Abstract:
A stent graft adaptor has an outer graft tube and an inner graft tube with the inner graft tube substantially concentric with and within the outer graft tube. A joining member extends between the inner tube and the outer tube. The s joining member can be a continuous fold of graft material extending from a proximal end of the outer tube to a proximal end of the inner tube. The inner tube has at least one self expanding stent on an outer surface thereof and the outer graft tube has at least one self expanding stent on an inner surface. The outer surface of the outer tube provides a sealing surface to engage against the wall of a vessel and the inner tube provides a sealing surface to engage with a corresponding sealing surface of a stent graft deployed through it. The outer sealing surface can include barbs.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a medical device and more particularly to a medical device for introduction by endovascular techniques. 
       BACKGROUND OF THE INVENTION 
       [0002]    Stent grafts are used for endovascular introduction into the vasculature of a patient. Generally these stent grafts are used to bridge a defect or damaged portion of the vasculature by providing an alternate flow path. Generally the stent graft is placed so that its ends engage on to non-diseased vasculature either side of the damaged portion. Where there are branch vessels extending from the vasculature, side branches can be provided but a side vessel is very small it is usually not practical to provide a side branch. 
         [0003]    In one particular situation when stent grafts are placed into the thoracic region of the aorta, there may be occluded one or more intercostal arteries either because a stent graft has a landing zone where there is an intercostal artery or the intercostal artery exists in the damaged area. 
         [0004]    Occlusion of intercostal arteries can cause temporary or permanent paraplegia and it is an object of this invention to alleviate or prevent the risk of such paraplegia. 
       DISCLOSURE OF THE INVENTION 
       [0005]    In one form therefore, although this may not necessarily be the broadest or only form, the invention is said to reside in a stent graft adaptor comprising an outer graft tube and an inner graft tube, the outer graft tube being substantially concentric with the inner graft tube, the outer graft tube and the inner graft tube defining an annular region therebetween and a joining member extending between the inner graft tube and the outer graft tube and the joining member closing off the annular region to prevent fluid flow through the annular region. 
         [0006]    Preferably an outer surface of the outer graft tube comprises a sealing surface to engage against the wall of a vessel and the inner tube comprises a sealing surface to engage with a corresponding sealing surface of a stent graft deployed therethrough. 
         [0007]    Preferably the inner graft tube comprises at least one self expanding stent on an outer surface thereof and the outer graft tube comprises at least one self expanding stent on an inner surface thereof. 
         [0008]    Preferably the joining member comprises a continuous fold of graft material extending from a first end of the outer tube to a first end of the inner tube. 
         [0009]    Alternatively the joining member can comprise an annular portion of graft material fastened to and extending from an inner surface of the outer graft tube to and fastened to an outer surface of the inner graft tube. In such a situation the annular portion of graft material can extend between the outer tube and the inner tube at a location between the ends of the outer tube and the inner tube. 
         [0010]    Preferably the stent graft adaptor comprises barbs extending outwards from the outer graft tube in use to engage with the wall of a vessel into which the adaptor is deployed. 
         [0011]    Preferably the outer graft tube comprises a diameter of up to 46 mm to fit in most descending aortas and the inner graft tube comprises a diameter of 32 mm to mate with an interference fit into a 34 mm thoracoabdominal device and the outer graft tube comprises a length of about 50 mm. 
         [0012]    In an alternate form the invention comprises a stent graft adaptor comprising an outer graft tube and an inner graft tube, the outer graft tube being substantially concentric with the inner graft tube, the inner graft tube and the inner graft tube defining an annular region therebetween and a joining member extending between the inner graft tube and the outer graft tube and the joining member closing off the annular region to prevent fluid flow through the annular region, the joining member comprising a continuous fold of graft material extending from a proximal end of the outer tube to a proximal end of the inner tube, the inner graft tube comprising at least one self expanding stent on an outer surface thereof and the outer graft tube comprising at least one self expanding stent on an inner surface thereof, whereby an outer surface of the outer graft tube provides a sealing surface to engage against the wall of a vessel and the inner tube provides a sealing surface to engage with a corresponding sealing surface of a stent graft deployed therethrough. 
