Abstract:
A method and apparatus for repair of AAA uses a graft that is introduced intraluminally and secured through laparoscopic and percutaneous access to the repair site. The arterial graft is a flexible, tubular sleeve that is free of any stent structure. A catheter assembly for delivering the graft includes a removable mechanical expansion assembly that is temporarily expanded to impinge the graft ends against the arterial wall to enable fixation of the graft ends. The fastener assembly for securing the graft includes an inner retention member and a pair of deformable wires extending from the inner retention member. The inner retention member is inserted via needle through the arterial wall and the graft and tension is applied to the wires and the inner retention member pulls the graft end into close impingement with the intimal surface of the vessel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an apparatus and method for repairing an anatomic vessel wall or the wall of a hollow organ or duct, such as the esophagus or aorta, particularly in the human body. More specifically, the invention relates to devices and methods for delivering a vessel graft or other graft endovascularly or endoluminally to a placement site, and thereafter securing the graft using laparoscopic or percutaneous techniques.  
           [0002]    A notable use for the present invention is with regard to an abdominal aortic aneurysm (hereinafter, “AAA”. AAA is a weakening of the wall of the aorta in the abdominal area. Over 160,000 AAAs are diagnosed annually in the United States; one-quarter of AAAs will eventually rupture and, despite many advances in acute medical care, medical transport, and resuscitation, ruptured AAAs continue to have a 50% mortality rate. Thus AAAs comprise a serious health problem for which, arguably, effective treatment has yet to be developed.  
           [0003]    A typical AAA is infrarenal, located below the kidneys and above the bifurcation point where the aorta divides into the iliac arteries. The arterial walls bulge outwardly from their normally generally tubular conformation, the bulging being caused by weakening of the aortic vessel walls. The traditional surgical technique for treating AAA involves excision of the aneurytic tissue and replacement of the tissue with either a synthetic graft or a graft from another portion of the patient&#39;s body. This surgical approach involves a large abdominal incision that dissects major abdominal muscle groups and fascia, and total bowel displacement and large disruption of the retroperitoneum, followed by excision of the aneurytic tissue and attachment of the replacement graft to the vessel ends. This involves a traumatic access through a large incision, with attendant blood loss, and recuperation typically involves several days in the hospital&#39;s Intensive Care Unit and a week or more in the hospital. The manipulation of the bowel and retroperitoneal dissection may result in prolonged ilius, and other detrimental effects such as hypothermia, coagulation problems, a risk of sexual dysfunction, as well as significant pain and disfigurement from the access incision.  
           [0004]    Because of the negative aspects of the otherwise effective open surgical procedure, alternative techniques have been developed in the prior art. An early attempt, transfemoral intraluminal graft implantation for AAA, involved inserting a stent graft through the femoral artery and guiding it to the aneurysm site. Upon proper positioning of the stent graft, the stent was deployed and grafted to the vascular walls of the aorta. The use of stent grafts has decreased patient morbidity and, because of the less invasive nature of the technique used to introduce, deploy, and secure the graft, has significantly reduced the problems involved with the open surgical techniques traditionally used for AAA repair. That is, there is less blood loss, less operative pain, a shorter hospital stay, and quicker healing of the smaller incisions.  
           [0005]    An alternative to open AAA resection is the use of laparoscopic techniques to accomplish the same goal of excising the aneurysm but avoiding the large abdominal incision. Laparoscopic AAA repair has been described in the surgical literature for several years but has failed to gain widespread acceptance due to its extreme technical difficulty and the low safety margin placement.  
           [0006]    It has been proposed to combine the best aspects of the two approaches. Laparoscopic assisted stent-graft placement has been advocated to resolve the problems inherent in both stent-graft placement and fixation.  
