Abstract:
A delivery system for endoluminal deployment of a stent inside of a biocompatible graft cover minimizes obstruction of endoluminal fluid flow during deployment. The delivery system comprises a stent sheath, a compressed stent underlying the stent sheath, and a graft overlying the stent sheath and releasably retained in a compressed state surrounding the sheath. The graft distal end is attached to the stent at or proximal the stent distal end, and the graft outer surface is exposed to the interior space of the lumen during deployment. The proximal end of the graft may be attached to the stent sheath by a releasable attachment adapted for release during deployment of the stent, or may be otherwise constrained, such as by heat deformation, to remain adjacent the outer circumference of the stent prior to deployment. The releasable attachment may be a suture that is severed by a pusher having a cutter therein. The delivery system may further include an inner core underlying the stent and connected to a tip sheath that overlies the stent distal end. One method of deploying the stent and overlying graft comprises advancing the tip sheath to allow the stent distal end to expand, retracting the stent sheath to cause the suture to be severed by the pusher cutter therefore allowing endoluminal fluid to flow between the graft and the sheath, and then completing deployment of the stent to urge the graft against the lumen wall.

Description:
TECHNICAL FIELD 
     The present invention relates generally to endoluminal grafts or “stents” and, more specifically, to a stent delivery system or “introducer” for deploying a stent inside of a prosthetic graft without interrupting fluid flow during deployment and a method for such deployment. 
     BACKGROUND OF THE INVENTION 
     A stent is an elongated device used to support an intraluminal wall. In the case of a vascular stenosis, a stent provides an unobstructed conduit for blood in the area of the stenosis. An intraluminal prosthesis may comprise a stent that carries a prosthetic layer of graft material. Such a prosthesis may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, an intraluminal stent or prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the stent, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a stent deployment system or “introducer” to the site where it is required. The introducer may enter the body through the patient&#39;s skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. When the introducer has been threaded into the body lumen to the stent deployment location, the introducer is manipulated to cause the stent to be released from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the stent), whereupon the stent expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stents are typically expanded by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration. 
     Referring now to a stent deployment system of the prior art in FIG. 1, there is shown an endoluminal prosthesis  10  comprising a wire stent  12  affixed along its length to an outer graft cover  14 , the graft and stent compressed inside outer sheath  16  (shown in cross-section). During the deployment process of endoluminal prosthesis  10  in a body lumen  20 , such as a blood vessel, outer sheath  16  is retracted, and stent  12  expands against the walls  19  of the lumen  20  (shown in cross-section). During the expansion process, the partially-deployed, covered section  22  at distal end  23  and middle section  25  of integral stent/graft prosthesis  10  can block the flow of blood along arrow A temporarily until proximal end  24  is released from the sheath. As used herein, “proximal” is defined as meaning “closer to the end of the introducer remaining outside the body”, whereas “distal” is defined as meaning “farther from the end of the introducer remaining outside the body”. During deployment, the pressure of obstructed blood flow at covered section  22  may cause the prosthesis to migrate away from its intended location or become longitudinally compressed. If for some reason the deployment procedure becomes protracted, the blood flow blocked by covered section  22  may impart serious stress upon the patient. Thus, it is desirable to provide for unobstructed blood flow throughout the stent deployment process. 
     A construction known to the inventor prior to this invention comprises a device shown in FIG. 2 comprising stent  12 ′ and outer graft cover  14 ′ joined by a connection  30  to stent  12 ′ proximal the distal end  23  thereof. Prior to deployment, stent  12 ′ and graft liner  14 ′ are restrained in a compressed configuration by an outer sheath  16 ′ surrounding both the stent and the liner, and by an inner sheath  38  disposed between stent  12 ′ and liner  14 ′ proximally of connection  30 . Deployment of this prosthesis is effected by first retracting outer sheath  16 ′, allowing distal portion of stent  12 ′ and then cover  14 ′ to fully expand independently. Stent  12 ′ is subsequently fully expanded proximal of the connection point by retracting inner sheath  38 . During deployment of this device, blood flow can continue as indicated by arrows B. 
     The introducer construction having two sheaths as described above necessarily requires an introducer of somewhat larger diameter and lesser flexibility than most such introducers known in the art having only a single sheath. 