         [0013]    In an alternate form the invention comprises a stent graft adaptor in combination with an introducer,
       the introducer comprising a pusher, the pusher comprising a proximal end to be introduced into a patient and a distal end, a dilator at the proximal end of the pusher, a first temporary retention arrangement on the pusher distal of the dilator,   the stent graft adaptor comprising an outer graft tube and an inner graft tube, the outer graft tube being substantially concentric with the inner graft tube, the inner graft tube having a first diameter and a proximal end and a distal end, the outer graft tube having a second diameter and a proximal end and a distal end, the first diameter being smaller than the second diameter, a joining member extending between the proximal end of the inner graft tube and the proximal end of the outer graft tube, the inner graft tube comprises one self expanding stent on an outer surface thereof and the outer graft tube comprises at least one self expanding stent on an inner surface thereof, the stent on the inner graft tube being at a distal end of the inner graft tube,   the stent graft adaptor being mounted onto the introducer with the distal end of the inner tube and the stent of the inner tube retained distally of the dilator by the first temporary retention arrangement an the joining member and the outer graft tube distally thereof.       
 
         [0017]    Preferably the stent graft adaptor in combination with an introducer further includes a second temporary retention arrangement distal of the first retention arrangement, the distal end of the outer tube being temporarily retained by the second temporary retention arrangement. 
         [0018]    Preferably the stent graft adaptor in combination with an introducer further comprises barbs extending outwards from the outer graft tube in use to engage with the wall of a vessel into which the adaptor is deployed. 
         [0019]    It will be seen that by this invention there is provided an arrangement which can act as an adaptor for placement of a stent graft and which reduces the amount of landing zone necessary which can potentially give a reduction in the potential for temporary or permanent paraplegia. 
         [0020]    Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis means the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away 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. 
         [0021]    Various stent types and stent constructions may be used in the stent graft of the present invention. In general, the stents may be formed from any material and have any structure that is expandable and has sufficient radial strength to retain its shape. For example, the stents may be balloon expandable or self-expanding stents. The stents may be capable of radially contracting, radially distensible and/or deformable. Self-expanding stents include those that have a spring-like action which causes the stent to radially expand, or stents which expand due to the memory properties of the stent material for a particular configuration at a certain temperature. A preferred self-expanding stent is the Z-STENT®, available from Cook, Incorporated, Bloomington, Ind. USA. 
         [0022]    Any suitable stent material is contemplated including, but not limited to, stainless steel, platinum, gold, titanium, Nitinol™ and other nickel-titanium alloys, MP35N® and other nickel-cobalt alloys, Cobalt L-605™ and other cobalt-chromium alloys, other biocompatible metals, metal-alloys, as well as polymeric stents. 
         [0023]    This then generally describes the invention but to assist with understanding reference will now be made to the accompanying drawings which show preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0024]      FIGS. 1A and 1B  show a first embodiment of stent graft adaptor according to the present invention; 
           [0025]      FIGS. 2A and 2B  show an alternative embodiment of stent graft adaptor according to the present invention; 
           [0026]      FIG. 3  shows the aortic vasculature of a patient including the placement of a thoracoabdominal stent graft and a stent graft adaptor according to the present invention; 
           [0027]      FIG. 4  shows detail of the thoracoabdominal vasculature as shown in  FIG. 3 ; 
           [0028]      FIGS. 5 and 6  show views of an alternative embodiment of a stent graft adaptor according to the present invention in a configuration as it would be loaded on to a delivery device; 
           [0029]      FIG. 7  shows the embodiment of  FIGS. 5 and 6  loaded on to a delivery device; 
           [0030]      FIG. 8  shows the device of  FIGS. 5 and 6  loaded on to a delivery device and constrained for endovascular delivery; and 
           [0031]      FIGS. 9 to 11  show various stages in the deployment of the device of the present invention of the embodiment shown in  FIGS. 5 and 6 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    Now looking at the drawings and in particular  FIGS. 1A and 1B , it will be seen that a stent graft adaptor  10  according to one embodiment of the invention comprises an outer graft tube  12  and an inner graft tube  14 . The inner graft tube  14  is substantially concentric with the outer graft tube and substantially within the outer graft tube. A connecting member  16  joins the outer graft tube from the top  12   a  of the outer graft tube to the top  14   a  of the inner graft tube. Preferably the inner graft tube  14 , the outer graft tube  12  and the connecting member are formed from a single piece of biocompatible graft material. 
