Abstract:
A stent assembly ( 42 ) adapted for endoluminal placement by endovascular deployment for the treatment of a false lumen ( 10 ) associated with a vascular dissection. The stent assembly has a number of self expanding stents ( 35 ) connected together to define an elongate substantially cylindrical lumen wall engaging surface. The stents are adapted to provided pressure on the wall of the lumen adjacent to and extending away from a rupture. A deployment device ( 40 ) for the stent assembly includes a sheath ( 48 ) and a retention and release arrangement ( 50 ) to retain the proximal end ( 37 ) of the stent graft to the deployment device. Release of the stent assembly is by withdrawal of the sheath before release of its proximal end by the use of a trigger wire ( 54 ) of the retention and release arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent document is a divisional application that claims the benefit of priority under 35 U.S.C. §121 of U.S. patent application Ser. No. 11/237,120, filed Sep. 28, 2005, which claims priority to U.S. Provisional Patent Application Ser. No. 60/613,950, filed Sep. 28, 2004 which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to a device for the treatment of aortic arch disease and more particularly to the treatment of a form of aortic aneurysm known as an aortic dissection. 
     BACKGROUND OF THE INVENTION 
     An aortic dissection is a form of aneurysm to the descending aorta in which the wall of the aorta is damaged to such an extent that blood under pressure can get between inner and outer layers of the wall of the aorta to expand part of the wall into an inflated sac of blood which is referred to as a false lumen. The inflated sac of blood or false lumen so formed may extend some distance down the descending aorta and open out into the aorta again further down. 
     It is the object of this invention to provide a device and a method of treatment for an aortic dissection using the device will also be discussed. 
     Throughout this specification the term proximal with respect to both human or animal vasculature and the deployment device and prosthesis will be used to refer to the region closest to the heart or that part of the deployment device or of the prosthesis which when in use is closest to the heart and the term distal will be used for regions of the human or animal vasculature further from the heart and those parts of the deployment device or prosthesis which in use are further from the heart. 
     SUMMARY OF THE INVENTION 
     In one form the invention comprises a stent assembly comprising a plurality of self expanding zig zag stents and a link arrangement between adjacent stents so that the stents are linked together to define an elongate substantially cylindrical lumen wall engaging surface, each stent having a plurality of struts and bends between the struts and the link arrangement comprising a thread or fibre such as a suture thread which is knotted alternately to a bend of one stent and then a bend of an adjacent stent to provide a link thread of zig zag configuration, whereby upon endoluminal placement by endovascular deployment the stent assembly is adapted to provided pressure on the wall of the lumen to close off a false lumen in the lumen wall with each stent able to act independently of an adjacent stent. In an alternative form the invention comprises a stent assembly comprising a plurality of self expanding zig zag stents, links between adjacent stents so that the stents are linked together to define an elongate substantially cylindrical lumen wall engaging surface whereby upon endoluminal placement by endovascular deployment the stent assembly is adapted to provided pressure on the wall of the lumen to close off a false lumen in the lumen wall. 
     Preferably the links are flexible links. They can be provided by metal rings or can be a thread or fibre such as a braided suture thread knotted to or threaded around bends of the zig-zag stents. In the case of a braided suture material the material may be a 5.0 braided suture. 
     The stents can be formed from stainless steel or Nitinol. 
     The stent assembly can be in the form of a self expanding spiral stent of zig-zag configuration. 
     The stent assembly according to the present invention may provided in three lengths of 4, 6 or 8 stents long, nominally 88, 132 and 178 mm long and have a nominal maximum diameter of 46 mm. 
     In a preferred form the stents may be constructed from stainless steel wire having a diameter of 0.016 inches. 
