WO2025090651A1

WO2025090651A1 - Balloon catheter

Info

Publication number: WO2025090651A1
Application number: PCT/US2024/052632
Authority: WO
Inventors: Tanhum Feld; Eitan Konstantino
Original assignee: Trireme Medical LLC
Current assignee: Trireme Medical LLC
Priority date: 2023-10-23
Filing date: 2024-10-23
Publication date: 2025-05-01
Anticipated expiration: 2026-04-23

Abstract

A system for treating intercranial arterial disease (ICAD) include a balloon catheter and an expandable flexible element disposed around the balloon. The expandable flexible element is asymmetric and comprises two end segments joined to a middle segment by two bridging segments. Each segment of the expandable element may have different flexibilities relative to each other to allow for improved navigation of the catheter through tortuous vasculature. The flexibility of each segment may be determined by shape and/or length geometries.

Description

BALLOON CATHETER

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

[0001] This application claims priority benefit of U.S. Provisional Application No. 63/592,291, filed October 23, 2023, titled “BALLOON CATHETER” which is hereby incorporated by reference in its entirety herein.

BACKGROUND

Field

[0002] The present disclosure relates to treatment of intra-cranial arterial disease (ICAD).

Description of the Related Art

[0003] The brain receives arterial blood from the bilateral internal carotid artery (ICA) and verterbral artery (VA). The ICA carries blood into the anterior cerebral circulation including the middle and anterior cerebral arteries. The anterior and posterior circulations communicate through the Circle of Willis via anterior and posterior communicating arteries.

SUMMARY

[0004] Devices for treatment of ICAD are delivered through femoral or radial access and through the tortuous and tight anatomy of the ICA, arguably the most tortuous path for interventional devices, making it difficult for balloon expandable devices to track to the cerebral circulation due to lack of flexibility and large profile. In addition, arteries of the central nervous system lack an external elastic lamina and are thinner compared to coronary or peripheral arteries. The inability to use angioplasty balloons with external structures for ICAD, due to the complexity of the anatomy, requires a novel approach.

[0005] The present disclosure relates to a systems and methods for treating a stenosis in an artery, particularly an intra-cranial artery, comprising a balloon catheter and an asymmetric expandable flexible element placed over the balloon. The expandable flexible element may have an asymmetric construction improving the ease with which the catheter is navigated throughout tortuous vasculature. The asymmetric geometry of the flexible element may additionally assist in the uniform expansion and retraction of the flexible element in response to inflation and deflation of the balloon. [0006] The devices and methods described herein relate to a balloon catheter including: a catheter shaft; a balloon carried by the catheter shaft; and an asymmetrical expandable element positioned over the balloon. The asymmetrical expandable element can include a proximal end segment, a distal end segment, and a middle segment therebetween. The expandable element may be made of a shape memory material (e.g., nitinol) and/or other suitable polymer material. The proximal end segment and/or the distal end segment affix the expandable element to the catheter shaft. The proximal end segment may be shaped and/or sized differently from the distal end segment. For example, the distal end segment may be the same length or shorter than the proximal end segment. The middle segment includes a plurality of radial rings and a plurality of longitudinal struts. The plurality of radial rings may include less than or equal to eleven radial rings (or less than or equal to ten, nine, eight, seven, six, five, or four radial rings). Each of the plurality of longitudinal struts may include a sinusoidal pattern.

[0007] The balloon may include a proximal balloon taper, a proximal leg, a distal balloon taper, a distal leg and a working length between the proximal balloon taper and the distal balloon taper. The proximal end segment of the expandable element may be positioned over the proximal balloon taper and proximal leg, and the distal end segment of the expandable element is positioned over the distal balloon taper and distal leg. The middle segment may be positioned over the working length of the balloon.

[0008] Each of the proximal end segment and the distal end segment includes one or more end rings. The distal end segment may include a first end ring and a second end ring. The first end ring may be shaped or sized differently from the second end ring.

