Double- and triple-branching ascending aortic stent-graft systems

Abstract

A stent-graft (222) is provided that includes a fluid flow guide (28) shaped so as to define proximal and distal fluid-flow guide end openings, (27A, 27B), a fluid flow lumen (29) therebetween, and a fluid-flow guide lateral opening (30). The stent-graft (222) is removably disposed within a delivery catheter (80A) with the distal fluid-flow guide end opening (27B) facing a distal catheter end (82). A sheath-rail guidewire (50C) is removably positioned passing sequentially through (1) the delivery catheter proximal to the proximal fluid-flow guide end opening (27 A), (2) the proximal fluid-flow guide end opening (27 A), (3) a longitudinal portion of the fluid flow lumen (29), (4) the fluid-flow guide lateral opening (30) to outside the fluid flow lumen (29), and (5) the distal catheter end (82). A nosecone (86) is removably coupled to the distal catheter end (82). A fixation tube (248) is disposed at least partially distal to the nosecone (86). The sheath-rail guidewire (50C) is coupled to an external surface of the fixation tube (248). Other embodiments are also described.

Description

[0001] DOUBLE- AND TRIPLE-BRANCHING ASCENDING AORTIC STENT-GRAFT SYSTEMS

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application:

[0004] (i) claims priority from (a) US Provisional Application 63 / 567,652, filed March 20, 2024, (b) US Provisional Application 63 / 643,063, filed May 6, 2024, and (c) US Provisional Application 63 / 695,067, filed September 16, 2024, and

[0005] (ii) is a continuation-in-part of International Application PCT / IL2023 / 051002, filed September 14, 2023, which published as PCT Publication WO 2024 / 057320 to Avisar et al., and which claims the benefit of US Provisional Application 63 / 406,955, filed September 15, 2022.

[0006] All of the above-referenced applications are assigned to the assignee of the present application and incorporated herein by reference.

[0007] FIELD OF THE APPLICATION

[0008] The present application relates generally to prostheses and surgical methods, and specifically to tubular prostheses, including endovascular stent-grafts, and surgical techniques for using the prostheses to maintain patency of body passages such as blood vessels, and treating aneurysms, dissections, aortic ulcers, and intramural hematomas of arterial walls.

[0009] BACKGROUND OF THE APPLICATION

[0010] Endovascular prostheses are sometimes used to treat acute aortic syndrome, which includes aortic aneurysm, aortic dissection, aortic ulcer (e.g., penetrating aortic ulcer (PAU), and intramural hematoma (IMH). Such treatment includes implanting a stent or stent-graft within the diseased vessel to bypass the anomaly. An aneurysm is a sac formed by the dilation of the wall of the artery. Aneurysms may be congenital, but are usually caused by disease or, occasionally, by trauma. Aortic aneurysms which commonly form between the renal arteries and the iliac arteries are referred to as abdominal aortic aneurysms ("AAAs"). Other aneurysms occur in the aorta, such as thoracic aortic aneurysms ("TAAs"), which may occur in one or more of the descending aorta, the ascending aorta, and the aortic arch. Endo-Vascular Aneurysm Repair (EVAR) has transformed the practice of treatment of aortic aneurysms from an open surgical approach to a much less invasive surgical approach. The first step of an endovascular intervention usually requires introducing a delivery system into the vasculature of a patient.

[0011] WO 2014 / 108895 to Shalev et al. describes an endovascular system that includes an endovascular implant and a delivery tool. The implant is configured to assume a radially- compressed delivery state, and a radially-expanded deployment state. The delivery tool includes a proximal main delivery catheter, having a distal portion in which the implant is disposed while in the radially-compressed delivery state; and a distal restraining assembly, which includes a restraining-assembly tubular shaft disposed distal to the proximal main delivery catheter. The distal restraining assembly is configured to assume an engaged state, in which the distal restraining assembly prevents proximal displacement of the implant relative to the distal restraining assembly, and a disengaged state, in which the distal restraining assembly allows proximal displacement of the implant relative to the distal restraining assembly. Other embodiments are also described.

[0012] US Patent 8,267,988 to Hamer et al. describes an expandable prosthetic device and method of delivery that allows the initial placement of multiple guidewires into selected target sites. The prosthesis includes a main body device. This main body device has a separate side branch guidewire lumen that passes through the main body device and through a side opening in the main body device. As the main body device is advanced, the side opening is self-guided (by the side branch guidewire) and self-aligns to the side branch vessel ostium. The main body device is then deployed, leaving the side branch guidewire in place. A side branch device is then advanced along the side branch guidewire through the main body device, through the side wall opening and into the native side branch vessel. The side branch device can then be deployed to engage the main body device and the native side branch vessel.

[0013] US Patent 8,672,989 to Schreck et al. describes an endoluminal prosthesis system deployable in a region of a patient's vasculature having one or more branch vessels, having a main graft body having a first opening in a wall portion of the main graft body and a pre- loaded guidewire positioned inside the main graft body and advanced through the first opening. One or more branch grafts can be attached to the main graft body to cover one or more openings in the main graft body. US Patent Application Publication 2018 / 0021157 to Marmur et al., which is incorporated herein by reference, describes an elongate delivery shaft assembly that includes an outer covering shaft and an inner support shaft. When the delivery shaft assembly is unconstrained and a stent-graft is removably constrained in a radially- compressed delivery state along a distal end portion of the delivery shaft assembly, radially between the outer covering shaft and the inner support shaft: (a) the delivery shaft assembly is shaped so as to define a self-orienting portion, which (i) is shaped so as to define at least proximal and distal curved portions, the proximal curved portion disposed more proximal than the distal curved portion, and (ii) at least one point of inflection on a central longitudinal axis of the delivery shaft assembly longitudinally between the proximal and the distal curved portions, and (b) respective smallest radii of curvature of the proximal and the distal curved portions, measured at the central longitudinal axis, are each between 2.5 and 12 cm.

[0014] SUMMARY OF THE APPLICATION

[0015] In some embodiments of the present invention, a stent-graft system is provided that comprises a main stent-graft, a main delivery catheter, and an elongate member. The main stent-graft is configured to assume a radially-compressed delivery state and a radially- expanded deployment state, and comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which is securely attached to and covers at least a portion of the main-stent-graft stent member, and is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening.

[0016] The main delivery catheter has proximal and distal catheter ends. The main stentgraft is removably disposed within the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that the distal main-fluid-flow guide end opening faces the distal catheter end, and the main- fluid-flow guide lateral opening is at a first angular location with respect to a central longitudinal axis of the main delivery catheter.

[0017] The elongate member, which may comprise, for example, a secondary guidewire, is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening, at the first angular location, to outside the main fluid flow lumen, and (e) the distal catheter end.

[0018] The elongate member exits the distal catheter end at a second angular location with respect to the central longitudinal axis of the main delivery catheter, the second angular location offset from the first angular location around the central longitudinal axis by at least 90 degrees, such as at least 135 degrees, e.g., by 180 degrees. During implantation of the main stent- graft in vasculature of a patient, this angular offset may assist the user with identifying proper rotational alignment of main delivery catheter using less fluoroscopy than would otherwise be necessary without this angular offset.

[0019] In some embodiments of the present application, a method is provided that comprises endovascularly introducing a vascular implant into vasculature of a patient through a vascular access site that is downstream of a first branch of an aortic arch. Thereafter, the vascular implant is advanced through the first branch to the aortic arch. Thereafter, the vascular implant is advanced from the aortic arch at least partially into a second branch of the aortic arch. Thereafter, the vascular implant is deployed at least partially in the second branch.

[0020] In some embodiments of the present application, a guidewire is deployed between (i) a first vascular access site that is downstream of a first branch of the aortic arch and (ii) a second vascular access site that is downstream of a second branch of the aortic arch, such that the guidewire is positioned partially within the first branch, partially within the aortic arch, and partially within the second branch. A vascular implant is advanced over the guidewire and deployed within the vasculature.

[0021] In some embodiments of the present application, a stent-graft system comprises a main stent-graft and an elongate member. The main stent-graft is configured to assume a radially-compressed delivery state and a radially-expanded deployment state. The main stent-graft comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which is securely attached to and covers at least a portion of the main- stent-graft stent member. The main fluid flow guide is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening. The main stent-graft further comprises an internal support channel, which is configured to assume expanded and collapsed states, and is disposed within the main fluid flow guide. The internal support channel comprises a generally tubular channel fluid flow guide, which is shaped so as to define proximal and distal channel-fluid-flow end openings. When the internal support channel is in the expanded state, the internal support channel defines a channel lumen between the proximal and the distal channel-fluid-flow end openings.

[0022] When the internal support channel is in the collapsed state, the distal channel-fluid- flow guide end opening faces radially inward. When the internal support channel is in the expanded state and the main stent-graft is in the radially-expanded deployment state, the distal channel-fluid-flow guide end opening faces at least partially distally within the main fluid flow guide.

[0023] The proximal channel-fluid-flow end opening is sealingly coupled to a perimeter of the main-fluid-flow guide lateral opening, such that the channel lumen is in fluid communication with outside the main fluid flow guide via the main-fluid-flow guide lateral opening when the internal support channel is in the expanded state. An external surface of the internal support channel is coupled to an internal surface of the main fluid flow guide such that the internal support channel runs alongside the internal surface of the main fluid flow guide distally from the main-fluid-flow guide lateral opening. Optionally, the internal support channel is also coupled to portions of the main-stent-graft stent member.

[0024] The elongate member is removably positioned passing sequentially through (a) the proximal main-fluid-flow guide end opening, (b) a longitudinal portion of the main fluid flow lumen, (c) the distal channel-fluid-flow guide end opening, and (d) the main-fluid- flow guide lateral opening to outside the main fluid flow lumen. The internal support channel is configured to automatically transition to the expanded state when not constrained in the collapsed state by the main stent-graft and not constrained in the collapsed state by the elongate member.

[0025] For some applications, the elongate member comprises a secondary guidewire tube that is shaped so as to define a secondary-guidewire-tube lumen for insertion therethrough of a secondary guidewire. For other applications, the elongate member comprises the secondary guidewire.

[0026] In some applications of the present invention, a stent-graft system is provided that comprises a stent-graft and a delivery system, which comprises a delivery catheter. The stent-graft comprises a fluid flow guide and a stent. The stent comprises cylindrical undulating rings and spring links. The cylindrical undulating rings are coupled to the fluid flow guide at respective axial locations along an axis of the fluid flow guide, so as to provide a tubular shape to the fluid flow guide about the axis when the stent-graft is in a radially- expanded deployment state. The spring links are joined to first and second ones of the cylindrical undulating rings.

[0027] The stent-graft is removably disposed within a portion of the delivery catheter such that the delivery catheter constrains the stent- graft in a radially-compressed delivery state in which (a) the spring links are in respective extended tensioned states, and (b) the first and the second cylindrical undulating rings do not axially overlap with each other. This lack of axial overlap allows the radial compression of the stent-graft into a smaller-diameter delivery catheter than would be possible if the first and the second cylindrical undulating rings axially overlapped.

[0028] The stent-graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings. This approximation of the first and the second cylindrical undulating rings may offer a shorter landing (sealing) zone with the vascular wall than if the rings were axially farther apart. The approximation provides a shorter sealing zone and a better seal with the wall of the blood vessel, due to the increased outwardly-directed radial force over the shortened landing zone, i.e., the greater radial force per length.

[0029] There is therefore provided, in accordance with an Inventive Concept 1 of the present invention, a stent-graft system for use with a primary guidewire, the stent-graft system comprising:

[0030] (i) a main stent-graft, which (a) is configured to be deployed over the primary guidewire, (b) is configured to assume a radially-compressed delivery state and a radially- expanded deployment state, and (c) comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which is (1) securely attached to and covers at least a portion of the main- stent- graft stent member, and (2) shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; and

[0031] (ii) a delivery system, which comprises:

[0032] (a) a main delivery catheter having proximal and distal catheter ends, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that the distal main-fluid-flow guide end opening faces the distal catheter end;

[0033] (b) a sheath-rail guidewire, which is removably positioned passing sequentially through (1) at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (2) the proximal main-fluid-flow guide end opening, (3) a longitudinal portion of the main fluid flow lumen, (4) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (5) the distal catheter end;

[0034] (c) a nosecone removably coupled to the distal catheter end; and

[0035] (d) a fixation tube, disposed at least partially distal to the nosecone, wherein the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube.

[0036] Inventive Concept 2. The stent- graft system according to Inventive Concept 1, wherein the fixation tube is removably coupled to a distal end portion of the main stent-graft.

[0037] Inventive Concept 3. The stent- graft system according to Inventive Concept 1, wherein the fixation tube is axially moveable away from the nosecone.

[0038] Inventive Concept 4. The stent- graft system according to Inventive Concept 1, wherein the fixation tube is removably in contact with a distal end portion of the nosecone.

[0039] Inventive Concept 5. The stent-graft system according to Inventive Concept 1, for use with a primary guidewire, wherein the fixation tube is shaped so as to define a lumen for insertion therethrough of the primary guidewire.

[0040] Inventive Concept 6. The stent-graft system according to Inventive Concept 1, wherein the delivery system further comprises a main inner shaft, which is removably disposed at least partially within the main delivery catheter, and wherein the nosecone and the main inner shaft are shaped so as to define respective guidewire longitudinal lumens for insertion therethrough of the primary guidewire.

[0041] Inventive Concept 7. The stent-graft system according to Inventive Concept 1, wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube. Inventive Concept 8. The stent-graft system according to Inventive Concept 1, wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0042] Inventive Concept 9. The stent- graft system according to any one of Inventive Concepts 1- 8, wherein the delivery system further comprises an introducer sheath, which is configured to be introduced into vasculature of a patient over the sheath-rail guidewire.

[0043] Inventive Concept 10. The stent-graft system according to Inventive Concept 9, wherein the delivery system further comprises a cannulating guidewire.

[0044] Inventive Concept 11. The stent-graft system according to Inventive Concept 10, wherein the delivery system further comprises a cannulating catheter, which is configured, while the cannulating guidewire is disposed at least partially within the cannulating catheter, to be introduced into a proximal end of the introducer sheath, and advanced through the introducer sheath and out of a distal end of the introducer sheath.

[0045] Inventive Concept 12. The stent-graft system according to any one of Inventive Concepts 1-8, wherein the stent-graft system further comprises a branching stent-graft, which: comprises a flexible branching-stent-graft stent member and a generally tubular branching- stent-graft fluid flow guide, and is configured to be disposed through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between the branching-stent-graft fluid flow guide and a portion of the main- stent- graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

[0046] Inventive Concept 13. The stent-graft system according to any one of Inventive Concepts 1-8, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, the at least a portion of the main delivery catheter is at least a first portion of the main delivery catheter, and the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein the main fluid flow guide is shaped so as to further define a second main- fluid-flow guide lateral opening, and wherein the delivery system further comprises: an elongate member, which is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main -fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end.

[0047] Inventive Concept 14. The stent-graft system according to Inventive Concept 13, for use with a secondary guidewire, wherein the elongate member comprises a secondary guidewire tube, which is shaped so as to define a secondary-guidewire-tube lumen for insertion therethrough of the secondary guidewire.

[0048] Inventive Concept 15. The stent-graft system according to Inventive Concept 13, wherein the elongate member comprises a secondary guidewire.

[0049] Inventive Concept 16. The stent-graft system according to Inventive Concept 13, wherein the stent-graft system further comprises first and second branching stentgrafts, which comprise first and second flexible branching-stent-graft stent members and first and second generally tubular branching-stent-graft fluid flow guides, respectively, wherein the first branching stent-graft is configured to be disposed through the first main-fluid-flow guide lateral opening so as to form a blood-tight seal between the first branching- stent-graft fluid flow guide and a first portion of the main- stent- graft fluid flow guide that defines a first perimeter of the first main-fluid-flow guide lateral opening, and wherein the second branching stent-graft is configured to be disposed through the second main-fluid-flow guide lateral opening so as to form a blood-tight seal between the second branching-stent-graft fluid flow guide and a second portion of the main-stent-graft fluid flow guide that defines a second perimeter of the second main-fluid-flow guide lateral opening.

[0050] There is further provided, in accordance with an Inventive Concept 17 of the present invention, a method comprising: providing a main stent-graft, which is configured to assume a radially-compressed delivery state and a radially-expanded deployment state, and which comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main-stent-graft stent member, and (b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; deploying a primary guidewire into vasculature of a patient between proximal and distal vascular access sites; introducing a main delivery catheter and a fixation tube over the primary guidewire into a main blood vessel via the proximal vascular access site, while: the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that the distal main-fluid-flow guide end opening faces the distal catheter end, a sheath-rail guidewire is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end, a nosecone is removably coupled to the distal catheter end, a fixation tube is disposed at least partially distal to the nosecone, and the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube; transitioning the main stent-graft to the radially-expanded deployment state by deploying the main stent-graft from the main delivery catheter; introducing an introducer sheath into the vasculature over the sheath-rail guidewire via the proximal vascular access site; distally advancing the introducer sheath over the sheath-rail guidewire until a distal end of the introducer sheath (a) is disposed within the main stent-graft within 1 cm of the main-fluid-flow guide lateral opening, or (b) exits the main-fluid-flow guide lateral opening; advancing a distal end portion of a cannulating guidewire through the introducer sheath and into a branch of the main blood vessel; advancing a branching stent-graft over the cannulating guidewire (a) from the proximal vascular access site to within the main stent-graft and (b) out of the main-fluid- flow guide lateral opening; disposing the branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) a branching-stent-graft fluid flow guide of the branching stent-graft and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening; and before or after advancing the branching stent-graft over the cannulating guidewire, withdrawing the introducer sheath from the vasculature via the proximal vascular access site.

[0051] Inventive Concept 18. The method according to Inventive Concept 17, wherein introducing the main delivery catheter and the fixation tube over the primary guidewire comprises introducing the main delivery catheter and the fixation tube over the primary guidewire into the main blood vessel via the proximal vascular access site, while the fixation tube is removably in contact with a distal end portion of the nosecone.

[0052] Inventive Concept 19. The method according to Inventive Concept 17, wherein advancing the distal end portion of the cannulating guidewire through the introducer sheath and into the branch of the main blood vessel comprises: introducing a cannulating catheter into a proximal end of the introducer sheath and advancing the cannulating catheter through the introducer sheath alongside the sheath-rail guidewire, and out of a distal end of the introducer sheath, while the cannulating guidewire is disposed at least partially within the cannulating catheter; advancing the distal end portion of the cannulating guidewire into the branch of the main blood vessel; and withdrawing the cannulating catheter from the introducer sheath, while leaving the distal end portion of the cannulating guidewire in the branch of the main blood vessel.

[0053] Inventive Concept 20. The method according to Inventive Concept 17, wherein introducing the main delivery catheter comprises introducing the main delivery catheter while the fixation tube is removably coupled to a distal end portion of the main stent-graft.

[0054] Inventive Concept 21. The method according to Inventive Concept 17, wherein introducing the main delivery catheter comprises introducing the main delivery catheter while the fixation tube is removably in contact with a distal end portion of the nosecone.

[0055] Inventive Concept 22. The method according to Inventive Concept 17, wherein introducing the main delivery catheter and the fixation tube over the primary guidewire comprises distally advancing the main delivery catheter, the nosecone, and the fixation tube over the primary guidewire until the coupling site exits the distal vascular access site, and wherein the method further comprises withdrawing the sheath-rail guidewire from the vasculature. Inventive Concept 23. The method according to Inventive Concept 22, wherein withdrawing the sheath-rail guidewire from the vasculature comprises: decoupling the sheath-rail guidewire from the fixation tube; and proximally withdrawing the sheath-rail guidewire from the vasculature via the proximal vascular access site.

[0056] Inventive Concept 24. The method according to Inventive Concept 23, further comprising axially moving the fixation tube away from the nosecone.

[0057] Inventive Concept 25. The method according to Inventive Concept 17, wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0058] Inventive Concept 26. The method according to Inventive Concept 17, wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0059] Inventive Concept 27. The method according to Inventive Concept 17, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, wherein the at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening is at least a first portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, wherein the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein main fluid flow guide of the main stent-graft is shaped so as to further define a second main-fluid-flow guide lateral opening, and wherein introducing the main delivery catheter and the fixation tube over the primary guidewire comprises introducing the main delivery catheter and the fixation tube over the primary guidewire into the main blood vessel via the proximal access site, while: an elongate member is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end. Inventive Concept 28. The method according to Inventive Concept 27, wherein the branching stent-graft is a first branching stent-graft, and the branchingstent-graft fluid flow guide is a first branching-stent-graft fluid flow guide, and wherein the elongate member is a secondary guidewire tube, and wherein the method further comprises:

[0060] (i) before introducing the main stent-graft into the vasculature: inserting a secondary guidewire through a secondary-guidewire-tube lumen of the secondary guidewire tube; removing the secondary guidewire tube; and deploying the secondary guidewire between two vascular access sites; and

[0061] (ii) after transitioning the main stent-graft to the radially-expanded deployment state: advancing a second branching stent-graft over the secondary guidewire (a) to within the main stent-graft and (b) out of the second main-fluid-flow guide lateral opening; disposing the second branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) the second branching-stent-graft fluid flow guide and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the second main-fluid-flow guide lateral opening; and withdrawing the secondary guidewire from the vasculature.

[0062] Inventive Concept 29. The method according to Inventive Concept 27, wherein the branching stent-graft is a first branching stent-graft, and the branching- stent-graft fluid flow guide is a first branching-stent-graft fluid flow guide, and wherein the elongate member is a secondary guidewire, and wherein the method further comprises:

[0063] (i) before introducing the main stent-graft into the vasculature, deploying the secondary guidewire between two vascular access sites; and

[0064] (ii) after transitioning the main stent-graft to the radially-expanded deployment state: advancing a second branching stent-graft over the secondary guidewire (a) to within the main stent-graft and (b) out of the second main-fluid-flow guide lateral opening; disposing the second branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) the second branching-stent-graft fluid flow guide and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the second main-fluid-flow guide lateral opening; and withdrawing the secondary guidewire from the vasculature.

[0065] There is still further provided, in accordance with an Inventive Concept 30 of the present invention, a stent-graft system for use with a primary guidewire, the stent-graft system comprising:

[0066] (i) a main stent- graft, which (1) is configured to be deployed over the primary guidewire, (2) is configured to assume a radially-compressed delivery state and a radially- expanded deployment state, and (3) comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main- stent- graft stent member, and (b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; and

[0067] (ii) a delivery system, which comprises:

[0068] (A) a main delivery catheter having proximal and distal catheter ends, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that (a) the distal main-fluid-flow guide end opening faces the distal catheter end, and (b) the main-fluid-flow guide lateral opening is at a first angular location with respect to a central longitudinal axis of the main delivery catheter; and

[0069] (B) an elongate member, which is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening, at the first angular location, to outside the main fluid flow lumen, and (e) the distal catheter end, wherein the elongate member exits the distal catheter end at a second angular location with respect to the central longitudinal axis of the main delivery catheter, the second angular location offset from the first angular location around the central longitudinal axis by at least 90 degrees.

[0070] Inventive Concept 31. The stent-graft system according to Inventive Concept 30, wherein the second angular location is offset from the first angular location around the central longitudinal axis by at least 135 degrees.

[0071] Inventive Concept 32. The stent-graft system according to Inventive Concept 30, wherein the main delivery catheter is shaped so as to define a distal curved portion that causes the main delivery catheter to automatically rotationally orient itself.

[0072] Inventive Concept 33. The stent-graft system according to Inventive Concept 30, further comprising a nosecone removably coupled to the distal catheter end.

[0073] Inventive Concept 34. The stent-graft system according to Inventive Concept 30, wherein the elongate member wraps around the main stent-graft from the first angular location to the second angular location in a single direction around the main stent-graft.

[0074] Inventive Concept 35. The stent-graft system according to Inventive Concept 30, wherein the elongate member wraps around the main stent-graft from the first angular location to the second angular location in less than one turn around the main stent-graft.

[0075] Inventive Concept 36. The stent-graft system according to Inventive Concept 30, wherein the elongate member is removably positioned passing sequentially through (a) the proximal catheter end, (b) the at least a longitudinal portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (c) the proximal main-fluid-flow guide end opening, (d) the longitudinal portion of the main fluid flow lumen, (e) the main-fluid- flow guide lateral opening to outside the main fluid flow lumen, and (f) the distal catheter end.

[0076] Inventive Concept 37. The stent-graft system according to any one of Inventive Concepts 30-36, for use with a secondary guidewire, wherein the elongate member comprises a secondary guidewire tube, which is shaped so as to define a secondary-guidewire-tube lumen for insertion therethrough of the secondary guidewire.

[0077] Inventive Concept 38. The stent-graft system according to any one of Inventive Concepts 30-36, wherein the elongate member comprises a secondary guidewire.

