravascular catheter 10 into an aneurysm (not shown) and selectively detached from the pusher member 14 via action of the junction 16 to deliver the vaso-occlusive device 12 within the aneurysm.

[51] The intravascular catheter 10 generally comprises an elongated catheter body 18 topologically divided between a proximal catheter body section 20 and a distal catheter body section 22, an inner catheter lumen 24 extending within the catheter body 18 from the proximal catheter body section 20 to the distal catheter body section 22, and a proximal catheter hub 26 affixed to the proximal catheter body section 20.

[52] The proximal catheter body section 20 remains outside of the patient and accessible to the operator, while the distal catheter body section 22 is sized and dimensioned to reach remote locations of the vasculature of the patient, and is configured to deliver the vaso-occlusive device 12 to the aneurysm (not shown). The distal catheter body section 22 is more flexible than the proximal catheter body section 20, so that it can transition between a straight configuration (Fig. 2) and a curved configuration (Fig. 3). Generally, the proximal catheter body section 20 may be formed from material that is stiffer than the distal catheter body section 22, so that the proximal catheter body section 20 has sufficient pushability to advance through the patient’s vascular system, while the distal catheter body section 22 may be formed of a more flexible material so that the distal catheter body section 22 may remain flexible and track more easily over a guidewire to access remote locations in tortuous regions of the vasculature. In some instances, the proximal catheter body section 20 may include a reinforcement layer, such a braided layer or coiled layer to enhance the pushability of the catheter body 18. The catheter body 18 may optionally comprise an intermediate catheter body section (not shown) that may gradually transition the relatively high bending stiffness of the proximal catheter body section 20 to the relatively low bending stiffness of the distal catheter body section 22. A distal tip 28 of the distal catheter body section 22 may be rounded to minimize the chance of traumatic piercing of body tissue. The intravascular catheter 12 comprises a distal port 30 at the distal tip 28 in communication with the inner catheter lumen 24 and from which the vaso-occlusive device 16 is deployed.

[53] The catheter body 18 has a suitable length for accessing a target tissue site within the patient from a vascular access point. The target tissue site depends on the medical procedure for which the intravascular catheter 10 is used. For example, if the intravascular catheter 10 is used to access vasculature in a brain of a patient from a femoral artery access point at the groin of the patient, the overall length of the catheter body 18 may be 125cm-200cm. In one embodiment, the outer diameter of the catheter body 18 may be uniform along the length of the catheter body 18. In another embodiment, the outer diameter of the catheter body 18 may taper in either a gradual fashion or a step-wise fashion from a first outer diameter of the proximal catheter body section 20 to a second outer diameter at the distal catheter body section 22.

[54] The outer diameter of the catheter body 18 may be in the range of 3F-1 OF. The distal catheter body section 22 may have an outer diameter less than the outer diameter of the proximal catheter body section 20 to reduce the profile of the distal catheter body section 22 and facilitate navigation in tortuous vasculature. Although depicted as having a generally round cross-sectional shape, it can be appreciated that the intravascular catheter 10 can include other cross-sectional shapes or combinations of shapes, e.g., oval, rectangular, triangular, polygonal, and the like. The catheter body 18 is structurally configured for being relatively flexible, pushable, and relatively kink- and buckle-resistant, so that it may resist buckling when a pushing force is applied to the proximal catheter body section 20 to advance the catheter body 18 distally through the vasculature of the patient, and so that it may resist kinking when traversing around a tight turn in the vasculature. The catheter body 18 may be relatively thin-walled, such that it defines a relatively large inner diameter for a given outer diameter, which may further contribute to the flexibility and kink-resistance of the catheter body 18. [55] In some embodiments, at least a portion of the outer surface of the catheter body 18 includes one or more coatings, such as, e.g., an anti-thrombogenic coating, which may help reduce the formation of thrombi in vitro, an anti-microbial coating, or a lubricating coating (e.g., a hydrophilic coating), which may reduce static friction or kinetic friction between the catheter body 18 and tissue of the patient as the catheter body 18 is advanced through the vasculature or through another catheter.

