Abstract:
A bifurcated stent graft for animal or human implantation and method of delivery thereof. The device stent graft employs a first component having an axial passage communicating with the axial cavities of a second leg and longer first leg. A separate leg extension is engageable to the second leg. A first catheter engages the first component for translation to the implantation site and a second catheter engaged with the first is provided with a prepositioned guide wire inside the second leg which may be employed to easily position a guide wire for engagement of the second leg with the leg extension.

Description:
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/903,253 filed Feb. 22, 2007. 
    
    
     FIELD OF THE INVENTION 
     The disclosed device relates to an endovascular prosthesis and implantation method therefor. More particularly it relates to a device and method for implantation of a bifurcated endoprosthesis for repair of infrarenal abdominal aortic aneurysms commonly known to those skilled in the art as AAA&#39;s. 
     BACKGROUND OF THE INVENTION 
     An aneurysm is a type of disease that affects the arteries and is manifested by a localized widening or enlargement of an artery compared to its normal size. Because of the potential of rupture of the artery in question, any aneurysm is a serious health problem and risk to a patient. When a blood vessel with an aneurysm ruptures, life-threatening bleeding generally is the result. Even prior to such an occurrence, aneurysms can also cause pain from pressure on nearby organs or nerves and on occasion, debris within the aneurysm can dislodge and thereafter be communicated through the circulatory system of the patient to the legs or vital organs. The result is generally a blocking of the blood flow to these tissues and resulting harm to organs and tissues remote to the aneurysm itself. 
     A common location for aneurysms is in the abdominal aorta, which is one of the largest blood vessels in the body and located in the abdominal region of the body. A rupture of such a large blood vessel has dire and life threatening consequences to the individual suffering such a crisis. Such abdominal aortic aneurysms (AAA&#39;s) most often involve the infrarenal aorta which is the portion of the blood vessel that lies below the takeoff of the arteries to the kidneys (renal arteries). About half of AAA&#39;s also involve the iliac arteries in the pelvis. The major risk associated with AAA&#39;s is that they have a high propensity to rupture and currently such ruptures are the 13th leading cause of death in the United States. Therefore, early detection and timely repair are paramount to the patient. 
     Current medical practice which is least invasive to the patient employs endovascular repair or stent grafting, in a procedure which is performed through small incisions in each groin. While carrying many of the same risks as invasive surgical repair, patients usually spend fewer days in the hospital and recover more quickly with less pain with the implantation of an endovascular prosthesis. 
     In a procedure to implant the prosthesis, a bifurcated stent graft is positioned within the aneurysm to provide a new conduit for blood flow through the damaged portion of the blood vessel. This effectively seals off the diseased and bulging portion of the aorta from the blood flow and eliminates the potential for rupture. 
     A common endoprosthesis for repair of an AAA is a two-piece bifurcated endovascular graft which is positioned to line the aorta within the aneurysm and has a first portion adapted to engage within the aorta, which communicates with two graft conduits, and which extends from below the renal arteries into both iliac arteries. Material such as ePTFE (expanded polytetrafluoroethylene) forming this fluid conduit for blood flow is commonly inert when implanted. A structural metallic component known generally as a stent is engaged in a skeletal arrangement with the material to maintain the formed conduits for blood flow in an expanded condition once implanted. 
     Delivery and implantation of the device to the site of the aneurysm in the abdominal aorta is generally done by assembly of two component sections which include the trunk with a cuff adapted to engage the contralateral leg. The trunk portion has a large diameter adapted to engage within the large internal diameter of the aorta and is implanted to a position just below the renal arteries. Extending from the trunk and having an internal conduit in communication with the internal passage of the trunk portion is the ipsilateral leg which is positioned in communication within one of the iliac arteries when deployed. The trunk and first leg are conventionally formed and deployed as a unitary structure. The cuff also extends from the trunk portion and, as noted, is adapted for engagement to the second leg which is positioned once engaged within a second of the iliac arteries. The engagement of the contralateral leg with the cuff and positioning of its distal end within the other of the iliac arteries completes the stent graft. 
     This two-piece construction yields is required because of the nature of the engagement of the two legs from the trunk into two different iliac arteries. However, assembly of these two components inside the body of the patient during surgery can be a vexing task to even the most experienced and knowledgeable surgeon. This is because the visual display depicting the components during assembly is a two-dimensional video visualization of a three-dimensional communication between the components of the implant and the two iliac arteries in their junction to the aorta. These arteries generally engage with the aorta at angles radial to the axis of the aorta which must be accommodated during the engagement of the contralateral leg portion with the short extending cuff from the trunk portion. 
