ENDOLUMENAL STENT-GRAFT WITH LEAK-RESISTANT SEAL

Abstract: An implantable medical device has a tubular member and a sealing member secured to an outer surface of the tubular member. The tubular member is expandable to engage an endolumenal wall and has a lumen for providing an artificial conduit for flow through an endolumenal space defined by that wall. The seal member occludes flow around the tubular member between the outer surface and the endolumenal wall. One suitable tubular member for use in the present invention is a stent-graft which may be bifurcated for use in protecting vascular wall malformations adjacent to vascular bifurcations against endolumenal pressure and flow. The seal member may be a flange that is oriented on the outer surface at one end of the tubular member as a one-way valve against flow. Multiple seal members may be used, either on opposite ends of the tubular member or in series at one end therof. Where anchors are used to secure the tubular member to the endolumenal wall, the seal member is positioned to protect against flow through leakage paths formed at localized areas of deformation in the tubular wall adjacent to the anchors. One or more seal members may also be used with two or more tubular members to prevent flow through endolumenal spaces that remain open to flow due to gaps between the multiple, parallel tubular members.

Description: ENDOLUMENAL STENT-GRΛFT WITH LEA K-RESISTANT SEAL TECHNICAL FIELD This invention is a surgical device assembly. More specifically it is an implantable medical device for providing an artificial conduit for biological flow through an endolumenal body space that is defined by an endolumenal wall, and also for substantially isolating that flow from the endolumenal wall. BACKGROUND ART Treatment or isolation of vascular a euiΛ sms or of \ essel walls which have been thickened by disease has traditionally been performed \ ia surgical bypassing with vascular grafts. Shortcomings of this invasive procedure include the morbidity and mortality associated with major surgery, long patient recovery times, and the high incidence of repeat intervention needed due to limitations of the graft or of the procedure. Minimally invasive alternatives involving stents or stent-grafts are generally known and widely used in certain types of treatments. Intralumenal stents, for example, are particularly useful for treatment of vascular or arterial occlusion or stenosis typically associated with vessels thickened by disease. Intralumenal stents function to mechanically hold these vessels open. In some instances, stents may be used subsequent to or as an adjunct to a balloon angioplasty procedure. Si nl -gulls o| sicni sii ik line, i p.ii liLii lai Is iisclul l i ih hcalnioni l . be chai eteiird as a sac loimc the dilatation ol tl all oi a'i aitciy, vein, or vessel. Typically the ancurysm is filled with fluid or clotted blood. The stent-graft provides a graft layer to reestablish a flow lumen through the aneurysm as well as a stcnt structure to support the graft and to resist occlusion or restenosis Treatment of a bifurcation site afflicted with such defects as an occlusion, stenosis, or aneurysm is a particularly demanding application lor either stents or stent-grafts. A bifurcation site is generally where a single lumen or artery (often called the trunk) splits into two lumen or arteries (often called branches), such as in a ""Y" configuration. For example, one such biluication site is found within the human bod> at the location where the abdominal aoitic branches into the left and right (or ipsalateral and contralateial) iliac aiteπes When a defect, such as an aneurysm, is located very close to the bifurcation of a trunk lumen into two branch lumens, treatment becomes especially difficult. One reason for this difficulty is because neither the trunk lumen nor either of the branch lumens provides a sufficient portion of healthy, lumen wall on both sides of the defect to which a siiaight section of single lumen stem or slcnt-graft can be seemed the stem oi steni-gialt must span the bifurcation site and yet allow undisturbed flow through each of the branch and trunk lumens. What is required then is a stent or stent-graft which may be secured to each of the lumen wall a sufficient distance away from the defect and yet is capable of allowing undisturbed flow into each of the branch and trunk lumen. Such a configuration, at least after implantation, generally must the same Y-shape as described for the bifurcation site. Prior to implantation, the stent or stent-graft may have a Y-shape or may have a modular construction which is assembled into the desired shape as it is implanted. As we shall see, deployment of implants adapted to meet these needs is also problematic in that they must be deployed and seemed in thiee different In men w Inch uie impossible lo ccess from a single tin ccimn l-uiihci. to lacililalc iniuluiuciui c l- \ ci > ilmuigh a IHKU s loituous \ asLiilaluic. ihc mi plant must be capable of being compiesscd into a small diameiei oi piofiic and then expand to a predetermined geometry adapted to engage the vessel wall. However, sometimes this expanded condition is insufficient to completely occlude flow over the device and into the endolumenal defect. Prior devices that deal ith treatment at a bifurcation site uiihin the body generally include grafts, stents. and stcnt-grafts m either a single-piece or modular configuration. The use of tubular grafts for treating defects at bifurcation sites has been known for some time. For example, in United States Patent Nos.3.029.819 to Starks, 3.096.560 to Liebig.3,142.067 to Licbig. and 3.805.301 lo Liebig. These grafts arc pically made of woven fabric or other synthetic material and, because they have no supporting stent structure, typically involve excising the defected segment and suturing the fabric graft in place using common surgical procedures. A number of bifurcated graft implants have been developed which use some limited means of supporting the one-piece bifurcated graft structure. Examples of such bifurcated grafts include United States Patent No.4.562.596 to Kornberg; United States Patent No 5,489,295 to Piplani et al . and U S. Patent Nos.5,360,443, and 5,522,880, both to Barone et al. As with all such one-piece devices, the delivery of the graft implant is complicated by the fact that each of the trunk and two legs of the graft must be positioned into their respective lumen and then secured into place. This requires the branch legs to be compressed together for delivery through one of the lumen and requires difficult maneuvering of the branch legs to get them unfolded and untwisted into place within their respective branch lumen This type of delivery requires the graft sections to be highly flexible so that its components may be manipulated as required and requires a larger profile. This demand for high flexibility often results in unsupported graft sections that may be subject to kinking, folding, collapse or the like Hiluualed slcnl ιle\ ices also been disclosed, uch as m micd States I'aki 1 No l. ( W 1,071 'o λ'lac ucgoi, loi example wlm.ii di ^l - ^ s a a i -picec bitmcatcd slcnl loi mscilion into a bil cating vessel, oi United Va s Patent No 5,342,387 to Summcis Some implant devices have further used a modulai approach, primarily for purposes of enhancing delivery. Examples of modular implants uch as stents or grafts include PR 2678508 Al, United States Patent No 5.507.769 tυ Mann et al, EP 0(551) (179) A 1 to Palmazetal.; WO 95/(215)92 (International Application number PCT/US95/(014)66); EP (068)6 (379) A2. EP 0 (696) (447) A2; and United States Patent No.5,562,724 to Vorwerk et al While these modular devices tend to offer a measure of improved delι\ery. continuing problems may include a ccita amount of leakage aiound the openings of the device or at the modulai connection, as well as increased compiesseα piofiles. and not optimized flexibility, kink-resistance, and axial stiffness. Another problem associated with the endovascular repair of aneurysms is postprocedural leakage into the aneurysm sac. Katzen et al.. Initial Expei tence Performing Combine Surgical Inlerventional Procedures in ihc Inienentional Suite (1996) J Endovasc Smg.3 467-468, discloses the tieatmcnl . patients Ibi abdominal aortic aneurysms (AAAs) using coveied (Dacion oi pσlytetrafluoroethylene) multisegment Z-stents; approximately one third of the patients experienced postprocedural leakage. Repair cases of AAAs using the White-Yu endovascular graft were described in White et al., Endoleak Following Endoluminal Repair of AAA' Diagnosis, Significance, and Management (1996) J. Endovasc. Surg 3- 339-340, this technique resulted in leakage around the graft 78% of the time. Chuter et al., Bifurcated Stent-Grafts for AAA 3-} ecu Follow- Up (1996) J. Endovasc. Surg.3.453 , describes the observation of persistent perigraft leakage 12% of the time in a late portion of patients treated for an AAA using a bifucated stent-graft. Parodi et al. Long-term Follow-up of AAA Endoluminal Repair (1996) J. Endovasc Surg.3.335, cites leakage as one of the primary factois causing caily lailuies of aoitic tube giaft icplacemeni tieatmcnl of nig ei l liei pi ox i ma l si enl fi xat ion oi ;ιm '. oi l i. >s"'l ;; ι . ' < pei n n a l t l eakage is the only cued cause i n late lai l ui es Phe postprocedui al leakage pioblem has pei sisted in mor e i cceniK developed systems for AAA treatment. Moore et al., in Transfemoral Endovascular Repair of Abdominal Aortic Aneurysm ■ Results of the Son/} American EI- Phase I Trial (April 1 996) J Vase. Surg.. 543-552, disclose an endovascular grafting stem (ΕGS) consisting of an endox ascular prosthesis, an endovascular deployment assembly and an expandable introducer sheath developed by Endovascular Teclmologies for the treatment of A AAs Moore ct al discloses postprocedural leakage for this device, as initially detected, in 44% of the patients; persistent leakage w as observed in greater than 20% of the patients An endovascular grafting sx tem is further described in Dereime et al Endoluminal Treatment of Abdominal Aortic Aneury sm with the Corvita Endovascular Graft. Results of a Single-Center, Prospective Feasibility Study of 90 Patients (1996) J. Endovasc. Surg. 3:453-483. Dereume et al. describe a system composed of a metallic self-expanding braided wire stent and an inner liner comprised of polycarbonate methane micro fibers. Among patients treated with this graft, 38% presented some postpi ocedural leakage, according lo the Dereume et al. disclosure. In short, the prior art does not disclose a system for the endovascular repair of AAAs that has adequately addressed the problem of postprocedural leakage. From the foregoing discussion it is evident that it would be desirable to have a stent-graft device for treating vessel wall aneurysms by endolumenally isolating the abnormal aneurysmal w all from blood pressure, and w hich does not allow for substantial leakage flow around the outer peripheπ, of the deuce SUMMARY OF THE INVENTION The present invention is an implantable medical device for delivery to an endolumenal body space that is defined by an endolumenal w all and for providing an artificial conduit for flow through the endolumenal body space I e device pi e fci ahl v is adapted l ' oι dcl ι \ cι \ to ,: • ) i n t i .i s asui lai l egion o i .a areui v MD and pi o\ ides a condui t thuuigh that i eg ion h i l e i mee t i ng i lk ai ... ..ι > - ϋ oin the intralumenal pressure. In one variation of the invention, the implantablc medical deuce has a tubular member and a sealing member. The tubular member has a tube wall with a length, two opposite end portions with a central portion therebetween, and an outer surface. The outer surface has a diameter and shape dimensioned to substantial!) engage at least a portion of the endolumenal wall. Furthermore, the tubular wall defines a lumen that extends along the length and that provides a conduit for flow through the endolumenal body space. The seal member is secured to the outei surface and is adapted to occlude leakage flow externally around the tubular wall between the outer surface and the endolumenal wall when the tubular member is deployed w ithin the endolumenal body space. In one mode of this variation, the seal member is an occlusive cuff that forms a flange as a one-way valve over the conduit tubing member ' s outer surface. In another mode, the tubular member has a radtalh collapsed condition such that the outer surface has a reduced diameter which is dimensioned to be smaller than the endolumenal diameter. The tubular member of this mode is adjustable to a radially expanded condition such that the outer surface has the first diameter and shape for engaging the endolumenal wall. This mode allow s for delivery of the tubular member when in the radially collapsed condition, and implantation of the tubular member w hen in the radially expanded condition. In still another mode of this variation, the tubular member includes an anchor and the seal member is adjacent to that anchor. It is believed that the anchoring of endolumenal grafts may create leakage paths around the outer surface of the graft. The seal member is positioned to occlude such leakage paths. Λ ol hei \ a nat i n o f t he i m ent ion is an mi plan la hie n ice ; real dev ice dial has a l ubu l ai membei . w hich i s a .stciU-gu l l. i n com bmal ion u i i n a seal mem bei eι the outside sui face of that stenl-gra l 1 he stent grail includes a flexible, tubular graft member, and also a stent member which is coupled to an outer surface of the tubular graft member. The stent member has at least one circumfercntially reinforcing member that is constructed of relatively rigid material compared to the tubular graft member. In a further mode of this variation, the stent-graft which makes up the tubular member is bifurcated, which provides primary utility for implantation in lower abdominal aortic bifurcations which have aortic wall aneurysms. It is believed that leakage into aneurysms over bifurcated implants of this type may occui over cither the main body end. or over one or both of the legs of the bifurcation Therefore, the seal member may be positioned adjacent the distal end of the main body of this stent-graft, or adjacent the end of one of the legs of the bifurcation, or both. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of an implantable medical device of the present invention wherein a seal membei is secured to an outer surface of a tubular member aαjaceπt an end ofthe tubπiar member. Figure 2 is a perspective view of a further embodiment of the implantable medical device of Figure 1, wherein two similar seal members are shown secured to outer surfaces of two opposite end portions of the tubular member with one seal member in an expanded condition relative to the other seal member. Figure 3 is a perspective view of the implantable medical device of Figure 1 , wherein the tubular member is shown in a radially expanded position within an intravascular region of an aneurysm. I iguie -1 is ,ι peispeclix e implanlable mcdk.il e that is lesiiained in a collapsed slate I'iguie 5 is an end view olThc lestrained implant ol 1 ig e 4 Figure 6 is a perspective view of the assembly of Figuie 4 with the restraint released and the implant in an expanded state. Figure 7 A is an end view ofthe assembly of Figure 6 Figure 7B is a bottom plan view ofthe restraining member ofl igure 7A. Figure 8A shows a restraining member retraction mechanism where the mechanism is in an unactuated state. Figure 8B shows the mechanism of Figure 8A in an actuated state. Figures 8C shows a retraining member retraction mechanism according to yet another variation here the mechanism is in an unactuated state Figure 8D shows the mechanism of Figure 8C in an actuated state Figure 9 A is a perspective view of another variation ofthe implant in conjunction with the restraining member of Figure 4. Figure 9B is a perspective view of a further variation ofthe implant in conjunction with the restraining member of Figure 4. Figure 10A illustrates the restraining and coupling member of figure 4 and the pull direction for removing the coupling member from the icstrainmg member Figure 10B shows the assembly of Figure 10A with the coupling member loosened to illustrate the chain knots used according to one variation. Figure IOC diagrammatically represents release ofthe assembly of Figure 10A or 10B as the coupling member is pulled in the direction shown. Figures 11A, 11B, 11C, 11D, 1 IE and 1 IF diagrammatically show a procedure for loading an expandable stent-graft into a restraining member prior to endolumenal delivery. Figure 12A diagrammatically shows delivering a restrained implant to a desired site in a mammalian body lumen with the coupling member configured as shown in Figures 10A-10C. I mine 12B is a sectional \ lew ol 1 igme I \ lak. I i 1 m I K U!i I " * I iguie lit shows an allunak nuihip iLsiiaiiiu _. ilk ilk in kineiit loi thai shown m 1 iguie 12A Figuie 13Λ diagiammatically shows paitial dcplo meni of the implant assembly illustrated in Figure 12A showing progressive expansion in a direction away fiom the distal end ofthe illustrated guidewirc (i e . toward the illustrated hub) Figuie 13B is a sectional view of Figuie 13A taken along line PB-13B Figure 14A diagrammatically shows full deployment ofthe implant assembly illustrated in Figure 12A Figures 15A, 15B, 15C nd 15D diagrammatical!) show deplounent of a lestiaincd implant accoiding to another variation wheie the coupling membei configuration piovides release fiom the middle poition oi the mplant o .twaid toward the implant ends. Figure 16 illustrates one coupling member configuration for deployment as shown in Figures 15A-15D Figure 17A is a perspective view of a bifurcated stent-graft Figuie 17B is a top plan view ofthe biluicated stent-g alt i I ig ic 17A Figure 17C is a cioss-sectional view taken along sectie I In e 1 " t -I 7C depicted in Figure 17A Figure 17D is a cross-sectional view taken along section line 17D-17D depicted in Figure 17A. Figures 17B and 17C are respectively top and bottom plan views ofthe implantable medical device of Figure 1/A Figure 18 is a front view ofthe assembled bifurcated stent-graft of Figure 17A placed at a bifurcation site within the vasculatuie of a body Figure 19 is a perspective break-away view showing a close-up of one construction ofthe stent anchoring apexes with a seal member secured adiacent thereto I iguie 2 Λ is a peispecli e hιeak-aw av \ w ' OW ■ .: el . - ιp o I a , ) a I te i native eon si ι net ion ol the stem ai hoi mg a|v \ ^ . » .. _ι..:ι _ , e l membei seemed adiacent theieto Figure 20B is a longitudinal cioss-scctional view ol a generic iubulai member with anchor and seal member deployed within an endolumenal space. Figure 21 is a cross-section view ofthe stent-graft tubular member taken along section line 21-21 depicted m Figure 17B Figure 22 is a cross-section view ofthe stent-graft de cied i iguie 17Λ. taken along section line 22-22. Figure 23 is an enlarged partial cross-sectional view ofthe contialateral leg connection depicted in Figure 22. Figures 24 and 25 are enlarged partial cioss-section::' views o " " alternati e constructions ofthe receiving lumen Figure 26 is a partial perspective view of an alternate scalloped construction ofthe proximal region ofthe contralateral leg component. Figures 27A and 27B are cross-sectional views taken along section line 27A-27A as shown in Figure 17A depicting a free state and a forced state respectively. Figures 28Λ and 28B aie cioss-sectional views take:' along section line 28A-28A as shown in Figure 26 depicting a free state and a forced state respectively. Figure 29A is a front view ofthe unassembled components of a variation ofthe graft element to be combined with a stent member to form a tubular member variation for use with the current invention. Figures 29B and 29C are respectively the front view and top v lew ofthe assembled graft elements. Figure 30A is a front view ofthe unassembled components of an alternate construction ofthe graft element. Figure 30B is a front view ofthe assembled graft element accoidmg to the alternative construction of Figuie 30Λ Figures ~ \ \ Λ t hi ough 3 1 F diam annnat ical l} show the deplov -at of the t o components of a hi I m ealed stent- i al ' t cons' -ue ted ae^or eiing .to i.k pi inei les o the present invention using a type of restraining membei loi elcpl menl. Figures 32A through 32D diagrammatically show the deployment of the tw o components of a bifurcated stent-graft constructed according to the principles of the present invention using an alternate type of restraining member which provides release from the middle portion of the implant outw ard toward the implant ends. BRIEF DESCRIPTION OF THE EMBODIMENTS The present invention is an implantable medical device assembly which has a tubular member designed to engage a length of endolumenal w all that defines an endolumenal space, and which has a seal member on the outer surface of the tubular member that occludes flow around the tubular member between its outer surface and the endolumenal wall. It is believed that this invention is particularly useful when the seal member is secured to the outer surface of a stent-graft as the tubular member. This variation is particularly useful in the treatment of intrav ascular aneurysms, wherein the seal member occludes leakage flow around the stent-graft and substantially isolates that flow from the dangerous, abnormal aneurysmal wall. It is further believed that the broad aspects of tubular member-seal member combination of the invention has utility in the prevention of leakage flow around the outer surfaces of implantable endolumenal medical devices. A first implantable medical device ( 1 ) variation of the present invention is depicted in Figure 1 , which shows tubular member ( 10) and seal member (20) secured to tubular member ( 10). Tubular member ( 10) is shown in Figure 1 to include a tubular wall ( 12), which has a length L defined by two opposite end portions ( 14, 16) and central portion ( 1 5) between those end portions. Tubular wall ( 1 2) also defines a lumen ( 1 7) which extends along length L. and further includes an outer surface ( 1 ). Seal mem he i ( 20) is show n i n I igui e I s an oec ' us .. i l I " , w eh has a Iii si cul l end (22 ) seemed to outei sui laee ( \ <S ) ol luhuhu w , i I 2 ). aικι hich also has a second cuff end (24 ) thai includes al least a portion w hich is unsecured lo form a flange (26). In this configuration, flange (26) forms a one-way valve that circumferentially surrounds tubular member ( 10) and occludes flow around tubular wall ( 12) in the direction from the first cuff end ( 22) to the second cuff end (24) when tubular member ( 1 0) is deployed ithin a radial lv confining endolumenal space. More particularly in Figure 1 , flange (26) is show n in a flared condition, which condition may be its relaxed geometry or may be a geometry imparted thereto by How in the occluded direction, depicted by an arrow in Figure 1. In the case where the flared shape of flange (26) is its relaxed geometrv . flange (26) may include an outward bias to that shape, such that w hen tubular member ( 10) is deployed into an endolumenal space (not shown in Figure 1 ). flange (26) may engage a radially confining endolumenal wall defining that space (not shown) and thereby enhance the reduction of flow around tubular member ( 10) between outer surface (1 8) and the endolumenal wall In one construction, both tubular wall ( 1 2) and seal member (20 ) comprise heat compatible polymers, such that seal membei (20) may be secured to tubular wall (12) with a heat seal. In one mode of this construction, only first cuff end (22) may be brought into contact with outer surface (18) and the heat seal is formed upon generally heating the region of seal member (20). In another mode, seal member (20) may be a heat shrinkable polymeric material, such as a material chosen from the group consisting of fluoropolymers. cross-lined polyolefins such as cross-linked polyethylene, polymides, or combinations thereof. In this mode, heat may be applied only to one end of the seal member (20). w hich shrinks in response thereto and melts to the tubular member (10). It should be further understood that seal member (20) could be secured to outer surface ( 18) in a variety of ways other than a heat seal, as would be apparent to one of ordinary skill For example, an appropriate adhesiv e for the materials chosen loi seal membei (20) and luhulai membei ( 10) --.iv • . ■ n cd in make an aillk n\ e bond then. -between Λllemaliv elv . seal iikin k : (_ ι rriav ha* e a h ictioii lit ovei outci suilace (1 ), as may be ihc case when se.:. mcmivi (20) is heat shiunk onto outer surface (18) but is not actually melted to that surface Phis may be the case, for instance, when seal member (20) and tubular member (10) do not comprise heat compatible polymers Furthermore, some mechanical coupling may secure seal member (20) to outer tube membei (KM An additional seal member (30) is also shown :: Figuie 1 on opposite end portion (16) and secured in an opposite orientation along the longitudinal axis of tubular member (10) when compared to seal member (20). Alternatively to the flange/one-way valve variation of Figure 1. Figure 2 shows implantable medical device (2) to include two similai seal members (60,70) which arc expandable from a first diameter to a second diametei. and which are secured to the outer surfaces of two opposite end portions (54.56) of tubular wall (50). For purposes of illustration in Figure 2, seal member (60) is shown in an expanded condition relative to unexpanded seal member (70) In one preferred construction, seal members (60.70) comprise a h> clrophilic material, preferably a hvdrophihc polvmer or gei-ioam. which expands when exposed to water, such as in blood oi omer w ate; -containing body fluids, and which is adherent to outer surface (58) of tubular wall (50), as would be apparent to one of ordinary skill. In the variation employing this construction, the hydrophilic material has an initially low profile prior to the implantable medical device being deployed into the endolumenal space where seal members (60,70) are exposed to hydrophilic body fluids or other artificially introduced fluids therein. Upon exposure to such fluids, the seal members (60,70) absorb water and expand outwardly from outer surface (58) to create an occlusive effect to flow across the seal members (60,70). While particular variations for the seal member ofthe present invention are herein described such as in Figures 1 and 2, it is to be further appreciated by one of oidmary skill that other seal membei ariations mav be secured to outer su i faces \ ' i m planta bl e cndov asc u lai med ica l dev ices i i liout o c .c ' ' • ". from t he scope o l the i n v en tion For exam ple, a t hrom bogenic malena l ^ h . co l lauen oi Dacron libers may be secured to an outer surface of an implantable crulolumenal medical device and suitably occlude flow around that device for a particular medical application. However, clinical limitations, such as profile, lubricity, traumaticity, or toxicity may dictate the utility of a particular seal member when it is intended to be combined with a tubular member which is designed for a particular application. It is to be understood that one seal member may be used in the current invention, or two seal members may be used on opposite end portions of the tubular member to form a "dual-seal. " as is shown in Figures 1 and 2 for purposes of illustration. ' Phe scope of either variation should be considered to include both seal member variations of Figures 1 and 2. as well as other seal member variations that would apparent to one of ordinary skill. It is believed that, when the implantable medical device is deployed within high pressure vessels such as the aorta, the pressure drop across the outer surface of the tubular wall is high enough at each end portion to cause leakage flow into the central portion of the tubular member. In the " dual seal " v ariation of the present invention, such as that shown in Figure 2. both of these potential leakage paths are occluded. In design variations for treating aortic aneurysms. such as lower abdominal aneurysms, the "dual-seal" variation may be a highly desirable design for this reason. Furthermore, in either case of one end or both ends including a seal member, there may also be a multiplicity of such seal members on a single end. For example, more than one seal member such as seal member (20) in Figure 1 may be used in series on a single end of the tubular member, such as for purpose of providing a redundancy of safety. If, for example, one of the serial seal members fails to provide a sufficient seal, such as for reasons of anatomical abnormalities at that seal, another serial seal member may be properlv engaged to the endolumenal wall and provide the necessary obstruction to leaka e How. \ fuilhei embodiment ol the piesenl invention als an: empl.iies use ol seal membeis. such as seal membei (20) in I iguie I . w nh e.ulh p lc ienulai members lo be placed in paiallel within an endolumenal space In one variation of this embodiment, two parallel tubular membeis such as tubular member (10) in Figure 1 may be wrapped together ith one circumferential cuff. In one construction of this variation, the first cuff end is constricted or heat shrunk to conform to the crease between the oulei circumferential surfaces ofthe parallel tubular membeis 1 ne other, second cuff end is left unsecured to form the flange, wherein the first and second cuff ends for the one-way valve against flow along and between the outer surfaces ofthe two parallel tubular members. In a further variation, each parallel tubular member mav ha e us own seal member secured thereon and still provide suitable flow obstruction, particularly in combination with the other, parallel tube with seal member. For example, when such seal members are constructed with a flare, such as shown for seal members (20) and (30) in Figure 1, they may meet at the "inter-tubular" spaces and thereby form a cross-sectional obstruction against flow through those spaces flow. Therefore, according to the multiple seal member ariations ιust described, all ofthe embodiments ofthe invention should be contemplated to include these variations, even in cases where there may be only one seal member shown on one end portion of a tubular member. Figure 3 further shows the use of one variation ofthe present invention, which is believed to be particularly useful for the treatment of intravascular aneurysms. Implantable medical device .