           [0007]    Although the use of minimally invasive surgical techniques for fixation of the graft have greatly improved AAA repair procedures, this combination is not free of problems. The fixation of the stent graft within the AAA has engendered complications. One technique for securing a stent graft employs hook-shaped projections extending from the stent at proximal and distal ends and disposed to mechanically grip the interior surface of the vascular wall. These hooks may fail to engage properly, or loosen over time, resulting in migration of the stent graft and failure of the AAA repair. Another approach is to employ hook-shaped retaining elements inserted through a band or bracket at the external surface of the aorta to engage the stent body. Moreover, stent grafts themselves have been shown to have their own drawbacks. The infrarenal aorta is subject to rotation and torsional forces as the upper body rotates with respect to the pelvic girdle, but a stent graft by its very rigidity and stiffness is not capable of accommodating rotational motion. Thus a stent graft secured in a AAA repair is subject to rotational movement, and there is ample opportunity for the proximal or distal graft to loosen in the aorta, resulting in endoleaks that are difficult to access and repair. The presence of the fragile stent structure within the flowing bloodstream also increases the risk of embolization if it should fracture. Likewise, the stent graft may experience kinking, or late migration, or endoleaks, or other failure modes cited by the FDA. Other failure modes listed by the FDA include:  
           [0008]    metallic component fracture due to material fatigue;  
           [0009]    migration of the endograft due to inadequate proximal fixation;  
           [0010]    incidence of type I, II, III, IV endoleaks due to weak radial force and lack of conformability;  
           [0011]    endograft wear holes due to graft/suture/metal interaction (metal to fabric wear);  
           [0012]    kinking of graft limbs due to migration of the endograft;  
           [0013]    loss of complete seal to vessel wall due to the attachment design.  
           [0014]    Among other issues in this regard are the high cost of stent grafts. Furthermore, the size of the introducers for current stent grafts are too large for 40% of AAA patient population, so that only 60% of people can benefit from endovascular repair today.  
           [0015]    It is apparent that the prior art methodolgy and apparatus for AAA repair are in need of further development and improvement.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention generally comprises a method and apparatus for repair of AAA using a non-stented graft that is introduced intraluminally and secured through laparoscopic or percutaneous access to the repair site.  
           [0017]    One significant aspect of the invention is the provision of an arterial graft that is formed of a flexible, tubular sleeve that is free of a conventional stent structure within the lumen thereof. The graft may be formed of a biocompatible material that is woven or otherwise formed in a sleeve-like configuration. The proximal and distal ends may be provided with an outwardly turned sidewall portion forming an annular cuff, and the cuff may be reinforced with one or more annular bands. The annular bands may be spring-biased to expand outwardly to aid in impinging the cuff portions on the intimal surfaces of the aorta.  
           [0018]    (Note: in the following specification, the term “proximal” is used to refer to a direction closer to the patient&#39;s heart, and the term “distal” is used to refer to a direction further from the heart.)  
           [0019]    The invention provides a catheter assembly for delivering the graft to the repair site intraluminally. A significant aspect of the catheter assembly is the provision of a mechanical expansion assembly that may be temporarily expanded to impinge the graft ends against the arterial wall to enable fixation of the graft ends. The expansion assembly includes a proximal end cap that is secured to the proximal end of a central flexible strut, and a plurality of peripheral flexible struts arrayed circumferentially (with respect to the axis of the catheter) about the central strut. The proximal ends of the peripheral struts are not secured to the end cap, but are selectively entrained and captured within the end cap. During insertion of the catheter, the peripheral struts extend generally parallel to the central strut in a collapsed (unexpanded) state. At the repair site, the expansion assembly may be selectively dilated within the deployed graft by withdrawing the central strut distally, causing the end cap to impinge on the proximal ends of the peripheral struts and exert compressional forces thereon that urge the peripheral struts to bow radially outwardly.  
           [0020]    After fixation of the graft, the central strut may be extended proximally to relieve the compressional forces on the peripheral struts. Indeed, the end cap may be freed of its entrainment of the peripheral struts, and the peripheral struts may be withdrawn distally without the end cap. This latter feature enables the peripheral struts to be withdrawn distally from any incidental entanglement or engagement with the fastener devices that extent through the arterial wall to the graft lumen.  