     Currently, the trunk portion and first leg portion are advanced using a catheter and guide wire through an incision in one of the femoral arteries. Once inserted into a femoral artery, the trunk and extending first leg and cuff are advanced over the guide wire to the proper position at the juncture of the aorta and renal arteries. During this translation into the aneurysm, the trunk, cuff, and ipsilateral leg are held in a compressed state at the distal end of the catheter by a restraining mechanism which can at a chosen time be released by controls positioned outside the patient&#39;s body to allow the stent graft to enlarge to its expanded state, thereby engaging within the vessel at the appropriate point. Once proper positioning is determined by the surgeon using radiopaque markers and fluoroscopic visualization of the distal end of the first catheter, a control mechanism communicating with the restraining mechanism is activated. This allows for enlargement of the trunk and first leg in their respective positions in the aorta and iliac artery. 
     It is at this point in the procedure that the surgery can become uncertain as to duration and an ongoing source of frustration to the surgeon. Attachment of the second or contralateral leg to the distal end of the cuff portion extending from the trunk is achieved by translating a guide wire from the second leg artery which must be visually guided into the aperture at the distal end of the cuff extending from the trunk. Once so positioned, the contralateral leg may be translated over the guide wire and into proper position relative to the cuff and enlarged to engage the contralateral leg to the cuff. 
     While this may sound like a simple procedure in principle, in practice it is both frustrating and can be extremely time consuming. The extra time in the operating room and uncertainty as to operation duration impacts the surgery schedules for subsequent surgeries. Additionally, during this engagement process of the contralateral leg to the cuff, the patient remains under anesthesia, exposed to continual x-ray radiation, and subjected to continued manipulation of the guide wire inside the vessel adjacent to the cuff. Since there is usually extensive clot and atherosclerotic plaque within the aneurysm, such manipulation entails the additional risk of dislodging debris within the lumen of the aneurysm, thereby also raising the risk of such debris traveling to branch arteries of the aorta. 
     The primary problem in this engagement step arises from the wide variance of intersecting angles of the radially extending iliac arteries from the aorta. The resulting angles of the graft legs may be highly divergent from the axis of the trunk. However, in the two-dimensional visualization provided by the fluoroscope, the surgeon is visually hindered in the attempt to thread the guide wire into the aperture at the distal end of the cuff. An additional factor complicating wire passage into the cuff is that the cuff is usually near the center of the large cavity formed by the aneurysm which in many cases can exceed 10 cm in diameter. The engagement of a small diameter cuff positioned in the midst of such a comparatively large space with the aid of only two-dimensional imaging, while concurrently contending with the highly variable angles of approach from the iliac arteries, renders the procedure very unpredictable. 
     Further, in many cases the angles leading to the iliac arteries from the aorta are such that the surgeon will choose to cross over the first leg and contralateral leg in an overlapping arrangement to maintain a continuous curve for blood flow and to avoid kinks. When graft legs are crossed, attempts at passage of a wire from the second iliac artery into the cuff may additionally be complicated by interference from the first leg which, when positioned in the cross-leg deployment format, will lie across the opening from the second iliac artery into the aorta. Even highly trained surgeons with years of experience can become bogged down trying to thread the guide wire into the aperture of the cuff using the two dimensional visualization and overlapping of images available on the fluoroscopic screen. Absent a lucky positioning of the guide wire, such an exercise can consume an inordinate amount of time. 
     As such, there exists an unmet need for a bifurcated endoprosthesis which can be more easily assembled from components to repair aortic aneurysms. Such a device should allow for conventional deployment of the trunk portion and first extending leg and cuff in a relatively conventional fashion to facilitate easy adoption of the device and procedure. However, such a device and method should provide a means to eliminate the frustration and time-consuming step requiring the surgeon to fish with the distal end of a second guide wire for the aperture of the cuff extending from the trunk portion. In this fashion implantation surgeries for such devices may be expedited and performed with a reasonably accurate estimate of duration, and patients undergoing such surgeries will benefit from shortened procedures and be spared exposure to prolonged radiation. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings nor the steps outlined in the specification. The invention is capable of other embodiments and of being practiced and carried out in various ways as those skilled in the art will readily ascertain from reading this application. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other methods and systems for carrying out the several purposes of the present invention of a device and method for implanting a bifurcated prosthesis in an aortic aneurysm. It is important, therefore, that the claims be regarded as including such equivalent construction insofar as they do not depart from the spirit and scope of the present invention. 
     OBJECTS OF THE INVENTION 
     An object of this invention is the provision of a bifurcated prosthesis for repair of aortic aneurysms. 
