u . s . pat . no . 5 , 387 , 235 entitled “ endovascular transluminal prosthesis for repair of aneurysms ” discloses apparatus and methods of retaining grafts onto deployment devices . these features and other features disclosed in u . s . pat . no . 5 , 387 , 235 could be used with the present invention and the disclosure of u . s . pat . no . 5 , 387 , 235 is herewith incorporated in its entirety into this specification . u . s . pat . no . 5 , 720 , 776 entitled “ stent barb ” discloses improved barbs with various forms of mechanical attachment to a stent . these features and other features disclosed in u . s . pat . no . 5 , 720 , 776 could be used with the present invention and the disclosure of u . s . pat . no . 5 , 720 , 776 is herewith incorporated in its entirety into this specification . u . s . pat . no . 6 , 206 , 931 entitled “ graft prosthesis materials ” discloses graft prosthesis materials and a method for implanting , transplanting replacing and repairing a part of a patient and particularly the manufacture and use of a purified , collagen based matrix structure removed from a submucosa tissue source . these features and other features disclosed in u . s . pat . no . 6 , 206 , 931 could be used with the present invention and the disclosure of u . s . pat . no . 6 , 206 , 931 is herewith incorporated in its entirety into this specification . pct patent publication no . wo98 / 53761 entitled “ a prosthesis and a method of deploying a prosthesis ” discloses an introducer for a prosthesis which retains the prosthesis so that each end can be moved independently . these features and other features disclosed in pct patent publication no . wo98 / 53761 could be used with the present invention and the disclosure of pct patent publication no . wo98 / 53761 is herewith incorporated in its entirety into this specification . pct patent publication no . wo99 / 29262 entitled “ endoluminal aortic stents ” discloses a fenestrated prosthesis for placement where there are intersecting arteries . this feature and other features disclosed in pct patent publication no . wo99 / 29262 could be used with the present invention and the disclosure of pct patent publication no . wo99 / 29262 is herewith incorporated in its entirety into this specification . pct patent publication no . wo03 / 034948 entitled “ prostheses for curved lumens ” discloses prostheses with arrangements for bending the prosthesis for placement into curved lumens . this feature and other features disclosed in pct patent publication no . wo03 / 034948 could be used with the present invention and the disclosure of pct patent publication no . wo03 / 034948 is herewith incorporated in its entirety into this specification . u . s . provisional patent application no . 60 / 392 , 682 entitled “ trigger wires ” discloses release wire systems for the release of stent grafts retained on introducer devices . this feature and other features disclosed in u . s . provisional patent application no . 60 / 392 , 682 could be used with the present invention and the disclosure of u . s . provisional patent application no . 60 / 392 , 682 is herewith incorporated in its entirety into this specification . u . s . provisional patent application no . 60 / 392 , 667 entitled “ thoracic deployment device ” discloses introducer devices adapted for deployment of stent grafts particularly in the thoracic arch . this feature and other features disclosed in u . s . provisional patent application no . 60 / 392 , 667 could be used with the present invention and the disclosure of u . s . provisional patent application no . 60 / 392 , 667 is herewith incorporated in its entirety into this specification . u . s . provisional patent application no . 60 / 391 , 737 entitled “ a stent - graft fastening arrangement ” discloses arrangements for fastening stents onto grafts particularly for exposed stents . this feature and other features disclosed in u . s . provisional patent application no . 60 / 391 , 737 could be used with the present invention and the disclosure of u . s . provisional patent application no . 60 / 391 , 737 is herewith incorporated in its entirety into this specification . pct patent publication no . wo03 / 053287 entitled “ improving graft adhesion ” discloses arrangements on stent grafts for enhancing the adhesion of such stent grafts into walls of vessels in which they are deployed . this feature and other features disclosed in pct patent publication no . wo03 / 053287 could be used with the present invention and the disclosure of pct patent publication no . wo03 / 053287 is herewith incorporated in its entirety into this specification . u . s . provisional patent application no . 60 / 405 , 769 entitled “ composite prostheses ” discloses prostheses or stent grafts suitable for endoluminal deployment . these prostheses and other features disclosed in u . s . provisional patent application no . 