           [0021]    Another important aspect of the invention is the provision of an improved method and apparatus for securing a graft within the lumen of a vessel or hollow organ. The apparatus includes an inner retention member, comprised of a rod-like member having a slight curvature, and at least one, and preferably a pair of deformable wires extending from a medial portion of the inner retention member. The inner retention member is secured within a needle-like delivery device with the wires extending therethrough. The delivery device is adapted to be manipulated and operated by a laparoscopic surgical tool, whereby the needle end may be inserted through the arterial wall and through the cuff of the graft to deliver the inner retention member into the lumen of the graft. Thereafter the needle may be withdrawn, and the inner retention member deployed to impinge on the inner surface of the graft. A laparoscopic tool is then used to twist or wind the wires extending from the inner retention member, whereby tension is applied to the wires and the inner retention member pulls the graft end into close impingement with the intimal surface of the vessel. A plurality of fastener members may be installed to circumscribe the cuff portion of the graft. The inner retention members are oriented generally perpendicular to the axis of the graft, the ends of each inner retention member impinging on the reinforcing bands to distribute the clamping force thereto.  
           [0022]    In an alternative embodiment, one or more outer retention members may be employed to distribute the clamping forces on the exterior surface of the vessel. In one embodiment, a curved outer retention member may be assembled to the retention wires, prior to the winding step, so that the curved member disperses the clamping force about the periphery of the vessel. In a further alternative, an outer retention member may comprise an omega-shaped component that substantially, but not totally circumscribes the vessel.  
           [0023]    In another aspect, the invention provides a sleeve-like graft that is free of any stent structure within the lumen thereof. The graft is formed of a woven biocompatible material, and is provided with reinforcement that increases the longitudinal stiffness of the graft. The reinforcement may include a plurality of pleats extending longitudinally and formed at the exterior surface of the graft, the pleats being angularly spaced about the circumference of the graft. Alternatively, the reinforcement may comprise one or more struts incorporated in the sidewall of the graft. In another alternative, the graft may be reinforced by the inclusion of wire or reinforcing fibers extending longitudinally in the sidewall of the graft.  
           [0024]    It is noted that although the invention is described with reference to repair of AAA, it may be applicable to repair of any body vessel or duct or hollow organ.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0025]    [0025]FIG. 1A is a schematic view of basic aspects of AAA repair using an intraluminally introduced, laparoscopically affixed stentless graft in accordance with the present invention; FIG. 1B is a schematic cross-section of the human abdomen depicting a possible percutaneous access arrangement for AAA repair.  
         [0026]    [0026]FIG. 2 is a cross-sectional view of a catheter formed in accordance with the present invention and proximally disposed in the infrarenal aorta or the like vessel.  
         [0027]    [0027]FIG. 3 is a cross-sectional view as in FIG. 2, showing the end cap extended proximally and the graft partially deployed from the catheter assembly.  
         [0028]    [0028]FIG. 4 is a cross-sectional view as in FIG. 3, depicting the dilation of the mechanical expansion assembly of the catheter assembly, and a plurality of fastener assemblies securing the proximal end of the graft in annular fashion to the vessel wall.  
         [0029]    [0029]FIG. 5 is a cross-sectional view as in FIG. 4, showing the end cap released proximally from the peripheral struts of the expansion assembly.  
         [0030]    [0030]FIG. 6 is a cross-sectional view as in FIG. 5, depicting the proximal ends of the peripheral struts of the expansion assembly withdrawn distally and unfettered by the fastener assemblies extending through the graft.  
         [0031]    [0031]FIG. 7 is a cross-sectional view following FIG. 6, depicting the catheter of the invention proximally disposed at the distal portion of the infrarenal aorta, with the mechanical expansion assembly dilated to expand the graft distal end, and a plurality of fastener assemblies extending through the graft distal end.  
         [0032]    [0032]FIG. 8 is a cross-sectional view as in FIG. 7, showing the end cap of the expansion assembly extended proximally to release the proximal ends of the peripheral struts and collapse the expansion assembly.  
         [0033]    [0033]FIG. 9 is a cross-sectional view as in FIG. 8, showing the catheter assembly withdrawn completely and the distal end of the graft secured annularly to the vessel wall of the distal end of the infrarenal aorta.  
         [0034]    [0034]FIG. 10 is a side view of a fastener assembly loaded into an endoscopic tool, with the jaw in position to deploy the fastener assembly.  
         [0035]    [0035]FIG. 11 is a side view as in FIG. 10 in which the fastener assembly is positioned in the endoscopic tool to be driven to pierce the vessel sidewall and graft sidewall.  
