Friction pads for deployment and resheathing of endovascular implants
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- STRYKER CORP
- Filing Date
- 2023-07-11
- Publication Date
- 2026-06-08
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical Field]
[0001] The present disclosure relates generally to minimally invasive assemblies used to deliver medical implants, and more particularly to delivery assemblies for delivering medical implants, such as tubular stents and flow diverters, to target implantation sites within a patient's vasculature. [Background technology]
[0002] The use of intravascular implants, such as stents, stent grafts, flow diverters, vascular occlusion devices, and vena cava filters, has become an effective method for treating many types of vascular diseases. Generally, a suitable intravascular implant is inserted into a patient's vascular system and guided through the vascular system to a desired target site using a delivery system. Using currently available delivery systems, virtually any target site in a patient's vascular system, including the coronary arteries, cerebral, and peripheral vessels, can be accessed.
[0003] In a typical intravascular medical device delivery procedure, a delivery catheter is percutaneously introduced into a patient's vasculature over a guidewire and / or through a guide sheath. The open distal end of the delivery catheter is then navigated to the target implantation site using well-known techniques. The intravascular implant is delivered through the lumen of the delivery catheter in a compressed (i.e., reduced diameter) delivery configuration. For example, a pusher member assembly having a pusher member (e.g., a core wire) to which the intravascular implant is temporarily secured can be used to push the intravascular implant through the lumen of the delivery catheter. Once the intravascular implant is positioned adjacent the desired location within the vasculature, it can be deployed from the open distal end of the delivery catheter (e.g., by withdrawing the delivery catheter relative to the intravascular implant) to an expanded (i.e., increased diameter) deployed configuration to engage the inner wall of the blood vessel. A radiopaque marker can be placed at the distal tip of the delivery catheter to estimate the implantation site of the intravascular implant with the aid of medical imaging techniques (e.g., fluoroscopy).
[0004] In one method of delivering an intravascular implant, the intravascular implant is mounted on a balloon, which is then inflated to expand the intravascular implant radially outward, thereby engaging the interior wall of the blood vessel. In another method of delivering an intravascular implant, the intravascular implant is self-expanding, loaded into the lumen of the catheter in a resiliently compressed state, and when the intravascular implant is deployed from the open distal end of the catheter, it resiliently expands without the assistance of a balloon.
[0005] Often, once an intravascular implant is at least partially deployed from a delivery catheter, a physician may determine that the actual implantation site of the intravascular implant is located away from the target implantation site of the intravascular implant and therefore is clinically undesirable. The actual implantation site of the intravascular implant may be clinically undesirable for several reasons. For example, if the intravascular implant is a stent for bridging the neck of an aneurysm or diverting flow from an aneurysm or blood vessel, the stent must be precisely implanted at the target implantation site. If the stent cannot cover the entire aneurysm, if the stent is located in a bend that could cause thrombosis or stroke, or if the stent covers another blood vessel, the intravascular stent must be repositioned. In the case of a self-expanding intravascular implant, if the intravascular implant has not been deployed beyond the point of no return from the delivery catheter (i.e., the point at which the intravascular implant cannot be pulled back into the delivery catheter), the intravascular stent can be resheathed and repositioned within the delivery catheter, thereby allowing the intravascular implant to be redeployed at the target implantation site.
[0006] 1 and 2, one embodiment of a delivery system 1 for delivering an endovascular implant 2 to a target implantation site 3 (shown in FIGS. 3A, 3B, 4A, and 4B) within a blood vessel 4 is shown. The delivery system 1 includes a delivery catheter 5 having an inner lumen 6 and a pusher member assembly 7 disposed within the inner lumen 6 of the delivery sheath 5. The pusher member assembly 7 includes a pusher member 8 and proximal and distal bumpers 9a and 9b attached to the pusher member 8, thereby forming an annular space 10 between the bumpers 9a and 9b. The proximal bumper 9a can function as a radiopaque marker indicating the proximal end of the endovascular implant 2, thereby enabling confirmation of complete deployment of the endovascular implant 2 from the delivery catheter 5. The distal bumper 9b can function as a radiopaque marker indicating a point of no return as the endovascular implant 2 is deployed from the delivery catheter 5, after which the endovascular implant 2 cannot be resheathed within the delivery catheter 5. Other radiopaque markers (not shown) may be positioned at the distal end of the delivery catheter 5 and at other locations along the pusher member 8. The pusher member assembly 7 may further include a protective device 11 disposed at the distal end of the endovascular implant 2. The pusher member assembly 7 further includes an elastomeric friction pad 12 disposed on the pusher member 8 within the annular space 10 between the bumpers 9 a, 9 b. The proximal and distal bumpers 9 a, 9 b serve to retain the friction pad 12 therebetween. The pusher member assembly 7 further includes an atraumatic distal portion 13 attached to the distal end of the pusher member 8.
[0007] The endovascular implant 2 is positioned within the inner lumen 6 of the delivery catheter 5 between the outer surface 14 of the friction pad 12 and the inner surface 15 of the delivery catheter 5. The friction pad 12 is positioned within the inner lumen 6 of the delivery catheter 5 in a compressed state such that the friction pad 12 exerts a radially outward force 16 against the inner surface 17 of the endovascular implant 2, while the inner lumen 6 of the delivery catheter 5 exerts a radially inward force 18 against the outer surface 19 of the endovascular implant 2, as best shown in FIG. 2 . In this manner, the endovascular implant 2 frictionally engages the pusher member assembly 7, such that when the pusher member assembly 7 and the delivery catheter 5 are moved axially relative to one another (e.g., by moving the delivery catheter 5 in a proximal direction 18 while holding the pusher member assembly 7 in a fixed position), the endovascular implant 2 moves integrally with the pusher member assembly 7, enabling the endovascular implant 2 to be deployed into the blood vessel 4 from the distal port 19 of the delivery catheter 5, as shown in FIGS. 3A and 3B .
[0008] Because the tensile strength of the intravascular implant 2 alone is very low, the friction pad 12 not only facilitates deployment of the intravascular implant 2, but also facilitates resheathing of the intravascular implant 2 within the inner lumen 6 of the delivery catheter 5 (e.g., by moving the delivery catheter 5 in the distal direction 21 while holding the pusher member assembly 7 in place), as shown in Figures 4A and 4B. As long as the intravascular implant 2 has not been deployed beyond the point of no return from the delivery catheter 5 (i.e., as long as the distal bumper 9b remains within the inner lumen 6 of the delivery catheter 5, indicating that the entire friction pad 12, which is prone to expand outside the constraints of the delivery catheter 5, is within the inner lumen 6 of the delivery catheter 5), the intravascular implant 2 can be urged by the friction pad 12 to be resheathed back into the delivery catheter 5.