60 / 405 , 769 could be used with the present invention and the disclosure of u . s . provisional patent application no . 60 / 405 , 769 is herewith incorporated in its entirety into this specification . now looking more closely at the drawings and in particular fig1 to 2 . now looking more closely at the drawings and in particular fig1 to 2 . it will be seen from an end on view of the stent graft prosthesis that in its unrestrained state , as particularly shown in fig1 , it has a substantially circular body end 1 . a deployment device for such a stent graft prosthesis has towards its proximal end a retention arrangement 3 for the retention of the proximal end of the stent graft body end 1 to the deployment device , the mechanism for which will be discussed in detail in relation to fig3 to 5 . the retention arrangement 3 engages various points around the circumference of the stent graft body end 1 to the deployment device to give the asymmetric arrangement as shown in fig2 . to provide the stent graft retention of the present invention , points of the circumference of the graft 1 as shown by the arrows 9 in fig1 are drawn towards the retention arrangement 3 and retained by thread - like material 11 such as fibres or suture material so that the end on view of the stent graft becomes substantially as shown in fig2 . in this embodiment there are three retention points but other numbers of retention points may also be used . this asymmetric arrangement of stent graft attachment produces a larger fold 13 and two smaller folds 15 . it will be noted , too , that the larger circumferential portion of the proximal end of the graft produces the larger fold 13 and the smaller circumferential portions of the proximal end of the graft produce the smaller folds 15 . one embodiment of a deployment device and stent graft suitable for the stent graft retention of the present invention is shown in fig3 to 5 . the deployment device 2 in the region of the proximal retention has a guide wire catheter 4 and a trigger wire catheter 8 coaxially around the guide wire catheter 4 . trigger wires 5 pass along the annular space 10 between the guide wire catheter 4 and the trigger wire catheter 8 and exit through apertures 7 at the retention points and then re - enter the annular space 10 between the guide wire catheter 4 and the trigger wire catheter 8 and pass into the nose cone 6 . the apertures 7 may be equally spaced around the trigger wire catheter or they may be spaced at other selected spacings . in this embodiment there are three apertures 7 spaced at approximately 120 degrees to each other around the circumference of the trigger wire catheter 8 . where each trigger wire 5 exits out of aperture 7 a thread of suture material or other thread - like material 11 is looped around the trigger wire 5 and is fastened to a bight 14 of the graft material of the stent graft 1 and tied off with a knot 12 . as can particularly be seen in fig3 the stent graft has zig zag z stents 17 on its inside for the first two stents from the proximal end and then outside zig zag z stents 19 distally thereof . each stent is fastened by of sutures 21 to the graft material . barbs 23 may also be used to encourage retention of the stent grafts against the wall of the aorta . it will be noted that the barbs 23 are distally facing so that pressure of blood flow will cause then to engage more strongly into the wall of the aorta . in some embodiments the thread of suture material or other thread - like material 11 may also be fastened around a portion of the zig zag z stent 17 . now looking at the embodiment shown in fig6 , 7 and 8 it will be seen that a thoracic arch 30 of an aorta 25 has an outer curve 33 and an inner curve 31 . a stent graft is deployed into the thoracic arch to span , for instance , a tear 26 in the wall of the aorta 25 which has caused an aortic dissection 27 . a deployment device 32 is inserted into the aorta 25 and bent around the thoracic arch 30 . owing to the curvature of the thoracic arch 30 the deployment device 32 will tend to be nearer the outer curve 33 and hence to ensure good engagement of the stent graft on the inner curve , the stent graft retention of the present invention is used . as can be seen in fig6 the deployment device 32 which is deployed into the thoracic arch 30 has a stent graft prosthesis 34 as shown by the dotted line held within a movable outer sheath 36 . in this embodiment the prosthesis 34 does not have a distal retention mechanism associated with the deployment device and hence when the sheath 36 is withdrawn as shown in fig7 the stent graft under the influence of its self expanding stents 35 opens except at the proximal end 38 where the graft is retained to the deployment device 32 by means of the stent graft retention of the present invention . as can be particularly be seen in fig7 the larger fold 13 of the stent graft is