         [0036]    [0036]FIG. 12 is a perspective view of the stentless graft of the present invention.  
         [0037]    [0037]FIG. 13 is an enlarged cross-sectional view depicting one embodiment of the end arrangement of the graft depicted in FIG. 12.  
         [0038]    [0038]FIG. 14 is a perspective view of the stentless graft of the present invention.  
         [0039]    [0039]FIG. 15 is a perspective view of an alternative embodiment of the graft of the invention.  
         [0040]    [0040]FIG. 16 is a perspective view of an alternative embodiment of the graft, a bifurcated docking graft.  
         [0041]    [0041]FIGS. 17A and 17B are perspective and end views of a further embodiment of the graft, a longitudinally pleated graft.  
         [0042]    [0042]FIGS. 18A and 18B are perspective and end views of a further embodiment of the graft, a longitudinally reinforced graft.  
         [0043]    [0043]FIGS. 19A and 19B are perspective views of one embodiment of the mechanical expansion assembly of the present invention, shown in the collapsed (retracted) disposition and expanded disposition, respectively.  
         [0044]    [0044]FIGS. 20A and 20B are perspective views of another embodiment of the mechanical expansion assembly, shown in the collapsed (retracted) disposition and dilated (expanded) disposition, respectively.  
         [0045]    [0045]FIG. 21 is a schematic view showing the placement and fixation of a graft using an external band about the vessel in conjunction with the fastener assemblies.  
         [0046]    [0046]FIG. 22 is a perspective view of one embodiment of the external band of claim  21 .  
         [0047]    [0047]FIGS. 23A and 23B are partial cross-sectional views of a graft secured within a vessel by a fastener member secured externally, without and with an external band or ring.  
         [0048]    [0048]FIG. 24 is an enlarged partial cross-sectional view of one embodiment of the graft fastening assembly of the present invention  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0049]    The present invention generally comprises a method and apparatus for delivering a tubular graft assembly to a damaged vessel or hollow body organ, and for expanding and affixing the graft assembly to the wall of the vessel or organ. With regard to FIG. 1A, an anatomic vessel  31 , in this case a section of the aorta, presents an aneurysm  32  that is to be repaired. To undertake this repair, a catheter assembly  33  constructed in accordance with the invention is introduced into the femoral artery  34  through a surgical cutdown, and advanced proximally to the aneurysm  32 , as is known in the prior art. The catheter assembly transports a graft  35  to the aneurysm site to effect repair thereof. A plurality of access openings  36  are formed in the abdominal wall to provide both visual and mechanical access to the exterior of the vessel  31 . A plurality of surgical instruments  37  are inserted through the openings  36  to carry out fixation of the graft to the vessel wall so that the graft acts as an internal shunt to carry blood flow past the aneurysm and prevents the potential hemorrhage thereof.  
         [0050]    With reference to FIG. 2, the catheter assembly  33  is generally comprised of an outer sheath  41  that is formed of biocompatible material and is flexible yet form-retaining. Disposed concentrically within the sheath  41  is the graft  35 , a tubular, sleeve-like component formed of a flexible, expandable, biocompatible material such as woven polymer filament or the like. The graft is positioned at the proximal end of the catheter assembly  33 , and a drive tube  42  extends distally from the graft  35  and in end-abutting registration therewith, as shown at reference numeral  43 . The graft  35  and tube  42  are slidably disposed within the sheath  41  for selectively independent axial translation therewith. It is noted that the proximal end of the graft  35  includes a cuff portion  44  comprised of the end of the sleeve-like tube of the graft  35  folded retroflexively and distally to impinge on the proximal end of the outer sheath  41 . The graft  35  is placed in the sheath  41  in a radially contracted state, so that the catheter is sufficiently small in diameter to pass through the femoral, iliac, and infrarenal aorta arteries without difficulty. The length of the graft  35  is chosen to exceed the length of the aneurysm  32 , so that the proximal and distal ends of the graft  35  may be expanded to impinge on healthy vascular wall portions proximally and distally of the aneurysm and be fastened thereto. Further description of the graft construction is given below.  