         [0033]    The outer graft tube has at least one self-expanding zigzag stent  18  on its inner surface so that it presents an outer sealing surface  20 . Barbs  22  fastened to the stent  18  extend out through the wall of the outer graft tube to engage in to the vasculature of a patient in use to prevent movement of the stent graft adaptor after it has been deployed into the vasculature. 
         [0034]    The inner graft tube  14  has at least one and preferably a number of self-expanding stents  24  on its outer surface so that it presents an inner sealing surface  26 . These self expanding stents can be relatively weak because all they need to do is to hold the inner tube open until a proximal end of a thoracoabdominal device or similar device is placed and expanded into it. 
         [0035]      FIGS. 2A and 2B  show an alternative embodiment of a stent graft adaptor  30  according to the present invention. In this embodiment the adaptor  30  has an outer tube  32  and an inner tube  34 . The inner graft tube  34  is substantially concentric with the outer graft tube  32  and substantially within the outer graft tube  32 . A connecting member  36  joins the outer graft tube with the inner graft tube. The connecting member is an annular portion of graft material fastened to and extending from an inner surface of the outer graft tube to and fastened to an outer surface of the inner graft tube. The connecting member  36  extends between the outer tube and the inner tube at a location between the ends of the outer tube and the inner tube. 
         [0036]    The outer graft tube  32  has at least one self-expanding zigzag stent  38  on its inner surface so that it presents an outer sealing surface  40 . Barbs  42  fastened to the stent  38  extend out through the wall of the outer graft tube to engage in to the vasculature of a patient in use to prevent movement of the stent graft adaptor after it has been deployed into the vasculature. 
         [0037]    The inner graft tube  34  has at least one and preferably a number of self-expanding stents  44  on its outer surface so that it presents an inner sealing surface  46 . These self expanding stents can be relatively weak because all they need to do is to hold the inner tube open until a proximal end of a thoracoabdominal device or similar device is placed and expanded into it. 
         [0038]    The device as shown in either of  FIGS. 1A and 1B  or  2 A and  2 B is in use compressed onto a introducer device to be introduced into the vasculature of a patient. Generally the device of the present invention would be deployed first at a selected position in the vasculature to occlude as few as possible or none of the intercostal arteries and then a thoracoabdominal device deployed so that its proximal end is expanded or expands into the inner tube to provide a proximal seal for the thoracoabdominal device. 
         [0039]      FIG. 3  shows a schematic view of the aortic vasculature of a human body. The vasculature shown comprises an aorta  60  extending from a heart  62  over a thoracic arch  64  to an aortic bifurcation  66  via a descending aorta  67 . At the aortic bifurcation iliac arteries  68   a  and  68   b  extend down to respective femoral arteries  70   a  and  70   b.  From the thoracic arch  64  the brachiocephalic artery  72 , the left carotid artery  74  and the left subclavian artery  76 . In the aorta there are renal arteries  77  and  78  and extending from the aorta a little above the renal arteries are the superior mesenteric artery  79  and the celiac artery  80 . These four arteries can generally be referred to as the pararenal arteries. The aorta  60  is depicted with an aneurism  82  which has occurred in the region of the pararenal arteries and as illustrated, a stent graft has been deployed into the aorta with a distal landing zone  84  in a non-diseased part of the aorta adjacent to the aortic bifurcation  66  to seal the distal end of the stent graft  85 . At the proximal end  86  of the stent graft  85  a stent graft adaptor  90  according to the present invention has been deployed. 
         [0040]    The intercostal arteries which can cause problems with paraplegia are in the region indicated by the bracket  92  and as shown in more detail in  FIG. 4 . 
         [0041]      FIG. 4  shows detail of the thoracoabdominal region shown in  FIG. 3 . The intercostal arteries in this region are shown as  92   a  to  92   d.    
         [0042]    It can be seen that the stent graft  85  has a diameter at its proximal end  86  of about 34 to 36 mm which is a smaller diameter than the diameter of the vasculature in this region and normally there would be placed a further stent graft extending further up the descending aorta  66 . Such a stent graft is shown in part by the dotted lines  94 . 
