Abstract:
A method for deploying an endoluminal prosthesis by introducing into a bifurcated vessel a sheath introducer having therein a bifurcated graft with a primary and contralateral limb. The contralateral limb being radially retained independent of the sheath introducer. The graft being positionable by an insertion catheter. When the graft is in position within the vessel, a retaining device about the contralateral limb is broken and the graft takes the shape of the vessel.

Description:
The present application is a continuation of co-copending U.S. application Ser. No. 09/949,813 filed Sep. 12, 2001, now Pat. No. 6,767,358, which is a division of U.S. application Ser. No. 09/405,562 filed Sep. 24, 1999, now Pat. No. 6,287,315, which is a continuation-in-part of U.S. application Ser. No. 09/017,474 filed Feb. 2, 1998, now abandoned, which is a continuation of U.S. application Ser. No. 08/710,460 filed Sep. 18, 1996, now Pat. No. 5,713,917, which is a continuation-in-part of U.S. application Ser. No. 08/549,880 filed Oct. 30, 1995, now Pat. No. 5,591,195. Said U.S. application Ser. No. 09/949,813 is a continuation-in-part of U.S. application Ser. No. 09/525,740 filed Mar. 14, 2000, now Pat. No. 6,334,869, which is a continuation of U.S. application Ser. No. 09/017,474 filed Feb. 2, 1998, now abandoned which is a continuation in part of U.S. application Ser. No. 08/710,460 filed Sep. 18, 1996 now U.S. Pat. No. 5,713,917 which is a continuation-in-part of U.S. application Ser. No. 08/549,880 filed Oct. 30, 1995 now U.S. Pat. No. 5,591,195. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates to blood vessel graft systems for repairing aneurysms, and more particularly to a catheter-based graft system for repairing aortic aneurysms by deploying a graft within a blood vessel via percutaneous entry into a femoral artery of a patient. 
     B. Description of the Prior Art 
     An aortic aneurysm is a very common deteriorating disease typically manifested by weakening and expansion of the aorta vessel wall at a region between the aorto-renal junction and the aorto-iliac junction. Aneurysms affect the ability of the vessel lumen to conduct fluids, and may at times be life threatening, for instance when rupture of the vessel wall occurs. A standard treatment for repairing an aneurysm is to surgically remove part or all of the aneurysm and implant a replacement prosthetic section into the vessel, however such surgery is generally postponed until the aneurysm has grown to a diameter greater than five centimeters. With aneurysms over five centimeters in diameter, the risk of complications is greater than the risks inherent in surgical excision and grafting of the aneurysm. Consequently, aortic aneurysms measuring greater than five centimeters in diameter, and those showing a rapid increase in size, are generally surgically removed and grafted as a matter of course, before rupture occurs. 
     The standard procedure for repairing an aortic aneurysm requires one or two days of preparing the large and small intestines prior to hospitalization. The operation itself generally takes one to three hours to perform, and necessitates several units of blood for transfusion. The patient commonly remains hospitalized for several days following surgery, and requires as much as three months recuperation time before returning to work. Moreover, there remain significantly high rates of mortality and morbidity associated with the standard procedure. The mortality rate is as high as eight percent, while the morbidity rate includes incident complications such as blood loss, respiratory tract infections, wound infections, graft infections, renal failure, and ischemia of the bleeding intestine. The mortality and morbidity rates for this type of major surgery are also often influenced by the fact that the typical aortic aneurysm patient is elderly and therefore less able to withstand major surgery, including anesthesia. 
     Other treatments for repairing an aneurysm involve deploying a graft device at the aneurysm site via a catheter traveling through a femoral artery. Conventional tubular aortic replacement sections, however, are generally considerably larger in diameter than the femoral artery and therefore cannot be inserted through the femoral artery lumen to the site of the aneurysm. Expandable graft devices suitable for catheter delivery and deployment have been proposed, as in U.S. Pat. Nos. 4,140,126 and 4,562,596 by Choudhury and Kornberg, respectively, however the expanding structures of the devices are cumbersome and difficult to operate. 
     U.S. Pat. No. 5,104,399 to Lazarus discloses an artificial graft device having staples at proximal and distal ends thereof for fixing the graft within the vessel, and a catheter-based deployment system including a tubular capsule from which the graft is deployed. The graft is of a preselected cross section and length, and is capable of being substantially deformed so as to accommodate to the interior surface of the blood vessel. 
     The majority of other graft systems, as exemplified by U.S. Pat. Nos. 5,304,220 to Maginot and 5,151,105 to KwanGett, require additional suturing or other methods for securing a graft. Furthermore, once a graft has been placed inside the lumen, adjustment usually requires a major surgical procedure. 
     Furthermore, the prior art stainless steel or elgialloy stent grafts carry high leakage rates. Moreover, high incidence of fractures have been associated with stainless stdel stent grafts. 
     An additional problem with grafts in the public domain is the graft in-folding which causes leakage, migration, and thrombosis. Too, those grafts in the public domain such as U.S. Pat. No. 5,507,771 can provide adequate seals only with straight surfaces due to the spring shape and sealing force. 
     In cases where the aneurysm involves the ipsilateral and contralateral iliac vessels extending from the aorta, it is known to provide a generally Y-shaped bifurcated graft having a primary limb joining with an ipsilateral limb and a contralateral limb. An example of such a graft, and means for surgically implanting same, are described in U.S. Pat. No. 5,387,235 to Chuter. The surgical procedure taught by Chuter involves either surgical isolation of the femoral vessels in the groin to provide direct access to the vessels, or percutaneous entry through both ipsilateral and contralateral femoral arteries. 
     The difficulties involved with traditional surgical procedures and additional complexities associated with securing grafts make the treatment of aneurysms a very expensive and lengthy procedure. Thus, there exists a need for a treatment for aneurysms which requires minimal preparation and outpatient care, and which provides a safe and percutaneous method for deploying a graft capable of remaining in place without additional suturing or stapling for security. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a graft which is deployable percutaneously by low-profile deployment means, and which provides a leak-proof conduit through the diseased region without suturing or stapling. 
     It is another object of the present invention to provide a bifurcated graft deployable through a single entry site. 
     It is yet another object of the present invention to provide an adjustable-length extension graft for coupling with a limb of a previously deployed graft. 
     It is yet another object of the present invention to provide low-profile graft deployment means capable of securely deploying a graft via percutaneous entry. 
     It is yet another object of the present invention to provide deployment means having inflatable and deflatable balloons for modeling a graft spring portion into conforming fixed engagement with the interior surface of a vessel, for dilating a vessel to facilitate insertion, and for controlling blood flow through a vessel during deployment of a graft. 
     It is yet another object of the present invention to establish an improved method for securely deploying a graft with minimal incision. 