extended towards the inner side of the curve 31 of the thoracic arch 30 and in this position blood flow can flow through the larger fold 13 and cause it to extend against the inner wall 31 before the stent graft fully engages the outer side of the curve 33 . at this stage barbs 23 , ( see fig3 ) if present , at the proximal end can engage into the inner wall 31 of the aorta and ensure that that portion of the proximal end of the stent graft is retained against the inside wall of the aorta 25 . as shown in fig8 trigger wires have been released ( by a mechanism not shown ) so that the stent graft retention has been released and the full circumference of the proximal end of the graft has now fully deployed against the walls of the thoracic arch . hence there is not the danger of a portion of the circumference of the proximal end of the graft , particularly that engaged against the inner curve 31 folding inwards under the influence of pulsating blood flow and closing off the aorta . other barbs 23 , if present at the proximal end , can then engage the wall of the aorta and ensure that that the entire proximal end of the stent graft is retained against the wall of the aorta . it will be noted that in this embodiment the fastenings 11 , which are used to retain the stent graft to the trigger wires , remain on the stent graft . an alternative embodiment of deployment of a stent graft prosthesis retained by the arrangement of the present invention is shown in fig9 , 10 and 11 . the stent graft in this embodiment is used to span an aneurysmal sac 29 . a number of features are substantially similar to those of fig6 , 7 and 8 and the same reference numerals are used for corresponding items . the stent graft prosthesis is similar at the proximal end to that depicted in fig6 to 8 , but at its distal end it has a distally extending exposed zig zag z stent 42 . this distally extending exposed stent 42 may have barbs 47 . in this embodiment the deployment device is deployed in the aorta 30 in the same manner as shown in fig6 but subsequent deployment of the stent graft prosthesis occurs in two stages . in a first stage the sheath 36 is withdrawn , as was shown fig7 , but as well as the proximal end 38 being retained by the asymmetric proximal stent graft attachment a capsule 40 retains the exposed stent 42 at the distal end . in the next stage as shown in fig1 , the capsule is withdrawn distally so that the exposed stent is released and because of their self expanding nature expand to bear against the walls of the aorta at the distal end of the stent graft prosthesis . the barbs 47 can engage into the wall of the aorta to retain the stent graft in position . at this stage the proximal end 38 of the stent graft prosthesis is still retained to the deployment device by the retention arrangement of the present invention . it will be noted that the larger fold 13 of the graft is towards the inner side of the curve 31 of the thoracic arch 30 and in this position blood flow can flow through the larger fold 13 and cause it to extend against the inner wall 31 before the graft fully engages the outer side of the curve 33 . then as shown in fig1 , in a similar manner to that shown in fig8 , the trigger wires can be released ( by a mechanism not shown ) so that the stent graft prosthesis is released and the full circumference of the proximal end of the graft can fully deploy against the walls of the thoracic arch . hence there is not the danger of a portion of the circumference of the proximal end of the graft , particularly that engaged against the inner curve 31 folding inwards and closing off the aorta . other barbs 23 , if present at the proximal end , can then engage the wall of the aorta and ensure that that the entire proximal end of the stent graft is retained against the wall of the aorta . it will be noted that in this embodiment the fastenings 11 , which are used to retain the stent graft to the trigger wires , remain on the stent graft . the nose cone 44 of the deployment device can then be withdrawn to the capsule 40 and the deployment device withdrawn . throughout this specification various indications have been given as to the scope of the invention but the invention is not limited to only one of these but may reside in two or more of these combined together . the examples are given for illustration only and not for limitation .
an arrangement for mounting a stent graft prosthesis onto a deployment device with a retention arrangement which includes retention at a number of points of the circumference of the proximal end of the stent graft prosthesis . the arrangement provides a greater circumferential distance between two adjacent retention points then other of the points . when the deployment device is deployed in a curved lumen such as the thoracic arch it is oriented so that the greater circumferential distance is on the inner side of the curve .