[56] The diameter of the inner catheter lumen 24 may vary based on the medical procedure for which the intravascular catheter 10 is used, and in the illustrated embodiment, is sized to accommodate the vaso-occlusive device 16. The diameter of the inner catheter lumen 24 may be substantially constant from the proximal catheter body section 20 to the distal catheter body section 22 or may taper from a first diameter at the proximal catheter body section 20 to a second different diameter at the distal catheter body section 22.

[57] The proximal catheter hub 26 may be affixed to the proximal catheter body section 20 using suitable means, e.g., adhesive, welding, etc. The proximal catheter hub 26 comprises a proximal port 32 through which the inner catheter lumen 24 may be accessed, and in some embodiments, closed. For example, the proximal port 32 may be located at a proximal end of the proximal catheter hub 26 and aligned with the inner catheter lumen 24, such that the inner catheter lumen 24 may be accessed via the proximal port 34. In this case, the vaso-occlusive device 12 with the pusher member 14 may be introduced into the inner catheter lumen 24 via the proximal port 34 of the catheter hub 26. The proximal catheter hub 26 may further comprises a side port 36 in fluid communication with the inner catheter lumen 24, which is used to introduce fluids into the catheter body 18. In some embodiments, another structure (not shown) in addition to, or instead of, the proximal catheter hub 26 may be affixed to the proximal catheter body section 20.

[58] Referring now to Figs. 4-7, the catheter body 18 of the intravascular catheter 10 generally comprises a hypotube structure 38, an inner polymer liner 40 (shown in Fig. 6-7) disposed within the hypotube structure 38, and a tie layer 42 (shown in Figs. 6-7) that attaches the inner polymer liner 40 to the hypotube structure 38.

[59] The hypotube structure 38 comprises an elongate tubular body 44 with a proximal end 46 and a distal end 48, a hypotube pattern 50 of apertures 50a and solid elements 50b formed on the distal end 48 of the tubular body 44, and an inner hypotube lumen 52 extending between the proximal end 46 and the distal end 48 of the tubular body 44. The tubular body 44 may be composed of any of a variety of suitable materials, e.g., a material that is rigid, but has some flexibility when used to form extremely thin structures, such as the wall of the tubular body 44. Examples of such materials include metals (e.g., stainless steel, such as 304 stainless steel, 316 stainless steel, 316L stainless steel, nickel chromium (NiCr) steel, nickel titanium alloy (e.g., nitinol), cobalt/chromium), or various plastics. The dimensions of the tubular body 44 may be suitable for one or more desired uses of the intravascular catheter 10. As examples, the outer diameter of the tubular body 44 may be in the range of 0.005-0.080 inches. The inner diameter of the tubular body 44 (i.e., the diameter of the inner hypotube lumen 52) may be in the range of 0.002-0.070 inches.

[60] In the illustrated embodiment, the hypotube pattern 50 takes the form of a brick pattern, and the apertures 50a take the form of slots, and the solid elements 50b take the form of struts. In an alternative embodiment illustrated in Fig. 8, a hypotube pattern 50’ formed on the distal end 48 of the tubular body 44 may have apertures in form of slits 50a’ (which may be oriented circumferentially (perpendicular to the longitudinal axis of the tubular body 44) or helically (at an oblique angle to the longitudinal axis of the tubular body 44), and solid elements in the form of spines 50b’ formed between the slits 50a’.

[61] The hypotube pattern 50 or hypotube pattern 50’ may formed in the distal end 48 of the tubular body 44 by laser cutting, saw cutting (e.g., diamond grit embedded semiconductor dicing blade), etching, waterjet cutting, or electrical discharge machining, among other methods.