     It is yet another object of the present invention to establish a method for implanting a graft with low mortality and low morbidity risks to patients. 
     It is yet another object of the present invention to establish a method for implanting a graft which requires less hospital and outpatient care than required by normal surgical grafting procedures. 
     It is yet another object of the present invention to establish a single-entry method for deploying a bifurcated graft. 
     It is yet another object of the present invention to provide means for easily adjusting or removing an improperly deployed graft. 
     The present invention relates to an aneurysm repair system characterized by a graft apparatus which can be placed percutaneously via deployment means at the location of an aneurysm. It will be understood the term “proximal” as used herein means relatively closer to the heart, while the term “distal”, as used herein means relatively farther from the heart. 
     The graft apparatus of the present invention comprises a tubular graft formed of bio-compatible graft material for conducting fluid, and may be in the form of either a straight single-limb graft or a generally Y-shaped bifurcated graft having a primary limb joining with a pair of lateral limbs, namely an ipsilateral limb and a contralateral limb, at a graft junction. A single-limb extension graft having a mating portion for coupling with a lateral limb of a bifurcated graft and an adjustable length portion extending coaxially from a distal end of the mating portion is also within the scope of the present invention. The graft material, preferably thin wall woven polyester or polytetrafluoroethylene (PTFE), is chosen so that the graft is capable of substantially deforming to conform to an interior surface of the blood vessel, and is preferably tapered through a middle portion of each limb. Other covering materials may be used, however, including micro-porous polyurethane, lycra, or cryogenically preserved explanted veins. The most preferred embodiment for the covering material is Lycra outside with thin PTFE inside at top proximal section with bare nitinol sinusoidal extension for above renal artery fixation. Further, for the aortic section, having aortic wall movement of approximately 3 MMS per heart beat, polyester (Dacron) is the preferred covering material. Moreover, with respect to grafts used in the iliac artery sections, where there is very little wall movement, PTFE is the preferred graft covering material. In the adjustable len portion of the extension graft, the graft material is crimped to permit axial or lengthwise extension and compression thereof. 
     The graft apparatus includes radially compressible spring means, preferably in the form of a nitinol wire spring having a pair of coaxially spaced annular spring portions connected by a connecting bar, for biasing proximal and distal ends of an associated graft limb or limb portion radially outward into conforming fixed engagement with the interior surface of the vessel. In the extension graft, an unpaired annular spring portion is located at a distal end of the adjustable length portion for similar biasing purposes. Each wire spring is enclosed by the graft material and stitched thereto, with cut-out portions being provided between spokes of the wire spring to define a plurality of radially distensible finger portions at the ends of the graft. A distal end of the contralateral limb of the bifurcated graft, and the distal end of the adjustable length portion of the extension graft, are each provided with a retainer ring to retain respective spring portions associated therewith in a radially compressed or loaded condition during deployment. 
     In a preferred embodiment, the graft apparatus further comprises a plurality of outer packets formed of a light degradable polymer and containing a tissue adhesive which is released by fiber-optic scope after the graft is implanted to bond the ends of the graft to the interior surface of the vessel and prevent leakage through micro-cracks therebetween. Medical grade expandable foam cuffs preferably surround the middle portion of the graft to promote clotting within the aneurysm sac. Alternatively, light actuated cryo precipitate fibrin glue may be painted onto the exterior surface of the graft material with a brush. The adhesive naturally remains as syrup until light actuates and cures. This replaces the need for packets and reduces the possibility of premature release of adhesive from packets that may break during deployment. 
     The deployment means of the present invention generally comprises an elongated sheath introducer having an axially extending sheath passage for slidably receiving the graft and maintaining the graft and associated spring means in a radially compressed pre-loaded condition prior to deployment of the graft within the vessel lumen, an elongated insertion catheter received within the sheath passage and pre-loaded graft for use in guiding the graft to the location of the aneurysm and deploying the graft within the vessel lumen at such location, and a flexible condensing spring push rod slidably arranged about the insertion catheter and received within the sheath passage to abut with the graft for navigating through tortuous vessels and pushing the graft out of the sheath passage during deployment. Deployment means may also comprise a micro-emboli filter tube selectively slidable over the sheath introducer and having controllable renal and iliac filters which may be opened to catch thrombus dislodged into the blood stream. 
     In one embodiment the push rod comprises a helical coil member. The push rod in this embodiment has a continuously variable stiffness so that the push rod may move flexibly throughout a tortuous vessel with minimal kinking of the sheath or other portions of the delivery system. 
     The insertion catheter of the present invention includes an embedded kink-resistant nitinol core wire and three inner tracks extending lengthwise thereof. A first inner track opens at both a near end and a remote end of the insertion catheter for receiving a guidewire to guide the insertion catheter through the vessel lumen. A second inner track opens at the near end of the insertion catheter for allowing fluid communication with an inflatable and deflatable tip balloon located at the remote end of the insertion catheter for dilating the vessel ahead of the graft and controlling blood flow through the vessel during placement. A third inner track opens at the near end of the insertion catheter for allowing fluid communication with an inflatable and deflatable graft balloon located near the remote end of the insertion catheter generally for securing the graft spring means against the interior surface of the vessel during graft deployment. 
     An optional spool apparatus may also be incorporated into the deployment means for collapsing a deployed graft and reloading the graft into sheath introducer  106  if unexpected leakage is observed due to incorrect graft position or size. The spool apparatus is connected to the sheath introducer and includes a plurality of suture loops wound around a spool cylinder and arranged to extend through a central axial passage of the push rod and around respective crests of a distal spring portion of the graft. A hand crank enables rotation of the spool cylinder to collapse the distal spring and pull it to within the sheath introducer, and a blade is provided on the spool apparatus for cutting each suture loop at one point to permit removal of the suture material if repositioning or removal of the graft is unnecessary. 
     A method of surgically implanting a pre-sized single limb graft to repair a previously-mapped aortic aneurysm using the deployment means of) the present invention may be summarized as follows, keeping in mind that fluoroscopic or other monitoring means known in the art may be employed throughout the procedure. 
     First, a guide wire is introduced into the vessel via a femoral percutaneous entry and progressively inserted until a remote end of the guide wire extends upward past the aorto-renal junction, and the insertion catheter with surrounding pre-loaded graft, push rod, and sheath introducer are caused to follow the guidewire through the vessel lumen using the first inner track of the insertion catheter until the tip balloon is above the aorto-renal junction. The tip balloon may be partially inflated during insertion of the deployment means to dilate the vessel for easier introduction, and once properly positioned, may be inflated further so as to obstruct blood flow in the aorta just above the aorto-renal junction. With aortic blood flow obstructed, the insertion catheter is rotated so that the sheath introducer and compressed graft therewithin are best aligned to match the bends in the patient&#39;s aorta. Next, the spring portion associated with the proximal end of the graft is observed for correct axial alignment within the vessel at a location just below the aorto-renal junction. 