     In a further form the invention comprises a deployment device and stent assembly for treatment of an aortic dissection, the stent assembly comprising at least one self expanding zig zag stent defining an elongate substantially cylindrical lumen wall engaging surface, and the deployment device comprising an elongate catheter adapted to be deployed over a guide wire, a nose cone at the proximal end of the elongate catheter, a trigger wire arrangement to retain a proximal end of the stent assembly just distal of the nose cone, a sheath over the elongate catheter adapted to retain the stent assembly in a contracted state around the elongate catheter, a release arrangement at the distal end of the elongate catheter to release the trigger wire arrangement and a grip mounted to the sheath to enable withdrawal of the sheath arrangement, whereby upon endoluminal placement by endovascular deployment, retraction of the grip and sheath and release of the stent assembly the stent assembly expands to provide pressure on the wall of the lumen to close off a false lumen in the lumen wall. 
     Preferably the stent assembly comprises a plurality of self expanding zig zag stents and a link arrangement between adjacent stents so that the stents are linked together to define an elongate substantially cylindrical lumen wall engaging surface, each stent having a plurality of struts and bends between the struts and the link arrangement comprising a biocompatible thread or fibre such as a suture thread and knots which are knotted alternately to a bend of one stent and then a bend of an adjacent stent to provide a link thread of zig zag configuration, whereby upon endoluminal placement by endovascular deployment the stent assembly is adapted to provided pressure on the wall of the lumen to close off a false lumen in the lumen wall with each stent able to act independently of an adjacent stent. 
     Preferably the distal end of the stent assembly is retained to the deployment device by a distal trigger wire arrangement and there are means at the distal end of the elongate catheter to release the distal trigger wire arrangement. 
     Preferably the trigger wire arrangement comprises at least one trigger wire extending from the release mechanism through the deployment catheter and the trigger wire engaged with the proximal end of the stent assembly. 
     There can be three trigger wires extending from the release mechanism through the deployment catheter and each of the trigger wires engaging with a proportion of the bends of the proximal most stent of the stent assembly. 
     The engagement of the trigger wire with the proximal end of the stent assembly can comprise loops of a biocompatible thread engaging between bends of the proximal stent of the stent assembly and the trigger wire. 
     The proximal end of the stent assembly can comprise a proximal stent and a circumferential biocompatible thread including portions between adjacent bends of the proximal end of the proximal stent and the engagement of the trigger wire with the stent assembly comprises the thread portions between adjacent bends extending around the trigger wire. The elongate catheter can include means to supply an angiographic contrast medium at a distal end thereof through the catheter. 
     Links between adjacent stents of the stent assembly can be provided by a thread or fibre such as a suture thread which is knotted alternately to a bend of one stent and then a bend of an adjacent stent to provide a link thread of zig zag configuration. 
     In a further form the invention comprises a method of treatment of a false lumen of an aortic dissection comprising the steps of 
     a) loading a stent assembly onto a deployment device, the stent assembly comprising a plurality of self expanding stents linked together and defining an elongate substantially cylindrical lumen wall engaging surface, the deployment device including a retention arrangement to retain the proximal end of the stent assembly in a retracted state and a trigger wire arrangement to release the retention arrangement to thereby release the proximal end of the stent assembly, a sheath to retain the entire the stent assembly in a retracted state and means to withdraw the sheath, 
     b) endovascularly deploying the deployment device with the stent assembly loaded thereon to the site of the false lumen, 
     c) withdrawing the sheath to expose the stent assembly such that it provides pressure against the wall of the lumen, 
     d) releasing the proximal end of the prosthesis by means of releasing the trigger wire arrangement, and 
     e) withdrawing the deployment device. 
     Preferably the distal end of the stent assembly is retained to the deployment device and previous or subsequent to the step of releasing the proximal end of the prosthesis the distal end is released. 
