CA2610703C

CA2610703C - Side branch stent graft

Info

Publication number: CA2610703C
Application number: CA2610703A
Authority: CA
Inventors: David Ernest Hartley; Krasnodar Ivancev
Original assignee: Cook Medical Technologies LLC
Current assignee: Cook Medical Technologies LLC
Priority date: 2005-06-01
Filing date: 2006-06-01
Publication date: 2014-07-22
Anticipated expiration: 2026-06-01
Also published as: AU2006252495B2; CA2610703A1; US7846194B2; WO2006130755A3; AU2006252495A1; US20060287704A1; EP1885289A2; JP2008541949A; WO2006130755A2; JP5037500B2; EP1885289B1

Abstract

A side branch stent graft suitable for the iliac arteries has a main tubular body of a biocompatible graft material and a tubular side branch. The tubular side branch is affixed into the main tubular body so that a side branch lumen is in fluid communication with a main lumen. There is at least one external zig-zag stent on the main tubular body proximal of the tubular side branch, one central external stent which also encompasses the side arm, at least one external zig-zag stent on the main tubular body distal of the tubular side branch and one internal zig-zag stent at the distal end of the main tubular body. A reinforcing ring is around the proximal end of the main tubular body and stitched thereto.

Description

SIDE BRANCH STENT GRAFT
Description Technical Field This invention relates to a side branch stent graft and in the preferred embodiments to the construction and deployment of a stent graft for the iliac artery.
Background of the Invention Stent grafts are used for treatment of vasculature in the human or animal body to bypass a repair or defect in the vasculature. For instance, a stent graft may be used to span an aneurism which has occurred in or is associated with the iliac artery. In many cases, however, such a damaged or defective portion of the vasculature may include a branch vessel such as an internal iliac artery.
Bypassing such a branch vessel without providing blood flow into it can cause problems and hence it has been proposed to provide a side branch on a stent graft which when deployed is positioned over the opening to the internal iliac artery and then another stent graft can be deployed through the side branch into the internal iliac artery to provide a blood flow path to the internal iliac artery.
Generally, when deploying an endovascular stent graft into a body lumen, it is possible to obtain access to such a body lumen from each end of the lumen where necessary, thereby facilitating placement of a device in the lumen. The internal iliac artery, which extends from the common iliac artery below the aortic bifurcation, is to all intents and purposes a blind vessel because there is no practical way of performing an endovascular minimally invasive procedure into that vessel other than by entry from the common iliac artery. The term blind vessel is used herein to describe such a vessel.
There have been proposals to deploy a branched stent graft into the common iliac artery via a femoral artery from a femoral incision with the branched stent graft having a side arm to extend into or at least adjacent the internal iliac artery. However, the use of such devices is very dependent upon favourable layout of the arteries and in many cases access is extremely difficult. Access over the aortic bifurcation has been proposed but as there is limited distance between the aortic bifurcation and the iliac bifurcation special construction of a stent graft for this region is desirable.
Summary of the Invention The present invention seeks to provide an improved side branch stent graft and an improved stent graft for deployment particularly into the iliac arteries or at least to provide a physician with a useful alternative.
According to an aspect of the present invention, there is provided a side branch stent graft.
The teachings herein will be generally discussed with reference to a branched stent graft which can be deployed so that its branch is directed towards an internal iliac artery from the common iliac but is not so limited and may be used with deployment into any branched vessel but is particularly applicable where the vessel into which the device is deployed is a blind vessel, that is, access is not available from an end of the vessel remote from the bifurcation from a main vessel.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis is the end of the aorta, deployment device or prosthesis further away in the direction of blood flow from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels, similar terms such as caudal and cranial should be understood.
Preferably there are one or two external zig-zag stents proximal of the tubular side branch and from one to three external zig-zag stents distal of the tubular side branch.
The reinforcing ring around the proximal end of the tubular body can comprise at least two turns of nitinol wire, each end of the nitinol wire terminating in a loop.
Preferably the tubular side branch comprises a connection socket for an extension stent. In one embodiment the connection socket comprises a first resilient ring around the tubular side branch at a distal end thereof, a second resilient ring spaced apart along the tubular side branch from the first ring and a zig zag resilient stent between the first and second rings. The zig zag resilient stent and the first and second rings are preferably on the outside of the tubular body and the first and second rings preferably comprise shape memory wire. The first and second rings preferably comprise at least two turns of wire with each end terminating in a loop.