     An additional object of this invention is the provision of such a prosthesis which may be assembled from multiple components with ease and in a much reduced duration from a conventionally available device. 
     Yet another object of this invention is to provide a plurality of means to restrain the implantable prosthesis in a compressed state such that controlled release of the restraining mechanism employed is achievable. The restraint system allows for incorporation of a novel component adapted for capture of an additional guide wire into the overall apparatus in a manner optimizing function of the device. 
     Yet another object of this invention is the provision of a method of implantation of such a device which pre-positions the guide wire employed for engagement of a second leg to the trunk portion of the device, thereby eliminating the time-consuming task of fishing for the cuff aperture. 
     Another object of this invention is to provide a method of capturing a secondary guide wire during assembly of a bifurcated stent graft procedure and guiding it into a targeted aperture using a snare or other capture means which may be engaged to a catheter which will slide on the prepositioned guide wire. 
     Yet another object of this invention is to provide a device and method of secondary guide wire capture and guide to a target aperture by provision of a catheter and snare combination and pre-positioned second, or escort, catheter. 
     These together with other objects and advantages which will become subsequently apparent reside in the details of the construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout. 
     SUMMARY OF THE INVENTION 
     The device and method herein feature a modular bifurcated vascular prosthesis which is assembled in the artery of a patient from a plurality of components adapted for mutual engagement and placement within a diseased aorta to provide a new conduit for blood flow therethrough. 
     As currently practiced, attempts to engage the contralateral cuff portion of the graft with a guide wire commence after the graft is deployed. As previously mentioned, this is encumbered by several factors, notably the small size of the target within a large aneurysm cavity, variably complex angles of approach imposed by iliac artery orientation relative to the axis of the aorta, and possible interference from the deployed long leg of the graft when a crossed-leg deployment is chosen. 
     The device and method disclosed herein obviates these difficulties through employment of several novel strategies and structures. Firstly, the time-consuming and unpredictable requirement of current art to maneuver a direct wire passage from the second iliac artery into the cuff after deployment of the device is eliminated. Instead, a maneuver is substituted which provides for easy capture of a guide wire from a catheter introduced from a second iliac artery by provision of means for capture of its distal end in a positive mechanical engagement. 
     Because of the manipulation of the device and captured guide wire subsequent to capture, it is especially important that the capture be secure until the surgeon decides to release that capture. This capture device in a current preferred mode employs a snare. The snaring function is enabled by a novel device which is a key component of the overall apparatus. The device, also referred to as the “escort catheter” in the text, is a narrow diameter, semi-rigid catheter having a central coaxial lumen allowing for passage of a second guide wire therethrough over which the catheter can be translated, and which second guide wire can be pre-positioned inside the cuff portion extending from the main trunk of the stent graft. 
     Also incorporated into the escort catheter is an eccentric lumen the proximal end of which lumen is accessed through a locking, rotatable valve attached externally near the back end of the escort catheter. The distal end of the eccentric lumen communicates with an aperture in the wall of the escort catheter some distance from the distal tip of the escort catheter. A snare wire passes through the locking valve, runs within the eccentric lumen, and has its tip tethered to the catheter wall at the aperture. Forward translation of this wire extrudes a desired length of wire from the aperture, the extruded length assuming the shape of a snare loop, projecting orthogonally to the axis of the catheter. Loop formation and its orthogonal projection are aided by incorporation of pre-shaped memory into the wire. 
     The snare loop can be closed by retraction of the wire, and held securely in the closed position by locking the rotating valve around the wire. The escort catheter is depicted in  FIG. 2 , and  FIG. 2   a  illustrates the incorporation of this catheter into the shaft of the main delivery catheter, the function of this integrated unit being detailed elsewhere in the text. Extending from this escort catheter is the second guide wire which is pre-positioned inside the cuff of the graft during assembly. This second guide wire thereby provides a pre-positioned guide for translation of a captured third guide wire directly into the cuff portion of the device. 
     Additional utility and benefit to the patient is provided by the fact that this capturing maneuver is transferred to a location within the vascular system far more favorable than the center of a large aneurysm cavity. Specifically, capture of the third wire from a second catheter is executed at the confluence of the two iliac arteries as they converge at the bottom of the aneurysm. The second catheter with the third guide wire introduced from the second iliac artery is predictably engaged by the snare loop of desired dimension and shape which projects across the opening of the iliac artery. This arrangement exploits the inevitable convergence of the second catheter and its guide wire and the snare-bearing device engaged with the delivery catheter from the first iliac artery. 
