WO2009042789A2

WO2009042789A2 - Stent deployment devices and methods

Info

Publication number: WO2009042789A2
Application number: PCT/US2008/077714
Authority: WO
Inventors: Issac J. Zacharias; Maurice Marthaler; Chris L. Staudenmayer; Brian A. Glynn
Original assignee: Trivascular2, Inc.
Priority date: 2007-09-26
Filing date: 2008-09-25
Publication date: 2009-04-02
Also published as: WO2009042789A3; CN101854884A; JP2010540108A; EP2194920A2; BRPI0817566A2

Abstract

A stent system comprising a stent body. At least one barb extends from the stent body and is configured such that a free end thereof is biased to extend radially outward from the stent body. A retaining mechanism is positioned to engage the at least one barb when the stent body is in a compressed state and retain the at least one barb in a tucked position relative to the stent body. A stent, a system for delivering a stent and a method of assembling a stent on a stent delivery shaft. The stent delivery system comprises a delivery shaft and a stent configured to be positioned about the delivery shaft. The stent includes an extension extending circumferentially from a portion of the stent to a free end, thereby defining a shoulder surface. The shoulder surface engages at least a portion of a belt to minimize axial movement of the belt during release of the release wire from engagement with the belt.

Description

STENT DEPLOYMENT DEVICES AND METHODS

Background

Embodiments are directed generally to endoluminal devices, particularly stents and grafts for placement in an area of a body lumen that has been weakened by damage or disease, such as an aneurysm of the abdominal aorta, and more particularly to devices having characteristics that enhance affixation of the devices to the body lumen.

Medical devices for placement in a human or other animal body are well known in the art. One class of medical devices comprises endoluminal devices such as stents, stent-grafts, filters, coils, occlusion baskets, valves, and the like. A stent typically is an elongated device used to support an intraluminal wall. In the case of a stenosis, for example, a stent provides an unobstructed conduit through a body lumen in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside and/or outside thereof. A covered stent is commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), a stent-graft, or endograft. An endograft may be used, for example, to treat a vascular aneurysm by removing or reducing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, an endograft is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called "minimally invasive techniques" in which the endograft, typically restrained in a radially compressed configuration by a sheath, crocheted or knit web, catheter or other means, is delivered by an endograft delivery system or "introducer" to the site where it is required. The introducer may enter the vessel or lumen from an access location outside the body, such as purcutaneously through the patient's skin, or by a "cut down" technique in which the entry vessel or lumen is exposed by minor surgical means. The term "proximal" as used herein refers to portions of the endograft, stent or delivery system relatively closer to the end outside of the body, whereas the term "distal" is used to refer to portions relatively closer to the end inside the body.

After the introducer is advanced into the body lumen to the endograft deployment location, the introducer is manipulated to cause the endograft to be deployed from its constrained configuration, whereupon the stent is expanded to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion typically is effected by spring elasticity, balloon expansion, and/or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration. Among the many applications for endografts is that of deployment in lumen for repair of an aneurysm, such as a thorasic aortic aneurysm (TAA) or an abdominal aortic aneurysm (AAA). An AAA is an area of increased aortic diameter that generally extends from just below the renal arteries to the aortic bifurcation and a TAA most often occurs in the descending thoracic aorta. AAA and TAA generally result from deterioration of the arterial wall, causing a decrease in the structural and elastic properties of the artery. In addition to a loss of elasticity, this deterioration also causes a slow and continuous dilation of the lumen.

The standard surgical repair of AAA or TAA is an extensive and invasive procedure typically requiring a week long hospital stay and an extended recovery period. To avoid the complications of the surgical procedure, practitioners commonly resort to a minimally invasive procedure using an endoluminal endograft to reinforce the weakened vessel wall, as mentioned above. At the site of the aneurysm, the practitioner deploys the endograft, anchoring it above and below the aneurysm to relatively healthy tissue. The anchored endograft diverts blood flow away from the weakened arterial wall, minimizing the exposure of the aneurysm to high pressure.

Intraluminal stents for repairing a damaged or diseased artery or to be used in conjunction with a graft for delivery to an area of a body lumen that has been weakened by disease or damaged, such as an aneurysm of the thorasic or abdominal aorta, are well established in the art of medical science. Intraluminal stents having barbs, hooks, or other affixation means to secure the stents to the wall of the lumen in which they are to be deployed are also well known in the art. While barbed and the like stents are advantageous in anchoring the device, an improved system for retaining and releasing stent barbs is desired.

Summary

In one aspect, the invention provides a stent system comprising a stent body. At least one barb extends from the stent body and is configured such that a free end thereof is biased to extend radially outward from the stent body. A retaining mechanism is positioned to engage the at least one barb when the stent body is in a compressed state and retain the at least one barb in a tucked position relative to the stent body.

In another aspect, the invention provides a stent delivery system comprising a stent body. At least one barb extends from stent body and is configured such that a free end thereof is biased to extend radially outward from the stent body. A support is positioned at least partially within the stent body, said support including a retaining mechanism positioned to engage the at least one barb when the stent body is in a compressed state and retain the at least one barb in a tucked position relative to the stent body.

In another aspect, the invention provides a stent a plurality of struts. A barb extends from at least one of the struts and is configured such that a free end thereof is biased to extend radially outward from the strut. A retaining mechanism is positioned to engage the barb when the stent is in a compressed state and retain the barb in a tucked position relative to the stent, wherein the retaining mechanism comprises a shoulder defined between two portions of at least one strut. In one aspect, the invention provides a stent assembly comprising a stent body. At least one barb extends from the stent body and is configured such that a free end thereof is biased to extend radially outward from the stent body. A belt is releasably positioned about the stent body and aligned with the barb to constrain the barb to a position with the free end proximal to the stent body. In another aspect, the invention provides a method of forming a stent assembly, comprising: forming a stent body having at least one barb with a free end extending radially outward from the stent body; and releasably securing a belt about the stent body in alignment with the barb to constrain the barb to a position with the free end proximate to the stent body.

