MEDICAL DEVICE SYSTEM

A medical device system includes a tubular medical device and a diameter reducing arrangement. The tubular medical device comprises a tubular graft body having a proximal end and a distal end. The diameter reducing arrangement is configured for constricting the medical device, and includes a strand section having first and second ends and being immovably secured to the medical device at the first end and at the second end. The second end is a first circumferential distance from the first end by way of a path along the strand section In a constricted configuration of the medical device a first portion of the strand section extends back on itself to form a first double-stranded tail leading to a first loop, the first tail extending circumferentially against the graft body, constricting the medical device by the strand section restricting the first circumferential distance between the first and second ends of the strand section.

RELATED APPLICATIONS

This application priority to UK Application Serial No. 2310335.1 filed on Jul. 5, 2023, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND

1. Technical Field Text

The present invention relates to a system for reducing the diameter of a medical device, including a tubular graft body, optionally a stent, and a diameter reducing arrangement.

2. Background Information

Aneurysms or ulcers of the thoracic aorta or aortic arch can be treated by insertion of a prosthesis, such as a stent graft, into an appropriate position. Owing to the curvature of the aorta, it is desirable to conform the stent graft, in particular the proximal end of the stent graft, with the curve of the aorta. One known stent graft system for providing proximal end conformance with the curve, as disclosed in US Publication No. 2022/0211482, the contents of which are incorporated by reference herein in their entirety, includes a proximal alignment stent and a sealing stent distal of the alignment stent where a diameter reduction loop first end is attached to the distal end of the sealing stent, the loop extends circumferentially about the stent graft, and the second end of the loop engages a trigger wire. In particular, two opposing loops' first ends may be attached to the stent and the loops extend in opposite directions about the stent graft with the second ends of the loops meeting to engage a release wire.

BRIEF SUMMARY

Disclosed is a medical device system for at least partially constricting a medical device including a tubular medical device, the medical device comprising a tubular graft body having a proximal end and a distal end; a diameter reducing arrangement configured for constricting a diameter of the medical device, the diameter reducing arrangement including a strand section having first and second ends and being secured to the medical device at the first end and at the second end, the second end being a first circumferential distance from the first end by way of a path along the strand section; wherein, in a constricted configuration of the medical device, a first portion of the strand section extends back on itself to form a first double-stranded tail leading to a first loop, the first double-stranded tail extending circumferentially against the graft body to constrict the medical device by the strand section restricting the first circumferential distance between the first and second ends of the strand section.

The first and second ends of the strand section are immovably secured to the medical device, and the first portion of the strand section passes and is laid double circumferentially beyond the first end to form the first tail and first loop. The first circumferential distance traverses and defines a first circumferential region of the medical device, and in an expanded configuration of the medical device, at least a majority of the strand section is disposed in the first circumferential region of the medical device. Further, in an expanded configuration of the medical device at least a majority of the first portion is disposed in the first circumferential region of the medical device. In the constricted configuration, the first circumferential distance traverses and defines a first circumferential region of the medical device, and wherein, in the constricted configuration, the first portion extends outside the first circumferential region. The first loop is retained by a release mechanism, which may be one or more trigger wires to hold the medical device in the constricted configuration.

In the expanded configuration, the first and second ends of the strand section define first and second mutually exclusive circumferential regions of the stent graft with the first circumferential region of the stent graft extending from the first end to the second end of the strand section. Further, in the expanded configuration of the medical device, the first circumferential region extends around at least 1/7 of the circumference of the medical device, preferably at least ½ and most preferably in the range of ½ to ⅚ of the circumference of the medical device.

The medical device may be a stent graft including at least one stent attached to the tubular graft body. The stent may be a proximal most body stent, and the strand section may be attached to the tubular graft body at the distal end of the stent. The strand section may engage distal apices of the stent to constrict the distal end of the stent.

Further disclosed is a diameter reduction system for a medical device having a tubular graft body having a proximal end and a distal end; a stent disposed about the tubular graft body adjacent the proximal end of the tubular graft body and at least partially overlapping the tubular graft body; and a diameter reducing arrangement configured for constricting a diameter of the stent, the diameter reducing arrangement including a strand section having first and second ends. The first end is attached to the stent at a first point on the stent and the second end is attached to the stent at a second point circumferentially spaced from the first stent to define a first circumferential distance from the first end by way of a path along the strand section to the second end, In an expanded configuration, the first circumferential distance traverses and defines a first circumferential region of the tubular graft body in which a majority of the strand section is disposed, and in a constricted configuration of the medical device, a first portion of the strand section extends back on itself to form a first double-stranded tail leading to a first loop and a second portion of the strand section extends back on itself to form a second double-stranded tail leading to a second loop. Further, in the constricted configuration, the first double-stranded tail and the second double-stranded tail extend circumferentially about a surface of the graft body in opposite directions to constrict the stent to restrict the first circumferential distance between the first and second ends of the strand section. The first and second loops engage at least one releasable wire, which may be a trigger wire.