[0009] The performance characteristics of the friction pad 12 should be selected to frictionally engage the endovascular implant 2 to enable both the deployment and resheathing of the endovascular implant 2. For example, the friction pad 12 should have a low lateral bending stiffness combined with a low radial strength (high radial compressibility / expansion) that can be adjusted or calibrated to allow the friction pad 12 to engage the endovascular implant 2 without damaging the endovascular implant 2 or generating particles from the ends of the endovascular implant 2, while avoiding high track / resheathing forces (which could interfere with the deployment, resheathing, or redeployment of the endovascular implant 2). In particular, it is desirable for friction pad 12 to exert a sufficient radial outward force 16 on the inner surface 17 of endovascular implant 2 to frictionally engage endovascular implant 2 without generating excessively high track / resheat forces, but not so great as to create excessive frictional forces between the outer surface of endovascular implant 2 and the inner surface of delivery catheter 5 (which could interfere with movement of endovascular implant 2 within and / or resheathing of endovascular implant 2 into inner lumen 6 of delivery catheter 5). Additionally, it is desirable for friction pad 12 to have sufficiently low lateral flexibility so that friction pad 12 can easily conform to bends in the patient's vasculature, allowing friction pad 12 to more easily follow bends in the patient's vasculature, and facilitating axial movement between pusher member assembly 7 and delivery catheter 5 as friction pad 12 traverses bends in the patient's vasculature. Conventionally, elastomeric friction pads having a low durometer (or modulus of elasticity) provide the friction pad with such sufficiently low bending stiffness and low radial strength.
[0010] However, as shown in FIG. 5 , elastomeric friction pads 12 made from low durometer materials have relatively low column strength and are prone to radially outward bulging (shown by the dotted lines) in the radial direction 22 in response to axial compressive forces 24, such as those caused by significant resistance to movement of the intravascular implant 2 within the inner lumen 6 of the delivery catheter 5 during deployment and / or resheathing of the intravascular implant 2. This radially outward bulging of the friction pad 12 significantly increases the track / resheathing forces of the intravascular implant 2, as well as the potential for particle generation at the ends of the intravascular implant 2. In some cases, the significant track / resheathing forces can cause the friction pad 12 to disengage beyond the proximal bumper 9 a or distal bumper 9 b, thereby rendering the delivery system 1 unusable.
[0011] Therefore, there remains a need to minimize radial outward bulging of the friction pad when there is significant resistance to movement of the endovascular implant within the lumen of the delivery catheter during deployment and / or resheathing of the endovascular implant, while also maintaining the desired radial compressibility / expansion and lateral flexibility of the friction pad. Summary of the Invention
[0012] According to the present invention, an endovascular implant delivery system includes an endovascular implant (e.g., one of a stent, a stent graft, a flow diverter, a vascular occlusion device, and a vena cava filter) having a compressed delivery configuration and an expanded deployed configuration. The endovascular implant includes a tubular implant body and a central implant lumen extending axially through the tubular implant body. The endovascular implant delivery system further includes a delivery catheter having an elongate sheath body and an inner sheath lumen extending axially through the sheath body. The endovascular implant is disposed within the inner sheath lumen when in the compressed delivery configuration. The endovascular implant delivery system further includes a pusher member assembly slidably disposed within the inner sheath lumen. The pusher member assembly includes an elongate pusher member (e.g., a delivery wire) and a friction pad having a radially compressed state and a radially expanded state. The friction pad is disposed within the central implant lumen when in the radially compressed state, and includes a tubular pad body and a central pad lumen extending axially through the tubular pad body. A pusher member is disposed within the central pad lumen.
[0013] In one embodiment, the pusher member assembly further includes a proximal bumper and a distal bumper attached to the pusher member, thereby forming an annular space therebetween with a friction pad disposed within the annular space. In another embodiment, the pusher member assembly and the delivery catheter are axially movable relative to one another, and the friction pad is configured to frictionally engage the endovascular implant as the pusher member assembly and the delivery catheter move axially relative to one another, such that the endovascular implant and the pusher member assembly move axially together to deploy the endovascular implant from the inner sheath lumen to its expanded, deployed configuration. In this embodiment, the friction pad is configured to frictionally engage the endovascular implant as the pusher member assembly and the delivery catheter move axially relative to one another, and such that the endovascular implant and the pusher member assembly move axially together to resheath the endovascular implant and thereby retract it back to its compressed, delivery configuration within the inner sheath lumen while in the at least partially expanded, deployed configuration. The tubular pad body has an elastomeric substrate forming the tubular pad body and at least one adjusting element embedded within the elastomeric substrate and extending axially along the elastomeric substrate. In one embodiment, multiple adjusting elements are circumferentially disposed within the elastomeric substrate. In another embodiment, the tubular pad body is cylindrical. In yet another embodiment, the elastomeric substrate of the friction pad is polyether block amide (PEBA). In yet another embodiment, each of the one or more adjusting elements is elongated. In this case, each of the one or more elongated adjusting elements can extend parallel to the longitudinal axis of the tubular pad body.
[0014] According to a first aspect of the present invention, each of the one or more adjusting elements has mechanical properties different from those of the elastomeric substrate. In one embodiment, the one or more adjusting elements increase the ratio of column strength to radial strength of the tubular pad body. As an example, each of the one or more adjusting elements can have a modulus of elasticity greater than that of the elastomeric substrate, thereby increasing the column strength of the tubular pad body. In this case, each of the one or more adjusting elements can be a solid beam and can have a durometer ranging from 25A to 35D. As another example, each of the one or more adjusting elements can have a modulus of elasticity less than that of the elastomeric substrate, thereby reducing the radial strength of the friction pad. In this case, each of the one or more adjusting elements can be gel or air and can have a durometer greater than 35D.
[0015] According to a second aspect of the present invention, one or more adjusting elements increase the ratio of column strength to radial strength of the tubular pad body. As an example, each of the one or more adjusting elements can have a modulus of elasticity greater than that of the elastomeric substrate, thereby increasing the column strength of the tubular pad body. In this case, each of the one or more adjusting elements can be a solid beam and have a durometer ranging from 25A to 35D. As another example, each of the one or more adjusting elements can have a modulus of elasticity less than that of the elastomeric substrate, thereby reducing the radial strength of the friction pad. In this case, each of the one or more adjusting elements can be gel or air and have a durometer greater than 35D.
[0016] According to a third aspect of the present invention, one or more adjusting elements increase the column strength of the tubular pad body. For example, each of the one or more adjusting elements can have a modulus of elasticity greater than the modulus of elasticity of the elastomeric substrate. In this case, each of the one or more adjusting elements can be a solid beam and can have a durometer in the range of 25A to 35D.
[0017] According to a fourth aspect of the present invention, one or more adjusting elements reduce the radial strength of the tubular pad body. For example, each of the one or more adjusting elements can have a modulus of elasticity less than that of the elastomeric substrate. In this case, each of the one or more adjusting elements can be gel or air and can have a durometer greater than 35D.
[0018] Other and further aspects and features of embodiments of the disclosed invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]
[0019] The drawings illustrate the design and utility of preferred embodiments of the present invention, with similar elements designated by common reference numerals. It should be noted that the drawings are not drawn to scale, and that elements of similar structure or function are designated by similar reference numerals throughout the drawings. It should also be noted that the drawings are intended only to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention, nor are they intended to limit the scope of the invention, which is defined solely by the appended claims and their equivalents. Furthermore, exemplary embodiments of the disclosed invention need not possess all of the disclosed aspects or advantages. Furthermore, an aspect or advantage discussed in connection with a particular embodiment of the disclosed invention is not necessarily limited to that embodiment, and may be implemented in any other embodiment, even if not so depicted. To better understand how the above-mentioned and other advantages and objectives of the invention are obtained, a more particular description of the invention, briefly described above, will be rendered with reference to specific embodiments thereof, as illustrated in the accompanying drawings. The invention will be described and explained with additional specificity and detail using the accompanying drawings, the understanding that these drawings illustrate only typical embodiments of the invention and are therefore not to be considered limiting of its scope.