     Further utility in the disclosed device is provided through the incorporation of the positioning or escort catheter in a translatable communication through the graft-bearing delivery catheter. Such a collinear engagement provides the surgeon freedom of orientation of the snare loop at the opening of the second iliac artery by translation and rotation of the catheter assembly to optimally position the snare for capture of the second guide wire. 
     Still further, after capture of the third guide wire extending from the second catheter, the entire engaged apparatus can be translated and rotated at will, thereby enabling the surgeon to provide precise graft positioning as well as rotational orientation for crossing the legs of the device to whatever degree is dictated by patient anatomy. Such maneuvers can be executed without risk of loss of the captured third guide wire because of the security conferred by design of the snare and an engagement bead positioned at the distal end of the third guide wire extending from the secondary catheter. This mechanical engagement insures that the capture will remain intact until the surgeon initiates a manual release. 
     In this particularly preferred mode of the disclosed device and method, a bead is engaged upon the extended third guide wire of the secondary catheter. To allow easy withdrawal of the third guide wire through the secondary catheter, the proximal profile of the bead needs to be tapered so as to align with the lumen easily. This attribute would, however, be in conflict with the requirement that the bead be securely captured in the snare loop, which would be aided by the bead having an abrupt proximal profile. 
     Therefore, the third guide wire from the secondary catheter in one preferred embodiment employs an abruptly fashioned bead which may not be removable through the lumen of the secondary catheter from which it translates. Using this mode of the device would therefore require a wire exchange be executed by the surgeon using conventional wide lumen sheaths to position a heavy duty angiographic wire inside the cuff over which the contralateral leg may be translated into the cuff. 
     Of course those skilled in the art will no doubt realize the device may be employed to take advantage of the prepositioned escort catheter guide wire in the cuff of the contralateral leg in combination with the operation of a snare or other means of engagement to secure and guide some type of guide wire from the secondary catheter to be employed to guide the contralateral leg into engagement with the cuff. Further, the method of positioning a capture device adjacent to the distal end of the main delivery catheter and prepositioning a guide wire in the cuff of the contralateral leg may be employed with currently manufactured devices. The employment of this method with all such devices is anticipated as included herein. Still further, while a two-step expansion system is described herein for the trunk and leg portions of the device, it is anticipated that a one-step expansion could be employed in a less preferred method and mode of the device which would require extraction of the second catheter from a position sandwiched between the engaged first leg and the iliac artery, and such is anticipated. 
     The device herein disclosed, as noted, has a first component which includes a trunk portion with an enlarged diameter adapted to engage within the walls of the aorta. In addition to the trunk portion, the first component has two smaller conduits extending from a lower end of the trunk opposite the open aperture of the trunk portion. An ipsilateral or first leg has a diameter and a length adapted to allow it to extend into an engaged position communicating between the trunk and one of the iliac arteries when the first component portion is deployed to its enlarged position. The other shorter conduit is a cuff portion which also extends from the lower end of the trunk portion. The shorter cuff portion has an aperture at a distal end. The distal end of the cuff is adapted for engagement to an engagement end of the second or contralateral leg which is the second component of the assembled device. 
     The trunk, first leg, and cuff forming the first component are adapted to be collapsed to a compressed position and held in that state by a removable sheath or other means of releasable restraint of the first component when engaged at the distal end of a first delivery catheter. A release mechanism is engaged within or along the first delivery catheter to allow a sequential release of the restraining mechanism at a desired time in the procedure. In a preferred mode of the device herein disclosed, the releasable restraint would provide two separately releasable component portions that would allow for expansion of the trunk and cuff portions of the device in a first step and the remainder of the device subsequent to engagement of a third guide wire into the cuff portion. 
     A second component of the device is a second leg portion which is engaged to a second delivery catheter in a collapsed state for translatable delivery along the properly positioned secondary guide wire to an engagement with the expanded cuff of the first component. As noted, the engagement end of the contralateral or second leg is adapted to cooperatively engage with the distal end of the expanded cuff to thereby yield a second conduit for blood flow from the trunk portion and into the second of the two iliac arteries once the device is fully assembled and deployed. 
     A projecting first guide wire is positioned in the body to provide a guide to the first delivery catheter which is advanced thereover to place the graft-bearing portion or distal end of a first delivery catheter in a proper positioning. The trunk and first leg are held by a fabric sheath or other restraining mechanism in a collapsed position. An escort catheter is slidably engaged within the first delivery catheter and has a projecting end portion which extends from an exit aperture in the first delivery catheter. This end portion is substantially exposed but for a tip portion which is held under the restraint. 
