Source: http://www.docstoc.com/docs/50775954/Exterior-Supported-Self-expanding-Stent-graft---Patent-6331188
Timestamp: 2015-04-01 09:38:46
Document Index: 39985324

Matched Legal Cases: ['application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 08', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'art.\n5']

Exterior Supported Self-expanding Stent-graft - Patent 6331188
50775954
This invention is a medical device and a method of using it. The device is a foldable stent-graft which may be percutaneously delivered with (or on) an endovascular catheter or via surgical techniques or using other suitable techniques and thenexpanded. The stent-graft uses a kink-resistant stent structure and an interior graft which is attached to the stent in such a way that the graft does not kink and yet the stent is able to conform to curves in the blood vessel lumen.The expandable stent structure preferably has a helically deployed torsional member with an undulating shape which is wound to form the generally cylindrical shape deployed as the stent. The helical winding desirably is aligned to allow theundulations in adjacent turns of the helix to be in phase. The adjacent undulating shapes may be held in that phased relationship using a flexible linkage, typically made of a polymeric material. The stent may also be of a ring configuration.The stent may be flared to promote smooth blood flow and to assure that the stent will remain in its chosen position.The graft component cooperating with the stent is tubular and mounted on the interior of the stent. Although it may be made of any of a variety of materials, it preferably is an expanded polyfluorocarbon. The graft component may be attached tothe stent in a variety of ways but desirably is bound to the flexible linkage which holds the stent windings in phase (or to the stent structure itself) at a number of sliding attachment points. This manner of attachment allows the stent to slidelocally with respect to the graft structure or, in the case of the helically wound stent structure, allows the adjacent undulating shapes in adjacent helical turns to slide longitudinally with respect to each other as the stent is bent and still supportthe shape of the graft.The stent-graft may be used to reinforce vascular irregularities, to provide a smooth nonthrombogenic interior vascular surface for diseased areas in b
United States Patent: 6331188
The present invention relates to a stent-graft where the stent is formed
from a self-expanding material and is coaxially and slidably coupled to
the graft component which contains collagen. At least one flexible linkage
is provided for coupling the stent and graft together in the slidable
Lau; Lilip (Sunnyvale, CA), Maroney; Charles (Portola Valley, CA)
08/871,427
740030Oct., 1996
299190Aug., 1994
623/1.13  ; 606/198; 623/1.22; 623/1.34
623/1,11,12,1.13,1.15,1.16,1.22,1.34,23.7,23.64 606/191,194,195,198
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196 17 823 A1
0 418 677 A1
0 423 916 B1
0 464 755 A1
0 556 850
0 565 351
0 667 131 A2
0 705 577 A1
0 716 834 A1
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1 567 122
06-007454
06-181993
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07-024688
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Neuwirth; A Percutaneous Therapy; Minimally Invasive Technologies..
This application is a continuation of application Ser. No. 08/740,030,
filed Oct. 23, 1996, now abandoned, which is a file wrapper continuation
of application Ser. No. 08/299,190, filed Aug. 31, 1994, now abandoned.
a support component having multiple turns of an undulating member, said undulating member being formed from a single continuous wire, each turn of said undulating member having multiple undulations which define multiple apexes, wherein
undulations in one turn are generally in-phase with undulations in an adjacent turn;  and
a tubular, graft component substantially coaxial with said support component, said tubular graft component containing collagen and being slidably attached to said support component to allow said undulations to move longitudinally relative to said
graft component.
2.  The device of claim 1 wherein said support is a helical member configured to form said support component and which contains said multiple turns of said support.
3.  The device of claim 2 further comprising at least one flexible link, said flexible link coupling adjacent helical turns of said support component to maintain said undulations generally in-phase.
4.  The device of claim 3, wherein said flexible link is secured to said graft component at least in-part.
5.  The device of claim 1 further comprising at least one loop passing around at least a portion of one of said undulations to attach said support component to said graft component.