     SUMMARY OF THE INVENTION 
     The present invention provides a flexible, single-sheath, low-profile delivery system for deployment of a stent inside of a biocompatible graft cover in a distal deployment location in a body lumen from a proximal access location outside the body lumen. The delivery system comprises a stent sheath having a distal end located upstream relative to the fluid flow; a compressed stent underlying the stent sheath, the stent having a proximal end housed within the stent sheath and a distal end; and a compressed biocompatible graft cover overlying the stent sheath along the length of the stent and releasably retained in a compressed state surrounding the sheath. The graft has a distal end attached to the stent at or proximal the stent distal end and an outer surface exposed to the interior space of the lumen during deployment. The stent distal end may be spaced distally from the stent sheath distal end and graft attachment, in which case the delivery system may further comprise a tip sheath overlying the stent distal end and an inner core, optionally having a guidewire lumen therein, attached to the tip and extending axially through the stent. A pusher underlies the stent sheath proximal the stent. The pusher distal end may be rounded. The inner core and attached tip sheath may be attached distally to the pusher, or the pusher may have an inner lumen extending axially therethrough, wherein the inner core extends axially through the pusher inner lumen. 
     The stent delivery system further may comprise a temporary, protective wrapper over the biocompatible graft, the wrapper adapted to be removed prior to insertion of the delivery system into the body lumen. The compressed biocompatible graft may further comprise a proximal end attached to the stent sheath by a releasable attachment, such as a suture, adapted to be released during deployment of the stent. The suture may be adapted for release by being secured with a slip-knot adapted to be untied during stent deployment, by the delivery system further comprising a balloon adapted for breaking the suture upon inflation of the balloon, or by the pusher further comprising a cutter, such as a sharpened hypotube, adapted for severing the suture upon movement of the pusher relative to the stent sheath. 
     Specifically, the stent sheath may have a suture connection point, such as a pair of tie-holes, in its circumference and radially-opposite first and second through-holes, with the pusher having a window in its distal end aligned with the stent sheath through-holes and having the cutter proximally located therein. In such a configuration, the opposite ends of the suture are attached to the suture connection point, and an intermediate section of the suture is threaded through the graft in one or more locations, through the sheath through-holes, and through the pusher window. 
     The invention further comprises a method for endoluminally deploying a stent and overlying biocompatible graft cover without obstructing fluid flow during deployment, as follows. First, the stent and graft are compressed and loaded into a single-sheath-profile stent delivery system as described herein. Then, the stent delivery system is inserted into a body lumen and navigated through the lumen until the stent is at a desired deployment location. Next, the stent sheath is proximally displaced relative to the stent distal end, the stent distal end becomes expanded, and endoluminal fluid flows between the stent sheath and the graft so that the graft becomes radially distanced from the stent sheath. Finally, deployment of the stent is completed so that it biases the graft against the body lumen. 
     Where the stent delivery system further comprises a tip having a tip sheath overlying the distal end of the stent and attached to an inner core extending axially through the stent, the method further comprises, prior to proximally displacing the stent sheath relative to the stent, first releasing the stent distal end from the tip sheath by displacing the inner core distally relative to the stent sheath. Where the pusher is attached to the inner core, displacing the inner core distally relative to the stent sheath comprises a single, continuous, proximal retraction of the stent sheath that also displaces the pusher distally relative to the stent sheath to deploy the stent. Where the pusher has an inner lumen axially therethrough through which the inner core is mounted, displacing the inner core distally relative to the stent sheath comprises first advancing the inner core distally relative to the stent sheath to release the stent distal end from the tip sheath, and then retracting the stent sheath to deploy the stent. Where the proximal end of the graft is attached to the sheath with a releasable attachment such as a suture, the attachment is released prior to endoluminal fluid flowing between the graft and the sheath. Where the releasable attachment is a suture, the step of moving the stent sheath relative to the pusher may cut the suture. 
     The method may further comprise suturing the graft to the stent sheath by the steps of anchoring a first end of the suture through the tie-holes, extending the suture along the stent sheath; piercing the graft one or more times with the suture; extending the suture along the stent sheath; entering the stent sheath radially through one of the through-holes, extending the suture through the pusher window, and exiting the stent sheath through the opposite through-hole; extending the suture along the stent sheath; piercing the graft one or more times with the suture; extending the suture semi-circumferentially around the sheath; and anchoring a second end of the suture to the tie-holes. 