[0020] [Figure 1]FIG. 1 is a longitudinal cross-sectional view of a prior art delivery system for delivering an intravascular implant to a patient. [Figure 2] FIG. 2 is a cross-sectional view of the delivery system of FIG. 1 taken along line 2-2. [Figure 3] 3A and 3B are plan views illustrating a prior art method of deploying an intravascular implant within a patient's vasculature using the delivery system of FIG. [Figure 4] 4A and 4B are plan views illustrating a prior art method of resheathing an intravascular implant using the delivery system of FIG. [Figure 5] FIG. 5 is a perspective view showing an elastomeric friction pad of a prior art delivery system, particularly showing the friction pad expanding radially in response to a compressive force. [Figure 6] FIG. 6 is a plan view of one embodiment of an endovascular implant delivery system constructed in accordance with the present invention. [Figure 7] FIG. 7A is a plan view of the distal end of the endovascular implant delivery system of FIG. 6. FIG. 7B is a cutaway plan view of the distal end of a pusher member assembly of the endovascular implant delivery system of FIG. 7A. FIG. 7C is a cutaway perspective view of the pusher member assembly of FIG. 7B. FIG. 7D is a diagram of an endovascular implant carried by the pusher member assembly of FIG. 7B. FIG. 7E is a close-up plan view of the distal tip of the pusher member assembly of FIG. 7B. FIG. 7F is a close-up plan view of a portion of the endovascular implant delivery system of FIG. 7A taken along line 7F-7F. FIG. 7G is a close-up plan view of the distal tip of the endovascular implant delivery system of FIG. 7A, particularly showing the endovascular implant during deployment. FIG. 7H is a cross-sectional view of the endovascular implant delivery system of FIG. 7F taken along line 7H-7H. FIG. 7I is a cross-sectional view of the endovascular implant delivery system of FIG. 7G taken along line 7I-7I. [Figure 8]Figure 8A is a perspective view of a friction pad of the pusher member assembly of Figure 7B, particularly illustrating how the diameter of the friction pad decreases in response to a radial compressive force. Figure 8B is a perspective view of the friction pad of Figure 8A, particularly illustrating how the diameter of the friction pad does not increase in response to an axial compressive force. [Figure 9] Figure 9 is a perspective view of one embodiment of the friction pad of Figure 8A. Figure 9A is a cross-sectional view of the friction pad of Figure 9 taken along line 9A-9A. [Figure 10] Figure 10 is a perspective view of one embodiment of the friction pad of Figure 8A. Figure 10A is a cross-sectional view of the friction pad of Figure 10 taken along line 10A-10A. [Figure 11] Figure 11 is a perspective view of one embodiment of the friction pad of Figure 8A. Figure 11A is a cross-sectional view of the friction pad of Figure 11 taken along line 11A-11A. [Figure 12] Figure 12 is a perspective view of one embodiment of the friction pad of Figure 8A. Figure 12A is a cross-sectional view of the friction pad of Figure 12 taken along line 12A-12A. [Figure 13] Figure 13 is a perspective view of one embodiment of the friction pad of Figure 8A. Figure 13A is a cross-sectional view of the friction pad of Figure 13 taken along line 13A-13A. Figure 13B is a cross-sectional view of the friction pad of Figure 13 taken along line 13B-13B. DETAILED DESCRIPTION OF THE INVENTION
[0021] 6 and 7A-7I, one embodiment of an implant delivery system 100 constructed in accordance with an embodiment of the present invention is described. The implant delivery system 100 generally includes an intravascular implant 102, a delivery catheter 104 for delivering the intravascular implant 102 to a target site within a patient's vasculature, and a pusher member assembly 106 (FIGS. 7A and 7D) slidably disposed within the delivery catheter 104 for coaxially carrying the intravascular implant 102.
[0022] Implant delivery system 100 can be used in an "over-the-wire" configuration, where delivery catheter 104 is introduced into a patient over a previously introduced guidewire (not shown), with delivery catheter 104 extending the entire length of the guidewire (not shown). Alternatively, implant delivery system 100 can be used in a "rapid-exchange" configuration, where a guidewire (not shown) extends from a guidewire port (not shown) through only a distal portion of delivery catheter 104. In other alternative embodiments, implant delivery system 100 can be introduced into a patient after the guidewire is withdrawn, leaving behind a guide sheath, for delivery catheter 104 to navigate through the patient's vasculature within the guide sheath.
[0023] 7A and 7D , the endovascular implant 102 may take the form of, for example, a stent, stent-graft, flow diverter, vascular occlusion device, vena cava filter, etc. The endovascular implant 102 typically comprises a tubular implant body 108 having a proximal portion 110 and a distal portion 112, and a central implant lumen 114 extending axially completely through the tubular implant body 108. The tubular implant body 108 is constructed of a resilient material such that the endovascular implant 102 assumes a compressed delivery configuration when radially constrained within the delivery catheter 104 and automatically assumes an expanded deployed configuration when released from the constraints of the delivery catheter 104 (i.e., when the endovascular implant 102 is deployed from the delivery catheter 104). The tubular implant body 108 can be constructed from a variety of biocompatible materials, such as, for example, stainless steel, Elgiloy, nickel, titanium, Nitinol, shape memory polymers, or combinations thereof, and can be constructed using well-known techniques, such as by etching or cutting a pattern from a tube or sheet of stent material, or by braiding / weaving one or more wires or ribbons into the desired shape and pattern. The endovascular implant 102 can include additional components welded, bonded, or otherwise engaged to one another, and can optionally include non-porous, non-permeable biocompatible materials or coverings, etc. The endovascular implant 102 can optionally include a bioactive or therapeutic agent carried or coated on the interior or exterior surface of the tubular implant body 108.
[0024] The delivery catheter 104 has a length of, for example, about 50 cm to 300 cm, typically about 60 cm to 200 cm. The delivery catheter 104 is configured to access a body cavity, such as a blood vessel (e.g., an intracranial vein or a carotid artery), for a desired treatment at a target site. For example, the target site may be in a small-diameter vessel having a lumen diameter of 2 to 12 mm and accessible via a tortuous vascular pathway including multiple vascular bends and multiple vascular branches. In such cases, the delivery catheter 12 has an appropriately small diameter and flexible structure.
[0025] The delivery catheter 104 comprises an elongate sheath body 116 having a proximal portion 118 and a distal portion 120, and an inner sheath lumen 122 (best shown in FIG. 7A ) extending axially completely through the sheath body 116. The inner sheath lumen 122 terminates at a distal port 124 at the end of the distal portion 120 of the sheath body 116. The proximal portion 118 of the sheath body 116 remains outside the patient and is accessible to the operator during use of the implant delivery system 100, while the distal portion 120 of the sheath body 116 is sized and dimensioned to reach remote locations in the vasculature to deliver the endovascular implant 102 to a target location within the patient, such as an occlusion in a blood vessel, a vessel adjacent an aneurysm neck, a branch vessel, etc. The inner sheath lumen 122 is sized to accommodate longitudinal movement of the radially retracted endovascular implant 102 and the pusher member assembly 106.