     Once proper positioning and alignment of the apparatus are observed, the sheath introducer is withdrawn a short distance while holding the push rod in place to release the proximal spring portion of the graft from within a remote end of the sheath passage and allow it to expand radially outward to conform with the interior surface of the vessel, with verification being made that the proximal spring portion continues to be in correct position. The operator may remove the guidewire from the first inner track and inject contrast media into the first inner track, or may place an ultrasound imaging catheter, for purposes of visualization. Next, the insertion catheter is moved upward within the vessel to align the graft balloon to within the proximal spring portion of the graft, and the graft balloon is inflated with relatively high pressure to fixedly model the proximal spring portion against the interior surface of the vessel. The sheath introducer may now be withdrawn further to fully deploy the graft, including the distal spring portion, which should be located at a healthy region below the aneurysm. 
     Blood flow may then be gently introduced to the graft by slowly deflating the tip balloon. The graft balloon may be repeatedly deflated, moved incrementally along the central axis of the graft, and re-inflated to smooth out any wrinkles in the graft material. When the graft balloon has traveled down the graft to within the distal spring portion, it may again be inflated at a relatively high pressure to fix the distal spring in conformance with the inner surface of the Vessel. If it is observed that the graft is not in its intended position, the spool apparatus of the present invention may be used to reload the graft within the sheath introducer. 
     Once the graft is correctly deployed, the deployment means may be completely withdrawn from the patient, and a fiber-optic scope inserted through the entry site to direct light at the tissue adhesive packets to cause the packet polymer material to degrade, thereby releasing the tissue adhesive. Finally, the entry site attended using standard procedure. Post-operative imaging may be conducted to verify isolation of the aneurysm, with particular attention being given to the occurrence of leaks at the proximal end of the graft closest to the heart. 
     The present invention also relates to a single-entry method of surgically implanting a pre-sized bifurcated graft in cases where mapping of the aneurysm indicates involvement of one or both iliac vessels. 
     Deployment of the bifurcated graft is carried out by a method similar to that used to implant a single-limb graft, except that additional procedures are required to properly implant a contralateral limb of the bifurcated graft within a contralateral iliac vessel. As the sheath introducer is withdrawn to deploy the primary leg of the graft within the aorta, the contralateral limb of the graft will be released from the sheath introducer when the sheath introducer has been withdrawn just past the graft junction, such that the contralateral limb of the graft is within the aneurysm sac or directed downward into the contralateral iliac vessel. The retainer ring at the distal end of the contralateral limb prevents premature expansion of the spring portion associated with such end to permit proper positioning of the contralateral limb within the contralateral iliac vessel. 
     Positioning of the contralateral limb is carried out using the insertion-catheter and a deflectable guide wire inserted within the first inner track of the insertion catheter and having an inflatable and deflatable tip balloon at a remote end thereof. First, the graft balloon is deflated and the insertion catheter with inserted deflectable guide wire are withdrawn to the graft junction. A dial control may be used to deflect the remote end of the guide wire and direct it into the contralateral limb of the graft; the guide wire is then advanced deep into the contralateral iliac vessel and the tip balloon thereof is inflated to anchor the guide wire within the vessel. With its own tip balloon partially inflated, the insertion catheter is advanced along the anchored guide wire into the, contralateral limb of the graft. The insertion catheter tip balloon is then inflated more fully to allow flow direction of blood to carry graft material of the contralateral limb down the contralateral iliac vessel. The contralateral limb is moved to a final desired location by deflating the insertion catheter tip balloon and advancing it to within the spring portion at the distal end of the contralateral limb held by the retainer ring, partially reinflating the tip balloon to hold the distal end and associated distal spring portion of the contralateral limb by friction, advancing the insertion catheter into the contralateral iliac vessel until the distal end of the contralateral limb is at the desired location, and finally reinflating the tip balloon fully to expand or break the retainer ring and release the spring portion. The deployment means may then be withdrawn and removed from the entry site and the entry site attended using standard procedure. 
     If the extent of disease indicates that a longer graft limb is necessary in either or both iliac vessels, an adjustable length extension graft may be coaxially coupled to a lateral limb, for instance the contralateral limb, of the bifurcated graft by the following procedure. 
     The extension graft is deployed via percutaneous entry through the contralateral femoral artery. A guide wire is directed through the contralateral limb and up into the primary limb of the bifurcated graft, and deployment means carrying a pre-loaded extension graft is directed over the guidewire to position the mating portion of the extension graft partially within the contalateral limb of the bifurcated graft such that a first spring portion at the proximal end of the mating portion is overlapped by the spring portion at the distal end of the contralateral limb. The sheath introducer may then be withdrawn while the push rod is held stationary to deploy the first spring portion, the insertion catheter moved upwards to locate the graft balloon within the first spring portion, and the graft balloon inflated to conform the first spring portion to the interior surface of the contralateral limb. Contrast media is injected through the first inner track of the insertion catheter to verify that the coupled graft limbs are not leaking. Next, the sheath introducer is further withdrawn to release a second spring portion defining a junction between the mating and adjustable-length portions, and a third spring portion at a distal end of the adjustable-length portion the radially retained distal annular spring of the adjustable length portion, into the contralateral iliac vessel. The graft balloon is then deflated and moved downward to within the third spring portion, and partially re-inflated to hold the distal end of the adjustable-length portion by friction. This permits the distal end of the adjustable-length portion to be positioned generally just above the sub-iliac or hypo-gastric branch by withdrawing the insertion catheter downward. The third spring portion is deployed by fully reinflating the graft balloon therewithin to expand or break the surrounding retainer ring and fix the third spring portion in conformance with the interior surface of the vessel. Any wrinkles in the extension graft may be removed using the graft balloon. Finally, once leakage has been ruled out, such as by angiogram verification, the deployment means may be withdrawn and the entry site attended. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature and mode of operation of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings wherein: 
         FIG. 1  is an elevational view showing a single-limb graft of the present invention fully deployed within an aorta of a patient to repair an aneurysm; 
         FIG. 2  is a view similar to that of  FIG. 1 , however showing an optional anchor spring attached to the graft for suprarenal fixation of the graft; 
         FIG. 3  is an elevational view showing a bifurcated graft of the present invention fully deployed within an aorta and lateral iliac vessels joined therewith; 
         FIG. 4  is a view similar to that of  FIG. 3 , however showing an extension graft of the present invention for coupling with a lateral limb of the bifurcated graft; 
         FIG. 5  is a perspective view showing graft deployment means of the present invention; 
         FIG. 5A  is an elevational view of an alternative embodiment of a push rod of the present invention. 