In one aspect, the present invention may provide a stent comprising a plurality of substantially axially extending struts; and an extension coupled to one of the struts and extending circumferentially therefrom to a free end, thereby defining a shoulder surface at angle approximately 90° or less relative to a longitudinal axis of the stent strut.

In another aspect, the invention may provide a stent delivery system comprising a delivery shaft and a stent configured to be positioned about the delivery shaft. The stent includes an extension extending circumferentially from a portion of the stent to a free end, thereby defining a shoulder surface. A belt has a first portion fixed relative to the delivery shaft and a second portion positioned circumferentially about at least a portion of the stent to retain the stent in an at least partially constrained configuration. A release wire is configured to releasably engage at least a portion of the belt to retain the belt. The shoulder surface engages at least a portion of the belt to minimize axial movement of the belt during release of the release wire from engagement with the belt.

In yet another aspect, the invention may provide a method of assembling a stent on a stent delivery shaft, the method comprising fixing a first portion of a belt relative to the delivery shaft; positioning a stent about a portion of the delivery shaft; positioning a second portion of the belt circumferentially about at least a portion of the stent to retain the stent in a constrained configuration; engaging at least a portion of the belt with a release wire to maintain the belt about the stent; and engaging at least a portion of the belt with an extension extending circumferentially from a portion of the stent and defining a shoulder surface.

Other aspects and advantages of embodiments of the present invention will be apparent from the detailed description of the invention provided hereinafter.

Brief Description of the Drawings

Fig. 1 is an isometric view of a bushing retainer mechanism in accordance with a first embodiment of the present invention. Fig. 2 is a flat pattern of a stent incorporating the bushing retainer mechanism of Fig. 1.

Fig. 3 is an isometric view of a bushing retainer mechanism that is an alternative embodiment of the present invention. Fig. 4 is an isometric view of a bushing retainer mechanism that is another alternative embodiment of the present invention.

Fig. 5 is a top plan view of a stent delivery system incorporating the bushing retainer mechanism of Fig. 3.

Fig. 6 is an expanded view of one of the bushing retainer mechanisms of Fig. 5.

Fig. 7 is a front plan view of a portion of a stent incorporating an alternative retainer mechanism in accordance with the invention.

Fig. 8 is a rear plan view of a portion of a stent incorporating an alternative retainer mechanism in accordance with the invention. Fig. 9 shows a flat pattern of a portion of the stent of Fig. 7.

Fig. 10 is a cross-sectional view along the line 10-10 in Fig. 9. Fig. 1 1 is a cross-sectional view along the line 1 1 -1 1 in Fig. 9.

Fig. 12 is a side elevation of a compressed stent with belted barbs in accordance with a first embodiment of the present invention. Fig. 13 is a side elevation of the compressed stent of Fig. 12 with the barbs released.

Fig. 14 shows a flat pattern of the stent of Fig. 12 illustrating the grinding pattern of the grooves.

Fig. 15 is a side elevation of a compressed stent with belted barbs in accordance with an alternative embodiment of the present invention.

Fig. 16 is a side elevation of the compressed stent of Fig. 15 with the barbs released.

Fig. 17 shows a flat pattern of the stent of Fig. 15 illustrating the grinding pattern of the grooves. Fig. 18 is a cross-sectional view of a grinding rod of a first method for grinding the stent of Fig. 15.

Fig. 19 is a cross-sectional view similar to Fig. 18 and illustrating a stent positioned on the grinding rod for grinding. Fig. 20 is an isometric view of an alternative grinding rod and associated collar.

Fig. 21 is a cross-sectional view of the grinding rod of Fig. 20.

Fig. 22 is an end elevation view of the collar of Fig. 20.

Fig. 23 is a cross-sectional view along the line 23-23 in Fig. 22. Fig. 24 is a side elevation of a compressed stent with belted barbs in accordance with another alternative embodiment of the present invention.

Fig. 25 is a side elevation of the compressed stent of Fig. 24 with the barbs released.

Fig. 26 shows a flat pattern of the stent of Fig. 24 illustrating the grinding pattern of the grooves.

Fig. 27 shows a flat pattern of another alternative stent illustrating the grinding pattern of the grooves.

Fig. 28 is a cross-sectional view of a grinding rod of a method for grinding the stent of Fig. 27. Fig. 29 is a cross-sectional view similar to Fig. 28 and illustrating a stent positioned on the grinding rod for grinding.

Fig. 30 is a side elevation view in partial section of a prior art endovascular stent graft delivery system.

Fig. 31 shows a flat pattern of an embodiment of a stent in accordance with one or more aspects of the invention.

Fig. 32 is a side elevation view illustrating the stent of Fig. 31 positioned about an embodiment of a delivery system in accordance with one or more aspects of the invention. Fig. 33 is a side elevation view illustrating an embodiment of a delivery shaft with a belt positioned thereabout.

Fig. 34 shows a flat pattern of an alternative embodiment of a stent in accordance with one or more aspects of the invention. Fig. 35 is a side elevation view illustrating the stent of Fig. 34 positioned about an embodiment of a delivery system in accordance with one or more aspects of the invention.