[0009] The proximal end segment may have a different number of end rings (e.g., greater number) than the distal end segment. For example, the proximal end segment may have a different two end rings, and the distal end segment may have one end ring. Where the proximal end segment includes a first end ring and a second end ring, the second end ring may be inverted relative to the first end ring.

[0010] Each of the one or more end rings may have a different shape from the radial rings in the middle segment. For example, the one or more end rings may have a zigzag pattern and/or the radial rings may have a sinusoidal pattern. Each of the one or more end rings may have two zigzags (e.g., two peaks), but other numbers of zigzags are possible (e.g., three, four, or more). At least one of the end rings in the distal end segment may have a greater number of zigzags compared to at least one of the end rings in the proximal end segment.

[0011] In some embodiments, the expandable element is capable of bending to a radius of less than or equal to 3.0 mm or less than or equal to 1.5 mm. The balloon may have a wall thickness of less than 0.015 inches.

[0012] The expandable element may include longitudinal bridges connecting the middle segment to the proximal end segment and the distal end segment. Each of the plurality of longitudinal struts may include a sinusoidal pattern and/or each of the longitudinal bridges may be straight.

[0013] Any feature, structure, or step disclosed herein can be replaced with or combined with any other feature, structure, or step disclosed herein, or omitted. Further, for purposes of summarizing the disclosure, certain aspects, advantages, and features of the inventions have been described herein. It is to be understood that not necessarily any or all such advantages are achieved in accordance with any particular embodiment of the inventions disclosed herein. No individual aspects of this disclosure are essential or indispensable.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Various embodiments are depicted in the accompanying drawings for illustrative purposes and should in no way be interpreted as limiting the scope of the embodiments. Furthermore, various features of different disclosed embodiments can be combined to form additional embodiments, which are part of this disclosure.

[0015] Figure 1 shows an expandable element.

[0016] Figure 2 shows another expandable element.

[0017] Figure 3 shows a close-up view of a middle portion of an expandable element.

[0018] Figure 4 shows a schematic of an expandable element attached to a balloon catheter.

DETAILED DESCRIPTION

[0019] Due to the compromised deliverability, angioplasty balloons with external structures helping to reduce vessel trauma, could play a major role in treatment of ICAD but are not currently used due to deliverability limitations. [0020] The present disclosure relates to systems and methods for treating stenosis in an intra-cranial artery comprising a balloon catheter and an asymmetric expandable flexible element placed over the balloon.

[0021] Figure 1 shows an expandable element 100 in a lay-flat configuration (e.g., prior to the attachment of the expandable element around the balloon of the balloon catheter). The expandable element can include an elastic material, for example a shape memory material (e.g., nitinol) and/or any other suitable polymer material. The expandable element 100 can be affixed to an exterior surface of the balloon of the balloon catheter, as shown in schematic form in Figure 4, such that the expandable element 100 transitions between an expanded configuration and a collapsed configuration in response to inflation and deflation of the balloon. For example, the expandable element 100 may transition from the collapsed configuration to the expanded configuration during inflation of the balloon, and then transition back to the collapsed configuration when the balloon is deflated.

[0022] The geometry of the expandable element 100 may include a middle segment 104 connected to proximal end segment 102 and a distal end segment 106 by longitudinal bridging segments 112 composed of a plurality of longitudinal bridges. The entire expandable element 100 may be laser cut as a monolithic structure. The length of the expandable element 100 may be at least 10 mm and/or no more than 20 mm (or no more than 15 mm) longer than the working length of the balloon. For example, if being used with a 2mm x 15mm balloon, the length of the expandable element 100 may be at least approximately 25 mm. The diameter of the expandable element 100 in the expanded configuration may be less than or equal to 5 mm, less than or equal to 4.75 mm, less than or equal to 4.5 mm, less than or equal to 4.25 mm, less than or equal to 4 mm, less than or equal to 3.75 mm, less than or equal to 3.5 mm, less than or equal to 3.25 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, or less than or equal to 2.0 mm, ranges between such values, and the like.