[62] In the illustrated embodiment, the hypotube pattern 50 of apertures 50a and solid elements 50b (or hypotube pattern 50’ of apertures 50a’ and solid elements 50b’) are arranged to enhance the bending flexibility of the distal end of the intravascular catheter 10, while maintaining the axial rigidity (pushability) and torqueability of the intravascular catheter 10, such that the intravascular catheter 10 may be introduced and advanced through the tortuous vasculature of a patient. By controlling and varying the spacing, width, and shape of apertures 50a, the bending flexure profile and torsional stiffness of the hypotube structure 38, and thus the distal catheter body section 22 (see Figs. 2 and 3) may be selectively modified. [63] Although the catheter body 18 has been described as having a hypotube structure, it should be appreciated that other types of elongated tubular bodies can be used, e.g., those having coiled, braided, or hybrid designs.

[64] As shown in Figs. 6-7, the inner polymer liner 40 is disposed within the inner hypotube lumen 52. As further shown in Fig. 9, the inner polymer liner 40 comprises an elongate polymer tube 54 with a proximal section 58 and a distal section 60, and an inner liner lumen 56 extending through the polymer tube 54. The inner surface of the polymer tube 54 may be lubricious to facilitate the passage of a medical device (e.g., another catheter, a guide member, an embolic protection device, a stent, a thrombectomy device, or any combination thereof) through the inner liner lumen 56. For example, the material from which the entire polymer tube 54 is formed may be lubricious. Preferably, the length of the distal section 60 of the polymer tube 54 spans the hypotube pattern 50 of the hypotube structure 38.

[65] Significantly, the flexural stiffness of the proximal section 58 of the polymer tube 54 is greater than the flexural stiffness of the distal section 60 of the polymer tube 54. In this manner, the decreased flexural stiffness of the distal section 60 of the polymer tube 54 improves the navigability of the catheter body 18 through the vasculature of the patient. Despite the different mechanical properties of the proximal section 58 and distal section 60 of the polymer tube 54, the polymer tube 54 has a seamless design or structure, meaning that the proximal section 58 and distal section 60 of the polymer tube 54, when solid, are not joined together via bonding, but rather are formed together as a single component. In this manner, not only is the fabrication process of the polymer tube 54 easier and more cost-efficient, the reliability of the resulting catheter body 18 is increased. That is, in contrast to a process that involves the extra step of butt bonding two polymer tubes together to form a single polymer tube, which may increase the chance of a delamination event between the inner polymer liner and the hypotube structure 38, the proximal section 58 and distal section 60 of the polymer tube 54 are formed without any joints therebetween, e.g., as a single piece in an extrusion process or dip coating/case film process.

[66] In one embodiment, the different flexural stiffnesses for the proximal section 58 and distal section 60 in a seamless design of the polymer tube 54 may be achieved by forming the polymer tube 54 from the same base polymeric material, but with different densities. That is, the density of the proximal section 58 of the polymer tube 54 is greater than the density of the distal section 60 of the polymer tube 54. As one example, the proximal section 58 of the polymer tube 54 may be composed of polytetrafluoroethylene (PTFE), while the distal section 60 of the polymer tube 54 may be composed of expanded polytetrafluoroethylene (ePTFE). In this example, not only does the distal section 60 of the polymer tube 54 exhibit less flexural stiffness than the proximal section 58 of the polymer tube 54, thereby improving the navigability of the catheter body 18 through the vasculature of the patient, the tensile strength of the distal section 60 of the polymer tube 54 (e.g., in the range of 50- 800MPa for ePTFE) will be greater than the tensile strength of the proximal section 58 of the polymer tube 54 (e.g., in the range of 20-35MPa for PTFE), which will facilitate deployment of stents from the intravascular catheter 10. In other examples, the seamless polymer tube 54 may be composed of other base materials (e.g., fluoropolymer, perfluoroalkyoxy, alkane (PFA), fluorinated ethylene polyethylene (FEP), polyethylene (PE), as long as the flexural stiffness/density of the proximal section 58 is greater than the flexural stiffness/density of the distal section 60 of the polymer tube 54. In the illustrated embodiment, the flexural stiffness/density is uniform along the length of the proximal section 58 of the polymer tube 54, and the flexural stiffness/density is uniform along the length of the distal section 60 of the polymer tube 54. In alternative embodiments, the flexural stiffness/density may vary (continuously or discretely) along the length of the proximal section 58 of the polymer tube 54, and/or the flexural stiffness/density may vary (continuously or discretely) along the length of the distal section 60 of the polymer tube 54, as long as the average flexural stiffness/density of the proximal section 58 is greater than the average flexural stiffness/density of the distal section 60 of the polymer tube 54. A novel method of manufacturing such a polymer tube 54 will be described in further detail below.