Fig. 36 shows a flat pattern of another alternative embodiment of a stent in accordance with one or more aspects of the invention.

Detailed Description

Referring to Figs. 1-2, a retainer mechanism 40 that is a first embodiment of the present invention is illustrated. The retainer mechanism 40 includes a generally cylindrical bushing body 42. While the bushing body 42 is illustrated as cylindrical, it is not limited to such and may have other configurations. The bushing body 42 includes a through bore 44 configured to receive a delivery catheter or guidewire chassis (not shown) of a stent-graft delivery system. The outer surface of the bushing body 42 includes pairs of radially extending pins 46. Each pair of pins 46 defines a barb receiving space 48 therebetween. The bushing body 42 and the pins 46 may be manufactured from a hard material, for example, polyimide, PEEK or polyurethane, or a softer material, for example, urethanes or silicone, such that the barbs 14 can be compressed within the receiving space 48 and into the surface of the bushing body 42 for increased stability. Fig. 2 illustrates an illustrative stent 10' positioned relative to the retainer mechanism 40. The bushing body 42 is axially positioned along the delivery system such that the barbs 14 align with and are received in the receiving space 48 between a respective pair of pins 46. The pins 46 are circumferentially aligned with a respective tuck pad 16 or strut 12 such that the barb 14 received in a receiving space 48 is maintained under the tuck pad 16 or strut 12. Since a pin 46 is provided on each lateral side of the barb 14, the pins 46 will maintain the barb 14 in proper lateral alignment even if the barb lateral angle α is not maintained to the highest tolerances.

The pins 46 have a radial height that is approximately one half of the thickness of the struts 12. As such, the pins 46 do not interfere with the compression of the stent. If the retaining mechanism is manufactured from a softer materials, the bushing body 42 can compress and relieve some of the added thickness of the tucked barb 14.

While an embodiment of a retaining mechanism 40 has the pins 46 in pairs, such is not required and the pins 46 can be grouped individually or in groups of more than two. As illustrated in Fig. 2, a retaining mechanism 40' with a single pin 46 is provided adjacent an end of the stent 10' to provide a crown 13 locating feature. Additionally, while the bushing body 42 is illustrated as extending a short axial distance adjacent the barb 14, the body 42 may have a longer axial length. For example, the bushing body 42 may be sufficiently long to extend under one or both belt axial positions such that the belts can be attached to the retaining member 40. Other shapes and configurations of the bushing body 42 and the pins 46 are within the scope of the present invention.

Referring to Figs. 3 and 5-6, a retaining mechanism 50 that is an alternative embodiment of the present invention will be described. The retaining mechanism 50 is similar to the previous embodiment and includes a bushing body 52 with a through bore 54 configured to receive a guidewire chassis 22 of a delivery system as illustrated in Figs. 5 and 6. While the retaining mechanism 50 may be secured to the guidewire chassis 22, such is not required and freedom of the retaining mechanism 50 may allow for greater flexibility and alignment. The retaining mechanism 50' illustrated in Fig. 4 is substantially the same as in the present embodiment but includes a secondary through passage 58. The secondary through passage 58 facilitates passage of additional delivery system items, for example, such as when the retaining mechanism 50' is used with a distal stent.

Both of the retaining mechanisms 50, 50' include a plurality of helical slots 56 formed about the outer surface of the bushing body 52. Each slot is configured to receive a barb 14 when the stent 10 is compressed via the belts 26. The helical nature of the slots 56 corresponds with the laying direction of the tucked barbs 14. The slots 56 may have other configurations to accommodate barbs 14 having different configurations. The slots 56 receive the tucked barbs 14 and retain them in the tucked position, aligned with a corresponding strut or tuck pad. Additionally, since the slots 56 are recessed into the bushing body 52, the tucked barbs 14 do not add to the radial size of the compressed stent. As seen in Fig. 5, multiple retaining mechanisms 50 may be utilized with a delivery system. The direction of the slots 56 for the two retaining mechanisms 50 is opposite such that they accommodate barbs 14 extending in opposite directions.

Referring to Figs. 7-1 1 , a retaining mechanism 71 that is another alternative embodiment of the present invention is shown. The retaining mechanism 71 is formed integrally with the stent 70, as opposed to being accommodated on the delivery system as in the previous embodiments. The retaining mechanism 71 is defined by the stent struts 72 and the associated reduced thickness tuck pads 76.

Referring to Figs. 10 and 1 1 , each tuck pad 76 has a radial height h that is approximately one-half or less the radial height of the corresponding strut 72. As such, the retaining mechanism 71 is defined by the shoulder 75 defined between the strut 72 and tuck pad 76. Referring to Figs. 8 and 9, in the compressed state, the barbs 74 are forced against the shoulder 75 of the retaining mechanism 71. The risk of the barb 74 overextending past the tuck pad or strut is reduced since the shoulder 75 of the retaining mechanism 71 prevents such. As such, the barb lateral angle α can be increased to ensure that the barbs 74 will not back out while not having to worry about overextension. Additionally, since the tuck pads 76 are approximately one-half or less the height of typical tuck pads, they will have a reduced effect on the radial thickness of the compressed stent 70. Referring to Figs. 12-14, a stent 1 10 that is a first embodiment of the present invention is illustrated, with Figs. 12 and 13 illustrating the stent 1 10 schematically and Fig. 14 illustrating a flat pattern of the stent 1 10. Stent 1 10 includes a plurality of struts 1 12 extending axially between the opposed ends 1 1 1 , 1 13 thereof. The stent 1 10 can be oriented in either direction, that is, the end 1 13 may represent the proximal end or the distal end of the stent 1 10, depending on the application. Both ends 1 1 1 , 1 13 have a plurality of crowns adjoining adjacent struts 1 12. The end 1 13 of stent 1 10 has a plurality of connecting members 1 16 configured to connect the stent 1 10 to a graft or other structure. The illustrated stent 1 10 structure is merely a representative example, and the invention is not intended to be limited to such. The stent 1 10 of the present invention can have various structures and is not limited to the strut structure illustrated herein. For example, the stent may have a body defined by a lattice structure or a helical structure. Along one or more of the struts 1 12, a barb 120 is provided. Referring to