[0023] The middle segment 104 may include a plurality of radial rings 110 and a plurality of longitudinal struts 114 positioned over the working length of the balloon. The proximal end segment 102 and distal end segment 106 may be configured for affixing the expandable element 110 to the balloon catheter and may be positioned beyond proximal and distal tapers of the balloon, respectively. The longitudinal bridging segments 112 may be positioned over the proximal and distal tapers over the balloon to connect the end segments 102, 106 to the middle segment 104. The expandable element 100 may bend to a radius of less than or equal to 3 mm or less than or equal to 1.5 mm (e.g., less than 3 mm, less than 2.8 mm, less than 2.6 mm, less than 2.5 mm, less than 2.4 mm, less than 2.2 mm, less than 2 mm, less than 1.8 mm, less than 1.6 mm, less than 1.5 mm, less than 1.4 mm, less than 1.2 mm, less than 1 mm, less than, 0.8 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.2 mm, less than 0.1 mm, 0 mm, ranges between such values, and the like) at any point along its length to better facilitate delivery though the highly tortuous anatomy of the ICA. The expandable element 100 flexibility to bend may be achieved by different means applied to certain portions of the structure, as described below, and may be applied individually or as a whole.

[0024] For example, the flexibility of the middle segment may be achieved by a sinusoidal configuration of the radial rings 110 and longitudinal struts 114. The longitudinal struts 114 may be arranged to have a low-profile cross section, such as, for example, a square flexible metal cross-section measuring between approximately 70 microns by 70 microns and approximately 35 microns by 35 microns (e.g, a square flexible metal cross-section measuring approximately 70 microns by 70 microns, approximately 65 microns by 65 microns approximately 60 microns by 60 microns, approximately 55 microns by 55 microns approximately 50 microns by 50 microns, approximately 45 microns by 45 microns approximately 40 microns by 40 microns, approximately 35 microns by 35 microns, ranges between such values, and the like), which may additionally contribute to the flexibility of the middle segment 104. One or more segments of the expandable structure (e.g., the middle segment, the proximal and distal end segments, and/or the bridging segment) may be heat treated to optimize the geometry, flexibility, and material response. To accommodate a low cross-section of the middle segment 104 of the expandable element 100, the underlying balloon of the balloon catheter may be a thin wall balloon, defined by a double wall thickness less than approximately 0.015 inches (e.g., less than 0.015 inches, less than 0.010 inches, less than 0.009 inches, less than 0.008 inches, less than 0.007 inches, less than 0.006 inches, less than 0.005 inches, less than 0.004 inches, less than 0.003 inches, less than 0.002 inches, less than 0.001 inches, ranges between such values, and the like). The balloon of the balloon catheter may have a limited rated burst pressure of less than between approximately 16 atmospheres and approximately 12 atmospheres (e.g. less than approximately, 16 atm, less than approximately 15 atm, less than approximately 14 atm, less than approximately 13 atm, less than approximately 12 atm, ranges between such values, and the like).

[0025] As shown, in Figure 1, the geometry of expandable structure 100 may include asymmetrical features, which advantageously allows navigating the ICA to deliver less traumatic angioplasty therapy to the intra cranial arteries that can reduce the need for permanent implants (e.g., stents) that have been shown to routinely fail in many clinical studies.

[0026] Each of the proximal end segment 102 and the distal end segment 106 may comprise one or more end rings 120. As illustrated in Figure 1, the end rings 120 may include no more than two zigzags (e.g., two peaks), but in other embodiments, the end rings 120 may include a greater number of zig-zags. However, having only two zig-zags (e.g., two zig-zags) may allow for an improved bond with a polymer, with a lower profile and higher flexibility.