[0078] Inventive Concept 39. The stent-graft system according to any one of Inventive Concepts 30-36, wherein the delivery system further comprises a main inner shaft, which is removably disposed at least partially within the main delivery catheter, and is shaped so as to define a guidewire longitudinal lumen for insertion therethrough of the primary guide wire.

[0079] Inventive Concept 40. The stent-graft system according to any one of Inventive Concepts 30-36, wherein the main stent-graft further comprises an internal support channel, which (a) is configured to assume expanded and collapsed states, (b) is disposed within the main fluid flow guide, and (c) comprises a generally tubular channel fluid flow guide, which is shaped so as to define (1) proximal and distal channel-fluid-flow end openings and (2) when the internal support channel is in the expanded state, a channel lumen between the proximal and the distal channel-fluid-flow end openings, wherein:

[0080] (A) when the internal support channel is in the collapsed state, the distal channel-fluid-flow guide end opening faces radially inward, and

[0081] (B) when the internal support channel is in the expanded state and the main stent-graft is in the radially-expanded deployment state, the distal channelfluid-flow guide end opening faces at least partially distally within the main fluid flow guide, wherein the proximal channel-fluid-flow end opening is sealingly coupled to a perimeter of the main-fluid-flow guide lateral opening, such that the channel lumen is in fluid communication with outside the main fluid flow guide via the main-fluid-flow guide lateral opening when the internal support channel is in the expanded state, wherein the elongate member is removably positioned passing sequentially through (a) the at least a portion of the main delivery catheter proximal to the proximal main-fluid- flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) the longitudinal portion of the main fluid flow lumen, (d) the distal channel-fluid-flow guide end opening, (e) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (f) the distal catheter end, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state with the distal main-fluid-flow guide end opening facing the distal catheter end, thereby constraining the internal support channel in the collapsed state, and wherein the internal support channel is configured to automatically transition to the expanded state when not constrained in the collapsed state by the main stent-graft and not constrained in the collapsed state by the elongate member.

[0082] Inventive Concept 41. The stent-graft system according to Inventive Concept 40, wherein the internal support channel further comprises a flexible channel stent member to which the channel fluid flow guide is securely attached.

[0083] Inventive Concept 42. The stent-graft system according to any one of Inventive Concepts 30-36, wherein the stent-graft system further comprises a branching stent-graft, which comprises a flexible branching -stent-graft stent member and a generally tubular branching- stent-graft fluid flow guide, and wherein the branching stent-graft is configured to be disposed through the main- fluid-flow guide lateral opening so as to form a blood-tight seal between the branching- stent- graft fluid flow guide and a portion of the main- stent- graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

[0084] Inventive Concept 43. The stent-graft system according to any one of Inventive Concepts 30-36, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, wherein the at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening is at least a first portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, wherein the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein main fluid flow guide of the main stent-graft is shaped so as to further define a second main-fluid-flow guide lateral opening, and wherein the delivery system further comprises a sheath-rail guidewire, which is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end. Inventive Concept 44. The stent-graft system according to Inventive Concept 43, wherein the delivery system further comprises: a nosecone removably coupled to the distal catheter end; and a fixation tube, disposed at least partially distal to the nosecone, wherein the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube.

[0085] Inventive Concept 45. The stent-graft system according to Inventive Concept 44, wherein the fixation tube is removably coupled to a distal end portion of the main stent-graft.

[0086] Inventive Concept 46. The stent-graft system according to Inventive Concept 44, wherein the fixation tube is axially moveable away from the nosecone.

[0087] Inventive Concept 47. The stent-graft system according to Inventive Concept 44, for use with a primary guidewire, wherein the fixation tube is shaped so as to define a lumen for insertion therethrough of the primary guidewire.

[0088] Inventive Concept 48. The stent-graft system according to Inventive Concept 44, wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0089] Inventive Concept 49. The stent-graft system according to Inventive Concept 44, wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0090] Inventive Concept 50. The stent-graft system according to Inventive Concept 44, wherein the delivery system further comprises an introducer sheath, which is configured to be introduced into vasculature of a patient over the sheath-rail guidewire.

[0091] Inventive Concept 51. The stent-graft system according to Inventive Concept 50, wherein the delivery system further comprises a cannulating guidewire.

[0092] Inventive Concept 52. The stent-graft system according to Inventive Concept 51, wherein the delivery system further comprises a cannulating catheter, which is configured, while the cannulating guidewire is disposed at least partially within the cannulating catheter, to be introduced into a proximal end of the introducer sheath, and advanced through the introducer sheath and out of a distal end of the introducer sheath.

[0093] Inventive Concept 53. The stent-graft system according to Inventive Concept 43, wherein the sheath-rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinal axis of the main delivery catheter, the third angular location offset from the second angular location around the central longitudinal axis by at least 90 degrees.

[0094] Inventive Concept 54. The stent-graft system according to Inventive Concept 53, wherein the third angular location is offset from the second angular location around the central longitudinal axis by at least 135 degrees.

[0095] Inventive Concept 55. The stent-graft system according to Inventive Concept 43, wherein the sheath-rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinal axis of the main delivery catheter, the third angular location either (a) at the first angular location around the central longitudinal axis, or (b) offset from the first angular location around the central longitudinal axis by less than 90 degrees.

[0096] Inventive Concept 56. The stent-graft system according to Inventive Concept 55, wherein the third angular location is offset from the first angular location around the central longitudinal axis by less than 45 degrees.

[0097] Inventive Concept 57. The stent-graft system according to Inventive Concept 43, wherein the stent-graft system further comprises first and second branching stentgrafts, which comprise first and second flexible branching-stent-graft stent members and first and second generally tubular branching-stent-graft fluid flow guides, respectively, wherein the first branching stent-graft is configured to be disposed through the first main-fluid-flow guide lateral opening so as to form a blood-tight seal between the first branching- stent-graft fluid flow guide and a first portion of the main- stent- graft fluid flow guide that defines a first perimeter of the first main-fluid-flow guide lateral opening, and wherein the second branching stent-graft is configured to be disposed through the second main-fluid-flow guide lateral opening so as to form a blood-tight seal between the second branching-stent-graft fluid flow guide and a second portion of the main-stent-graft fluid flow guide that defines a second perimeter of the second main-fluid-flow guide lateral opening.

[0098] There is additionally provided, in accordance with an Inventive Concept 58 of the present invention, a method comprising: providing a main stent-graft, which is configured to assume a radially-compressed delivery state and a radially-expanded deployment state, and which comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main-stent-graft stent member, and (b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; deploying a primary guidewire into vasculature of a patient; introducing, over the primary guidewire, a main delivery catheter, having proximal and distal catheter ends, into the vasculature while: the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that (a) the distal main-fluid-flow guide end opening faces the distal catheter end, and (b) the main-fluid-flow guide lateral opening is at a first angular location with respect to a central longitudinal axis of the main delivery catheter, and an elongate member is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening, at the first angular location, to outside the main fluid flow lumen, and (e) the distal catheter end, and the elongate member exits the distal catheter end at a second angular location with respect to the central longitudinal axis of the main delivery catheter, the second angular location offset from the first angular location around the central longitudinal axis by at least 90 degrees; and thereafter, transitioning the main stent-graft to the radially-expanded deployment state by deploying the main stent-graft from the main delivery catheter.

[0099] Inventive Concept 59. The method according to Inventive Concept 58, wherein the second angular location is offset from the first angular location around the central longitudinal axis by at least 135 degrees.

[0100] Inventive Concept 60. The method according to Inventive Concept 58, wherein the main delivery catheter is shaped so as to define a distal curved portion that causes the main delivery catheter to automatically rotationally orient itself.

[0101] Inventive Concept 61. The method according to Inventive Concept 58, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while a nosecone is removably coupled to the distal catheter end. Inventive Concept 62. The method according to Inventive Concept 58, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the elongate member wraps around the main stent-graft from the first angular location to the second angular location in a single direction around the main stent-graft.

[0102] Inventive Concept 63. The method according to Inventive Concept 58, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the elongate member wraps around the main stent-graft from the first angular location to the second angular location in less than one turn around the main stent-graft.

[0103] Inventive Concept 64. The method according to Inventive Concept 58, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the elongate member is removably positioned passing sequentially through (a) the proximal catheter end, (b) the at least a longitudinal portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (c) the proximal main-fluid-flow guide end opening, (d) the longitudinal portion of the main fluid flow lumen, (e) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (f) the distal catheter end.

[0104] Inventive Concept 65. The method according to Inventive Concept 58, further comprising, before deploying the main stent-graft from the main delivery catheter: disposing the main delivery catheter at least partially in a main blood vessel of the vasculature; and facilitating rotation of the main delivery catheter such that that the main-fluid-flow guide lateral opening is on a side of the main delivery catheter that is oriented toward a branch of the main blood vessel.

[0105] Inventive Concept 66. The method according to Inventive Concept 58, wherein the elongate member is a secondary guidewire tube, and wherein the method further comprises, before introducing the main stent-graft into the vasculature, inserting a secondary guidewire through a secondary-guidewire-tube lumen of the secondary guidewire tube.

[0106] Inventive Concept 67. The method according to Inventive Concept 66, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while a nosecone is removably coupled to the distal catheter end, and wherein the method further comprises, before deploying the main stent-graft from the main delivery catheter: removing the secondary guidewire tube from the main stent-graft and the main delivery catheter; before or after removing the secondary guidewire tube, disposing the main delivery catheter at least partially in a main blood vessel of the vasculature; upon ascertaining that the secondary guidewire crosses the nosecone at least once, rotating the main delivery catheter, until the secondary guidewire exits a side of the nosecone facing toward the second branch; and facilitating rotation of the main delivery catheter such that that the main- fluid-flow guide lateral opening is on a side of the main delivery catheter that is oriented toward a branch of the main blood vessel.

[0107] Inventive Concept 68. The method according to Inventive Concept 66, further comprising, after transitioning the main stent-graft to the radially-expanded deployment state: advancing a branching stent-graft over the secondary guidewire (a) from a vascular access site to within the main stent-graft and (b) out of the main-fluid-flow guide lateral opening; and disposing the branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) a branching-stent-graft fluid flow guide of the branching stent-graft and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

[0108] Inventive Concept 69. The method according to Inventive Concept 58, wherein the elongate member is a secondary guidewire, and wherein the method further comprises, before introducing the main stent-graft into the vasculature, deploying the secondary guidewire between two vascular access sites.

[0109] Inventive Concept 70. The method according to Inventive Concept 69, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while a nosecone is removably coupled to the distal catheter end, and wherein the method further comprises, before deploying the main stent-graft from the main delivery catheter: disposing the main delivery catheter at least partially in a main blood vessel of the vasculature; upon ascertaining that the secondary guidewire crosses the nosecone at least once, rotating the main delivery catheter, until the secondary guidewire exits a side of the nosecone facing toward the second branch; and facilitating rotation of the main delivery catheter such that that the main- fluid-flow guide lateral opening is on a side of the main delivery catheter that is oriented toward a branch of the main blood vessel.

[0110] Inventive Concept 71. The method according to Inventive Concept 69, further comprising, after transitioning the main stent-graft to the radially-expanded deployment state: advancing a branching stent-graft over the secondary guidewire (a) from a first of the vascular access sites to within the main stent-graft and (b) out of the main-fluid-flow guide lateral opening; and disposing the branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) a branching-stent-graft fluid flow guide of the branching stent-graft and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

[0111] Inventive Concept 72. The method according to Inventive Concept 58, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, wherein the at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening is at least a first portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, wherein the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein main fluid flow guide of the main stent-graft is shaped so as to further define a second main-fluid-flow guide lateral opening, and wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while a sheath-rail guidewire is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end.

[0112] Inventive Concept 73. The method according to Inventive Concept 72, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while: a fixation tube is disposed at least partially distal to a nosecone that is removably coupled to the distal catheter end, and the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube.

[0113] Inventive Concept 74. The method according to Inventive Concept 73, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the fixation tube is removably coupled to a distal end portion of the main stent-graft.

[0114] Inventive Concept 75. The method according to Inventive Concept 73, wherein introducing the main delivery catheter into the vasculature comprises: deploying a primary guidewire between two vascular access sites; and introducing the main delivery catheter and the fixation tube into the vasculature over the primary guidewire.

[0115] Inventive Concept 76. The method according to Inventive Concept 73, wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0116] Inventive Concept 77. The method according to Inventive Concept 73, wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

[0117] Inventive Concept 78. The method according to Inventive Concept 72, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the sheath-rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinal axis of the main delivery catheter, the third angular location offset from the second angular location around the central longitudinal axis by at least 90 degrees. Inventive Concept 79. The method according to Inventive Concept 78, wherein the third angular location is offset from the second angular location around the central longitudinal axis by at least 135 degrees.

[0118] Inventive Concept 80. The method according to Inventive Concept 72, wherein introducing the main delivery catheter into the vasculature comprises introducing the main delivery catheter into the vasculature while the sheath-rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinal axis of the main delivery catheter, the third angular location either (a) at the first angular location around the central longitudinal axis, or (b) offset from the first angular location around the central longitudinal axis by less than 90 degrees.

[0119] Inventive Concept 81. The method according to Inventive Concept 67, wherein the third angular location is offset from the first angular location around the central longitudinal axis by less than 45 degrees.

[0120] There is yet additionally provided, in accordance with an Inventive Concept 82 of the present invention, a stent-graft system comprising:

[0121] (i) a stent-graft comprising (a) a fluid flow guide and (b) a stent, which comprises: cylindrical undulating rings, which are coupled to the fluid flow guide at respective axial locations along an axis of the fluid flow guide, so as to provide a tubular shape to the fluid flow guide about the axis when the stent-graft is in a radially-expanded deployment state, and which comprise first and second cylindrical undulating rings; and spring links, which are joined to the first and the second cylindrical undulating rings,

[0122] (ii) a delivery system, which comprises a delivery catheter, wherein the stent-graft is removably disposed within a portion of the delivery catheter such that the delivery catheter constrains the stent-graft in a radially-compressed delivery state in which (a) the spring links are in respective extended tensioned states, and (b) the first and the second cylindrical undulating rings do not axially overlap with each wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings.

[0123] Inventive Concept 83. The stent-graft system according to Inventive Concept 82, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings bunch up a portion of the fluid flow guide axially between first and second axial locations at which the first and the second cylindrical undulating rings are coupled to the fluid flow guide.

[0124] Inventive Concept 84. The stent-graft system according to Inventive Concept 82, wherein the spring links are joined to the first and the second cylindrical undulating rings such that the spring links are oriented axially along the stent-graft.

[0125] Inventive Concept 85. The stent-graft system according to Inventive Concept 82, wherein the spring links have respective first and second ends that are coupled to the first and the second cylindrical undulating rings, respectively.

[0126] Inventive Concept 86. The stent-graft system according to Inventive Concept 82, wherein the spring links are shaped so define respective undulations falling generally in respective planes.

[0127] Inventive Concept 87. The stent-graft system according to Inventive Concept 82, wherein the spring links are helical.

[0128] Inventive Concept 88. The stent-graft system according to Inventive Concept 82, wherein the stent comprises at least three of the cylindrical undulating rings in addition to the first and the second cylindrical undulating rings.

[0129] Inventive Concept 89. The stent-graft system according to Inventive Concept 88, wherein the first cylindrical undulating ring is located closer to an end of the fluid flow guide than are any of the other cylindrical undulating rings.

[0130] Inventive Concept 90. The stent-graft system according to Inventive Concept 82, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 30% - 70% of the extended axial offset.

[0131] Inventive Concept 91. The stent-graft system according to Inventive Concept 82, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 4.5 - 10.5 mm less than the extended axial offset.

[0132] Inventive Concept 92. The stent-graft system according to Inventive Concept 82, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 40% - 80% of an average height of undulations of the first and the second cylindrical undulating rings, measured along the axis when the stent-graft is in the radially- expanded deployment state.

[0133] Inventive Concept 93. The stent-graft system according to Inventive Concept 82, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 5% - 35% of an average diameter of the first and the second cylindrical undulating rings when the stent-graft is unconstrained in the radially-expanded deployment state.

[0134] Inventive Concept 94. The stent-graft system according to Inventive Concept 82, wherein the stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent-graft in the radially-compressed delivery state in which friction between the first and the second cylindrical undulating rings and an inner wall of the delivery catheter helps hold the spring links in the respective extended tensioned states.

[0135] Inventive Concept 95. The stent-graft system according to Inventive Concept 82, wherein the stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent-graft in the radially-compressed delivery state in which the fluid flow guide helps hold the spring links in the respective extended tensioned states.

[0136] Inventive Concept 96. The stent-graft system according to any one of Inventive Concepts 82-95, wherein, when the stent- graft is removably disposed within the portion of the delivery catheter in the radially-compressed delivery state, the first and the second cylindrical undulating rings are disposed along the stent-graft so as to define an axial gap between the first and the second cylindrical undulating rings. Inventive Concept 97. The stent-graft system according to Inventive Concept 96, wherein the axial gap has a length of 0.1 - 5 mm, measured parallel to the axis.

[0137] Inventive Concept 98. The stent-graft system according to any one of Inventive Concepts 82-95, wherein the stent- graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings:

[0138] (a) axially overlap with each other,

[0139] (b) axially border each other, or

[0140] (c) define an axial gap between each other, the axial gap having a length less than 50% of an average height of undulations of the first and the second cylindrical undulating rings, the length and the average height measured parallel to the axis when the stent-graft is in the radially-expanded deployment state.

[0141] Inventive Concept 99. The stent-graft system according to Inventive Concept 98, wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings define the axial gap between each other.

[0142] Inventive Concept 100. The stent-graft system according to Inventive Concept 98, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap with each other.

[0143] Inventive Concept 101. The stent-graft system according to Inventive Concept 100, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap each other by an overlap length measured parallel to the axis, and wherein the overlap length equals 5% - 80% of the average height of the undulations of the first and the second cylindrical undulating rings. Inventive Concept 102. The stent-graft system according to Inventive Concept 101, wherein the overlap length equals 15% - 50% of the average height of the undulations of the first and the second cylindrical undulating rings.

[0144] There is also provided, in accordance with an Inventive Concept 103 of the present invention, a method comprising: introducing a delivery catheter of a delivery system into a blood vessel of patient and advancing the delivery catheter to a target location in the blood vessel while a stentgraft is removably disposed within a portion of the delivery catheter such that the delivery catheter constrains the stent-graft in a radially-compressed delivery state in which (a) spring links of a stent of the stent-graft are in respective extended tensioned states, and (b) first and second ones of cylindrical undulating rings of the stent do not axially overlap with each other, wherein the spring links are joined to the first and the second cylindrical undulating rings; and transitioning the stent-graft to a radially-expanded deployment state by deploying the stent-graft from the delivery catheter, such that the cylindrical undulating rings, which are coupled to a fluid flow guide of the stent-graft at respective axial locations along an axis of the fluid flow guide, provide a tubular shape to the fluid flow guide about the axis, wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter upon the deploying the stent-graft from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings.

[0145] Inventive Concept 104. The method according to Inventive Concept 103, wherein the stentgraft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings bunch up a portion of the fluid flow guide axially between first and second axial locations at which the first and the second cylindrical undulating rings are coupled to the fluid flow guide.

[0146] Inventive Concept 105. The method according to Inventive Concept 103, wherein the spring links are joined to the first and the second cylindrical undulating rings such that the spring links are oriented axially along the stent-graft. Inventive Concept 106. The method according to Inventive Concept 103, wherein the spring links have respective first and second ends that are coupled to the first and the second cylindrical undulating rings, respectively.

[0147] Inventive Concept 107. The method according to Inventive Concept 103, wherein the spring links are shaped so define respective undulations falling generally in respective planes.

[0148] Inventive Concept 108. The method according to Inventive Concept 103, wherein the spring links are helical.

[0149] Inventive Concept 109. The method according to Inventive Concept 103, wherein the stent includes at least three of the cylindrical undulating rings in addition to the first and the second cylindrical undulating rings.

[0150] Inventive Concept 110. The method according to Inventive Concept 109, wherein the first cylindrical undulating ring is located closer to an end of the fluid flow guide than are any of the other cylindrical undulating rings.

[0151] Inventive Concept 111. The method according to Inventive Concept 103, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 30% - 70% of the extended axial offset.

[0152] Inventive Concept 112. The method according to Inventive Concept 103, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 4.5 - 10.5 mm less than the extended axial offset.

[0153] Inventive Concept 113. The method according to Inventive Concept 103, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 40% - 80% of an average height of undulations of the first and the second cylindrical undulating rings, measured along the axis when the stent-graft is in the radially- expanded deployment state.

[0154] Inventive Concept 114. The method according to Inventive Concept 103, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 5% - 35% of an average diameter of the first and the second cylindrical undulating rings when the stent-graft is unconstrained in the radially-expanded deployment state. Inventive Concept 115. The method according to Inventive Concept 103, wherein introducing the delivery catheter comprises introducing the delivery catheter into the blood vessel and advancing the delivery catheter to the target location in the blood vessel while a stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent-graft in the radially-compressed delivery state in which friction between the first and the second cylindrical undulating rings and an inner wall of the delivery catheter helps hold the spring links in the respective extended tensioned states.

[0155] Inventive Concept 116. The method according to Inventive Concept 103, wherein introducing the delivery catheter comprises introducing the delivery catheter into the blood vessel and advancing the delivery catheter to the target location in the blood vessel while a stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent-graft in the radially-compressed delivery state in which the fluid flow guide helps hold the spring links in the respective extended tensioned states.

[0156] Inventive Concept 117. The method according to Inventive Concept 103, wherein, when the stent-graft is removably disposed within the portion of the delivery catheter in the radially-compressed delivery state, the first and the second cylindrical undulating rings are disposed along the stent-graft so as to define an axial gap between the first and the second cylindrical undulating rings.

[0157] Inventive Concept 118. The method according to Inventive Concept 117, wherein the axial gap has a length of 0.1 - 5 mm, measured parallel to the axis.

[0158] Inventive Concept 119. The method according to Inventive Concept 103, wherein the stentgraft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings:

[0159] (a) axially overlap with each other,

[0160] (b) axially border each other, or

[0161] (c) define an axial gap between each other, the axial gap having a length less than 50% of an average height of undulations of the first and the second cylindrical undulating rings, the length and the average height measured parallel to the axis when the stent-graft is in the radially-expanded deployment state.

[0162] Inventive Concept 120. The method according to Inventive Concept 119, wherein the stentgraft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings define the axial gap between each other.

[0163] Inventive Concept 121. The method according to Inventive Concept 119, wherein the stentgraft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap with each other.

[0164] Inventive Concept 122. The method according to Inventive Concept 121, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap each other by an overlap length measured parallel to the axis, and wherein the overlap length equals 5% - 80% of the average height of the undulations of the first and the second cylindrical undulating rings.

[0165] Inventive Concept 123. The method according to Inventive Concept 122, wherein the overlap length equals 15% - 50% of the average height of the undulations of the first and the second cylindrical undulating rings.

[0166] The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

[0167] BRIEF DESCRIPTION OF THE DRAWINGS

[0168] Figs. 1A-B are schematic illustrations of a vascular implant assembly in disassembled and assembled states, respectively, in accordance with an application of the present invention;

[0169] Figs. 1C-D are schematic illustrations of another configuration of the vascular implant assembly of Figs. 1A-B in disassembled and assembled states, respectively, in accordance with an application of the present invention;

[0170] Figs. 2A-0 are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0171] Fig. 3 is a schematic illustration of an alternative implantation of the vascular implant assembly of Figs. 1A-B in vasculature, in accordance with an application of the present invention;

[0172] Figs. 4A-C are side-view schematic illustrations of an internal support channel of a main stent-graft of the vascular implant assembly of Figs. 1A-B in an expanded state, a partially-collapsed state, and a collapsed state, respectively, in accordance with an application of the present invention;

[0173] Figs. 4D-F are side-view schematic illustrations of the internal support channel of the main stent-graft of the vascular implant assembly of Figs. 1 A-B in the expanded state, the partially-collapsed state, and the collapsed state, respectively, in accordance with another application of the present invention;

[0174] Fig. 5 is a schematic illustration of a flexible channel stent member of the internal support channel of Figs. 4A-C in an expanded state, from a partially distal and partially side view, in accordance with an application of the present invention;

[0175] Figs. 6A-C are schematic illustrations of several stages of a portion of a method for deploying a main stent-graft and a branching stent-graft, in accordance with an application of the present invention;

[0176] Fig. 7 is a schematic illustration of a configuration of a main stent-graft of the vascular implant assembly of Figs. 1A-B disposed in a radially-compressed delivery state within a portion of a main delivery catheter, in accordance with an application of the present invention;

[0177] Figs. 8A-D are schematic illustrations of several stages of an improperly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0178] Figs. 9A-C are schematic illustrations of several stages of a properly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0179] Figs. 10A and 10B are schematic illustrations of another configuration of a main stent-graft disposed in a radially-compressed delivery state within a portion of a main delivery catheter, in accordance with an application of the present invention;

[0180] Figs. 11A-D are schematic illustrations of several stages of an improperly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0181] Figs. 12A-C are schematic illustrations of several stages of a properly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0182] Figs. 13A-B are schematic illustrations of another vascular implant assembly in disassembled and assembled states, respectively, in accordance with an application of the present invention;

[0183] Fig. 14 is a schematic illustration of an alternative configuration of a main stentgraft of the vascular implant assembly of Figs. 13A-B, in accordance with an application of the present invention;

[0184] Figs. 15A and 15B are schematic illustrations of a configuration of a main stentgraft of the vascular implant assembly of Figs. 13A-B disposed in a radially-compressed delivery state within a portion of a main delivery catheter, in accordance with an application of the present invention;

[0185] Fig. 16 is a schematic illustration of a control handle of a delivery system, in accordance with an application of the present invention;

[0186] Fig. 17 is a schematic illustration of a portion of the delivery system of Fig. 16, in accordance with an application of the present invention;

[0187] Figs. 18A-Q are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention;

[0188] Figs. 19A and 19B are schematic illustrations of yet another configuration of a main stent-graft disposed in a radially-compressed delivery state within a portion of a main delivery catheter, in accordance with an application of the present invention;

[0189] Figs. 20A-H are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention; and Figs. 21A-B are schematic illustrations of a portion of a stent-graft system comprising a stent- graft, shown in a radially-compressed delivery state and in a partially radially-expanded deployment state, respectively, in accordance with an application of the present invention.