     A second guide wire extending from the distal end of the escort catheter is pre-positioned within the cuff portion extending from the trunk of the first component prior to compression to the collapsed state. Once in the collapsed state, this second guide wire extending from the projecting end portion of the escort catheter thereby remains pre-positioned in the cuff. 
     As noted, also incorporated into the escort catheter of the device is a snare which is preferably formed of memory material such as nitinol. This snare is extendable from an exit aperture communicating through the sidewall of an uncovered portion of the escort catheter. A snare control wire for cinching the projecting snare is tranlatably engaged axially through the escort catheter to a rotating valve positioned exterior to the body of the patient. The cinch can thus be extended to an enlarged loop, or collapsed, by translation of the control wire. Using memory material, the enlarged loop may be preformed with a memorized shape and projection, such that the loop so projected is orthogonal to the axis of the escort catheter and is of a size best adapted to the task of capturing a third guide wire extending forward from the secondary catheter which is also operatively engaged to this guide wire. 
     In the method of implantation, the first component formed of the trunk, first leg, and cuff, in the above noted collapsed position on the end of the first delivery catheter, is translated over a pre-positioned first guide wire through a femoral artery to thereby position the trunk within the aorta at the site of the aneurysm. To this end, the first delivery catheter is extended up through one of the iliac arteries to position the trunk portion in the aorta and concurrently place the first leg within that iliac artery. 
     Prior to activation of the mechanism which releases a first portion of the employed means for restraining the upper half of the first component in the collapsed position, the snare is extended from the uncovered portion of the escort catheter to form a loop by translating the snare wire. The loop as noted, is positioned at the juncture of the second iliac artery and the aorta by extension of the snare and/or translation of the escort catheter. Once positioning of the first component and the snare is properly confirmed using the fluoroscope or other means, the second catheter is translated up the opposite leg artery toward the first component. The third guide wire extending from the distal end of the secondary catheter and has a bead or small terminating component fixed to its distal end to provide a grip for the snare. 
     During this step, the distal end of the third guide wire extending from the second catheter is translated to a point wherein it traverses through the extended loop of the projecting snare which is positioned around the iliac artery juncture with the aorta. Once traverse of the second guide wire through the loop of the snare is confirmed, the snare control wire is translated to cinch the loop of the snare and capture the distal end of the third guide wire extending from the second catheter. A locking rotatable valve is then set to hold the snare in the closed position. 
     At this juncture in the method of deployment the disclosed device with the captured third guide wire may be manipulated into proper position relative to the aorta and iliac arteries by the surgeon to provide a precise graft positioning depending on the surgeon&#39;s chosen mode of leg and trunk orientation of the device within the patient. As noted, this maneuver can be accomplished without risk of loss of the captured second guide wire since it is secure in the snare and only subject to release by the positive action of the surgeon to do so. Once properly positioned by the surgeon, the first portion of the compressed first component may be fully deployed from the compressed state to the enlarged state thereby seating the trunk in the aorta and the cuff in expanded mode. The first or longer engaged leg remains compressed for subsequent deployment in the chosen one of the two iliac arteries. 
     Once the first component is so expanded, the novelty and utility of the disclosed device become evident. Since the third guide wire of the secondary catheter is already captured by the snare, and the second guide wire extending from the escort catheter is pre-positioned within the now expanded cuff, it is a short and simple process to translate the escort catheter, along with the snare-engaged guide wire of the secondary catheter, along the second guide wire into the cuff, and subsequently translate the secondary catheter, or subsequent devices, over the third guide wire and into the cuff. 
     As noted earlier, with the third guide wire extending from the secondary catheter positioned in the cuff, any of a number of conventional wire exchanges may be executed by the surgeon using this third guide wire from the secondary catheter to place a conventional heavy duty guide wire into the cuff, over which the catheter bearing the contralateral leg may be advanced for engagement into the cuff. 
     As an example, the surgeon may advance a wide lumen sheath over the third guide wire to thereby position its distal end inside the cuff. Thereafter, the third guide wire may be removed through the wide lumen axial cavity of the sheath and a guide wire of the surgeon&#39;s choice may be properly positioned through the axial cavity to place its distal end inside the cuff. Using this subsequently placed wire, the surgeon would then advance a secondary delivery catheter, bearing the second leg, thereover to properly position the contralateral or second leg within the distal end of the cuff. The contralateral leg is then deployed by activating a control to release the constraining mechanism holding it in a collapsed state, as is the first leg in the secondary employment of the first component of the assembled device. Once so deployed, the engagement end of the properly positioned contralateral leg enlarges to a fixed engagement with the cuff thereby providing the second sealed conduit between the aorta-engaged trunk and the second iliac artery. This completes assembly of this device. 