Fig. 14, the barbs 120 are preferably formed integrally with the struts 1 12, but may otherwise be manufactured, for example, as a separate component attached to the struts 1 12. Each of the barbs 120 has a pointed tip 121 configured to engage the intended lumen wall. In the present embodiment, each tip 121 slopes outwardly along its outward radial extent. The stent struts 1 12 and the barbs 120 are preferably self expanding, that is, upon release of a constraining force, the struts 1 12 will move radially apart and the barbs 120 will extend radially outward. Other configurations, for example, balloon expansion, are also contemplated within the present invention. Referring to Fig. 12, a belt 124 is compressed about the stent 1 10 and contacts approximately the tips 121 of the barbs 120 to constrain the barbs 120. A release wire 125 or the like preferably extends through the ends of the belt 124 to retain the belt 124 in the constraining condition. The release wire 125 may extend through the barb belt 124 alone with a separate wire 1 17 extending through the main belts 1 19 retaining the stent 1 10, as illustrated. Alternatively, a single wire may pass through all of the belts 1 19 and 124 and control deployment of the stent 1 10 and the barbs 120. The belts 1 19 and 124 and release wires 1 17 and 125 can be selected to provide various deployment sequences. For example, the barbs 120 may be deployed first, as illustrated in Fig. 13, and thereafter the stent 1 10 deployed such that the barbs 120 are positioned for engagement as soon as the stent is released. As another example, all of the belts 1 19 and 124 may be release substantially simultaneously such that the stent 1 10 opens in a uniform manner. Alternatively, a single belt may be utilized for both maintaining the stent 1 10 in the compressed configuration and retaining the barbs 120 in the constrained condition. Various belt and release wire configurations and sequences are described in U.S. Patent Application Publication No. US 2004/0138734, which is incorporated herein in its entirety by reference. To minimize axial movement of the belt 124, a circumferential groove 122 is preferably ground, etched (e.g. laser or chemical) or otherwise formed about the stent 1 10 axially aligned with the barbs 120. The groove is similar to the circumferential grooves 1 18 provided for the main belts 1 19. In the present embodiment, the groove 122 is substantially aligned with the barb tips 121 , such that the barb tips 121 have a minimal groove 123 therein. The barbs 120 continue to present a sharpened tip and the groove 123 generally does not affect the barb 120 effectiveness. The groove 122 extending across each of the struts 1 12 and the barb tips 121 can be seen in the schematic drawing in Fig. 14. As illustrated in Fig. 12, the belt 124 retains each of the barbs 120 in a constrained position with the sharpest portion of the tip positioned radially inward from the surface of the stent 1 10, thereby providing effective barb 120 constraint. Additionally, since the barbs 120 are not tucked under the struts 1 12 or tucking pads (which may be used in prior art devices, but not required with the present device), the barbs 120 are free to reliably expand as soon as the belt 124 is removed. As an additional advantage, since the barbs 120 are not tucked under the struts 1 12, the stent 1 10 maintains a slim and more uniform radial profile in the compressed state. In contrast, stents with tucked barbs often have an expanded mid-section, similar to a football shape, due to the double material thickness of the strut and barb tucked underneath.

Referring to Figs. 15-17, a stent 1 10' that is an alternative embodiment of the present invention is shown. The stent 1 10' is similar to that of the previous embodiment, except that a groove 123 is not present on the barb tips 121 '. This is illustrated more clearly in Fig. 17. Referring to Fig. 16, the barb 120 includes a full outwardly directed tip 121 '. In addition to providing more material (since there is no groove 123), the belt 124 has the higher radially outward surface of the barb 120 to contact. As such, the belt 124 more effectively depresses the barbs 120 below the outer radial surface of the compressed stent 1 10'.

Referring to Figs. 18 and 19, a first method of manufacturing the stent 1 10' of Figs. 15-17 will be described. A grinding rod 150 has a generally cylindrical body 152 with a circumferential recess 154 formed adjacent one end of the rod 150. The circumferential recess 154 is configured to receive the barbs 120 in an inwardly deflected position such that the barb outer surfaces are below the plane of the grinding wheel (not shown). As shown in Fig. 19, the stent 1 10' is positioned on the grinding rod 150 with the barbs 120 axially aligned with the circumferential recess 154. A deflecting block 160 or the like is attached to the outer surface of each barb 120. A wire 162 or the like is then tightened about the deflecting blocks 160 such that the blocks 160, and thereby the barbs 120, are deflected inward. With the barbs 120 deflected into the circumferential groove 154, the grinding wheel can be utilized to grind the barb belt groove 122'. Upon removal of the stent 1 10' from the grinding rod 150, the stent struts 1 12 include the groove 122', but the barbs 120 do not have the groove 122', as illustrated schematically in Fig. 17. The main belt grooves 1 18 may also be ground prior to removal of the stent 10' from the grinding rod 150.