[0026] The delivery catheter 104 comprises a proximal adapter 126 attached to the proximal portion 118 of the sheath body 116. The proximal adapter 126 includes a central bore 128 (shown in phantom) that communicates with the internal lumen 122 of the sheath body 116. The central bore 128 terminates in a proximal port 130 to allow loading of the pusher member assembly 106 into the delivery catheter 104. The proximal adapter 126 further comprises at least one fluid port 132 in fluid communication with the internal lumen 122 for introducing fluid into the delivery catheter 104 to hydrate the pusher member assembly 106 and the endovascular implant 102. Additionally, the delivery catheter 104 includes a tapered radiopaque marker 134 located on the distal portion 120 of the sheath body 116 proximate the distal port 124, which allows the location of the distal tip of the delivery catheter 104 within the patient's vasculature or relative to a partially or fully deployed endovascular implant 102 to be identified using medical imaging techniques (e.g., fluoroscopy). Additionally, the delivery catheter 104 includes an atraumatic distal tip 136 attached to the distal tip of the sheath body 116.
[0027] The delivery catheter 104 can include one or more regions along its length, or multiple regions, having different configurations and / or properties. For example, the distal portion 120 of the sheath body 116 can have a smaller outer diameter than the outer diameter of the proximal portion 118, thereby reducing the profile of the distal portion 120 and facilitating navigation through tortuous vasculature. Additionally, the distal portion 120 can be more flexible than the proximal portion 118. Typically, the proximal portion 118 is formed from a stiffer material than the distal portion 120, allowing the proximal portion 118 to have sufficient pushability for advancement through a patient's vasculature, while the distal portion 120 is formed from a more flexible material, allowing the distal portion 120 to remain flexible and more easily track over a guidewire to access remote locations in tortuous regions of the vasculature. In some cases, the proximal portion 118 can include a reinforcing layer, such as a braided or coiled layer, to enhance the pushability of the delivery catheter 104. The delivery catheter 104 may include a transition region between the proximal portion 118 and the distal portion 120 .
[0028] The sheath body 116 can be constructed of a suitable polymeric material, metal, and / or alloy, such as polyethylene, stainless steel, or other suitable biocompatible material or combinations thereof. Examples of suitable metals and metal alloys include stainless steels, such as 304V, 304L, and 316L stainless steel, nickel-titanium alloys, such as superelastic (i.e., pseudoelastic) or linear elastic nitinol, nickel-chromium alloys, nickel-chromium-iron alloys, cobalt alloys, tungsten or tungsten alloys, tantalum or tantalum alloys, gold or gold alloys, MP35-N (including a composition consisting of approximately 35% Ni, 35% Co, 20% Cr, 9.75% Mo, max 1% Fe, max 1% Ti, max 0.25% C, max 0.15% Mn, and max 0.15% Si), or other suitable metals, or combinations or alloys thereof. Examples of suitable polymers include, but are not limited to, polyoxymethylene (POM), polybutylene terephthalate (PBT), polyether block ester, polyether block amide (PEBA), fluorinated ethylene propylene (FEP), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysulfone, nylon, perfluoro(propyl vinyl ether) (PFA), polyether ester, polymer / metal composites, or mixtures, blends, or combinations thereof.
[0029] The sheath body 116 may include a braided shaft construction of stainless steel flat wire encapsulated or surrounded by a polymer coating. As a non-limiting example, HYDROLENE is a polymer coating used to cover the outer portion of the sheath body 116. Of course, the implant delivery system 100 is not limited to a particular construction or type of delivery catheter 104, and other constructions known to those skilled in the art may be used for the sheath body 116 of the delivery catheter 12. The inner sheath lumen 122 may advantageously be coated with a lubricious coating (not shown), such as PTFE, to reduce frictional forces between the sheath body 116 and the pusher member assembly 106 and endovascular implant 102 during axial movement within the inner lumen 122.
[0030] The pusher member assembly 114 is slidably disposed within the inner lumen 122 of the delivery catheter 104, and the endovascular implant 102 is coaxially disposed between the delivery catheter 104 and the pusher member assembly 114. The pusher member assembly 114 is configured to engage the endovascular implant 102 when the pusher member assembly 114 is moved axially relative to the delivery catheter 104 to deliver the endovascular implant 102 to a target site in a patient or to resheath the endovascular implant 102 back into the delivery catheter 104. The interface between the pusher member assembly 114 and the endovascular implant 102 is described in further detail below.
[0031] The pusher member assembly 114 generally includes an elongated pusher member in the form of a delivery wire 138 having a proximal portion 140 extending proximally from the proximal adapter 126 of the delivery catheter 104 that can be grasped by a physician to move the pusher member assembly 114 axially within the internal lumen 122 of the delivery catheter 104, a distal portion 142 that carries the intravascular implant 102, and a transition portion 144 between the proximal portion 140 and the distal portion 142 to facilitate tracking of the pusher member assembly 114 within the internal lumen 122 of the delivery catheter 104.
[0032] The delivery wire 138 can be constructed of a conventional guidewire, a torqueable cable tube, or a hypotube. In either case, there are numerous materials that can be used for the delivery wire 138 to achieve the desired properties commonly associated with medical devices. Some examples include metals, metal alloys, polymers, metal-polymer composites, or any other suitable materials (e.g., nickel-titanium alloys, stainless steel, nickel-titanium alloy and stainless steel composites). In some cases, the delivery wire 138 can be made of the same material along its length, or in some embodiments, can include portions or sections made of different materials. In some embodiments, the materials used to construct the delivery wire 138 are selected to impart various flexibility and stiffness characteristics to different portions of the delivery wire 138. For example, the proximal portion 140, distal portion 142, and transition portion 144 of the delivery wire 138 can be formed of different materials, e.g., materials having different elastic moduli, thereby providing differential flexibility. For example, the proximal portion 140 may be formed of stainless steel, while the distal portion 142 and intermediate portion 144 may be formed of a nickel-titanium alloy. However, any suitable material or combination of materials may be used for the delivery wire 138, as desired.
[0033] In the illustrated embodiment, pusher member assembly 106 further includes a coil 146 secured to transition portion 144 of delivery wire 138. The diameter of transition portion 144 with coil 146 is closely toleranced to the diameter of inner sheath lumen 122 of delivery catheter 104, thereby facilitating stable tracking of pusher member assembly 106 through inner sheath lumen 122, while coil 146 provides columnar support to pusher member assembly 106 just proximal to distal portion 142 where endovascular implant 102 is positioned while maintaining lateral flexibility of pusher member assembly 106. The distal portion 142 has a smaller diameter, which can provide a platform on which the intravascular implant 102 in its compressed delivery configuration and other components of the pusher member assembly 106 (described below) are positioned, so that the outer diameter of the compressed intravascular implant 102 and the outer diameter of the distal portion of the pusher member assembly 106 are also toleranced closely to the diameter of the inner lumen 122 of the delivery catheter 104 [is this correct?].
[0034] The pusher member assembly 106 further includes an atraumatic distal tip member 148 attached to the distal end of the delivery wire 138. The distal tip member 148 enables vascular selection and facilitates guiding the implant delivery system 100 to the target implantation site. The distal tip member 148 can be pre-shaped to assume a curved shape (a J-shape in a preferred embodiment) when unconstrained and a straight shape when constrained. Alternatively, the distal tip member 148 can be flexible, for example, comprised of a flexible coil member. The distal tip member 148 can optionally be radiopaque to aid in visualization using medical imaging techniques (e.g., fluoroscopy). The pusher member assembly 106 further includes a protection device 150 attached to the delivery wire 138 via one or more locking members 152 to cover a distal portion of the endovascular implant 102.