     After deployment, the stent delivery system may be prepared for withdrawal by advancing the pusher into the tip sheath and advancing the stent sheath until the distal end of the stent sheath is adjacent the proximal end of the tip sheath, and then withdrawn. Prior to insertion into the body, the stent sheath may be locked to the pusher and the inner core biased under slight tension and locked to the pusher. In such case, deployment further comprises unlocking the inner core from the pusher prior to moving the inner core distally and unlocking the stent sheath from the pusher prior to retracting the stent sheath. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention. 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures: 
     FIG. 1 is a longitudinal section schematic illustration of an exemplary endoluminal prosthesis delivery system of the prior art. 
     FIG. 2 is a longitudinal section schematic illustration of an exemplary stent delivery system known to the inventor prior to this invention. 
     FIGS. 3A-3C are longitudinal section schematic illustrations of an assembled exemplary stent delivery system of the present invention, and enlarged portions thereof, respectively. 
     FIGS. 4A and 4B are schematic illustrations of a crochet weave securing a graft to the stent sheath, shown in partial longitudinal section, and of the loops of an exemplary crochet configuration, respectively. 
     FIG. 5 is a longitudinal section schematic illustration of a graft secured to the stent sheath with an adhesive. 
     FIGS. 6A-6C are schematic illustrations of an exemplary graft and an exemplary stent sheath to which the graft is adapted to be releasably secured, a longitudinal section of such graft and stent sheath showing the graft in a secured configuration, and a longitudinal section of the graft and stent sheath showing the graft in a released configuration. 
     FIGS. 7A-7C are longitudinal section schematic illustrations of the stent delivery system of FIGS. 3A-3C during sequential deployment steps. 
     FIG. 7D is a partial longitudinal section schematic illustration of the deployed stent and the stent delivery system prepared for withdrawal after the deployment step shown in FIG.  7 C. 
     FIG. 8 is a flowchart depicting exemplary method steps for deployment of a stent and graft according to the present invention. 
     FIG. 9 is a longitudinal section schematic illustration of an alternate embodiment of an assembled exemplary stent delivery system of the present invention. 
     FIGS. 10A and 10B are a longitudinal section schematic illustration of an exemplary introducer embodiment wherein the graft is secured via a slip knot, and a detailed illustration of the knot, respectively. 
     FIG. 11 is a partial longitudinal section schematic illustration of a distal portion of an exemplary stent delivery system having a crochet weave securing the distal end of the stent. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring now to the drawing, wherein like reference numerals refer to like elements throughout, FIGS. 3A-3C illustrate an exemplary introducer according to the present invention for endoluminal deployment of a stent inside of a biocompatible graft cover without obstructing endoluminal fluid flow during deployment. As shown in FIGS. 3A-C, exemplary stent delivery system  40  comprises a stent sheath  42 , a compressed stent  44  underlying the stent sheath, a pusher  46  underlying the stent sheath proximal to the stent, an inner core  48 , and a compressed biocompatible graft  50  overlying distal end  52  of the stent sheath. Inner core  48  is axially mounted within inner lumen  56  of pusher  46 , extends axially through stent  44  and attaches to tip  58  comprising tip sheath  60  overlying distal end  62  of the stent. Optional central guidewire lumen  49  (not shown in FIG. 3A) runs through inner core  48  and tip  58 , as shown in FIGS. 3B and 3C. Graft  50  has a distal end  64  attached to the stent by attachment  51  distally of the sheath distal end  52 . Optionally, attachment  51  may be located at or somewhat proximally of the distal end  52  of sheath  42  within sheath  42 , so long as the part of graft  50  lying within sheath  42  is easily pulled or otherwise disposed distally of sheath  42  during deployment. Graft  50  further has a proximal end  66  attached to stent sheath  42  by a releasable attachment, such as suture  68 , adapted to be released during deployment of the stent. As shown in FIGS. 3A-C, pusher  46  has a rounded distal end  47 . 
     Although stent delivery system  40  has both a tip sheath  60  and a stent sheath  42 , the two sheaths abut one another axially and have the same outer diameter. Thus, the two sheaths together in series form a single-sheath-profile stent delivery system, meaning that the profile of the stent delivery system is no greater than that provided by a single outer sheath plus graft material. Other embodiments having no tip sheath  60 , are discussed below. 