     As those skilled in the art will realize, other means to releasably engage the secondary catheter guide wire to the escort catheter extending exposed from the first delivery catheter might be employed, and all as would occur to those skilled in the art are anticipated. However, because of the confined working environment, the compactness and ease of operation of the snare, the ability to provide memorized shapes to the snare, and the positive releasable mechanical engagement thereon, the current preferred mode of the device employs the snare to capture the secondary catheter for placement of a third guide wire in the contralateral cuff. 
     With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. Therefore, the foregoing summary and following detailed description are considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a depiction of the device showing a delivery catheter having a snare capture component extending from an exposed aperture in an escort catheter. 
         FIG. 2  depicts the escort catheter and an extending snare and control wires. 
         FIG. 2   a  depicts the device incorporated into the delivery catheter and a release stitch providing a two-stage release of a restraint during deployment. 
         FIG. 3  depicts the capture of a third guide wire using a snare extendable from the escort catheter. 
         FIG. 4  shows insertion of the delivery catheter to a position at the juncture of the second iliac artery and the aorta and deployment of the snare capture device from the escort catheter. 
         FIG. 5  depicts translation of the device into the aorta subsequent to capture of the second lead wire. 
         FIG. 6  shows initial deployment, by release of a first portion of the two stage restraint through a release of the constraining stitch allowing expansion of the trunk portion of the device in the aorta. 
         FIG. 7  depicts translation of the escort catheter and captured third guide wire into the expanded cuff. 
         FIG. 7   a  shows the escort catheter and third guide wire fully translated into the expanded cuff ready for release from its engagement with the snare. 
         FIG. 8  shows the third guide wire positioned in the cuff after release of the snare and removal of the escort catheter. 
         FIG. 9  depicts a subsequent guide wire located in the cuff after the surgeon executes a wire exchange with the second lead wire and a subsequent advancement of the restrained second leg, along the chosen guide wire for engagement in the cuff. 
         FIG. 10  shows the second leg of the device in an expanded engagement with the cuff subsequent to release of restraint mechanism holding the second leg collapsed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in  FIGS. 1-10 , wherein similar parts are identified by like reference numerals, the device  10  is depicted in  FIG. 1  which illustrates the components of the bifurcating prosthesis  12  engaged to the distal end of a delivery catheter  38 . A trunk portion  14  is shown having a diameter adapted to engage within the walls of the aorta  16  shown in  FIGS. 4-6 . The trunk portion  14  is in communication with two smaller conduits extending from a lower end of the trunk  14 , communicating with the larger open aperture at the upper end of the trunk  14 . An ipsilateral or first leg  18  shown in  FIG. 1  and  FIGS. 4-10 , has a diameter and a length adapted to extend into an engaged position communicating between the trunk  14  and one of the iliac arteries. The other shorter conduit shown in  FIGS. 1 and 2   a , is a cuff  22  portion extending from the lower end of the trunk  14  portion. As shown in other figures such as  FIG. 10 , the distal end  24  of the cuff  22  is adapted for engagement to one end of the contralateral or second leg  28  of the assembled device  10  as depicted in  FIG. 10 . 
     In use adapted for deployment, the trunk  14 , first leg  18 , and cuff  22  forming the first component are initially in a collapsed position and held in that state by means of a releasable restraint adapted to the task, which is shown in  FIG. 1  as a fabric sheath  30  having a release stitch  31  as a release mechanism to deploy the restraint as best shown in  FIG. 2   a . The release stitch  31  shown in  FIG. 2   a , is a chain-type stitch and incrementally releasable by traction on the release string  32  slidably engaged through the first delivery catheter  38  to allow release of the sheath  30  or other releasable restraint, in two segments  33   a  and  33   b , for a staged deployment of the device  10  from its collapsed position in  FIG. 2   a.    
     As depicted in  FIGS. 1 and 2   a , in a preferred mode of the device  10 , the restraint would provide for two separately releasable component sections  33   a  and  33   b  in a sequential releasable restraint of the bifurcated prostheses  12  which allows for sequential expansion of the first component  19  (comprising the trunk  14  and cuff  22 ), and subsequently the ipsilateral leg  18  in sequential steps and at appropriate times chosen by the surgeon. The second leg  28  shown in the  FIG. 10 , is engaged to a second delivery catheter  34  in a collapsed state for translatable delivery along a positioned guide wire  55  to an engagement with the expanded cuff  22 . The leading end  29  of the contralateral or second leg  28  shown in  FIG. 10 , is adapted to cooperatively engage with the distal end  24  of the expanded cuff  22 . 