Referring to Figs. 20-23, an alternative method of manufacturing the stent 1 10' of Figs. 15-17 will be described. The method again utilizes a grinding rod 150' having a cylindrical body 152'. Instead of providing a full circumferential groove, individual barb slots 154' are provided in the grinding rod 150'. As such, the barbs 120 can be deflected into the slots 154' while the struts 1 12 remain supported along the rod body 152' during grinding of the groove 122'. To deflect the barbs 120 into the slots 154', a collar 170 is utilized. The collar 170 includes a cylindrical body 172 with an axial through bore 173 larger than the outer diameter of the stent 1 10' when it is positioned on the rod 150'. The collar 170 includes a plurality of inwardly extending ribs 174 corresponding to the number of barbs 120 and slots 154'. The ribs 174 define an inner diameter therebetween which is only slightly larger than the outer diameter of the grinding rod 150'. As such, as the collar 170 is moved onto the grinding rod 150', the stent struts 1 12 fit between the collar body 172 and the grinding rod 150', however, the clearance at the ribs 174 is not sufficient, and the ribs 174 contact the corresponding barbs 120 and deflect the barbs 120 into the corresponding slots 154'. Each of the ribs 174 preferably has a tapered forward end 176 to further facilitate passage of the rib 174 onto the respective barb 120. Referring to Figs. 24-26, a stent 1 10" that is an alternative embodiment of the present invention is shown. The stent 1 10" is similar to that of the stent 1 10' of Figs. 15-17 and again does not include a groove 122" extending across the barb tips 121 ", as seen in Fig. 26. Referring to Fig. 25, the stent 1 10" differs from the stent 1 10' in that the barb 120 converges inward to a radially inward tip 121 ". As such, the barb 121 " is yet further recessed from the stent outer surface, as illustrate in Fig. 24. In some applications, the inward tip 21 " may also prove more effective since the tip 121 " will effectively lock against radially inward disengagement once it engages the lumen wall.

Referring to Fig. 27, a flat schematic pattern of another alternative stent 1 10"' is shown. The current stent 1 10"' is in opposite to the stent 1 10' of Figs. 15- 17 in that the stent 1 10"' includes a belt groove 122"' extending across the barbs 120, but no associated belt groove extending across the stent struts 1 12. Such a configuration has been found in some applications to provide a better combination of barb recessing and barb constraining effectiveness.

Referring to Figs. 28 and 29, a method of manufacturing the stent 1 10"' of Fig. 27 will be described. A grinding rod 150"' has a generally cylindrical body 152"' with a circumferential recess 154"' formed at the complete end of the rod 150"'. The circumferential recess 154"' is configured to receive the struts 1 12 and the end 1 13 of the stent 1 10"' below the surface of the barbs 120. To ensure the barbs 120 do not deflect inward, a support wire 164 is positioned between the barbs 120 and the struts 1 12. The support wire 164 maintains the barbs 120 in the grinding plane such that belt grooves 122"' may be formed therein. A retaining wire 166 may be provided about the end 1 13 of the stent 1 10"' to ensure it is maintained away from the grinding plane.

Medical devices for placement in a human or other animal body are well known in the art. One class of medical devices comprises endoluminal devices such as stents, stent-grafts, filters, coils, occlusion baskets, valves, and the like. A stent typically is an elongated device used to support an intraluminal wall. In the case of a stenosis, for example, a stent provides an unobstructed conduit through a body lumen in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside and/or outside thereof. A covered stent is commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), a stent-graft, or endograft.

An endograft may be used, for example, to treat a vascular aneurysm by removing or reducing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, an endograft is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called "minimally invasive techniques" in which the endograft, typically restrained in a radially compressed configuration by a sheath, crocheted or knit web, catheter or other means, is delivered by an endograft delivery system or "introducer" to the site where it is required. The introducer may enter the vessel or lumen from an access location outside the body, such as purcutaneously through the patient's skin, or by a "cut down" technique in which the entry vessel or lumen is exposed by minor surgical means. U.S. Patent Application Publication No. US 2004/0138734, which is incorporated herein in its entirety by reference, describes systems and methods for the delivery of stents, endovascular grafts, and the like. Fig. 30 herein illustrates a delivery system 210 of such publication for delivering a variety of expandable intracorporeal devices; for example, an expandable endovascular graft 21 1 . One such expandable endovascular graft 21 1 useful for delivery and deployment at a desired site within a patient is disclosed in U.S. Patent No. 6,395,019, which is hereby incorporated by reference in its entirety.

Delivery system 210 in Fig. 30 has an elongate shaft 212 with a proximal section 213, a distal section 214, a proximal end 215 and a distal end 216. The distal section 214 has an elongate belt support member in the form of a guidewire tube 217 disposed adjacent a portion of the expandable endovascular graft 21 1. A guidewire 218 is disposed within guidewire tube 217. A plurality of belts 221 , 222, and 223 are secured to the guidewire tube 217 and are circumferentially disposed about portions of the endovascular graft 21 1. Fig. 30 shows the belts in a configuration that constrains the endovascular graft 21 1. First and second release members 224 and 225 releasably secure belts 221 , 222, and 223 in a constraining configuration as shown.

As defined herein, the proximal end of the elongate shaft is the end 215 proximal to an operator of the delivery system 210 during use. The distal end of the elongate shaft is the end 216 that enters and extends into the patient's body. The proximal and distal directions for the delivery system 210 and endovascular graft 21 1 loaded within the delivery system 210 as used herein are the same. This convention is used throughout the specification for the purposes of clarity, although other conventions are commonly used.

Belts 221-223 extend circumferentially about the respective portions of the expandable intracorporeal device 21 1 and are releasably locked together by one or more release members 224 and 225. U.S. Patent Application Publication No. US 2004/0138734 discloses various belt and release wire configurations that may be utilized to secure stents and the like.