[0190] DETAILED DESCRIPTION OF APPLICATIONS

[0191] Figs. 1A-B are schematic illustrations of a vascular implant assembly 20 in disassembled and assembled states, respectively, in accordance with an application of the present invention. Vascular implant assembly 20 typically comprises a main stent-graft 22 and a branching stent-graft 24. Both main stent-graft 22 and branching stent-graft 24 are shown in radially-expanded deployment states in Figs. 1A-B.

[0192] Figs. 1C-D are schematic illustrations of another configuration of vascular implant assembly in disassembled and assembled states, respectively, in accordance with an application of the present invention. Both main stent-graft 22 and branching stent-graft 24 are shown in radially-expanded deployment states in Figs. 1C-D. The difference between the configurations of Figs. 1 A-B and 1C-D is described hereinbelow with reference to Figs. 1C-D.

[0193] Main stent-graft 22 typically comprises a flexible main-stent-graft stent member 26 and a generally tubular fluid flow guide 28. Generally tubular fluid flow guide 28 is securely attached to main-stent-graft stent member 26, such as by suturing or stitching, so as to cover at least a portion of main- stent- graft stent member 26. The stent member may be attached to an internal surface and / or an external surface of the fluid flow guide. Optionally, a portion of the stent struts of the stent member may be attached (e.g., sutured) to the internal surface, and another portion to the external surface. Main- stent-graft fluid flow guide 28 is shaped so as to define proximal and distal main-fluid-flow guide end openings 27A and 27B, a main fluid flow lumen 29 therebetween, and a main-fluid-flow guide lateral opening 30.

[0194] For some applications, main-stent-graft fluid flow guide 28 has one or more of the following dimensions when unconstrained (by a deployment catheter, by anatomy, or otherwise) in the radially-expanded deployment state:

[0195] • a length of at least 15 cm, no more than 30 cm, and / or 15 -30 cm,

[0196] • a greatest diameter of at least 1 cm, no more than 5 cm, and / or 1 - 5 cm, • an area of lateral opening 30 of at least 0.5 cm2, no more than 2.1 cm2, and / or 0.5 - 2.1 cm2,

[0197] • a perimeter of lateral opening 30 of at least 2 cm, no more than 6.5 cm, and / or 2 - 6.5 cm,

[0198] • a perimeter of proximal main-fluid-flow guide end opening 27 A of at least 10 cm, no more than 15 cm, and / or 10 - 15 cm, and / or

[0199] • a perimeter of distal main-fluid-flow guide end opening 27B of at least 1.6 cm, no more than 4.5 cm, and / or 1.6 - 4.5cm.

[0200] Branching stent-graft 24 typically comprises a flexible branching- stent-graft stent member 32 and a generally tubular branching-stent-graft fluid flow guide 34. Branchingstent-graft fluid flow guide 34 is securely attached to branching- stent-graft stent member 32, such as by suturing or stitching, so as to cover at least a portion of branching-stent-graft stent member 32. The stent member may be attached to an internal surface and / or an external surface of the fluid flow guide. Optionally, a portion of the stent struts of the stent member may be attached (e.g., sutured) to the internal surface, and another portion to the external surface. Further optionally, branching- stent-graft fluid flow guide 34 comprises two layers of graft bonded together, between which branching- stent-graft stent member 32 is sandwiched, thereby encapsulating branching-stent-graft stent member 32 in graft material of branching- stent-graft fluid flow guide 34. Branching stent-graft 24 is configured to be disposed through main-fluid-flow guide lateral opening 30 so as to form a blood-tight seal between branching- stent- graft fluid flow guide 34 and:

[0201] • the portion of main- stent-graft fluid flow guide 28 that defines the perimeter of main-fluid-flow guide lateral opening 30, such as shown in Fig. IB, and / or

[0202] • an internal surface of tubular channel fluid flow guide 128 of internal support channel 120, in applications in which main stent-graft 22 comprises internal support channel 120, such as shown in Fig. IB, and such as described in detail hereinbelow with reference to Figs. 4A-C, 4D-F, 5, 6A-C, and 7.

[0203] For some applications, main stent-graft 22 is configured to be positioned partially in a descending aorta 66, partially in an aortic arch 62, and partially in a first branch 60 of aortic arch 62. For example, first branch 60 may be a brachiocephalic artery (BCT) 64. As used in the present application, including the claims and Inventive Concepts, a "branch" of the aortic arch means an artery that branches from the aortic arch, i.e., BCT 64, a left common carotid artery (LCCA) 72, or a left subclavian artery (LSA) 74. As used in the present application, including the claims and Inventive Concepts, a "branch" of the aortic arch does not mean the ostium of the branch (i.e., the opening of the branch off of the aortic arch). Thus, "downstream" of a "branch" of the aortic arch means downstream along the branching artery, rather than downstream along the continuation of the aorta.

[0204] For some applications, branching stent-graft 24 is configured to be positioned partially in a second branch 70 of aortic arch 62 and partially within main stent-graft 22 within aortic arch 62. For example, second branch 70 may be LCCA 72 (as shown in Figs. 2B-O, described hereinbelow) or LSA 74 (as shown in Fig. 3, described hereinbelow).

[0205] For some applications, vascular implant assembly 20 further comprises a branching extension stent-graft 36. Branching extension stent-graft 36 is shown in a radially- expanded deployment state in Figs. 1A-B and 1C-D. Branching extension stent-graft 36 typically comprises a branching-extension-stent-graft stent member 40 and a generally tubular branching-extension-stent-graft fluid flow guide 38. Branching-extension-stent- graft fluid flow guide 38 is securely attached to branching-extension-stent- graft stent member 40 so as to cover at least a portion of branching-extension-stent-graft stent member 40. For these applications, main-stent-graft fluid flow guide 28 is shaped so as to define an extension lateral opening 42, and branching extension stent-graft 36 is configured to be disposed through extension lateral opening 42 so as to form a blood-tight seal between main-stent-graft fluid flow guide 28 and branching-extension-stent-graft fluid flow guide 38, such as shown in Figs. IB and ID. Optionally, main-stent-graft fluid flow guide 28 may implement any of the features of the lateral tube described in US Patent 10,485,684 to Marmur et al., which is incorporated herein by reference.

[0206] Typically, the flexible stent members described herein are self-expandable (and are biased toward a radially-expanded deployment state), though they may alternatively be balloon-expandable. Typically, each of the flexible stent members comprises one or more stent struts that may or may not be interconnected, and may or may not be arranged as rings that are optionally axially separate from one another. In configurations in which the stent struts are not interconnected, they are held together by the generally tubular fluid flow guide. For example, the flexible stent members may comprise a metal, such as a superelastic metal alloy, a shape memory metallic alloy, and / or Nitinol; alternatively, the metal may comprise stainless steel. Each of the generally tubular fluid flow guides may comprise at least one piece of biologically-compatible substantially blood-impervious fabric. The fabric may comprise, for example, a polyester, a polyethylene (e.g., a poly-ethylene-terephthalate), a polymeric film material (e.g., polytetrafluoroethylene (PTFE), polypropylene, polyethylene, high- density polyethylene, polyurethane, polyolefins, ePTFE), a polymeric textile material (e.g., woven polyethylene terephthalate (PET)), natural tissue graft (e.g., saphenous vein or collagen), or a combination thereof.

[0207] Reference is now made to Figs. 2A-O, which are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention. For some applications, the method is used to treat an aortic arch 62 that suffers from acute aortic syndrome, such an aneurysm, a dissection, a penetrating aortic ulcer (PAU), and / or an intramural hematoma (IMH). Although the method is illustrated as comprising deploying main stent-graft 22 and branching stent-graft 24 of the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1A-B, the method may alternatively be used for deploying the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D, or for deploying one or more other vascular implants, such as one or more uncovered stents, one or more balloon catheters, or one or more stent-grafts other than those of vascular implant assembly 20. The method may include all or only a subset of the steps described hereinbelow, and / or additional steps, including but not limited to those described hereinbelow.

[0208] As shown in Fig. 2A, a primary guidewire 50A is deployed endovascularly (typically percutaneously) between a first vascular access site 52A and a third vascular access site 52C of vasculature 54 of a patient, such that (a) a first end portion 56A of primary guidewire 50A passes out of vasculature 54 at first vascular access site 52A, and (b) a second end portion 58A of primary guidewire 50A, opposite first end portion 56A of primary guidewire 50A, passes out of vasculature 54 at third vascular access site 52C. (First vascular access site 52A may be considered a distal vascular access site, and third vascular access site 52C may be considered a proximal vascular access site, in the sense that main delivery catheter 80A is later introduced via the proximal vascular access site, as described hereinbelow with reference to Fig. 2C.) Primary guidewire 50A may be deployed using techniques known in the art for deploying through-and-through guidewires. Primary guidewire 50A may be introduced into and advanced within the vasculature in either direction (i.e., from third vascular access site 52C to first vascular access site 52A or vice versa).

[0209] Typically, first vascular access site 52A is downstream of first branch 60 of aortic arch 62. For example, first vascular access site 52A may be on a right axillary artery (RAA) in applications in which first branch 60 is BCT 64, such as shown.

[0210] Typically, third vascular access site 52C is downstream of descending aorta 66. For example, third vascular access site 52C may be on a right femoral artery, as illustrated, or a right iliac artery (approach not shown).

[0211] As shown in Fig. 2B, a secondary guidewire 50B is deployed between a second vascular access site 52B and third vascular access site 52C, such that (a) a first end portion 56B of secondary guidewire 50B passes out of vasculature 54 at second vascular access site 52B, and (b) a second end portion 58B of secondary guidewire 50B, opposite first end portion 56B of secondary guidewire 50B, passes out of vasculature 54 at third vascular access site 52C. (First vascular access site 52A may be considered a first distal vascular access site, and second vascular access site 52B may be considered a second distal vascular access site.) Secondary guidewire 50B may be deployed using techniques known in the art for deploying through- and- through guidewires. Secondary guidewire 50B may be introduced into and advanced within the vasculature in either direction (i.e., from third vascular access site 52C to second vascular access site 52B to or vice versa).

[0212] Typically, second vascular access site 52B is downstream of second branch 70 of aortic arch 62. For example, second vascular access site 52B may be directly on LCCA 72 in applications in which second branch 70 is LCCA 72, or on LSA 74 or one of its downstream branches (e.g., the left axillary or the left brachial) in applications in which second branch 70 is LSA 74 (such as shown in Fig. 3, described hereinbelow).

[0213] For example, secondary guidewire 50B may be introduced through a through-and- through catheter deployed between second vascular access site 52B (e.g., LCCA 72 or LSA 74) and third vascular access site 52C (for example, such as described hereinbelow with reference to Fig. 18B, mutatis mutandis). Alternatively, secondary guidewire 50B may be introduced using an introducer or access sheath (with or without a catheter) via either second vascular access site 52B or third vascular access site 52C, and then snared to bring the end portion of the secondary guidewire 50B to its target location in vasculature 54. For some applications, the steps of the method described hereinbelow with reference to Figs. 6A-C are performed (a) after deploying primary guidewire 50A and secondary guidewire 50B, such as described hereinabove with reference to Figs. 2A and 2B, respectively, and (b) before deploying main stent-graft 22 over primary guidewire 50A, such as described hereinbelow with reference to Figs. 2C-E.

[0214] As shown in Figs. 2C-E, main stent-graft 22 is deployed over primary guidewire 50A at least partially in aortic arch 62, such that main-fluid-flow guide lateral opening 30 is oriented toward second branch 70 (as can better be seen Figs. 2D-E).

[0215] For some applications, a stent-graft system 44 (labeled in Fig. 6A) is provided that comprises vascular implant assembly 20 and a delivery system 46 (labeled in Fig. 6A), which comprises a main delivery catheter 80A and a main inner shaft 78. Main inner shaft 78 is removably disposed at least partially within main delivery catheter 80A and, optionally, partially within a nosecone 86 of delivery system 46, and is shaped so as to define a guidewire longitudinal lumen 79 through which primary guidewire 50A can be inserted and pass (shown in Figs. 6A-C and 7, described hereinbelow). Typically, delivery system 46 further comprises nosecone 86, as is known in the catheter art, which is typically coupled to a distal end of main inner shaft 78 (for example, main inner shaft 78 may be partially disposed within nosecone 86, as shown). For some applications, proper rotational alignment and / or axial orientation of main-fluid-flow guide lateral opening 30 is achieved using fluoroscopy. For example, main stent-graft 22 may comprise one or more radiopaque markers in a vicinity (e.g., on a periphery of) main-fluid-flow guide lateral opening 30.

[0216] Typically, main stent- graft 22 is deployed by:

[0217] • introducing main delivery catheter 80A into vasculature 54 through third vascular access site 52C and advancing main delivery catheter 80A over primary guidewire 50A and secondary guidewire 50B while main stent-graft 22 is disposed within a portion of main delivery catheter 80A, constrained in a radially-compressed delivery state by main delivery catheter 80A (typically disposed radially between main delivery catheter 80A and main inner shaft 78 (labeled in Figs. 2D, 6A-C, and 7), extending proximally from distal catheter end 82), as shown in Fig. 2C, and

[0218] • releasing main stent-graft 22 from the portion of main delivery catheter 80A, such that main stent-graft 22 transitions to a radially-expanded deployment state at least partially in aortic arch 62, such as shown in Figs. 2D-E; main stent-graft 22 is typically released from main delivery catheter 80A by proximally withdrawing the main delivery catheter, as shown in Fig. 2D.

[0219] In configurations in which secondary guidewire 50B is removably pre-positioned passing sequentially inter alia through proximal catheter end 83 and out of distal catheter end 82, such as shown in Figs. 4D-F and 7, during the advancing of main delivery catheter 80A over primary guidewire 50A and secondary guidewire 50B, main stent- graft 22 may slide distally over secondary guidewire 50B. Alternatively or additionally, main stent-graft 22 may remain axially stationary with respect to secondary guidewire 50B, in which case secondary guidewire 50B may move with delivery system 46 and may move distally out of a secondary access sheath at second vascular access site 52B (the secondary access sheath is used to introduce secondary guidewire 50B into the vasculature, as known in the guide wire art).

[0220] Fig. 2D shows main stent-graft 22 partially released from the main delivery catheter, while Fig. 2E shows the main stent-graft fully released from the main delivery catheter.

[0221] For some applications, such as shown in Figs. 2C-E, a distal-most portion of main stent-graft 22 is deployed in first branch 60 of aortic arch 62. For example, first branch 60 may be BCT 64, such as shown. Alternatively, a distal-most portion of main stent-graft 22 is deployed in aortic arch 62 (configuration not shown).

[0222] Typically, as main delivery catheter 80A is advanced over primary guidewire 50A and secondary guidewire 50B, as shown in Fig. 2C, both primary guidewire 50A and secondary guidewire 50B pass through a distal catheter end 82 of main delivery catheter 80A. Typically, secondary guidewire 50B passes:

[0223] • from distal catheter end 82 of main delivery catheter 80A,

[0224] • to within a distal portion of main delivery catheter 80A outside main stent-graft 22,

[0225] • through main-fluid-flow guide lateral opening 30,

[0226] • to within main stent-graft 22, and

[0227] • out of proximal main- fluid-flow guide end opening 27 A within main delivery catheter 80A, for example as described in detail hereinbelow with reference to Figs. 4A-C, 6A-C, and 7. Typically, primary guidewire 50A and secondary guidewire 50B additionally pass through main delivery catheter 80A until outside of the body of the patient (not shown).

[0228] As described above, in some configurations main- stent- graft fluid flow guide 28 is shaped so as to define extension lateral opening 42. In some of these configurations, main stent-graft 22 is deployed over primary guidewire 50A at least partially in aortic arch 62, such that extension lateral opening 42 is disposed in aortic arch 62 facing upstream, oriented toward an ascending aorta 84, in a vicinity of the bifurcation of aortic arch 62 and BCT 64, such as shown in Figs. 2D-E.

[0229] As shown in Fig. 2F, a through-and-through catheter 90 is deployed over primary guidewire 50A between first vascular access site 52A and third vascular access site 52C, such that (a) a first end portion 92A of through-and-through catheter 90 passes out of vasculature 54 at first vascular access site 52A, and (b) a second end portion 92B of through-and-through catheter 90, opposite first end portion 92A, passes out of vasculature 54 at third vascular access site 52C.

[0230] As shown in Fig. 2G, primary guidewire 50A is removed (withdrawn) from through- and-through catheter 90, leaving through-and-through catheter 90 in place within vasculature 54.

[0231] As shown in Fig 2H, second end portion 58B of secondary guidewire 50B is reinserted into vasculature 54 through third vascular access site 52C via through-and- through catheter 90, so as to form second end portion 58B of secondary guidewire 50B into a loop 94 outside a body of the patient.

[0232] As shown in Fig. 21, second end portion 58B of secondary guidewire 50B is advanced through through-and-through catheter 90 and out of first vascular access site 52A.

[0233] As shown in Fig. 2J, through-and-through catheter 90 is removed from vasculature 54 via first vascular access site 52A.

[0234] As shown in the transition between Fig. 2 J and Fig. 2K, loop 94 is drawn into vasculature 54 via third vascular access site 52C, typically by pulling on second end portion 58B of secondary guidewire 50B outside of first vascular access site 52A. As a result, secondary guidewire 50B is deployed between first vascular access site 52A and second vascular access site 52B, such that: • secondary guidewire 50B is positioned partially within first branch 60, partially within aortic arch 62, and partially within second branch 70, and

[0235] • secondary guidewire 50B is positioned passing between distal main-fluid-flow guide end opening 27B and main-fluid-flow guide lateral opening 30, via a portion of a lumen 98 defined by main stent-graft 22.

[0236] Optionally, the steps of the method shown in Figs. 2J and 2K are performed simultaneously, i.e., through-and-through catheter 90 is removed from vasculature 54 as second end portion 58B of secondary guidewire 50B is pulled through first vascular access site 52A.

[0237] As shown in Fig. 2L, branching extension stent- graft 36 is deployed through extension lateral opening 42 so as to form a blood-tight seal between main- stent-graft fluid flow guide 28 and branching-extension- stent- graft fluid flow guide 38. Although the deployment of branching extension stent-graft 36 is shown between the steps of Figs. 2K and 2M, branching extension stent-graft 36 may alternatively be deployed at any point between the steps of Figs. 2E and 2N.

[0238] As shown in Figs. 2M-N, branching stent-graft 24 is deployed by advancing branching stent-graft 24 over secondary guidewire 50B (a) from first vascular access site 52A to within main stent-graft 22, (b) from within main stent-graft 22, and (c) partially into second branch 70 via main-fluid-flow guide lateral opening 30. As a result, branching stentgraft 24 is partially in second branch 70 external to main-fluid-flow guide lateral opening 30 and partially inside main stent-graft 22, forming the blood-tight seal between main-stent- graft fluid flow guide 28 and branching-stent-graft fluid flow guide 34. For example, above-described delivery system 46 may further comprise a branching delivery catheter 80B and a branching inner shaft (not shown), which is shaped so as to define a guidewire longitudinal lumen through which secondary guidewire 50B passes.

[0239] For some applications, main stent- graft 22 comprises an internal support channel 120, such as described in detail hereinbelow with reference to Figs. 4A-C, 4D-F, 5, 6A-C, and 7. In these applications, at this stage of deployment a distal channel-fluid-flow guide end opening 127B of internal support channel 120 faces at least partially distally within main fluid flow guide 28 (e.g., partially distally and partially toward a central axis of main fluid flow guide 28, such as shown). In applications in which delivery system 46 of stentgraft system 44 comprises a secondary guidewire tube 140, such as described hereinbelow with reference to Figs. 4A-C and 6A-C, this orientation may facilitate inserting secondary guidewire 50B into distal channel-fluid-flow guide end opening 127B, through internal support channel 120, and through main-fluid-flow guide lateral opening 30. After main stent-graft 22 has been transitioned to the radially-expanded deployment state, as shown in the transition between Fig. 2C and 2D, as described hereinbelow, this orientation may also facilitate advancing branching delivery catheter 80B along this path over secondary guidewire 50B, such as described hereinbelow with reference to Figs. 2M and 2N.

[0240] Typically, branching stent-graft 24 is advanced over secondary guidewire 50B while branching stent-graft 24 is disposed in a radially-compressed delivery state within a portion of branching delivery catheter 80B, such as shown in Fig. 2M. Thereafter, branching stentgraft 24 is released from the portion of branching delivery catheter 80B, such that branching stent- graft 24 transitions to a radially-expanded deployment state at least partially in second branch 70, such as shown in Fig. 2N. Branching stent- graft 24 is typically released from branching delivery catheter 80B by proximally withdrawing the branching delivery catheter.

[0241] As shown in Fig. 20, secondary guidewire 50B is removed from vasculature 54 via first vascular access site 52A or second vascular access site 52B, leaving vascular implant assembly 20 (including main stent-graft 22, branching stent-graft 24, and branching extension stent-graft 36) implanted in vasculature 54.

[0242] Reference is again made to Figs. 2A-O, in particular Figs. 2E-M. The method described hereinabove with reference to these figures uses an anterograde approach. Alternatively, the method is implemented using a retrograde approach, in which internal support channel 120 extends in an opposite direction from that shown in Figs. 1A-D and 2A-O, i.e., faces proximally (i.e., in an inferior direction away from the heart), rather than distally as shown for the anterograde approach. Unlike as shown in Figs. 2D-F, in this alternative retrograde approach, in the state shown in Figs. 2D-F secondary guidewire 50B does not loop around distally before continuing proximally, but instead extends proximally directly from the branch toward the femoral artery. In the retrograde approach, the steps of the method described with reference to Figs. 2G-K are omitted. In the retrograde approach, at the step described with reference to Fig. 2L, distal channel-fluid-flow guide end opening 127B and secondary guidewire 50B face proximally. In the anterograde approach, at the step of the method described with reference to Fig. 2M, secondary guidewire 50B is introduced from a proximal location (e.g., the femoral artery). The remaining steps of the retrograde approach are performed in the same manner as illustrated for the anterograde approach, except that channel-fluid-flow guide end opening 127B faces proximally and branching stent-graft 24 extends proximally within the aorta rather than distally as shown.

[0243] Reference is now made to Fig. 3, which is a schematic illustration of an alternative implantation of vascular implant assembly 20 in vasculature 54, in accordance with an application of the present invention. In this implantation, branching stent-graft 24 is positioned partially in LSA 74. Although this alternative implantation is illustrated using main stent-graft 22 and branching stent-graft 24 of the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1A-B, this alternative implantation may alternatively be used with the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D.

[0244] Reference is made to Figs. 2M-0 and 3. In some applications of the present invention, a method is provided that comprises:

[0245] • endovascularly introducing a vascular implant 100 into vasculature 54 through a vascular access site 52 that is downstream of first branch 60 of aortic arch 62; vascular implant 100 may comprise branching stent-graft 24 or another vascular implant, such as a non-branching stent-graft, an uncovered stent, or a balloon catheter, and / or vascular access site 52 may be first vascular access site 52A or another vascular access site;

[0246] • thereafter, advancing vascular implant 100 through first branch 60 to aortic arch 62, such as shown in Fig. 2M;

[0247] • thereafter, advancing vascular implant 100 from aortic arch 62 at least partially into second branch 70 of aortic arch 62; and

[0248] • thereafter, deploying vascular implant 100 at least partially in second branch 70, such as shown in Fig. 2N.