In the constricted configuration the strand section entirely encircles the tubular graft and in the expanded configuration only partially encircles the graft. The strand section may be woven in and out of the tubular graft body and the first end may be permanently and immovably knotted to a first apex and the second end may be permanently and immovably knotted to a second apex. In the expanded configuration, the stent has a first distal apex within the first circumferential region, a second distal apex within the first circumferential region, and a third distal apex disposed between the first and second distal apices and outside of the first circumferential region, and wherein the first end is secured to the first distal apex, the second end is secured to the second distal apex.

The strand section may be a diameter reduction strand, such as a length of suture, which has a first terminal end immovably attached to the tubular body at one point on the tubular body and a second terminal end immovably attached to a point on the tubular body circumferentially spaced from the first point to define a length of the diameter reducing strand between the first and second point. In a constricted configuration, a first portion of the diameter reduction strand at the first end extends back on itself to form a first double-stranded tail leading to a first loop, the diameter reduction strand is disposed fully circumferentially about the tubular body, and a releasable wire engages the first loop, and in an expanded configuration, the diameter reducing strand is disposed only partially circumferentially about the body, and upon release of the releasable wire, the first loop is released from its looped configuration. In the constricted configuration a second portion of the diameter reduction strand at the second end extends back on itself to form a first double-stranded tail leading to a second loop engaged with the releasable wire, and upon release of the releasable wire, the second loop is released from its looped configuration.

Also described is a medical device, comprising a tubular medical device comprising a tubular graft body having a proximal end and a distal end; a diameter reducing arrangement configured for constricting a diameter of the medical device, the diameter reducing arrangement including a strand section. In the constricted configuration of the medical device, a first portion of the strand section extends back on itself to form a first double-stranded tail leading to a first loop, the first double-stranded tail extending circumferentially against the graft body to constrict the diameter of the medical device.

The various embodiments of the invention, as described in detail below, can help prevent the Bird Beak configuration (stent graft malposition) in the curvature of the aortic arch, thus creating an improved chance of procedural success. Also, the diameter reduction arrangement of the invention may be used to constrain a section or all of the stent graft, making it possible to rotate, align and re-align the stent graft.

FIGS.1A-Dshow a diameter reduction system for reducing the diameter of a medical device. As shown, the system10includes a tubular medical device in the form of a stent graft12. The stent graft12is intended to be implanted in a vessel of the human body, such as the thoracic aorta and/or the aortic arch.FIGS.1A-Dshow the stent graft from various sides—of the stent graft with the stent graft in a fully expanded configuration. The stent graft12includes a tubular graft body14including a proximal open end16and a distal open end (not shown), an inner lumen between the proximal and distal ends, and a graft wall.

As shown, the stent graft12includes a plurality of body stents18attached to and supporting the graft body14. The body stents18each form a ring or hollow cylinder for supporting patency of the lumen of the graft body14. As shown, the body stents18are Z-stents each have a proximal end and a distal end, with struts in a zig-zag pattern around the circumference linking a plurality of proximal apices at the proximal end of the stent to a plurality of distal apices at the distal end of the stent. However, other types of body stents can be used. The body stents can be internal to the stent graft, external to the stent graft or a combination of both. Alternatively, the body stents18can be omitted entirely.

The stent graft includes a sealing stent20located at and supporting the proximal end16of the graft body14. The sealing stent20forms a ring or hollow cylinder for supporting patency of the lumen of the graft body14at the proximal end. At least a majority of the sealing stent is overlapped by the graft body14. As shown, the sealing stent20is entirely overlapped by the graft body14. The sealing stent20is a Z-stent having a proximal end and a distal end, with struts in a zig-zag pattern around the circumference linking a plurality of proximal apices at the proximal end of the stent20to a plurality of distal apices at the distal end of the stent20. Nevertheless, in other embodiments other types of stent can be used for the sealing stent. As shown, the sealing stent is an internal stent, however, it can be an external stent in other embodiments. The sealing stent20is attached to the graft body14by one or more sutures, although in other embodiments other forms of attachment can be used.