(3) is depicted in Figure 3 with tubular member (80) and seal member (90) deployed within an intravascular region of aneurysm (99). Tubular member (80) includes an expandable tubular wall (82) having one end portion (86) engaged with a vascular wall (97) at a location adjacent to aneurysm (99). Tubular member also includes another opposite end portion which similarly engages vascular wall (97) on the opposite tia sv eise side of aneurysm X> ) l elat i v e t o t he vesse l s longi tu i nal ax i s ( not show n) A cen lul port ion ( 8 1 ) o l l ubu lai mem bei ( SO ) i s located bet w een t he lubu l.ii membei s oppo a le end portions and is shown i n Figui e 3 m partial view t ' entul |X)i lιon (84 ) has a length and an expanded diameter sufficient to substantially span the abnormal wall section that comprises aneurysm (99) (not shown). In one desirable construction, tubular member (80) may comprise a stent- graft which is deliverable to the intravascular region of the aneurysm (99) in a radially collapsed condition and which is adjustable to the radially expandable condition shown in Figure 3. Such radial adjustment may be actuated by balloon expansion of the stent-graft structure, or the stent-graft structure itself may be sel f- expanding, such as upon removing a radially confining member from the stent- graft which has a bias to the radially expanded shape Variations of a particularly desirable stent-graft embodiment are provided in detail in Figures 14A-32D Seal member (90) is shown in Figure 3 to be secured to an outer surface of end portion (86). Seal member (90) is an occlusive cuff of a similar type to that shown in Figure 1 , wherein first cuff end (92) is secured to the outer surface of tubular member (80) and second cuff end (96) is unsecured to form a flange (95). Phe particular orientation shown for the adjacent first and second cuff ends (92.94) along the longitudinal axis A of end portion (86) allow for flange (95) to provide a one-way valve against flow in the direction from end portion (86) toward central portion (86). Tubular member (80) thus provides an artificial conduit for flow through the region of aneurysm (99) (shown with representative arrows) and aneurysm (99) is substantially isolated from leakage flow across the one-way valve of seal member (90). Tubular member (80) is further shown in Figure 3 in a radially expanded condition wherein the outer surface of the tubulai wall (82) has a dimension and shape sufficient to engage wall (97). In fact, the expanded condition is actually shown here to be oversized, which is often desired in order to effectuate enough force at the wall to hold the tubular member (80) in its deployed position along the longitudinal axis of lumen (97) However, in such a design, a w rinkle such as w i ink le ( SS ) mav i csull due to the undei -expanded stale ol ihc mbulai membei I his mav pi esenl a leakage path to allow flow lo pi opagaic a .ong ;. e outei sui l ace oi tubulai member (80) and into aneιιι > sm (99) Seal member (90 ) how evci , is shown to be positioned with flange (95) ovei a portion of that wrinkle (88) and ith first cuff end (92) secured over the outer surface of the end of the leakage path which is wrinkle (88). In this mode, the leakage path is occluded and any flow that would otherwise propagate therethrough is captured by flange (95). The following portions of the description relate to Figures 4-32D, and are directed toward variations of two highly desirable embodiments of the present invention. The particular embodiment of Figures 4- 1 6 relates to variations of a particular assembly for delivering the implantable medical dev ice of the present invention when the tubular member of the device is self-expanding from a first radially collapsed condition to a second radially expanded condition. The particular embodiment of Figures 17-32D relates to variations of a particular tubular member construction for the implantable medical device of the present invention, which tubular member construction is a highly desirable, modular stent-graft Coisel Dchvciv oMmplaiitahlc Medical l)e e Ixolening to diawmgs 4-16 detail vvhciein numeuls inJicale like elements, delivery systems for delivering implants oi devices, such as stents 01 stent-grafts, to a desired site in mammalian vasculature aic shown The delivery systems ofthe present invention generally include a lestiammg member that is adapted and configured for surrounding at least a portion ol a collapsed oi compiessed implant and a coupling mcmbeι(s) loi leleasablv coupling portions ol the restraining member to one another to maintain the implant in us collapsed oi compressed state. Referring to Figures 4-7, an implant delivery sv stem suitable for use with the piesent invention is shown Deliver} system (100) geneiallv includes a lestiammg member (102), which as shown may be in the form of a sheet of material, and a coupling member (104) for releasably coupling portions ofthe restraining member to one another. The restraining member portions that are coupled may differ than those illustrated, but preferably are selected to maintain the implant, such as self-expanding stent-graft (106). in a collapsed or compressed stale as shown in Figures 4 and 5 vvheie the resttaming member ( 102) is shown in the foim of a tube In the illustrative variation, the coupling membei (104) is shown as a filament or thread-like element which prevents the restraining member (102) from rearranging to a configuration where the stent-graft (106) could expand to its expanded state. The implant may be collapsed in any suitable manner for placement within the restraining member (102), For example, the implant may be folded or radially crushed before placement within the restraining member (102) as will be described in more detail below. As shown in Figuies 12-14. a delivery assembly (108), which includes the restraining member ( 102) and the stent-graft ( 106), has relatively small cross-sectional dimensions which facilitate endolumenal delivery ofthe assembly to a site where the natural lumen diameter mav be smaller than the expanded diametei ofthe stent-graft ( 106) elei ling lo I iguies 6 and 7Λ. the assemhb (I K ) ι shown eplovcd state altei lemo al ol the coupling membei ( I 04) I he ic s c i mug : ; ... ml vj ( I () 2) may be fixedly secured to the stenl-gralt (106) so thai the two components icmam attached after expansion at the desired deployment site. I wo or more sutures (110) may be used to fixedly attach the restraining member (102) lo the stent-graft (106) as shown in Figures 7A and 7B. Although one arrangement ofthe sutures (110) is shown in Figure 7B other aπangcmcnts may be used The attachment between the restraining member and the implant prei ' erablv is made to prevent significant movement between the restraining member and stent-graft after deployment which could disrupt endovascular fluid flow. Although other configurations ofthe restraining member (102) can be used, a preferred configuration is a generally rectangular one as sho n m Figure 7B. The restraining member configuration may vary depending on the confirmation ofthe implant. For example, in the case where the restraining member is used in conjunction with a modular bifurcated stent as will be described below, the restraining member may have a similar rectangular configuration as that shown in Figure 7B, one that have two differentlv sized rectangular portions arranged to mate with the regions of different diameicr (trunk and leg) or another configuration that would maintain the implant in a collapsed stent when secured. Returning to Figure 7B, the restraining member may be described as having side margins (112) that extend between the ends (114) ofthe member. Eyelets (116) are disposed along the side margins so that the coupling member (104) may be laced or threaded therethrough. The eyelets may be in the form of through holes (118), which may be formed by a uniform-diameter puncturing device or by other means such as laser-drilling Alternatively, the eyelets may be formed by loops (120) which may be attached to the side margins (112) or formed by other means as would be apparent to one of ordinary skill in the art. It is further desirable to have structural reinforcement at the side margins (112) to minimize or eliminate the possibility ofthe coupling member (104) fiom teai ing the icsiuining membei ( 102) when uiulei load Uemloieed side nun m n mav be loi med bv l kling a portion ol the icsli inii' ■ membei ι I ( J 21. > . eι a icmlbiccmenl membei (122). such as a small diametci suluie. which mav behe.it bonded between the two layers of sheet material With this construction, a relatively low profile bead of material along the side margins (112) prevents or minimizes the possibility of tear propagation and. thus, accidental uncoupling of the restraining member (102) The small diameter suture (122) mav comprise cPTFE, for example. As the restraining member (102) constrains a collapsed self-expanding stent-graft, for example, forces resulting from stored spring energy in the collapsed stent-graft (106) will be acting on the restraining member (102) when it is configured for deliver I hus, the restraining member (102) may compπse a material which is creep resistant and can withstand icquued loads without stretching over time. The restraining member (102) may comprise, for example, ePTFE, which is believed to provide suitable creep resistance, flexibility, and biocompatibility in a thin sheet form which can be heat bonded. Other materials also may be used including polyethers such as polyethylene terepthalate (DACRON® or MYLAR®) or polyaiamids such as EVLΛR® The thread-like coupling membei (104) mav also comprise ePTFE Sutures of polyethers such as polyethylene terepthalate (DACRON® or MYLAR®) or polyaramids such as KEVLAR® or metal wire comprising nitinol, stainless steel or gold may also be used for the coupling member (104). The coupling member (104) may simply extend to form a remote pull line as will be discussed below. Alternatively, a metallic pull line, such as one comprising stainless steel may be coupled to a nonmetallic coupling member (104) such as one comprising ePTFE. The coupling may be made by folding the end ofthe metallic pull line back upon itself to form an eyelet and threading the coupling member therethrough and securing it to the eyelet with a knot. It is further noted that the width ofthe restraining member, when in a flat orientation as shown in Figure 7A preferably, is less than the diametci ofthe implant I pieallv the , estiauung iikinbei w idlh w ill be les than /suit 10mm (iv pically about 25- ()mm when the ice is si/ed loi thoiacic aoita applications), and moie typically less than about I 5mm I he sheet ol matciial piefeiably has a thickness less than 010 inch (0254mm) and moie preferably less than .005 inch (0.127mm). In addition, the length ofthe restraining member picfcrably is less than or equal to that ofthe implant A retiaction assemblv may be piovided to retract the restiainmg membei during expansion ofthe implant, so that the length ofthe icstraining member is maintained to be about equal to oi less than that ofthe implant. The expandable portion ofthe implant may undergo minor amounts of shortening along the axial direction due to the expansion thereof m the radial direction, which may lead to an ovetlap ofthe restraining membei at the ends ofthe implant, but for the use of some type of retraction assembly m these situations The retraction assembly minimizes or eliminates the risk ofthe restraining member extending beyond the implant and interfering with any channel formed by the implant, or any fluid flowing therethrough after expansion Referring to Figures 8A.