     In a further form the invention comprises a method of treatment of aortic dissection disease comprising a two stage process to close off a rupture associated with the aortic dissection and to apply pressure to a false lumen associated with the aortic dissection, the method comprising the steps of: 
     a) endovascularly deploying a first deployment device with a stent graft retained thereon to the site of the aortic dissection, 
     b) checking by radiographic techniques that the stent graft is positioned over the site of the rupture, 
     c) deploying the stent graft from the first deployment device, 
     d) withdrawing the first deployment device, 
     e) endovascularly deploying a second deployment device with a stent assembly loaded thereon to the site of the false lumen, the stent assembly comprising a plurality of self expanding stents linked together and defining an elongate substantially cylindrical lumen wall engaging surface, the deployment device including a retention arrangement to retain the proximal end of the stent assembly in a retracted state and a trigger wire arrangement to release the retention arrangement to thereby release the proximal end of the stent assembly, a sheath to retain the entire stent assembly in a retracted state and means to withdraw the sheath, 
     f) withdrawing the sheath to expose the stent assembly such that it provides pressure against the wall of the lumen, 
     g) releasing the proximal end of the prosthesis by means of releasing the trigger wire arrangement, and 
     h) withdrawing the second deployment device. 
     Preferably the distal end of the stent assembly is also retained to the deployment device and previous or subsequent to the step of releasing the proximal end of the prosthesis the distal end is released. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       This then generally describes the invention but to assist with understanding reference will now be made to the drawings which show preferred embodiments of the invention. 
       In the drawings: 
         FIG. 1  shows a schematic view of an aorta with an aortic dissection; 
         FIG. 2  shows the aorta shown in  FIG. 1  with a first deployment device inserted therein; 
         FIG. 3  shows the first stage of deployment of a covered stent graft prosthesis; 
         FIG. 4  shows the fully deployed covered stent graft prosthesis and the deployment of a second deployment device; 
         FIG. 5  shows the first stage of the deployment of a stent assembly from the second deployment device; 
         FIG. 6  shows the next stage of the deployment of the stent assembly from the second deployment device; 
         FIG. 7  shows the fully deployed stent assembly: 
         FIG. 8  shows a stent assembly according to one embodiment of this invention; 
         FIG. 9  shows an alternative embodiment of a stent assembly according to the invention; 
         FIG. 10  shows a still further embodiment of a stent assembly according to the invention; 
         FIG. 11  shows a still further embodiment of a stent assembly according to the invention; 
         FIG. 12  shows a detailed view of the proximal end of a deployment device with a stent assembly mounted thereon according to one embodiment the invention; 
         FIG. 13  shows a detailed cross sectional view of the proximal end of the deployment device and stent assembly of  FIG. 12 ; 
         FIG. 14  shows a detailed view of part of the proximal end of a deployment device and an alternative method by which a stent assembly may be retained onto the deployment device according to one embodiment of the invention; 
         FIG. 15  shows the embodiment of  FIG. 14  when retention sutures are pulled tight; 
         FIG. 16  shows a detailed view of part of the proximal end of a deployment device and an alternative method by which a stent assembly may be retained onto the deployment device according to the invention; and 
         FIG. 17  shows the embodiment of  FIG. 16  when the trigger wires are pulled into place. 
     
    
    
     DETAILED DESCRIPTION 
     Looking more closely to the drawings and in particular  FIG. 1  it will be seen that the aorta comprises an ascending aorta  1  which receives blood from the heart though an aortic valve  2 . At the upper end of the ascending aorta there are branches for the innominate artery  3  the left common carotid artery  4  and the subclavian artery  5 . The aorta after these is referred to as the descending aorta  6  and it is in this region that an aortic dissection can occur. In an aortic dissection the wall of the descending aorta can be injured such as by a traumatic injury so that a partial rupture or tear  7  occurs and the wall of the descending aorta splits so that there is an outer wall  8  and an inner wall  9  between which a false lumen  10  occurs. At some distance down the false lumen  10  the false lumen may again open out into the aorta  6  such as at  11 . The dotted line  12  shows the normal position of the wall of the aorta. 
     Treatment of the aortic dissection requires that the rupture  7  be closed off and the false lumen  10  deflated. 
     As can be seen in  FIG. 2 , a first deployment device  15  with a nose cone  16  has been advanced over a guide wire  17  through the true lumen  18  of the descending aorta  6 . Preferably the deployment device is inserted through a femoral artery and up through the iliac arteries into the aorta using a technique known as the Seldinger technique. 