[67] In the preferred embodiment, the tubular body 54 is unreinforced (meaning that there are no metallic elements disposed within the wall of the tubular body 54 that function to increase the radial strength of the tubular body 54), thereby minimizing any bending stiffness imparted by the inner polymer liner 40 onto the distal catheter body section 22 (see Fig. 3). As will be described in further detail below, because the tubular body 54 is unreinforced, it may be expanded within the inner hypotube lumen 52 of the hypotube structure 38, thereby reducing the wall thickness of the tubular body 54, and ensuring that there is continuous intimate contact (but not continuous coupling) between the tubular body 54 and the inner hypotube lumen 52 of the hypotube structure 38 (i.e., the hypotube structure 38 is in contact with the entirety of all solid elements of the hypotube structure 38).

[68] The wall thickness of the distal end 60 of the tubular body 54 may be equal to or less than 001”. In some embodiments, the wall thickness of the tubular body 54 is substantially constant along a length of the tubular body 54. In other embodiments, the wall thickness of the tubular body 54 may decrease toward the distal end 50 (e g., the thickness of the tubular body 54 may decrease from the proximal end 48 to the distal end 50 of the tubular body 54). The inner diameter of the tubular body 54 (i.e., the diameter of the inner liner lumen 56) may be substantially constant along the entire length of the tubular body 54. In other embodiments, the inner diameter of the tubular body 54 may be vary, e.g., may taper continuously from the proximal end 48 to the distal end 50 of the tubular body 54 or in may vary in a step-wise fashion. In an optional embodiment, the inner polymer liner 40 may have a pattern of apertures (e.g., slots or slits) and solid elements (e.g., struts or ribs) (not shown) to enhance the bending flexibility of the distal catheter body section 22, e.g., as described in U.S. Patent Publication No. 2020/0129733, which is expressly incorporated herein by reference.

[69] The tie layer 42 may be composed of a suitable material, e.g., polyurethane (e.g., Tecoflex™), Pebax®, and nylon. The tie layer 42 may have of a thickness of no more than about 0.005 inches, and in some implementations, approximately 0.001 inches, and perhaps even less than 0.0001 inches. The tie layer 42 may generally extend along at least along a range of 10-20cm of the distal catheter body section 22, and generally less than about 50cm along the length of the catheter body 18. In an optional embodiment, the bending stiffness of the distal catheter body section 22 (shown in Fig. 3) may be reduced through selective application (or removal) of material that forms the tie layer 42, so that a certain distal length of the inner polymer liner 40 is not continuously attached to the hypotube structure 12. In this manner, the navigability of the catheter body 18 through the vasculature of the patient may be improved.

[70] In particular, a tie layer 42’ may have tie layer pattern 62 of apertures 62a and solid elements 62b that is complementary to the hypotube pattern 50, such that the tie layer 42’ intermittently attaches the inner polymer liner 40 to the solid elements 50b of the hypotube structure 38 along a length of the hypotube pattern 50, as illustrated in Fig. 10. As a result, at least one discrete adhesion region 64 is formed between the hypotube structure 38 and the inner polymer liner 40, and at least one non-adhesion region 66 is formed between the hypotube structure 38 and the inner polymer liner 40. In the illustrated embodiment, the tie layer pattern 62 is complementary to the hypotube pattern 50, such that several discrete adhesion regions 64 are formed between the hypotube structure 38 and the inner polymer liner 40, and several non-adhesion regions 66 are formed between the hypotube structure 38 and the inner polymer liner 40. Further details of tie layers that intermittently attach inner polymer liners to hypotube structures are set forth in U.S. Provisional Application Ser. No. 63/278,463, entitled “Patterned Tie Layer for Catheter Performance Optimization,” which is expressly incorporated herein by reference.