The stent graft12may also include a bare stent22as shown in the figures, however, this is not necessary in every embodiment. The bare stent22has a proximal end and a distal end, with struts in a zig-zag pattern linking a plurality of proximal apices at the proximal end of the stent20to a plurality of distal apices at the distal end of the stent20. The distal apices are attached to the graft body14at the proximal end16of the graft body14, and the bare stent22extends proximally of the graft body14. As shown, the proximal apices of the bare stent22are more rounded and have a greater radius of curvature than the distal apices thereof to reduce pressure exerted on a vessel wall when deployed. Stents having differing radii of curvature of the proximal and distal apices are disclosed in US Publication No. 2009/0171437, the disclosure of which is incorporated by reference herein in its entirety. For example, the radius of curvature of the proximal apices may range from about 3.0 mm to 10.0 mm and the radius of curvature of the distal apices may range from about 0.5 mm to about 1.75 mm. The stents of the stent graft12may be self-expanding, balloon expandable, or a combination of self-expanding and balloon expandable stents.

The system10includes a diameter reducing arrangement for constricting the stent graft, in particular the sealing stent20, although the arrangement can be applied to any of the stents. The diameter reducing arrangement includes a strand section24, for example, as shown here, a length of suture. The strand section24has a terminal first end26and a terminal second end28which, as shown, may be longitudinally level. In other words, the first and second ends26,28are longitudinally level ends of the strand of suture disposed the same longitudinal distance from the proximal edge of the stent graft. The strand section24is preferably immovably secured to the stent graft12at the first end26and at the second end28, in each case by being tied to the sealing stent20with a knot, although the first and second ends can be immovably secured to the stent graft in other fashions. The first and second ends26,28may also be secured to just the graft material, or to both the graft and a stent.

As shown inFIG.2, when the stent graft is in the expanded configuration, the second end28is fixed to the stent graft at one point27on the stent graft a first circumferential distance away from an attachment point25the first end26by way of a path along the strand section. In other words, travelling along the strand section24from the first end26to the second end28will result in finishing the first circumferential distance away from the first end26. The first circumferential distance thereby traverses and defines a first circumferential region30of the stent graft where the strand section encompasses the first circumferential region30of the stent graft circumferentially between the first26and second28ends. In this manner, when the stent graft is in the expanded configuration, the first and second ends26,28of the strand section24define first30and second30′ mutually exclusive circumferential regions of the stent graft between them, the first circumferential region30of the stent graft being from the first end26to the second end28of the strand section, and the second circumferential region30′ being the remainder of the circumference of the stent graft.

InFIG.2, the strand section24is shown to encompass about ⅘ of the circumference of the stent graft in the expanded configuration. That is to say that the first circumferential region30extends around ⅘ of the circumference of the stent graft. However, in other embodiments the strand section24may encompass different proportions of the circumference (and the first circumferential region may extend around different proportions of the circumference) in the expanded configuration of the stent graft, preferably at least 1/7, more preferably at least ½ and most preferably in the range of ½ to ⅚ of the circumference.

In the expanded configuration shown inFIG.1, the strand section extends circumferentially from the first end26to the second end28. As it does so, the angle formed between an arbitrary radius of the stent graft and a radius of the stent graft to a point on the strand section24, can be considered to increase monotonically as the point travels along the strand section24from the first end26to the second end28. In other words, in the expanded configuration, all of the strand section24from the first end to the second end is disposed in the first circumferential region30.

Because the first end and the second end are longitudinally level, the strand section24extends in a single plane from the first end26to the second end28in the expanded configuration. The plane is perpendicular to the longitudinal axis of the stent graft. This minimises the profile of the device and avoids hanging loops. The strand section24remains slack in the expanded configuration of the stent graft but is sewn to match the expanded diameter of the graft. In other words, the length of the strand section24is slightly greater than (no more than 5% greater than) the circumferential distance from the first end of the strand section24to the second end of the strand section24when the stent graft is in the expanded configuration. In this way the strand section will not inhibit expansion but will also not have excess suture.

The strand section24, including the first and second ends26,28thereof, are disposed at and configured to constrict a portion of the sealing stent20, preferably the distal end of the sealing stent20. Inn particular the strand section24is disposed at and configured to constrict distal apices of the sealing stent20. The strand section is disposed about the graft and through a majority of the distal apices of the sealing stent20. For example, the strand section is woven in and out of the graft material and through a majority of the distal apices.