[0027] The one or more end rings 120 may be secured to the balloon catheter. In some embodiments, the end rings are thermal bonded to the balloon catheter. For example, an over-tube may be placed over the bond area to be melted. A shrink tube may be placed over the bond area that shrinks when heated and compresses the over-tube material down into the spaces between the end ring struts. The shrink tube may then be removed after the heating. With less struts (e.g., only two zig-zags), it is easier to achieve a lower profile bond because there is more space for the polymer to melt into. The one or more end rings 120 may be secured to the balloon catheter using other methods, including liquid adhesive.

[0028] As the proximal end segment 102 is subjected to higher bending moment over curves during navigation through the ICA, the proximal end segment 102 may be optimized for bending and/or reduction of orthogonal forces. The distal end segment 106 may be optimized for guidewire tracking. The geometries of the proximal end segment 102 and distal end segment 106 may thus differ from each other in order to accommodate their respective functions.

[0029] For example, the proximal end segment 102 may have a greater length, which allow it to accommodate a greater number of end rings 120, than the distal end segment 106. For example, the length of the proximal segment 102 may be at least 2X the length of the distal segment 106. The proximal end segment 104 may have a length of at least approximately 4 mm and/or less than approximately 6 mm (e.g., approximately 4 mm, approximately 4.1 mm, approximately 4.2 mm, approximately 4.3 mm, approximately 4.4 mm, approximately 4.5 mm, approximately 4.6 mm, approximately 4.7 mm, approximately 4.8 mm, approximately 4.9 mm, approximately 5 mm, ranges between such values, and the like). The longer length of the proximal end segment 102 causes the proximal end segment 102 to be subjected to high moment when bent, which allows for offsetting some of the bending forces applied to the proximal segment 102 during navigation through the ICA and makes it easier to flex. In some embodiments, the proximal end segment 102 may have two end rings 120 for increased flexibility. The end rings 120 of the proximal end segment 102 may face one another to create a construction that is both flexible for bending but still strong enough to resist collapsing (e.g., to a more condensed geometry than the collapsed configuration) smaller geometries when transitioning between the expanded and collapsed configurations.

[0030] In contrast, the distal end segment 106 may be optimized for tracking a guidewire, and thus it may be desirable that the distal end segment 106 is as short as possible to accommodate crossing over tortuous anatomy. For example, the distal end segment 106 may have a length of at least approximately 1.5 mm and/or less than 3.5 mm (e.g., approximately 1.5 mm, approximately 1.6 mm, approximately 1.7 mm, approximately 1.8 mm, approximately 1.9 mm, approximately 2 mm, approximately 2.1 mm, approximately 2.2 mm, approximately 2.3 mm, approximately 2.4 mm, approximately 2.5 mm, ranges between such values, and the like) The shorter length for the distal end segment 106 may only allow the distal segment to include one end ring 120, as shown in Figure 1.

[0031] It would not be desirable for the distal end segment to have a longer construction to increase flexibility because it would require extending the catheter beyond the balloon more than necessary and increasing the risk of damaging blood vessels distal of the treatment site. The disclosed architecture having a longer proximal end segment 102 and a shorter distal end segment 106 creates an asymmetric geometry of the expandable element 100 with flexible attachments to the balloon catheter that allow it to be delivered successfully through difficult anatomies.

[0032] As discussed above, the end rings 120 of the proximal end segment 102 and distal segment end segment 106 may include two or more zigzags. For example, as shown in Figure 1, the end rings 120 of both the proximal end segment 102 and the distal end segment 106 may each comprise only two zigzags 108. However, in other embodiments, the at least one of the end rings 120 of the distal end segment 106 may be include a greater number of zigzags 108 than the end rings 120 of the proximal end segment 102.

[0033] For example, as shown in Figure 2, the end rings 120 of the proximal end segment 102 may include two zigzags, and the end ring 120 of the distal end segment may include two or four zigzags 108. The end rings 120 of the distal end segment may include the same or a different number of zigzags. A greater number of zigzags 108 may increase the stiffness of the distal end segment 106. However, this may not always be desirable as having a stiffer distal end segment 106 may make it more difficult to navigate the catheter through tortuous anatomy.