[71] Having described the structure and arrangement of the intravascular catheter 10, one exemplary method 100 of manufacturing the intravascular catheter 10 will now be described with respect to Fig. 11.

[72] The method 100 initially comprises providing a tubular body 202 having a proximal end 204, a distal end 206, and a lumen 208 extending between the proximal end 204 and the distal end 206 (see Fig. 12) (step 102), and forming a pattern 210 of apertures 212 (e.g., slots) and solid elements 214 (e.g., struts) on the distal end 206 of the tubular body 202, e.g., by laser cutting, saw cutting (e.g., diamond grit embedded semiconductor dicing blade), etching, waterjet cutting, or electrical discharge machining, among other methods) (see Fig. 13) (step 104), thereby creating the hypotube structure 200.

[73] The method 100 further comprises providing a “green” polymer tube 216 having a proximal section 218, a distal section 220, and a lumen 222 (see Fig. 14) (step 106). For example, the method 100 may comprise selecting a polymeric resin for the green polymer tube 216, molding the selected polymeric resin under high pressure to form a billet, which may be cylindrical, extruding the green polymer tube 216 from the billet, and then sintering the green polymer tube 216. The density of the green polymer tube 216 may be controlled by selecting the size of resin particles used in the extrusion process and/or pressure applied during the extrusion process. The density of the green polymer tube 216 may be increased in inverse proportion to the size of the resin particles (i.e., the smaller the size of the resin particles, the more dense the material in the extruded polymer tube) and/or in proportion to the pressure applied during the extrusion process. In one embodiment, the polymeric resin is selected to be unetched, unsintered, fine PTFE resin. Alternatively, other types of polymeric resin may be selected, e.g., fluoropolymer, PFA, FEP, or PE. Preferably, the green polymer tube 216 is unreinforced, such that the bending flexibility of the distal end of the resulting intravascular catheter is not degraded, and furthermore, the processed polymer tube 216’ (shown in Fig. 15) may be radially expanded within the hypotube structure 200. In an alternative embodiment, instead of extruding the green polymer tube 216, the green polymer tube 216 may be formed from a dip coating/case film process by coating a wire with a PTFE layer, and then removing the wire. Further details discussing the fabrication of PTFE polymer tubes are described in PCT Publication No. WO2021/025814, which is expressly incorporated herein by reference.

[74] In the preferred embodiment, the green polymer tube 216 initially has a uniform polymer composition having uniform mechanical properties (e.g., uniform flexural stiffness and uniform density), although in alternative embodiments, the green polymer tube 216 may initially have a non-uniform composition and/or have non-uniform mechanical properties (e.g., different densities along the length of the green polymer tube 216) as long as the average density and/or flexural stiffness of the distal section 220 of the processed polymer tube 216’ is less than that of the proximal section 220 of the processed polymer tube 216’.

[75] The method further comprises locally treating the distal section 220 of the green polymer tube 216 to form a processed polymer tube 216’, such that the distal section 220 has a density that is less than the density of the proximal section 218 (step 108) (see Fig. 15). As a result, the flexural stiffness of the distal section 220 of the processed polymer tube 216 is less than the flexural stiffness of the distal section 220 of the green polymer tube 216. In the preferred embodiment, the flexural stiffness/density of the distal section 220 of the green polymer tube 216 is modified by expanding the distal section 220 of the green polymer tube 216 beyond the elastic limit of the material therein under an elevated temperature (e.g., in the range of 500°F-700°F, such as 650°F). In one embodiment, the proximal section 218 of the green polymer tube 216 may be affixed within a mandrel (not shown) as the distal section 220 of the green polymer tube 216 is expanded. The distal section 220 of the green polymer tube 216 may be expanded longitudinally (stretched), radially, or both, the latter of which may be referred to as bi-axial. In the illustrated embodiment, the distal section 220 of the green polymer tube 216 is stretched at a controlled speed and ratio (e.g., 1 :4).