[0035] The pusher member assembly 106 further includes a proximal bumper 154 attached to the distal portion 142 of the delivery wire 138 just distal to the transition section 144, and a distal bumper 156 attached (e.g., via epoxy bonding) to the distal portion 142 of the delivery wire 138 distal to the proximal bumper 154, thereby forming an annular space 158 between the bumpers 154, 156. The bumpers 154, 156 may be constructed of a suitable biocompatible material, such as stainless steel or nitinol. Each of the bumpers 154, 156 is disc-shaped and sized to slide within the inner sheath lumen 122 of the delivery catheter 104, although in alternative embodiments, the bumpers 154, 156 may have any suitable shape. In the illustrated embodiment, the diameter of the proximal bumper 154 is toleranced closely to the diameter of the inner sheath lumen 122, while the distal bumper 156 has a distally tapered tip to minimize tissue trauma. The outer surfaces of the bumpers 154, 156 can be provided with low friction depending on the material from which they are formed. Alternatively or additionally, the outer surfaces of the bumpers 154, 156 can be coated with a lubricious coating, such as polytetrafluoroethylene (PTFE), to allow the bumpers 154, 156 to move easily through the inner sheath lumen 122.
[0036] 7C , pusher member assembly 106 further includes a friction pad 162 coaxially disposed about delivery wire 138 within an annular space 158 between bumpers 154, 156. In particular, friction pad 162 includes a tubular pad body 164 having a proximal portion 166 and a distal portion 168, and a central pad lumen 170 extending axially through tubular pad body 164 and within which delivery wire 138 is disposed. A distal face of proximal bumper 154 serves to abut proximal portion 166 of friction pad 162, such that friction pad 162 moves axially with delivery wire 138 as pusher member assembly 106 moves distally relative to delivery sheath 104 (e.g., during deployment of endovascular implant 102 from delivery catheter 104). In contrast, the proximal surface of the distal bumper 154 functions to abut the distal portion 168 of the friction pad 162, causing the friction pad 162 to move axially with the delivery wire 138 when the pusher member assembly 106 moves proximally relative to the delivery sheath 104 (e.g., during resheathing of the intravascular implant 102 within the delivery catheter 104).
[0037] One or both of the bumpers 154, 156 can be radiopaque and thereby also serve as markers to assist in locating the position of the endovascular implant 102 relative to the delivery catheter 104 using medical imaging techniques (e.g., fluoroscopy). For example, such a radiopaque proximal bumper 154 can indicate the proximal end of the endovascular implant 102 so that full deployment of the endovascular implant 102 from the delivery catheter 104 is confirmed, while such a radiopaque distal bumper 156 can indicate a point of no return as the endovascular implant 102 is deployed from the delivery catheter 104, after which the endovascular implant 102 cannot be resheathed within the delivery catheter 104. To that end, the bumpers 154, 156 can be constructed of a suitable radiopaque material, such as, for example, platinum, gold, tungsten, or alloys thereof, or other metals. The pusher member assembly 106 may optionally include additional radiopaque elements anywhere along its length to facilitate visualization using medical imaging techniques (e.g., fluoroscopy).
[0038] 7F and 7H , in its compressed delivery configuration, the endovascular implant 102 is disposed within the inner lumen 122 of the delivery catheter 104 in coaxial alignment with the distal portion of the pusher member assembly 106. In the illustrated embodiment, the endovascular implant 102 extends from the proximal end of the friction pad 162 to the distal tip of the delivery wire 138, such that the proximal portion 110 of the tubular implant body 108 of the endovascular implant 102 and the friction pad 162 are coaxially disposed, i.e., the proximal portion 110 of the tubular implant body 108 is disposed between the outer surface 172 of the friction pad 162 and the inner surface 174 of the delivery catheter 104. While in the illustrated embodiment, the endovascular implant 102 extends from only a portion of the friction pad 162 to the distal tip of the delivery wire 138, it should be understood that the friction pad 162 may extend along the entire friction pad 162 to the distal tip of the delivery wire 138 or to a point proximal to the distal tip of the delivery wire 138, or alternatively, the endovascular implant 102 may extend along the entire friction pad 162. In contrast, as shown in FIGS. 7G and 7I, in its expanded, deployed configuration, the endovascular implant 102 is not disposed within the inner lumen 122 of the delivery catheter 104, but may remain coaxially disposed with the distal portion of the pusher member assembly 106.
[0039] Friction pad 162 is configured to cooperate with endovascular implant 102 such that pusher member assembly 106 engages endovascular implant 102 when endovascular implant 102 is in a compressed delivery configuration ( FIGS. 7F and 7G ) within inner lumen 122 of delivery catheter 104, and releases endovascular implant 102 when endovascular implant 102 is in an expanded deployed configuration ( FIGS. 7G and 71 ) outside inner lumen 122 of delivery catheter 104. To that end, friction pad 162 is elastically deformable and capable of alternately transitioning between a radially compressed state ( FIGS. 7F and 7G ) and a radially expanded state ( FIG. 7H ). The cross-sectional dimension of the friction pad 162 when in a radially expanded state (e.g., diameter d1 shown in FIG. 7I ) is larger than the cross-sectional dimension of the inner lumen 114 of the endovascular implant 102 when in a compressed delivery configuration within the inner lumen 122 of the delivery catheter 104 (e.g., diameter d2 shown in FIG. 7H ), thereby enabling the friction pad 162 to reliably frictionally engage the endovascular implant 102 when in a radially compressed state within the inner lumen 114 of the compressed endovascular implant 102. In contrast, the cross-sectional dimension of the friction pad 162 when in a radially expanded state (e.g., diameter d1 shown in FIG. 7I ) is smaller than the cross-sectional dimension of the inner lumen 114 of the endovascular implant 102 when in an expanded, deployed configuration outside the inner lumen 122 of the delivery catheter 104 (e.g., diameter d3 shown in FIG. 7I ), thereby enabling the friction pad 162 to reliably release the endovascular implant 102 when in a radially expanded state within the inner lumen 114 of the expanded endovascular implant 102.
[0040] In particular, as best shown in FIG. 7H , when the endovascular implant 102 is in a compressed delivery configuration within the internal sheath lumen 122, the friction pad 162 is positioned within the central implant lumen 114 of the endovascular implant 102 in a radially compressed state (i.e., coaxially positioned between the delivery wire 138 and the endovascular implant 102), such that the friction pad 162 exerts a radially outward force 176 against an inner surface 178 of the endovascular implant 102, while the internal sheath lumen 122 exerts a radially inward force 180 against an outer surface 182 of the endovascular implant 102. In this manner, the proximal portion 162 of the intravascular implant 102 is frictionally engaged (i.e., gripped) by the pusher member assembly 106, such that when the pusher member assembly 106 and the delivery catheter 104 are moved axially relative to one another (e.g., by moving the delivery catheter 104 proximally while holding the pusher member assembly 106 in a fixed position), the entire intravascular implant 102 moves integrally with the pusher member assembly 106, causing the intravascular implant 102 to be deployed into an expanded, deployed configuration within the blood vessel from the distal port 124 of the delivery catheter 104.
[0041] 7I , when the endovascular implant 102 is in the expanded, deployed configuration outside the inner lumen 122 of the delivery catheter 104, the friction pad 162 is coaxially disposed between the delivery wire 138 and the endovascular implant 102 in a radially expanded state, but does not exert a radially outward force against the inner surface 178 of the endovascular implant 102. As a result, the endovascular implant 102 is no longer frictionally engaged (i.e., gripped) by the pusher member assembly 106, such that as the pusher member assembly 106 and the delivery catheter 104 are moved axially relative to one another (e.g., by moving the pusher member assembly 106 proximally while holding the delivery catheter 104 in place), the pusher member assembly 106 moves independently of the deployed endovascular implant 102, leaving the deployed endovascular implant 102 in place when the pusher member assembly 106 is fully retracted into the distal port 124 of the delivery catheter 104.