         FIG. 5B  is an exploded elevational view of the push rod of  FIG. 5A ; 
         FIG. 6  is a sectional view thereof taken generally along the line  6 — 6  in  FIG. 5 ; 
         FIG. 7   a  is a perspective view showing a spool apparatus of the present invention; 
         FIG. 7   b  is an enlarged partial view of circled portion A in  FIG. 7   a  showing the arrangement of a suture loop of the spool apparatus; 
         FIG. 8  is an elevational view showing a micro-emboli filter tube of the present invention in an activated condition; 
         FIGS. 9   a - 9   d  are a series of elevational views illustrating a method of deploying a single-limb graft in accordance with the present invention; 
         FIGS. 10   a  and  10   b  are elevational views illustrating a method of deploying a bifurcated graft in accordance with the present invention; and 
         FIG. 11  is an elevational view illustrating a method of deploying an extension graft for coupling with a lateral limb of a bifurcated graft in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , there is shown an aorta  10  joined by renal arteries  12  and  14  at aorto-renal junction  16 , and having an aneurysm  18  below the aorto-renal junction characterized by a weakened and expanded vessel wall at the diseased region. In accordance with the present invention, an elongated single-limb tubular graft  20  is deployed at the region of aneurysm  18  as a prosthetic device for the purpose of relieving blood flow pressure against the weakened vessel wall by acting as a fluid conduit through the region of the aneurysm. In its deploye condition, graft  20  defines a central longitudinal axis  22  extending in a direction of blood flow through aorta  10 , and generally comprises a deformable graft material  24  enclosing radially compressible spring means  26  for biasing a proximal end  28  and a distal end  30  of the graft into conforming fixed engagement with an interior surface of aorta  10 . 
     Graft material  24  is a biocompatible, flexible and expandable, low-porosity woven fabric, for example thin-walled polyester or PTFE, capable of substantially deforming to conform with an intrior surface of aorta  10 , and additionally capable of acting as a fluid conduit when in tubular form. A middle portion  29  of graft  20  between proximal end  28  and distal end  30  is tapered to provide a decreased fluid-conducting cross-sectional area relative to ends  28  and  30 , such as by excising at least one longitudinal strip of graft material  24  and sewing the resulting gap or gaps closed, as a way of reducing the occurrence of folding and wrinkling and adapting the graft to fit within a wider range of differently sized vessels. 
     Enclosed within graft material  24  is a nitinol wire spring having a proximal spring portion  34  and a distal spring portion  36 . Alternatively, the proximal spring portion  34  may have uncovered portions or open areas proximal of the graft material so that in the event the spring portion  34  is deployed over the renal arteries  12 ,  14 , the blood flow through arteries  12 ,  14  will not be blocked. Spring portions  34  and  36  are designed to exert radially outward force of approximately 240 to 340 grams for biasing graft material  24  at graft ends  28  and  30  into conforming fixed engagement with the interior surface of aorta  10  above and below aneurysm  18 . The nitinol wire used to form the spring is in a super elastic, straight annealed condition and may be coated with titanium oxide to improve biocompatibility, reduce the incidence of allergic reaction to nickel, and improve radiopacity. A PTFE coating may also be used to lower the risks of blood clotting and wire corrosion. As a further preventive measure, the coating may be treated with iridium 192 or other low dose Beta radiation emitting substance to reduce post-surgical cell proliferation in the vessel which can lead to closure of the vessel. Spring portions  34  and  36  are each formed by revolving a sinusoidal wire pattern of straight spokes  38  connected by rounded alternating crests  40  and troughs  42  about central axis  22  to provide a continuous annular spring portion. A preferred spring portion includes five equistaced crests  40  and five equispaced troughs  42  formed to a predetermined radius to produce better spring properties and avoid sharp transitions in the wire, in that sharp transitions are more prone to failure. The coaxially spaced spring portions  34  and  36  are connected by at least one straight connecting bar  44  which preferably extends generally parallel to central axis  22  for minimal disruption of blood flow. Connecting bar  44  provides torsional stability for graft  20 , and may be welded to spring portions  34  and  36 , or fastened thereto by a small tightened sleeve (not shown). 
     The wire spring is sewn within graft material  24  using polyester suture. Prior to sewing, graft material  24  is arranged to surround the wire spring and is heat pressed to conform to spring portions  34  and  36  using an arcuate press surface (not shown) heated to approximately 150 degrees Fahrenheit and corresponding in curvature to the spring portions. A preferred stitch pattern includes two generally parallel stitches extending along opposite sides of the wire, and a cross-over stitch around the wire for pulling the parallel stitches together to achieve tight attachment of graft material  24  to the wire spring. This method of attachment substantially prevents contact between wire spring and the interior surface of the vessel, and is reliable over time. In accordance with the present invention, graft material  24  is cut out between crests  40  of proximal spring portion  34  and distal spring portion  36  to define a plurality of radially distensible finger portions  46  at graft ends  28  and  30 . Importantly, finger portions  46  allow graft  20  to be situated with proximal end  28  much closer to aorto-renal junction  16  than was possible with prior art graft constructions, since gaps between the finger portions may be aligned with renal arteries  12  and  14  so as not to block blood flow. Moreover, finger portions  46  may be radially compressed to approximate a conical tip to facilitate loading insertion of graft  20  within a sheath introducer, to be described hereinafter. As shown in  FIG. 2 , a bare nitinol wire anchor spring  48  may be used to provide increased positional integrity to graft  20  where healthy vessel neck between aorto-renal junction  16  and aneurysm  18  is particularly short. Anchor spring  48  includes a proximal spring portion  50  set approximately 20 mms above aorto-renal junction  16  for suprarenal fixation remotely of graft proximal spring portion  34 , and a distal spring portion  52  sewn within graft middle portion  29  and connected to proximal spring portion  50  by at least one axially extending connecting bar  54 . The provision of radially distensible finger portions  46  and optional anchor sprinc  48  render the present invention useful in a much greater patient population relative to prior art graft systems, in that only about 5 mms of healthy vessel neck below the aorto-renal junction is required as compared with about 20 mms for prior art graft systems. 
     Graft  20  further includes a plurality of releasable tissue adhesive packets  56  fixed to an exterior surface of graft material  24  at ends  28  and  30  for establishing a fluid tight seal between graft material  24  and the inner wall of aorta  10 . Packets  56  may be constructed of photosensitive polyurethane and filled with bio-compatible tissue adhesive, for example fibrin glue or isobutyl  2  cyanoacrylate. The tissue adhesive remains secure during deployment, and may subsequently be released by directing a fiber-optic catheter light source at packets  56  from inside graft  20  to cause breakdown of the packet material. Tissue adhesive enters and occupies small micro-cracks existing between graft material  24  and the interior surface of aorta  10  to form a bonding fluid seal, thereby preventing the serious problem of leakage. An alternative to the described tissue adhesive packets is the use of light activated cryo precipitate fibrin glue painted on the exterior surface of the graft material. 