The zig zag resilient stent of the connection socket preferably comprises a shape memory wire and the zig zag resilient stent defines a cylindrical form having a diameter less than that of the tubular side branch whereby to define a self contracting stent.
The invention also encompasses a side arm stent graft comprising a main tubular body of a biocompatible material, a fenestration in the main tubular body defined by a peripheral edge and a side arm being a tube of biocompatible material being joined around the peripheral edge at a joined region by stitching and extending from the main tube at an acute angle thereto and being in fluid communication with the main tubular body, at least one external zig-zag stent on the main tubular body proximal of the side arm, at least one external zig-zag stent on the main tubular body distal of the side arm, one internal zig-zag stent at the distal end of the main tubular body, and a reinforcing ring around the proximal end of the main tubular body and stitched thereto.
Preferably the fenestration is selected from the group comprising an elongate aperture, a substantially rectangular aperture, a substantially elliptical aperture and a substantially triangular aperture. The acute angle may be in the range of from 15 to 60 degrees and preferably 15 to 45 degrees.
The or each external zig-zag stents proximal of the tubular side branch can have a length of 14 mm and are spaced apart by about 2 mm and the or each external zig-zag stents distal of the tubular side branch has a length of 12 mm and are spaced apart by about 5 mm.
There may be further a central external zig-zag stent around the main tubular body and the tubular side branch. The central external zig-zag stent can have a length of 14 mm and is spaced apart from the stent proximal to it by about 2 mm and from the stent distal of it by about 5 mm.
The main tubular body can have a diameter of from 12 mm in a central portion and remaining at 12 mm or expanding to 20 mm at a proximal end with a frustoconical portion between the 12 mm and 20 mm portions and the tubular side branch has a diameter of about 8 mm. Alternatively the main tubular body can have a diameter of about 12 mm proximal of the tubular side branch and in a central portion and a diameter distal of the tubular side branch of from about mm to 16 mm frustoconical portion between the 12 mm and 16 mm portions.
The main tubular body can have a length of about 69 mm to 119 mm and the tubular side branch has a length of about 25 mm. The stent graft can have a length from its proximal end to the distal end of the side arm of about 45 mm to 61 mm. The stent graft can have a length from its distal end to the distal end of the side arm of about 24 mm to 58 mm.
Brief Description of the Drawing Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 shows a first embodiment of stent graft intended for use in the iliac artery;
Figure 2 shows a second embodiment of stent graft intended for use in the iliac artery;
Figure 3 shows a third embodiment of stent graft intended for use in the iliac artery;
Figure 4 shows a fourth embodiment of stent graft intended for use in the iliac artery;
Figure 5 shows a fifth embodiment of stent graft intended for use in the iliac artery;
Figure 6 shows a sixth embodiment of stent graft intended for use in the iliac artery;
Figures 7A to 7F show schematically a first range of preferred configurations of stent grafts intended for use in the iliac artery;
Figures 8A to 8F show schematically an alternative range of preferred configurations of stent grafts intended for use in the iliac artery;
Figures 9A to 9D show schematically an alternative range of preferred configurations of stent grafts intended for use in the iliac artery;
Figure 10 shows a detail of the proximal end of an embodiment of stent graft, and Figure 11 shows schematically a cross section of an aneurysed aorta and common iliac artery with a composite stent graft system deployed into it including an embodiment of iliac stent graft.
Detailed Description Now looking more closely at the drawings and in particular Figure 1, an embodiment of stent graft 1 comprises a tubular body 3 with a side arm 5, also a tubular body, stitched into an aperture in the main body 3 at 7 so as to allow fluid communication from the lumen of the main body into the lumen of the side arm 5.
The main tubular body 3 has a reinforcing ring arrangement 9 at its proximal end 11. The construction of the reinforcing ring 9 will be discussed in relation to Figure 10. The tubular body 3 also has a number of external zig-zag self-expanding stents 13, 14 and 16 along its length and an internal self-expanding zig-zag stent 15 at its distal end 17.
PCT Patent Publication No. WO 2006/034276 entitled "Side Branch Stent Graft" includes discussion of one method of connection of a side arm to a main tubular body in a stent graft which could be used in the embodiments of stent graft taught herein, if desired.
On the side arm 5 there is a connection socket arrangement 19. The connection socket arrangement includes a self-expanding stent 21 between two reinforcing rings 22 and 23.
PCT Patent Publication No. WO 2006/034340 entitled "Stent Graft Connection Arrangement" discloses a stent graft connection arrangement of the type suitable for the side arm of the stent graft of the type taught herein, although other connection arrangements apparent to the skilled person could instead be used.