[0042] 7A-7D , the friction pad 162 not only facilitates deployment of the endovascular implant 102, but also serves to facilitate resheathing of the stent 102 within the inner lumen 122 of the delivery catheter 104 (e.g., by moving the delivery catheter 104 distally while holding the pusher member assembly 106 in place). As long as the endovascular implant 102 has not been deployed beyond the point of no return from the delivery catheter 104 (i.e., as long as the distal bumper 156 remains within the inner lumen 122 of the delivery catheter 104, indicating that the entire expandable friction pad 162 is within the inner lumen 122 of the delivery catheter 104 outside the constraints of the delivery catheter 104), the endovascular implant 102 can be urged by the friction pad 162 to be resheathed back to its compressed delivery configuration within the delivery catheter 104.
[0043] In the illustrated embodiment, the friction pad 162 is generally cylindrical, although in alternative embodiments, the friction pad 162 can have a non-circular cross-sectional shape (e.g., octagonal). In the illustrated embodiment, the friction pad 162 is constructed from an elastomeric substrate. Such an elastomeric substrate may be a high-friction polymer, such as, for example, polyether block amide (PEBA), to facilitate frictional engagement with the endovascular implant 102. Alternatively, other types of polymers suitable for the elastomeric substrate include, but are not limited to, polyoxymethylene (POM), polybutylene terephthalate (PBT), polyether block ester, fluorinated ethylene propylene (FEP), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysulfone, nylon, perfluoro(propyl vinyl ether) (PFA), polyether ester, polymer / metal composites, or mixtures, blends, or combinations thereof.
[0044] In an alternative embodiment, the friction pad 162 can be coated with a high-friction, adhesive material. In another alternative embodiment, the outer surface of the friction pad 162 can be modified to provide the friction pad 162 with a desired resistance for frictional engagement with the endovascular implant 102. For example, at least a portion of the outer surface of the friction pad 162 can be roughened by any suitable technique, such as grit blasting, plasma treatment, or knurling, or lateral grooves, protrusions, or rings can be formed on at least a portion of the outer surface of the friction pad 162.
[0045] In the illustrated embodiment, a single friction pad 162 is disposed in the annular space 158 between the bumpers 154, 156, although in alternative embodiments, multiple friction pads may be disposed in the annular space 158 between the bumpers 154, 156. Additionally, although the friction pad 162 is designed to frictionally engage uniformly with the entire length of the endovascular implant 102 between the bumpers 154, 156, one or more friction pads 162 may frictionally engage non-uniformly with only a portion of the endovascular implant 102 between the bumpers 154, 156.
[0046] As previously mentioned, the tubular pad body 164 desirably has a relatively low radial strength so that the friction pad 162 is radially compressible / expandable to the extent that it applies a radially outward force large enough to frictionally engage the intravascular implant 102, a relatively low bending stiffness so that the friction pad 162 more easily passes through bends in the patient's vasculature, and a relatively high column strength so that radially outward bulging of the tubular pad body 164 is prevented, or at least minimized, when significant resistance to movement of the intravascular implant 102 within the inner lumen 122 of the delivery catheter 104 exists during deployment and / or resheathing of the intravascular implant 102.
[0047] Additionally, the column strength of the tubular pad body 164 can be characterized by the axial strain (i.e., the change in length of the tubular pad body 164 in the presence of a unit axial force (or axial stress) divided by the length of the tubular pad body 164 in the absence of an axial force (or axial stress)), while the radial strength of the tubular pad body 164 can be characterized by the radial strain (i.e., the change in diameter of the tubular pad body 164 in the presence of a unit radial force (or radial stress) divided by the diameter of the tubular pad body 164 in the absence of a radial force (or radial stress)).
[0048] Importantly, the friction pads 162 are configured to have sufficiently high column strength and sufficiently low radial strength and bending stiffness so that, even if there is significant resistance to relative movement of the endovascular implant 102 with respect to the lumen 122 of the delivery catheter 104 during deployment and / or resheathing of the endovascular implant 102, radial outward bulging of the friction pads 162 is minimized while allowing the friction pads 162 to frictionally engage the endovascular implant 102 and easily advance through the patient's vasculature.
[0049] 8A and 8B , the tubular pad body 164 of the friction pad 162 includes an elastomeric substrate 184 that forms the friction pad 162 and at least an adjustment element 186 (shown as multiple adjustment elements 186) extending axially within the elastomeric substrate 184. The adjustment element 186 may be embedded within the elastomeric substrate 184 using any suitable process, such as, for example, an extrusion process, an overmolding process, or a lamination process. In the illustrated embodiment, the adjustment element 186 is elongated and extends in a direction parallel to the longitudinal axis of the tubular pad body 164. However, it should be noted that the adjustment element 186 may also extend obliquely relative to the longitudinal axis of the tubular pad body 164 (e.g., at an angle of no more than 15 degrees from the longitudinal axis of the tubular pad body 164). As described in more detail below, the adjusting element 186 serves to adjust the mechanical properties of the tubular pad body 164, and thus the mechanical properties of the material comprising the adjusting element 186 are substantially different from the mechanical properties of the material comprising the elastomeric substrate 184.
[0050] Importantly, the adjustment element 186 is configured to increase the column strength of the tubular pad body 164 without excessively increasing the radial strength of the tubular pad body 164 (i.e., the radial strength of the tubular pad body 164 is not so great that the friction pad 162 is no longer elastic enough to have sufficient radially outward force to frictionally engage the endovascular implant 102) and without increasing the bending stiffness of the tubular pad body 164, or to decrease the radial strength or lateral bending stiffness of the tubular pad body 164 without excessively decreasing the column strength of the tubular pad body 164 (i.e., the column strength of the tubular pad body 164 is not so weak that the friction pad 162 bulges radially outward even when there is significant resistance to movement of the endovascular implant 102 within the internal lumen 122 of the delivery catheter 104 during deployment and / or resheathing of the endovascular implant 102).
[0051] In one embodiment, the tuning elements 186 increase the ratio of column strength to radial strength of the tubular pad body 164 (i.e., the ratio of column strength to radial strength of the tubular pad body 164 with the axially extending elements 186 is substantially greater than the ratio of column strength to radial strength of the tubular pad body 164 when the axially extending elements or elements are replaced with the same elastomeric material 184 that would have occupied the space within the tubular pad body 164 without the axially extending elements 186). It should be understood that because the lateral bending stiffness of the tubular pad body 164 is directly related to the radial strength of the tubular pad body 164, as the ratio of column strength to radial strength of the tubular pad body 164 increases, the ratio of column strength to radial strength of the tubular pad body 164 also increases, much in the same way that a solid cylinder constructed of a rigid material significantly increases the lateral bending stiffness of a solid cylinder.