     In addition to tissue adhesive packets  56  at ends  28  and  30 , one or more cuffs  58  comprising medical-grade expandable foam may be provided to surround middle portion  29  to promote clotting in the space of the aneurysm outside of graft  20 . In a preferred embodiment, first and second cuffs expandable to approximately 4-10 mms greater than the graft diameter are arranged near spring portions  34  and  36 , and a third cuff expandable to approximately 10-40 mms greater than the graft diameter is arranged intermediate the first and second cuffs. Cuffs  58  preferably include fetal endothelial cells, smooth muscle cells, or other living tissue cells and glioma growth factor in their respective foam matrices or light activated foaming particles to encourage healing near spring portions  34  and  36  and filling of aneurysmal sac  18  around middle portion  29 . 
     A bifurcated graft  60  as shown in  FIG. 3  is also within the scope of the present invention for use in cases where involvement of one or both iliac vessels  11  and  13  is indicated. Graft  60  is Y-shaped and includes a primary limb  62  for location within aorta  10 , and is joined by an ipsilateral limb  64  for location within ipsilateral iliac vessel  11 , and by a contralateral limb  66  for location within contralateral iliac vessel  13 , at a graft junction  63 . Each limb of bifurcated graft  60  is generally similar in construction to single-limb graft  20  in that the proximal and distal ends of each limb are biased into conforming fixed engagement with the interior surface of a corresponding vessel by annular spring portions associated therewith, and middle portions of each limb are preferably tapered. A first nitinol wire spring is enclosed by, and attachably sewn within, graft material  24  and includes a proximal spring portion  68 A associated with a proximal end of primary limb  62 , a distal spring portion  68 B associated with a distal end of primary limb  62 , and an axially extending connecting bar  68 C coupling the proximal and distal spring portions together. Similarly, a second nitinol wire spring having a proximal spring portion  70 A, a distal spring portion  70 B, and an axially extending connecting bar  70 C, is sewn within ipsilateral limb  64 ; and a third nitinol wire spring having a proximal spring portion  72 A, a distal spring portion  72 B, and an axially extending connecting bar  72 C, is sewn within contralateral limb  66 . Terminal ends of bifurcated graft  60 , namely the proximal end of primary limb  62  and the distal ends of lateral limbs  64  and  66 , are provided with radially distensible finger portions  46  as described above. Where entry is to be made through an ipsilateral femoral artery to deploy graft  60 , distal spring portion  72 B is held in a radially compressed condition by an expandable retainer ring  79 , which may simply be a length of suture material tied end to end using a purse-string type knot to form a loop, to prevent premature deployment of distal spring portion  72 B prior to proper positioning thereof within contralateral iliac vessel  13 . Likewise, where entry is to be made through a contralateral femoral artery, distal spring portion  70 B may be provided with a retainer ring  79  to prevent premature deployment of distal spring portion  70 B prior to proper positioning thereof within ipsilateral iliac vessel  11 . It will be understood that previously described tissue adhesive packets  56  and foam cuffs  58 , while not shown in  FIG. 3 , may be incorporated into bifurcated graft  60 . Specifically, packets  56  are preferably provided at least at the proximal end of primary limb  62  to prevent leaking, and foam cuffs  58  are preferably provided around the primary limb for filling aneurysmal sac  18 . 
     A single-limb extension graft  80 , as depicted in  FIG. 4 , embodies another useful apparatus of the present invention. Extension graft  80  is designed for end-to-end coupling with a lateral limb of bifurcated graft  60 , for example contralateral limb  66 , and generally includes a mating portion  82  and an adjustable length portion  84  extending coaxially from a distal end of the mating portion. Mating portion  82  includes a wire spring having a first spring portion  88 A serving to bias a proximal end of mating portion  82  into conforming fixed engagement with an interior surface of contralateral limb  66 , and a second spring portion  88 B connected to first spring portion  88 A by a connecting bar  88 C serving to bias a distal end of mating portion  82  and a proximal end of adjustable length portion  84  into conforming fixed engagement with the interior surface of contralaterai iliac vessel  13 . An unpaired third spring portion  90  is provided at a distal end of adjustable length portion  84  to bias such end against the interior surface of contralateral iliac vessel  13 , and is maintained in a radially compressed condition prior to deployment by a breakable retainer ring  91  similar to retainer ring  79 . Third spring portion  90  is movable in opposite axial directions to a desired location during deployment by virtue of a crimped length of graft material provided in adjustable length portion  84 . 
     As will be appreciated by those skilled in the art, the above described grafts  20 ,  60 , and  80  may be manufactured in a range of seizes for fitting within differently sized vessels to repair aneurysms of various lengths. 
     A preferred apparatus of the present invention for deploying a graft within a blood vessel is depicted in  FIGS. 5 and 6  and identified generally by the reference numeral  100 . Deployment means  100  is elongated to permit delivery of a graft carried thereby to aneurysm  18  via percutaneous entry into a femoral artery of the patient, and may be described as having a near end  102  normally remaining outside the skin of the patient for manipulation by an operating surgeon, and; a remote end  104  normally traveling inside the blood vessel lumen during deployment and carrying a graft to be implanted at aneurysm  18 . Deployment means  100  includes an elongated sheath introducer  106  having an axially extending sheath passage  108 ; an elongated insertion catheter  110  loosely received within sheath passage  108 ; and an elongated compression spring push rod  112  slidably mounted over insertion catheter  110  and received within sheath asage  108 . 
     Sheath introducer  106  is formed of a low-friction, flexible material, preferably F.E.P., however polyurethane, silicone, polyethylene, or other similar materials may be substituted for PTFE. The size of sheath introducer  106  is chosen based on the size of the graft to be deployed so as to hold the graft within a remote end of sheath passage  108  in a radially compressed, pre-loaded condition prior to deployment of the graft within the vessel, with sizes 12 FR, 14 FR, 16 FR, 18 FR, and 20 FR being suitable in a vast majority of instances. Graft finger portions  46  can be pushed together to approximate a conical tip for easier insertion of graft  20  within sheath passage  108 , a feature which has resulted a 2 FR reduction in sheath introducer profile relative to loading a similar graft without finger portions  46 . In order to permit viewing of a pre-loaded graft to confirm proper loading, sheath introducer  106  is preferably transparent. Sheath introducer  106  is equipped with at least one latex-lined hemostasis valve  114  at a near end thereof serving to form a fluid seal around push rod  112  to prevent blood from leaking out of the patient at the entry site. A side port means  116  is provided for transporting fluid, such as heparinized solution or contrast media, into sheath passage  108  and eventually into the blood vessel. Side port means  116  includes a manually operable valve  118  communicating with sheath passage  108  through a flexible tube  120  and adapted to receive a suitable fluid injection means (not shown). 