     The stent may be self-expanding, comprising, for example, a shape-memory material such as nitinol, or may be any type of elastically or thermally expandable stent known in the art. The biocompatible graft material may be polyester, polyurethane, polyethylene, polytetrafluoroethylene (PTFE), or any material known in the art. The stent deployment system of the present invention may be used for deployment of stents and grafts within blood vessels or in other body lumens, such as in the trachea. As used herein, the term “stent delivery system” shall encompass both a completed assembly which is capable of deploying a stent or a sub-assembly which is capable of deploying a stent when combined with other components. 
     To effect release of the suture  68  during deployment, pusher  46  further comprises at distal end  47  a window  76  in which is proximally mounted cutter  70 , such as a sharpened hypotube, adapted for severing the suture upon movement of the pusher relative to stent sheath  42 . Stent sheath  42  has a connection point, such as a pair of tie-holes  72 , as shown in FIG. 3C, and a pair of radially opposite through-holes  74 . Window  76  is radially aligned with stent sheath through-holes  74  prior to and during introduction of stent delivery system  40  into the body. As shown in FIG. 3C, suture  68  is anchored at one end through tie-holes  72  and extends distally along stent sheath  42  from the tie-holes along arrow “C”, pierces graft  50  one or more times along arrow “D”, returns proximally along the stent sheath along arrow “E”, turns radially in the direction of arrow “F” and enters the stent sheath through one through-hole  74 , extends through pusher window  76  and exits the stent sheath through the other through-hole  74 , extends distally along the stent sheath along arrow “G”, pierces the graft one or more times along arrow “H”, extends semi-circumferentially around the stent sheath along arrow “I” (shown in dashed lines) and anchors to the tie holes or to the other end of the suture. Suture  68  may be attached by a method that follows the order described above, starting along arrow C in alphabetical order through arrow I, or in reverse order, starting in the direction opposite arrow I, and following reverse alphabetical order in the opposite direction of each arrow named above. This suture configuration reduces friction between the suture and graft during deployment because the suture is cut into two short lengths to be pulled through the graft rather than one long length of suture. 
     Other suture configurations may also be used to anchor graft  50  to stent sheath  42  and to cut the suture upon deployment. Instead of the suture being tied through a pair of tie holes  72 , the suture connection point to stent sheath  42  may comprise any type of connection known in the art. Such connection may comprise, for example without limitation thereto, a single hole in the stent sheath and a stopper knot tied in the end of the suture to prevent pulling the end through the hole, an adhesive or heat-fused bond, or a crimped metal or rubber band. 
     Different releasable attachment devices other than sutures may also be used. In an alternative embodiment, referring now to FIGS. 4A and 4B, a crochet weave  80  may be disposed over proximal end  66  of graft  50  to secure it to stent sheath  42 . As shown in detail in FIG. 4B, crochet weave  80  comprises a continuous filament  82  wound into n successive loops  84   i-n  helically wrapped around the graft in alternating orientations (loop  84   i  counterclockwise, loop  84   ii  clockwise, loop  84   iii  counterclockwise, and so on, viewed from loop  84   i  looking proximally), the stem  86  of each loop protruding through the hole  88  made by the preceding loop. Distal end  90  of filament  82  is typically releasably secured to provide resistance to unwinding of crochet weave  80 , such as by being pulled through a slot  91  in tip sheath  60  and pinched therein. Proximal end  92  of the filament is tucked within through-hole  74  in stent sheath  42 , as shown in FIG. 4A, and trailed within the stent sheath to the outside of the body. Filament  82  may then be pulled like a drawstring to untie crochet weave  80  loop by loop and to pull distal end  90  out of slot  91 . Although FIG. 4A shows sheath  42  and graft  50  in longitudinal section to illustrate through-hole  74  and trailing proximal end  92 , crochet weave  80  is illustrated in its entirety without hidden portions, to show location. FIG. 4B shows crochet weave  80  as visible from one side of graft  50 . 
     In another alternative embodiment, referring now to FIG. 5, graft  50  may be tacked to stent sheath  42  with a bead of biocompatible adhesive  100  that softens or dissolves after a certain amount of time of exposure to blood (or other intraluminal fluid in the lumen in which the stent is to be deployed), thus allowing the graft to be pulled away from stent sheath  42  upon deployment. 