     The first delivery catheter  38  is advanced through an axial passage running through the interior of the first leg  18  over a first guide wire  35 . As shown in  FIGS. 1 and 2   a , the escort catheter  40  is slidably engaged with the first delivery catheter  38  and with its distal end projecting from an exit aperture  41  in the first delivery catheter  38  as depicted in  FIGS. 1 and 2   a . In this configuration the distal end of the escort catheter  40  is covered in an engagement under the first release component  33   a  to maintain the escort catheter  40  streamlined and adjacent to the delivery catheter  38  during initial deployment ( FIG. 2   a ). 
     A second guide wire  36  projects from the distal end of the escort catheter  40  and is pre-positioned within the cuff  22  prior to compression of the first component  19  to the collapsed state in which it is held by the releasable component sections  33   a  and  33   b  depicted in  FIG. 1 , or other means of sequentially releasable restraint. As shown in  FIG. 2   a  this distal end engagement may be accomplished by passage of the tip of the escort catheter  40  through the release stitch  31  thereby allowing for easy sequential release by the surgeon of the first component section  33   a  along with the escort catheter  40 . The second guide wire  36  thus remains pre-positioned in the cuff  22  for subsequent employment as a guide into the cuff  22  once the first releasable component  33   a  is released expanding the trunk  14  and cuff  22 . 
     In a preferred mode of the device  10  shown in various views in  FIGS. 1-3 , communicating from an exit aperture  42  in the escort catheter  40 , is a wire capturing means shown as a snare  46  in  FIG. 2   a . The snare  46  is preferably formed of memory material such as nitinol to a predetermined preferred deployed shape and controllable size by the operator. A snare control wire  50 , or other means for cinching and expanding the projecting snare  46 , is tranlatably engaged axially through the escort catheter  40  and through a locking valve  51  positioned exterior to the body of the patient. The snare  46  can thus be extended to a loop of a desired size or collapsed by translation of the control wire  50  and held in that position by the locking valve  51 . 
     During implantation, the first component  19  shown expanded in  FIG. 8 , formed of the trunk  14 , first leg  18 , and cuff  22 , and shown in  FIG. 1  in a collapsed position on the distal end of the first delivery catheter  38 , is translated over the pre-positioned first guide wire  35  ( FIG. 1 ), through a femoral artery. The first component  19  in the collapsed position is advanced to a position within the aorta so that the aperture  42  of the escort catheter is adjacent to the juncture of the second iliac artery and the aorta. 
     Prior to the sequential release of the compressed first component  19 , and once the surgeon has determined proper placement in the aorta, the snare  46  is deployed from the exit aperture  42  in the escort catheter  40 , to form a loop by employment of the snare control wire  50 . The loop of the snare  46  as noted, is properly positioned by the surgeon at the juncture of the second iliac artery and the aorta. Means for positioning of the snare  46  is provided by one or a combination of extension of the snare  46 , translation of the delivery catheter  38  and rotation of the delivery catheter  38 , to thereby properly deploy the snare  46  extending from the escort catheter  40  in a position for a capture of a third guide wire  54  inserted from the contralateral femoral artery as depicted in  FIG. 4 . 
     Upon proper positioning of the first component  19 , and the snare  46 , a guide catheter  37 , having the third guide wire  54  extending from its distal end, is translated through the opposite leg artery shown in  FIG. 4 . As noted, in a preferred mode of the device  10 , the third guide wire  54  is extendable from the distal end of the guide catheter  37  and has a bead  56  or similar means for maintaining a secure capture within the cinched snare  46 . Other means to maintain the snare  46  on the third guide wire  54  may be employed as would occur to those skilled in the art and such are anticipated. The main object being that the snare  46  maintains its engagement to the third guide wire  54  during manipulation of the device  10  after the capture, to a desired positioning within the aneurysm. This secured engagement of the cinched snare  46  and escort catheter with the captured third guide wire  54 , allows for subsequent translation of the escort catheter  40  along the second guide wire  36 , and concurrent translation of the captured third guide wire  54  into the cuff  22  without risk of a detachment therefrom. 
     As shown in  FIG. 4 , in the positioning step, the distal end of the third guide wire  54  and the guide catheter  37  are translated to a point wherein the bead  56  passes through the pre-positioned and extended snare  46 . Once so positioned, the snare control wire  50  is translated to close the loop and capture the distal end of the third guide wire  54 . This cinched snare  46  around the third guide wire  54  behind the bead  56  thereby provides means for positive mechanical engagement of the escort catheter  40  to the third guide wire  54 . A locking valve  51  is then set to maintain the snare  46  cinched. As noted, once so captured, the delivery catheter  38  may be manipulated by the surgeon for proper position for deployment of the first component  19  in the aneurysm, as depicted in  FIGS. 5-6 . During this positioning, capture of the third guide wire  54  is maintained, whether the delivery catheter  38  is translated or rotated. 