6.  The device of claim 1 wherein said support component includes at least one common arm between adjacent undulations.
7.  The device of claim 1 wherein the support comprises wire and the undulations have a sinusoidal shape.
8.  The device of claim 1 wherein the support comprises wire and the undulations have a U-shape.
9.  The device of claim 1 wherein the support comprises wire and the undulations have a V-shape.
10.  The device of claim 1 wherein the support comprises wire and the undulations have an ovaloid shape.
11.  The device of claim 1 wherein the support comprises a stainless steel material.
12.  The device of claim 1 wherein the support comprises a cobalt chromium alloy.
13.  The device of claim 1 wherein the support comprises a platinum/tungsten alloy.
14.  The device of claim 1 wherein the support comprises a titanium alloy.
15.  The device of claim 1 wherein the support comprises a nickel-titanium alloy.
16.  The device of claim 1 wherein the support is produced from sheet material or tubing.
17.  The device of claim 1 further comprising radiopaque markers within said collagen containing graft member.
18.  The device of claim 1 wherein at least one end of the support component is flared.
19.  The device of claim 3 wherein said at least one flexible link comprises a polyfluorocarbon.
20.  The device of claim 5 wherein the at least one loop comprises a polyfluorocarbon.
21.  The device of claim 1 wherein said support component is slidably secured to said graft component such that relative movement therebetween is limited.
22.  The device of claim 2 further including a flexible link interwoven through undulations in adjacent helical turns.
23.  A device comprising:
a tubular, graft component substantially coaxial with said support component, said tubular graft component containing collagen and being slidably attached to said support component which allows said undulations to move longitudinally relative to
said graft component;  and
24.  A device comprising:
a support component having multiple turns of an undulating member, said undulating member being formed from a single continuous wire, each turn of said undulating member having multiple undulations which define multiple apexes, wherein apexes in
one turn are longitudinally movable with respect to apexes in an adjacent turn, and wherein undulations in said one turn are generally in-phase with undulations in said adjacent turn;  and
a tubular, graft component substantially coaxial with said support component, said tubular graft component containing collagen and being slidably attached to said support component to allow said apexes to move longitudinally relative to said
graft component.  Description
This invention is a medical device and a method of using it.  The device is a foldable stent-graft which may be percutaneously delivered with (or on) an endovascular catheter or via surgical techniques or using other suitable techniques and then
expanded.  The stent-graft uses a kink-resistant stent structure and an interior graft which is attached to the stent in such a way that the graft does not kink and yet the stent is able to conform to curves in the blood vessel lumen.
The expandable stent structure preferably has a helically deployed torsional member with an undulating shape which is wound to form the generally cylindrical shape deployed as the stent.  The helical winding desirably is aligned to allow the
undulations in adjacent turns of the helix to be in phase.  The adjacent undulating shapes may be held in that phased relationship using a flexible linkage, typically made of a polymeric material.  The stent may also be of a ring configuration.
The graft component cooperating with the stent is tubular and mounted on the interior of the stent.  Although it may be made of any of a variety of materials, it preferably is an expanded polyfluorocarbon.  The graft component may be attached to
the stent in a variety of ways but desirably is bound to the flexible linkage which holds the stent windings in phase (or to the stent structure itself) at a number of sliding attachment points.  This manner of attachment allows the stent to slide
locally with respect to the graft structure or, in the case of the helically wound stent structure, allows the adjacent undulating shapes in adjacent helical turns to slide longitudinally with respect to each other as the stent is bent and still support
the shape of the graft.
The stent-graft may be used to reinforce vascular irregularities, to provide a smooth nonthrombogenic interior vascular surface for diseased areas in blood vessels, or to increase blood flow past a diseased area of a vessel by mechanically
improving the interior surface of the vessel.  The inventive stent-graft is especially suitable for use within smaller vessels between 2 mm and 6 mm in diameter but is equally suitable for significantly larger vessels.  The inventive stent-graft may be
self-expandable; it is kink-resistant, easily bent along its longitudinal axis, and does not change its length during that expansion.
Treatment-or isolation of vascular aneurysms or of vessel walls which have been thinned or thickened by disease has traditionally been done via surgical bypassing with vascular grafts.  Shortcomings of this procedure include the morbidity and
blood to a smooth, nonthrombogenic surface capable of supporting endothelium growth.
The inventive device may be delivered in a reduced diameter and expanded to maintain the patency of any conduit or lumen in the body.  An area in which the inventive stent-graft is particularly beneficial is in the scaffolding of atherosclerotic
lesions in the cardiovascular system to establish vessel patency, prevention of thrombosis, and the further prevention of restenosis after angioplasty.  In contrast to many of the stents discussed below having metallic struts intruding into the blood
flow in the vessel lumen which generate turbulence and create blood stasis points initiating thrombus formation, the smooth, continuous surface provided by the preferred tubular inner conduit of our invention provides a hemodynamically superior surface
for blood flow.