FIG.2shows a cross-section through the stent graft system10ofFIG.1in the region of the strand section24and looking distally. As shown inFIGS.1and2, from the first end26to the second end28, the strand section24passes generally around the outside of the graft body14except that it passes around the inside of the second strut of each distal apex of the sealing stent20that it passes (with the exception of the apex where the second end28is attached), penetrating to the interior of the graft body14on one side of the strut and returning to the outside of the graft body14on the other side of the strut, before passing to the adjacent apex on the outside of the graft body14. For the apex where the second end28is attached, the strand section passes around the inside of the first strut in the manner described above, and is then knotted to the second strut.

As shown inFIGS.1-2, in the expanded configuration of the stent graft the first26and second28ends are circumferentially spaced and the strand section has a length from the first end26to the second end28which is less than the circumference of the stent graft12in the expanded configuration, although this is not necessary in every embodiment. As a result, some apices and interstices are free from the strand section in the expanded configuration of the stent graft. The stent graft ofFIG.1has a diameter in the expanded configuration of 40-42 mm and the sealing stent20has seven distal apices and seven proximal apices, although any expanded configuration can be used and the number of apices does not need to be the same in every embodiment, as described in more detail below.

As shown, six distal apices of the sealing stent20and their five intermediate distal interstices are sewn (herein sewn apices/interstices are those that in the expanded configuration of the stent graft are located in the first circumferential region30and have the strand section24pass them and, in the case of apices, preferably have the strand section sewn over a strut thereof, as shownFIG.2). Also as shown inFIG.2, one distal apex31, together with the two adjacent distal interstices23,25, (as well as two proximal apices) of the sealing stent20are free (herein free apices/interstices are those that in the expanded configuration of the stent graft are located outside the first circumferential region30—in other words are in the second circumferential region—and are free from the strand section, that is are not passed by the strand section). This gives a ratio between the circumferential extent of the first circumferential region and the circumferential extent of the second circumferential region of about 5:2. As shown inFIG.2, the first and second ends26,28of the strand section are knotted to distal apices adjacent to and either side of the free distal apex31, in particular to the struts thereof that are adjacent to the free distal apex31.

A constricted configuration of the stent-graft is shown inFIG.3. In the constricted configuration, a first portion32of the strand section extends back on itself to form a first double-stranded tail34leading to a first loop36. In particular, from the first circumferential region30the first portion32passes the first end26and extends outside the first circumferential region30into the second circumferential region, where it is laid double circumferentially beyond the first end26to form the first tail34and first loop36. As shown, the first tail34extends double-stranded circumferentially against the graft body, that is against a surface of the graft body, in this embodiment around part of the exterior of the graft body14, constricting the stent by the strand section restricting the first circumferential distance between the first and second ends26,28of the strand section24. In particular, the first portion32extending into the second circumferential region and being laid double reduces the length of strand section24that is disposed in the first circumferential region30, thereby forcibly constricting the first circumferential region30.

Similarly, as shown inFIG.3, a second portion38of the strand section24extends back on itself to form a second double-stranded tail40leading to a second loop42. In particular, from the first circumferential region30the second portion38passes the second end28and extends outside the first circumferential region30into the second circumferential region, where it is laid double circumferentially beyond the second end28to form the second tail40and second loop42. Similarly to the first tail34, the second tail40extends double-stranded circumferentially against the graft body14, that is against a surface of the graft body, in this embodiment around part of the exterior of the graft body14, constricting the stent by the strand section24restricting the first circumferential distance between the first and second ends26,28of the strand section. In particular, the second portion38extending into the second circumferential region and being laid double reduces the length of strand section24that is disposed in the first circumferential region30, thereby forcibly constricting the first circumferential region30. As shown, a majority of each of the first and second tails34,40is against an exterior surface of the graft body14. As it further can be seen, the first and second tails34,40extend against the graft body14in opposite circumferential senses, meaning that a circumferential direction along the first tail34towards the first loop36is in an opposite circumferential sense from a circumferential direction along the second tail40towards the second loop42.

As shown inFIG.3, the first and second tails34,40pass through the wall of the graft body14into the interior of the graft body such that the first and second loops36,42are internal to the graft body. As shown The first and second tails34,40pass through the wall of the graft body14between the struts of the free distal apex31, which can be referred to as the holding apex31, as it is where the tails pass through the wall to be retained. The holding apex31is in this embodiment configured to be on the outside of the curve when the stent graft is placed in a curved body vessel. As shown In the constricted configuration of the stent graft, every distal apex of the sealing stent20is overlapped by the strand section, whether on the inside or the outside. However, while preferable, this is not essential in every embodiment.