         [0051]    Another significant component of the catheter assembly  33  is a mechanical expansion assembly  51  that is disposed within the lumen of the drive tube  42  and the graft  35 . The mechanical expansion assembly  51  is sufficiently flexible to be accommodated within the catheter assembly and to undergo bending together with the outer sheath  41  and drive tube  42 , and graft  35 . With reference to FIGS. 2 and 19A, the assembly  51  generally includes a flexible confinement tube  52  extending concentrically within the drive tube  42  and dimensioned for selective independent axial translation relative thereto. A flexible strut support  53  extends coaxially through the tube  52 , and terminates at its proximal end at a plurality of peripheral struts  54 . The struts  54  are flexible and bendable, and may be resiliently biased (sprung outwardly) to expand radially. The proximal ends of the struts  54  are free of attachment, whereas the distal ends are secured to the cable support. The struts  54  are generally arrayed in an angularly spaced apart manner within the confinement tube  52 .  
         [0052]    The mechanical expansion assembly  51  also includes an end cap assembly  61  extending proximally from the flexible strut support  53 . The end cap assembly includes a central strut  62  extending in slidable fashion through the flexible strut support  53 , and an end cap  63  is secured to the proximal end of the central strut  62 . In this embodiment, the end cap  63  is secured to the strut  62  by a pair of crimps  64  formed on the strut  62  exteriorly and interiorly of the cap to clamp the cap therebetween. The end cap  63  is shown as a bell-shaped structure, but it may have any configuration that exhibits a blunt, convex proximal surface and an annular, concave distal opening that may receive the proximal ends of the peripheral struts, as will be described below.  
         [0053]    The end cap  63  and confinement tube  52  are substantially similar in diameter, and are initially disposed in end-abutting relationship, as shown at reference numeral  66 . The peripheral struts  54  are retained(confined) in a radially compressed state within the confinement tube  52 , and the proximal ends of the peripheral struts may thus be captured within the concave opening of the end cap  63 .  
         [0054]    In the initial configuration of the catheter assembly  33  as shown in FIG. 2, the catheter assembly is advanced to the site of the aneurysm  32  to effect repair thereof (This process may involve the use of dilators, a guidewire, an introducer sheath, and other tools and techniques known in the art) The catheter is positioned so that the cuff  44  is positioned in axial alignment with a portion of the vessel proximal to the aneurysm  32 . Thereafter, as shown in FIG. 3, the outer sheath  41  is retracted distally to expose a proximal end portion of the graft  35 . Note that the position of tube  42  is unchanged, so that the location of the graft  35  remains unchanged as the tube  41  is withdrawn. Likewise, the tube  52  is withdrawn distally to expose the proximal end portions of the peripheral struts  54 . Note that the proximal ends of the peripheral struts  54  remain engaged in the end cap  63 , the position of which is essentially unchanged.  
         [0055]    In the next step, shown in FIGS. 4 and 19B, the central strut is withdrawn distally, causing the end cap  63  to axially compress the peripheral struts  54 , which bow outwardly in response to the compressive forces applied thereto. The action causes the cuff  44  of the graft  35  to move radially outwardly and impinge forcefully against the intimal surface of the vessel. The cuff  44  is thus expanded and positioned and supported for fastening the cuff to the vessel wall, using fastener assemblies  71  that are described in greater detail in the following specification. The fastener assemblies  71  are introduced through the access ports  36  and installed using laparoscopic or percutaneous surgical tools as described herein. The fastener assemblies are placed annularly about the cuff  44  to form a sealing engagement with the intimal surface of the vessel  31 .  
         [0056]    With reference to FIG. 5, the subsequent step involves urging the end cap  63  proximally by pushing the central strut  62  proximally, while at the same time holding the peripheral struts motionless or withdrawing them slightly distally to free the proximal ends of the peripheral struts  54  from the end cap  63 . This action releases any compressional force applied from the end cap  63  to the peripheral struts, so that the peripheral struts are not driven to bow radially. In addition, this action enables the peripheral struts  54  to be withdrawn distally, as shown in FIG. 6, by retracting the strut support  53  while the tube  52  remains in place. As a result, the peripheral struts are pulled distally past the fastener assemblies  71  and are freed of any incidental entanglements therewith. In addition, the retraction of the peripheral struts  54  within the tube  52  collapses the peripheral struts  54  radially inwardly to fit the confined diameter of the lumen of tube  52 . The consequence of all the steps taken to this point is the fixation of the proximal end of the graft  35  to the interior surface of the vessel  31 .  