     Once the deployment device is in substantially the correct place angiographic fluids may be supplied through a hollow elongate catheter  20  in the deployment device to exit through the nose cone  16  so that with the use of angiographic contrast medium the region can be visualised by radiographic techniques. 
     When the deployment device is found to be in the correct position, the sheath  24  of the deployment device is withdrawn to the position as shown in  FIG. 3  at which stage the stent graft  25  is expanded except that the proximal end  27  is retained by a trigger wire retention mechanism to the central catheter  20 . At this stage the pressure of blood flow from the heart will still tend to cause blood flow around the stent graft  25 . 
     Next a trigger wire release mechanism is released so that the proximal end  27  of the prosthesis  25  is allowed to open as shown in  FIG. 4  and the barbs  30  on the proximal end of  27  of the stent graft  25  engage against the wall of the aorta to securely fix the stent graft  25  in the upper end of the descending aorta with the stent graft  25  covering the rupture  7  and essentially closing it off so that blood can no longer flow into the false lumen  10 . Blood can then flow through the stent graft and exit out at the distal end  29  of the stent graft  25 . 
     Next, the first deployment device can be withdrawn and a second deployment device  40  deployed over the guide wire  17 . Alternatively the first deployment device  15  can be withdrawn leaving the sheath  24  and guide wire  17  in place and a second deployment device  40  can be deployed through the sheath  24  and over the guide wire  17 . 
     The second deployment device  40  has a elongate deployment catheter  44  and a nose cone  46  and carries a stent assembly  42  as will be discussed in relation to  FIGS. 8 to 11  and the stent assembly  42  is mounted onto the second deployment device  40  by various arrangements as will be discussed in relation to  FIGS. 12 to 17 . 
     When the second deployment device is in place as shown in  FIG. 4  the sheath  48  of the second deployment device  40  is withdrawn as shown in  FIGS. 5 and 6  so that the stent assembly  42  is exposed and gradually released until it is fully released except where it is retained by a release mechanism  50  just distal of the nose cone  46  as will be discussed in relation to  FIGS. 12 to 17 . There is optionally also a distal retention arrangement  47  at the distal end of the stent assembly. The distal retention arrangement  47  can be released either before or after release of the proximal retention arrangement  50 . The self expanding stents of the stent assembly  42  are allowed to engage against the wall of the true lumen  18  and provide pressure onto the wall particularly where the false lumen occurs to gradually deflate and close off the false lumen as shown in  FIG. 6 . 
     If the stent assembly  42  was not retained at its proximal end just distal of the nose cone  46  then there is a danger that, as the sheath  48  was withdrawn or the stent assembly pushed out of the sheath  48 , its proximal end could fan out and actually turn inside out or at least jamb in an unacceptable position in the descending aorta. This could put unacceptable pressure on the wall of the aorta which could be torn or ruptured. 
     The distal retention arrangement  47  is particularly useful to prevent a too rapid release of the distal end of the stent assembly. 
     The release mechanism  50  can then be released and then the entire second deployment device can be withdrawn to leave the stent assembly  42  in place in the descending aorta  6  as shown in  FIG. 7 . 
       FIG. 7  shows the stent assembly  42  placed distally of the covered stent graft  25  but in an alternative arrangement the stent assembly  42  could be placed so that its proximal end  37  is within the distal end of the stent graft  25 . 
       FIG. 8  shows a first embodiment of a stent assembly  42  for use with the method of the present invention. The stent assembly  42  has a plurality of zig zag self expanding Gianturco type zig zag stents  35  and each apex  36  of the stents is linked to the next stent up or down by flexible links  37 . The flexible links may be wire rings or loops of thread or fibre such as a suture thread. The flexible links enable each stent of the stent assembly to expand separately as the false lumen is deflated which may occur over a period of several days or weeks. The stents provide gradual pressure on the wall of the lumen to close the false lumen and open up the true lumen. It will be realised that different numbers of stents may be used depending upon the nature of the aortic dissection and the length of aorta to be opened and the dimensions of the rupture in the wall of the aorta. 