For the purposes of deployment, an introducer assembly includes a release mechanism including a trigger or release wire44, which passes through the lumen of the graft body14. In the constricted configuration of the stent graft, the first and second loops36,42are retained and locked by the trigger wire44internally to the graft body14to hold the stent graft in the constricted configuration. However, the first and second loops36,42, may be retained and locked by the trigger wire44externally to the graft body14to hold the stent graft in the constricted configuration. Further, the first and second loops36,42are retained and locked by the trigger wire44both internally and externally to the graft body14to hold the stent graft in the constricted configuration, for example where the trigger wire extends in and out of the graft material of the graft body along its length. As shown inFIG.4, the trigger wire44passes through both loops36,42. However, in other embodiments, one loop (loop A) can pass through the other loop (loop B), and the trigger wire can pass through loop A, as shown inFIG.5.

InFIG.5, loop A is the first loop36and loop B is the second loop42, but they could be the other way around in other embodiments.FIGS.6to7and9show an arrangement including the system ofFIG.1in the delivery state and the introducer assembly, the introducer assembly including a delivery device onto which the stent graft is mounted in the constricted configuration. The delivery device includes a urethane tubing (UAT)50and a nose cone52coupled to the UAT50at the end which would be furthest from the clinician during a procedure. The UAT50extends through the lumen of the graft body14and the stent graft12is constricted about the UAT50.

As shown in inFIG.7for example, the bare stent22is held to the UAT at its proximal apices in a conventional manner using bare stent trigger wires54which extend through the UAT, and out of the UAT to loop around one or more proximal apices of the UAT, and return into the UAT to extend within the UAT to be secured within the UAT or within the nose cone52. Here, the trigger wire44is separate from the bare stent trigger wires54, but in other embodiments the trigger wire44can also serve as a bare stent trigger wire. As shown, the trigger wire44is attached to the UAT on the inside of the graft. The trigger wire44extends from a manipulation section (not shown) through the UAT, and extends out of the UAT in the region of the stent graft to pass through the loops36,42as discussed above, and return into the UAT to extend within the UAT to be secured within the UAT or within the nose cone52.

However, in other embodiments, the trigger wire44can be fixed to the side of the UAT rather than extending within it, or can be ‘floating’, in that it is not held against or in the UAT but is independent of the UAT and secured at the nose cone52, as shown inFIG.8, which is otherwise the same as the arrangement ofFIG.7. With a ‘floating’ trigger wire, the trigger wire can optionally retain the first and second loops36,42on the outside of the graft body14, in which case the first and second tails34,40do not need to pass through the wall of the graft body. As shown, the trigger wire44retains the loops36,42such that they will be on the outside of the curve when introduced into the aorta.

In a method of making the stent graft system, a stent graft is provided in the expanded configuration and the strand section is applied to the stent graft using a needle or other appropriate tool in order to form the system shown inFIG.1. The materials and tools for making the stent graft system and constricting the stent graft can be standard materials and tools for fabrication of stent grafts. In the method, with the stent graft in the expanded configuration as shown for example inFIG.1, all of the strand section is disposed in the first circumferential region30. The method includes pulling the first portion32of the strand section24to form the first loop36and the first double-stranded tail34leading to the first loop36. The method includes using a conventional stylet or pert (although other tools can be used in other embodiments) to lift the strand section24adjacent to the first end26away from the surface of the graft body14, thereby forming a bight which forms the first portion32and the first loop36. The first loop36then is pulled by the stylet or pert, thereby pulling more of the strand section24into the first portion32, thereby constricting the stent graft and producing the first tail34.

The method includes pulling the first loop36past and circumferentially beyond the first end26, outside the first circumferential region30into the second circumferential region, and extending the first tail34circumferentially against the graft body in the second circumferential region, in this embodiment around part of the exterior of the graft body14. As discussed, this constricts the stent by restricting the first circumferential distance between the first and second ends of the strand section24. The method also includes pulling the second portion38of the strand section24to form the second loop42and the second double-stranded tail40leading to the second loop42.