To deploy the graft 21 1 , the release wires 224 and 225 are pulled proximally, in a desired sequence, such that the release wires 224 and 225 disengage from the end loops of the belts 221 , 222 and 223. It is desired to provide a system and method to minimize the axial force required on the release wires 224 and 225 to release the belts 221 , 222 and 223.

Referring to Fig. 31 , a stent 230 that is a first embodiment of the present invention is illustrated. Stent 230 includes a plurality of struts 232 extending axially between the opposed ends 231 , 233 thereof. The stent 230 can be oriented in either direction, that is, the end 233 may represent the proximal end or the distal end of the stent 230, depending on the application. Both ends 231 , 233 have a plurality of crowns adjoining adjacent struts 232. The end 233 of stent 230 has a plurality of connecting members 236 configured to connect the stent 230 to a graft or other structure. The illustrated stent 230 structure is merely a representative example, and the invention is not intended to be limited to such. The stent 230 of the present invention can have various structures and is not limited to the strut structure illustrated herein. For example, the stent 230 may have a body defined by a lattice structure or a helical structure. Along one or more of the struts 232, a barb 240 may be provided. The barbs 240 are preferably formed integrally with the struts 232, but may otherwise be manufactured, for example, as a separate component attached to the struts 232. The stent struts 232 and the barbs 240 are preferably self expanding, that is, upon release of a constraining force, the struts 232 will move radially apart and the barbs 240 will extend radially outward. Other configurations, for example, balloon expansion, are also contemplated within the present invention. Referring to Figs. 32 and 33, a belt 244 is positioned about the stent 230 and secured to maintain the stent 230 in at least a partially constrained configuration. In the present embodiment, opposite ends 243 and 245 of the belt 244 are separately wrapped about the delivery shaft 260. Both ends 243 and 245 are secured to the delivery shaft 260, for example, via adhesive, welding, bonding or any other suitable means. Two intermediate belt portions 247 and 249 extend from the bonded portions and are intertwined to define an eye loop 250 at a free portion of the belt 244 configured to receive a release wire 270 to maintain the stent 230 in the at least a partially constrained configuration. As illustrated in Figs. 32 and 33, in the present embodiment, intermediate belt portion 247 is returned upon itself to form a partial loop portion 251 through which the release wire 270 extends. Intermediate belt portion 249 extends tangentially from the delivery shaft 260 and extends over the release wire 270.

While the release wire 270 is illustrated as engaging only one belt, the release wire 270 may extend through multiple stent belts 244 or a single stent belt 244. Various belt and release wire configurations and sequences are described in U.S. Patent Application Publication No. US 2004/0138734, which is incorporated herein in its entirety by reference.

To provide general axial containment of the belt 244, a circumferential groove 242 is preferably ground about the stent 230. While the groove 242 provides general axial containment, belts of prior art systems have been found to move in conjunction with the release wire due to the friction force created between the belt and the release wire. The friction force may provide undesired resistance to removal of the release wire. Such undesired resistance to removal of the release wire may be further enhanced if a portion of the belt moves axially, thereby creating a pivot motion which may pinch or otherwise trap the release wire.

Referring to Figs. 31 and 32, the stent 230 of the present embodiment of the invention includes an extension 280 extending circumferentially from one of the struts 232 to define a shoulder surface 282. In the present embodiment, the extension 280 is formed integrally with the strut 232 during stamping of the stent 230. Provision of the extension 280 on the stent 230 allows the extension 280 to be accurately positioned relative to the intended position of the belt 244. In the present embodiment, the shoulder surface 282 is positioned slightly proximal of the groove 242. The shoulder surface 282 preferably extends at an angle 0 relative to the longitudinal axis of the strut. With such an arrangement, the shoulder surface 282 guides the belt 244 toward the junction 284 between the shoulder surface 282 and the strut 232 and reduces the changes the belt 244 will slip past the extension 280 in the proximal direction.

Referring to Fig. 32, it is preferable that the extension 280 is provided on the strut 232 which is the last strut 232 that the free portion of the belt 244 passes over. As such, the eye loop 250 positioned about the release wire 270 biases the release wire 270 toward the extension 280, thereby moving the intermediate portion 249 toward the shoulder surface 282. However, the extension 280 may be provided on any of the other struts 232 if such will be aligned adjacent the release wire 270.

As further illustrated in Fig. 32, it is also preferable that the extension 280 be axially positioned such that it is proximally adjacent the intermediate belt portion 249 which extends tangentially from the delivery shaft 260 as opposed to the intermediate belt portion 247 that is returned upon itself. With such an arrangement, the intermediate belt portion 249 extends from under the strut 232 over the release wire such that it crosses the shoulder surface 282. However, the extension 280 may be otherwise axially positioned. For example, in the embodiment illustrated in Fig. 35, the extension 280' is positioned axially adjacent the returned intermediate belt portion 247, however, the extension 280' still contacts the eye loop 250 and maintains the axial position of the belt 244.

The belt 244 can be made from any high strength, resilient material that can accommodate the tensile requirements of the belt members and remain flexible after being set in a constraining configuration. Typically, belt 244 is made from solid ribbon or wire of a shape memory alloy such as nickel titanium or the like, although other metallic or polymeric materials are possible. Belt 244 may also be made of braided metal filaments or braided or solid filaments of high strength synthetic fibers such as Dacron^®, Spectra or the like. The release wire 270 is generally made from a biocompatible high strength alloy such as stainless steel, but can also be made from any other suitable materials. Examples include other metallic alloys such as nickel titanium, non-metallic fibers such as carbon, polymeric materials, composites thereof, and the like. The diameter and stiffness of the release wire 270 can be selected in accordance with the diameter and stiffness of the belt 244. The configuration of the belt 244 may vary to suit the particular embodiment of the delivery system. As set forth above, various belt and release wire configurations and sequences are described in U.S. Patent Application Publication No. US 2004/0138734, which is incorporated herein in its entirety by reference.