       FIGS. 9 and 10  show further embodiments of stent assemblies  59  and  61  respectively according to the present invention. In these embodiments bends  60  between the struts  62  of the zig zag self expanding stents  64  are linked by means of a fibre or thread  68  such as a suture thread with the thread knotted to each bend  60  by a knot  66  so that each self expanding stent can act independently of its neighbours. It will be noted that the thread or fibre is knotted alternately to a bend of one stent and then a bend of an adjacent stent to provide a link thread of zig zag configuration. The stent assembly  59  in  FIG. 9  can have up to eight stents with a total length of from 178 mm and a diameter when expanded of 46 mm. The stent assembly  61  in  FIG. 10  has four stents with a total length of 88 mm and a diameter when expanded of 46 mm. A further embodiment may have a length of 132 mm with six stents. In one embodiment the stents may be formed from 0.016 inch diameter stainless steel wire but in other embodiments there may be differing wire thicknesses to vary the radial force applied to the vessel wall. 
       FIG. 11  shows a still further embodiment of the stent assembly of the invention. In this embodiment the stent assembly  70  is formed from a continuous spiral of zig-zag stent  72  with again loops in adjacent spirals joined by a thread  74  such as a suture thread. Again suitable knots may be used to assist with the controlled linking of adjacent portions of the spiral stent. 
     In an alternative embodiment of the invention of a stent assembly according to the invention the stents and the links between the stents may be in the form of a mesh and formed from a biocompatible and biodegradable mesh material so that after it has performed its work of providing a radial pressure onto the wall of the aorta it can biodegrade in the bloodstream. 
       FIG. 12  shows a detailed view of the proximal end of a deployment device with a stent assembly mounted thereon according to one embodiment of the invention and  FIG. 13  shows a detailed cross sectional view of the embodiment shown in  FIG. 12 . 
     The deployment device  40  has a deployment catheter  44  extending to a nose cone  46  at its proximal end. Just distal of the nose cone  46  a mounting and release mechanism  50  is provided to retain the proximal end  43  of the stent assembly  42 . The stent assembly  42  is held in a contracted condition by a sheath  45 . The mounting and release mechanism  50  has a catheter  53  around the deployment catheter  44  with at least one internal lumen  52  through which passes a trigger wire  54 . An aperture  56  opening into the lumen  52  allows a bight  58  of the trigger wire to be exposed. Lengths of thread  57  such as a suture thread are used to fasten each of the apices  51  of the proximal-most stent  47  of the stent assembly  42  separately to the bight  58  of the trigger wire  54 . When the stent assembly is to be finally released the trigger wire  54  is withdrawn and each of the threads  57  are released from the bight  58  so that the proximal end of the stent assembly can open against the vessel wall as discussed with reference to  FIG. 6 . The loops or lengths of thread  57  remain fastened to the apices of the proximal-most stent of the stent assembly. 
       FIGS. 14 and 15  show a detailed view of part of the proximal end of a deployment device and an alternative method by which a stent assembly may be retained onto the deployment device.  FIG. 15  shows the embodiment of  FIG. 14  when the retaining sutures are pulled tight. 
     In  FIG. 14  the deployment device  70  has a deployment catheter  72  extending to a nose cone  74  at its proximal end. Just distal of the nose cone  74  a mounting and release mechanism  76  is provided to retain the proximal stent  78  of the stent assembly  80 . The mounting and release mechanism  76  comprises an enlarged end  82  of a trigger wire sleeve  84  and three trigger wires  86  which loop out of apertures  88  in the enlarged end  82  of a trigger wire sleeve  84 . 
     One process for the loading of the proximal-most stent  78  of the stent assembly  80  to the deployment device  70  is as follows. In this embodiment the proximal stent  78  of the stent assembly  80  has twelve points or proximal bends. 