Mechanically, the linked helical stent structure used in the stent-graft provides a good combination of radial strength and flexibility.  The structure is also radially resilient.  It can be completely crushed or flattened and yet spring open
again once the obstructive loading is removed.  This ability is important for use in exposed portions of the body around the peripheral vasculature or around joints.  The stent-graft can sustain a crushing traumatic blow or compression from the bending
of a joint and still return to the open configuration once the load is removed.
With regard to delivery, the self-expansion mechanism eliminates the need for a balloon catheter and the associated balloon rupture problems often associated with that delivery procedure.  In addition, the absence of the bulk of the balloon
allows a smaller delivery profile to be achieved.  Unlike some other self-expanding stent designs, this stent-graft maintains a constant length throughout the expansion process.  Thus, the stent-graft does not have some of the positioning problems
associated with other many self-expanding stents.  In treating longer lesions, our self-expanding design eliminates the need for special long balloons or repositioning of the balloon between inflations in order to expand the entire length of the stent.
The impermeability of the preferred stent-graft makes it suitable for shunting and thereby hydraulically isolating aneurysms.  The expansile properties derived from the stent structure provide a secure anchor to the vessel wall.
Quan-Gett, U.S.  Pat.  No. 5,151,105, discloses an implantable, collapsible tubular sleeve apparently of an outer band and an inner spring used to maintain the sleeve in a deployed condition.
angioplasty balloon for its expansion.  Hillstead, U.S.  Pat.  No. 4,856,516, suggests a stent for reinforcing vessel walls made from a single elongated wire.  The stent produced is cylindrical and is made up of a series of rings which are, in turn,
linked together by half-hitch junctions produced from the single elongated wire.
tubular shape interconnected with a filament.  The bends of the helix each have small loops or &quot;eyes&quot; at their apexes which are interconnected with a filament.  Because of the teaching to connect the eyes of the apexes, the stent appears to be a design
patent further suggests the use of a pyrolytic carbon layer on the surface of the stent to present a porous surface of improved antithrombogenic properties.
There are a variety of disclosures in which super-elastic alloys such as nitinol are used in stents.  See, U.S.  Pat.  No. 4,503,569, to Dotter; U.S.  Pat.  No. 4,512,338, to Balko et al.; U.S.  Pat.  No. 4,990,155, to Wilkoff; U.S.  Pat.  No.
5,037,427, to Harada, et al.; U.S.  Pat.  No. 5,147,370, to MacNamara et al.; U.S.  Pat.  No. 5,211,658, to Clouse; and U.S.  Pat.  No. 5,221,261, to Termin et al. None of these references suggest a device having discrete, individual, energy-storing
torsional members as are required by this invention.
The Palmaz &#39;762 and &#39;337 patents appear to suggest the use of thin-walled, biologically inert materials on the outer periphery of the earlier-described stents.
Schatz, U.S.  Pat.  No. 5,195,984, shows an expandable intraluminal stent and graft related in concept to the Palmaz patents discussed above.  Schatz discusses, in-addition, the use of flexibly-connecting vascular grafts which contain several of
Cragg (European Pat.  Application 0,556,850) discloses an intraluminal stent made up of a continuous helix of zig-zag wire and having loops at each apex of the zig-zags.  Those loops on the adjacent apexes are individually tied together to form
Those biocompatible materials may be inside the stent (col.  3, lines 52+) or outside the stent (col.  4, lines 6+).  There is no suggestion that the zig-zag wire helix be re-aligned to be &quot;in phase&quot; rather than tied in an apex-to-apex alignment.  The
alignment of the wire and the way in which it is tied mandates that it expand in length as it is expanded from its compressed form.
into the lumen of the graft and massaging the slurry into the pore structure of the substrate-to assure intimate admixture in the interior.  Repeated applications and massaging and drying is said further to reduce the porosity of the graft.
use of a ledge at the longitudinal seam for catching the opposite side of the seam on the expanded graft.
The use of expanded polyfluorocarbons in vascular devices is shown in British patent Nos.  1,506,432, and 1,567,122, which patents show in particular blood vessel linings of the material.