[0052] Preferably, the number, cross-sectional size, cross-sectional shape, orientation, and composition of the adjusting elements 186 are selected to maximize the volume of the elastomeric substrate 184. That is, the total volume of adjusting elements 186 required to achieve a desired ratio of column strength to radial strength of the tubular pad body 164 should be minimized to minimize any adverse effects on the radial strength (and bending stiffness) of the tubular pad body 164 when the adjusting elements 186 serve to increase the column strength of the tubular pad body 164, or to minimize any adverse effects on the column strength of the tubular pad body 164 when the adjusting elements 186 serve to decrease the radial strength (and bending stiffness) of the tubular pad body 164. In other words, the adjusting elements 186 are designed to adjust the mechanical properties (i.e., column strength and radial strength) of the tubular pad body 164, as opposed to dominating the mechanical properties of the tubular pad body 164. Therefore, it is preferred to minimize the number and cross-sectional size of the adjusting elements 186 as much as possible. It is also preferred to minimize the thickness of the cross-sectional shape of the adjusting elements 186 as much as possible. It should be understood that the greater the difference between the mechanical properties of the material comprising the adjusting element 186 and the mechanical properties of the material comprising the elastomeric substrate 184, the greater the adjustment of the tubular pad body 164 by the adjusting element 186, and therefore the cross-sectional size of the adjusting element 186 can be reduced.
[0053] As shown in Figure 8A, adjustment of tubular pad body 164 by adjustment element 186 causes the diameter of friction pad 162 to decrease by a desired amount (e.g., from diameter d1 to diameter d2) in response to radial compressive force 188 (i.e., a radial compressive force corresponding to a radially inward force 180 imparted by inner sheath lumen 122 of delivery catheter 104 against outer surface 182 of endovascular implant 102, shown in Figure 7H). In contrast, as shown in Figure 8B, the length or diameter (e.g., diameter d2) of friction pad 162 does not substantially change in response to axial compressive force 190 (i.e., a force created by the significant resistance to relative movement of endovascular implant 102 with respect to lumen 122 of delivery catheter 104 during deployment and / or resheathing of endovascular implant 102).
[0054] Referring to FIG. 9, the tubular pad body 164a of one embodiment of the friction pad 162a includes three elongated adjustment elements 186a that extend completely axially through the elastomeric substrate 184. The adjustment elements 186a are circumferentially disposed within the elastomeric substrate 184, and specifically, are circumferentially spaced 120 degrees apart from one another. While the tubular pad body 164a includes three adjustment elements 186a, it should be understood that the tubular pad body 164a may include any number of adjustment elements 186a. However, the adjustment elements 186a are preferably circumferentially spaced equally apart from one another. Alternatively, for example, if the tubular pad body 164a includes four adjustment elements 186a, the adjustment elements are preferably circumferentially spaced 90 degrees apart from one another. In the illustrated embodiment, each of the adjustment elements 186a is cylindrical (i.e., has a circular cross-section), as shown in FIG. 9A.
[0055] In alternative embodiments, one or more of the adjusting elements 186a can have other cross-sections, such as triangular, rectangular, oval, elliptical, etc. Additionally, while in the illustrated embodiment the cross-sectional size of each of the adjusting elements 186a is uniform along the length of the respective adjusting element, the cross-sectional size of one or more of the adjusting elements 186a may vary along the length of the respective adjusting element. Additionally, while all of the adjusting elements 186a are depicted as having the same cross-sectional size, the cross-sectional sizes of the adjusting elements 186a may differ from one another.
[0056] It should be appreciated that the cross-sectional size and composition of the adjusting element 186a can be selected to provide a desired ratio of column strength to radial strength (or bending stiffness) of the tubular pad body 164a. That is, a larger cross-sectional size and / or a higher durometer (or modulus of elasticity) of the adjusting element 186a will result in a higher ratio of column strength to radial strength of the tubular pad body 164a, while a smaller cross-sectional size and / or a lower durometer (or modulus of elasticity) of the adjusting element 186a will result in a lower ratio of column strength to radial strength of the tubular pad body 164a.
[0057] 10 , the tubular pad body 164b of another embodiment of a friction pad 162b differs from the tubular pad body 164a of the friction pad 162a of FIG. 9 in that, instead of including an elongated adjustment element 186a that extends completely through the elastomeric substrate 184, the tubular pad body 164b includes three elongated adjustment elements 186b that extend only partially axially through the elastomeric substrate 184. Thus, the adjustment elements 186b do not extend axially all the way to the proximally-facing surface 192 of the tubular pad body 164b or all the way to the distally-facing surface 194 of the tubular pad body 164b. Similar to the adjustment elements 186a of the tubular pad body 164a shown in FIG. 9A , each of the adjustment elements 186b of the tubular pad body 164b is cylindrical (i.e., has a circular cross-section), as shown in FIG. 10A .
[0058] 11 , a tubular pad body 164c of yet another embodiment of a friction pad 162c differs from the tubular pad body 164a of the friction pad 162a of FIG. 9 in that instead of including a single elongated adjusting element 186a extending axially into the elastomeric substrate 184 at each circumferential position, the tubular pad body 164c includes a series of elongated adjusting elements 186c extending axially into the elastomeric substrate 184 at each circumferential position. In the illustrated embodiment, three adjusting elements 186c (two relatively short adjusting elements 186c sandwiching a relatively long central adjusting element 186c) extend axially within the elastomeric substrate 184 at each circumferential position. Like the adjusting element 186a of the tubular pad body 164a shown in FIG. 9A , each of the adjusting elements 186c of the tubular pad body 164c is cylindrical (i.e., has a circular cross-section), as shown in FIG. 11A .
[0059] 12, a tubular pad body 164d of yet another embodiment of a friction pad 162d differs from the tubular pad body 164a of the friction pad 162a of FIG. 9 in that instead of including an elongated adjusting element 186a having a circular cross-section, the tubular pad body 164d includes an elongated adjusting element 186d having an arcuate cross-section, as best shown in FIG. 12A. This allows the arcuate cross-sectional shape of the elongated adjusting element 186d to better conform to the outer periphery of the elastomeric substrate 184. This allows the volume of the elongated adjusting element 186d to be minimized, thereby maximizing the volume of the elastomeric substrate 184.
[0060] 13, a tubular pad body 164e of yet another embodiment of a friction pad 162e differs from the tubular pad body 164d of the friction pad 162a of FIG. 9 in that the tubular pad body 164e includes an adjustment element 186e that is not elongated. Furthermore, as best shown in FIG. 13A, the thickness of the arcuate cross section of the adjustment element 186e is reduced to compensate for the shortened length of the adjustment element 186e. Furthermore, the adjustment elements 186e are disposed only at the ends of the elastomeric substrate 184, and are absent from the central portion of the elastomeric substrate 184. As a result, only the ends of the tubular pad body 164e are adjusted by the adjustment element 186e, and the central portion of the tubular pad body 164e remains unadjusted, as shown in FIG. 13B, while the ends of the tubular pad body 164e are adjusted.
[0061] The composition of the adjusting element 186 of the tubular pad body 164 shown in Figures 9-13 depends on the composition of the elastomeric substrate 184. For example, the elastomeric substrate 184 may have a relatively low durometer (e.g., in the range of 25A to 35D) and thus a relatively low modulus of elasticity (Young's modulus). Examples of materials for the elastomeric substrate 184 include Piothane®, Isothane®, Cronoflex®, Cronoprene®, silicone, Pebax®, Versaflex®, and Picoflex®.
[0062] In this case, such an elastomeric substrate 184 may provide sufficiently low radial strength (and thus sufficiently high radial expandability / compressibility) to frictionally engage the endovascular implant 102, and sufficiently low bending stiffness to allow the friction pad 162 to follow the patient's vasculature. However, such an elastomeric substrate 184 may not, by itself, provide sufficiently high column strength to prevent or otherwise minimize outward bulging of the tubular pad body 164 in response to movement of the endovascular implant 102 within the inner lumen 122 of the delivery catheter 104 during deployment and / or resheathing of the endovascular implant 102.