         [0043]    As can be seen in  FIG. 4  the placement of the adaptor  90  has caused occlusion of the intercostal artery  92   a  but not occlusion of the intercostal arteries  92   b,    92   c  or  92   d.  If an alternative stent graft such as shown by the dotted lines  94  in  FIG. 4  had been placed without essentially overlapping inner and outer tubes to act as an adaptor, then at least three intercostal arteries  92   a,    92   b  and  92   c  would have been occluded and perhaps  92   d  as well depending on the size of the stent graft  94  and this would have considerably added to the risk of paraplegia. 
         [0044]      FIGS. 5 and 6  show an alternative embodiment of a stent graft adaptor  100 . of the present invention which is substantially the same as the embodiment shown in  FIGS. 1A and 1B  but is depicted in  FIGS. 5 and 6  in a condition ready for mounting on an introducer device for deployment into the vasculature of a patient. In this embodiment the same reference numerals will be used as those in  FIGS. 1A and 1B . 
         [0045]    In the ready to deploy configuration shown in  FIGS. 5 and 6  the stent graft adaptor  100  has an outer graft tube  12  is in substantially the same configuration as shown in  FIGS. 1A and 1B  but the connection member  16  extends away from the outer tube  12  and the inner tube  14  is partially inverted so that there is an outer portion  14   b  and an inner portion  14   c  of the inner tubular portion  14 . The stents  18  on the outer tubular portion are in substantially the same positions as shown in  FIGS. 1A and 1B  but in this variation of the embodiment there is only one stent  24  on the inner tubular portion and in the ready to deploy condition this is mounted to the inner tubular portion  14   c  but between the inner tubular portion  14   c  and the outer tubular portion  14   b.  Hence when the stent graft adaptor  100  is finally deployed there will be an inner sealing surface  26  which has a stent at its distal end but on the outside surface of the inner tube  14 . 
         [0046]      FIGS. 7 to 11  show the various stages of mounting the stent graft adaptor of the present invention on to a delivery device and the delivery of that device into the vasculature of a patient. Only part of the delivery device is depicted. The delivery device includes a nose cone dilator  104  mounted on to a guide wire catheter  106  which extends from a pusher  108 . The stent graft adaptor  100  in its ready to deploy condition is mounted on to the delivery device so that the distal end  26  of the inner portion of the inner tube  14   c  and the stent  24  is retained by a retention arrangement  110  just distal of the nose cone dilator  104 . The distal end  28  of the outer tube  12  is retained to the pusher  108  by a release arrangement  112 . 
         [0047]    When the adaptor  100  has been so mounted a constraining sleeve  114  is placed around the device  100  and the sleeve extends forward to the nose cone dilator  104  as shown in  FIG. 8 . 
         [0048]    As shown in  FIG. 9  the introducer has been introduced into the vasculature of the patient and the sheath  114  withdrawn to release the outer tubular portion  12  so that it engages against the wall of the vasculature  60 . This has occluded the intercostal artery  92   a  but not the intercostal artery  92   c.    
         [0049]    Still further in  FIG. 9  the guide wire catheter and nose cone have been retracted with respect to the pusher  108  while the inner tubular portion  14   c  and stent  24  are still retained by the retention arrangement  110  and the distal end  28  is still retained by the retention arrangement  112 . 
         [0050]    As shown in  FIG. 10  the distal retention arrangement has been released so that the guide wire catheter  106  and pusher  108  can be withdrawn together so that the inner tubular portion  14  is moved down to its final position. The outer tubular portion  12  remains essentially in its same position because of the barbs  22  engaging into the wall of the aorta  60 . 
         [0051]    As shown in  FIG. 11  the proximal retention arrangement  110  has also been released so that the stent graft adaptor  100  is completely released from the delivery device  102 . The stent graft adaptor  100  is then positioned so that the outer tubular portion  12  is engaged against the wall of the aorta  60  and the inner tubular portion  14  is substantially concentric with and substantially within the outer tubular portion  12 . 
         [0052]    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 these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation. 
         [0053]    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.