The method includes using the stylet or pert to lift the strand section24adjacent to the second end28away from the surface of the graft body14, thereby forming a bight which forms the second portion38and the second loop42. The second loop42then is pulled by the stylet or pert, thereby pulling more of the strand section24into the second portion38, thereby constricting the stent graft and producing the second tail40. Similarly to the first loop36, the method includes pulling the second loop42past and circumferentially beyond the second end28, outside the first circumferential region30into the second circumferential region, and extending the second tail40circumferentially against the graft body in the second circumferential region, in this embodiment around part of the exterior of the graft body14. As discussed, this constricts the stent by restricting the first circumferential distance between the first and second ends of the strand section24. The method includes extending the first tail34and second tail40through the wall of the graft body into the interior of the graft body and looping the first loop36and the second loop42around the trigger wire44at the interior of the graft body as discussed above.

In use, the stent graft system is introduced into a vessel, in this embodiment into the aorta, endoluminally in a conventional manner with the stent graft in the constricted configuration. Once the stent graft is at the desired deployment site, the stent graft can be partially deployed, for example by retraction of a sheath (not shown). The stent graft can then be fully deployed and implanted in the vessel by retraction of the trigger wire44.

Once the trigger wire is retracted from the loops36,44, the sealing stent20is free to expand, allowing the stent graft12to expand to the expanded configuration and come into apposition with the vessel walls. This will happen automatically because the stents are self-expanding stents, but in other embodiments the sealing stent20and/or other stents may be expanded for example using a balloon.

As the sealing stent20expands, the first and second tails34,40are pulled out from the interior of the graft body14, and the first and second portions32,38are pulled back into the first circumferential region30. This retraction maintains a low profile for the device during expansion, while retrieving the loops36,42from the interior of the stent graft, thereby minimising any potential undesired interaction of the strand section and loops with other components.

FIGS.10ato10dshow a system according to another embodiment of the invention with the stent graft in the expanded configuration. The embodiment ofFIGS.10ato10dis the same as the embodiment ofFIG.1, including details of manufacture and use, except that the stent graft has a diameter in the expanded configuration of 44 to 46 mm, and the sealing stent has 8 distal apices and 8 proximal apices. As with the system of the embodiment ofFIG.1, there is only one free distal apex (with its two adjacent distal interstices also free) in the expanded configuration of the stent graft, which means that in this embodiment there are seven sewn distal apices with six sewn intermediate distal interstices, and a ratio of the circumferential extent of the second circumferential region to the circumferential extent of the first circumferential region of 1:3.FIG.11shows a cross-section of the system ofFIG.10in the expanded configuration,FIG.11being a cross-section through the stent graft system ofFIG.10in the region of the strand section and looking distally.

FIG.12shows a cross-section of the system ofFIG.10from the same perspective asFIG.11, but with the stent graft in the constricted configuration. As shown, the constricted configuration is formed and configured in a similar manner to the embodiment ofFIG.1.

FIG.13is a cross-sectional view of a system as per the embodiment ofFIG.1, the cross-section being through the stent graft system in the region of the strand section with the stent graft in the constricted configuration and looking distally. As represented byFIG.13(andFIGS.14to18), the number of sewn distal apices/interstices of the sealing stent can be varied. In addition, the number of free distal apices/interstices of the sealing stent can also be varied. For example, there can be more than or less than one free distal apex and two free distal interstices of the sealing stent. In an expanded configuration of the stent graft a ratio of the number of distal apices of the sealing stent in the second circumferential region (that is free distal apices) to the number of distal apices in the first circumferential region (that is sewn distal apices) may depend on the application. However, preferably this ratio is in the range of 1:2 to 1:7 as this is likely to cover most applications. A preferred ratio between the circumferential extents of the second and first circumferential regions in the expanded configuration of the stent graft is from 1:2 to 1:5. A preferred ratio between the number of distal interstices of the sealing stent in the second circumferential region to the number of distal interstices of the sealing stent in the first circumferential region in the expanded configuration of the stent graft is from 1:2 to 1:5. This ratio can be achieved with any of the configurations depicted in the accompanying figures.

Examples of the number of free distal interstices (in the second circumferential region) to sewn distal interstices (in the first circumferential region) in the expanded configuration of the stent graft for sealing stents with different total numbers of distal apices are given in the following table.