     Insertion catheter  110 , which may be formed of 8 FR catheter tubing, is longer than sheath introducer  106  to permit near and remote ends thereof to extend from sheath introducer  106  when the insertion catheter is received within sheath passage  108 . As seen in the cross-sectional view of  FIG. 6 , insertion catheter  110  is provided with an embedded, kink-resistant nitinol core wire  122 , a first inner track  124 , a second inner track  126 , and a third inner track  128 , all extending lengthwise thereof. Referring once again to  FIG. 5 , a first end port means  130  for transporting fluid to first inner track  124  includes a threaded adapter  132  for mating with suitable fluid injection means (not shown) and communicating with a near end of first inner track  124  through a flexible tube  134 . A second end port means  136  for transporting fluid to second inner track  126  includes a manually operable valve  138  communicating with a near end of the second inner track through a flexible tube  140  and adapted to receive a suitable fluid injection means  142 . Similarly, a third end port means  144  for transporting fluid to third inner track  128  includes a manually operable valve  146  communicating with a near end of the third inner track through a flexible tube  148  and adapted to receive a suitable fluid injection means  150 . 
     In a preferred form of the invention, core wire  122  is gradually tapered from a diameter of 0.031 inches at the near end of insertion catheter  110  to a diameter of 0.020 inches at the remote end of the insertion catheter. This feature provides that the near end of insertion catheter  110  is strong, and the remote end of the insertion catheter is less likely to cause puncture or rupture of the vessel yet will not deflect significantly under force of blood flow. In addition to providing kink resistance and strength to insertion catheter  110 , core wire  122  provides greatly improved torsional rigidity, whereby rotation at the near end of insertion catheter  110  about its longitudinal axis translates into a substantially equivalent rotation at the remote end of the insertion catheter, such that a graft may be easily rotated during deployment for proper alignment. 
     In accordance with the present invention, second inner track  126  communicates with a transparent polyurethane tip balloon  152  arranged circumferentially about insertion catheter  110  at the remote end thereof, while third inner track  128  communicates with a transparent polyurethane graft balloon  154  arranged circumferentially about insertion catheter  110  in the vicinity of tip balloon  152 . Balloons  152  and  154  are preferably of the same outside diameter or profile when fully inflated, with graft balloon  154  being longer than tip balloon  152 . Balloons- 152  and  154  behave in a pressure compliant manner, such that the profile thereof may be continuously and reversibly varied by changing inflation pressure using fluid injection means  142  and  150 , respectively. Fluid injection means may be a syringe having a slidable plunger for observably varying a plenum volume of the syringe, and the plenum volume may be functionally correlated with balloon profile diameter. A preferred inflation fluid is filtered carbon dioxide, which is readily visualized by X-ray observation. 
     Insertion catheter  110  further includes a tapered head  156  adjacent tip balloon  152  for providing a rigid vessel dilator characterized by a smooth atraumatic transition from an 8 FR profile of the insertion catheter to a larger profile of sheath introducer  106 . Tapered head  156  preferably defines an annular abutment lip  158  arranged to engage the remote end of sheath introducer  106  to prevent withdrawal of the tapered head to within sheath passage  108 . Insertion catheter  110  may also be provided with a plurality of circumferential radiopaque markings (not shown) equispaced along the length thereof to assist in location of the insertion catheter during deployment of a graft. 
     Push rod  112  is a metallic compression spring having a combination of flexibility and axial compression strength to enable it to follow the path of a tortuous vessel without losing its ability to act as a push rod for exerting force against a graft during deployment. Push rod is sized with inner clearance relative to insertion catheter  110  and outer clearance relative to sheath introducer  106  so as to be independently movable within sheath passage  108 . A plunger  162  is preferably arranged at remote end of push rod  112  for stopping blood flow within sheath passage  108 . Push rod  112  may also include dampening means near its remote end, such as a thin heat-shrunken polyolifin or polyimid coating, to dampen undesirable recoil of the push rod. 
       FIGS. 5   a  and  5   b  illustrate another embodiment of a push rod apparatus to be used in place of push rod  112  as part of deployment means  100 . Push rod  312  comprises a handle  313  located towards the proximal or near end  102  of the deployment means  100 , coupled to a push rod body  317 , which is in turn coupled to a helical coil portion  320 . A cup  322  is located at the distal end of the helical coil portion  320  for containing the distal portion of the stent held within the sheath passage  108 . 
     The handle  313  includes a luer adaptor  314  for coupling with a Tuohy Borst connector (not shown), a lumen  315  extending through the handle  313  for receiving insertion catheter  110 , and a female connecting portion  316  for receiving push rod body  317  and push rod stiffener  318 . 
     The push rod body  317  extends distally or remotely of the handle  313  and is made of a polymer material such as polyethylene. Push rod body  317  has lumen  319  extending through the body for receiving the introducer catheter  110  and push rod stiffener  318 . Push rod stiffener  318  and push rod body  317  are coupled to the handle  313  through female connecting portion  316 . Push rod stiffener  318  provides further support for the flexible push rod body  317 , during deployment of the graft. The handle  313  is used in deploying the graft by holding the graft in place while the sheath covering the graft is retracted. 
     The distal end of the push rod body  317  is coupled to the helical coil portion  320 . The helical coil portion  320  is preferably made of a helically wound metal material such as stainless steel. The helical coil portion  320  includes an inner spring  323  threaded inside the helical coil portion  320  at the juncture between the helical coil portion  320  and the push rod body  317 . The inner spring  323  provides for a transition in stiffness between the relatively stiffer push rod body  317  and the more flexible helical coil portion  320 . The inner spring  323  provides a relatively smooth or continuous transition in stiffness from the push rod body  317  to the helical coil portion  320 . In this embodiment, the transition occurs from a stiffer push rod body to a more flexible coil. 
     At the distal end of the helical coil portion  320 , a cup  322  is threaded into the lumen  321  through the helical coil portion  320 . The cup opening  327  is arranged to receive the distal portion of the graft contained within the sheath passage  108 . The cup portion  322  acts to minimize kinking of the sheath that occurs because of the discontinuity in stiffness between the push rod and the graft. The cup portion  322  enables the push rod  312  and graft to act as one unit during deployment. Other means for holding or containing the prostheses are contemplated by this invention. This would include any structure that holds the prosthesis in a position adjacent the push rod so that the push rod and prosthesis act relatively as a unit during deployment or so that kinking of the sheath is decreased. Examples of such structures may include hooks ribbons, wires and posts that engage either the inner or outer lumen of the prosthesis. 