In the side arm stent graft shown in Figure 1 there are two external stents 13 proximal of the connection of the side arm, one central external stent 14 which also encompasses the side arm and three external stents 16 and one internal stent 15 distal of the connection with the side arm 5. The internal and external stents are fastened to the tubular body by known methods including by stitching, adhesive or the like.
The stent graft depicted in Figure 1 would normally have a diameter of the main tubular body of 12mm and a diameter of the side arm of 8mm. The stent graft shown in Figure 1 is the longest that would normally be used in deployment into the iliac artery of a patient as will be discussed below.
Figure 2 shows the shortest practical stent graft which can be deployed into a common iliac artery. The stent graft 29 depicted in Figure 2 has a tubular body 30 and a side arm 32. In this embodiment there is one external stent 13 proximal of the junction with the side arm, one central external stent 14 which also encompasses the side arm and one external stent 16 and one internal stent 15 distal of the junction with the side arm. The stent graft depicted in Figure 2 has a diameter of the main tubular body 30 of 12mm and a diameter of the side arm 32 of 8mm. The construction of the connection socket 33 on the stent graft shown in Figure 2 is similar to that shown in Figure 1.
For placement of a side branch stent graft into the internal iliac artery, the critical dimension is the distance from the proximal end 11 of the stent graft to the end 25 of the side arm 5 as this is the distance which must fit between the aortic bifurcation and the entrance to the internal iliac artery as will be discussed below.
Figure 3 shows an alternative embodiment of stent graft 35 substantially similar to that shown in Figure 1 except that the tubular body 40 is tapered to a diameter of 10mm distal of the connection with the side arm 41 whereas the diameter of the tubular body 40 proximal of the connection is 12mm.
Similarly in Figure 4 the stent graft 36 has a tubular body 37 which is tapered distal of the side arm connection 38 to give a diameter of lOmm whereas the diameter of the tubular body 37 proximal of the connection is 12mm.

Figure 5 shows another embodiment of stent graft 40 substantially similar to that shown in Figure 1 except that the tubular body 41 is expanded to a diameter of 20 mm at its proximal end 42 proximal of the connection with the side arm 44 with a frusto-conical portion 41a joining the central portion to the proximal portion and also expanded to a diameter of 16mm at its distal end 43 with a frusto-conical portion 41b joining the central portion to the distal portion.
Similarly in Figure 6 the stent graft 45 has a tubular body 46 which is expanded distal of the side arm 47 connection to give a diameter of 16mm at its distal end 48 with a frusto-conical portion 46a joining the central portion to the distal portion whereas the diameter of the tubular body proximal of the connection is 12mm.
Figures 7A to 7F show schematically a range of sizes of stent grafts for the common iliac artery in stylised form. The position of stents is represented by a box on the stylised form.
Figure 7A shows a schematic stent graft 50 with a proximal reinforcing ring 51, two external stents 52 proximal of the side arm 53, central external stent 54, three external stents 55 distal of the side arm 53 and one internal distal-most stent 56. The stents 52 and 54 each have a length of 14mm and are separated by a gap 57 of 2mm. The stents 55 each have a length of 12mm and are separated by a gap 58 of 5mm. The stent 56 has a length of 17mm and is separated from the stent 55 by a gap of 5mm.
Figures 7B, 7C, 7D, 7E and 7F all show the various configurations of stent graft with varying numbers of stents proximal and distal of the side branch.
Table 1 shows a range of sizes of stent grafts and numbers and sizes of stents as depicted in Figures 7A to 7F. The overall length is the dimension 60 shown in Figure 7A, the proximal length is the length 61 shown in Figure 7A and the distal length is the length 62 shown in Figure 7A.