[0249] For some applications in which vascular access site 52 is first vascular access site 52A, the method further comprises deploying a guidewire 50 between first vascular access site 52A and second vascular access site 52B that is downstream of second branch 70. As a result, the guidewire is positioned partially within first branch 60, partially within aortic arch 62, and partially within second branch 70, such as shown in Fig. 2M for secondary guidewire 50B. Advancing vascular implant 100 through first branch 60 to aortic arch 62 and from aortic arch 62 at least partially into second branch 70 comprises:

[0250] • advancing vascular implant 100 over guidewire 50 through first branch 60 to aortic arch 62; and

[0251] • thereafter, advancing vascular implant 100 over guidewire 50 from aortic arch 62 at least partially into second branch 70.

[0252] For some of these applications in which guidewire 50 is deployed between first vascular access site 52A and second vascular access site 52B, vascular implant 100 is endovascularly introduced into vasculature 54 while vascular implant 100 is disposed in a radially-compressed delivery state within a portion of a delivery catheter 80, such as branching delivery catheter 80B, such as shown in Fig. 2M for branching stent-graft 24. Vascular implant 100 is advanced through first branch 60 to aortic arch 62 and from aortic arch 62 at least partially into second branch 70, by advancing the portion of delivery catheter 80 through first branch 60 to aortic arch 62 and from aortic arch 62 at least partially into second branch 70. Vascular implant 100 is deployed at least partially in second branch 70 by releasing vascular implant 100 from the portion of delivery catheter 80, such that vascular implant 100 transitions to a radially-expanded deployment state at least partially in second branch 70.

[0253] Reference is still made to Figs. 2A-0 and 3. In some applications of the present invention, a method is provided that comprises:

[0254] • deploying guidewire 50 between (i) first vascular access site 52A that is downstream of first branch 60 of aortic arch 62 and (ii) second vascular access site 52B that is downstream of second branch 70 of aortic arch 62, such that guidewire 50 is positioned partially within first branch 60, partially within aortic arch 62, and partially within second branch 70, such as shown in Figs. 2K-L for secondary guidewire 50B;

[0255] • advancing vascular implant 100 over guidewire 50, such as shown in Fig. 2M for branching stent- graft 24; and

[0256] • deploying vascular implant 100 within vasculature of the patient, such as shown in Fig. 2N for branching stent-graft 24. Vascular implant 100 may comprise branching stent-graft 24 or another vascular implant, such as a non-branching stent-graft, an uncovered stent, or a balloon catheter.

[0257] For some applications, deploying guidewire 50 between first vascular access site 52A and second vascular access site 52B, such that guidewire 50 is positioned partially within first branch 60, partially within aortic arch 62, and partially within second branch 70, comprises:

[0258] • deploying guidewire 50 between (i) second vascular access site 52B and (ii) third vascular access site 52C that is downstream of descending aorta 66, such as shown in Fig. 2N for secondary guidewire 50B, such that:

[0259] ■ guidewire 50 is positioned partially within second branch 70, partially within aortic arch 62, and partially within descending aorta 66,

[0260] ■ a first end portion 56 of guidewire 50 passes out of vasculature 54 at second vascular access site 52B, and

[0261] ■ a second end portion 58 of guidewire 50, opposite first end portion 56, passes out of vasculature 54 at third vascular access site 52C;

[0262] • forming second end portion 58 of guide wire 50 into loop 94 outside a body of the patient by reinserting the second end portion of guidewire 50 into vasculature 54 through third vascular access site 52C, such as shown in Fig. 2H for secondary guidewire 50B; and

[0263] • thereafter, advancing second end portion 58 of guidewire 50 (a) through descending aorta 66, (b) through a portion of aortic arch 62, (c) through at least a portion of first branch 60, and (d) out of first vascular access site 52A, such that loop 94 is drawn into vasculature 54 via third vascular access site 52C, such as shown in Figs. 2I-K for secondary guidewire 50B.

[0264] For some applications in which guidewire 50 is secondary guidewire 50B, secondary guidewire 50B is deployed between first vascular access site 52A and second vascular access site 52B by deploying primary guidewire 50A between first vascular access site 52A and third vascular access site 52C, such that (a) first end portion 56A of primary guidewire 50A passes out of vasculature 54 at first vascular access site 52A, and (b) second end portion 58A of primary guidewire 50A, opposite first end portion 56A of primary guidewire 50A, passes out of vasculature 54 at third vascular access site 52C, such as shown in Fig. 2B. Optionally, some or all of the steps of the method described hereinabove with reference to Figs. 2C-J are additionally performed.

[0265] For some applications, vascular implant 100 is advanced over guidewire 50 while vascular implant 100 is disposed in a radially-compressed delivery state within a portion of delivery catheter 80, such as branching delivery catheter 80B, such as shown in Fig. 2M for branching stent-graft 24. Vascular implant 100 is deployed within vasculature 54 by releasing vascular implant 100 from the portion of delivery catheter 80, such that vascular implant 100 transitions to a radially-expanded deployment state within vasculature 54, such as shown in Fig. 2N for branching stent-graft 24.

[0266] For some applications, vascular implant 100 is advanced over guidewire 50 from first vascular access site 52A to aortic arch 62, and from aortic arch 62 at least partially into second branch 70, such as shown in Figs. 2M-N for branching stent-graft 24. Optionally, before deploying branching stent-graft 24 within vasculature 54, main stent-graft 22 is deployed at least partially in aortic arch 62, such that main-fluid-flow guide lateral opening 30 is oriented toward second branch 70, such as described hereinabove with reference to Figs. 2M-N.

[0267] Reference is still made to Figs. 2A-0 and 3. Optionally, the deployment techniques described herein are implemented in combination with one or more of the deployment techniques described in US Patent 8,945,203 to Shalev et al., which is incorporated herein by reference.

[0268] Reference is again made to Fig. 1A and is also made to Figs. 4A-C, which are sideview schematic illustrations of internal support channel 120 of main stent-graft 22 in an expanded state, a partially-collapsed state, and a collapsed state, respectively, in accordance with an application of the present invention. For example, internal support channel 120 may assume the partially-collapsed state during a transition from the expanded state to the collapsed state during manufacture, and / or during a transition from the collapsed state to the expanded state during deployment, such as described hereinbelow. Although Figs. 4A- C illustrate main stent-graft 22 and branching stent-graft 24 of the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1A-B, many of the features described with reference to Figs. 4A-C are also applicable to the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D, mutatis mutandis. Figs. 4A-C also show a portion of a stent-graft system 44, which comprises a main stent-graft, such as, by way of example and not limitation, main stent-graft 22, described hereinabove with reference to Figs. 1A-3.

[0269] Reference is also made to Fig. 5, which is a schematic illustration of a flexible channel stent member 126 of internal support channel 120 in the expanded state, from a partially distal and partially side view, in accordance with an application of the present invention. For clarity of illustration, channel fluid flow guide 128 is not shown in Fig. 5, although it is actually present. Flexible channel stent member 126 shown in Fig. 5 may be implemented with either the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1 A-B or the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D.

[0270] In these configurations, internal support channel 120 is configured to assume expanded and collapsed states, such as shown in Figs. 4A-C. Internal support channel 120 is disposed within main fluid flow guide 28. Internal support channel 120 comprises a generally tubular channel fluid flow guide 128, which is shaped so as to define:

[0271] • proximal and distal channel-fluid-flow end openings 127A and 127B, and

[0272] • when internal support channel 120 is in the expanded state, as shown in Fig. 4A, a channel lumen 129 between proximal and distal channel-fluid-flow end openings 127 A and 127B.

[0273] Proximal channel-fluid-flow end opening 127A is sealingly coupled to a perimeter of main-fluid-flow guide lateral opening 30, typically around the entire perimeter of the lateral opening, such that channel lumen 129 is in fluid communication with outside main fluid flow guide 28 via main-fluid-flow guide lateral opening 30 when internal support channel 120 is in the expanded state.

[0274] For some applications, such as shown in Figs. 1C-D, an external surface 131 (labeled in Figs. 1C and Fig. 4A) of internal support channel 120 is coupled to an internal surface 133 of main fluid flow guide 28 such that internal support channel 120 runs alongside the internal surface of main fluid flow guide 28 distally from main-fluid-flow guide lateral opening 30. Typically, in these applications, tubular channel fluid flow guide 128 is coupled to internal surface 133 of main fluid flow guide 28, such as by being coupled (e.g., by stitching 137) to one or more struts of main- stent-graft stent member 26. (Stitching 137 is in addition to any other stitching (shown by way of example as smaller than stitching 137) that couples main fluid flow guide 28 itself to the struts of main-stent-graft stent member 26.)

[0275] As shown in Fig. 4C, when internal support channel 120 is in the collapsed state, distal channel-fluid-flow guide end opening 127B faces radially inward (i.e., toward a central longitudinal axis 135 of main fluid flow guide 28).

[0276] As shown in Fig. 4 A, when internal support channel 120 is in the expanded state and main stent-graft 22 is in the radially-expanded deployment state, distal channel-fluid- flow guide end opening 127B faces at least partially distally within main fluid flow guide 28 (optionally angled with respect to central longitudinal axis 135 of main fluid flow guide 28, such as shown). Typically, when internal support channel 120 is in the expanded state and main stent-graft 22 is in the radially-expanded deployment state, distal channel-fluid- flow guide end opening 127B is disposed distal to main-fluid-flow guide lateral opening 30.

[0277] In some applications of the present invention, stent-graft system 44 further comprises a secondary guidewire tube 140, which is removably positioned passing sequentially through:

[0278] • typically, proximal catheter end 83,

[0279] • proximal main-fluid-flow guide end opening 27 A,

[0280] • inside a longitudinal portion 142 of main fluid flow lumen 29,

[0281] • distal channel-fluid-flow guide end opening 127B,

[0282] • main-fluid-flow guide lateral opening 30,

[0283] • along the outside of main fluid flow lumen 29, and

[0284] • typically, out of (e.g., 0.5 - 2 cm, e.g., about 1 cm out of), or terminating at the same level as, distal catheter end 82.

[0285] In this configuration, secondary guide wire tube 140 is an implementation of an elongate member 160A, which is removably positioned passing sequentially through (a) proximal main-fluid-flow guide end opening 27 A, (b) longitudinal portion 142 of main fluid flow lumen 29, (c) distal channel-fluid-flow guide end opening 127B, and (d) main-fluid- flow guide lateral opening 30 to outside main fluid flow lumen 29. Secondary guidewire tube 140 is shaped so as to define a secondary-guidewire-tube lumen for insertion therethrough of the secondary guidewire 50B, such as described hereinbelow with reference to Fig. 6B.

[0286] In this configuration, secondary guidewire 50B typically has a diameter of 0.012" - 0.016" (0.305 - 0.406 mm), such as 0.014" (0.356 mm).

[0287] In this configuration, internal support channel 120 is configured to automatically transition to the expanded state when:

[0288] • not constrained in the collapsed state by main stent-graft 22, such as when at least a longitudinal portion of main stent-graft 22 alongside internal support channel 120 is in the radially-expanded deployment state, such as shown in Fig. 2D, or is transitioning to the radially-expanded deployment state as internal support channel 120 automatically transitions to the expanded state, and

[0289] • not constrained by secondary guidewire tube 140, such as (i) after removal of secondary guidewire tube 140, such as described hereinbelow with reference to Fig. 6C, or (ii) if secondary guidewire tube 140 is allowed to pass loosely through internal support channel 120 (i.e., secondary guidewire tube 140 is not tensed sufficiently to constrain internal support channel 120 in the collapsed state).

[0290] For some applications, main stent-graft 22 is configured such that secondary guidewire tube 140 is removable from internal support channel 120 while main stent-graft 22 is in the radially-compressed delivery state, such as described hereinbelow with reference to Fig. 6C. In these applications, internal support channel 120 becomes not constrained by secondary guidewire tube 140 before becoming not constrained by main stent-graft 22.

[0291] Alternatively or additionally, for some applications, main stent-graft 22 is configured such that secondary guidewire tube 140 is removable from internal support channel 120 while main stent- graft 22 is in the radially -compressed delivery state and secondary guidewire 50B is inserted through the secondary-guidewire-tube lumen, such as described hereinbelow with reference to Fig. 6C.

[0292] For some applications, as labeled in Fig. 4C, a longitudinal portion 144 of secondary guide wire tube 140 includes: • a first longitudinal sub-portion 144A extending between proximal main-fluid-flow guide end opening 27 A and main-fluid-flow guide lateral opening 30, via distal channel- fluid-flow guide end opening 127B, and

[0293] • a second longitudinal sub-portion 144B extending out of main-fluid-flow guide lateral opening 30, outside main fluid flow lumen 29, and having a length of 1 cm, measured from main-fluid-flow guide lateral opening 30 to a distal end 146 of second longitudinal sub-portion 144B.

[0294] Typically, secondary guidewire tube 140 further includes a distal portion extending distally from distal end 146 of second longitudinal sub-portion 144B, and out of distal catheter end 82 of main delivery catheter 80A.

[0295] For some applications, such as shown in Fig. 4C, when distal end 146 of second longitudinal sub-portion 144B is held in contact with an external surface of main stent- graft 22 (such as by main delivery catheter 80A) while main stent-graft 22 is in the radially- compressed delivery state, longitudinal portion 144 of secondary guidewire tube 140:

[0296] • is almost straight, i.e., has a smallest radius of curvature, at any location along longitudinal portion 144, that is at least 0.15 cm, such as at least 0.3 cm, at least 0.5 cm, at least 1 cm, at least 2 cm, at least 3 cm, or at least 5 cm,

[0297] • is not folded,

[0298] • is not kinked,

[0299] • is neither folded nor kinked, and / or

[0300] • defines a directional path 148 from proximal main-fluid-flow guide end opening 27A to distal end 146 of second longitudinal sub-portion 144B, and directional path 148 does not include any proximally -directed portions.

[0301] The above-mentioned properties may enable insertion of secondary guidewire 50B through the secondary-guidewire-tube lumen while main stent-graft 22 is in the radially- compressed delivery state, such as described hereinbelow with reference to Fig. 6B.

[0302] For some applications, such as shown in Fig. 4C, internal support channel 120 is configured such that when internal support channel 120 is in the collapsed state, a proximal- most point 150A of distal channel-fluid-flow guide end opening 127B is disposed proximal of a distal-most point 150B of main-fluid-flow guide lateral opening 30. Secondary guidewire tube 140 passes through a gap 151 defined between proximal-most point 150A and distal-most point 150B. (Gap 151 is defined by axially overlapping portions of distal channel-fluid-flow guide end opening 127B and main-fluid-flow guide lateral opening 30.)

[0303] For some applications, during loading of main stent-graft 22 into main delivery catheter 80A prior to introduction into vasculature 54, tongue-shaped stent strut 152 is folded proximally back on itself (as illustrated in the transition between Fig. 4A and Fig. 4C). This folding may be facilitated by:

[0304] • passing secondary guidewire tube 140 sequentially through proximal main-fluid- flow guide end opening 27 A, inside a longitudinal portion 142 of main fluid flow lumen 29, distal channel-fluid-flow guide end opening 127B, main-fluid-flow guide lateral opening 30, and along the outside of main fluid flow lumen 29, as shown in Fig. 4A, and

[0305] • applying tension to secondary guidewire tube 140 before and during compression of main stent-graft 22 into main delivery catheter 80A; the tension primarily helps fold tongue-shaped stent strut 152 in the right orientation (extending proximally) for compression of internal support channel 120; the tension also constrains internal support channel 120 in the collapsed state.

[0306] Reference is now made to Figs. 4D-F, which are side-view schematic illustrations of internal support channel 120 of main stent-graft 22 in the expanded state, the partially- collapsed state, and the collapsed state, respectively, in accordance with another application of the present invention. In this configuration, unlike the configuration described hereinabove with reference to Figs. 4A-C, stent-graft system 44 does not comprise secondary guidewire tube 140. Instead, secondary guidewire 50B is removably prepositioned passing sequentially through:

[0307] • typically, proximal catheter end 83,

[0308] • proximal main-fluid-flow guide end opening 27 A,

[0309] • inside longitudinal portion 142 of main fluid flow lumen 29,

[0310] • distal channel-fluid-flow guide end opening 127B,

[0311] • main-fluid-flow guide lateral opening 30,

[0312] • along the outside of main fluid flow lumen 29, and • typically, out of (e.g., 150 - 500 cm, such as 200 - 400 cm out of) distal catheter end 82.

[0313] In this configuration, secondary guidewire 50B is an implementation of an elongate member 160B, which is removably positioned passing sequentially through (a) proximal main-fluid-flow guide end opening 27A, (b) longitudinal portion 142 of main fluid flow lumen 29, (c) distal channel-fluid-flow guide end opening 127B, and (d) main-fluid-flow guide lateral opening 30 to outside main fluid flow lumen 29.

[0314] In this configuration, secondary guidewire 50B typically has a diameter of 0.016" - 0.02" (0.406 - 0.508 mm), such as 0.018" (0.457 mm).

[0315] In this configuration, internal support channel 120 is configured to automatically transition to the expanded state when:

[0316] • not constrained in the collapsed state by main stent-graft 22, such as when at least a longitudinal portion of main stent-graft 22 alongside internal support channel 120 is in the radially-expanded deployment state, such as shown in Fig. 2D, or is transitioning to the radially-expanded deployment state as internal support channel 120 automatically transitions to the expanded state, and

[0317] • not constrained by secondary guidewire 50B. As shown in Fig. 2D, secondary guidewire 50B does not constrain internal support channel 120, even though secondary guidewire 50B passes loosely through internal support channel 120. (Typically, secondary guidewire 50B only constrains internal support channel 120 during loading of main stent-graft 22 into main delivery catheter 80A, as described below.)

[0318] For some applications, as labeled in Fig. 4F, a longitudinal portion 144 of secondary guide wire 50B:

[0319] • a first longitudinal sub-portion 144A extending between proximal main-fluid-flow guide end opening 27 A and main-fluid-flow guide lateral opening 30, via distal channel- fluid-flow guide end opening 127B, and

[0320] • a second longitudinal sub-portion 144B extending out of main-fluid-flow guide lateral opening 30, outside main fluid flow lumen 29, and having a length of 1 cm, measured from main-fluid-flow guide lateral opening 30 to a distal end 146 of second longitudinal sub-portion 144B. As mentioned above, secondary guidewire 50B further includes a distal portion extending distally from distal end 146 of second longitudinal sub-portion 144B, and out of distal catheter end 82 of main delivery catheter 80A.

[0321] For some applications, such as shown in Fig. 4F, when distal end 146 of second longitudinal sub-portion 144B is held in contact with an external surface of main stent- graft 22 (such as by main delivery catheter 80A) while main stent-graft 22 is in the radially- compressed delivery state, longitudinal portion 144 of secondary guidewire 50B:

[0322] • is almost straight, i.e., has a smallest radius of curvature, at any location along longitudinal portion 144, that is at least 0.15 cm, such as at least 0.3 cm, at least 0.5 cm, at least 1 cm, at least 2 cm, at least 3 cm, or at least 5 cm,

[0323] • is not folded,

[0324] • is not kinked,

[0325] • is neither folded nor kinked, and / or

[0326] • defines a directional path 148 from proximal main-fluid-flow guide end opening 27A to distal end 146 of second longitudinal sub-portion 144B, and directional path 148 does not include any proximally -directed portions.

[0327] The above-mentioned properties may prevent damage (such as kinking) to secondary guidewire 50B while main stent-graft 22 is in the radially-compressed delivery state, such as described hereinabove with reference to Fig. 2C and hereinbelow with reference to Fig. 7.

[0328] As described hereinabove with reference to Figs. 4C, and as also shown in Fig. 4F, for some applications, internal support channel 120 is configured such that when internal support channel 120 is in the collapsed state, proximal-most point 150A of distal channelfluid-flow guide end opening 127B is disposed proximal of distal-most point 150B of main- fluid-flow guide lateral opening 30. In the configuration shown in Fig. 4F, secondary guidewire 50B passes through gap 151 defined between proximal-most point 150A and distal-most point 150B. (Gap 151 is defined by axially overlapping portions of distal channel-fluid-flow guide end opening 127B and main-fluid-flow guide lateral opening 30.)

[0329] For some applications, during loading of main stent-graft 22 into main delivery catheter 80A prior to introduction into vasculature 54, tongue-shaped stent strut 152 is folded proximally back on itself (as illustrated in the transition between Fig. 4D and Fig. 4E). This folding may be facilitated by:

[0330] • passing secondary guidewire 50B sequentially through proximal main-fluid-flow guide end opening 27 A, inside longitudinal portion 142 of main fluid flow lumen 29, distal channel-fluid-flow guide end opening 127B, main-fluid-flow guide lateral opening 30, and along the outside of main fluid flow lumen 29, as shown in Fig. 4D, and

[0331] • applying tension to secondary guide wire 50B before and during compression of main stent-graft 22 into main delivery catheter 80A; the tension primarily helps fold tongue-shaped stent strut 152 in the right orientation (extending proximally) for compression of internal support channel 120; the tension also constrains internal support channel 120 in the collapsed state.

[0332] Reference is now made to both Figs. 4A-C and Fig. 4D-F. For some applications, internal support channel 120 further comprises flexible channel stent member 126 to which channel fluid flow guide 128 is securely attached.

[0333] For some of these applications, channel stent member 126 comprises one or more stent struts, which are shaped so as to define a tongue-shaped stent strut 152. Tongueshaped stent strut 152, typically including a tip 154 thereof, is securely attached to a portion of a perimeter of distal channel-fluid-flow guide end opening 127B, so as to help define distal channel-fluid-flow guide end opening 127B.

[0334] Reference is still made to both Figs. 4A-C and Fig. 4D-F. For some applications, a minimal surface 156 defined by tongue-shaped stent strut 152 faces:

[0335] • at least partially distally when internal support channel 120 is in the expanded state, as shown in Figs. 4A and 4D, and

[0336] • at least partially radially inward (i.e., toward central longitudinal axis 135) when internal support channel 120 is in the collapsed state, as shown in Figs. 4C and 4F.

[0337] As used in the present application, including the claims and Inventive Concepts, the "minimal surface" defined by tongue-shaped stent strut 152 is the mathematical surface bounded by the two sides and tip of tongue-shaped stent strut 152 that locally minimizes its area, in accordance with the definition of "minimal surface" known in the mathematical arts. It will be appreciated that the minimal surface is a mathematical construct, rather than a physical element of internal support channel 120.

[0338] Reference is still made to both Figs. 4A-C and Fig. 4D-F. For some applications, tongue-shaped stent strut 152 is configured such that, during the automatic transition of internal support channel 120 from the collapsed state (shown in Figs. 4C and 4F) to the expanded state (shown in Figs. 4A and 4D), tip 154 of tongue-shaped stent strut 152 automatically swings along a curved path 157 from facing proximally to facing less proximally, such as partially distally.

[0339] Reference is still made to both Figs. 4A-C and Fig. 4D-F. For some applications, tongue-shaped stent strut 152 is configured such that, during the automatic transition of internal support channel 120 from the collapsed state (shown in Figs. 4C and 4F) to the expanded state (shown in Figs. 4A and 4D), tongue-shaped stent strut 152 automatically swings:

[0340] • from minimal surface 156 facing at least partially radially inward (i.e., toward central longitudinal axis 135),

[0341] • to minimal surface 156 facing at least partially distally.

[0342] Reference is still made to both Figs. 4A-C and Fig. 4D-F. For some applications, internal support channel 120 is configured such that, during the automatic transition of internal support channel 120 from the collapsed state (shown in Figs. 4C and 4F) to the expanded state (shown in Figs. 4A and 4D), a best-fit plane defined by distal channel-fluid- flow guide end opening 127B automatically swings:

[0343] • from distal channel-fluid-flow guide end opening 127B facing at least partially radially inward (i.e., toward central longitudinal axis 135), to distal channel-fluid-flow guide end opening 127B facing at least partially distally.

[0344] Reference is now made to Figs. 6A-C, which are schematic illustrations of several stages of a portion of a method for deploying main stent-graft 22 and branching stent-graft 24, in accordance with an application of the present invention. Figs. 6A-C show main stentgraft 22 disposed in the radially-compressed delivery state within a portion of main delivery catheter 80A. (For clarity of illustration, main stent-graft 22 is shown slightly expanded in Figs. 6A-C, even though it is in practice generally more radially-compressed when in this delivery state.) In some applications, the steps of the method illustrated in Figs. 6A-C are performed (a) after deploying primary guidewire 50A and secondary guidewire 50B, such as described hereinabove with reference to Figs. 2 A and 2B, respectively, and (b) before deploying main stent-graft 22 over primary guidewire 50A, such as described hereinabove with reference to Figs. 2C-E.