         [0057]    Thereafter, the end cap  63  is retracted distally, as at  63   a , so that the concave recess of the end cap is adjacent to the proximal end of the tube  52 . The radially confined ends of the peripheral struts  54  are received in the concave recess of the end cap, whereby the end cap  63 , struts  54 , and tube  52  are returned to approximate the relationship shown in FIG. 2. The entire catheter assembly  33  is then withdrawn distally, with the exception of the drive tube  42 , which remains essentially unmoved. The tube  42  holds the graft  35  in its axial position while the remainder of the catheter assembly moves distally, and eliminates tensile forces acting distally on the graft as the catheter withdraws.  
         [0058]    With regard to FIG. 7, the catheter assembly  33  is shown withdrawn distally into a branching vessel  81 ; e.g., the iliac artery extending from the distal aorta. The distal end  82  of the graft  35  may be provided with a cuff  44 ′ similar in construction to proximal cuff  44 . The mechanical expansion assembly is deployed once again, which involves retracting the tube  52  to expose the struts  54 , and then retracting the central strut  62  to cause the end cap  63  to compress the struts  54  axially and expand them radially. The struts  54  thus urge the cuff portion  44 ′ of the graft  35  against the intimal surface of the vessel  31 , and remain in this expanded disposition while a plurality of fastener assemblies  71  are installed through the wall of the vessel  31  and through the cuff  44 ′. The fastener assemblies  71  are introduced through the access ports  36  and installed using laparoscopic surgical tools and techniques. The fastener assemblies are placed annularly about the cuff  44 ′ to form a sealing engagement with the intimal surface of the vessel  31 .  
         [0059]    Thus the graft  35  is completely installed in the vessel  31 , forming an internal shunt across the aneurysm  32  that carries blood flow past the diseased portion of the vessel and eliminates the opportunity for hemorrhage.  
         [0060]    With regard to FIG. 8, the end cap  63  is disengaged from the proximal ends of the peripheral struts  54  by extension of the central strut  62  proximally. The compressional forces acting on the struts  54  are released, and the radial expansion of the struts  54  is significantly diminished. In addition, the proximal ends of the struts  54 , by virtue of their lack of attachment to any other component, are free to be withdrawn past the fastener assemblies  71  and freed of any incidental entanglements therewith. This action is carried out by retracting the strut support  53  while the tube  52  remains in place. The struts  54  are thus withdrawn distally into the tube  52 , collapsing the struts  54  radially into the lumen of tube  52 . Thereafter, the end cap  63  is withdrawn distally by the central strut  62 , as depicted previously in FIG. 6, so that the catheter assembly  33  is in condition to be withdrawn completely from the vessels  31  and  81 . The result, as shown in FIG. 9, is a completed aneurysm repair. Note that the graft  35  is free of any internal stent or like mechanical structure or framework, and is comprised of a fabric sleeve that is sufficiently flexible to be capable of torsional motion and bending, yet which is sufficiently stiff to resist kinking or collapsing during such flexure.)  
         [0061]    Although the graft of the invention is depicted as comprising a tubular sleeve with cuffs  44  and  44 ′ at opposed ends, the cuffs should be considered additional improvements to the essential tubular sleeve graft. As shown in FIGS. 12 and 13, each cuff  44  and  44 ′ includes an end portion  82  folded retroflexively, and at least one, and preferably a pair, of annular bands  83  are secured between the graft body and the folded end portion  82 . The bands provide reinforcement to the cuff structure, and also serve to distribute the compressive forces applied to the graft by the fastener assemblies  71 . It is preferable to install the fastener assemblies between the axial span of the two bands  83 .  
         [0062]    Furthermore, the annular bands  83  may be formed of a structure that retains radial elastic compression, whereby the bands  83  tend to expand radially when the cuff  44  is released from the outer sheath  41 , as shown for example in FIG. 4. One example of this structure is an annular wire spring or the like, or shape memory alloy components formed in accordance with known techniques to promote radial expansion. As suggested in FIG. 14, the graft  35  is preferably formed of a fabric woven in a tubular configuration and designed to undergo sufficient radial expansion to enable the graft to be transported through a catheter in a collapsed state and expanded, as described above, to engage the sidewall of the vessel.  