[76] As a result, the distal section 220 of the green polymer tube 216 will be transformed into a microporous structure 68 of fibrils 70 and nodes 72 to form the distal section 220 of the processed polymer tube 216’, as illustrated in Fig. 19, whereas the proximal section 218 of the processed polymer tube 216’ will have no such microporous structure. Typically, the size of a fibril 70 is in the range of 0.05 pm to 0.5 pm in diameter. The surfaces of the fibrils 70 and nodes 72 define numerous interconnecting pores 74 that extend completely through the wall of the processed polymer tube 216’. The average size of the pores 74 is sufficient to be deemed microporous. For example, the average size of the pores 74 may be in the range of 0.01 pm to 10 pm. The nodes 72 serve as “hinges”, thereby providing more flexibility and material strength to the distal section 220 of the processed polymer tube 216 relative to the proximal section 218 of the processed polymer tube 216’.

[77] In alternative embodiments, rather than transforming the distal section 220 of the green polymer tube 216 into a microporous structure 68 of fibrils 70 and nodes 72 to form the distal section 220 of the processed polymer tube 216’, the distal section 220 of the green polymer tube 216 may be transformed into other types of porous and fibrous structures. For example, the distal section 220 of the green polymer tube 216 may be transformed into a microporous structure 68’ (Fig. 20A) or microporous structure (Fig. 20B) that has fibrils 70, but no nodes. The surfaces of the fibrils 70 define numerous interconnecting pores 74 that extend completely through the wall of the processed polymer tube 216’. Ultimately, the nature of the porous and fibrous structure into which the distal section 220 of the green polymer tube 216 will be transformed will depend on the type of stretch and amount of stretch that exerted on the distal section 220 of the green polymer tube 216.

[78] Thus, the proximal section 218 of the processed polymer tube 216 will be less dense, and will have less flexural stiffness, than that of the distal section 218 of the processed polymer tube 216. For example, if the green polymer tube 216 is PTFE, the proximal section 218 of the processed polymer tube 216’ may be 2.1 grams/cm³, whereas the distal section 220 of the processed polymer tube 216’ may be in the range of 0.1-1 .0 grams/cm³. The density of the distal section 218 of the processed polymer tube 216 may be controlled by controlling the porosity of the distal section 218 of the processed polymer tube 216 (i.e., an increase in porosity (increased pore size), results in larger voids in the polymeric material, and thus a decrease in density, of the distal section 218 of the processed polymer tube 216. In the case where the green polymer tube 216 is composed of PTFE, the distal section 218 of the green polymer tube 216 will be converted to ePTFE to form the processed polymer tube 216’, whereas the proximal section 220 of the processed polymer tube 216’ will remain PTFE.

[79] The method 100 may optionally comprise decreasing the length of the processed polymer tube 216’ by removing an end of the distal section 220 from the polymer tube 216 (see Fig. 16), such that the length of the distal section 220 of the processed polymer tube 216’ matches the length of the pattern 210 of apertures 212 and solid elements 214 on the distal end 206 of the hypotube structure 200 (step 110). The method 100 may optionally comprise forming a pattern of apertures and solid elements on the distal end 218 of the polymer tube 216 (not shown).

[80] The method 100 further comprises disposing the processed polymer tube 216’ within the lumen 206 of the hypotube structure 200 (see Fig. 17) (step 112). The method further comprises expanding the processed polymer tube 216’ within the lumen 206 of the hypotube structure 200, thereby decreasing the wall thickness of the processed polymer tube 216’, as well as creating continuous intimate contact between the exterior of the processed polymer tube 216’ and the interior of the hypotube structure 200 (step 114). As a result, the processed polymer tube 216’ serves as an inner polymer liner to the hypotube structure 200. The method 100 optionally comprises intermittently attaching the processed polymer tube 216’ to the solid elements 214 of the hypotube structure 200 at at least one discrete adhesion region 224 along a length of the distal end 206 of the tubular body 202 (see Fig. 18) (step 116). Although in the illustrated method, the discrete adhesion region(s) 224 has a circumferential band pattern, it should be appreciated that the discrete adhesion region(s) 224 may alternatively take any suitable pattern, including a spiral pattern with a constant pitch/width or a variable pitch/width. Different techniques for intermittently attaching the processed polymer tube 216’ to the solid elements 214 of the distal end 206 of the tubular body 202 are described in U.S. Patent Publication No. 2020/0129733, which is expressly incorporated herein by reference.