[0034] The longitudinal bridging segments 112 that connect the proximal end segments 102 and the distal end segment 106 to the middle segment 104 may be in aligned in a longitudinal, rather than a radial configuration in order to adapt to the balloon tapers during deflation. During deflation, the balloon material does not uniformly compress back to its preinflated folded configuration. The length of the longitudinal bridging segments 112 may therefore be minimized to the length of the balloon taper to reduce the bridging segments’ 112 tendency to collapse and/or buckle when bent during deflation of the balloon. For example, the longitudinal bridging segments 112 may have a length of less than or equal to approximately 3.5 mm, less than or equal to approximately 3.0 mm, less than or equal to approximately 2.5 mm, or less than or equal to 2.2 mm (e.g., approximately 1.5 mm, approximately 1.6 mm, approximately 1.7 mm, approximately 1.8 mm, approximately 1.9 mm, approximately 2 mm, approximately 2.1 mm, approximately 2.2 mm, approximately 2.3 mm, approximately 2.4 mm, approximately 2.5 mm, ranges between such values, and the like).

[0035] Figure 3 shows a close-up example of middle segment 104 of the expandable element 100. As shown, the longitudinal struts 114 are comprised of s-shaped portions 302 and straight portions 304 in a lay-flat or condensed configuration.

[0036] The radial rings 110 may be arranged in a sinusoidal pattern in the condensed configuration and are stretched when the balloon is inflated. The amplitude of the radial rings 110 may be less than or equal to approximately 2.0 mm or less than or equal to approximately 1.5 mm (e.g., approximately 0.5 mm, approximately 0.6 mm, approximately 0.7 mm, approximately 0.8 mm, approximately 0.9 mm, approximately 1 mm, approximately 1.1 mm, approximately 1.2 mm, approximately 1.3 mm, approximately 1.4 mm, approximately 1.5 mm, ranges between such values, and the like) in the condensed configuration. The amplitude of the radial rings 110 may reduce during inflation such that the radial rings 110 become substantially circular.

[0037] The length of each of the radial rings 110 may determine how much the rings radial rings 110 will sink into the inflated balloon surface. If the length of the radial ring 110 is made shorter, meaning the radial ring 110 is made with a lower amplitude, the radial ring 110 will sink more into the balloon surface and will create deeper channel in the balloon surface on inflation.

[0038] For example, the length of each radial rings 110 may be less than or equal to about 10 mm, less than or equal to about 9 mm, less than or equal to about 8mm, or less than or equal to about 7 mm (e.g., approximately 6 mm, approximately 6.1 mm, approximately 6.24 mm, approximately 6.36 mm, approximately 6.43 mm, approximately 6.5 mm, approximately 6.61 mm, approximately 6.72 mm, approximately 6.8 mm, approximately 6.9 mm, approximately 7 mm, ranges between such values, and the like) when the balloon circumference is between approximately 5 mm and 10 mm, or between approximately 6 mm and 8 mm (e.g., approximately 6 mm, approximately 6.15 mm, approximately 6.28 mm, approximately 6.36 mm, approximately 6.44 mm, approximately 6.5 mm, ranges between such values, and the like).

[0039] The length of the radial rings is less than a circumference of a fully inflated balloon. The radial rings 110 cannot expand to the diameter of the inflated balloon and remains sunk in the balloon material below the surface. When the operator increases the inflation pressure beyond the nominal pressure, the balloon diameter continues to grow while the radial rings radial rings 110 create deeper channels into the balloon surface. The inflated balloon diameter may be less than or equal to 5.0 mm, less than or equal to 4.5 mm, less than or equal to 4.0 mm, less than or equal to 3.5 mm, less than or equal to 3.0 mm, less than or equal to 2.5 mm, or less than or equal to 2.0 mm.