The incorporated expandable stent structure utilizes torsional regions which allow it to be folded to a very small diameter prior to deployment.  Preferably, the torsional members have an undulating shape which may be helically wound to form the
stent&#39;s cylindrical shape.  The undulating shape may be aligned to allow the undulations in adjacent turns of the helix to be in phase.  Adjacent undulating shapes may be held in the phased relationship using a flexible linkage, often made of a polymeric
material.  In the helically wound variation of the invention, the undulating torsional members do not have any means at (or near) the apex of the undulating shapes which would tend to constrict the movement of the flexible linkage during compression or
bending of the stent.  The stent is preferably made of a highly flexible, superelastic alloy such as nitinol, but may be of any suitable elastic material such as various of the medically accepted stainless steels.  The stent structure may also be of a
series of rings incorporating the torsional members which rings may be axially linked.
The graft component used to complement the stent is typically tubular, placed within the stent, and may be made of a polymeric material which may be attached variously to the filament used to maintain the shape of the stent structure, when such
filament is used, or to the stent structure itself.  Preferably, the graft component is a biocompatible, expanded polyfluoroethylene polymer.  The attachment between the graft component and the stent, e.g., by bonding the graft component to the flexible
linkage or by using eyelets or other discrete or continuous linking sites, is carefully crafted to allow the stent torsional members to slide longitudinally with respect to each other and to the graft component and so maintain the interior shape of
graft.  This is to say that the graft component is supported at a variety of sites located along its outer surface.  Bending the stent-graft combination distributes the flexing movement of the graft over a long region because of the distributed support
of the stent.  The tendency of the graft component to kink in a single site is minimized and the resultant flexing is observed to take place in a collection of smaller non-kinking bends located among the tie points to the stent or the stent&#39;s filament.
As was noted above, this invention is an expandable stent-graft and a method of using it.  The stent-graft is a combination of several components: first, a thin-walled tube forming the graft component which graft component is generally coaxial to
and within the stent and, second, the expandable stent structure.  The graft material may optionally contain a fibrous reinforcement material.  The expandable stent structure is a cylindrical body produced either of a helically placed (wound or otherwise
preformed) torsion member having an undulating or serpentine shape or a series of axially situated rings comprising those torsion members.  When the undulating torsion member is formed into the cylinder, the undulations may be aligned so that they are
&quot;in phase&quot; with each other.  The helically wound undulations are desirably linked, typically with a flexible linkage of a suitable polymeric or metallic material, to maintain the phased relationship of the undulations during compression and deployment
and during bending of the stent.  These stent configurations are exceptionally kink-resistant and flexible, particularly when flexed along the longitudinal axis of the stent.
Central to the invention is the distributed attachment of the stent component to the graft component via, e.g., the bonding of the graft to the filament which may used to maintain the stent in its tubular shape or via bonding to other loops,
eyelets, or fasteners associated with or adhering to the stent component.
The stent-graft may be delivered percutaneously, typically through the vasculature, after having been folded to a reduced diameter.  Once reaching the intended delivery site, it is expanded to form a lining on the vessel wall.
Our stent is constructed of a reasonably high strength material, i.e., one which is resistant to plastic deformation when stressed.  The structure is typically from one of three sources:
These stent structures are typically oriented coaxially with the tubular graft component.  The stent structures are, at least, placed on the outer surface of the graft although, in certain configurations, an additional graft structure may be
placed on the outer surface of the stent.  When the outer graft structure is utilized, the stent structure should have the strength and flexibility to tack the graft tubing firmly and conformally against the vessel wall.  In order to minimize the wall
thickness of the stent-graft, the stent material should have a high strength-to-volume ratio.  Use of designs as depicted herein provides stents which may be shorter in length than those often used in the prior art.  Additionally, the designs do not
suffer from a tendency to twist (or helically unwind) or to shorten as the stent-graft is deployed.  As will be discussed below, materials suitable in these stents and meeting these criteria include various metals and some polymers.
A percutaneously delivered 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 (for neurological applications) from 2.0 mm in diameter to 30 mm in diameter (for placement in the aorta).  A range of about 2.0 mm to 6.5 mm (perhaps to 10.0 mm) is believed to be desirable.
Typically, 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 of the 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 usually sufficient.  For the larger stents, the appropriate thickness for
the stent flat stock may be somewhat thicker, e.g., 0.005 to 0.020 inches.