[81] The method 100 optionally comprises affixing an outer polymer jacket (not shown) to the exterior of the hypotube structure 200 (step 118). In this case, the polymer tube 216 may be intermittently attached to the outer polymer jacket at at least one discrete adhesion region along a length of the distal end 206 of the tubular body 202. In this case, instead of intermittently attaching the polymer tube 216 to the solid elements 214 of the hypotube structure 200 via the tie layer 226 in step 112, the polymer tube 216 may be intermittently attached to the outer polymer jacket via the tie layer 226. In other embodiments, the polymer tube 216 may be intermittently attached to both the solid elements 214 of the hypotube structure 200 and the outer polymer jacket via the tie layer 226.

[82] Lastly, the method 100 comprises affixing a proximal catheter hub 220 to the proximal end 204 of the hypotube structure 200 (not shown) (step 120).

[83] Although particular embodiments have been shown and described herein, it will be understood by those skilled in the art that they are not intended to limit the disclosed inventions, and it will be obvious to those skilled in the art that various changes, permutations, and modifications may be made (e.g., the dimensions of various parts, combinations of parts) without departing from the scope of the disclosed inventions, which is to be defined only by the following claims and their equivalents. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The various embodiments shown and described herein are intended to cover alternatives, modifications, and equivalents of the disclosed inventions, which may be included within the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1. An intravascular catheter, comprising: an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body; and an inner polymer liner disposed within the tubular body lumen, the inner polymer liner having an elongated seamless polymer tube with a proximal section composed of polytetrafluoroethylene (PTFE) and a distal section composed of expanded polytetrafluoroethylene (ePTFE), and a liner lumen extending through the polymer tube.

2. The intravascular catheter of claim 1 , wherein the tubular body is a hypotube structure.

3. The intravascular catheter of claim 2, wherein the hypotube structure has a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

4. The intravascular catheter of claim 3, wherein the distal section of the seamless polymer tube spans the hypotube pattern.

5. The intravascular catheter of claim 1 , further comprising an outer polymer jacket disposed on an exterior surface of the tubular body.

6. The intravascular catheter of claim 1 , wherein the tubular body is an outer polymer jacket.

7. The intravascular catheter of claim 1 , further comprising a tie layer attaching the inner polymer liner to the tubular body.

8. An intravascular catheter, comprising: an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body; and an inner polymer liner disposed within the tubular body lumen, the inner polymer liner having an elongated seamless polymer tube with a proximal section having a first density and a distal section having a second density less than the first density, and a liner lumen extending through the seamless polymer tube.

9. The intravascular catheter of claim 8, wherein the tubular body is a hypotube structure.

10. The intravascular catheter of claim 9, wherein the hypotube structure has a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

11. The intravascular catheter of claim 10, wherein the distal section of the seamless polymer tube spans the hypotube pattern.

12. The intravascular catheter of claim 8, further comprising an outer polymer jacket disposed on an exterior surface of the hypotube structure.

13. The intravascular catheter of claim 8, wherein the tubular body is an outer polymer jacket.

14. The intravascular catheter of claim 8, further comprising a tie layer attaching the inner polymer liner to the tubular body.

15. The intravascular catheter of claim 8, wherein the distal section of the seamless polymer tube has a microporous structure.