     In yet another alternative embodiment, referring now to FIGS. 6A-6C, graft  650  may have a tab  651  at the proximal end  66  thereof, the tab adapted to be inserted in slot  674  in stent sheath  642 . Tab  651  is then releasably secured by being pinched between stent sheath  642  and pusher  646 , as shown in FIG.  6 B. Pusher  646  has an indent  676  adjacent the pusher distal end  647  such that when sheath  642  is retracted proximally or pusher  646  is advanced distally, indent  676  aligns with slot  674  in stent sheath  642  such that tab  651  is released and graft  650  is free to deploy, as shown in FIG.  6 C. As shown in FIGS. 6B and 6C, tab  651  may be completely inserted within slot  674  and its end pinched between pusher  676  and the inside wall of stent sheath  642  as shown with respect to top slot  674 , or as shown with respect to bottom through-hole  674 ′, portion  651 ′ of graft  650  may be doubled over on itself with the end outside the slot. Portion  651 ′ inserted within slot  674 ′ may be a discrete tab, or if the materials of construction of graft  650  so allow, portion  651 ′ may rather be a portion of graft  650  that is merely pushed into through-hole  674 , doubled over on itself, and pinched. 
     Introducer  40  is used to carry out a method for endoluminally deploying a stent and overlying graft without blocking endoluminal fluid flow during deployment, as shown in FIGS. 7A-D. First, stent  44  and overlying graft  50  are compressed and loaded into stent delivery system  40  having the components previously described herein and assembled as shown in FIG.  3 A. Next, the stent delivery system is navigated to a desired deployment location over a guidewire (not shown) or by other means known in the art. Then, at the deployment location, stent distal end  62  is released by moving inner core  48  distally relative to stent sheath  42  along arrow Z, as shown in FIG.  7 A. Then, stent sheath  42  is retracted proximally relative to stent  44  along arrow Y, thus pulling suture  68  in window  76  across cutter  70  of pusher  46  and severing the suture as shown in FIG.  7 B. With suture  68  cut, graft  50  expands so that blood or other endoluminal fluid flows along arrows B through stent  44  and between stent sheath  42  and the graft, as is shown in FIG.  7 C. Suture  68  is retained on stent sheath  42  in two pieces, each piece tied at one end through tie-holes  72  in the stent sheath and carried by the motion of the stent sheath and the endoluminal fluid flow in the direction of arrow B. Stent sheath  42  is retracted along arrow Y until stent  44  is completely deployed in a configuration biasing graft  50  against the walls  19  of the body lumen  20 , as shown in FIG.  7 D. 
     Stent delivery system  40  may then be prepared for withdrawal from the body by advancing pusher  46  inside tip sheath  60  and advancing stent sheath  42  until it is adjacent to the tip sheath as also shown in FIG.  7 D. Rounded distal end  47  of pusher  46  is advantageous for guiding the pusher into tip sheath  60 , which is especially useful when stent delivery system  40  is used in an area of curved anatomy. With the stent delivery system  40  in a closed configuration as shown in FIG. 7D, tip sheath  60  is less likely to snag on stent  44  or on walls  19  of lumen  20  during withdrawal, than if left in an open configuration with a gap between stent sheath  42  and the tip sheath, such as is shown in FIG.  7 C. 
     Prior to deployment, stent sheath  42  may be locked to pusher  46  and inner core  48  may also be locked to the pusher. The locking of these components together is typically accomplished at the handles located at the proximal end of the delivery system (not shown) and that remain outside the body during the deployment procedure. Inner core  48  may also be biased under slight tension prior to locking and introduction of stent delivery system  40  into the body lumen so that tip sheath  60  does not become displaced relative to stent sheath  42  in curved anatomy. Thus, when stent delivery system  40  is introduced into the body in a locked configuration, the step of advancing inner core  48  relative to stent sheath  42  first comprises unlocking the inner core from pusher  46  prior to moving the inner core. Similarly, the step of retracting stent sheath  42  further comprises unlocking the stent sheath from pusher  46  prior to moving the sheath. Thus, one exemplary method for deployment of a stent and graft according to the present invention may include all the steps as depicted in the self-explanatory flowchart of FIG.  8 . 