[0040] For intra-cranial applications, it may be desired that the expandable element 100 be designed such that it can be expanded via the balloon with lower pressure than may be required in other applications. For example, the length of each radial ring 110 may be made slightly longer, resulting in a higher sinusoidal amplitude which requires lower pressure to expand. For example, in intra-cranial application the length of the radial rings 110 may be similar to the balloon circumference at 2 mm diameter (e.g., within 0.1 mm or within 0.5 mm), while for other applications the length of the radial ring may be between approximately 0.2 mm and 0.4 mm (e.g., approximately 0.2 mm, approximately 0.22 mm, approximately 0.24 mm, approximately 0.25 mm, approximately 0.26 mm, approximately 0.28 mm, approximately 0.3 mm, approximately 0.32 mm, approximately 0.34 mm, approximately 0.35 mm, approximately 0.36 mm, approximately 0.38 mm, approximately 0.4 mm, ranges between such values, and the like) shorter than the balloon circumference.

[0041] The radial rings 110 may be spaced apart along the working length of the balloon. The distance between adjacent radial rings 110 may also affect the balloon surface that is formed on inflation. For example, the distance between adjacent radial rings 110 may determine the length of the longitudinal struts 114 that connect between adjacent rings. A longer distance between each radial rings 110 may result in a shallower channel being formed in the balloon by the longitudinal struts 114 upon inflation. Conversely, a shorter distance between each radial rings 110 may result in a deeper channel being formed in the balloon by the longitudinal struts 114 upon inflation

[0042] In some embodiments, the middle segment 104 may include a greater number of radial rings than longitudinal struts. The middle segment 104 may include eight radial rings 110 and seven longitudinal struts 114, e.g., as shown in Figure 3, resulting in total a difference of less than or equal to about 1 mm (e.g., approximately 0.9, approximately 0.8, approximately 0.7 mm, or approximately 0.6 mm) between the total length of each longitudinal strut segment and the distance between the ends of the longitudinal strut segment in the S- shape (when collapsed), where the longitudinal strut segment extends between adjacent radial rings. In such examples, the distance between each of the radial rings 110 may be less than or equal to about 3 mm, less than or equal to about 2.5 mm, or less than or equal to about 2.0 mm (e.g., approximately 1.75 mm, approximately 1.8 mm, approximately 1.85 mm, approximately 1.9 mm, approximately 1.95 mm, ranges between such values, and the like) while the length of the longitudinal struts 114 may be less than or equal to about 3.5 mm, less than or equal to about 3 mm, less than or equal to about 2.5 mm, or less than or equal to about 2.0 mm (e.g., approximately 1.5 mm, approximately 1.75 mm, approximately 2 mm, approximately 2.25 mm, approximately 3 mm, ranges between such values, and the like). This difference allows the shape of longitudinal strut 1 14 to transform upon inflation of the balloon. The middle segment 104 may include no more than eight radial rings 110.

[0043] The longitudinal struts 114 may not be as radially resistant to balloon inflation as compared to the radial rings 110, such that while the ends of a longitudinal strut segment 114a between two radial rings 110 is pressed inwardly into the balloon surface by the radial ring 110, the S-shaped portion therebetween is pushed outwardly by the balloon inflation pressure.

[0044] The radial rings 110 may be rotated relative to adjacent rings 110 along the working length of the balloon. As discussed above, the longitudinal struts 114 are comprised of s-shaped portions 302 and straight portions 304 in a lay-flat or condensed configuration, formed in part by the sinusoidal shape of the longitudinal struts 114 when the expandable element 100 is in the compressed configuration. When the balloon is inflated and the expandable element 100 transitions to the expanded configuration, the shape of the longitudinal struts 114 changes. The distance between ends of the longitudinal strut grows very slightly just enough to accommodate the reduction in sinusoidal amplitude of a single radial ring 110 amplitude. While the distance between ends of the longitudinal strut 114 grows, the rings 110 rotate around the balloon axis and the s-shape portions 302 straighten. At the same time, while the longitudinal strut 114 straightens, it assumes a wave shape that projects inwardly into the balloon due the pressure exerted on the longitudinal struts 114 by the radial rings 110.