-8D illustrative retraction assemblies or mechanisms are shown In Figure 8 \ a letraction assembly (340) includes a biocompatible filament (342) which includes a portion that is tied or otheiwise fixed, as shown at an attachment point (348), adjacent to the end ofthe restraining member (102). Filament (342) is passed underneath the members forming the first or end helical turn ofthe stent (126) and looped under or otherwise slidably secured to a portion ofthe second , third or another helical turn other than the first helical turn such a an apex (344) in a second turn The other end portion of filament (342) is further fixed, by tv mg or some alternative to tying, to a portion ofthe stent that is circumferentially spaced from the attachment point (348) or apex (344), for example, such as an apex (346) ofthe same helical turn. Preferably, the filament (342) is looped through an apex ofthe second helical turn and tied to an apex (346) which is adiacent to the looped apex (344) as shown in Figuie 8A I i g u i e S. \ show s t he ste m a com pi essed stale I pon ex paik 'on o f t he stem, as menlioned above, the membei s ol the stent expand to elieet lac udial expansion of the stem, as shown in Figure 8B Because the distance between apexes (344) and (346) becomes greater upon expansion of the stent, and because the filament (342) is relatively unyieldable and inelastic, the distance between the attachment point (344) and the apex (348) necessarilv" decreases. The result is thai the end of the restraining member ( 102) is retracted with respect to the stent ( 126). as shown in Figure 8B. Thus, the retraction along the longitudinal axis of the restraining member is driven by the expanding distance between adjacent apexes in this variation. Although only one retraction mechanism is shown, another similarly configured and arranged retraction mechanism may be used at the other end o the restraining member. Figure 8C shows another variation for a retraction assembly. The view of this assembly as that shown in Figures 8A and 8B are taken from a location between the generally cylindrical graft and stent looking radially outward. In contrast to that shown above where one end portion of a filament is secured to the restraining member and another to a portion of the stent that circumferentially mov es during stent expansion, the other end of the filament is secured to a portion of a stent that moves generally parallel to the longitudinal axis of the stent (axially) as the stent expands. In this variation, at least one apex (364) of an end helix of the stent member (126') (which differs from stent (126) in that it includes eyelets which may be formed as shown in the drawings) is made shorter than the majority of apexes (366). A filament (362) is tied or otherwise fixed at one end to apex (364), and at the other end, to one end portion of the restraining member ( 1 02). As shown in Figure 8D, upon radial expansion of the stent, inwardly positioned apex (364) retracts to a greater extent in the longitudinal or axial direction than the full height apexes (366). This relative greater retraction directly translates through filament (362) such that the end of the restraining member ( 102) is retracted relative to apexes (366). As described above, another similarly i i onsti ueled leluetion mechanism mav be piov ided .n ihc o'. ' k end < > cstianung membei Retuining lo Figure 4, one stent-gult consliuclion thai mav be used m conjunction vvilh the delivery systems disclosed heiem is sho n Stent-graft ( 106) generally includes a thin-walled tube or giaft membei ( 124). a stent member (126), which can be a self-expanding stent. and a ribbon or tape member (128) for coupling the slent (126) and graft (124) members togelhei I he ste ( 126) and giaft (124) members may be heat bonded togelhei, thus sealing m portions ofthe stent member (126) that are between the tape member (128) and the graft meniber (124). The mechanical properties ofthe stent-graft (128) mav be customized, for example, through materials selection, by varying the structural pattern ofthe stent member, vaiymg the thickness ofthe tape (128) and gialt ( 12-) membeis. and varying the pattern with which the tape member contacts the tent and graft members. As shown in Figure 4A, the tape member (128) may cover only a portion of the stent member (126) as it follows the helical turns of the undulating stent member With this construction, regions ofthe stent membei do not interface with the tape member when the stent-graft is in an uncompιcs>cd state, for example 1 his is believed to advantageouslv, reduce shear stresses between the stent member (126) and the tape member (128) when the stent-graft undergoes bending or compression, thereby reducing the risk of tearing the graft (124) or tape (128) members or causing delamination between the stent (126) and graft (124) members. The tape meniber (128) also preferably has a generallv broad or flat surface for interfacing with the stent (126) and graft (124) members as compared to filament or thread-like structures such as sutures This incieases potential bonding surface area between the tape member (128) and the graft meniber (124) to enhance the structural integrity ofthe stent-graft. The increased bonding surface area also facilitates minimizing the thickness ofthe tape member (128) It h been lound that a tape membei in the loi m o l a , k h he • i - diov n in the duw ings pi ov ides desiicd results I ape member s having widths of 0 025, 0 0 ^ ano. 0 ( i - i nc lk > appl ied lo a stent member having a peak-to-pcak undulation ampl itude ol about 0 075 inch are believed to provide suitable lesults. However, it has been found that as the tape member band width increases, the stent-graft flcxibi hlv gene- •.11 > is diminished It is believed that a tape member width of about one-lou".h < " i ee-loui ths the ampl itude of the stent member undulations, measuied ρeak-t"-:vak. mav be preferred (may be more preferably about one-third to tw o-thirds that ampl itude) to optimize flexibility It also has been found that by positioning one of the lateral margins of the tape member adjacent to the apexes, the tape membei v< ιdιh mav be l educcd without signi ficantly sacrificing apex secui enent \ ai v g the w idth of the tape member (e g , varying width of the tape along the ength of the stent graft) can also result in the adjustment of other structural properties Increasing the width can also potentially increase the radial stiffness and the burst pressure and decrease the porosity of the device. Increasing band w idth can also diminish graft member wrinkling between coupling member tut n The tape member (oi separate pieces thereof) aho ma si ι > round the terminal end portions of the stent-graft to secure the tei m mal vi uons of the graft member to the stent member. Figures 9A and 9B illustrate further stent-graft constructions that may be used with the delivery systems descπbed herein. Refeiτing to Figure 9A. stent-graft (200) is the same as stent-graft ( 106) with the exception that stent-graft (200) includes a filament thai couples stent undulations ι:ι ach?cent turns Filament (202) is laced or interwoven between undulations o the stent meniber and acquires a helical configuration (i.e., it forms a secondaiv helix) in being laced as such Such a configuration is disclosed in PCT publication No WO 95/26695 (International Application No PCT/US95/04000) the entirety of which is hereby incorporated herein by reference The stent-graft (300) show n in Figure 9B is the same as thai shown in I iguie 9 A w ith the exception thai the Ii lament ( ^ .2 ) i intci w ov en betw een undulat ions in the same helical i n of the stent member. ' Flic fi laments (202. 302) ai e of ihc same construction and mav- be of anv appropriate filamentary material which is blood compatible or biocompatible and sufficiently flexible to allow the stent to flex and not deform the stent upon folding. Although the linkage mav- be a single or multiple strand wire (platinum, platinum/tungsten, gold, pal ladium, tantalum, stainless steel, etc.). much preferred is the use of polymeric biocompatible filaments. The flexible link mav be ticd-off at either end of the stent-graft ( 100). for example, by wrapping its end portion around the stent and tying it off at the point at the beginning of the last turn as would be apparent to one ol " ordinarv skill. A percutaneous!) deli ered stent-graft must expand from a reduced diameter, necessary for delivery, to a larger deployed diameter. The diameters of these devices obviously vary with the size of the body lumen into which they are placed. For instance, the stents of this invention may range in size from 2.0mm in diameter (for neurological applications) to 40mm in diameter (for placement in the aorta). A range of about 2.0mm to 6.5mm (perhaps to 10.0mm) is believed to be desirable. Typical ly, expansion ratios of 2: 1 or more are required. These stents are capable of expansion ratios of up to 5: 1 for larger diameter stents. Typical expansion ratios for use with the stents-grafts ofthe invention typically are in the range of about 2: 1 to about 4: 1 although the invention is not so limited. The thickness of the stent materials obviously varies with the size (or diameter) of the stent and the ultimate required yield strength of the folded stent. These values are further dependent upon the selected materials of construction. Wire used in these variations are typically of stronger alloys, e.g., nitinol and stronger spring stainless steels, and have diameters of about 0.002 inches to 0.005 inches. For the larger stents, the appropriate diameter for the stent wire may be somewhat larger, e.g., 0.005 to 0.020 inches. For flat stock metallic stents, thicknesses of about 0.002 inches to 0.005 inches is usual lv sufficient. For the larger stents. the appropriate thickness l the stem flat stock mav be somew hat thicker, e.g.. 0.005 to 0.020 inches. The following example is provided for purposes of illustrating a preferred method of manufacturing a stenl-graft as shown in Figure 6. It should be noted. however, that this example is not intended to limit the invention. The stent member wire is helically wound around a mandrel having pins positioned thereon so that the helical structure and undulations can be formed simultaneously. Whi le still on the mandrel, the stent member is heated to about 460°F for about 20 minutes so that it retains its shape. Wire sizes and materials may vary widely depending on the application. The following is an example construction for a stent-graft designed to accommodate a 6mm diameter vessel lumen. The stent member comprises a nitinol wire (50.8 atomic % Ni) having a diameter of about 0.007 inch. In this example case, the wire is formed to have sinusoidal undulations, each having an amplitude measured peak-to-peak of about 0.100 inch and the helix is formed with a pitch of about 10 windings per inch. The inner diameter of the helix (when unconstrained) is about 6.8mm. (The filament when used as shown in Figures 9A and 9B may have a diameter of about 0.006 inch.) In this example, the graft member is porous expanded polytetrafluoroethylene (PTFE), while the tape member is expanded PTFE coated with FEP. The tape member is in the form of a flat ribbon (as shown in the illustrative variations) that is positioned around the stent and graft member as shown in Figure. 6. The side of the tape member or ribbon that is FEP coated faces the graft member to secure it to the graft member. The intermediate stent- graft construction is heated to allow the materials of the tape and graft member to merge and self-bind as will be described in more detail below. The FEP-coated porous expanded PTFE film used to form the tape member preferably is made by a process which comprises the steps of: (a) contacting a porous PTFE film with another layer which is preferably a film of FEP or alternatively of another thermoplastic polymer; ( b ) heali ng ihe composi t ion obtai ned i n step ( a ) to a temperature above t he mel ting point of the thermoplastic polvmer: (c) slrclching the heated composition of step ( b) w hi le maintai ning ihe temperature above the melting point of the thermoplastic polymer; and (d) cooling the product of step (c). In addition to FEP, other thermoplastic polymers including thermoplastic fluoropolymers may also be used to make this coated film. The adhesive coati ng on the porous expanded PTFE film may be either continuous (non-porous) or discontinuous (porous) depending primarily on the amount and rate of stretching, the temperature during stretching, and the thickness of the adhesive prior to stretching. In constructing this example, the thin wall expanded PTFE graft was of about . 1 mm (0.004 in) thickness and had a density of about .5g/cc. The microstructure of the porous expanded PTFE contained fibrils of about 25 micron length. A 3cm length of this graft material was placed on a mandrel the same diameter as the inner diameter of the graft. The nitinol stent member having about a 3cm length was then carefully fitted over the center of the thin wall graft. The stent-member was then provided with a tape coupling member comprised of the FEP coated film as described above. The tape member was helically wrapped around the exterior surface of the stent-member as shown in Figure 6. The tape member was oriented so that its FEP-coated side faced inward and contacted the exterior surface of the stent-member. This tape surface was exposed to the outward facing surface of the thin wall graft member exposed through the openings in the stent meniber. The uniaxially-oriented fibrils of the microstructure of the helically-wrapped ribbon were helically-oriented about the exterior stent surface. The mandrel assembly was placed into an oven set at 3 1 5°C for a period of 15 minutes after which the film-wrapped mandrel was removed from the oven and allowed to cool. Following cooling to approximately ambient temperature, the mandrel was removed from the resultant stent-graft. The amount of heal applied w i adequate to melt the I I P-coa l iim on the poi ous expanded P i l l Fi l m t hei ebv cause the gu l l and coupl ing membei s to adhei e to eac h othei ' bus. the gu l l membei was adhesively bonded lo ihe innei sin lace ol the hchcal l) -w uppe tape member through the openings between the adjacent w ires of the stent member The combined thickness of the luminal and exterior coverings (graft and lapc members) and the stent member was about 0 4mm Although the invention has been descnbed w ith l eference to the stent-gi al t examples illustrated in the drawings, it should be undei stood that it can be used in conjunction with other devices, stents or stent-grafts having constructions di fferent than those shown. For example, delivery systems described herein may be used in conjunction with bifurcated stents oi stent-grafts as w ill be described in detail below In addition, although a sel f-expanding stent-graft has been described, balloon expanding stent-grafts also mav be used in conjunction with the delivery systems described herein These stent-grafts require a balloon to expand them into their expanded state as opposed to the spring energy stored in a collapsed self-expanding stent. Referring to Figures 10A-C. one slip knot configuration that mav- be used m conjunction with the thread-like coupling membei ( 1 04) w i l l be described The i cstraining member ( 102) is shown w ithout an implant positioned therein for purposes of simplification. Figure 10A illustrates the slip knot in a prerelease or predeployment state, the series of knots are generally flush with the restraining member (102) surface and add very little profile to the construct which is preferred during implant delivery. Figure 10B shows the assembly of Figure 10A with the thread-like coupling member ( 104) loosened to illustrate how the chain knots ( 1 30) may be formed. Figure 10C diagrammatically represents release of the assembly of Figure 10A or 10B The illustrated stitches or knots is releasablc by pulling one end of the line that results in releasing of the cylindrical or tubular restraining member and then deployment of the device This particular stitch is cal led a "chain stitch" and may be cieated with a single needle and a single line A chain stitch is a series of loops oi slip knots that aie looped ihi υugh on anotbei such thai