     In a first stage three equally spaced points  90  are mounted to respective trigger wires  86  by passing the respective trigger wire through the point or bend and then pushing the trigger wire back into the aperture  88 . This holds these three points to the enlarged end  82  of the trigger wire sleeve  84 . A portion of suture thread  92  is then tied with a knot  93  to the next point  94  clockwise from each of the points  90  captured by a trigger wire  86  (clockwise looking from the top—i.e. the proximal end). The suture thread  92  is then threaded clockwise through the next two points  95 ,  96  passing them from the outside inwards. The suture thread  92  is then passed beneath the respective trigger wire  86  and then re-threaded through the points  95 ,  96  in the same alignment as the initial threading. Then suture thread  92  is then tied to the loose end of the suture thread at the knot  93  at the point  94  and the suture thread is pulled tight and knotted three times. Then loose tails of suture thread are then cut short. When threaded this way, the stent points “stack up” neatly as the suture is tightened and the suture loops are short. If they are threaded in the opposite direction, they do not stack neatly, and the suture loops are longer. 
       FIG. 15  shows the suture threads  92  pulled tight and the points  94 ,  95  and  96  neatly stacked. The sheath  98  of the deployment device has been moved up to cover most of the stent assembly leaving only part of the proximal stent  78  exposed. 
     By the arrangement shown in  FIGS. 14 and 15  upon release of the stent assembly the sutures will remain fixed to the points  94  and not cause problem within the blood vessel. Other suturing methods may be devised in which the suture remains with the delivery device. 
       FIG. 14  also shows one method by which the adjacent stents of the stent assembly can be joined for optimal deployment. The proximal stent  78  of the stent assembly  80  has a plurality of struts  100  and bends  102 ,  104  and  106 , for instance, between the struts  100  and the distally adjacent stent  108  has bends  110 ,  112 ,  114 , and  116 , for instance. The link arrangement between the stent  78  and the stent  108  comprises a thread or fibre such as a suture thread  118  which is knotted such as at  120  alternately to a bend  102  of one stent and then a bend  112  of an adjacent stent to provide a link thread of zig zag configuration. Upon endoluminal placement by endovascular deployment the stent assembly  80  is adapted to provided pressure on the wall of the lumen to close off a false lumen in the lumen wall with each stent able to act independently of an adjacent stent. 
       FIGS. 16 and 17  show a detailed view of part of the proximal end of a deployment device and an alternative method by which a stent assembly may be retained onto the deployment device before and during delivery.  FIG. 17  shows the embodiment of  FIG. 16  when the proximal trigger wires are pulled into place. 
     In  FIG. 16  the deployment device  70  has a deployment catheter  72  extending to a nose cone  74  at its proximal end. Just distal of the nose cone  74  a mounting and release mechanism  76  is provided to retain the proximal stent  78  of the stent assembly  80 . The mounting and release mechanism  76  comprises an enlarged end  82  of a trigger wire sleeve  84  and trigger wires  86  which loop out of apertures  88  in the enlarged end  82  of a trigger wire sleeve  84 . 
     The process for the loading proximal stent  78  of the stent assembly  80  onto the deployment device  70  according to this embodiment of the invention is a follows. In this embodiment the proximal stent  78  of the stent assembly  80  has twelve points or proximal bends  101 . 
     For this embodiment the proximal end bends  101  of the proximal stent  78  are joined by a circumferential length of suture thread  102  and knotted  104  to each bend  101  in a similar manner to the joining of adjacent stents lower down the stent assembly  80 . 
     To connect the trigger wire  86  to the proximal stent  78  the trigger wire is extended from the aperture  88  and then passed once around the suture  102  between each bend  101  for four portions between bends. This procedure is shown in  FIG. 16 . The end of the trigger wire is then placed back into the aperture  88 , extended into the nose cone and pulled tight. This draws the lengths of suture material  102  between each bend  101  up to the aperture  88  to give the configuration shown in  FIG. 17 . This operation is repeated for the two other trigger wires  86 . 
     By the arrangement shown in  FIGS. 16 and 17  upon release of the stent assembly the suture thread  102  will remain fixed to the bends  101  and not cause problem within the blood vessel. 
     Throughout this specification various indications have been given as to the scope of the invention but the invention is not limited to any 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.