[0045] The s-shape portions 302 inhibit enough length to accommodate both deformations, but it may inhibit more length than necessary. While the inhibited length may be made minimal for other medical applications such as in coronary or peripheral arteries, it may be made longer for applications in intracranial arteries.

[0046] The length of the longitudinal strut segment 114a and the parameters of the s-shaped portions 302 identified by the reference letters “D” and “R” in Figure 3 affect the deliverability of the device into the intracranial arteries by affecting the longitudinal flexibility of the device.

[0047] Reference letter “D” represents the shift between the radial rings, which may be, for example, between approximately 0.8 mm and approximately 0.5mm (e.g., approximately 0.78 mm, approximately 0.75 mm, approximately 0.7 mm, approximately 0.68 mm, approximately 0.65 mm, approximately 0.64 mm, approximately 0.6 mm, approximately

-l i 0.55 mm, ranges between such values, and the like). “D” affects how much the radial rings 1 10 arc rotated relative to adjacent rings 100. In intracranial arteries applications, it may be desirable to construct the expandable element 100 such that the Delta is larger than may be required for other applications. A larger Delta results in a longer longitudinal strut segment 114a and smaller radius (represented by reference letter “R”) which allows for higher longitudinal flexibility. For example, coronary or peripheral arteries applications may require that the Delta is between approximately 0.3 mm and 0.5 mm (e.g. approximately 0.3 mm, approximately 0.35 mm, approximately 0.4 mm, approximately 0.45 mm, approximately 0.5 mm, ranges between such values, and the like).

[0048] In contrast, applications involving intracranial arteries may require that the Delta is between approximately 0.5 mm and 0.8 mm (e.g. approximately 0.5 mm, approximately 0.55 mm, approximately 0.6 mm, approximately 0.65 mm, approximately 0.7 mm, approximately 0.75 mm, approximately 0.8 mm, ranges between such values, and the like), resulting in the overall length of the longitudinal strut segment to be about 0.1 mm longer. In such embodiments, a radius “R” for may be between approximately 0.5 mm and approximately 0.8 mm (e.g., approximately 0.5 mm, approximately 0.45 mm, approximately 0.5 mm, approximately 0.55 mm, approximately 0.6 mm, approximately 0.65 mm, approximately 0.7 mm, approximately 0.75 mm, approximately 0.8 mm, ranges between such values, and the like). Such example parameters result in a significant increase to longitudinal flexibility of the middle segment 104, and significantly reduction in the force is required to bend the device during navigation to the treatment site.

[0049] Figure 4 shows a schematic of an expandable element 100 attached to balloon catheter 400. As shown, the expandable elements 100 described herein may be wrapped around the balloon 410 of the balloon catheter 400, and the longitudinal struts 114 create radial rings 110 around the circumference of the balloon 410. The expandable element 100 impresses axial channels 412 and circumferential channels 414 on the surface of the balloon 410. As the balloon 410 is inflated, the contact force between the balloon 410 the expandable element 100 cause the axial channels 412 and circumferential channels 414 become deeper.

Terminology [0050] Although certain embodiments have been described herein with respect to intra-cranial arterial disease, the balloon catheters described herein can be used in connection with any small diameter vessels, for example vessels having a diameter of less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3.5 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, or less than or equal to 2 mm.

[0051] As used herein, the relative terms “proximal” and “distal” shall be defined from the perspective of the catheter system. Thus, proximal refers to the direction of the handle and distal refers to the direction of the catheter tip.

[0052] The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.

[0053] The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, and “substantially” may refer to an amount that is within less than 10% of the stated amount.