one slip knot prevents the next slip knot I om releasing. W hen the line is pulled lo release a slip knot, ihe foiiow mg slip knot is then leleased and that releases the next slip knot . This process continues during pulling ofthe line until the entire line is pulled out ofthe restraining member. Referring to the drawings, as the unknotted portion or the lead (132) ofthe thread-like coupling member (104) is pulled, such as in the direction shown by reference arrow (134). each consecutive chain knot ( 132) releases the next adjacent one. In the preferred embodiment, the chain knots ( 130) of ihe coupling member (104) are arranged to progressively release the collapsed implant in a direction away from the distal portion ofthe delivery catheter as,shown in Figure 10A and as will be discussed in detail below. Referring to Figures 11A through 1 IF. a method for making an assembly comprising a restraining member with a collapsed or compressed implant therein is shown for purposes of example. Figure 11 A shows the restraining member (102) with its side margins releasably coupled to one another and its left end dilated by a tapered mechanical dilator (402). A small funnel (404) is then inserted into the restraining member (102) as shown in Figures 11 B and 1 IC. The small funnel (404) and restraining member (102) are then mounted onto a pulling frame (410), and a large funnel (406) is fitted into the small funnel (404) as shown in Figure 1 ID. Traction or pull lines (408), which have been sutured to one end of the stent-graft, (106) are pulled through the large funnel (406), small funnel (404), and restraining member (102) with a tapered mandrel (416). As shown in Figures 1 IF, the pull lines (408) are fastened to a tie down post (412) located on a tension screw (414) and then are pulled by the tension screw (414). The stent-graft (106) is then pulled and collapsed sequentially through the large (406) and small (404) funnels, and then into the restraining member (102). Once the stent-graft (106) has been radially collapsed into the restraining meniber (102). which has its side margins coupled together, the pull lines (408) can be removed. The mandrel (416) may be inserted into the restrained implant lo facilitate introduction of another component. In the preferred embodiment, a multilumen catheter ( 136) (Figures 1 14) is introduced through the center o ihe compressed Mem -gr t ( Kid ) ;uκ | j s used to del iver the rad ial ly restrai ned stent-gi ali to the desu ed endolumenal site . l l also is noted that the funnels may be chi lled to fac i l i tate compression of the stent when the stent is made of nitinol . That is, when the stent is made of nitinol, the funnels may be chilled below 0°C or belo the transition temperature (M/) where nitinol is in ils martensitic state. In addition, the stent-graft could be folded first and then reduced in profile by pulling through the funnel and into the restraining meniber. Cooling may be accomplished by spray soaking the stent- graft with chilled gas such as tetrafluoroethane. Micro-Dust ™ dry circuit duster manufactured by MicroCare Corporation (Conn) provides suitable results. The spray canister preferably is held upside down to discharge the fl uid as a liquid onto the stent-graft. A method of deploying an implant wi ll be described w ith reference to Figures 12-14. In general, an implant may be delivered percutaneously with the delivery systems described herein, typically through the vasculature, after having been assembled in the reduced diameter form (see e.g. Figure 4). At the desired delivery site, the implant may be released from the restraining member, thus allowing the implant to expand or be expanded against the lumen wall at the delivery site. Although other devices including stents or stent-grafts may be used. such as balloon expandable stents, the following example will be made with reference to a self-expanding stent-graft, which has the ability to fully expand itself into its final predetermined geometry when unconstrained. More particularly, the following example will be made using a delivery system as shown in Figures 4 and 10A-C and a stent-graft construction as shown in Figure 6. Referring to Figures 12A and 12B, an implant delivery assembly including a collapsed stent-graft ( 106) that is confined within a restraining member ( 102) and, which surrounds a distal portion of the delivery catheter ( 1 36), is shown. The attending physician will select a device having an appropriate size. Typically, the stent-graft will be selected to have an expanded diameter of up to about 20% greater than the diameter of the lumen at ihe desired deployment site. Ihedclivciv caihelei piefeiahlv is a multiliiinen eat .lei I Ik oioximal portion o I the ealhctei (J > (>) is coupled to a hub ( 140). w hk, m lu ts ; mildew iic port (142) f i a guidew ue (142), and a deployment knob (144), w Inch is coupled lo the lead (132) ofthe thiead-like coupling membei (104) Accordingly, when the knob (144) is retracted, the restraining membei (102) is released so that the stent-graft may expand The hub (140) also may include a flushing port (146) as is conventional in the art ' I he stent-gtaft ( 106) is held axially in place prior lo deployment by a proximal barrier (148) and distal barrier (150) which ate positioned around delivery catheter (136) adjacent to the proximal and distal portions, respectively, ofthe restrained stent-graft The proximal and distal barriers (148.150) may be fixedly secured to the multilumen catheter ( 136) to restrict any axial movement ofthe lestrained stent-graft The barrieis preferably are positioned to abut against the stent-graft or restraining member. The lead (132) ofthe coupling member (104) is passed through an aperture (152) in the proximal barrier (148) which is fluidly coupled to a lumen in the delivery catheter (136) so that the coupling member lead (132) can be coupled to the deployment knob ( 144). Figures 12 A and 12B show advancement of the catheter (136) and the restiained implant through a vessel (154) toward a desired site Referring to Figures 13A and 13B, once the restrained stent-graft reaches the desired site (156), the deployment knob (144) is retracted so that the stent- graft progressively expands as shown in the drawings as the coupling member (104) is removed from the restraining member. The coupling member preferably is arranged to facilitate stent-graft expansion in a direction from the distal to proximal ends ofthe stent-graft (i.e . in a direction from the catheter tip to the catheter hub) Figures 14A and 14B show the stent-graft (106) and restraining member (102) in their final implantation position after the coupling meniber and catheter have been removed therefrom. In another variation, multiple restraining members may be used as shown in Figure 12C When the multiple coupling members (104) aic released simultaneously implant deployment time may be leduccd A method for deploying a balloon expandable sienl-gra l i mav h the same as that described above, w ith (he exception thai after ihe coupling member ( I 0 ) has been relucted from the eyelets ( I 1 ), the bal loon, w hich mav be positioned inside the stent-graft prior to delivery, is inflated to expand the stent-grafi ( 1 06) and then deflated for removal through the catheter ( 136). According to further variations, multidirectional coupling member release or multiple coupling members may be used. These configurations may facil itate more rapid deployment of the implant than when a single unidirectional coupling meniber is used. Figures 1 5A - 15D diagrammatically show multidirectional deployment of a restrained implant according to the principles of the invention where a coupling member arrangement is provided to release the implant from its middle portion, preferably its axial center, outward toward the implant ends. Although a particular coupling member configuration is not show n in these diagrammatic representations, one suitable coupling configuration is shown in Figure 16 where the leads (132) may be passed through the aperture (152) and coupled to the deployment knob (144) as shown in Figure 12A and described above. Referring to Figure 15A, the restrained stent-graft, which is positioned on the distal end portion of delivery catheter ( 136). is advanced through a vessel ( 1 54) for deployment in an aneurysm ( 158). The axial midpoint of the restraining member (102) preferably is positioned at the center of the aneurysmal sac. As the coupling member arrangement unlacing propagates from middle of the construct toward the proximal and distal ends of the restraining member ( 102) and the stent- graft ( 106), the stent-graft ( 106) progressively expands from its axial midportion toward its ends as shown in Figures 15B and 15C. This may be accomplished by pulling the leads ( 132) shown in Figure 16 simultaneously when the arrangement in that figure is used. The stent-graft size is selected so that when the restraining member is fully released and the stent-graft fully deployed as shown in Figure 1 5D, the proximal and distal portions of the stent-graft are positioned against the M pioximal and distal necks of the anein .iii lhedehveiv ,.' _.cι . > . aen be n 11 acted As is apparent fiom the drawings, tins vanation udvaiKagcoi.slv allow s fluid flow ihiough the aneuiysmal sac to remain substantial!} unobsiiucted dunng the release ofthe restraining member. For example, the stent-graft ends aie still constrained at the deployment time shown m Figure 15C where ihe aneurysm neck regions are shown minimally obstructed In addition, this simultaneous, multidirectional release ofthe restraining member advantageously reduces the tune in which fluid flow in the vessel may disturb the implant position as it is deployed as compared to a single directional release mechanism such as that shown in Figures 12-14. Referring to Figure 16, a multiple coupling membei configuiation is shown The illustrated arrangement includes two lacing configurations (150) and (152). Except for the placement ofthe lead (132) of thread-like coupling member (104) configuration ( 152) is the mirror image of configuration (150). Accordingly, description of only one of the configurations will be made for purposes of simplification. Referring to the lacing configuration (152). configuration (152) is the same as that shown in Figures In \-C with the exception that configuration (152) further includes two additional slip knots, designated generally with reference numeral (504), and tuck arrangement (506) The additional slip knots are not interwoven in the restraining member and provide a delay mechanism for release ofthe coupling member, as is apparent from the drawings, when the lead (132) is pulled in the direction ofthe arrow (134) Thus, inadvertent pulling ofthe lead (132) will not immediately begin to release the coupling member from the restraining member The tuck aπangement simply involves tucking the slack from lead (132) under stitches at various intervals as shown so that when pulled, the additional slip knots (504) mav be pulled out of the way for delivery. I \ i fiircalcd _Stejιj,__ι. ileriHCli ajl 1 Ins portion l ihe dcscnplioa i elated to I ig.iu es 1 - \ - > 2 I ) g. uei al ly i clatcs to an embodiment of the current i nvention w hei ei n U occ l usi v e flange is secured as a one-way valve on an outer surface ol one end portion ol a sel f- expanding, modular, bifurcated stent-graft. The seal member is intended to prevent leakage (low around the stent-graft and into an abnoi mal section of vascular wall which is intended to isolated from thai flow \\ bi le much of the description related to Figures 1 7A-32D is directed tow ai d the sieni-gi aft structure of the tubular member, the tubular member is being so descπbed for purposes of its role in defining this particular implantable medical dev ice embodiment of the present invention, which is assumed to include seal member attached to the outer surface of each tubular member variation described This portion of the description of the invention w ill also use certain nomenclature which is set forth as follows. The term ' " distal, "' as hereinafter used, is meant to refer to locations that are furthest away from the surgical access point. ''Proximal" is meant to refer to locations that are closer to the surgical access point A surgical access point, for purposes of this discussion, refers to the location at which the prosthesis first enters the bodv . in the i l lusti ativ e examples a small incision in the femoral artery Finally, the term "" prosthesis " refers to eithei a stent or a stent-graft. When the term stent is used, it refers to a structure that does not have a graft element whereas the term stent-graft refers to a structure that has both a stent element and a graft element. The tubular member of this embodiment, as shown in particular forms in the Figures 17A-32D, is a modular prosthesis adapted for placement at a bifurcation site with the body. For i llustrative purposes, this embodiment will be described with reference to the location in the human body w here the abdominal aorta bifurcates into the ipsalateral and contralateral iliac arteries. It should be understood, however, that this embodiment may be used at many other locations within the body. 895 I he sicnl-gu li components thai w il l be discussed below eonmnsc a flexible gul l membei .Klached lo a w πe stent membei usi ng a tape . mbei Picferably the stcnl-gnift components ai e designed foi compi essed deh v ei y and arc self-expanding, again as discussed in detail in reference to Figures 4- 1 3 above. The modular stent-graft of Figures 17A through 1 7b generally has two principal components; a main body (700) and a contralateral leg (730) each generally having a gi aft membei attached to a stent member according lo the description above ' Fhe main body (700) generally has a number of sections which have distinct overall constructions. A distal trunk section (708) has a single lumen structure beginning at a distal end (702) of the main body (700) and continuing until a bifurcation point (728) The bifurcation point (728 ) is the location within the prosthesis w here the single lumen of the distal tiunk section (708) bifurcates into internal two flow lumen. An intermediate section (710) begins at the bifurcation point (728) and continues to the receiving hole (704). In the intermediate section (710), the stent- graft has an internal graft structure which is bifurcated into two lumen surrounded by a generally tubular, single-lumen stent structure Finally, a proximal section (712) is a single lumen structure for both the stent member and the graft member and includes an ipsalateul leg (726) w hich terminates