     Helical coil portion  320 , inner spring  323 , and cup  322  have lumens  321 ,  325 ,  326  respectively therethrough. Lumens  321 ,  325 ,  326 ,  315 , and  319  provide a continuous opening for receiving insertion catheter  110 . 
       FIGS. 7   a  and  7   b  illustrate an optional spool apparatus  170  provided as part of deployment means  100  for collapsing a deployed graft and reloading the graft into sheath introducer  106  if unexpected leakage is observed due to incorrect graft position or size. Spool apparatus  170  is mounted adjacent a near end of sheath introducer  106  by a mounting arm  172 , and includes a plurality of suture loops  174  wound around a spool cylinder  176  thereof and arranged to extend through a central axial passage of push rod  112  and around respective crests  40  of a distal spring portion of the graft, as depicted in  FIG. 7   b . A hand crank  178  and releasable pawl (not shown) are provided for rotating and fixing spool cylinder  176  of spool apparatus  170 . A blade  180  is mounted on the body of the spool apparatus for selectively and simultaneously cutting each suture loop  174  at one point to enable removal thereof. Where optional spool apparatus  170  is provided, plunger  162  at the remote end of push rod  112  must be omitted to permit suture loops  174  to connect with the distal spring portion of the graft. 
       FIG. 8  shows a micro-emboli filter tube  182  available for use with deployment means  100  of the present invention for trapping thrombus dislodged during manipulation of deployment means  100  within the vessel. Filter tube  182  is adapted to slide over sheath introducer  106  and includes a renal filter  184  and an iliac filter  186 . Filters  184  and  186  are of similar construction and include a plurality of flexible spokes  188  defined by a series of axially extending slits spaced around the circumference of filter tube  182 . Nylon mesh fabric  190  is affixed around the bottom portion of spokes  188 , such that when filter tube  182  is axially compressed by pushing a near end thereof while a remote end thereof is held in place by inflated tip balloon  152 , spokes  188  flex radially outward to form mesh fabric  190  into a bowl-shaped filter for trapping thrombus entering through gaps between the upper portions of spokes  188 . The near end of filter tube  182  may be pulled while the remote end remains fixed to collapse filters  184  and  186  in preparation for the removal of filter tube  182  from the patient. 
     Reference is now made to  FIGS. 9   a - 9   d , which illustrate a method of surgically deploying single-limb graft  20 . It is assumed that necessary mapping of the vessel and aneurysm  18  have been performed, and that an appropriately sized graft  20  has been selected and pre-loaded within a remote end of sheath passage  108  of appropriately sized deployment means  100 . It is further assumed that certain equipment used for monitoring and visualization purposes is available for use by a surgeon skilled in the art, including a freely positionable C-arm having high resolution fluoroscopy, high quality angiography, and digital subtraction angiography capabilities. 
     As an initial step, the largest femoral artery, left or right, is determined by placing a high flow pig tail angiography catheter (not shown) through a percutaneous entry site in aorta  10  above aorto-renal junction  16  and taking an angiogram; the pig tail catheter is left in place. A flexible guide wire  200  preferably having a tip balloon (not shown) at its remote end is introduced into the vessel via a percutaneous entry site in the larger femoral artery, and progressively advanced upward until its tip balloon is above aorto-renal junction  16 . Deployment means  100 , pre-filled with heparinized solution through side port means  116 , may then be introduced through the femoral entry site and caused to follow guide wire  200  by inserting a near end of the guide wire into first inner track  124  via first end port means  130 , and slowly advancing deployment means  100  upward to the site of aneurysm  18 . During advancement of deployment means  100  along guide wire  200 , it is advantageous to maintain tip balloon  152  partially inflated with carbon dioxide for brighter visualization and atraumatic dilation of the vessel. In order to verify the position of renal arteries  12  and  14 , contrast media is injected through first end port means  130  to the remote end opening of first inner track  124  above the renal arteries. At this point, deployment means  100  should be positioned such that proximal spring portion  34  is at or just below renal arteries  12  and  14 , and distal spring portion  36  is above the bifurcated aorto-iliac junction and not within aneurysm  18 . Blood flow through the region can be obstructed by inflating tip balloon  152  more fully using fluid injection means  142  so as to occlude aorta  10 , as depicted in  FIG. 9   a . With aortic blood flow obstructed, deployment means  100  is rotated so that sheath introducer  106  and compressed graft  20  carried thereby are best aligned to match the bends in the patient&#39;s aorta. 
     Deployment of proximal spring portion  34  is initiated by withdrawing sheath introducer  106  a short distance, approximately 3.5 cm, while simultaneously holding push rod  112  stationary. The finger portions  46  associated with proximal spring portion  34  will distend as the proximal spring portion is released from within sheath passage  108 , and will appear as shown in  FIG. 9   b . Insertion catheter  110  is then advanced upward to position graft balloon  154  within recently deployed proximal spring portion  34 , and the position and alignment of the proximal spring portion relative to renal arteries  12  and  14  is verified by further injection of contrast media through first end port means  130 . Once proper verification has been made, graft balloon  154  is inflated to a relatively high pressure to create a smooth vessel wall seat for proximal spring portion  34  and forcibly model the spring portion into conforming fixed engagement with the interior surface of aorta  10  without causing inelastic deformation of the spring portion, as can be seen in  FIG. 9   c.    
     With inflated graft balloon  154  reinforcing fixation of proximal spring portion  34 , sheath introducer  106  is further withdrawn to a point just before that which is required to release distal spring portion  36  from within sheath passage  108 . Once verification has been made that distal spring portion  36  is not going to block either ipsilateral iliac vessel  11  or contralateral iliac vessel  13 , sheath introducer may be withdrawn a distance sufficient to release distal spring portion  36  from within sheath passage  108 , as depicted in  FIG. 9   d.    
     Blood flow may then be gently introduced to the newly deployed graft  20  by slowly deflating the graft balloon  154  in small increments. Graft balloon  154  may be repeatedly deflated, moved downward through graft  20  by increments of approximately 2 cm, and re-inflated to smooth out any wrinkles in graft material  24 . After graft balloon  154  has traveled downward through graft  20  to within distal spring portion  36 , it may again be inflated to a relatively high pressure to fix the distal spring portion in conformance with the interior surface of the vessel. As will be appreciated, expandable foam sleeves  58  (shown in  FIG. 1  only) surrounding middle portion  29  act to promote clotting in an around aneurysm  18 . 