16. The intravascular catheter of claim 15, wherein the microporous structure has fibrils.

17. The intravascular catheter of claim 15, wherein the microporous structure has fibrils and nodes.

18. The intravascular catheter of claim 8, wherein the proximal section of the seamless polymer tube has a first flexural stiffness, and the distal section of the seamless polymer tube has a second flexural stiffness less than the first flexural stiffness.

19. The intravascular catheter of claim 8, wherein the proximal end of the seamless polymer tube is composed of polytetrafluoroethylene (PTFE), and the distal end of the seamless polymer tube is composed of expanded polytetrafluoroethylene (ePTFE).

20. A method of manufacturing an intravascular catheter, comprising: providing an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body; providing a polymer tube having a proximal section, a distal section, and a tube lumen extending through the polymer tube, the proximal section and distal section of the polymer tube being composed of polytetrafluoroethylene (PTFE); converting the distal section of the polymer tube from PTFE to expanded polytetrafluoroethylene (ePTFE), while the proximal section remains PTFE; and affixing the polymer tube within the tubular body lumen.

21. The method of claim 20, wherein providing the polymer tube comprises selecting a PTFE resin, and extruding the polymer tube from the PTFE resin.

22. The method of claim 20, wherein transforming the distal section of the polymer tube from PTFE to ePTFE comprises locally expanding the distal section of the polymer tube at an elevated temperature.

23. The method of claim 22, wherein locally expanding the distal section of the polymer tube comprises stretching the distal section of the polymer tube.

24. The method of claim 23, further comprising decreasing the length of the polymer tube by removing an end of the distal section of the polymer tube from the polymer tube.

25. The method of claim 22, wherein the elevated temperature is in the range of 500°F-700°F.

26. The method of claim 20, wherein affixing the polymer tube within the tubular body lumen comprises radially expanding the polymer tube within the tubular body lumen.

27. The method of claim 20, wherein the tubular body is a hypotube structure.

28. The method of claim 27, wherein the hypotube structure has a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

29. The method of claim 28, wherein the polymer tube is affixed within the tubular body lumen, such that the distal section of the polymer tube spans the hypotube pattern.

30. The method of claim 27, further comprising affixing an outer polymer jacket on an exterior surface of the hypotube structure.

31. The method of claim 18, wherein the tubular body is an outer polymer jacket.

32. A method of manufacturing an intravascular catheter, comprising: providing an elongate tubular body with a proximal end, a distal end, and a tubular body lumen extending between the proximal end and the distal end of the tubular body; providing a polymer tube having a proximal section, a distal section, and a tube lumen extending through the polymer tube; locally expanding the distal section of the polymer tube at an elevated temperature, such that the distal section of the polymer tube is composed of a microporous structure, while the proximal section of the polymer is not composed of the microporous structure; and affixing the polymer tube within the tubular body lumen.

33. The method of claim 32, wherein the microporous structure has fibrils.

34. The method of claim 32, wherein the microporous structure has fibrils and nodes.

35. The method of claim 32, wherein providing the polymer tube comprises selecting a polymer resin, and extruding the polymer tube from the polymer resin.

36. The method of claim 33, wherein locally expanding the distal section of the polymer tube comprises stretching the distal section of the polymer tube.

37. The method of claim 36, further comprising decreasing the length of the polymer tube by removing an end of the distal section of the polymer tube from the polymer tube.

38. The method of claim 32, wherein the elevated temperature is in the range of 500°F-700°F.

39. The method of claim 32, wherein affixing the polymer tube within the tubular body lumen comprises radially expanding the polymer tube within the tubular body lumen.

40. The method of claim 32, wherein the tubular body is a hypotube structure.

41. The method of claim 40, wherein the hypotube structure has a hypotube pattern of apertures and solid elements disposed on the distal end of the hypotube structure.

42. The method of claim 41 , wherein the polymer tube is affixed within the tubular body lumen, such that the distal section of the polymer tube spans the hypotube pattern.

43. The method of claim 40, further comprising affixing an outer polymer jacket on an exterior surface of the hypotube structure.

44. The method of claim 32, wherein the tubular body is an outer polymer jacket.