at an rpsalateral leg hole (706). The graft member of the intermediate section (710) bifurcates the single lumen distal trunk section (708) into the ipsalateral leg (726) and an internal female receiving lumen (703). The receiving lumen (703) terminates at a receiving hole (.704). The receiving hole (704) and receiving lumen (703) accommodate delivery and attachment of the contralateral leg component (730). Preferably, the graft material at the distal end (734) of the contralateral leg component (730) is scalloped as shown more clearly in Figure 23 discussed below. The receiving hole (704) is supported by a wire structure around a substantial portion of its periphery so that the receiving hole (704) is held open >5 M I S S I N G P A G E bi furcated gra li seelion resulting in less slcnl material lo compress i n l .it region As t he main body coniponeni (700) is compi essed for del iv ei y as el iscu .sed above , ihc compressed profile is signi ficantly smaller than would be a struclui e that had a section of bifurcated stent over the section of bifurcated graft. Even though bifurcated flow is supported, manufacturing is simplified because there is no bi furcated stent section. Winding a bi furcated stent section i n one piece, for example, is a more complex process. Likew ise, winding separate cylindrical stent structures and connecting them to form a bifurcated stent structure is complicated and ultimately may be less reliable. The intermediate section (710) allows the entire stent member that covers the main body coniponeni (700) to be made from a single undulating wire arranged in multiple helical turns. The result is a bifurcated stent-graft device which is simple to manufacture, easi ly- compressible and which expands reliably upon deployment. An alternative construction of the intermediate stent section (710) is shown in Figure 17D. The intermediate stent section (710') has a shape characterized by the indented regions (727). The shape could generally be described as a ' figure-8 ' . except that the area between the bifurcated graft member- remains unsupported at its centermost region. This construction is still a single lumen stent construction and therefore maintains much of the benefits of reduced profile and simplified manufacturability while providing the bifurcated graft member with increased support around a greater portion of its perimeter. Further, indented portions (727) have less of a tendency to spring outward upon application of external forces. As mentioned above, the main body component (700) and the contralateral leg component (730) are adapted for delivery in a compressed state to a bi furcation site within a body. For this purpose the main body coniponeni (700) is preferably equipped with a restraining member (722) constructed as described above. Likewise, the contralateral leg component (730) has an attached restraining member (732). These restraining members are typically sutured to the graft material at intervals down their length. I iguie I 8 shows an assembled biluiealed sknl-Luall ( / 10) allu deplov menl at a biluication site wilhm a biluuakd bo sst al flic l w ith an aneuiysm (7s8) Although not intended to be so limited to unv paiticulai location the inventive pioslhesis is shown al the location where the abdominal aoitic aiteiy (752) bifurcates into the left iliac artery (756) and the light iliac aiteiy (754) So that the various features ofthe inventive implant aie moie cleaily shown, the restraining member is not shown in Figuie 1 The assembled bifuicated stent-giaft (740) is compnsed ofthe main body component (700) and the contralateral leg component (730) Fhe distal end (734) ofthe contralateral leg component (730) has been inserted into the receiving leg hole (704) and the female receiving lumen (703) ofthe main body component (700) Foi best lesults in deploying any stent oi stent-graft of these t)pes it is essential that they have the appropriate stiuctural properties such as axial stiffness, flexibility and kink-resistance. With complicated structures, such as those required for treating a bifurcated site, it is increasingly difficult to obtain the desired structural properties because optimizing one may negatively effect the other For instance, optimizing the global axial stiffness of a stent or stent-graft will necessarily make the device significantly less flexible and consequently impair its resistance to kinking and lessen its ability to conform to the natural bends of curves the body's vasculature. Conversely a device that has high flexibility with little axial stiffness is difficult to properly deploy and does not aid in anchoring the device in the desired location With these constraints in mind, it has been discovered that having a bifurcated stent-graft which has segments consti acted with vaiying structural properties offers improved deployabihty, is less susceptible to kinking, and favorably tends to maintain its desired position after deployment while allowing sufficient flexibility to accommodate movement bv the body The exact structural propert ies desi red ma v depend on t he f 'cal io n w here ' . ■ ' . -.' prost h esi s : - t be deployed. For these reasons, it is preferable that the bifurcated stent or skill-graft be constructed with at least two segments having structural properties di fferent from one another. For example, in Figure 17A. a length of the distal section (708) and the intermediate section (710) may be constructed w ith a higher axial stiffness for improved deployment and positional stability w hile the proximal section (712) may be constructed to have higher flcxibilitv- to accommodate the geometry of the iliac artery. It may be further desirable to have a number of segments that have different structural properties. Accordingly , the main body component (700) and the contralateral leg component (730) of the assembled stent-graft (740) have segments constructed with structural properties different from adjacent segments. In one preferred variation shown in Figure 18, the main body component (700) has four different segments constructed with different structural properties. The distal segment (742) is constructed to have higher axial stiffness than the more flexible proximally adjacent segment (744). The proximal section (74S) is constructed to have a higher flexibility than that of its distal 1 y adjacent segment (746). Likewise the contralateral leg component (730 ) has an axially suffer distal segment (750) and a more flexible proximal segment (749). There are a number of ways to alter the structural properties of stent or stent-graft components. One way of selectively altering the structural properties of a stent-graft segment is to use a tape member for that segment that has different physical dimensions. Such a tape meniber is discussed above with reference to the tape meniber ( 128) of Figure 4. For example the tape member width, thickness or spacing may be increased, from the preferred dimensions discussed above, in a segment where it is desirable to have increased or decreased stiffness. For example, the use of wider tape wound with closer spacing w ill increase the stiffness in that area. Λ nolhei w as ol select i v el v al tei mg ihe sii uctuul pi opei t ies ol a stem 01 stent -gu l l segment i s shown i n I igu i es I 7 \ and I 8 I x tended si ml . , " 1 8 ) and (7 1 9) may be used lo mci case the ax ial sti ll ness o l a stent -gi al t segment Extended struts arc formed by extending an apex on one turn of the undulating wire until it contacts an apex on an adjacent turn. This contact between an extended strut and the apex of an adjacent stent turn piovides an added amount of axial stiffness. In a preferred embodiment, a layer of tape (not shown) is applied around the device in a helical pattern that covers each of the apexes of the extended struts. This additional layer of taping keeps the strut pairs together. Referring to Figure 17A, a first helical stent turn (720) and a second helical stent turn (721 ) have a generally undulating shape having apexes. An extended strut (718) of the stent turn (720) is formed having its apex near or in contact with the apex of the ste turn (721 ) directly below The extended strut (719) is similarly formed by extending an apex of the stent turn (721 ) directly down to contact the apex in the turn below. This pattern in continued, each time spacing the extended strut over one undulation. This results in a helical pattern of extended struts down the length of the device Of course, the extended struts may be arranged in patterns other than the helical configuration described A number of these patterns may be employed in any one segment or the extended strut pattern may be used in other segments to increase axial stiffness, Preferably the distally adjacent segment (746) on the main body component (700) and the axially stiff distal segment (750) on the contralateral leg component are constructed with extended struts as shown. Another important aspect of the present invention is achieving a secure position against the walls of the vessel lumen so that the deplo ed position is maintained and so that there is no leakage of luminal flow. Referring now to Figure 15, the distal end (702) is sized to properly fit the inside diameter o the target artery, in this case the abdominal aortic artery. Typically, the prosthesis is designed to have an unconstrained diameter slightly larger than the mside o the target vessel I he ipsalateul ΛU contulateial legs ol ' the s cr-' cJ mlukalcd stent- gull (740) aie ty picallv the s imc si/e at iheu distal eikk ,eg, . nlcss ol the size o| the distal cnύ (702) and undergo tapeied sections (724) and ( "" "S) that lapei to a diameter which corresponds approximately to the internal diametci of the iliac arteries. These tapered sections (724) and (738) are preferable to abrupt changes in diameter as they tend to produce supeiioi flow dynamics After deplo ment, the assembled bifurcated stent-graft (740) must establish sufficient contact with the healthy vessel lumen an each side ofthe aneurysm (758) so that the device does not migrate or dislodge hen subjected to the relatively high fluid pressures and flow rates encountered in such a major artery, especially when the body again becomes mobile after recovery Further, sufficient contact must be made so that there is no leakage at the distal end (702). the ipsalateral leg hole (706) or the proximal end (736) ofthe contralateral leg Anchoring or staying features that allow the stent or stent-graft exterior to anchor itself to the vessel lumen wall may be provided to help the device seal to the vessel wall and maintain its deployed position. For example, anchors (716) as seen in Figures 17A and 18 are provided on the main body component (700) and could also be provided on ihe contialateral leg component (730) Preferably, the top stent portion (717) is diiccted angularly outward This flared ste portion works to force the anchors (716) into the vessel wall as the top stent portion (717) expands under force into radial interference with the vessel wall upon deployment. A preferred construction for an anchor (716) is shown in Figure 20 A. This construction involves extending two wires from the upper stent turn (762) under an apex of an adjacent lower stent turn (764). The two ends of stent wires (760 and 761) are then bent out and away from the graft material (768) Extended struts (771) are formed adjacent to each anchor in the manner described above except the extended struts extend under the adjacent lo er stent turn (764) down to a third stent turn (765). This extended strut arrangement provides support for the anchors (716) and provides for low stresses in the wires (760 and 761 ) under ihe application of bending forces encountered as the prosthesis expands into the vessel wall, fhe extended skills (771 ) inimi/.e the loeali/..: Jcloιι:..;-.ion the sic ni -grail si rue tine in the area of the anchors by pro i mg i :> MC.OI s . poi ι. Another construction of ihe anchors (716 " ) are shown in Figure |V>. An anchor (716 " ) is formed in the same manner except ihe ends o the anchor remain connected in a ' U-shape' configuration as shown. An anchor (716 " ) may be formed at any location on the stent-graft. Most preferably, the anchors arc formed in an evenly spaced pattern around the top stent portion (717ι (Figure 17A). It should be apparent that the anchors as described above are t limited in use to the stent-graft combination shown in the figures but indeed could be used in any non-bifurcated or stent only construction that require similar functionality. Figure 20B further shows an implantable medical device with a tubular member, which is shown schematically and is preferably a stent-graft. with an anchor (716) and seal member (950) deployed into an endolumenal space. This is shown to further illustrate the effect an anchor may have on the tubular member wall when it is impinged into the artery wall. Much like a lever, the anchor pushes the tubular member wall out from the artery wall and creates a leak path. Sealing member (950) has flange (954) and first cuff end (952) in position to occlude such leak passageways. In addition to maintaining a good contact with the vessel lumen walls, the components ofthe stent-graft must make sufficient contact with each other such that the separate modules stay attached and do not leak at their engagement interface. The inventive stent-graft shown in Figure 21 illustrates several important features designed to effectuate a leak-free and positionally stable seal at the interface between the receiving lumen (703) ofthe main body component (700) and contralateral leg component (730). Figure 21 shows a partial cross-section ofthe assembled stent-graft. The contralateral leg component (730) has been inserted into the receiving lumen (703) ofthe main body component (700). This cross-sectional view shows clearly that the main body component (700) includes a main body graft member (780) and a main body stent member (782). The contralateral leg component (730) i ncludes a contralateral graft meniber ( 784) and a contralateral stent member ( 78(0 At the interface between the contralateral leg component (730) and the receiving lumen (703), the assembly provides for an extending sealing region (790). Preferably the extended sealing region (790) consists of a generally cylindrical interfering friction fit between the outside diameter of the contralateral leg component (730) and the inside diameter of the receiving lumen (703). That is the natural or resting outside diameter of Ihe self expanding contralateral leg component (730) would be larger than the natural inside diameter of the receiving lumen (703). Thus the forces