[0345] For some applications, such as shown in Fig. 6A, stent-graft system 44 further comprises main delivery catheter 80A, such as described hereinabove with reference to Figs. 2C-E. Main stent-graft 22 is removably disposed within main delivery catheter 80A in the radially-compressed delivery state with distal main-fluid-flow guide end opening 27B facing distal catheter end 82 of main delivery catheter 80A, and internal support channel 120 in the collapsed state.

[0346] As shown in Fig. 6A, secondary guidewire tube 140 is removably positioned passing sequentially through (a) a proximal catheter end 83 of main delivery catheter 80A, (b) proximal main-fluid-flow guide end opening 27 A, (c) longitudinal portion 142 of main fluid flow lumen 29, (d) distal channel-fluid-flow guide end opening 127B, (e) main-fluid-flow guide lateral opening 30 to outside main fluid flow lumen 29 within main delivery catheter 80A, and (f) distal catheter end 82.

[0347] For some applications, as shown in Fig. 6A, longitudinal portion 144 (labeled in Fig. 4C) of secondary guidewire tube 140:

[0348] • extends between proximal main-fluid-flow guide end opening 27A of the radially- compressed main stent-graft 22 and distal catheter end 82, and is almost straight, i.e., has a smallest radius of curvature, at any location along longitudinal portion 144, that is at least 0.15 cm, such as at least 0.3 cm, at least 0.5 cm, at least 1 cm, at least 2 cm, at least 3 cm, or at least 5 cm,

[0349] • extends between proximal main-fluid-flow guide end opening 27A of the radially- compressed main stent-graft 22 and distal catheter end 82, and is neither folded nor kinked, and / or

[0350] • defines a directional path from proximal main-fluid-flow guide end opening 27 A of the radially-compressed main stent-graft 22 to distal catheter end 82, and the directional path does not include any proximally-directed portions. As shown in Fig. 6B, secondary guidewire 50B is inserted through the secondary- guidewire-tube lumen of secondary guidewire tube 140 that is removably positioned passing sequentially through (a) proximal main-fluid-flow guide end opening 27 A, (b) longitudinal portion 142 of main fluid flow lumen 29, (c) distal channel-fluid-flow guide end opening 127B, and (d) main-fluid-flow guide lateral opening 30 to outside main fluid flow lumen 29.

[0351] This insertion of secondary guidewire 50B is typically performed while main stentgraft 22 is in the radially-compressed delivery state and while main stent-graft 22 (and main delivery catheter 80A) is outside the patient's body, such as shown in Fig. 6B. Typically, but not necessarily, second end portion 58B of secondary guidewire 50B (which passes out of vasculature 54 at third vascular access site 52C) is inserted into the secondary-guidewire- tube lumen of secondary guidewire tube 140.

[0352] Typically, secondary guidewire 50B is advanced along (e.g., through) delivery system 46 to a delivery handle of delivery system 46.

[0353] In addition, also as shown in Fig. 6B, typically primary guidewire 50A is inserted into guidewire longitudinal lumen 79 of main inner shaft 78 of delivery system 46, also typically while main stent-graft 22 (and main delivery catheter 80A) is outside the patient's body. Typically, but not necessarily, second end portion 58A of primary guidewire 50A (which passes out of vasculature 54 at third vascular access site 52C) is inserted into guide wire longitudinal lumen 79.

[0354] In some applications, such as shown in Fig. 6C, secondary guidewire tube 140 is removed from main stent-graft 22 (and main delivery catheter 80A, as well as entirely from delivery system 46). As a result of this removal, secondary guidewire 50B remains positioned passing sequentially through (a) a proximal catheter end 83 of main delivery catheter 80A, (b) proximal main-fluid-flow guide end opening 27 A, (c) longitudinal portion 142 of main fluid flow lumen 29, (d) distal channel-fluid- flow guide end opening 127B, (e) main-fluid-flow guide lateral opening 30 to outside main fluid flow lumen 29, and (f) and out of distal catheter end 82 of main delivery catheter 80A (secondary guidewire 50B optionally passes from proximal catheter end 83 into a handle of delivery system 46 (not shown)).

[0355] For some applications, this removal of secondary guidewire tube 140 from main stent-graft 22 is performed while main stent-graft 22 (and main delivery catheter 80A) is outside the patient's body, such as shown in Fig. 6C. Alternatively, this removal is performed after the main stent-graft has been introduced into vasculature 54, such as shown in Fig. 2C.

[0356] The method continues as described hereinabove with reference to Figs. 2C-O: main stent-graft 22 is introduced into vasculature 54 while (a) main stent-graft 22 is in the radially-compressed delivery state, and (b) internal support channel 120 is in the collapsed state, in which distal channel-fluid-flow guide end opening 127B faces radially inward within main fluid flow lumen 29. Thereafter, main stent-graft 22 is transitioned to the radially-expanded deployment state, as shown in the transition between Fig. 2C and Fig. 2D. Also as shown in Fig. 2D, internal support channel 120 is configured to automatically transition to the expanded state when not constrained in the collapsed state by main stentgraft 22 and not constrained in the collapsed state by secondary guidewire tube 140. As described above, when internal support channel is in the expanded state, distal channel- fluid-flow guide end opening 127B faces at least partially distally within main fluid flow guide 28. (As shown in Fig. 2D, secondary guidewire 50B does not constrain internal support channel 120, even though secondary guidewire 50B passes loosely through internal support channel 120.)

[0357] When internal support channel 120 is in the expanded state, distal channel-fluid- flow guide end opening 127B faces at least partially distally within main fluid flow guide 28, also as shown in Figs. 2D-O. As described hereinabove with reference to Figs. 2M-N, branching stent-graft 24 is deployed by advancing branching stent-graft 24 over secondary guidewire 50B (a) from first vascular access site 52A to within main stent-graft 22 (via distal main-fluid-flow guide end opening 27B), (b) from within main stent-graft 22, and (c) partially into second branch 70 via main-fluid-flow guide lateral opening 30. As a result, branching stent- graft 24 is partially in second branch 70 external to main-fluid-flow guide lateral opening 30 and partially inside main stent-graft 22. In order to advance branching stent- graft 24 from within main stent-graft 22 and partially into second branch 70, branching stent-graft 24 is advanced (a) from within main stent-graft 22 into distal channelfluid-flow guide end opening 127B of channel fluid flow guide 128 of internal support channel 120, (b) through channel fluid flow guide 128, and (c) out of main-fluid-flow guide lateral opening 30 via proximal channel-fluid-flow end opening 127A. The insertion of branching stent- graft 24 from within main stent-graft 22 into distal channel-fluid-flow guide end opening 127B of channel fluid flow guide 128 is facilitated by the at least partially distal facing of distal channel-fluid-flow guide end opening 127B within main fluid flow guide 28. Typically, branching stent-graft 24 is disposed in its radially-compressed delivery state within a portion of branching delivery catheter 80B during the above-described advancing of branching stent-graft 24.

[0358] Reference is now made to Fig. 7, which is a schematic illustration of a configuration of main stent-graft 22 disposed in the radially-compressed delivery state within a portion of main delivery catheter 80A, in accordance with an application of the present invention. (For clarity of illustration, main stent-graft 22 is shown slightly expanded in Fig. 7, even though it is in practice generally more radially-compressed when in this delivery state.)

[0359] In this configuration, secondary guidewire 50B is removably pre-positioned passing sequentially through (a) a proximal catheter end 83 of main delivery catheter 80A, (b) proximal main-fluid-flow guide end opening 27 A, (c) longitudinal portion 142 of main fluid flow lumen 29, (d) distal channel-fluid-flow guide end opening 127B, (e) main-fluid-flow guide lateral opening 30 to outside main fluid flow lumen 29, and (f) and out of distal catheter end 82 of main delivery catheter 80A (secondary guidewire 50B optionally passes from proximal catheter end 83 into a handle of delivery system 46 (not shown)).

[0360] Reference is now made to Figs. 8A-D, which are schematic illustrations of several stages of an improperly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention.

[0361] Reference is also made to Figs. 9A-C, which are schematic illustrations of several stages of a properly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention.

[0362] In the following description of Figs. 8A-9C, as well as in the description hereinbelow of Figs. 10A-12, rotational directions (counterclockwise and clockwise) and anatomic directions (anterior and posterior) are given by way of example and not limitation, and may be reversed in practice, depending, for example, on the design of the system and the particular vascular location.

[0363] Figs. 8A-D and 9A-C show only a portion of the complete deployment method; the remainder of the method may be implemented as described hereinabove with reference to Figs. 2A-0 and / or Fig. 3. Figs. 8A-D and 9A-C show the arrangement of elongate member 160B described hereinabove with reference to Fig. 7, in which elongate member 160B comprises secondary guidewire 50B. Alternatively, the method may be used for deploying the arrangement of elongate member 160A described hereinabove with reference to Figs. 6A-C, in which elongate member 160A comprises secondary guidewire tube 140. In this configuration, secondary guidewire 50B is inserted through the secondary-guidewire-tube lumen of secondary guidewire tube 140, and secondary guidewire tube 140 is removed from main stent- graft 22 (and main delivery catheter 80A, as well as entirely from delivery system 46), optionally before introduction of main delivery catheter 80A into the vasculature, such as described hereinabove with reference to Fig. 6C.

[0364] Although the method is illustrated as comprising deploying main stent-graft 22 and branching stent-graft 24 of the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1A-B, the method may alternatively be used for deploying the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D, or for deploying one or more other vascular implants, such as one or more uncovered stents, one or more balloon catheters, or one or more stent-grafts other than those of vascular implant assembly 20, for deployment either as illustrated in the figures, or at other deployment locations, such as (a) deploying main stent-graft 22 in the aorta and branching stent-graft 24 in one of the other branches of the aorta, such as a lumbar artery, a musculophrenic artery, a renal artery, a middle suprarenal artery, a visceral artery (a celiac trunk, a superior mesenteric artery, or an inferior mesenteric artery), or a left or right common iliac artery, or (b) deploying main stent-graft 22 in an iliac artery and branching stent- graft 24 in one of the branches of the iliac artery.

[0365] Figs. 8A and 9A (like Fig. 2C, described hereinabove) show main delivery catheter 80A after it has been advanced over primary guidewire 50A and secondary guidewire 50B while main stent-graft 22 is disposed within a portion of main delivery catheter 80A, constrained in a radially-compressed delivery state by main delivery catheter 80A.

[0366] During distal advancement of main delivery catheter 80A through the vasculature of the patient from the third vascular access site 52C to the deployment location in the aorta, main delivery catheter 80A may rotate; such rotation is difficult to both control and to detect. As a result, when main delivery catheter 80A reaches the location shown in Figs. 8A and 9A (and Fig. 2C, described hereinabove), the portion of secondary guidewire 50B outside and near distal catheter end 82 crosses nosecone 86 from the side of nosecone 86 facing away from second branch 70 to the side of nosecone 86 facing toward second branch 70. (At this stage of the procedure, nosecone 86 is coupled to distal catheter end 82.) The portion of secondary guidewire 50B may cross nosecone 86 either anteriorly, as shown in Fig. 8A, or posteriorly, as shown in Fig. 9A. If the portion of secondary guidewire 50B crosses nosecone 86 anteriorly, secondary guidewire 50B will become entangled with main stent-graft 22, such as described hereinbelow with reference to Figs. 8C-D. On the other hand, if the portion of secondary guidewire 50B crosses nosecone 86 posteriorly, secondary guidewire 50B will not become entangled with main stent-graft 22, such as described hereinbelow with reference to Fig. 9C.

[0367] However, using a fluoroscopic anterior view 85 alone, it is difficult to see whether the portion of secondary guidewire 50B crosses nosecone 86 either anteriorly or posteriorly, because the radiopacity of secondary guidewire 50B is substantially greater than the radiopacity of nosecone 86. (For purposes of illustration, fluoroscopic view 85 is of a phantom in Fig. 8A, as well as in Figs. 9A and 12A, described hereinbelow.)

[0368] In order to ascertain whether the portion of secondary guidewire 50B crosses nosecone 86 either anteriorly or posteriorly, fluoroscopy may additionally be performed from a lateral view 87, as shown in Fig. 9A. In this view, the user (e.g., surgeon) can clearly see which side of the nosecone the guidewire crosses. However, providing the additional fluoroscopic view increases procedure duration and exposes the patient to additional radiation. (Fluoroscopic view 87 is of human anatomy taken during an experimental procedure.)

[0369] As indicated by the arrow in Figs. 8A and 9A, the physician is instructed to rotate main delivery catheter 80A counterclockwise, as viewed in proximal-to-distal direction, i.e., as viewed from the user control handle to which main delivery catheter 80A is coupled. This rotation typically orients main delivery catheter 80A so that main-fluid-flow guide lateral opening 30 is on the side of main delivery catheter 80A that is oriented toward second branch 70 (although main-fluid-flow guide lateral opening 30 is typically not yet positioned at the height of second branch 70 at this stage of the procedure).

[0370] For some applications, delivery system 46, e.g., main delivery catheter 80A and / or main inner shaft 78, may be configured (e.g., biased or shaped) so as to cause, or contribute to, this rotation of main delivery catheter 80A. The user may optionally also be instructed to assist delivery system 46 with this rotation. For example, distal advancement of main delivery catheter 80A (and main inner shaft 78 and nosecone 86) from the axial location shown in Fig. 8A to the axial location shown in Fig. 8B may cause, or contribute to, this rotation. For example, delivery system 46 (e.g., main delivery catheter 80A and / or main inner shaft 78) may be shaped so as to define a curved portion 88, which, together with the shape of other longitudinal portions of delivery system 46, causes distal curved portion 88 to automatically rotationally orient itself to a least constrained state, i.e., to an orientation in which the wall of the aortic arch applies the least force to the longitudinal portion of delivery system 46 including distal curved portion 88. As a result, delivery system 46 causes distal curved portion 88 to:

[0371] • rotate to the outer curvature of the upper portion of the descending aorta when main delivery catheter 80A is advanced to the axial location shown in Fig. 8A, and

[0372] • rotate approximately 180 degrees to away from the outer curvature of the upper portion of descending aorta when main delivery catheter 80A is further advanced to the axial location shown in Fig. 8A.

[0373] Main stent-graft 22 is rotationally disposed within main delivery catheter 80A such that main-fluid-flow guide lateral opening 30:

[0374] • faces away from the outer curvature (and thus from second branch 70) when main delivery catheter 80A is advanced to the axial location shown in Fig. 8A, and

[0375] • faces toward the outer curvature (and thus toward second branch 70) when main delivery catheter 80A is advanced to the axial location shown in Fig. 8B.

[0376] These self-orientation techniques may also be applied at the steps of the methods described with reference to Figs. 2C-D, 9A-B, 11A-B, and 12A-B.

[0377] Distal curved portion 88 (and optionally one or more other curved portions) causes a distal portion of main delivery catheter 80A to automatically rotationally orient itself to a desired rotation in the blood vessel. Therefore, less manual rotation of the delivery shaft assembly by the user is generally necessary than if the one or more curved portions were not provided. The proximal end portion is typically quite long, and thus transmits proximal torque poorly to the distal end portion. In addition, without the one or more curved portions, it may be difficult to properly rotationally orient the delivery shaft assembly before and / or during introduction into the vasculature, because the tortuous vasculature changes the rotation of the delivery shaft assembly as it is advanced.

[0378] Optionally, delivery system 46 implements, mutatis mutandis, all or a portion of the self-orienting techniques described in US Patent Application Publication 2018 / 0021157 to Marmur et al., which is incorporated herein by reference. For example, as shown in the figures herein, delivery system 46 may have fewer curved portions and points of inflection than delivery system 46 described in the '1157 publication.

[0379] Figs. 8B and 9B show main delivery catheter 80A after the counterclockwise rotation. As can be seen in Fig. 8B, because secondary guidewire 50B earlier crossed nosecone 86 anteriorly, as shown in Fig. 8A, the counterclockwise rotation causes secondary guidewire 50B to become wrapped around main delivery catheter 80A. This leads to tangling and an improper deployment, as shown in Figs. 8C and 8D (after main stent- graft 22 has been released from portion of main delivery catheter 80A). If the user ascertains that the orientation of main delivery catheter 80A will result in this improper deployment, the user must reverse and repeat a portion of the procedure in order to properly deploy the stent- grafts. For example, the user may torque main delivery catheter 80A and evaluate whether secondary guidewire 50B becomes more or less wrapped around main delivery catheter 80A. If secondary guidewire 50B became more wrapped, the user may torque main delivery catheter 80A in the opposite direction until secondary guidewire 50B becomes unwrapped. If the torque was applied in the correct rotational direction, the user may ascertain that secondary guidewire 50B became unwrapped and the user may see the secondary guidewire 50B exiting between main delivery catheter 80A and nosecone 86, and thus stop torquing. In addition, in order to rotate main delivery catheter 80A, the user typically must partially proximally withdraw main delivery catheter 80A from the axial location shown in Fig. 8B back to axial location shown in Fig. 8A, which may complicate and / or lengthen the deployment procedure.

[0380] By contrast, as can be seen in Fig. 9B, because secondary guidewire 50B earlier crossed nosecone 86 posteriorly, as shown in Fig. 9A, the counterclockwise rotation does not cause secondary guidewire 50B to become wrapped around main delivery catheter 80A, but instead to cleanly extend toward second branch 70, as shown in Fig. 9C.

[0381] Reference is now made to Figs. 10A and 10B, which are schematic illustrations of another configuration of main stent-graft 22 disposed in the radially -compressed delivery state within a portion of main delivery catheter 80A, in accordance with an application of the present invention. Fig. 10B is a top-view, not shown to scale. (For clarity of illustration, main stent-graft 22 is shown slightly expanded in Figs. 10A-B, even though it is in practice generally more radially-compressed when in this delivery state.) As described in detail hereinbelow, this configuration may help avoid the possible inadvertent incorrect deployment described hereinabove with reference to Figs. 8A-D, without the need for the second fluoroscopic lateral view 87 described hereinabove with reference to Fig. 9A.

[0382] Main stent-graft 22 is removably disposed within main delivery catheter 80A such that main delivery catheter 80A constrains main stent-graft 22 in the radially-compressed delivery state such that main-fluid-flow guide lateral opening 30 is at a first angular location 202 with respect to a central longitudinal axis 200 of main delivery catheter 80A.

[0383] In the configuration shown in Figs. 10A-B, secondary guidewire 50B is an implementation of elongate member 160B, which is removably positioned passing sequentially through:

[0384] • proximal catheter end 83 of main delivery catheter 80A (as shown), or a lateral opening through main delivery catheter 80A (configuration not shown),

[0385] • at least a longitudinal portion 31 of main delivery catheter 80A proximal to proximal main-fluid-flow guide end opening 27 A,

[0386] • proximal main-fluid-flow guide end opening 27 A,

[0387] • longitudinal portion 142 of main fluid flow lumen 29,

[0388] • optionally, distal channel-fluid-flow guide end opening 127B, if internal support channel 120 is provided,

[0389] • main-fluid-flow guide lateral opening 30, at first angular location 202, to outside main fluid flow lumen 29, and

[0390] • out of distal catheter end 82 of main delivery catheter 80A (secondary guidewire 50B optionally passes from proximal catheter end 83 into a handle of delivery system 46 (not shown)).

[0391] Alternatively, secondary guidewire tube 140 may be provided, such as described hereinabove with reference to Figs. 6A-C, in which case secondary guidewire tube 140 would be an implementation of an elongate member 160A, which is removably positioned passing sequentially through (a) proximal main-fluid-flow guide end opening 27 A, (b) longitudinal portion 142 of main fluid flow lumen 29, (c) distal channel-fluid-flow guide end opening 127B, (d) main-fluid-flow guide lateral opening 30, at first angular location 202, to outside main fluid flow lumen 29, and (e) out of distal catheter end 82 of main delivery catheter 80A, similar to the configuration shown in Figs. 6A-C, mutatis mutandis (including, the lack in Figs. 6A-C of the angular offset described hereinbelow).

[0392] (The phrase "passing sequentially through" includes within its scope both (a) "passing contiguously sequentially through" and (b) "passing non-contiguously sequentially through," i.e., the elongate member additionally passes through intervening element in the sequence of listed elements.)

[0393] Unlike in the configurations shown in Figs. 6A-C and 7, in the configuration shown in Figs. 10A-B, elongate member 160A, 160B exits distal catheter end 82 at a second angular location 204 with respect to central longitudinal axis 200 of main delivery catheter 80A, second angular location 204 offset from first angular location 202 around central longitudinal axis 200 by at least 90 degrees, such as by at least 135 degrees, e.g., by at least 150 degrees, such as by 180 degrees (such as shown).

[0394] Typically, elongate member 160A, 160B wraps around main stent-graft 22 from first angular location 202 to second angular location 204 in a single direction around main stent-graft 22 (i.e., either clockwise or counterclockwise).

[0395] Alternatively or additionally, elongate member 160A, 160B may wrap around main stent-graft 22 from first angular location 202 to second angular location 204 in less than one turn around main stent-graft 22 (i.e., less than 360 degrees around central longitudinal axis 200). In this configuration, elongate member 160A, 160B typically wraps around main stent-graft 22 by either (a) the angular offset or (b) 360 degrees minus the angular offset.

[0396] Reference is still made to Figs. 10A-B, and is further made to Figs. 11A-D, which are schematic illustrations of several stages of an improperly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention.

[0397] Reference is still further made to Figs. 12A-C, which are schematic illustrations of several stages of a properly implemented method for deploying one or more vascular implants, in accordance with an application of the present invention.

[0398] Figs. 11A-D and 12A-C show only a portion of the complete deployment method; the remainder of the method may be implemented as described hereinabove with reference to Figs. 2A-0 and / or Fig. 3. Figs. 11A-D and 12A-C show the arrangement of elongate member 160B described hereinabove with reference to Figs. 10A-B, in which elongate member 160B comprises secondary guidewire 50B. Alternatively, the method may be used for deploying the arrangement of elongate member 160A described hereinabove with reference to Figs. 6A-C, in which elongate member 160A comprises secondary guidewire tube 140. In this configuration, secondary guidewire 50B is inserted through the secondary-guidewire-tube lumen of secondary guidewire tube 140, and secondary guidewire tube 140 is removed from main stent- graft 22 (and main delivery catheter 80A, as well as entirely from delivery system 46), optionally before introduction of main delivery catheter 80A into the vasculature, such as described hereinabove with reference to Fig. 6C (as modified as described hereinabove with reference to Figs. 10A-B regarding second angular location 204).

[0399] Although the method is illustrated as comprising deploying main stent-graft 22 and branching stent-graft 24 of the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1A-B, the method may alternatively be used for deploying the configuration of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D, or for deploying one or more other vascular implants, such as one or more uncovered stents, one or more balloon catheters, or one or more stent-grafts other than those of vascular implant assembly 20, for deployment either as illustrated in the figures, or at other deployment locations, such as (a) deploying main stent-graft 22 in the aorta and branching stent-graft 24 in one of the other branches of the aorta, such as a lumbar artery, a musculophrenic artery, a renal artery, a middle suprarenal artery, a visceral artery (a celiac trunk, a superior mesenteric artery, or an inferior mesenteric artery), or a left or right common iliac artery, or (b) deploying main stent-graft 22 in an iliac artery and branching stent-graft 24 in one of the branches of the iliac artery.

[0400] Figs. 11A and 12A (like Figs. 2C, 8A, and 9A, described hereinabove) show main delivery catheter 80A after it has been advanced over primary guidewire 50A and secondary guidewire 50B while main stent-graft 22 is disposed within a portion of main delivery catheter 80A, constrained in a radially-compressed delivery state by main delivery catheter 80A.

[0401] During distal advancement of main delivery catheter 80A through the vasculature of the patient from the third vascular access site 52C to the deployment location in the aorta, main delivery catheter 80A may rotate; such rotation is difficult to both control and to detect. As a result, when main delivery catheter 80A reaches the location shown in Figs. 11A and 12A (and Figs. 2C, 8A, and 9A, described hereinabove), the portion of secondary guidewire 50B outside and near distal catheter end 82 either: • as shown in Fig. 11A, crosses nosecone 86 twice: (1) from the side of nosecone 86 facing toward second branch 70, and (2) from the side of nosecone 86 facing away from second branch 70 to the side of nosecone 86 facing toward second branch 70, or

[0402] • as shown in Fig. 12A, exits the side of nosecone 86 facing toward second branch 70, without crossing nosecone 86.

[0403] (At this stage of the procedure, nosecone 86 is coupled to distal catheter end 82.)

[0404] If the portion of secondary guidewire 50B crosses nosecone 86, as shown in Fig. 11 A, secondary guidewire 50B will become entangled with main stent-graft 22, such as described hereinbelow with reference to Figs. 11C-D. On the other hand, if the portion of secondary guidewire 50B does not cross nosecone 86, as shown in Fig. 12A, secondary guidewire 50B will not become entangled with main stent-graft 22, such as described hereinbelow with reference to Fig. 12C.