FIG. 1A is a plan view of an isolated section of the stent which may be used in the stent-graft of the invention.  The Figure is intended both to identify a variation of the invention and to provide conventions for naming the components of the
torsion member (100).  FIG. 1A shows, in plan view, an undulating torsion member (100) formed from a wire stock into a U-shape.  A torsion pair (102) is made up of an end member (104) and two adjacent torsion lengths (106).  Typically, then, each torsion
length (106) will be a component to each of its adjacent torsion pairs (102).  The U-shaped torsion pair (102) may be characterized by the fact that the adjacent torsion lengths are generally parallel to each other prior to formation into the stent.
Generically speaking, the stents of this invention use undulating torsion members which are &quot;open&quot; or &quot;unconfined&quot; at their apex or end member (104).  By &quot;open&quot; or &quot;unconfined&quot; we mean that the apex or end member (104) does not have any means in
that apex which would tend to inhibit the movement of the flexible linkage (discussed below) down between the arms or torsion lengths (106) of the torsion pair (102).
FIG. 1B shows another variation of the stent having a sinusoidal shaped torsion member (108).  In this variation, the adjacent torsion lengths (110) are not parallel and the wire forms an approximate sinusoidal shape before being formed into a
FIG. 1C shows a variation of the stent having an ovoid shaped torsion member (112).  In this variation, the adjacent torsion lengths (114) are again not parallel.  The wire forms an approximate open-ended oval with each torsion pair (116) before
being formed into a cylinder.
FIG. 1D shows another variation of the stent having a V-shaped torsion member (118).  In this variation, the adjacent torsion lengths (120) form a relatively sharp angle at the torsion end (122) shape before being formed into a cylinder.
As ultimately deployed, a section of the torsion member found on one of FIGS. 1A-1D would be helically wound about a form of an appropriate size so that the end members (e.g., 104 in FIG. 1A) would be centered between the end members of the
FIG. 4 shows a magnified portion of a stent-graft (viewed from the outside of the stent-graft) incorporating a stent such as is shown in FIGS. 2 and 3 and depicts a method for distributively attaching the stent to the graft component.
Specifically, end member or apex (104) is flanked by side lengths (106) and is looped therethrough by a filament (124).  The graft component (134) is seen in the background.  The filament (124) adheres to the graft (134) at the locations of contact (130)
between the filament (124) and the graft component (134).  It should be apparent that the apexes (104) are free to move in the direction shown by arrows (132) when the stent-graft is flexed.  This shows the ability of the various apexes to move
longitudinally with respect to each other and yet retain the graft component (134) reasonably snug against the inner surface of the stent and thereby prevent kinking of that graft component (134).
FIG. 5 shows a close-up of a section of a stent-graft according to the invention that is similar to the stent-graft portion shown in FIG. 4 but in which the stent is attached to the graft using loops (136) or eyelets on the stent.  Again this
shows a manner of distributively-attaching the stent to the graft component (134).  Again, end member or apex (104) is flanked by side lengths (106).  Although no filament (124 in FIG. 4) is shown in the variation in FIG. 5, it is contemplated that the
filament (124) may be used in conjunction with loops (136).  The graft component (134) is seen in the background.  These loops (136) may be of a material which adheres to the graft component (134) at the junctions shown at (138).  It is also contemplated
that the filament (124) may be of material which is either adherent to (such as a melt-miscible thermoplastic polymer) or not adherent to (such as a metal or thermoset polymer) the graft component (134) when used with the loops (136).
FIG. 6 shows, in side view, a variation of the stent (140) support structure made from wire and having flares (142) at one or both ends.  The flaring provides a secure anchoring of the resulting stent-graft (140) against the vessel wall and
prevents the implant from migrating downstream.  In addition, the flaring provides a tight seal against the vessel so that the blood is channelled through the lumen rather than outside the graft.  The undulating structure may vary in spacing to allow the
helix turns to maintain their phased relationship between turns of the helix and to conform to the discussion just above.  A flexible linkage between the contiguous helical turns is not shown but may also be applied to at least a portion of the helices.
The stent support structure may also be made by forming a desired structural pattern out of a flat sheet.  The sheet may then be rolled to form a tube.  FIG. 7 shows a plan view of torsion members (160) which may be then rolled about an axis to
form a cylinder.  As is shown in FIG. 8, the end caps (162) may be aligned so that they are in phase.  The flexible linkage (164) may then be included to preserve the diameter of the stent.  The graft component (166) is shown on the inner surface of the
stent.  Loops may be used as was described above.  The graft may be attached to the loops or filament in the manner discussed above.