         [0063]    With regard to FIGS. 17A and 17B, the graft  35  may be provided with a plurality of pleats  84  formed in the sidewall of the graft and extending longitudinally therealong. The pleats are disposed at essentially equal angles about the periphery of the graft body, and may be secured by sutures extending longitudinally through the gathered sidewall portions, or by thermal or ultrasonic welding of the sidewall material at the gathered portions, or the like. The pleats are provided to enhance the longitudinal stiffness of the graft body. This increased stiffness aids in resisting the outward pressure of the blood flow through the graft, and resists kinking of the graft under torsion or bending forces. It also assists in the process of deploying the graft to its full length within the vessel or hollow organ.  
         [0064]    As shown in FIGS. 18A and 18B, the graft  35  may be augmented with a plurality of reinforcing struts  86  joined to or incorporated within the sidewall of the graft  35 . The struts  86  may comprise wires or flexible rods interwoven in the fabric of the graft body or integrally molded into the graft sidewall. Like the pleats described previously, the struts  86  provide increased longitudinal stiffness to the graft body, and the attendant benefits described above.  
         [0065]    The graft component of the invention may be provided in many different configurations to suit the range of structural formations in which a graft may be installed. For example, as shown in FIG. 15, the graft  135  may comprise a tubular flexible component having a distal, tapered cutout  136 . The graft  135  may be reinforced, if required, by preferably providing a plurality of pleats, as shown in FIG. 17. With regard to FIG. 16, the invention provides a bifurcated graft  235  that is comprised of a flexible tubular body  236  terminating in a split distal end: one elongated tubular leg  237  and one short connector leg  238 . This configuration is shaped to extend through the infrarenal aorta to the iliac arteries, the leg  237  extending into the iliac artery through which the catheter  33  introduces and deploys the graft  235 . Thereafter, another similar catheter is used to introduce and deploy graft extension  239  through the other iliac artery, the end  240  of the extension  239  being shaped to circumscribe and retain the connector leg  238 . This arrangement is designed for situations in which the infrarenal artery does not have sufficient healthy vessel wall to secure any of the grafts described previously.  
         [0066]    With regard to FIG. 20A, there is shown in isolated view a further embodiment of the mechanical expansion assembly  51 ′ of the invention that differs in structure, but not function, from the general description of the assembly  51  given previously and shown in FIGS. 19A and 19B. The end cap  63 ′ is secured to a central strut  62 ′ by welding or other techniques, and crimp structures are absent. A tube  241  is received about the central strut  62 ′, and is provided with a plurality of slits  243  extending from the proximal end of the tube  241  to a point adjacent to the distal end thereof. The slits  243  are spaced angularly and disposed to define a plurality of peripheral struts  54 ′. Each strut  54 ′ thus comprises a longitudinally extending strip portion of the sidewall of the tube  241 , the struts  54 ′ being arrayed in the circumference of the tube  241 . The strut  62 ′ extends coaxially through a thrust tube  242  in slidable fashion, and the tube  242  is itself slidably disposed within a concentric outer tube  52 ′.  
         [0067]    As shown in FIG. 20B, the assembly  51 ′ is expanded by retracting the central strut  62 ′ while also advancing the tube  242  to abut the distal end of tube  241 , whereby the struts  54 ′ are placed in compression between the end cap  63 ′ and the thrust tube  242 . The struts  54 ′ are thus driven to bow radially outwardly, defining a dilated outer diameter that is significantly greater than the collapsed diameter shown in FIG. 20A. This expansion effect is exploited to support the graft end  44  or  44 ′ as described above. Note that the tubes  241  and  242  may be withdrawn distally within the tube  52 ′ to retract the assembly  51 ′ when it is not in use. The tube  241  (and struts  54 ′) may be fabricated from a shape memory alloy (SMA) or stress-induced martensitic (SIM) material, as described for example in U.S. Pat. No. 5,067,957, to enhance the expansion capacity of the struts  54 ′.  