The delivery shaft 260 illustrated herein may have various configurations. For example, the delivery shaft 260 may be a catheter, a guide wire lumen, a solid shaft or any other suitable structure. Similarly, while the belts 244 are illustrated as directly connected to the delivery shaft 260 without any additional support, belt bushings, standoff tubes and the like may be provided to secure, support and direct the belt 244.

Referring to Figs. 34 and 35, a stent 230' that is an alternative embodiment of the present invention is shown. The stent 230' is similar to the previous embodiment and like elements are numbered alike. Stent 230' includes a extension 280' that is formed integrally formed with the strut 232 axially aligned with the groove 242 such that the shoulder surface 282' is within the axial confines of the groove 242. Additionally, the shoulder surface 282' is at angle 0 which is substantially perpendicular to the strut 232. The junction 284' is still configured to receive a portion of the belt 244. As explained above with respect to Fig. 35, the extension 280' is positioned axially adjacent the returned intermediate belt portion 247, however, the extension 280' still contacts the eye loop 250 and maintains the axial position of the belt 244. The extension 280' has a circumferential length such that the extension 280' does not pass under the release wire 270, but instead terminates prior to reaching the release wire 270. Referring to Fig. 36, a stent 230" that is an another alternative embodiment of the present invention is shown. The stent 230" is similar to the previous embodiments and like elements are numbered alike. Stent 230" includes a extension 280". The extension 280" is formed as part of a separate shoulder member 300 that is interconnected with the strut 232. The shoulder member 300 may be crimped, adhered, welded, bonded or otherwise fixed relative to the strut 232. The shoulder member 300 is axially aligned such that the shoulder surface 282" is axially aligned in a desired relationship with respect to the groove 242. In the illustrated embodiment, the contact face 282" is aligned directly with an axial edge of the groove 242 and the shoulder surface 282" is at angle 0 which is substantially perpendicular to a longitudinal axis of the strut 232. The position of the extension 280" relative to the intermediate belt portions 247 and 249 can be controlled by positioning the shoulder member 300 prior to interconnection and/or by controlling the direction of winding of the belt 244 with respect to the delivery shaft 260.

While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention.

Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.

Claims

What is claimed is:

1. A stent system comprising: a stent body; at least one barb extending from the stent body and configured such that a free end thereof is biased to extend radially outward from the stent body; and a retaining mechanism positioned to engage the at least one barb when the stent body is in a compressed state and retain the at least one barb in a tucked position relative to the stent body.

2. The stent system according to claim 1 wherein the retaining mechanism includes a bushing body configured to be supported on a stent delivery system.

3. The stent system according to claim 2 wherein the bushing body includes a radial surface with one or more radial outwardly extending pins.

4. The stent system according to claim 3 wherein the pins are arranged in pairs and define a barb receiving space in between each pair of pins.

5. The stent system according to claim 4 wherein the pins are manufactured from a compressible material such that the barb is compressed within the respective barb receiving space.

6. The stent system according to claim 4 wherein each barb receiving space is circumferentially aligned with a strut or tuck pad of the stent body.

7. The stent system according to claim 3 wherein the at least one barb has a thickness and each pin has a radial thickness approximately one-half the barb thickness.

8. The stent system according to claim 2 wherein a stent restraining belt is supported by the bushing body.

9. The stent system according to claim 2 wherein the bushing body includes a secondary through passage.

10. The stent system according to claim 2 wherein the bushing body includes a plurality of surface slots configured to receive a corresponding barb.

1 1. The stent system according to claim 10 wherein each of the slots extends helically.

12. The stent system according to claim 1 1 wherein the delivery system supports a secondary retaining mechanism including a plurality of surface slots, and wherein the surface slots of the secondary retaining mechanism extend helically in a direction opposite to the slots of the other retaining mechanism.

13. The stent system according to claim 10 wherein each of the slots is configured to circumferentially align with a strut or tuck pad of the stent body.

14. The stent system according to claim 2 wherein the bushing body is free to rotate relative to the stent delivery system.

15. The stent system according to claim 1 wherein the retaining mechanism is formed integrally with the stent body.

16. The stent system according to claim 15 wherein the retaining mechanism includes a shoulder defined between one of the struts and an associated tuck pad.

17. The stent system according to claim 16 wherein the tuck pad has a radial thickness that is approximately one-half or less of a radial thickness of the associated strut.

18. A stent delivery system comprising: a stent body; at least one barb extending from stent body and configured such that a free end thereof is biased to extend radially outward from the stent body; and a support positioned at least partially within the stent body, said support including a retaining mechanism positioned to engage the at least one barb when the stent body is in a compressed state and retain the at least one barb in a tucked position relative to the stent body.

19. A stent comprising: a plurality of struts; a barb extending from at least one of said struts and configured such that a free end thereof is biased to extend radially outward from the strut; and a retaining mechanism positioned to engage the barb when the stent is in a compressed state and retain the barb in a tucked position relative to the stent, wherein the retaining mechanism comprises a shoulder defined between two portions of at least one said strut.

20. A stent assembly comprising: a stent body; at least one barb extending from the stent body and configured such that a free end thereof is biased to extend radially outward from the stent body; and a belt releasably positioned about the stent body and aligned with the barb to constrain the barb to a position with the free end proximate to the stent body.