Sewn distalFree distalinterstices betweenintersticesdistal apicesStent total(in the second(in the firstnumber ofcircumferentialcircumferentialdistal apicesregion)region)Ratio5141/46151/57252/58261/39272/710373/711383/812391/3133103/10144102/5
As shown, in the embodiment ofFIG.13, together the first and second tails34,40span two distal interstices in the constricted configuration of the stent graft. Preferably the first and second tails34,40are arranged symmetrically in the constricted configuration of the stent graft in that they extend against the graft body14for the same distance and overlap the same number of apices of the sealing stent20, as in the systems described above. However, in other embodiments they can be arranged in an asymmetric manner. For example, they can extend against the graft body14for different lengths, and/or the free distal apex of the sealing stent20can be fully or partially spanned by one of the tails and not the other tail, and/or if there is more than one free distal apex of the sealing stent20, one tail can span more of the free distal apices than the other tail. One tail can span more free distal interstices of the sealing stent20than the other.

Furthermore, although in the above embodiments there are first and second portions32,38forming first and second tails34,40, it is possible in some embodiments to just use one portion forming one tail and loop. It is also possible in other embodiments to use multiple strand sections around different parts of the circumference of the stent graft, each configured as described herein, and thereby have any number of tails and loops, however preferably such that every distal apex of the sealing stent is overlapped by a strand section in the constricted configuration of the stent graft.

One example of a system which uses one tail and one loop is shown inFIG.14.FIG.14is a cross-section through the stent graft system in the region of the strand section24′ and looking distally, with the stent graft in the constricted configuration. The embodiment ofFIG.14is the same as the embodiment ofFIG.1orFIG.10, including details of manufacture and use, with the following changes. As shown, the second portion, second tail, and second loop are not present in this example. The first portion32, first tail34and first loop36are the same as in the system ofFIG.1, but there is no completely free apex in this example.

As shown inFIG.14, the holding apex31′ is partially free (in other words it is partially in the first circumferential region and partially in the second circumferential region). Only one of the distal interstices of the sealing stent is free, adjacent to the holding apex31′. In particular, the second end28′ of the strand section24′ is located at one strut of the holding apex31′ with the other strut being free. As shown inFIG.14, in the constricted configuration the first tail34passes the free distal interstice over the free strut of the holding apex31′ and through the wall of the graft body14between the struts of the holding apex31′ where it is retained by the trigger wire44(not shown inFIG.14) internally to the graft body14. Therefore, in the constricted configuration of the stent graft, the first tail spans a single distal interstice.

FIG.15is a view of a system according to an embodiment which is the same as the embodiment ofFIG.14, including details of manufacture and use, except as discussed below.FIG.15is a cross-section through the stent graft system in the region of the strand section and looking distally, with the stent graft in the constricted configuration. In the system ofFIG.15, in addition to the holding apex31′ which is partially free, there is also a completely free second distal apex56between the first end26of the strand section and the holding apex31′. There are therefore two free distal interstices of the sealing stent, both to the same side of the holding apex31′, with one on each side of the second apex56. As discussed earlier, what is meant by a free distal apex/interstice is a distal apex/interstice of the sealing stent that is in the second circumferential region, and is therefore not spanned by the strand section24in the expanded configuration of the stent graft12.

As shown inFIG.15, in the constricted configuration of the stent graft12, the first tail34′ is sewn through the second apex56. In other words, a majority of the first tail34′ extends around the outside of the graft body14from the first end26of the strand section24to the holding apex31′; however it passes around the inside of the first strut of the second apex56, penetrating to the interior of the graft body14on one side of the strut and returning to the outside of the graft body14on the other side of the strut, before passing to the holding apex31′ on the outside of the graft body14. In other words, the first tail34′ spans one and a half distal apices and two distal interstices in the constricted configuration of the stent graft.

FIG.16is a view of a system according to an embodiment which is the same as the embodiment ofFIG.15, including details of manufacture and use, except as discussed below.FIG.16is a cross-section through the stent graft system in the region of the strand section and looking distally, with the stent graft in the constricted configuration. Further to the system ofFIG.15, the system ofFIG.16additionally includes the second portion38, second tail40, and second loop42of the system ofFIG.1and, as perFIG.1, the second end28of the strand section is located at a distal apex adjacent to the holding apex31but on the opposite side from the second apex56. The first and second loops36,42are retained by the trigger wire (not shown inFIG.16) as discussed in respect of the system ofFIG.1. In this embodiment, therefore, three distal interstices of the sealing stent are together spanned by the first and second tails in the constricted configuration of the stent graft.