     Once the first component  19  is properly positioned, the first releasable portion  33   a  of the restraining device shown as the sheath  30 , is released as shown in  FIGS. 6-7 . Release as noted is in two stages through the disengagement of the release stitch  31  by translation of the release string  32  ( FIG. 2   a ). Release of the first releasable portion  33   a  expands the trunk  14  and the cuff  22  in the aorta, and also releases the distal end of the escort catheter  40  from its engagement under the first releasable portion  33   a  of the fabric sheath  30 . The first leg  18  portion in the preferred mode of the device, remains compressed within the second releasable component  33   b , for subsequent deployment. 
     With the third guide wire  54  captured against the side of the escort catheter  40 , the escort catheter  40  is now translated along the pre-positioned second guide wire  36  extending into the now expanded cuff  22  as depicted in  FIG. 7 . This translation of the escort catheter  40  moves the snare-engaged third guide wire  54  into the interior of the cuff  22  easily, thereby eliminating a time-consuming, costly, radiation-intensive and frustrating component in current versions of the procedure. 
     Once the surgeon ensures passage of the third guide wire  54  into the cuff  22 , the snare  46  may be released and the second guide wire  36  and the escort catheter  40  removed. The third guide wire  54  is maintained in position inside the cuff  22  while the escort catheter  40  and snare  46  are removed. With the third guide wire  54  in position, the second releasable portion  33   b  may be released to deploy the ipsilateral or first leg  18  of the graft in place in the artery. Release of the second releasable portion  33   b  is accomplished by finishing the unwinding of the release stitch  31  through a translation of the release string  32 . Thereafter the first delivery catheter  38  is removed leaving the first component  19  engaged in place in the aorta as shown in  FIG. 8 . 
     With the first component  19  so engaged, as will be evident to those skilled in the art, employing the properly positioned third guide wire  54  as a guide, any of a number of conventional wire exchanges may be executed by the surgeon using the third guide wire  54  to properly position subsequent sheaths or guide wires having their distal ends easily positioned inside the cuff  22 . For instance the surgeon may advance a wide lumen sheath over the third guide wire  54  to a position with its distal end inside the cuff  22 , whereafter the third guide wire  54  may be removed through the wide lumen axial cavity of the sheath. Thereafter a wire  55 , of the surgeon&#39;s choice, as shown in  FIG. 9 , may be properly positioned through the axial cavity to place its distal end inside the cuff  22 . 
     Using the wire exchange and the subsequently placed wire  55 , the surgeon then advances a secondary delivery catheter  34  thereover to properly position the second component of the bifurcated stent graft  12 , which is the contralateral or second leg  28 . Such a proper positioning with the leading end  29  the collapsed second leg  28  within the distal end  24  of the cuff  22  is easily accomplished translating the second delivery catheter  34  over the wire  55 . So positioned, the second leg  28  is then deployed by activating a secondary release string  58  to release the means for constraint of the second leg  28  from its collapsed position as depicted in  FIG. 9  to an engagement with the cuff  22  as depicted in  FIG. 10 . 
     The method and components shown in the drawings and described in detail herein disclose arrangements of elements of particular construction and configuration for illustrating preferred embodiments of structure and steps for deployment of the present invention. It is to be understood, however, that elements of different construction and configuration, and using different steps and process procedures, and other arrangements thereof, other than those illustrated and described herein, may be employed for providing for the capture of a second guide wire prior to expansion of a bifurcated endovascular prosthesis in accordance with the spirit of this invention. Further, existing prostheses can be easily adapted to employ the method of assembly and deployment herein described, to deploy a capture device from a catheter which also has a pre-positioned guide wire inside the cuff to later guide that catheter and a captured second guide wire therein. Or, to employ the second catheter and prepositioned wire, to guide any component which can engage with the second catheter, into the cuff portion to be used as a later guide for the leg extension. 
     As such, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended in the foregoing disclosures, it will be appreciated that in some instance some features of the invention could be employed without a corresponding use of other features without departing from the scope of the invention as set forth in the following claims. All such changes, alternations and modifications as would occur to those skilled in the art are considered to be within the scope of this invention as broadly defined in the appended claims. 
     Further, the purpose of the abstract of the invention, is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers, and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting, as to the scope of the invention in any way.