Table 1 Fig Fig Fig Fig7D Fig7E Fig7F
_ 7A 7B 7C
Overall Length (mm) 119 102 85 103 86 69 Proximal length (mm) 61 61 61 45 45 45 Distal length (mm) 58 41 24 58 41 24 Proximal Diameter (mm) 12 12 12 12 12 12 Central Diameter (mm) . 12 12 12 12 12 12 Distal Diameter (mm) 12 12 12 12 12 12 Number of Stents on main 7 6 5 6 5 4 body Number of stents on main 2 2 2 1 1 1 body proximal of side arm Length of stents on main 14 14 14 14 14 14 body proximal of side arm (mm) Spacing of stents on main 2 2 2 2 2 2 body proximal of side arm (mm) , Number of central external 1 1 1 1 1 1 stents Length of central external 14 14 14 14 14 14 stents (mm) Number of stents on main 4 3 2 4 3 2 body distal of side arm Length of external stents 12 12 12 12 12 12 on main body distal of side arm (mm) , Length of distal most 17 17 17 17 17 17 internal stent on main body (mm) Spacing of stents on main 5 5 5 5 5 5 body distal of side arm (mm) .
Number of Stents on side 1 1 1 1 1 1 arm ....
12 mm Ring at proximal Yes Yes Yes Yes Yes Yes end _ 7 mm Rings on side arm Yes Yes Yes Yes Yes Yes As discussed above, the proximal length is important as a stent graft must be able to be deployed with its distal end below the aortic bifurcation and the distal end of its side arm proximal of the iliac bifurcation between the internal and external iliac arteries.
Similarly Figures 8A to 8F show schematic configurations of stent grafts similar to those of the corresponding drawings in Figures 7A to 7F except that in Figures 8A to 8F the proximal end 70 of the stylised stent graft has a diameter of 12mm and the distal end 71 is tapered to a diameter of lOmm. The lesser diameter of the distal end of the stent graft in the embodiments of stent graft shown in Figures 8A to 8F allow for sealing into a smaller non-aneurysed region of the external iliac artery without exerting excessive pressure onto the walls of the vasculature.
Table 2 shows a range of sizes of stent grafts as depicted in Figures 8A to 8F. The overall length is the dimension 60 shown in Figure 7A, the proximal length is the length 61 shown in Figure 7A and the distal length is the length shown in Figure 7A.

Table 2 Fig Fig Fig8 Fig Fig Fig Overall Length (mm) 119 102 85 103 86 69 Proximal length (mm) 61 61 61 45 45 45 Distal length (mm) 58 41 24 58 41 24 Proximal Diameter (mm) 12 12 12 12 12 12 Central Diameter (mm) 12 12 12 12 12 12 Distal Diameter (mm) 10 10 10 10 10 10 Number of Stents on 7 6 5 6 5 4 main body Number of stents on main 2 2 2 1 1 1 body proximal of side arm Length of stents on main 14 14 14 14 14 14 body proximal of side arm (mm) Spacing of stents on main 2 2 2 2 2 2 body proximal of side arm (mm) Number of central 1 1 1 1 1 1 external stents Number of stents on main 4 3 2 4 3 2 body distal of side arm Length of central external 14 14 14 14 14 14 stents (mm) Length of external stents 12 12 12 12 12 12 on main body distal of side arm (mm) Length of distal most 17 17 17 17 17 17 internal stent on main body (mm) Spacing of stents on main 5 5 5 5 5 5 body distal of side arm (mm) Number of Stents on side 1 1 1 1 1 1 arm 12 mm Ring at proximal Yes Yes Yes Yes Yes Yes end 7 mm Rings on side arm Yes Yes Yes Yes Yes Yes Figures 9A to 9D show schematic configurations of stent grafts similar to those of the corresponding drawings in Figures 7A to 7F except that in Figures to 9D the proximal end 70 of the stylised stent graft has a diameter of 20 mm and the distal ends 71 have diameters of 12 mm and 16 mm.
Table 3 shows a range of sizes of stent grafts as depicted in Figures 9A to 9D. The overall length is the dimension 60 shown in Figure 7A, the proximal length is the length 61 shown in Figure 7A and the distal length is the length shown in Figure 7A.