[0405] Unlike in the configuration described hereinabove with reference to Figs. 8A-D and 9A-D, in the configuration described with reference to Figs. 10A-12C, using fluoroscopic anterior view 85 alone, it is easy to see whether:

[0406] • as shown in Fig. 11A (fluoroscopic view omitted), the portion of secondary guidewire 50B crosses nosecone 86 (because the radiopacity of secondary guidewire 50B is substantially greater than the radiopacity of nosecone 86), or

[0407] • as shown in Fig. 12A, the portion of secondary guidewire 50B does not cross nosecone 86.

[0408] Thus, unlike in the configuration described hereinabove with reference to Figs. 8A- D and 9A-D, it is not necessary to perform additional fluoroscopy from lateral view 87 in order to ascertain whether the portion of secondary guidewire 50B crosses or does not cross nosecone 86. The configuration described with reference to Figs. 11A-D and 12A-C thus does not require an additional fluoroscopic view that would increase procedure duration and expose the patient to additional radiation.

[0409] As indicated by the arrow in Figs. 11 A and 12A, the physician is instructed to rotate main delivery catheter 80A counterclockwise, as viewed in proximal-to-distal direction, i.e., as viewed from the user control handle to which main delivery catheter 80A is coupled. This rotation typically orients main delivery catheter 80A so that main-fluid-flow guide lateral opening 30 is on the side of main delivery catheter 80A that faces second branch 70 (although main-fluid-flow guide lateral opening 30 is typically not yet positioned at the height of second branch 70 at this stage of the procedure). Optionally, delivery system 46, e.g., main delivery catheter 80A, may be configured (e.g., biased or shaped) so as to cause, or contribute to, this rotation of main delivery catheter 80A, such as described hereinabove in detail with reference to Figs. 8A-B.

[0410] Figs. 11B and 12B show main delivery catheter 80A after the counterclockwise rotation. As can be seen in Fig. 11B, because secondary guidewire 50B earlier crossed nosecone 86 (twice), as shown in Fig. 11A, the counterclockwise rotation causes secondary guidewire 50B to become even further wrapped around main delivery catheter 80A. This leads to tangling and an improper deployment, as shown in Figs. 11C and 1 ID (after main stent- graft 22 has been released from the portion of main delivery catheter 80A).

[0411] By contrast, as can be seen in Fig. 12B, because secondary guidewire 50B earlier did not cross nosecone 86, as shown in Fig. 12A, the counterclockwise rotation does not cause secondary guidewire 50B to become wrapped entirely around main delivery catheter 80A, but instead to wrap partially (approximately 180 degrees) around main delivery catheter 80A, still extending toward second branch 70, as shown in Figs. 12B and 12C, and thus allowing release of main stent-graft 22 from the portion of main delivery catheter 80A without the main stent-graft 22 becoming entangled in secondary guidewire 50B. This partial wrapping of secondary guidewire 50B does not result in entanglement because of the secondary guidewire's offset of second angular location 204 from first angular location 202, as described hereinabove with reference to Figs. 10A-B, and because the user begins with secondary guidewire 50B facing second branch 70 and subsequently rotates main delivery catheter 80A counterclockwise, which must result in main-fluid-flow guide lateral opening 30 facing the second branch 70. During the proximal withdrawal of main delivery catheter 80A, as seen in the transition between Fig. 12B and Fig. 12C, the route of secondary guidewire 50B radially between main delivery catheter 80A and main stent-graft 22 allows the release of secondary guidewire 50B in the direction of second branch 70 without entanglement with main stent-graft 22.

[0412] If, at the stage of the deployment shown in Figs. 11 A and 12A, the user ascertains, using fluoroscopic anterior view 85, that secondary guidewire 50B crosses nosecone 86 (at least once, typically twice), as shown in Fig. 11 A, the user rotates (e.g., by about 360 degrees) main delivery catheter 80A clockwise, as viewed in proximal-to-distal direction, until secondary guide wire 50B exits the side of nosecone 86 facing toward second branch 70. As a result, secondary guidewire 50B assumes the correct position shown in Fig. 12A, and the user proceeds as described hereinabove with reference to Figs. 12B-C. This corrective rotation is typically performed during advancing main delivery catheter 80A to the axial location shown in Figs. 11B and 12B.

[0413] Reference is now made to Figs. 13A-B, which are schematic illustrations of a vascular implant assembly 220 in disassembled and assembled states, respectively, in accordance with an application of the present invention. Vascular implant assembly 220 typically comprises a main stent-graft 222 and first and second branching stent-grafts 24A and 24B. Main stent-graft 222 and first and second branching stent-grafts 24 A and 24B are shown in radially-expanded deployment states in Figs. 13A-B.

[0414] Reference is also made to Fig. 14, which is a schematic illustration of an alternative configuration of main stent-graft 222, in accordance with an application of the present invention.

[0415] Other than as described below, main stent-graft 222 may be identical to main stentgraft 22, described hereinabove with reference to Figs. 1A-B and / or Figs. 1C-D, and may implement any of the dimensions and / or other features thereof, mutatis mutandis. Like reference numerals refer to like parts. Main- stent-graft fluid flow guide 28 of main stentgraft 222 is shaped so as to define two main-fluid-flow guide lateral openings 30.

[0416] Branching stent-grafts 24A and 24B may be identical to branching stent-graft 24, described hereinabove with reference to Figs. 1 A-B and / or Figs. 1C-D, and may implement any of the dimensions and / or other features thereof, mutatis mutandis. First and second branching stent-grafts 24A and 24B are configured to be disposed through respective ones of main- fluid-flow guide lateral openings, so as to form respective blood-tight seals between respective branching- stent- graft fluid flow guides 34 and:

[0417] • respective portions of main-stent-graft fluid flow guide 28 that define the perimeter of main-fluid-flow guide lateral openings, such as shown in Fig. 13B, and / or

[0418] • respective internal surfaces of respective tubular channel fluid flow guides 128 of internal support channels 120, in applications in which main stent- graft 222 comprises internal support channels 120, such as shown in Fig. 13B, and such as described in detail hereinabove with reference to Figs. 4A-C, 4D-F, 5, 6A-C, and 7. For some applications, such as shown in Figs. 13A-B, main-fluid-flow guide lateral openings 30 and respective internal support channels 120 are disposed at respective different axial locations along main stent-graft 222. For other applications, such as shown in Fig. 14, main-fluid-flow guide lateral openings 30 and respective internal support channels 120 are disposed at respective different angular locations about a central longitudinal axis of main stent-graft 222, optionally at the same axial location along main stent-graft 222, such as shown in Fig. 14, or at respective different axial locations along main stent-graft 222 (configuration not shown).

[0419] For some applications, main stent-graft 222 is configured to be positioned partially in a descending aorta 66, partially in an aortic arch 62, and partially in a first branch 60 of aortic arch 62. For example, first branch 60 may be a brachiocephalic artery (BCT) 64.

[0420] For some applications, first branching stent-graft 24A is configured to be positioned partially in a second branch 70 of aortic arch 62 and partially within main stent-graft 22 within aortic arch 62. For example, second branch 70 may be LCCA 72 (as shown in Figs. 18I-Q and Figs. 20B-H, described hereinbelow) or LSA 74 (configuration not shown).

[0421] Second branching stent-graft 24B is configured to be positioned partially in a third branch 73 of aortic arch 62 and partially within main stent-graft 22 within aortic arch 62. Typically, third branch 73 is LSA 74 in configurations in which second branch 70 is LCCA 72 (as shown in Figs. 18I-Q and Figs. 20B-H, described hereinbelow), or is LCCA 72 in configurations in which second branch 70 is LSA 74 (configuration not shown).

[0422] For some applications, vascular implant assembly 220 further comprises branching extension stent-graft 36, described hereinabove with reference to Figs. 1A-B and 1C-D.

[0423] Reference is now made to Figs. 15A and 15B, which are schematic illustrations of a configuration of main stent-graft 222 disposed in a radially-compressed delivery state within a portion of main delivery catheter 80A, in accordance with an application of the present invention. Fig. 15B is a top-view, not shown to scale. (For clarity of illustration, main stent-graft 222 is shown slightly expanded in Figs. 15A-B, even though it is in practice generally more radially-compressed when in this delivery state.)

[0424] By way of example and not limitation, Figs. 15A-B show the configuration of main stent- graft 222 described hereinabove with reference to Figs. 13A-B. Alternatively, the configuration of main stent-graft 222 described hereinabove with reference to Fig. 14 may be similarly disposed in main delivery catheter 80A. For some applications, a stent-graft system 244 is provided that comprises vascular implant assembly 220 and a delivery system 246, which comprises main delivery catheter 80A and, typically, main inner shaft 78. Main inner shaft 78 is removably disposed at least partially within main delivery catheter 80A, and is shaped so as to define a guidewire longitudinal lumen 79 through which primary guidewire 50A can be inserted and pass. Typically, delivery system 46 further comprises nosecone 86, as is known in the catheter art, which is typically coupled to a distal end of main inner shaft 78.

[0425] Reference is further made to Fig. 16, which is a schematic illustration of a control handle 230 of delivery system 246, in accordance with an application of the present invention.

[0426] Main stent-graft 222 is removably disposed within main delivery catheter 80A such that main delivery catheter 80A constrains main stent-graft 222 in the radially-compressed delivery state such that main-fluid-flow guide lateral openings 30 are at first angular location 202 with respect to central longitudinal axis 200 of main delivery catheter 80A.

[0427] In the configuration shown in Figs. 15A-B, secondary guidewire 50B is an implementation of elongate member 160B, which is removably positioned such as described hereinabove with reference to Figs. 10A-B. Alternatively, secondary guidewire tube 140 may be provided, such as described hereinabove with reference to Figs. 6A-C, in which case secondary guidewire tube 140 would be an implementation of an elongate member 160A, which is removably positioned such as described hereinabove with reference to Figs. 10A-B.

[0428] Optionally, as shown in Figs. 15A-B, the elongate member exits distal catheter end 82 at second angular location 204, such as described hereinabove with reference to Figs. 10A-B. Optionally, the elongate member may be arranged in any of the configurations described hereinabove with reference to Figs. 10A-B. Alternatively, the elongate member exits distal catheter end 82 at angular location other than second angular location 204, such as, for example, described hereinabove with reference to Figs. 6A-C and 7.

[0429] Reference is still made to Figs. 15A-B and 16 and is additionally made to Fig. 17, which is a schematic illustration of a portion of delivery system 246, in accordance with an application of the present invention. In some applications of the present invention, delivery system 246 further comprises a sheath-rail guidewire 50C, which is removably positioned passing sequentially through (a) at least a portion of main delivery catheter 80A proximal to proximal main-fluid-flow guide end opening 27 A, (b) proximal main-fluid-flow guide end opening 27 A, (c) a longitudinal portion of main fluid flow lumen 29, (d) one of main- fluid-flow guide lateral openings 30 to outside main fluid flow lumen 29, and (e) distal catheter end 82.

[0430] For some applications, delivery system 246 further comprises nosecone 86 removably coupled to distal catheter end 82, and a fixation tube 248, disposed at least partially distal to nosecone 86. Typically, fixation tube 248 is axially moveable away from nosecone 86. For example, fixation tube 248 may be removably in contact with a distal end portion of nosecone 86, e.g., an axial portion of fixation tube 248 may be removably disposed (inserted) in a distal tip portion of nosecone 86, as shown, while the remainder of fixation tube 248 is disposed distal to nosecone 86.

[0431] Sheath-rail guidewire 50C is coupled to a coupling site 250 on an external surface of fixation tube 248. By way of example and not limitation, sheath-rail guidewire 50C may be coupled to coupling site 250 by (a) an adhesive, (b) a band of material that surrounds fixation tube 248 and is shaped so as to define a slot to receive sheath-rail guidewire 50C, (c) shrink tubing (application of a band of tubing that shrinks when heated), or (d) insertion into a skived area of fixation tube 248 at coupling site 250.

[0432] For some applications, sheath-rail guidewire 50C is removably coupled to coupling site 250, in the sense that sheath-rail guidewire 50C can be decoupled from fixation tube 248 non-destructively during ordinary use of delivery system 246. For other applications, sheath-rail guidewire 50C is permanently coupled to coupling site 250, in the sense that sheath-rail guidewire 50C can be readily decoupled from fixation tube 248 during ordinary use of delivery system 246.

[0433] For some applications, such as shown by way of example in Fig. 17, fixation tube 248 is removably coupled to a distal end portion 252 of main stent-graft 222. Optionally, fixation tube 248 is removably coupled to one or more struts of flexible main-stent-graft stent member 26 of distal end portion 252, such as shown in Fig. 17. In configurations in which fixation tube 248 is axially moveable away from nosecone 86, fixation tube 248 is axially moveable away from nosecone 86 at least after fixation tube 248 has been decoupled from distal end portion 252 of main stent-graft 222, and, optionally, additionally while fixation tube 248 is still removably coupled to distal end portion 252.

[0434] For example, fixation tube 248 may be removably coupled to distal end portion 252 by one or more flexible elongated members 254, such as sutures, wires, or strings, such as shown in Fig. 17 (by way of example, exactly one flexible elongated member 254 is shown in Fig. 17). For example, one or more flexible elongated members 254 may be looped through distal end portion 252 and pass through one or more lumens defined through fixation tube 248 that provides distal access to the one or more flexible elongated members 254. Pulling one end of each of the one or more flexible elongated members 254 unloops and thereby disengages the flexible elongated member from distal end portion 252. Typically, the one or more flexible elongated members 254 pass alongside nosecone 86 outside nosecone 86. (Although the one or more flexible elongated members 254 are not shown in Figs. 15A-B, they may be provided.)

[0435] Fixation tube 248 may help prevent proximal displacement of main stent-graft 222 during deployment, such as after the step of the deployment procedure described hereinbelow with reference to Fig. 18F and before the step of the deployment procedure described hereinbelow with reference to Fig. 18G. Between these steps, a portion of delivery system 246 is within fully -deployed main stent-graft 222, and must be removed from the main stent-graft. Removal of the delivery system might dislodge the distal end portion of main stent-graft 222 from first branch 60 (e.g., BCT 64) during removal of nosecone 86 and main inner shaft 78 from the deployed main stent-graft 222. Applying tension to fixation tube 248 (or removing any slack in fixation tube 248 and the one or more flexible elongated members 254) during the removal of the delivery system prevents proximal migration of main stent-graft 222.

[0436] At this stage of deployment, a distal end of fixation tube 248 is held (e.g., fixed and / or secured) stationary outside distal vascular access site 52A, which prevents proximal movement of fixation tube 248 and the one or more flexible elongated members 254, and thus main stent-graft 222.

[0437] Optionally, fixation tube 248 is implemented in combination, mutatis mutandis, with techniques of the distal restraining assembly described in US Patent 9,993,360 to Shalev et al., which is incorporated herein by reference.

[0438] For some applications, fixation tube 248 is shaped so as to define a lumen for insertion therethrough of primary guidewire 50A. When primary guidewire 50A is inserted within the lumen, fixation tube 248 is typically axially moveable over primary guidewire 50A away from nosecone 86. For some applications, coupling site 250 is:

[0439] • at a distance of at least 30 cm, e.g., at least 35 cm, such as at least 40 cm from a proximal end 256 of fixation tube 248,

[0440] • at a distance of no more than 60 cm, e.g., no more than 50 cm from proximal end 256 of fixation tube 248,

[0441] • at a distance of no more than 5 cm, e.g., no more than 3 cm, such as no more than 2 cm from a distal end 258 of fixation tube 248, and / or

[0442] • at a distance of at least 0.5 cm, such as at least 1 cm from distal end 258 of fixation tube 248.

[0443] The above-mentioned distances are measured along a central longitudinal axis of fixation tube 248 (the central longitudinal axis has the same straightness and / or curvature as the fixation tube).

[0444] Typically, fixation tube 248 has a length of at least 30 cm (e.g., at least 35 cm), no more than 60 cm (e.g. no more than 50 cm), and / or 30 - 60 cm, e.g., 30 - 50 cm, such as 35 - 50 cm; this length is typically long enough for fixation tube 248 to be advanced out of vasculature and the patient's body at distal vascular access site 52A, such as described hereinbelow with reference to Fig. 18E (and Fig. 20A).

[0445] For some applications, sheath-rail guidewire 50C has a diameter of 0.014" - 0.035", such as 0.018" (i.e., 0.3556 mm - 0.889 mm, such as 0.4572 mm).

[0446] As described above, delivery system 246 may further comprise main inner shaft 78, which is removably disposed at least partially within main delivery catheter 80A. For some applications, nosecone 86 and main inner shaft 78 are shaped so as to define respective guidewire longitudinal lumens for insertion therethrough of the primary guidewire 50A.

[0447] In an application of the present invention (not shown), sheath-rail guidewire 50C is coupled to a coupling site on an external surface of nosecone 86, rather than to coupling site 250 on the external surface of fixation tube 248. In this configuration, delivery system 246 may or may not comprise fixation tube 248.

[0448] Reference is made to Figs. 15A-B. Sheath-rail guidewire 50C exits distal catheter end 82 at a third angular location 206 with respect to central longitudinal axis 200 of main delivery catheter 80A. For some applications, third angular location 206 is: • offset from second angular location 204 around central longitudinal axis 200 by at least 90 degrees, such as by at least 135 degrees, e.g., by at least 150 degrees, such as by 180 degrees (such as shown), and / or

[0449] • either (a) at first angular location 202 around central longitudinal axis 200 (such as shown), or (b) offset from first angular location 202 around central longitudinal axis 200 by less than 90 degrees, such as less than 45 degrees.

[0450] Reference is now made to Figs. 18A-Q, which are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention. For some applications, the method is used to treat an aortic arch 62 that suffers from acute aortic syndrome, such an aneurysm, a dissection, a penetrating aortic ulcer (PAU), and / or an intramural hematoma (IMH). Although the method is illustrated as comprising deploying main stent-graft 222 and first and second branching stent-grafts 24A and 24B of the configuration of vascular implant assembly 220 described hereinabove with reference to Figs. 13A-B, the method may alternatively be used for deploying the configuration of vascular implant assembly 220 described hereinabove with reference to Fig. 14, or for deploying one or more other vascular implants, such as one or more uncovered stents, one or more balloon catheters, or one or more stent-grafts other than those of vascular implant assembly 220. In addition, vascular implant assembly 220 may optionally implement features of vascular implant assembly 20 described hereinabove with reference to Figs. 1C-D. The method may include all or only a subset of the steps described hereinbelow, and / or additional steps, including but not limited to those described hereinbelow.

[0451] The method described with reference to Figs. 18A-Q may optionally be implemented in combination with any of the techniques described hereinabove for the methods described with reference to Figs. 2A-O, 9A-C, and / or 12A-C, mutatis mutandis.

[0452] As shown in Fig. 18A, primary guidewire 50A is deployed endovascularly (typically percutaneously) into vasculature 54 of the patient between a proximal vascular access site 52C (which may be referred to hereinabove as third vascular access site 52C) and a distal vascular access site 52A (which may be referred to hereinabove as first vascular access site 52A), such that (a) first end portion 56A of primary guidewire 50A passes out of vasculature 54 at distal vascular access site 52A, and (b) second end portion 58 A of primary guidewire 50A, opposite first end portion 56A of primary guidewire 50A, passes out of vasculature 54 at proximal vascular access site 52C. Primary guidewire 50A may be deployed using techniques known in the art for deploying through-and-through guidewires. Primary guidewire 50A may be introduced into and advanced within the vasculature in either direction (i.e., from distal vascular access site 52A to proximal vascular access site 52C or vice versa).

[0453] Typically, distal vascular access site 52A is downstream of first branch 60 of aortic arch 62. For example, distal vascular access site 52A may be on a right axillary artery (RAA) in applications in which first branch 60 is BCT 64, such as shown.

[0454] Typically, proximal vascular access site 52C is downstream of descending aorta 66. For example, proximal vascular access site 52C may be on a right femoral artery, as illustrated, or a right iliac artery (approach not shown).

[0455] For some applications, the method includes implanting second branching stent-graft 24B partially in third branch 73, for example, LSA 74, such as shown, or LCCA 72 (configuration not shown). For these applications, secondary guidewire 50B is deployed into the third branch (the LSA or the LCCA). Alternatively, such as described hereinbelow with reference to Figs. 20A-G, the method does not include implanting second branching stent-graft 24B, in which case secondary guidewire 50B is not used.

[0456] For some applications in which the method includes implanting second branching stent- graft 24B partially in third branch 73, elongate member 160B is secondary guidewire 50B, as described hereinabove with reference to Figs. 15A-B. Secondary guidewire 50B is deployed between two vascular access sites. The two vascular access sites typically include a second distal vascular access site 52D, which may be on a left axillary artery. For some applications, the second of the two vascular access sites is proximal vascular access site 52C, such as shown in Figs. 18B-O. Alternatively, the second of the two vascular access sites is distal vascular access site 52A, in which case secondary guidewire 50B may be deployed as described hereinabove with reference to Figs. 2D-N, with the optional substitution of second distal vascular access site 52D for second vascular access site 52B described with reference to Figs. 2D-N.

[0457] Secondary guidewire 50B may be deployed using techniques known in the art for deploying through-and-through guidewires. Secondary guidewire 50B may be introduced into and advanced within the vasculature in either direction. For example, secondary guidewire 50B may be introduced through a through-and-through catheter 260 deployed between the two vascular access sites. Alternatively, secondary guidewire 50B may be introduced using an introducer or access sheath (with or without a catheter) via either of the two vascular access sites, and then snared to bring the end portion of the secondary guidewire 50B to its target location in vasculature 54.

[0458] For other applications in which the method includes implanting second branching stent-graft 24B partially in third branch 73, elongate member 160A is secondary guidewire tube 140. Secondary guidewire 50B is inserted through the secondary-guidewire-tube lumen of secondary guidewire tube 140, and secondary guidewire tube 140 is removed, leaving secondary guidewire 50B, such as described hereinabove with reference to Figs. 6A-C. The steps of the method described hereinabove with reference to Figs. 6A-C may be performed (a) after deploying primary guidewire 50A and secondary guidewire 50B, and (b) before deploying main stent-graft 22 over primary guidewire 50A.

[0459] As shown in Fig. 18D-F, main stent-graft 22 is deployed over primary guidewire 50A at least partially in aortic arch 62. Typically, main stent-graft 22 is deployed by introducing main delivery catheter 80A and fixation tube 248 into vasculature 54 through proximal vascular access site 52C and advancing main delivery catheter 80A and fixation tube 248 over primary guidewire 50A (and secondary guidewire 50B, if provided) while, as shown in Fig. 15A:

[0460] • main stent-graft 222 is disposed within a portion of main delivery catheter 80A, such that main delivery catheter 80A constrains main stent-graft 222 in the radially- compressed delivery state such that distal main-fluid-flow guide end opening 27B faces distal catheter end 82 (main stent-graft 222 is typically disposed radially between main delivery catheter 80A and main inner shaft 78),

[0461] • sheath-rail guidewire 50C is removably positioned passing sequentially through (a) at least a portion of main delivery catheter 80A proximal to proximal main-fluid- flow guide end opening 27A, (b) proximal main-fluid-flow guide end opening 27A, (c) a longitudinal portion of main fluid flow lumen 29, (d) one of main-fluid-flow guide lateral openings 30 to outside main fluid flow lumen 29, and (e) distal catheter end 82,

[0462] • nosecone 86 is removably coupled to distal catheter end 82, and

[0463] • fixation tube 248 is disposed at least partially distal to nosecone 86, and • sheath-rail guidewire 50C is coupled to coupling site 250 on the external surface of fixation tube 248.

[0464] As shown in Fig. 18E, fixation tube 248, typically while in contact with nosecone 86, is distally advanced over primary guidewire 50A until a distal portion of fixation tube 248, which includes coupling site 250, exits vasculature 54 at distal vascular access site 52A. As a result, a distal end portion of sheath-rail guidewire 50C, which is coupled to coupling site 250, also exits vasculature 54 at distal vascular access site 52A.

[0465] As shown in Fig. 18G, main stent-graft 222 is transitioned to the radially-expanded deployment state at least partially in aortic arch 62, by deploying main stent-graft 222 from main delivery catheter 80A releasing main stent-graft 22 from the portion of main delivery catheter 80A. Main stent-graft 22 is typically released from main delivery catheter 80A by proximally withdrawing main delivery catheter 80A.

[0466] Nosecone 86 and main inner shaft 78 are proximally withdrawn from radially- expanded main stent-graft 222 and from vasculature 54 via proximal vascular access site 52C. In configurations in which fixation tube 248 is removably coupled to distal end portion 252 of main stent-graft 222, the fixation tube is decoupled from distal end portion 252, such as described hereinabove with reference to Fig. 17. Typically, fixation tube 248 and the one or more flexible elongated members 254 are held tight to ensure that the distal portion of main stent-graft 222 does not become dislodged from first branch 60 (e.g., BCT 64) during removal of nosecone 86 and main inner shaft 78 from the deployed main stentgraft 222.