created by the interference act to seal the two components and also serve to resist movement of the two components. The type of generally cylindrical extended sealing region just described has many advantages. First, it allows for the stent and graft structures in the extended sealing region (790) to be constructed of relatively simple generally cylindrical elements that are easily manufactured. Because the extended sealing region (790) extends over a large length it necessarily has a large surface area to effectuate sealing between the components. This larger sealing area typically provides that multiple turns o the stent structures w ill be engaged in an interfering and thus sealing relationship. In one preferred variation, the extended sealing region has a length in excess of one-half of the diameter of the receiving lumen (703), more preferably the length is greater that the diameter ofthe receiving lumen (703), and most preferably the length is more than 2 times the diameter of the receiving lumen (703). Because the manufacturing tolerances of the simplified shapes are easily controlled and because the engagement of the extended sealing region (790) is quite large, a highly reliable joint is formed between the modular components. Even so it may be desirable to create one or more localized zones of increased interference to increase the sealing capability and positional stability. Localized zones of inlei ference may be created in a numbei of way In o pi elcn ed vanalion. an annulai ring of dcci ca ed dianieiei is l or med w ithm the receiving lumen. Such a localized decreased diameter causes a gieatci interference with the outside diameter of the conlralaleral leg component in a localized area while the remainder of the engagement with the receiving lumen is subject to the general interference friction fit described above. One way of creating a localized decreased diameter is illustrated in Figure 23 which shows a partial cross-section of the extended sealing region (790). A zone of reduced diameter (799) is created by placing an anchoring ring (798) between the graft meniber (780) and the stent member (782) of the receiving lumen (703). The anchoring ring may be made from any polymeric or wire material, preferably a material that w ill not inhibit the receiving lumen from self- expanding to an open position. Most preferably the material is a suture material, typically ePTFE. Alternately, localized zones of decreased diameter may be created as shown in Figures 24 and 25 by folding a portion of the graft member (780) back up into the receiving lumen (703). In Figure 24. the zone of reduced diameter (806) is formed by creating a folded flap (808) of the graft material (780) around an anchoring ring (802). The flap is heat bonded in place roughly at a location (804) as shown. In Figure 25, the zone of reduced diameter (809) is formed of flap (808) and heat bonded roughly at a location (807) in a similar manner but without any anchoring ring. The localized interference using these methods tends to cover a larger area and the flap (808) provides a more flexible member to seal against the outside diameter of the contralateral leg component (730). One further aspect of ensuring a good seal between the stent-graft components involves the use of a scalloped stent-graft construction at the distal end of the contralateral leg component (810). To create this scalloped construction, the graft material between the apexes of the stent member is removed on the last turn of the stent. For example scallop (812) may be formed by removing (or folding under) the graf t material from betw een a fu st apex ( 1 4 ) and an adjacent ape (8 I ( • >). Fhe advantage of using a scalloped arrangement are i llustrated in Figures 27A through 28B. Figure 27A shows a cross-section of the fully expanded contralateral leg component (730) having an unscalloped construction. A first apex (822) and an adjacent apex (824) have continuous graft material (784) in the area between them. If the apex (822) and the adjacent apex (824) are forced together in the directions of the arrows (820), the graft material (784) forms a buckle or wrinkle (818) which is a potential leak path or is a potential site for thrombogenic material to build up as seen in Figure 27B. The scalloped construction shown in Figures 28A and 28B, on the other hand, have no graft material between the first apex (814) and the adjacent apex (8 16) and therefore when forced together do not form a graft material wrinkle. The wrinkle (818), mentioned above may also be formed when the stent- graft is not allowed to expand to its complete diameter. For instance it is quite common that the receiving lumen or vessel wall internal diameter is smaller than the fully expanded stent-graft outer diameter. In fact, in order to achieve complete stent-graft deployment with secure positioning and minimal leakage flow, oversizing a stent-graft to the vessel is often a desirable design choice. This being the case, it should be clear that the scalloped construction may alternately be used at any of the terminal openings of the main body component or the contralateral leg component. Preferably, the distal end (702) ofthe main body component (700) also has this scalloped construction as shown in Figures 17A and 17B. In the previous discussion we have referred generally to a stent-graft that includes a graft member. While the construction of such straight stent grafts are discussed at length above, the construction of a bifurcated graft member is illustrated in Figures 29, 30A and 30B. A bifurcated graft member suitable for construction of the main body component (700) discussed above is generally formed of two graft members: the ipsalateral tapered graft (840) and the contralateral tapered graft (842). The separate contralateral leg graft component ( 844 ) is a sti aighl or tapered section and may be formed accordi ng lo ihe pi m a ples d iscussed in the fu st section abov e. Fhe ipsalateral tapered graft (840) has three sections which aie separated by tapers. A top section (846), a middle section (848), and a bottom section (850). The body component graft (854) is formed by heat bonding the top section (846) of ipsalateral tapered graft (840) to the top section (847) of contralateral tapered graft (842). This heat bonding forms a common septum (856) which in a preferred variation is subsequently cut away to produce a smooth bifurcation (858). Cutting away the septum material prevents fluid flow disturbance or blockage that could result from deviation of the septum. Such deviation is caused by the fluid pressure and is aggravated if the stent-graft is radially compressed in a manner which causes the septum to become loose or no longer taut. In another embodiment, a graft section may be constructed in the manner illustrated in Figures 30A and 30B. According to this embodiment, the body component graft (867) is constructed from two pieces. A tubular graft section (860) is bent into a 'U-shape'. A top hole (864) is formed by notching the top of the "U-shape'. Upper graft section (862) is placed over the top hole (864) of tubular graft section (860). The two pieces are bonded together at the bonding interface (866). Preferably, the two graft pieces are heat bonded while supported by interior mandrels (not shown) to obtain the desired shape and smooth interior. However, upper graft section (862) may be attached to the tubular graft section (860) at the bond interface (866) in any manner that provides a sufficient leak-free seal. For example, the components may be sutured together or adhesive bonded. In use, the modular bifurcated stent-graft is typically delivered percutaneously through the vasculature of the body. Preferably the prosthesis is delivered by way of a restraining member as described in detail above. Figures 31 A though 3 I E diagrammatically illustrate deployment of a bifurcated stent-graft with a restraining member (902) using a percutaneous catheter assembly. Referring to Figure 31 A, a ultilumen catheter assembly (928) has been inserted to a selected site within a body lumen. The main body component ( 700) ol a hi l ui ealed .stcnt-gi aft is held in a compiessed siak . HUH a guidevv u c ( 926 ) and a guidcw u c lumen (929) by a l esti ammg membei rM2 ) and a c oupl i ng member (906) ' I he collapsed ma body component (700) is held axially i n place pnoi to deployment by a distal baincr (930) and a pioximal bamei (932) 1 he distal (930) and proximal (932) barriers are typically affixed to the guidewne lumen (929) The coupling meniber (906) extends through the eyelets (920) of the restraining member (902) forming chain knots and into the multilumen calhetei (928) Figure 31A shows advancement of the multilumen catheter (928) with the distally located main body component (700) and the restraining member (902) into implantation position, typically at the bifurcation of a maior vessel. During deployment it is critical that the surgeon align the main body component (700) so that the ipsalateral leg (726) will extend down one branch of the bifuicated vessel. and so the receiving hole (704) and the receiving lumen (703) will be lined up with the other branch of the bifurcated vessel so as to receive the contralateral leg component (730). One way of facilitating this alignment is to prov ide radiopaque markers so that the surgeon may readily determine the rotational position of the main body component (700) prior to deployment or release from the restraining meniber (902). In a preferred variation, a long marker (934) is located on the contralateral side of the compressed assembly and a shorter marker (936) is placed on the ipsalateral side. Preferably these markers are placed on the stent prior to compression but may alternatively be part of the restraining member. Having one marker of a different length allows the surgeon to identify the orientation of both the ipsalateral leg and the receiving lumen relative to the bifurcated vessel. Once the assembly is properly aligned and positioned for implantation, the coupling member (906) is pulled and the restraining member (902) begins to release the implant, typically at the distal end first. In the preferred embodiment, the restraining member (902) is located down the side as sho n because it is less likely to interfere with deployment of the receiving lumen (703 ) 1 igui e 3 I B show s Ihe mam bodv component ( 700 ) ι Mii ing as ihe coupling membei (906) is i cti acled ihi ough ihe ey elets ( 2θ j o l l. _ l estu i ng membei (902) and into the catheter assembly (928) In ihe pi elen ed embodiment the icstraining membei (902) has been fixedly attached to the a body component (700) with a number of sutures along the length of the mam body component to prevent any relative longitudinal movement betw een the implanted piosthesis and the restraining membei (902) The restummg member may optionally employ a retracting oi pull-down mechanism as descnbed at length above Figure 31 C shows the main body component (700) and the restiaining member (902) in final implantation position at the vessel bifurcation after the guide ire (926) and the catheter assembly (928) have been retracted Figure 3 I D shows the contralatcial leg component (730) being delivered to the contralateral receiving hole using a restraining meniber (942) The procedure for positioning and releasing the contralateral leg component (730) is the same as that described above for implantation of a generally cylindrical stent-graft except that certain radiopaque markers may be employed to ensure us proper position relative to the bifurcation point (728) of main body coniponeni ( 700) Radiopaque markers may be located, for example, to indicate the position of the receiving hole (704), the distal end (734) of the contralateral leg component (730), and the bifurcation point (728) of the main body component (700) These markers serve to indicate the position ofthe contralateral leg component as it enters the receiving hole (704) and its ultimate position relativ e to the receiving lumen (703) which begins at bifurcation point (728) In a preferred v ariation illustrated in Figure 22, the radiopaque wires (794) may be heat bonded or imbedded into the graft material (780) around the periphery of the receiv mg lumen Such radioopaque wires could be used in other places such as the contralateral leg component lumen, the ipsalateral leg lumen or the lumen at the distal end of the main body component (700) Figui e 3 1 E show s the assembled bi l ut eaic,' sic - M I t i n Us final i mplantation slate w ilh the contulaiei al leg <_omp> '. ico i nk mil engaged with the l eceiving lumen ol the mai n bodv t r no, ml ( 700 ) Figures 32A through 32D diagtammutically show the same slcnl or stcnt- graft components being deployed except that the lestiammg membei (902) is i eleased from the center out towards as the coupling member (906) is retracted. This may provide moi e accurate placement l elaln e to :.