     If graft  20  is observed to be incorrectly placed and optional spool apparatus  170  has been provided, hand Crank  178  thereof may be rotated very slowly in a counterclockwise direction as viewed in  FIG. 7   a  to collapse distal spring portion  36  of graft  20  and reload graft  20  back to within sheath passage  108 . The sheath may be pushed upward during reloading of graft  20  to reestablish an abutment seal between annular abutment lip  158  of tapered head  156  and the remote end of sheath introducer  106 . Deployment means  100  may then be gently withdrawn, preferably after partially inflating tip balloon  152  with contrast media, such as carbon dioxide, for visualization. Verification that the removal process has not caused rupture of the vessel or embolization should be undertaken by way of an angiogram through the previously placed pig tail catheter. 
     Once graft  20  is correctly deployed, deployment means  100  and guide wire  200  may be completely withdrawn from the patient and the entry site attended using standard procedure. Where optional spool apparatus  170  is used, suture loops  174  may be removed by cutting them with blade  180  and rotating hand crank  178  in a counterclockwise direction. Tissue adhesive may then be released from light-degradable packets  56  (shown in  FIG. 1  only) by insertion of a fiber optic catheter (not shown) through the femoral artery to graft  20  and direction of light at the packets, thereby helping to bond the graft to the vessel and seal micro-cracks which are a source of leakage. Post-operative CAT scan and ultrasound imaging may be conducted to verify isolation of the aneurysm, with particular attention being given to the occurrence of leaks at proximal spring portion  34  closest to the heart. 
     Referring now to  FIGS. 10   a  and  10   b , a single-entry method for deploying bifurcated graft  60  in accordance with the present invention is procedurally similar to the method described above with regard to single-limb graft  20 , however additional steps are necessary to deploy contralateral limb  66  within contralateral iliac vessel  13  with the help of a deflectable-tip guide wire  206  used in place of regular guide wire  200  and having a controllable balloon  208  at a remote end thereof. Bifurcated graft  60  is pre-loaded into sheath passage  108  with contralateral limb  66  folded alongside primary limb  62 , such that as sheath introducer  106  is withdrawn past graft junction  63  subsequent to deployment of proximal spring portion  68 A, contralateral limb  66  unfolds generally into aneurysm  18  or the mouth of contralateral iliac vessel  13 , as shown in  FIG. 10   a . Retainer ring  79  prevents premature expansion of distal spring portion  72 B, thereby enabling distal spring portion  72 B to be moved within contralateral iliac vessel  13  to a proper position for deployment. 
     To position distal spring portion  72 B, graft balloon  154  is deflated and insertion catheter  110  with inserted deflectable guide wire  206  are withdrawn to the graft junction  63 . A dial control (not shown) may be used to deflect the remote end of guide wire  206  and direct it into contralateral limb  66  of graft  60 . Guide wire  206  may then be advanced deep into contralateral iliac vessel  13 , and tip balloon  208  inflated sufficiently to fix the guide wire within the vessel. With its own tip balloon  152  partially inflated, insertion catheter  110  is advanced along fixed guide wire  206  into contralateral limb  66  between proximal spring portion  72 A and distal spring portion  72 B, after which the insertion catheter tip balloon  152  is inflated more fully to allow flow direction of blood to carry graft material  24  of the contralateral limb downward into contralateral iliac vessel  13 . The distal end of contralateral limb  66  is moved to a final desired location by deflating the insertion catheter tip balloon  152  and advancing it to within distal spring portion  72 B held by retainer ring  79 , partially and carefully re-inflating tip balloon  152  to hold distal spring portion  72 B by friction without breaking retainer ring  79 , advancing insertion catheter  110  further into contralateral iliac vessel  13  until the distal end of cotitralateral limb  66  is at the desired location, and finally reinflating the tip balloon to a pressure sufficient to expand or break retainer ring  79  and release distal spring portion  72 B, as shown in  FIG. 10   b . Deployment means  100  may then be withdrawn and removed from the patient and the entry site attended using standard procedure. 
     A method of coaxially coupling extension graft  80  to contralateral limb  66  in accordance with the present invention is once again similar to the method described above with regard to single-limb graft  20 . While the present method is described herein for coupling extension graft  80  with contralateral limb  66 , it will be understood that a similar procedure may be followed to deploy extension graft  80  in coupled relation with ipsilateral limb  64 . 
     Referring to  FIG. 11 , extension graft  80  is deployed via percutaneous entry through the contralateral femoral artery. A guide wire  200  having a controllable tip balloon  202  is advanced upward through contralateral limb  66  and into primary limb  62  of previously deployed bifurcated graft  60 , and deployment means  100  carrying pre-loaded extension graft  80  is directed over guide wire  200 , again using first inner track  124 , and advanced to a position wherein mating portion  82  of extension graft  80  is partially within contralateral limb  66 , preferably with first spring portion  88 A of mating portion  82  overlapped by distal spring portion  72 B of bifurcated graft  60 . Sheath introducer  106  is then withdrawn while push rod  112  is held stationary in order to release first spring portion  88 A. To set first spring portion  88 A into conforming coupled engagement with an interior surface of contralateral limb  66 , insertion catheter  110  is advanced upwards to locate graft balloon  154  within first spring portion  88 A, and the graft balloon is inflated to a relatively high pressure. Contrast media may then be injected as previously described to verify that the coupled graft limbs are not leaking. 
     Next, sheath introducer  106  is further withdrawn to successively release second spring portion  88 B and third spring portion  90  from sheath passage  108 , with third spring portion  90  remaining in a compressed condition due to retainer ring  91 . Graft balloon  154  is then deflated and moved downward to within third spring portion  90 , and partially re-inflated to hold the third spring portion by friction, with care being taken so as not to overinflate graft balloon  154  and expand or break retainer ring  91 . This permits the distal end of adjustable length portion  84  to be positioned generally just above the sub-iliac or hypogastric branch by further withdrawing insertion catheter  110 . Third spring portion  90  is deployed by inflating graft balloon  154  therewithin to a relatively high pressure sufficient to expand or break surrounding retainer ring  91 , as depicted in  FIG. 11 , and fix the third spring portion in conformance with the interior surface of contralateral iliac vessel  13 . Any wrinkles in extension graft  80  may be removed using graft balloon  154  as previously described herein. Finally, once leakage has been ruled out, such as by angiogram verification, deployment means  100  may be withdrawn from the patient and the entry site attended. 
     It is contemplated herein that the delivery system of the present invention and in particular the aspects regarding the flexible, compressible push rod may be used in deploying other endoluminal prostheses where the prosthesis is retained in the shaft of a catheter for delivery to an endoluminal site. Endoluminal prostheses which terms are herein intended to mean medical devices which are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring or artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed, each providing a uniquely beneficial structure to modify the mechanics of the targeted luminal wall.