[0467] In configurations in which secondary guidewire 50B is removably pre-positioned passing sequentially inter alia through proximal catheter end 83 and out of distal catheter end 82, during the advancing of main delivery catheter 80A over primary guidewire 50A and secondary guidewire 50B, main stent-graft 222 may slide distally over secondary guide wire 50B. Alternatively or additionally, main stent-graft 222 may remain axially stationary with respect to secondary guidewire 50B, in which case secondary guidewire 50B may move with delivery system 246 and may move distally out of a secondary access sheath at second distal vascular access site 52D (the secondary access sheath is used to introduce secondary guidewire 50B into vasculature 54, as known in the guidewire art).

[0468] For some applications, such as shown in Figs. 18F-G, a distal-most portion of main stent- graft 222 is deployed in first branch 60 of aortic arch 62. For example, first branch 60 may be BCT 64, such as shown. Alternatively, a distal-most portion of main stent-graft 222 is deployed in aortic arch 62 (configuration not shown).

[0469] Optionally, the steps of the deployment shown in Figs. 18D-G are implemented in combination with the techniques described hereinabove with reference to Figs. 9A-C and / or Figs. 12A-C, mutatis mutandis. Optionally, main stent-graft 222 comprises one or more internal support channels 120, such as described hereinabove with reference to Figs. 4A-C, 4D-F, 5, 6A-C, and 7, mutatis mutandis.

[0470] For some applications, delivery system 246 further comprises:

[0471] • an introducer sheath 262, which is configured to be introduced into vasculature 54 over sheath-rail guidewire 50C;

[0472] • a cannulating guidewire 50D; and / or

[0473] • a cannulating catheter 266, which is configured, while cannulating guidewire 50D is disposed at least partially within cannulating catheter 266, to be introduced into a proximal end of introducer sheath 262, and advanced through introducer sheath 262 and out of a distal end 270 of introducer sheath 262.

[0474] For example, a distal end portion of cannulating catheter 266 may have a predetermined curvature, which is selected to help with insertion of a distal end portion 264 of cannulating guidewire 50D into the branch from the main blood vessel. Cannulating catheters are also known in the art as angiographic catheters, diagnostic catheters, and vertebral catheters. By way of example and not limitation, appropriate cannulating catheters may include the Imager^M II Angiographic Catheter (Boston Scientific (Marlborough, MA, USA), Impress® Peripheral Angiographic Catheters (Merit Medical, South Jordan, UT, USA), and the Performa® Transradial Angiographic Catheter (Merit Medical).

[0475] Reference is again made to Fig. 18G. At the stage of deployment shown in Fig. 18G, sheath-rail guidewire 50C passes into vasculature 54 via proximal vascular access site 52C, through proximal catheter end 83 and into main stent-graft 222, out of one of main- fluid-flow guide lateral openings 30, and out of vasculature 54 via distal vascular access site 52A.

[0476] As shown in Fig. 18H, introducer sheath 262 is introduced into vasculature 54 over sheath-rail guidewire 50C via proximal vascular access site 52C, and is distally advanced over sheath-rail guidewire 50C until distal end 270 of introducer sheath 262 (a) is disposed within main stent-graft 222 within 1 cm of main-fluid- flow guide lateral opening 30 (e.g., flush with main-fluid-flow guide lateral opening 30), or (b) exits main-fluid-flow guide lateral opening 30. In applications in which main stent-graft 222 comprises internal support channel 120, distal end 270 of introducer sheath 262 typically (a) is disposed within channel lumen 129 of internal support channel 120 (labeled in Figs. 4A and 4D) (e.g., flush with main-fluid-flow guide lateral opening 30), or (b) exits main-fluid-flow guide lateral opening 30.

[0477] Optionally, a proximal end portion of introducer sheath 262 is temporarily clamped to sheath-rail guidewire 50C outside vasculature 54, and sheath-rail guidewire 50C is pulled distally from outside distal vascular access site 52 A in order to help advance introducer sheath 262 distally through vasculature 54.

[0478] As shown in Figs. 181- J, distal end portion 264 of cannulating guidewire 50D is advanced through introducer sheath 262 into a branch of the main blood vessel, such as second branch 70 of aortic arch 62; for example, second branch 70 may be LCCA 72, such as shown. Alternatively, the cannulating guidewire may be advanced into LSA 74 (configuration not shown). Typically, distal end portion 264 of cannulating guidewire 50D terminates in the vasculature, i.e., does not exit the body at a distal vascular access site using a through-and-through technique.

[0479] Optionally, as shown in Fig. 181, in order to assist with advancing cannulating guidewire 50D, cannulating catheter 266 is introduced into a proximal end of introducer sheath 262 (outside vasculature 54) and advanced through introducer sheath 262 alongside sheath-rail guidewire 50C, and out of distal end 270 of introducer sheath 262, while cannulating guidewire 50D is disposed at least partially within cannulating catheter 266; thus, cannulating guidewire 50D and cannulating catheter 266 are typically advanced together through the vasculature. Typically, as shown, sheath-rail guidewire 50C still passes through introducer sheath 262 as cannulating catheter 266 is advanced through introducer sheath 262. If introducer sheath 262 should inadvertently move during the advancement of cannulating catheter 266, sheath-rail guidewire 50C can be used to properly reposition introducer sheath 262.

[0480] It is noted that this deployment technique prevents sheath-rail guidewire 50C from becoming wrapped around any elements of delivery system 246 or main stent-graft 222. As shown in Fig. 18 J, distal end portion 264 of cannulating guidewire 50D is into the branch of the main blood vessel, typically while cannulating catheter 266 remains in the main blood vessel outside the branch (as shown), or is only slightly inserted into the branch (approach not shown).

[0481] As shown in Fig. 18K, cannulating catheter 266, if used, is withdrawn from introducer sheath 262, while leaving distal end portion 264 of cannulating guidewire 50D in the branch of the main blood vessel.

[0482] Also as shown in Fig. 18K, sheath-rail guidewire 50C is withdrawn from vasculature 54. For some applications, such as shown in Fig. 18K, sheath-rail guidewire 50C is withdrawn from vasculature 54 by decoupling sheath-rail guidewire 50C from fixation tube 248, and proximally withdrawing sheath-rail guidewire 50C from vasculature 54 via proximal vascular access site 52C.

[0483] Alternatively (configuration not shown), sheath-rail guidewire 50C is distally withdrawn from vasculature 54 via distal vascular access site 52A, either while coupled to coupling site 250 or after decoupling from coupling site 250. For example, a proximal end portion of sheath-rail guidewire 50C may be softer than a distal end portion of sheath-rail guidewire 50C that is coupled to coupling site 250 of fixation tube 248. (By contrast, in configurations in which sheath-rail guidewire 50C is proximally withdrawn from vasculature 54 via proximal vascular access site 52C, a distal end portion of sheath-rail guidewire 50C may optionally be softer than a proximal end portion of sheath-rail guide wire 50C.)

[0484] As shown in Fig. 18L, introducer sheath 262 is withdrawn from vasculature 54 via the proximal vascular access site 52C. This withdrawal may be performed after sheath-rail guidewire 50C has been withdrawn from vasculature 54, such as shown in the figures, or before sheath-rail guidewire 50C has been withdrawn from vasculature 54 (sequence not shown). Alternatively, in configurations in which introducer sheath 262 has a large enough diameter, branching extension stent-graft 36 is deployed through introducer sheath 262, and the introducer sheath is subsequently withdrawn.

[0485] As shown in Fig. 18N, branching extension stent-graft 36 is deployed through extension lateral opening 42 so as to form a blood-tight seal between main- stent-graft fluid flow guide 28 and branching-extension- stent- graft fluid flow guide 38. Although the deployment of branching extension stent-graft 36 is shown between the steps of Figs. 18M and 18N, branching extension stent-graft 36 may alternatively be deployed at any point between the steps of Figs. 18G and 18Q.

[0486] As shown in Figs. 18O-P, first and second branching stent-grafts 24A and 24B are deployed by advancing the branching stent-grafts over cannulating guidewire 50D and secondary guidewire 50B, respectively (or vice versa), (a) from proximal vascular access site 52C to within main stent-graft 22, (b) from within main stent-graft 22, and (c) partially into second branch 70 and third branch 73, respectively (or vice versa), via main-fluid-flow guide lateral openings 30. As a result, first and second branching stent-grafts 24A and 24B partially in second branch 70 and third branch 73, respectively (or vice versa), external to main-fluid-flow guide lateral openings 30 and partially inside main stent-graft 22, forming blood-tight seals between main- stent- graft fluid flow guide 28 and respective branching- stent-graft fluid flow guides 34. For example, above-described delivery system 46 may further comprise branching delivery catheters and branching inner shafts (not shown), which are shaped so as to define guidewire longitudinal lumens through which cannulating guidewire 50D and secondary guidewire 50B pass. First branching stent-graft 24A may be deployed before or after deploying branching stent-graft 24B .

[0487] As shown in Fig. 18Q, primary guidewire 50A, secondary guidewire 50B, and cannulating guidewire 50D are removed from vasculature 54, leaving vascular implant assembly 220 (including main stent-graft 222, first and second branching stent-grafts 24A and 24B, and branching extension stent-graft 36) implanted in vasculature 54.

[0488] Reference is again made to Figs. 18A-Q, in particular Figs. 18G-Q. The method described hereinabove with reference to these figures uses a retrograde approach. Alternatively, the method is implemented using an anterograde approach, such as described hereinabove with reference to Figs. 2E-M, in which internal support channels 120 extends in an opposite direction from that shown in Figs. 18G-Q, i.e., face distally (i.e., in a superior direction toward from the heart), rather than distally as shown for the retrograde approach. Further alternatively, the method is implemented with a retrograde approach for one branching stent-graft and an anterograde approach for the other branching stent-graft (configuration not shown).

[0489] In an application of the present invention, delivery system 246 comprises two sheath-rail guidewires 50C, which are configured and arranged as described hereinabove for the single sheath-rail guidewire 50C. The two sheath-rail guidewires 50C are used to introduce first and second branching stent-grafts 24A and 24B into first and second branching blood vessels, respectively. In this configuration, secondary guidewire 50B is typically not provided or used during the deployment procedure.

[0490] Reference is now made to Figs. 19A and 19B, which are schematic illustrations of another configuration of main stent-graft 222 disposed in a radially-compressed delivery state within a portion of main delivery catheter 80A, in accordance with an application of the present invention. Fig. 19B is a top- view, not shown to scale. (For clarity of illustration, main stent-graft 222 is shown slightly expanded in Figs. 19A-B, even though it is in practice generally more radially-compressed when in this delivery state.)

[0491] For some applications, stent-graft system 244 comprises delivery system 246 and vascular implant assembly 220, which comprises the configuration of main stent-graft 222 shown in Figs. 19A-B.

[0492] In the configuration shown in Figs. 19A and 19B, main stent-graft 222, vascular implant assembly 220, stent-graft system 224, and delivery system 246 differ from the configurations of these elements described hereinabove with reference to Figs. 13A-B, 14, 15A-B, 16, and 17 in the following respects:

[0493] • main stent-graft 222 comprises only a single main-fluid-flow guide lateral opening 30, similar to main stent-graft 22 described hereinabove with reference to Figs. 1 A- D;

[0494] • implant assembly 220 comprises only a single branching stent-graft 24, similar to configuration described hereinabove with reference to Figs. 1A-D; and

[0495] • delivery system 246 does not comprise secondary guidewire 50B.

[0496] Other than these differences, the configurations of main stent-graft 222, vascular implant assembly 220, stent-graft system 224, and delivery system 246 described with reference to Figs. 19A and 19B may implement any of the other features of these elements described hereinabove.

[0497] Reference is further made to Figs. 20A-H, which are schematic illustrations of several stages of a method for deploying one or more vascular implants, in accordance with an application of the present invention. Other than as described below, the method of Figs. 20A-H is generally similar to the method described hereinabove with reference to Figs. 18A-Q, and may be implemented using any of the techniques described with reference to Figs. 18A-Q and / or any of the other deployment methods and other techniques described herein.

[0498] The method of Figs. 20A-H includes the steps of the method described hereinabove with reference to Figs. 18A and 18D-F, omitting the steps described hereinabove with reference to Figs. 18B-C, which relate to deployment of secondary guidewire 50B, which, as described above with reference to Figs. 19A-B, is not provided in the present configuration.

[0499] The steps of the method of Figs. 20A-H are otherwise similar to the steps of the method described hereinabove with reference to Figs. 18G-O, mutatis mutandis, with the omission of the steps relating to secondary guidewire 50B and second branching stent-graft 24B, which are not provided in the present configuration.

[0500] Figs. 20A-H show the deployment of branching stent-graft 24 in LCCA 72 by way of example; branching stent-graft 24 may alternatively be deployed in LSA 74 using the same techniques.

[0501] Reference is now made to Figs. 21A-B, which are schematic illustrations of a portion of a stent-graft system 324 comprising a stent-graft 322, shown in a radially- compressed delivery state and in a partially radially-expanded deployment state, respectively, in accordance with an application of the present invention. Optionally, the features of stent-graft 322 are implemented in any of the stent-grafts described herein. Alternatively, the features of stent-graft 322 are implemented in a stent-graft other than the stent-grafts described herein.

[0502] Stent-graft 322 comprises a fluid flow guide 328 and a stent 326. Stent 326 comprises:

[0503] • cylindrical undulating rings 330, which are coupled to fluid flow guide 328 at respective axial locations 332 along an axis 334 of fluid flow guide 328, so as to provide a tubular shape to fluid flow guide 328 about axis 334 when stent-graft 322 is in a radially-expanded deployment state, such as shown for a portion of stentgraft 322 in Fig. 21B; cylindrical undulating rings 330 comprise first and second cylindrical undulating rings 33OA and 33OB; and

[0504] • spring links 336, which are joined to first and second cylindrical undulating rings 33OA and 33OB, respectively. For example, spring links 336 may be joined to respective peaks or valleys of first and second cylindrical undulating rings 33OA and 33OB, such as shown. Alternatively, spring links 336 may be joined to other respective locations of first and second cylindrical undulating rings 330A and 33OB (configurations not shown).

[0505] For some applications, spring links 336 are joined to first and second cylindrical undulating rings 33OA and 33OB such that spring links 336 are oriented axially along stentgraft 322, such as shown.

[0506] Optionally, respective first and second ends 338A and 338B of spring links 336 are joined to first and second cylindrical undulating rings 33OA and 33OB, respectively, such as shown. Alternatively, one or more non-end portions of spring links 336 are joined to first and second cylindrical undulating rings 33OA and 33OB, respectively (configurations not shown).

[0507] For example, cylindrical undulating rings 330 may be coupled to fluid flow guide 328 by suturing or stitching. Fluid flow guide 328 covers at least a portion of cylindrical undulating rings 330. Cylindrical undulating rings 330 may be attached to an internal surface and / or an external surface of fluid flow guide 328. Optionally, a portion of cylindrical undulating rings 330 may be attached (e.g., sutured) to the internal surface, and another portion to the external surface. (It will be appreciated that each of axial locations 332 is not disposed at a single point along axis 334, but instead has an axial length equal to the height (i.e., axial length) of the undulations of cylindrical undulating rings 330, measured along axis 334.)

[0508] For some applications, stent 326 comprises two sets of first and second cylindrical undulating rings 33OA and 33OB. In these applications, stent 326 may comprise two sets of spring links 336, which are respectively joined to the two sets of rings, or the spring links of a single set of spring links may connect three or more undulating rings 330A (configurations not shown). For some of these applications, both first cylindrical undulating rings 33OA are located closer to respective ends of fluid flow guide 328 than are any of the other cylindrical undulating rings 330 (configuration not shown).

[0509] Stent-graft system 324 further comprises a delivery system 346, which comprises a delivery catheter 380. (Delivery system 346 typically further comprises additional elements, such as a control handle.) As shown in Fig. 21 A, stent-graft 322 is removably disposed within a portion of delivery catheter 380 such that delivery catheter 380 constrains stent-graft 322 in the radially-compressed delivery state (sometimes referred to in the art as a crimped state). For clarity of illustration, the entirety of stent-graft 322 is shown in Fig. 21A in the radially-compressed state less radially compressed than in typical actual practice, and the radially-compressed portion of stent-graft 322 is shown in Fig. 2 IB in the radially- compressed state less radially compressed than in typical actual practice.

[0510] When stent-graft 322 is in the radially-compressed delivery state, such as shown in Fig. 21 A:

[0511] • spring links 336 are in respective extended tensioned states, and

[0512] • first and second cylindrical undulating rings 33OA and 330B do not axially overlap with each other; in other words, first and second cylindrical undulating rings 33OA and 330B are not disposed at any common axial locations along stent-graft 322.

[0513] This lack of axial overlap allows the radial compression of stent-graft 322 into a smaller-diameter delivery catheter 380 than would be possible if first and second cylindrical undulating rings 330A and 33OB axially overlapped.

[0514] For some applications, such as shown in Fig. 21 A, when stent-graft 322 is in the radially-compressed delivery state and spring links 336 are in the respective extended tensioned states, first and second cylindrical undulating rings 330A and 33OB are disposed along stent-graft 322 so as to define an axial gap 340 between first and second cylindrical undulating rings 33OA and 33OB. For example, axial gap 340 may have a length L of at least 0.1 mm, no more than 5 mm, and / or 0.1 - 5 mm, measured parallel to axis 334.

[0515] For other applications, when stent-graft 322 is in the radially -compressed delivery state and spring links 336 are in the respective extended tensioned states, first and second cylindrical undulating rings 33OA and 330B axially border each other, i.e., are axially directly adjacent each other such that the rings axially terminate at the same axial location, without axially overlapping or defining a gap therebetween (configuration not shown).

[0516] When spring links 336 are in the respective extended tensioned states, first and second cylindrical undulating rings 330A and 33OB are at an extended axial offset DI from each other, measured parallel to axis 334, as labeled in Fig. 21A. For example, extended axial offset DI may be measured between respective peaks of first and second cylindrical undulating rings 33OA and 330B, or between respective valleys of first and second cylindrical undulating rings 330A and 330B. For some applications, stent-graft 322 is removably disposed within the portion of delivery catheter 380 such that delivery catheter 380 constrains stent-graft 322 in the radially-compressed delivery state in which:

[0517] • friction between first and second cylindrical undulating rings 33OA and 33OB and an inner wall of delivery catheter 380 helps hold spring links 336 in the respective extended tensioned states, and / or

[0518] • fluid flow guide 328 helps hold spring links 336 in the respective extended tensioned states.

[0519] Optionally, delivery system 346 comprises a mechanism that holds stent-graft 322 in tension inside delivery catheter 380. The mechanism has a release function or controlled release when desired.

[0520] For some applications, such as shown in Figs. 21A-B, spring links 336 are shaped so define respective undulations falling generally in respective planes. For other applications, spring links 336 are helical or have another shape (configurations not shown).

[0521] As shown in the transition between Fig. 21 A and Fig. 2 IB, stent-graft 322 is configured such that upon release of spring links 336 from delivery catheter 380, spring links 336 shorten as they transition toward respective resting states. This shortening of spring links 336 approximates (i.e., brings closer together) first and second cylindrical undulating rings 330A and 33OB, typically such that the rings:

[0522] (a) axially overlap with each other, i.e., at least an axial portion of first cylindrical undulating ring 33OA and at least an axial portion of second cylindrical undulating ring 33OB share a common axial location along stent-graft 322, such as shown in Fig. 2 IB; in this axially-overlapping state, first and second cylindrical undulating rings 33OA and 33OB may also be considered to be axially nested with each other,

[0523] (b) axially border each other, i.e., are axially directly adjacent each other such that the rings axially terminate at the same axial location, without axially overlapping or defining a gap therebetween (configuration not shown, or

[0524] (c) define an axial gap between each other, the axial gap typically having a length less than 50%, such as less than 30%, of an average height H of undulations of the first and the second cylindrical undulating rings, the length and the average height H measured parallel to the axis when the stent-graft is in the radially-expanded deployment state (configuration not shown).

[0525] This approximation of first and second cylindrical undulating rings 33OA and 33OB may offer a shorter landing (sealing) zone with the vascular wall than if the rings were axially farther apart. The approximation provides a shorter sealing zone and a better seal with the wall of the blood vessel, due to the increased outwardly-directed radial force over the shortened landing zone, i.e., the greater radial force per length.

[0526] For some applications, such as shown in Fig. 2 IB, the shortening of spring links 336 as they transition toward the respective resting states approximates first and second cylindrical undulating rings 33OA and 33OB such that the rings bunch up (i.e., gather into one or more folds) a portion 382 of fluid flow guide 328 axially between first and second axial locations 332A and 332B at which first and second cylindrical undulating rings 33OA and 33 OB are coupled to fluid flow guide 328. The fabric (graft material) of fluid flow guide 328 is typically quite thin (e.g., has a thickness of about 0.075 mm) and does not interfere with the seal between rings 330A and 330B and the landing zone within the blood vessel, even if the fabric somewhat overlaps the rings.

[0527] As mentioned above, when spring links 336 are in the respective extended tensioned states, first and second cylindrical undulating rings 330A and 33OB are at the extended axial offset DI from each other, measured parallel to axis 334, as labeled in Fig. 21A. Stentgraft 322 is configured such that upon the release of spring links 336 from the delivery catheter, spring links 336 shorten as they transition toward the respective resting states, thereby approximating first and second cylindrical undulating rings 33OA and 33OB such that first and second cylindrical undulating rings 33OA are at an approximated axial offset D2 from each other, measured parallel to axis 334, as labeled in Fig. 21B. For example, approximated axial offset D2 may be measured between respective peaks of first and second cylindrical undulating rings 33OA and 33OB, or between respective valleys of first and second cylindrical undulating rings 33OA and 330B.

[0528] For some applications, stent-graft 322 is configured such that upon the release of spring links 336 from delivery catheter 380, spring links 336 shorten as they transition toward the respective resting states, thereby approximating first and second cylindrical undulating rings 33OA and 33OB such that first and second cylindrical undulating rings 33OA and 33OB axially overlap each other by an overlap length O measured parallel to axis 334. The overlap length O typically equals at least 1%, no more than 80%, and / or 1% - 80% of the average height H of undulations of first and second cylindrical undulating rings 33OA and 33OB, measured along axis 334 when stent-graft 322 is in the radially-expanded deployment state, e.g., at least 5%, no more than 80%, and / or 5% - 80%, such as at least 15%, no more than 50%, and / or 15% - 50%, e.g., at least 25%, no more than 40%, and / or 25% - 40%, of the average heigh H of the undulations.

[0529] Alternatively or additionally, for some applications, stent-graft 322 is configured such:

[0530] • the approximated axial offset D2 equals at least 30%, no more than 70% and / or 30% - 70% of the extended axial offset DI,

[0531] • the approximated axial offset D2 equals at least 4.5 mm, no more than 10.5 mm, and / or 4.5 - 10.5 mm less than the extended axial offset DI,

[0532] • a difference between the approximated axial offset D2 and the extended axial offset DI equals at least 40%, no more than 80%, and / or 40% - 80% of the average height H of the undulations of first and second cylindrical undulating rings 33OA and 33OB, measured along axis 334 when stent-graft 322 is unconstrained in the radially- expanded deployment state, and / or

[0533] • the difference between the approximated axial offset D2 and the extended axial offset DI equals at least 5%, no more than 35%, and / or 5% - 35% of an average diameter D3 of first and second cylindrical undulating rings 33OA and 33OB when stent-graft 322 is unconstrained in the radially-expanded deployment state.

[0534] Typically, cylindrical undulating rings 330 are self-expandable (and are biased toward the radially-expanded deployment state), though they may alternatively be balloonexpandable. For example, cylindrical undulating rings 330 may comprise a metal, such as a superelastic metal alloy, a shape memory metallic alloy, and / or Nitinol; alternatively, the metal may comprise stainless steel.

[0535] For some applications, spring links 336 comprise a metal, such as a superelastic metal alloy, a shape memory metallic alloy, Nitinol, spring stainless steel, or titanium; or a polymer, such as silicone, Polyether Ether Ketone (PEEK), Polyetherimide (PEI), Poly ether Block Amide (PEBA), or Polyurethane (PU).

[0536] For some applications, spring links 336 are fabricated as separate pieces from first and second cylindrical undulating rings 33OA and 33OB, and are coupled to first and second cylindrical undulating rings 330A and 33OB, such as by suturing (as shown) or soldering (configuration not shown). Optionally, each of spring links 336 comprise one or two eyelets that are coupled to first and second cylindrical undulating rings 33OA and 33OB, respectively, such as shown.