[0054] Although certain embodiments and examples have been described herein, it will be understood by those skilled in the art that many aspects of the delivery systems shown and described in the present disclosure may be differently combined and/or modified to form still further embodiments or acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure. A wide variety of designs and approaches are possible. No feature, structure, or step disclosed herein is essential or indispensable.

[0055] For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be embodied or carried out in a manner that achieves one advantage or a group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. [0056] Moreover, while illustrative embodiments have been described herein, the scope of any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to the examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. Further, the actions of the disclosed processes and methods may be modified in any manner, including by reordering actions and/or inserting additional actions and/or deleting actions. It is intended, therefore, that the specification and examples be considered as illustrative only, with a true scope and spirit being indicated by the claims and their full scope of equivalents.

Claims

WHAT IS CLAIMED IS:

1. A balloon catheter comprising: a catheter shaft; a balloon carried by the catheter shaft; and an asymmetrical expandable element positioned over the balloon, the asymmetrical expandable element comprising a proximal end segment, a distal end segment, and a middle segment therebetween; wherein the proximal end segment and the distal end segment are configured to affix the expandable element to the catheter shaft, the proximal end segment shaped and/or sized differently from the distal end segment; wherein the middle segment comprises a plurality of radial rings and a plurality of longitudinal struts.

2. The balloon catheter of claim 1, wherein the distal end segment is shorter than the proximal end segment.

3. The balloon catheter of claim 1, wherein the distal end segment is shaped and sized differently from the proximal end segment.

4. The balloon catheter of claim 1, wherein each of the proximal end segment and the distal end segment comprises one or more end rings.

5. The balloon catheter of claim 4, wherein the distal end segment comprises a first end ring and a second end ring, the first end ring shaped or sized differently from the second end ring.

6. The balloon catheter of claim 4, wherein the proximal end segment has two end rings and the distal end segment has one end ring.

7. The balloon catheter of claim 4, wherein the proximal end segment comprises a first end ring and a second end ring, the second end ring inverted relative to the first end ring.

8. The balloon catheter of claim 4, wherein each of the one or more end rings has a zigzag pattern.

9. The balloon catheter of claim 8, wherein each of the one or more end rings has two zigzags.

10. The balloon catheter of claim 8, wherein at least one of the end rings in the distal end segment has a greater number of zigzags compared to at least one of the end rings in the proximal end segment.

11. The balloon catheter of claim 1 , wherein the expandable element is capable of bending to a radius of less than or equal to 3.0 mm.

12. The balloon catheter of claim 1, wherein the expandable element is capable of bending to a radius of less than or equal to 1.5 mm.

13. The balloon catheter of claim 1, wherein the balloon has a wall thickness of less than 0.15 inches.

14. The balloon catheter of claim 1, wherein each of the plurality of radial rings comprises a sinusoidal pattern.

15. The balloon catheter of claim 1, wherein each of the plurality of longitudinal struts comprises a sinusoidal pattern.

16. The balloon catheter of claim 1, wherein the expandable element further comprises longitudinal bridges connecting the middle segment to the proximal end segment and the distal end segment.

17. The balloon catheter of claim 16, wherein each of the plurality of longitudinal struts comprises a sinusoidal pattern and each of the longitudinal bridges is straight.

18. The balloon catheter of claim 1, wherein the balloon comprises a proximal balloon taper, a distal balloon taper, and a working length between the proximal balloon taper and the distal balloon taper.

19. The balloon catheter of claim 18, wherein the proximal end segment of the expandable element is positioned over the proximal balloon taper, and the distal end segment of the expandable element is positioned over the distal balloon taper.

20. The balloon catheter of claim 18, wherein the middle segment is positioned over the working length of the balloon.

21. The balloon catheter of claim 1, wherein the expandable element comprises nitinol.

22. The balloon catheter of claim 1, wherein the plurality of radial rings comprises less than or equal to eight radial rings.