The stent shown in FIG. 8 may be machined from tubing.  If the chosen material in nitinol, careful control of temperature during the machining step may be had by EDM (electro-discharge-machining), laser cutting, chemical machining, or high
FIG. 9 is a conceptual schematic of an isolated ring section of another variation of the stent component useful in this invention.  The FIG. 9 is intended only to identify and to provide conventions for naming the components of the ring.  FIG. 9
shows, in plan view, of the layout of the various components of a ring as if they were either to be cut from a flat sheet and later rolled into tubular formation for use as a stent with welding or other suitable joining procedures taking place at the
As ultimately deployed, a roll of the sheet found in FIG. 9 would be entered into the body lumen.  Typically, it would be folded in some fashion which will be discussed below.  A front quarter perspective view of the rolled stent (179) is shown
in the FIG. 10.
FIG. 11 shows a variation of the stent having a ring section (180) similar in configuration to that shown above and joined by tie members (182).  Those tie members (182) extend from the inside of a torsion pair (184) to the outside of a torsion
FIG. 12 shows a plan view of a variation of the inventive stent in which the number of torsion members (190) in a selected ring member (192) is fairly high.  This added number of torsion members may be due to a variety of reasons.  For instance,
FIG. 13 shows a variation of the invention in which the end caps (194) are bound by a long torsion member (195) and two short torsion members (196).  This torsion set (197) is in turn separated from the adjacent torsion set (197) by a bridge
member (198) which shares the bending load of the stent when the stent is rolled and the ends (199) joined by, e.g., welding.  The short torsion members (196) have a greater width than that of the long torsion member (195) so to balance the load around
the ring during deformation and thereby to prevent the bridge members from becoming askew and out of the ring plane.
It should be clear that a variety of materials variously metallic, super elastic alloys, and preferably nitinol, are suitable for use in these stents.  Primary requirements of the materials are that they be suitably springy even when fashioned
platinum/tungsten alloys, and especially the nickel-titanium alloys generically known as &quot;nitinol&quot;.
The &#39;700 patent describes an alloy containing a higher iron content and consequently has a higher modulus than the Ni--Ti alloys.
Nitinol is further suitable because it has a relatively high strength to volume ratio.  This allows the torsion members to be shorter than for less elastic metals.  The flexibility of the stent-graft is largely dictated by the length of the
torsion member components in the stent structural component.  The shorter the pitch of the device, the more flexible the stent-graft structure can be made.  Materials other than nitinol are suitable.  Spring tempered stainless steels and cobalt-chromium
alloys such as ELGILOY are also suitable as are a wide variety of other known &quot;super-elastic&quot; alloys.
Although nitinol is preferred in this service because of its physical properties and its significant history in implantable medical devices, we also consider it also to be useful in a stent because of its overall suitability with magnetic
resonance imaging (MRI) technology.  Many other alloys, particularly those based on iron, are an anathema to the practice of MRI causing exceptionally poor images in the region of the alloy implant.  Nitinol does not cause such problems.
The flexible linkage between adjacent turns of the helix (124 in FIGS. 2, 3, 4, and 8) or the loops (136 in FIG. 5) may be of any 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 may be a single or multiple strand wire (platinum, platinum/tungsten, gold, palladium, tantalum, stainless steel, etc.), much preferred in this invention is the use of polymeric
biocompatible filaments.  Synthetic polymers such as polyethylene, polypropylene, polyurethane, polyglycolic acid, polyesters, polyamides, their mixtures, blends, copolymers, mixtures, blends and copolymers are suitable; preferred of this class are
polyesters such as polyethylene terephthalate including DACRON and MYLAR and polyaramids such as KEVLAR, polyfluorocarbons such as polytetrafluoroethylene with and without copolymerized hexafluoropropylene (TEFLON or GORETEX), and porous or nonporous
polyurethanes.  Natural materials or materials based on natural sources such as collagen may also be used is this service.