Table 3 Fig Fig Fig Fig Overall Length (mm) 119 119 102 102 Proximal length (mm) 61 61 61 61 Distal length (mm) 58 58 41 41 Proximal Diameter (mm) 20 20 20 20 Central Diameter (mm) 12 12 12 12 Distal Diameter (mm) 12 16 12 16 Number of Stents on main 7 7 6 6 body Number of stents on main 2 2 2 2 body proximal of side arm Length of stents on main 14 14 14 14 body proximal of side arm (mm) Spacing of stents on main 2 2 2 2 body proximal of side arm (mm) Number of central external 1 1 1 1 stents Length of central external 14 14 14 14 stents (mm) Number of stents on main 4 4 3 3 body distal of side arm Length of external stents 12 12 12 12 on main body distal of side arm (mm) Length of distal most 17 17 17 17 internal stent on main body (mm) Spacing of stents on main 5 5 5 5 body distal of side arm (mm) Number of Stents on side 1 1 1 1 arm 20 mm Ring at proximal Yes Yes Yes Yes end 7 mm Rings on side arm Yes Yes Yes Yes Figure 10 shows the construction of a preferred embodiment of stent graft with a proximal reinforcing ring. The same reference numerals as used in Figure 1 are used for Figure 10 for the corresponding components. The tubular body 3 of the = CA 02610703 2013-05-30 stent graft 1 has a proximal-most external stent 13 stitched onto the tubular body by means of stitches 75. At the proximal end 78 of the stent graft 1 a reinforcing ring 9 is provided. The reinforcing ring 9 comprises two turns of a shape memory wire 74, such as NitinolTM wire, around the proximal end 78 and loops 76 at each terminal end of the NitinolTM wire 74. The loops 76 are provided to prevent the ends of the Nitinol TM wire causing damage to the vasculature in which they are deployed.
The two turns of NitinolTM wire 74 are stitched by means of stitching 77 to the proximal end of the tubular body 3.
The NitinolTM reinforcing ring 9 provides reinforcement for the proximal end of the stent graft so that when a catheter or other device is being deployed into the proximal end of the stent graft the end of the stent graft cannot be damaged.
The NitinolTM reinforcing ring 9 provides a fixed diameter into which another self expanding or balloon expandable stent graft can expand or be expanded within the proximal end of the stent graft 1.
Figure 11 shows a full assembly of a composite stent graft system into an aneurysed aortic and common iliac artery using the preferred embodiment of stent graft for the common iliac artery.
The vasculature illustrated generally consists of a descending aorta 152 extending down to renal arteries 153 and further extending as the infra-renal aorta 150 down to an aortic bifurcation 178 and into the iliac and contra-iliac arteries 154 and 187. The common iliac artery 154 further bifurcates into an external iliac artery 164 and an internal iliac artery 168. It is this internal iliac artery 168 which is described above as a blind artery as endovascular access is only available via the common iliac artery. An aneurysed region 151 of the aorta 150 extends down into the common iliac artery 154.
In Figure 11 the aorta 150 has an aneurysm 151 which extends from below the renal arteries 153 into the common iliac artery 154. The aorta 152 proximal of the renal arteries 153 is not aneurysed and provides a suitable landing zone for a proximally extending external stent 156 of a bifurcated stent graft 157.
The general order of placement of such a stent graft assembly for an aneurysed aorta is first that the iliac branch stent graft 160 is placed first with its distal end 162 placed into a non-aneurised region of the external iliac artery 164.
The side arm 166 extends towards the internal iliac artery 168. Subsequent to placement of the iliac branched stent graft 160 a covered leg extension 170 is placed extending from the side branch 166 so that it extends into and seals in the internal iliac artery 168. The covered leg extension 170 can be a covered balloon expandable stent or a covered self expanding stent.
The main bifurcated stent graft 157 is then deployed through the contra-lateral iliac artery 187 so that its longer leg 176 extends down the contra-lateral iliac artery 187 and its shorter leg 172 terminates proximal of the reinforcing ring 174 on the iliac stent graft 160 and proximal of the aortic bifurcation 178.
The proximal end of the bifurcated stent graft 157 seals into a landing zone in the region of aorta 182 just distal of the renal arteries 153 and the proximally extending supra-renal external stent 156 extends over the renal arteries to the aorta region 152 to provide good support for the bifurcated stent graft. A leg extension 190 can then be deployed to connect the shorter leg 172 of the main bifurcated stent graft 157 to the reinforcing ring 174 on the iliac stent graft 160.
In a final deployment stage a leg extension 185 can deployed into the longer leg 176 to seal into a non-aneurised portion of the contra-lateral common iliac artery 187 if the longer leg does not already seal onto such a zone.
By this arrangement a stent graft is effectively bridging the aneurised region by sealing in the non-aneurised portion of the aorta as well as in the non-aneurised portions of the iliac arteries.
The critical dimension in relation to deployment of a stent graft into an aneurised iliac artery 154 is the distance shown as 135 in Figure 11. This is the distance from the iliac bifurcation 178 down to the bifurcation of the external iliac artery 164 and the internal iliac artery 168. The proximal length of a stent graft of the type discussed in relation to Figures 1 to 6 and as shown in Figures 7 to 9 is less than the distance 135 so that access over the aortic bifurcation is possible to endovascularly enter the proximal end 174 of the stent graft 160 and the end of the side branch 166 of the stent graft 160 is placed so that a guide wire (not shown) can extend out of the side branch 166 and be manipulated into the internal iliac artery 168.
The length of the distal portion 162 of the stent graft 160 is such that it can extend to non-aneurised region of the external iliac artery 164 so that a seal may be obtained with the distal end of the stent graft 160. Where the aneurism extends some distance down the external iliac artery a further leg extension may be placed so that the stent graft assembly extends through non-aneurised region of the external iliac artery.
Throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of the disclosed features but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.
Throughout this specification and the claims that follow, unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. A side branch stent graft including a main tubular body of a biocompatible graft material and providing a main lumen therethrough;
a tubular side branch providing a side branch lumen therethrough, the tubular side branch being stitched to the main tubular body so that the side branch lumen is in fluid communication with the main lumen, the tubular side branch extending from the main tubular body at an acute angle thereto;
at least one external zig-zag self-expanding stent on the main tubular body proximal of the tubular side branch;
at least one external zig-zag self-expanding stent on the main tubular body distal of the tubular side branch;
at least one internal zig-zag self-expanding stent at the distal end of the main tubular body;
a reinforcing ring around the proximal end of the main tubular body and stitched thereto, the reinforcing ring comprising at least two turns of shape memory wire, each end of the shape memory wire terminating in a loop;
and a single central external zig-zag self-expanding stent that extends around both the main tubular body and the proximal end of the tubular side branch;
wherein the tubular side branch comprises a connection socket for an extension stent at its distal end, wherein the connection socket comprises a first resilient ring around the tubular side branch at a distal end thereof, a second resilient ring spaced along the tubular side branch from the first ring, and a zig-zag resilient stent between the first and second rings.