[0063] In this case, the adjusting elements 186 preferably have a modulus of elasticity greater than that of the elastomeric substrate 184, thereby increasing the ratio of column strength to radial strength of the tubular pad body 164 (by increasing the numerator (column strength) of the ratio). For example, each of the adjusting elements 186 can be a solid beam constructed from a suitable material, e.g., a metal or metal alloy such as stainless steel, nitinol, cobalt chromium alloy, or a high durometer polymer. In this embodiment, a sufficiently high column strength is provided to the tubular pad body 164 to prevent or otherwise minimize outward bulging of the tubular pad body 164 in response to movement of the endovascular implant 102 within the inner lumen 122 of the delivery catheter 104 during deployment and / or resheathing of the endovascular implant 102, without increasing the radial strength of the tubular pad body 164 to an extent that it cannot frictionally engage the endovascular implant 102, and without increasing the bending stiffness of the tubular pad body 164 to an extent that it cannot easily navigate the patient's vasculature. Preferably, the adjusting elements 186 are not rigidly coupled to one another (i.e., the only material connecting the adjusting elements 186 to one another is the elastomeric substrate 184), allowing the adjusting elements 186 to substantially "float laterally" relative to one another, thereby minimizing any adverse effect on the radial strength and bending stiffness of the tubular pad body 164.
[0064] As another example, the elastomeric substrate 184 can have a relatively high durometer (e.g., a durometer greater than 35D) and thus a relatively high modulus of elasticity (Young's modulus). Materials for such elastomeric substrate 184 include, for example, Pebax®, polyamide, polyurethane, polycarbonate, nylon, etc.
[0065] In this case, such an elastomeric substrate 184 may provide sufficient column strength to prevent or otherwise minimize outward bulging of the tubular pad body 164 in response to movement of the endovascular implant 102 within the inner lumen 122 of the delivery catheter 104 during deployment and / or resheathing of the endovascular implant 102. However, such an elastomeric substrate 184 may not, by itself, provide sufficiently low radial strength (and thus sufficiently high radial expandability / compressibility) to frictionally engage with the endovascular implant 102, or sufficiently low bending stiffness to enable the friction pad 162 to easily navigate the patient's vasculature.
[0066] In this case, it is preferable for the adjusting elements 186 to have a modulus of elasticity (i.e., density) that is less than the modulus of elasticity of the elastomeric substrate 184, thereby increasing the ratio of column strength to radial strength of the tubular pad body 164 (by decreasing the denominator of the ratio (radial strength)). For example, each of the adjusting elements 186 can include gel or air. This provides the tubular pad body 164 with a sufficiently low radial strength to frictionally engage the endovascular implant 102 without reducing the column strength of the tubular pad body 164 to an extent that it cannot prevent or otherwise minimize outward bulging of the tubular pad 164 during deployment and / or resheathing of the endovascular implant 102.
[0067] While particular embodiments of the present invention have been disclosed and described, it should be understood that it is not intended to limit the invention to the preferred embodiments. Moreover, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to cover alternatives, modifications, and equivalents which may be included within the spirit and scope of the present invention as defined by the appended claims.
Claims
1. Intravascular implant delivery system, An intravascular implant having a compression delivery configuration and an expansion deployment configuration, comprising a tubular implant body and a central implant lumen extending axially through the tubular implant body, A delivery catheter having an elongated sheath body and an internal see-through membrane extending axially through the sheath body, wherein the delivery catheter is positioned within the internal see-through membrane when the intravascular implant is in a compressed delivery configuration, An intravascular implant delivery system comprising a pusher member assembly slidably disposed within the internal see-through lumen, wherein the pusher member assembly comprises an elongated pusher member and a friction pad having a radially compressed state and a radially expanded state, wherein when the friction pad is in the radially compressed state, it is disposed within the central implant lumen, and the friction pad comprises a tubular pad body and a central pad lumen extending axially through the tubular pad body, wherein the pusher member is disposed within the central pad lumen, and the tubular pad body comprises an elastomer substrate forming the tubular pad body and at least one adjustment element embedded within the elastomer substrate and extending axially along the elastomer substrate, each of the at least one adjustment element having mechanical properties different from the mechanical properties of the elastomer substrate.
2. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the pusher member assembly and the delivery catheter are movable relative to each other in the axial direction, and the friction pad is configured to frictionally engage with the intravascular implant when the pusher member assembly and the delivery catheter move relative to each other in the axial direction, thereby causing the intravascular implant and the pusher member assembly to move integrally in the axial direction, thereby deploying the intravascular implant from the internal see-through membrane to its expanded deployment configuration.
3. In the intravascular implant delivery system according to claim 2, An intravascular implant delivery system characterized in that the friction pad is configured to frictionally engage with the intravascular implant as the pusher member assembly and the delivery catheter move relative to each other in the axial direction, thereby causing the intravascular implant and the pusher member assembly to move integrally in the axial direction and re-sheathe the intravascular implant, returning it to a compressed delivery configuration within the internal sheath membrane while it is in at least a partially expanded deployment configuration.
4. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the intravascular implant is one of a stent, a stent graft, a flow diverter, a vascular occlusion device, and a vena cava filter.
5. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the pusher member assembly further comprises a proximal bumper and a distal bumper attached to the pusher member, thereby forming an annular space between them, and the friction pad is positioned within this annular space.
6. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the pusher member includes a delivery wire.
7. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the elastomer base material of the friction pad is polyether block amide (PEBA).
8. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that at least one adjustment element increases the ratio of the columnar strength to the radial strength of the tubular pad body.
9. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that each of the at least one adjustment element is elongated.
10. In the intravascular implant delivery system according to claim 9, An intravascular implant delivery system characterized in that each of the at least one elongated adjustment element extends parallel to the longitudinal axis of the tubular pad body.
11. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that each of the at least one adjustment element has an elastic modulus greater than the elastic modulus of the elastomer substrate.
12. In the intravascular implant delivery system according to claim 11, An intravascular implant delivery system characterized in that each of the at least one adjustment element is a solid beam.
13. In the intravascular implant delivery system according to claim 11, An intravascular implant delivery system characterized in that at least one of the adjustment elements increases the columnar strength of the tubular pad body.
14. In the intravascular implant delivery system according to claim 11, An intravascular implant delivery system characterized in that the elastomer substrate has a durometer in the range of 25A to 35D.
15. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that each of the at least one adjustment element has an elastic modulus smaller than the elastic modulus of the elastomer substrate.
16. In the intravascular implant delivery system according to claim 15, An intravascular implant delivery system characterized in that each of the at least one regulatory element is a gel or air.
17. In the intravascular implant delivery system according to claim 15, An intravascular implant delivery system characterized in that at least one adjustment element reduces the radial strength of the tubular pad body.
18. In the intravascular implant delivery system according to claim 15, An intravascular implant delivery system characterized in that the elastomer substrate has a durometer greater than 35D.
19. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the at least one adjustment element includes a plurality of adjustment elements.
20. In the intravascular implant delivery system according to claim 19, An intravascular implant delivery system characterized in that the plurality of adjustment elements are arranged circumferentially within the elastomer substrate.
21. In the intravascular implant delivery system according to claim 1, An intravascular implant delivery system characterized in that the tubular pad body is cylindrical.