[0537] For some applications, spring links 336 and first and second cylindrical undulating rings 33OA and 33OB are fabricated integrally from a single piece of material, e.g., laser cut from a single metal tube. Optionally, a cross-sectional area of spring links 336 is less than a cross-sectional area of cylindrical undulating rings 330; for example, or a width of spring links 336 may be less than a wall thickness and / or a width of cylindrical undulating rings 330.

[0538] Optionally, regardless of how the spring links and cylindrical undulating rings are fabricated, a cross-sectional area of spring links 336 is less than a cross-sectional area of cylindrical undulating rings 330. For example, a wall thickness and / or a width of spring links 336 may be less than a wall thickness and / or a width of cylindrical undulating rings 330.

[0539] Optionally, spring links 336 are more elastic than cylindrical undulating rings 330.

[0540] Optionally, spring links 336 are more extensible than cylindrical undulating rings 330.

[0541] Optionally, spring links 336 are more springy than cylindrical undulating rings 330.

[0542] Fluid flow guide 328 may comprise at least one piece of biologically-compatible substantially blood-impervious fabric. The fabric may comprise, for example, a polyester, a polyethylene (e.g., a poly-ethylene-terephthalate), a polymeric film material (e.g., polytetrafluoroethylene (PTFE), polypropylene, polyethylene, high-density polyethylene, polyurethane, polyolefins, ePTFE), a polymeric textile material (e.g., woven polyethylene terephthalate (PET)), natural tissue graft (e.g., saphenous vein or collagen), or a combination thereof. The fabric may be non-elastic (such as illustrated) or elastic (configuration not shown).

[0543] In some applications of the present invention, a method is provided that comprises introducing delivery catheter 380 into a blood vessel of patient and advancing delivery catheter 380 to a target location in the blood vessel while stent-graft 322 is removably disposed within the portion of delivery catheter 380 such that delivery catheter 380 constrains stent-graft 322 in the radially-compressed delivery state described hereinabove with reference to Fig. 21 A. Stent-graft 322 is transitioned to the radially-expanded deployment state by deploying stent- graft 322 from delivery catheter 380, such that cylindrical undulating rings 330 provide a tubular shape to fluid flow guide 328 about axis 334. Stent-graft 322 is configured such that upon release of spring links 336 from delivery catheter 380 upon the deploying stent-graft 322 from delivery catheter 380, spring links 336 shorten as they transition toward respective resting states, thereby approximating first and second cylindrical undulating rings 33OA and 330B.

[0544] In an embodiment, techniques and apparatus described in one or more of the following applications, which are incorporated herein by reference, are combined with techniques and apparatus described herein:

[0545] • US Patent 8,317,856 to Benary et al.

[0546] • US Patent 8,870,938 to Shalev et al.

[0547] • US Patent 8,945,203 to Shalev et al.

[0548] • US Patent 9,993,360 to Shalev et al.

[0549] • US Patent 9,668,892 to Shalev

[0550] • US Patent Application Publication 2016 / 0193029 to Shalev

[0551] • US Patent 10,603,197 to Marmur et al.

[0552] • US Patent 10,485,684 to Marmur et al.

[0553] • US Provisional Patent Application 63 / 406,955, filed September 15, 2022

[0554] • PCT Publication WO 2024 / 057320 to Avisar et al.

[0555] • US Provisional Patent Application 63 / 567,652, filed March 20, 2024

[0556] • US Provisional Patent Application 63 / 643,063, filed May 6, 2024

[0557] • US Provisional Patent Application 63 / 695,067, filed September 16, 2024,

[0558] It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

CLAIMS1. A stent-graft system for use with a primary guidewire, the stent-graft system comprising:(i) a main stent-graft, which (a) is configured to be deployed over the primary guidewire, (b) is configured to assume a radially-compressed delivery state and a radially- expanded deployment state, and (c) comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which is (1) securely attached to and covers at least a portion of the main- stent- graft stent member, and (2) shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; and(ii) a delivery system, which comprises:(a) a main delivery catheter having proximal and distal catheter ends, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that the distal main-fluid-flow guide end opening faces the distal catheter end;(b) a sheath-rail guidewire, which is removably positioned passing sequentially through (1) at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (2) the proximal main-fluid-flow guide end opening, (3) a longitudinal portion of the main fluid flow lumen, (4) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (5) the distal catheter end;(c) a nosecone removably coupled to the distal catheter end; and(d) a fixation tube, disposed at least partially distal to the nosecone, wherein the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube.

2. The stent-graft system according to claim 1, wherein the fixation tube is removably coupled to a distal end portion of the main stent-graft.

3. The stent- graft system according to claim 1, wherein the fixation tube is axially moveable away from the nosecone.

4. The stent-graft system according to claim 1, wherein the fixation tube is removably in contact with a distal end portion of the nosecone.

5. The stent-graft system according to claim 1, for use with a primary guidewire, wherein the fixation tube is shaped so as to define a lumen for insertion therethrough of the primary guidewire.

6. The stent- graft system according to claim 1, wherein the delivery system further comprises a main inner shaft, which is removably disposed at least partially within the main delivery catheter, and wherein the nosecone and the main inner shaft are shaped so as to define respective guidewire longitudinal lumens for insertion therethrough of the primary guidewire.

7. The stent-graft system according to claim 1 , wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

8. The stent-graft system according to claim 1 , wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

9. The stent-graft system according to any one of claims 1-8, wherein the delivery system further comprises an introducer sheath, which is configured to be introduced into vasculature of a patient over the sheath-rail guidewire.

10. The stent-graft system according to claim 9, wherein the delivery system further comprises a cannulating guidewire.

11. The stent-graft system according to claim 10, wherein the delivery system further comprises a cannulating catheter, which is configured, while the cannulating guidewire is disposed at least partially within the cannulating catheter, to be introduced into a proximal end of the introducer sheath, and advanced through the introducer sheath and out of a distal end of the introducer sheath.

12. The stent-graft system according to any one of claims 1-8, wherein the stent-graft system further comprises a branching stent-graft, which: comprises a flexible branching-stent-graft stent member and a generally tubular branching- stent-graft fluid flow guide, and is configured to be disposed through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between the branching-stent-graft fluid flow guide and a portion of the main- stent- graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

13. The stent-graft system according to any one of claims 1-8, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, the at least a portion of the main delivery catheter is at least a first portion of the main delivery catheter, and the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein the main fluid flow guide is shaped so as to further define a second main- fluid-flow guide lateral opening, and wherein the delivery system further comprises: an elongate member, which is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end.

14. The stent-graft system according to claim 13, for use with a secondary guidewire, wherein the elongate member comprises a secondary guidewire tube, which is shaped so as to define a secondary-guidewire-tube lumen for insertion therethrough of the secondary guide wire.

15. The stent-graft system according to claim 13, wherein the elongate member comprises a secondary guidewire.

16. The stent-graft system according to claim 13, wherein the stent-graft system further comprises first and second branching stentgrafts, which comprise first and second flexible branching-stent-graft stent members and first and second generally tubular branching-stent-graft fluid flow guides, respectively, wherein the first branching stent-graft is configured to be disposed through the first main-fluid-flow guide lateral opening so as to form a blood-tight seal between the first branching- stent-graft fluid flow guide and a first portion of the main- stent- graft fluid flow guide that defines a first perimeter of the first main-fluid-flow guide lateral opening, and wherein the second branching stent-graft is configured to be disposed through the second main-fluid-flow guide lateral opening so as to form a blood-tight seal between the second branching-stent-graft fluid flow guide and a second portion of the main-stent-graft fluid flow guide that defines a second perimeter of the second main-fluid-flow guide lateral opening.

17. A method comprising: providing a main stent-graft, which is configured to assume a radially-compressed delivery state and a radially-expanded deployment state, and which comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main-stent-graft stent member, and (b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; deploying a primary guidewire into vasculature of a patient between proximal and distal vascular access sites; introducing a main delivery catheter and a fixation tube over the primary guidewire into a main blood vessel via the proximal vascular access site, while: the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that the distal main-fluid-flow guide end opening faces the distal catheter end, a sheath-rail guidewire is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end, a nosecone is removably coupled to the distal catheter end, a fixation tube is disposed at least partially distal to the nosecone, and the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube; transitioning the main stent-graft to the radially-expanded deployment state by deploying the main stent-graft from the main delivery catheter; introducing an introducer sheath into the vasculature over the sheath-rail guidewire via the proximal vascular access site; distally advancing the introducer sheath over the sheath-rail guidewire until a distal end of the introducer sheath (a) is disposed within the main stent-graft within 1 cm of the main-fluid-flow guide lateral opening, or (b) exits the main-fluid-flow guide lateral opening;advancing a distal end portion of a cannulating guidewire through the introducer sheath and into a branch of the main blood vessel; advancing a branching stent-graft over the cannulating guidewire (a) from the proximal vascular access site to within the main stent-graft and (b) out of the main-fluid- flow guide lateral opening; disposing the branching stent-graft through the main-fluid-flow guide lateral opening so as to form a blood-tight seal between (a) a branching-stent-graft fluid flow guide of the branching stent-graft and (b) a portion of the main-stent-graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening; and before or after advancing the branching stent-graft over the cannulating guidewire, withdrawing the introducer sheath from the vasculature via the proximal vascular access site.

18. A stent-graft system for use with a primary guidewire, the stent- graft system comprising:(i) a main stent- graft, which (1) is configured to be deployed over the primary guidewire, (2) is configured to assume a radially-compressed delivery state and a radially- expanded deployment state, and (3) comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main- stent- graft stent member, and (b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; and(ii) a delivery system, which comprises:(A) a main delivery catheter having proximal and distal catheter ends, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that (a) the distal main-fluid-flow guide end opening faces the distal catheter end, and (b) the main-fluid-flow guide lateral opening is at a first angular location with respect to a central longitudinal axis of the main delivery catheter; and(B) an elongate member, which is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) themain-fluid-flow guide lateral opening, at the first angular location, to outside the main fluid flow lumen, and (e) the distal catheter end, wherein the elongate member exits the distal catheter end at a second angular location with respect to the central longitudinal axis of the main delivery catheter, the second angular location offset from the first angular location around the central longitudinal axis by at least 90 degrees.

19. The stent- graft system according to claim 18, wherein the second angular location is offset from the first angular location around the central longitudinal axis by at least 135 degrees.

20. The stent- graft system according to claim 18, wherein the main delivery catheter is shaped so as to define a distal curved portion that causes the main delivery catheter to automatically rotationally orient itself.

21. The stent-graft system according to claim 18, further comprising a nosecone removably coupled to the distal catheter end.

22. The stent-graft system according to claim 18, wherein the elongate member wraps around the main stent-graft from the first angular location to the second angular location in a single direction around the main stent-graft.

23. The stent-graft system according to claim 18, wherein the elongate member wraps around the main stent-graft from the first angular location to the second angular location in less than one turn around the main stent-graft.

24. The stent-graft system according to claim 18, wherein the elongate member is removably positioned passing sequentially through (a) the proximal catheter end, (b) the at least a longitudinal portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (c) the proximal main-fluid-flow guide end opening, (d) the longitudinal portion of the main fluid flow lumen, (e) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (f) the distal catheter end.

25. The stent-graft system according to any one of claims 18-24, for use with a secondary guidewire, wherein the elongate member comprises a secondary guidewire tube, which is shaped so as to define a secondary-guidewire -tube lumen for insertion therethrough of the secondary guidewire.

26. The stent-graft system according to any one of claims 18-24, wherein the elongate member comprises a secondary guidewire.

27. The stent- graft system according to any one of claims 18-24, wherein the delivery system further comprises a main inner shaft, which is removably disposed at least partially within the main delivery catheter, and is shaped so as to define a guidewire longitudinal lumen for insertion therethrough of the primary guidewire.

28. The stent- graft system according to any one of claims 18-24, wherein the main stent-graft further comprises an internal support channel, which (a) is configured to assume expanded and collapsed states, (b) is disposed within the main fluid flow guide, and (c) comprises a generally tubular channel fluid flow guide, which is shaped so as to define (1) proximal and distal channel-fluid-flow end openings and (2) when the internal support channel is in the expanded state, a channel lumen between the proximal and the distal channel-fluid-flow end openings, wherein:(A) when the internal support channel is in the collapsed state, the distal channel-fluid-flow guide end opening faces radially inward, and(B) when the internal support channel is in the expanded state and the main stent-graft is in the radially-expanded deployment state, the distal channelfluid-flow guide end opening faces at least partially distally within the main fluid flow guide, wherein the proximal channel-fluid-flow end opening is sealingly coupled to a perimeter of the main-fluid-flow guide lateral opening, such that the channel lumen is in fluid communication with outside the main fluid flow guide via the main-fluid-flow guide lateral opening when the internal support channel is in the expanded state, wherein the elongate member is removably positioned passing sequentially through (a) the at least a portion of the main delivery catheter proximal to the proximal main-fluid- flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) the longitudinal portion of the main fluid flow lumen, (d) the distal channel-fluid-flow guide end opening, (e) the main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (f) the distal catheter end, wherein the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state with the distal main-fluid-flow guide end opening facingthe distal catheter end, thereby constraining the internal support channel in the collapsed state, and wherein the internal support channel is configured to automatically transition to the expanded state when not constrained in the collapsed state by the main stent-graft and not constrained in the collapsed state by the elongate member.

29. The stent- graft system according to claim 28, wherein the internal support channel further comprises a flexible channel stent member to which the channel fluid flow guide is securely attached.

30. The stent- graft system according to any one of claims 18-24, wherein the stent-graft system further comprises a branching stent-graft, which comprises a flexible branchin -stent-graft stent member and a generally tubular branchingstent-graft fluid flow guide, and wherein the branching stent-graft is configured to be disposed through the main- fluid-flow guide lateral opening so as to form a blood-tight seal between the branchingstent-graft fluid flow guide and a portion of the main- stent- graft fluid flow guide that defines a perimeter of the main-fluid-flow guide lateral opening.

31. The stent-graft system according to any one of claims 18-24, wherein the main-fluid-flow guide lateral opening is a first main-fluid-flow guide lateral opening, wherein the at least a portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening is at least a first portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, wherein the longitudinal portion of the main fluid flow lumen is a first longitudinal portion of the main fluid flow lumen, wherein main fluid flow guide of the main stent-graft is shaped so as to further define a second main-fluid-flow guide lateral opening, and wherein the delivery system further comprises a sheath-rail guidewire, which is removably positioned passing sequentially through (a) at least a second portion of the main delivery catheter proximal to the proximal main-fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a second longitudinal portion of the main fluid flow lumen, (d) the second main-fluid-flow guide lateral opening to outside the main fluid flow lumen, and (e) the distal catheter end.

32. The stent-graft system according to claim 31, wherein the delivery system further comprises: a nosecone removably coupled to the distal catheter end; and a fixation tube, disposed at least partially distal to the nosecone, wherein the sheath-rail guidewire is coupled to a coupling site on an external surface of the fixation tube.

33. The stent-graft system according to claim 32, wherein the fixation tube is removably coupled to a distal end portion of the main stent-graft.

34. The stent-graft system according to claim 32, wherein the fixation tube is axially moveable away from the nosecone.

35. The stent-graft system according to claim 32, for use with a primary guidewire, wherein the fixation tube is shaped so as to define a lumen for insertion therethrough of the primary guidewire.

36. The stent-graft system according to claim 32, wherein the coupling site is at a distance of at least 30 cm from a proximal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

37. The stent-graft system according to claim 32, wherein the coupling site is at a distance of no more than 5 cm from a distal end of the fixation tube, the distance measured along a central longitudinal axis of the fixation tube.

38. The stent-graft system according to claim 32, wherein the delivery system further comprises an introducer sheath, which is configured to be introduced into vasculature of a patient over the sheath-rail guidewire.

39. The stent-graft system according to claim 38, wherein the delivery system further comprises a cannulating guidewire.

40. The stent-graft system according to claim 39, wherein the delivery system further comprises a cannulating catheter, which is configured, while the cannulating guidewire is disposed at least partially within the cannulating catheter, to be introduced into a proximal end of the introducer sheath, and advanced through the introducer sheath and out of a distal end of the introducer sheath.

41. The stent- graft system according to claim 31, wherein the sheath -rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinalaxis of the main delivery catheter, the third angular location offset from the second angular location around the central longitudinal axis by at least 90 degrees.

42. The stent-graft system according to claim 41, wherein the third angular location is offset from the second angular location around the central longitudinal axis by at least 135 degrees.

43. The stent- graft system according to claim 31, wherein the sheath -rail guidewire exits the distal catheter end at a third angular location with respect to the central longitudinal axis of the main delivery catheter, the third angular location either (a) at the first angular location around the central longitudinal axis, or (b) offset from the first angular location around the central longitudinal axis by less than 90 degrees.

44. The stent-graft system according to claim 43, wherein the third angular location is offset from the first angular location around the central longitudinal axis by less than 45 degrees.

45. The stent- graft system according to claim 31, wherein the stent-graft system further comprises first and second branching stentgrafts, which comprise first and second flexible branching-stent-graft stent members and first and second generally tubular branching-stent-graft fluid flow guides, respectively, wherein the first branching stent-graft is configured to be disposed through the first main-fluid-flow guide lateral opening so as to form a blood-tight seal between the first branching- stent-graft fluid flow guide and a first portion of the main- stent- graft fluid flow guide that defines a first perimeter of the first main-fluid-flow guide lateral opening, and wherein the second branching stent-graft is configured to be disposed through the second main-fluid-flow guide lateral opening so as to form a blood-tight seal between the second branching-stent-graft fluid flow guide and a second portion of the main-stent-graft fluid flow guide that defines a second perimeter of the second main-fluid-flow guide lateral opening.

46. A method comprising: providing a main stent-graft, which is configured to assume a radially-compressed delivery state and a radially-expanded deployment state, and which comprises a flexible main-stent-graft stent member and a generally tubular main fluid flow guide, which (a) is securely attached to and covers at least a portion of the main-stent-graft stent member, and(b) is shaped so as to define proximal and distal main-fluid-flow guide end openings, a main fluid flow lumen therebetween, and a main-fluid-flow guide lateral opening; deploying a primary guidewire into vasculature of a patient; introducing, over the primary guidewire, a main delivery catheter, having proximal and distal catheter ends, into the vasculature while: the main stent-graft is removably disposed within a portion of the main delivery catheter such that the main delivery catheter constrains the main stent-graft in the radially-compressed delivery state such that (a) the distal main-fluid-flow guide end opening faces the distal catheter end, and (b) the main-fluid-flow guide lateral opening is at a first angular location with respect to a central longitudinal axis of the main delivery catheter, and an elongate member is removably positioned passing sequentially through (a) at least a portion of the main delivery catheter proximal to the proximal main- fluid-flow guide end opening, (b) the proximal main-fluid-flow guide end opening, (c) a longitudinal portion of the main fluid flow lumen, (d) the main-fluid-flow guide lateral opening, at the first angular location, to outside the main fluid flow lumen, and (e) the distal catheter end, and the elongate member exits the distal catheter end at a second angular location with respect to the central longitudinal axis of the main delivery catheter, the second angular location offset from the first angular location around the central longitudinal axis by at least 90 degrees; and thereafter, transitioning the main stent-graft to the radially-expanded deployment state by deploying the main stent-graft from the main delivery catheter.

47. A stent-graft system comprising:(i) a stent-graft comprising (a) a fluid flow guide and (b) a stent, which comprises: cylindrical undulating rings, which are coupled to the fluid flow guide at respective axial locations along an axis of the fluid flow guide, so as to provide a tubular shape to the fluid flow guide about the axis when the stent-graft is in a radially-expanded deployment state, and which comprise first and second cylindrical undulating rings; and spring links, which are joined to the first and the second cylindrical undulating rings,(ii) a delivery system, which comprises a delivery catheter, wherein the stent-graft is removably disposed within a portion of the delivery catheter such that the delivery catheter constrains the stent-graft in a radially-compressed delivery state in which (a) the spring links are in respective extended tensioned states, and (b) the first and the second cylindrical undulating rings do not axially overlap with each other, and wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings.

48. The stent-graft system according to claim 47, wherein the stent- graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings bunch up a portion of the fluid flow guide axially between first and second axial locations at which the first and the second cylindrical undulating rings are coupled to the fluid flow guide.

49. The stent-graft system according to claim 47, wherein the spring links are joined to the first and the second cylindrical undulating rings such that the spring links are oriented axially along the stent-graft.

50. The stent-graft system according to claim 47, wherein the spring links have respective first and second ends that are coupled to the first and the second cylindrical undulating rings, respectively.

51. The stent-graft system according to claim 47, wherein the spring links are shaped so define respective undulations falling generally in respective planes.

52. The stent-graft system according to claim 47, wherein the spring links are helical.

53. The stent-graft system according to claim 47, wherein the stent comprises at least three of the cylindrical undulating rings in addition to the first and the second cylindrical undulating rings.

54. The stent-graft system according to claim 53, wherein the first cylindrical undulating ring is located closer to an end of the fluid flow guide than are any of the other cylindrical undulating rings.

55. The stent-graft system according to claim 47, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 30% - 70% of the extended axial offset.

56. The stent-graft system according to claim 47, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein the approximated axial offset equals 4.5 - 10.5 mm less than the extended axial offset.

57. The stent- graft system according to claim 47, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axialoffset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 40% - 80% of an average height of undulations of the first and the second cylindrical undulating rings, measured along the axis when the stent-graft is in the radially- expanded deployment state.

58. The stent-graft system according to claim 47, wherein when the spring links are in the respective extended tensioned states, the first and the second cylindrical undulating rings are at an extended axial offset from each other, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings are at an approximated axial offset from each other, the extended axial offset and the approximated axial offset measured parallel to the axis, and wherein a difference between the approximated axial offset and the extended axial offset equals 5% - 35% of an average diameter of the first and the second cylindrical undulating rings when the stent-graft is unconstrained in the radially-expanded deployment state.

59. The stent-graft system according to claim 47, wherein the stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent-graft in the radially-compressed delivery state in which friction between the first and the second cylindrical undulating rings and an inner wall of the delivery catheter helps hold the spring links in the respective extended tensioned states.

60. The stent-graft system according to claim 47, wherein the stent-graft is removably disposed within the portion of the delivery catheter such that the delivery catheter constrains the stent- graft in the radially-compressed delivery state in which the fluid flow guide helps hold the spring links in the respective extended tensioned states.

61. The stent-graft system according to any one of claims 47-60, wherein, when the stent-graft is removably disposed within the portion of the delivery catheter in the radially- compressed delivery state, the first and the second cylindrical undulating rings are disposedalong the stent-graft so as to define an axial gap between the first and the second cylindrical undulating rings.

62. The stent-graft system according to claim 61, wherein the axial gap has a length of 0.1 - 5 mm, measured parallel to the axis.

63. The stent-graft system according to any one of claims 47-60, wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings:(a) axially overlap with each other,(b) axially border each other, or(c) define an axial gap between each other, the axial gap having a length less than 50% of an average height of undulations of the first and the second cylindrical undulating rings, the length and the average height measured parallel to the axis when the stent-graft is in the radially-expanded deployment state.

64. The stent-graft system according to claim 63, wherein the stent- graft is configured such that upon release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings define the axial gap between each other.

65. The stent-graft system according to claim 63, wherein the stent- graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap with each other.

66. The stent-graft system according to claim 65, wherein the stent-graft is configured such that upon the release of the spring links from the delivery catheter, the spring links shorten as they transition toward the respective resting states, thereby approximating the first and the second cylindrical undulating rings such that the first and the second cylindrical undulating rings axially overlap each other by an overlap length measured parallel to the axis, andwherein the overlap length equals 5% - 80% of the average height of the undulations of the first and the second cylindrical undulating rings.

67. The stent-graft system according to claim 66, wherein the overlap length equals 15% - 50% of the average height of the undulations of the first and the second cylindrical undulating rings.

68. A method comprising: introducing a delivery catheter of a delivery system into a blood vessel of patient and advancing the delivery catheter to a target location in the blood vessel while a stentgraft is removably disposed within a portion of the delivery catheter such that the delivery catheter constrains the stent-graft in a radially-compressed delivery state in which (a) spring links of a stent of the stent-graft are in respective extended tensioned states, and (b) first and second ones of cylindrical undulating rings of the stent do not axially overlap with each other, wherein the spring links are joined to the first and the second cylindrical undulating rings; and transitioning the stent-graft to a radially-expanded deployment state by deploying the stent-graft from the delivery catheter, such that the cylindrical undulating rings, which are coupled to a fluid flow guide of the stent-graft at respective axial locations along an axis of the fluid flow guide, provide a tubular shape to the fluid flow guide about the axis, wherein the stent-graft is configured such that upon release of the spring links from the delivery catheter upon the deploying the stent-graft from the delivery catheter, the spring links shorten as they transition toward respective resting states, thereby approximating the first and the second cylindrical undulating rings.

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