2. A side branch stent graft as in claim 1, wherein there are one or two external zig-zag stents proximal of the tubular side branch.

3. A side branch stent graft as in claim 1 or 2, wherein there are from one to three external zig-zag stents distal of the tubular side branch.

4. A side branch stent graft as in claim 1, wherein the zig-zag resilient stent and the first and second rings are on the outside of the tubular side branch.

5. A side branch stent graft as in any one of claims 1 to 4, wherein the first and second rings of the tubular side branch comprise shape memory wire.

6. A side branch stent graft as in any one of claims 1 to 5, wherein the first and second rings of the tubular side branch comprise at least two turns of wire with each end terminating in a loop.

7. A side branch stent graft as in any one of claims 1 to 6, wherein the zig-zag resilient stent comprises a shape memory wire and the zig-zag resilient stent has a cylindrical form having a diameter less than that of the tubular side branch so as to provide a self-contracting stent.

8. A side branch stent graft as in any one of claims 1 to 7, wherein the acute angle is in the range of from 15 to 60 degrees.

9. A side branch stent graft as in claim 8, wherein the acute angle is in the range of from 15 to 45 degrees.

10. A side branch stent graft as in any one of claims 1 to 9, wherein the or each external zig-zag stents proximal of the tubular side branch has a length of 14 mm, the zig-zag stents being spaced apart by about 2 mm.

11. A side branch stent graft as in any one of claims 1 to 10, wherein the or each external zig-zag stent distal of the tubular side branch has a length of mm, the zig-zag stents being spaced apart by about 5 mm.

12. A side branch stent graft as in any one of claims 1 to 13, wherein the central external zig-zag stent has a length of 14 mm and is spaced from the stent proximal to it by about 2 mm and from the stent distal of it by about 5 mm.

13. A side branch stent graft as in any one of claims 1 to 12, wherein the main tubular body has a diameter of about 12 mm and the tubular side branch has a diameter of about 8 mm.

14. A side branch stent graft as in any one of claims 1 to 13, wherein the main tubular body has a diameter of about 12 mm proximal of the tubular side branch and a diameter distal of the tubular side branch of about 10 mm.

15. A side branch stent graft as in any one of claims 1 to 12, wherein the main tubular body has a diameter of about 20 mm proximal of the tubular side branch and a diameter distal of the tubular side branch of about 16 mm.

16. A side branch stent graft as in any one of claims 1 to 15, wherein the main tubular body has a length of about 69 mm to 119 mm and the tubular side branch has a length of about 25 mm.

17. A side branch stent graft as in any one of claims 1 to 16, wherein the stent graft has a length from its proximal end to the distal end of the side branch of about 45 mm to 61 mm.

18. A side branch stent graft as in any one of claims 1 to 17, wherein the stent graft has a length from its distal end to the distal end of the side branch of about 24 mm to 58 mm.