         [0068]    With reference to FIGS. 10, 11, and  24 , the fastener assemblies  71  described previously may be comprised of an internal fastener member  72 , which is a thin, rod-like component formed of a biocompatible material. The member  72  may be provided with a slight longitudinal curvature, or may be resiliently biased to assume a longitudinally curved configuration in a relaxed state. The member  72  is received within the lumen of a needle  73  having a sharp, piercing end  74 . At least one, and preferably a pair of flexible tie connectors such as wires  76  are secured to a medial portion of member  72 , the wires extending distally through the lumen of the needle. A push rod  77  is also disposed within the lumen of the needle  73  with sufficient clearance to be slidably disposed with respect to the needle and the wires  76 .  
         [0069]    As shown in FIGS. 10 and 11, an endoscopic surgical tool  91  includes tool body  92  adapted to be extended through a port in the abdominal wall of the patient, as is known in laparoscopic surgery. The tool includes one jaw provided with a pivoting fixture  93  adapted to secure the needle  73  therein, the push rod  77  extending distally from the needle  73 . The other, opposed jaw  94  is configured to close over the needle  73  and push rod  77 , as shown in FIG. 11, to form a compact assembly that will pass through the surgical port (typically 5 mm or 10 mm diameter) that provides access to the infrarenal aorta or other vessel  31 . In the disposition of FIG. 1, the tool  91  may be used to manipulate the needle end  74  to the external surface of the aorta in registration with the cuff  44  or  44 ′ of the graft of the invention, and may be used to drive the needle end  74  to pierce the vessel wall and graft cuff.  
         [0070]    Thereafter, the jaw  94  may be opened, as shown in FIG. 10, and the fixture  93  is rotated to present the distal end of the push rod  77  in approximate opposition to the jaw  94 . The jaw  94  may then be operated to drive the pusher rod  77  to discharge the fastener member  72  from the needle  73  into the lumen of the graft, as described previously. The needle  73  is then withdrawn from the graft and vessel, restored to the compact configuration of FIG. 11, and withdrawn from the surgical site. The wires  76  remain, extending outwardly from the puncture in the vessel wall.  
         [0071]    As shown in FIG. 23A, the wires  76  may be grasped by another endosurgical tool having pliers-like jaws  75 , and the tool may be rotated repeatedly to wrap the wire  76  about the tool. In this manner the wires  76  may be pulled taut, applying significant tensile force to the fastener member  72  and pulling the graft  35  into close abutment with the intimal surface of the vessel  31 . The pliers-like tool may then be disengaged, so that the rolled portion of wires  76  remains impinging on the external surface of the vessel  31  to retain the fastener member tightly against the graft  35 . The surgeon may employ a simple torque limiting drive mechanism to wind the wires  76 , whereby excessive tension on the wires may be prevented. This process is repeated at selected angular locations along an annulus about the vessel periphery, so that the entire circumference is impinged against the internal vessel surface in a sealing engagement.  
         [0072]    With regard to FIG. 23B, the invention may also provide a curved ring  96  extending about the external surface of the vessel  31 . The ring  96 , which is curved to conform to the curvature of the vessel wall, is introduced into the abdominal cavity and secured about the vessel  31  prior to installation of the fastener assemblies  71 . The needle is driven through the ring  96 , vessel  31 , and graft  35  to deploy the fastener member  72 , as shown in FIG. 21, so that the wires  76  will extend outwardly from the ring  96 . Thereafter, the wires  76  are wound or wrapped as described above to place the wires under tension. The tensile force applied by the wires radially inwardly with respect to the fastener member is applied to the ring  96 , where it is distributed more uniformly about an annular portion of the vessel wall.  
         [0073]    A further embodiment of the ring concept, shown in FIG. 22, provides an omega-shaped member  97  formed of a scrim  98  of flexible material. A reinforcing layer  99  may be applied to the curved portion of the member  97 , which is intended to extend entirely about the external surface of the vessel and provide a pressure distribution effect for the wires extending from the fastener members  72 . The tails  101  of the member  97  may be trimmed to remove excess amounts after the fastening procedures are completed.  
         [0074]    The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching without deviating from the spirit and the scope of the invention. The embodiment described is selected to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as suited to the particular purpose contemplated. It is intended that the scope of the invention be defied by the claims appended hereto.