     Inner core  48  attached to tip  58  (and attached to tip sheath  60 , where present) may be mounted axially through inner lumen  56  of pusher  46  as shown in FIGS. 3A-C and  7 A-D, or, referring now to FIG. 9, inner core  148  may instead be mounted to distal end of pusher  146 . In such a configuration when tip sheath  60  is also present, sheath  42  is retracted in a single motion in the direction of arrow Y to simultaneously pull distal end  62  of stent  44  from out of tip sheath  60 , allowing it to expand, while also severing suture  168  against cutter  170  within pusher  146 . As retraction of sheath  42  continues in the direction of arrow Y after stent distal end  62  is expanded, the proximal end  66  of stent  44  contacts distal end  47  of pusher  146 , which then pushes the stent out from within stent sheath  42 . 
     Also illustrated in FIG. 9 is a temporary protective wrapper  150  over graft  50 . The wrapper may be adapted to be split or otherwise peeled or torn away prior to inserting the delivery system within the body lumen. Such a temporary wrapper protects the graft and keeps it compressed against the sheath until just prior to deployment. Such a wrapper may be heat-set in place during a heat setting step that also may heat-set the graft into a low profile. This wrapper may be particularly useful in an embodiment of this invention wherein the proximal end of the graft is not attached to the sheath at all (not shown), but instead remains in its heat-set position wrapped about stent sheath  42  until stent  44  starts to expand. The heat-set configuration is undone as stent  44  expands and blood flows between graft  50  and stent sheath  42 . 
     Further illustrated in FIG. 9 is an embodiment wherein suture  168  is secured to graft  50  rather than being secured through tie-holes in stent sheath  42 . In this configuration, when suture  168  is broken, it remains connected to graft  50  rather than to sheath  42 . Suture  168  preferably comprises a resorbable suture material to reduce risk of embolism from the trailing suture segments. 
     In yet another embodiment, the suture used for attaching the graft to the sheath may be a slip knot  200 , such as shown in FIGS. 10A and 10B, that may be untied to release the suture. Exemplary slip knot  200 , as shown in more detail in FIG. 10B, may comprise a first suture  202  and a second suture  204  that each hold down graft  50  and are secured to stent sheath  42  at a connection point, such as at tie holes  72 , and a third suture  206  that has a slipped end  208 . Slipped end may be attached to pusher  246  (as shown in FIG. 10A) or to the inner core (not shown) so that relative movement of the stent sheath relative to the pusher or inner core unties the knot, or the slipped end may be trailed as a drawstring outside the body lumen. First suture  202 , second suture  204 , and third suture  206  each also have free ends  203 ,  205 , and  207 , respectively, that are tied together in slip knot  200 . Knot  200  as illustrated in FIG. 10B is a modified sheet bend, shown prior to tightening, for clarity. Other slip knot configurations known in the art may also be chosen, based on suture properties and manufacturing considerations. 
     To provide a slip knot embodiment such as shown in FIG. 10A, slip knot  200  may be first created at free end  203  of first suture  202 , free end  205  of second suture  204 , and free end  207  of third suture  206  having slipped end  208  attached to pusher  246 . Then the ends of sutures  202  and  204  opposite free ends  203  and  205 , respectively, are threaded inside sheath  42  and out through through-holes  74 , and pusher  246  is threaded inside sheath  42  into its position for deployment into the body lumen. Sutures  202  and  204  may then be secured to graft  50  and tie-holes  72  as shown in FIG.  10 A. 
     Attachment means other than sutures may also be used for securing the proximal end of the graft to the sheath, or as mentioned above, the sheath may be left unattached at the proximal end, constrained about the sheath only by the effects of a heat-set step. Alternatively, the fluid dynamics of opposing blood flow may be sufficient to retain the proximal end circumference of the graft and preclude flow obstruction by the graft both prior to and during deployment. 
     Distal end  62  of stent  44  may extend distally of distal end  64  of graft  50  as shown in the embodiment illustrated in FIGS. 3A-C and  7 A-D, or the graft distal end may be attached directly to the stent distal end. Where the stent and graft distal ends are attached, tip sheath  60  is unnecessary, but tip  58  may still be present. Where stent distal end  62  does extend distally of graft distal end  64 , the stent distal end may be secured to core  48  by means other than tip sheath  60 , as shown in FIG.  3 B. For instance, as shown in FIG. 11, crochet weave  80 ′, having a distal end  90  pinched within slot  91  in catheter tip  58  and a proximal end  92  threaded into through-hole  74  in stent sheath  42  and trailed proximally outside the body lumen to be pulled like a drawstring, can be used in accordance with the general crochet weave configuration described herein earlier with respect to FIG.  4 B. 
     Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.