FIG.17is a view of a system according to an embodiment which is the same as the embodiment ofFIG.16, including details of manufacture and use, except as discussed below.FIG.17is a cross-section through the stent graft system in the region of the strand section and looking distally, with the stent graft in the constricted configuration. In the system ofFIG.17, in addition to the holding apex31″ and the second apex56, which are completely free, there is also a completely free third distal apex58located on the opposite side of the holding apex31″ from the second apex56and located between the second end28of the strand section and the holding apex31″. There are therefore four free distal interstices of the sealing stent, two on each side of the holding apex31′, which are laid out with one on each side of the second apex56, and one on each side of the third apex58. As discussed earlier, what is meant by a free distal apex/interstice is a distal apex/interstice of the sealing stent that is in the second circumferential region, and is therefore not spanned by the strand section24in the expanded configuration of the stent graft12.

As shown inFIG.17, in the constricted configuration of the stent graft12, the second tail40′ is sewn through the third apex58. In other words, a majority of the second tail40′ extends around the outside of the graft body14from the second end28of the strand section24to the holding apex31″; however it passes around the inside of the second strut of the third apex58, penetrating to the interior of the graft body14on one side of the strut and returning to the outside of the graft body14on the other side of the strut, before passing to the holding apex31′ on the outside of the graft body14. In other words, the second tail40′ spans one and a half distal apices and two distal interstices in the constricted configuration of the stent graft, meaning that together the first and second tails span four distal interstices in the constricted configuration of the stent graft.

As shown inFIG.17, in this system the first tail passes around the inside of the second strut of the second apex56rather than the inside of the first strut of the second apex56as inFIG.16(the numbering of the strut representing the circumferential order away from the end of the strand section24from which the respective tail extends). However, where the strand section24and/or tails24,40pass around the inside of one strut of an apex, either strut can be selected.

In addition to the above, it is possible in some embodiments for the tails to pass through the wall of the graft body at different locations from each other.

FIG.18is a view of a system according to an embodiment which is the same as the embodiment ofFIG.1, including details of manufacture and use, except as discussed below.FIG.18is a cross-section through the stent graft system in the region of the strand section and looking distally, with the stent graft in the constricted configuration.

As shown inFIG.18, in this system there are first31aand second31bholding apices in the second circumferential region. In this embodiment these are adjacent distal apices of the sealing stent, but in other embodiments they could be separated by further intermediate distal apices. The first tail34″ passes through the wall of the graft body14between the struts of the first holding apex31aand the second tail40″ passes through the wall of the graft body14between the struts of the second holding apex31b. The first and second loops36″,42″ are retained by the trigger wire as discussed above. In this embodiment, therefore, the first and second tails together span three distal interstices in the constricted configuration of the stent graft.

It is possible in some embodiments for the first and second loops to be retained by different trigger wires. However, it is preferable for them to be retained by the same trigger wire so that the sealing stent20expands symmetrically. Although in the above embodiments the strand section is configured to constrict the sealing stent, in other embodiments it can be configured to constrict other stents along the graft body.

As discussed above, the first and/or second tails extend around part of the exterior of the graft body in the constricted configuration, however, it is not excluded that they can extend against an interior surface of the graft body in some embodiments for example such that a majority of each of the first and/or second tails extends against an interior surface of the graft body.

Although, the first and second tails are shown extending from the first and second ends of the strand section, in other embodiments the first and second tails can extend from other points of attachment of the strand section to the stent graft, such as points where the strand section loops around a strut at an apex of the sealing stent. This can be done for example by pulling a bight of the strand section circumferentially past these points. However, such embodiments are less preferable as they result in the strand section being laid triple in the regions of the tails.

Although, as shown the strand section is disposed at the distal end of the stent to be constricted, in other embodiments it can be disposed at any longitudinal location of the stent to be constricted, or even longitudinally offset from the stent to be constricted. Further, although all of the strand section from the first end to the second end is disposed in the first circumferential region in the expanded configuration, this is not necessary in every embodiment. In some embodiments it is possible that the first and/or second portion extends slightly outside the first circumferential region in the expanded configuration. However, this is not preferred as having all of the strand section in the first circumferential region can minimise the profile of the device. Preferably, at least a majority of the strand section, including a majority of the first portion and/or second portion, is disposed in the first circumferential region of the stent graft in the expanded configuration.

Although the tubular medical device to be constricted is disclosed as a stent graft including a stent, this is not essential in every embodiment. The diameter reducing arrangement may be used to constrain any tubular medical device from one diameter to a smaller diameter.

All optional and preferred features and modifications of the described embodiments and dependent claims are usable in all aspects of the invention taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.

The disclosures in the abstract accompanying this application are incorporated herein by reference. Although the embodiments are described separately, the features of an embodiment may be included with other embodiments.