ιe bι :uι cation point of the vessel instead of relative to the distal end as w ith end i iea c Seal member (950) is further shown throughout Figures 1 7A-32D where its inclusion is appropriate to illustrate how the seal meniber combines with these stent-graft tubular member variations to result in the implantable medical device of the present invention For example, Figur es 1 9 and 20A show seal me nlv ( 950) secured to the outer surface of the stent-graft meniber adjacent to apex anchors ( 16), which may be proximally positioned adjacent to such anchors located on the distal main body end of a bifurcated stent graft. Seal member (950) is shown as an occlusive cuff which preferably circumferentially envelops both the stent meniber and the graft meniber of the stent-graft tubular membei Seal e b er (950 ) has a first cuff end (952) secured to the outer surface of the stent-gi ali an:: also has a second cuff end (954) that is unsecured and extends distally toward apex anchors (716), forming a flange over the struts of the stent member. In this orientation relative to the longitudinal axis of the stent-graft, seal member (950) forms a one-way valve to occlude flow over the stent-graft and in the direction from the stent-graft end and toward the central portion of the stent-graft. for instance tow ard an aneurysm adjacent the bifurcation. One preferred construction for seal membei (950) in the variations shown in Figures 19 and 20A may be similar to the prefeπed construction for the tape member used in constructing the stent-graft tubular member as is provided in reference to Figure 6 above I n gcneu l . a th i n w al led eP I I K tape i s used l oi seal mem bei k' 0 ) si m i la i ly as t hat l oi tape membe i ( 1 2S ). show n ion s l i gui es Fhe tape used for seal member (950 ) is adhered to the outei sin face ol the stent- graft. including over tape meniber ( 128), described previously for bonding the stent and graft members. Seal member (950) has an inner surface constructed of a simi lar material for either the outer surface of the tape meniber ( 1 28) or the outer surface of the graft-member ( 1 24). depending upon which surface the seal member is desirably adhered. In one preferred mode, the construction of seal member (950) has a width along the longitudinal axis of the stent-graft of about 2cm. wherein first end portion (952) comprises about 1 cm and second end portion (954) comprises about 1 cm. First cuff end (952) is bonded to the stent-graft outer surface and second cuff end (954) is not. in order to form the unadhcred flange to function as a oneway valve against peri-stent-graft flow. Seal member (950) may be selectively adhered along its length in this manner by providing a variable inner surface to the seal member such that, upon heating, only the surface in the region of first cuff end (952) bonds to the outer surface of the stent-graft. For example, the inner surface of seal membei (950) may have an FEP liner in the region of first cuff end (952) but not in the region of second cuff end (954) In this case, upon contacting an outer surface of the stent-graft that has a uniform FEP outer surface, only first cuff end (952) may be heat secured thereon. Alternatively, seal member (950) may have a uniform inner surface, such as constructed of FEP, and a variable outer surface, such as with a selective portion of FEP. may be provided either on the tape member ( 128) or on the graft member ( 124) in the region where the heat bonding of seal member (950) is desired. Still further, seal member (950) may have a uniform surface and may be positioned over tape member ( 128) and graft member ( 124) so that variability between the outer surfaces of tape member (128) and graft member ( 124) causes a selective bonding with the first cuff end (952) over one of those surfaces. l- ' urthci lo the consn uclion of seal membei ( 950). ihe parl iculai w al l t h ickness ol the tape w hich may be used I i this coniponeni should desu ablv be as thi n as possible to functional ly provide the flangc-one-w ay-valv e function loi thai member. Phis is because, since seal member (950) is over the outer surface of the other stent and graft components of the stent-graft, seal member (950) is believed to be the profile-limiting feature of the overall assembly. Therefore, in a particular design, seal member (950) may desirably be a thinner wall than for the tape member used lo construct the stent-graft described in reference to Figure 6. Further referring to the particular constructions and related methods just described for adhering seal member (950) to the outer surface of the underlying stent-graft, it should be apparent to one of ordinary skill in the art that the desired construction and heat securing technique for seal member (950) is premised upon the theory that, where one polymer meets a like polymer (such as FEP meeting • FEP), heating under proper conditions will allow for a selected heat bond. The present invention, however, should not be construed as limited to these particularly described conditions, but instead should be considered to more broadly encompass any suitable means for securing a seal member to the outer surface of a given tubular member, as would be apparent to one of ordinary skill , and as is provided previously with reference to Figure 1 . Further to the detail shown in Figures 19 and 20A, a plurality of circumferential strut spaces (956) are also shown between the struts of the stent member. It is believed that these spaces may provide a path for leakage flow around the outer surface of the graft member and along the outside of the stent- graft. Second cuff end (954), however, captures such leakage flow beneath its flange, which can not propagate along the outer surface of the stent-graft because first cuff end (952) is secured to the outer surface of that stent-graft. In other words, flow over the stent-graft and into an aneurysm is occluded. Furthermore, when apex strut (716) is anchored into the wall of abdominal aortic artery (752), as shown in Figure 20B, it has been observed that the portion of main body (700) at and adjacent to the apex strut ( 7 1 6) can be forced a ay h orn ihe ai tei y w al l pai iiculai Iv i n case o l calci fied tissue I h i s uctio causes a se paul ion ( u 56) bclw een ihe oulei sui hk c ol mam body t, 7 ( ) 0 ) and ilk ai tei y w a l l w hich sepaution is believed to ci eatc a leakage flow path 1 he flange of seal membei (950) captuies that flow and occludes it liom propagating uiio the aneuiysm (758). Figure 31 E further shows seal member (950) on a stent-graft m combination with additional seal membeis (960,970). which are located adjacent the ends of ipsalateral and contralateral legs (726,730). respectively, of the modular stent graft assembly. It is believed that distal leakage flow around the legs of bifurcated stent- giafts may often be a major contributing component to overall leakage flow into the aneurysms which are intended to be protected by such stent-grafts agarnsl flow. Seal members (960,970) are beneficially intended to occlude such distal leakage. It should be further appreciated that the present invention contemplates seal members (950), (960), and (970), as well as combinations thereof, secured to the outer surfaces of the tubular member designs shown in Figures 17 Λ. 18. 3 1 C- D. or 32A-D. Furthermore, any sufficient seal member, such as those provided in the above described embodiments and variations thereof, may be used w ith these stent-graft variations and fall within the scope of the invention For example, either the flange occlusion cuff variations described, or even an expandable hydrophilic member, may be used with the bifurcated stent-graft shown in these Figures, such as Figure 3 I E, and fall within the scope of the present inv ention In a further variation, a seal member such as seal member (950) shown variously in the figures, may be secured over the distal end of contralateral leg component (810) in a modular stent-graft assembly, such as shown at (810) in Figure 27B. The potential leak path through wrinkle (818) of the graft member (Figure 27B) is formed by oversizing the leg component for coaxial engagement with the other modular graft component Seal meniber (950) blocks the leak path ihiough wiinkle (8 I S). which would olherw ise allow How o ol the ι . nen oi ' the sienl-g.ull into the .suiiounding eiuloluiuen.il sp.uc I he w imk le (818) is caused by a similai condition lo thai escnbed eai liei ith leference to oversizing graft members relative to engage arterial walls, such as is shown in and described in reference to Figure 3. In fact, it is quite common that the receiving lumen or vessel wall internal diameter is smaller than the fully expanded stent-graft outer diameter. In order to achie e complete stent-graft deployment with secure positioning and minimal leakage flow, oversizing a stent- graft to the vessel is often even a desirable design choice. Therefore, all cases of stent-graft oversizing and wrinkling may benefit from the seal meniber design of the current invention. While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations ofthe illustrative embodiments, as well as other embodiments ofthe invention will be apparent to persons skilled in the ait upon reference to the description It is therefore intended that the appended claims encompass any such modifications oi embodiments

Claims: ( I \IM_S W 'i is i lainud is 1 \n implantable medical dev ice loi dclivuv to an endolumenal body space that is defined by Λ endolumenal wall and loi piov idmg an artificial conduit foi flow Ihiough the endolumenal body space, comprising a tubulai membei with a tubulai wall having a length along a longitudinal axis, two opposite end portions, a central portion between said two opposite end portions, and an outei suiface with a fust diametci and shape dimensioned to substantially engage at least a portion ofthe endolumenal wall, said tubular wall further defining a lumen that extends along said length and that provides a conduit foi flow thiough ihe endolumenal body space and a seal membei secuied to said outei suiface which is adapted to occlude leakage flow exleinallv around the tubulai wall between the outer suiface and the endolumenal wall when the tubular member is deplo ed within the endolumenal body space 2 The implantable medical device of claim 1 wheie said seal member comprises an occlusive cuff having a fust cuff end secured to said outer suiface and also having a second cuff end with a portion that is unsecuied to form a flange over said outer surface as a one-way valve adapted to occlude flow in a direction from the second cuff end toward the first cuff end 3 The implantable medical device of claim 2. wherein said seal member is secuied to one of said end portions with said first and second cuff ends oriented relative to each other along said longitudinal axis such that leakage flow in the duection from the one end portion to aid the ccntial portion is occluded 4 The implantable medical device of claim 3 wherein said tubular member further compnses .in uni hoi has mg a li i st am hoi uul p i l ion s uii ul " n luhulai w al l and a sec ond aiu hoi uul port ion L X kiidi ng udial l v o a w . oin outei stii lace, said seal membei being secuied lo said oulei ui Luc adjacent to said anchoi 5 I hc implantable medical device of claim 3 w hei ei n the endolumenal wall has an abnoi mal portion with an endolumenal diameter adjacent thci cto, and wherein said central portion has a central portion length adapted to span the abnormal portion of the endolumenal wall; and said tubular membei has a iadially collapsed condition such that said outer sui face has a second diametei which is dimensioned to be smaller than the endolumenal diameter, said tubular member being adjustable to a radially expanded condition such that said outer surface has said first diameter and shape, wherein each end portion substantially engages the endolumenal wall adjacent to the abnormal portion and said seal membei is adapted to occlude flow aiound the one end portion and into the abnormal portion o' endolumenal wall when said tubulai member is adjusted to said radially expanded condition 6 The implantable medical device of claim 5, further comprising two said seal members, each being secured to an opposite end portion and having an opposite orientation along the longitudinal axis relative to the other, such that flow in directions from each end portion and toward the cential portion is occluded 7 The implantable medical device of claim 5, w herein said tubular member is in said radially collapsed condition when radially confined, and is in said radially expanded condition w hen iadially unconfined :> 8 1 he i in plan table medical dev ice o l c laim 7. I in ti i ^ on - a im a sheet ol malct ial which is i apped aiound said lubu hii ilk -mei and said ctil member and which has portions that are coupled together w ith coiφhng member to radially confine said tubular meniber in said radial ly collapsed condition 9 The implantable medical device of claim 5, said one end portion comprising exactly one tubular wall with a single lumen, said othei end portion comprising more than one leg portion, each leg portion compr ising a separate tubular wall that defines a separate lumen which is in communication w ith the single lumen 10. The implantable medical device of claim 9, further comprising a second said seal member secured to one leg portion o f the other end portion in an orientation relative to the longitudinal axis of the tubular member such that flow in directions from each end portion and toward the cential portion is occluded 1 1. The implantable medical device of claim 1 , wherein said tubular member further comprises a stent-graft having: a flexible, tubular graft member; and a stent member which is coupled to said tubular graft member and which has at least one circumferentially reinforcing member that is constructed of relati vely rigid material compared to said tubular graft member 12 I he mφlaniable meilual dev ice ol claim I I w hci em said stent mem Ik i i , .t.αι i ed to an on lc. MI '1.1 ol I nail member, and wheiein said seal membei comprises dn occlusive cull ha ing a lust cull end over said stent and graft membeis and secuied to said outer surface ol said giaft membei, and also having a second cuff end with a portion thai is unsecuied to foim a flange ovei said stem and giaft membeis as a one-way val adapted lo occlude flow in a diiection from the second flange end toward the fii i flange end 13 The implantable medical device of claim 12. further comprising an anchor having a first anchor end portion secured to said tub.ilai wall, and also having a second anchor end portion extending iadially outwa-dly liom said outer surface, said seal member being secured to said outer surface of said tubulai member adjacent to said anchor. 14. The implantable medical device of claim 11. wherein said seal member is seemed to one of said end pυrt.ons such t at leakage flow in the direction from the one end portion toward the cential poiuon is occluded 15. The implantable medical device of claim 14, wherein said one end portion comprises exactly one tubular wall with a single lumen, and said other end portion comprises more than one leg portion each leg portion comprising a separate tubular wall that defines a separate lumen which is in communication with the single lumen 16 I he implantable medical dev ILL ol ι hum Is Itnihei coinpnsing a second said seal membei sαπiul to < HK lc" JIOI lion ol tin othei portion m an onenlalion iclalive lo the longitudinal axis ol the lubului membei such thai flow in diiections fiom each e d portion ,m lowanl ihe cential portion is occluded. 17 An implantable medical device compnsing an implantable tubular membei means loi engaging an endolumenal wall that defines an endolumenal body space and for providing an artificial conduit for flow through the endolumenal body space, said implantable tubular member means having a tubular wall with an outei surface: and a sealing means secuied to said outei suiface loi occluding leakage flow externally around the tubulai membei means between the outei surface and the endolumenal wall when the tubular membei means is deployed within the endolumenal body space.

Inventors: LAU LILIP, THORNTON TROY, LAU, LILIP, THORNTON, TROY
Applicants: PROGRAFT MEDICAL INC, PROGRAFT MEDICAL, INC.
Application year: 1997
Main classification: A61F2
IPC codes: A61F2