As will be discussed below, the material chosen for the linkage or the loops is preferably of a material which can be bonded to the graft liner in a distributed sequence of points along the outside surface of the graft liner.  By bonding the
liner to the linkage or the loops in such fashion, the flexibility and resistance to kinking of the stent is maintained in the resulting stent-graft.  To state the central concept of the invention in another way, the graft component is to be
distributively attached to the stent structure at a number of sites.  The attachments should allow some movement between the graft component and the stent at the attachment points.  This may be accomplished by causing adherence of the graft independently
to at least some of the linkage, to the loops, or to one or the other.  Other structural attachments may be used to meet the functional requirements recited here.
The tubular component or graft member of the stent-graft may be made up of any material which is suitable for use as a graft in the chosen body lumen.  Many graft materials are known, particularly known are those used as vascular graft materials. For instance, natural materials such as collagen may be introduced onto the inner surface of the stent and fastened into place.  Desirable collagen-based materials include those described in U.S.  Pat.  No. 5,162,430, to Rhee et al, and WO 94/01483
(PCT/U.S.  Pat.  No. 9,306,292), the entirety of which are incorporated by reference.  Synthetic polymers such as polyethylene, polypropylene, polyurethane, polyglycolic acid, polyesters, polyamides, their mixtures, blends, copolymers, mixtures, blends
and copolymers are suitable; preferred of this class are polyesters such as polyethylene terephthalate including DACRON and MYLAR and polyaramids such as KEVLAR, polyfluorocarbons such as polytetrafluoroethylene with and without copolymerized
hexafluoropropylene (TEFLON or GORETEX), and porous or nonporous polyurethanes.  Especially preferred in this invention are the expanded fluorocarbon polymers (especially PTFE) materials described in British.  Pat.  Nos.  1,355,373, 1,506,432, or
1,506,432 or in U.S.  Pat.  Nos.  3,953,566, 4,187,390, or 5,276,276, the entirety of which are incorporated by reference.
polychlorotrifluoroethylene (PCTFE), and its copolymers with TFE, ethylene-chlorotrifluoroethylene (ECTFE), copolymers of ethylene-tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), and polyvinyfluoride (PVF).  Especially preferred, because of
its widespread use in vascular prostheses, is expanded PTFE.
In addition, one or more radio-opaque metallic fibers, such as gold, platinum, platinum-tungsten, palladium, platinum-iridium, rhodium, tantalum, or alloys or composites of these metals like may be incorporated into the device, particularly, into
the graft, to allow fluoroscopic visualization of the device.
The tubular component may also be reinforced using a network of small diameter fibers.  The fibers may be random, braided, knitted, or woven.  The fibers may be imbedded in the tubular component, may be placed in a separate layer coaxial with the
tubular component, or may be used in a combination of the two.
The preferred method of constructing the stent-graft is to first construct the stent incorporating a filamentary linkage of the type discussed above and then to place the tubular component inside the stent.  The tubular component is then expanded
using a mandrel or the like and heated to allow the materials of the filamentary linkage and the tubular graft component to merge and self-bind.
The attending physician will choose a stent or stent-graft having an appropriate diameter.  However, inventive devices of this type are typically selected having an expanded diameter of up to about 10% greater than the diameter of the lumen to be
The stent-graft may be tracked through the vasculature to the intended deployment site and then unfolded against the vessel lumen.  The graft tube component of the stent-graft is flexible and easy to fold.  Folding or otherwise collapsing the
stent structure allows it to return to a circular, open configuration.
FIGS. 14A-14C show a method for deployment of the devices of the present invention and allow them to self-expand.  FIG. 14A shows a target site (202) having, e.g., a narrowed vessel lumen.  A guidewire (204) having a guide tip (206) has been
directed to the site using known techniques.  The stent-graft (208) is mounted on guidewire (204) and is held in place prior to deployment by distal barrier (210) and proximal barrier (212).  The distal barrier (210) and proximal barrier (212) typically
are affixed to the guidewire tube (214).  The tether wire (216) is shown extending through loops (218) proximally through the catheter assembly&#39;s (220) outer jacket (222) through to outside the body.
FIG. 14C shows the final removal of the tether wire (216) from the loops (218) and the retraction of the catheter assembly (220) from the interior of the stent-graft (208).  The stent-graft (208) is shown as fully expanded.
Other methods of deployment are suitable for use with this device and are described in U.S.  patent application Ser.  Nos.  07/927,165 and 07/965,973, the entirety of which are incorporated by reference.
"Exterior Supported Self-expanding Stent-graft - Patent 6331188"