21. The stent according to claim 20 wherein the stent body comprises a plurality of axially extending struts.

22. The stent according to claim 20 wherein the stent body comprises a lattice structure.

23. The stent according to claim 20 wherein the stent body comprises a helical structure.

24. The stent according to claim 20 wherein the at least one barb is formed integrally with the stent body.

25. The stent according to claim 20 wherein the barb free end has a pointed tip.

26. The stent according to claim 25 wherein the pointed tip converges radially outward.

27. The stent according to claim 25 wherein the pointed tip converges radially inward.

28. The stent according to claim 25 wherein a circumferential groove configured to receive the belt extends across the pointed tip.

29. The stent according to claim 28 wherein the circumferential groove does not extend across the stent body.

30. The stent according to claim 20 wherein a circumferential groove extends about the stent body and is configured to receive the belt.

31. The stent according to claim 30 wherein the circumferential groove extends across a portion of the at least one barb.

32. The stent according to claim 20 wherein a release wire releasably secures the belt.

33. The stent according to claim 20 wherein at least one secondary belt radially constrains the stent body.

34. The stent according to claim 33 wherein a single release wire releasably secures the belt and the at least one secondary belt.

35. The stent according to claim 33 wherein a first release wire releasably secures the belt and a second release wire releasably secures the at least one secondary belt.

36. A method of forming a stent assembly, comprising: forming a stent body having at least one barb with a free end extending radially outward from the stent body; and releasably securing a belt about the stent body in alignment with the barb to constrain the barb to a position with the free end proximate to the stent body.

37. The method according to claim 36 further comprising: defining a circumferential groove about the stent body configured to receive the belt.

38. The method according to claim 37 wherein the step of defining the circumferential groove includes deflecting the at least one barb radially inward such that the at least one barb does not include the circumferential groove.

39. The method according to claim 36 further comprising: defining a circumferential groove across the at least one barb configured to receive the belt.

40. The method according to claim 39 wherein the step of defining the circumferential groove includes deflecting the stent body radially inward such that the stent does not include the circumferential groove.

41. A stent comprising: a plurality of substantially axially extending struts; and an extension coupled to one of the struts and extending circumferentially therefrom to a free end, thereby defining a shoulder surface at angle approximately 90° or less relative to a longitudinal axis of the stent strut.

42. The stent of claim 41 wherein the extension is formed integrally with the strut.

43. The stent of claim 41 wherein the extension is formed as part of a separate shoulder member that is interconnected with the strut.

44. The stent of claim 43 wherein the shoulder member is interconnected with the strut via crimping, adhesion, welding or bonding.

45. The stent of claim 41 wherein a belt groove extends circumferentially about the plurality of struts, the belt groove defining a distal edge and a proximal edge.

46. The stent of claim 45 wherein the shoulder surface is axially adjacent to the belt groove proximal edge.

47. The stent of claim 45 wherein the shoulder surface is proximal relative to the belt groove proximal edge.

48. The stent of claim 45 wherein the shoulder surface is axially aligned between the belt groove distal and proximal edges.

49. The stent of claim 41 wherein the shoulder surface is at an angle of approximately 90° relative to the longitudinal axis of the stent strut.

50. The stent of claim 41 wherein the shoulder surface is at an angle of less than 90° relative to the longitudinal axis of the stent strut.

51. A stent delivery system comprising: a delivery shaft; a stent configured to be positioned about the delivery shaft, the stent including an extension extending circumferentially from a portion of the stent to a free end, thereby defining a shoulder surface; a belt having a first portion fixed relative to the delivery shaft and a second portion positioned circumferentially about at least a portion of the stent to retain the stent in an at least partially constrained configuration; and a release wire configured to releasably engage at least a portion of the belt to retain the belt; wherein the shoulder surface engages at least a portion of the belt to minimize axial movement of the belt during release of the release wire from engagement with the belt.

52. The delivery system of claim 51 wherein the belt second portion is defined by first and second belt intermediate portions which are intertwined to define an eye loop.

53. The delivery system of claim 52 wherein the first belt intermediate portion extends tangentially relative to the delivery shaft and the second belt intermediate portion reverses upon itself to define a partial loop portion.

54. The delivery system of claim 53 wherein the shoulder surface is axially adjacent to the first belt intermediate portion.

55. The delivery system of claim 54 wherein the first intermediate portion extends from under the stent to over the release wire such that the first intermediate portion crosses the shoulder surface.

56. The delivery system of claim 52 wherein the shoulder surface is axially adjacent to the eye loop.

57. The delivery system of claim 51 wherein the stent includes a plurality struts and the shoulder extends from the strut which is the last strut which the belt second portion passes over.

58. The delivery system of claim 57 wherein the belt second portion biases the release wire toward the shoulder surface.

59. The delivery system of claim 58 wherein the release wire biases an intermediate portion of the belt toward the shoulder surface.

60. A method of assembling a stent on a stent delivery shaft, the method comprising: fixing a first portion of a belt relative to the delivery shaft; positioning a stent about a portion of the delivery shaft; positioning a second portion of the belt circumferentially about at least a portion of the stent to retain the stent in a constrained configuration; engaging at least a portion of the belt with a release wire to maintain the belt about the stent; and engaging at least a portion of the belt with an extension extending circumferentially from a portion of the stent and defining a shoulder surface.

61. The method of claim 60 further comprising defining a groove about a circumference of the stent.

62. The method of claim 61 wherein the shoulder surface is positioned adjacent to or within the groove.