CA2220039A1

CA2220039A1 - Radially expandable vascular graft with resistance to longitudinal compression and method of making same

Info

Publication number: CA2220039A1
Application number: CA002220039A
Authority: CA
Inventors: Christopher E. Banas; Scott Randall; Tarun J. Edwin; Fariba Hurry
Original assignee: Impra, Inc.; Christopher E. Banas; Scott Randall; Tarun J. Edwin; Fariba Hurry
Current assignee: Bard Peripheral Vascular Inc
Priority date: 1995-05-12
Filing date: 1996-04-26
Publication date: 1996-11-14
Also published as: AU695269B2; AU5631596A; JPH11506944A; WO1996035577A1; EP1007348A1; US5628786A; EP1007348A4

Abstract

A microporous polytetrafluoroethylene endovascular graft (10) which has a reinforcing structure (16) integrally bound to the graft which permits radial expansion of the graft and stabilizes the graft against longitudinal compression upon application of an axial force thereto and against axial foreshortening upon radial expansion of the graft. The graft is particularly useful as a covering for an endovascular stent.

Description

WO 96135577 PCT~JS9~ '0~,909 RADIALLY EXPANDABLE VASCULAR GR~FT WITH RESISTANCE TO
LONGlIVD~AL COMPRESSION AND METHOD OF MA~ING SAME

Back~round of th,~ Tnvention The present invention relates generally to radially çxr~n-1~hle tubular grafts which are to longihl-lin~l c~ lession resnlting from an axially applied extern~l force, and is resistant to axial shrinkage or axial foreshortening upon radial expansion. More particularly, the present invention relates to a microporous polyl~ nuoroethylene (~PTFE") endovascular graft which has a leil~leillg structure integral with or bound to the graft which permits radial expansion of the graft and stabilizes the graft against axial shrinkage upon radial expansion of the graft. P~ e to axial shrinkage is particularly desirable where a vascular graft is moun~ted onto a radially e~ hle endoluminal stent or alone onto an expansion balloon for intr~lnmin~l delivery and radial exr~n~ion.
The term "longit~ in~l coll,~l~ssion~ means a reduction in a lon~ihl~lin~l dimension resull:ing from an axially applied e~t~n~l force.
Radially expandable stents are used to m~int~in an occluded ~n~tomi~al passageway in an unoccluded state. For example, the use of radially exr~n~l~ble stents in endovascular applications is well known, as exemplified by U.S. Patents 4,733,665, 4,739,762, 4,776,337, 4,793,348 relating to balloon expandable endoluminal stents, all issued to Palmaz, et al., U.S.
Patents 4,580,568, 4,800,882, 4,907,336, 5,035,706, 5041,126, 5,282,824 relating to balloon expandable and self-exr~n~ling endoluminal stents, all issued to Gianturco, et al., all of which are hereby incorporated by reference for the purpose of exemplifying stent types useful with the longit~ in~lly rei~ ced grafts of the present invention.
The use of radially expansible stents is not, however, limited to endovascular applications. Rather, various types of endolnminal stents are also employed to m~int~in other W 096/35577 PCTrUS~C/OS~0 alla~o~ical passageways, such as biliary ducts and ureters in an un~crhldecl condition. In those uses where it may be desirable to cover the stent with a biocomp~tible material, particularly one which will promote tissue ingrowth, such as PTFE, the stent is covered with the biocomr~ihle material. In ~e endovascular i~Le~vel~lional ml~rlir~l field, endovascular stents may be covered by co-axially disposing a tubular PTFE vascular graft over an endovascular stent, the stent-graft assembly is introduced endovascularly and delivered to the desired location, whereupon the stent-graft assembly is radially e~r~n~1~A, such as by balloon ~ t~ltic)n to secure the stent-graft assembly against the vessel walls.
Balloon exr~n~ion of the stent-graft assembly occurs at p.es~ ,s sufficient to cause both the stent and the graft to radially exp~n-l As used herein, the terms ~axial shrinkage"
and "axial foresho~ ," are used illLel~-h,...~ hly to describe a reA~lcti-)n in the longihl-lin~l length of the graft alone or the graft relative to the lon~h~ in~l length of the stent which occurs upon radial exp~n~iQn of the graft or the graft-stent cullll)"~ion. Axial shrinlcage of the graft relative to the associated stent typically results in exposure of the proximal and/or distal end of the stent. Such exposure may, in hlrn, provide a fluid passageway for body fluids, such as blood, to flow between the abluminal wall of the graft and the lllmin~l wall of the anatomical passageway, e.g., a blood vessel. Such an escaping flow as in, for example, an arterio-venous fistula repair, is undesirable and may be associated with increased mortality and decreased patency of the graft or stent-graft. It is desirable, therefore, to provide a tubular PTFE
struchure which is lesi~ to axial shrinkage during radial expansion of the PTFE structure.

_ W 096/35577 PCTrUS96105909 R~ tl of the Prior Art The use of co~ting.c, wraps and impregnated materials in co,ljul";Lion with PTFEvascular grafts is known. However, in the prior art, such coatings, wraps or impregnated materials are used for example, to I) increase the tear strength of the PTFE (Mano et al, U.S.
Patent No. 4,306,318); ii) enh~nre endothelialization of the PTFE; iii) enh~nre mechanical compliance of the PTFE (Gogolewski, U.S. Patent No. 4,834,747); iv) seal the microporous network present in exr~n~le~l PTFE (Flecl~e.,~l~hl, et al, U.S. Patent No. 4,902,290), v) increase radial and longihl-1in~l elasticity of the PTFE graft (Tu, et al, U.S. Patent No.
~,061,276); vi) provide a self-sealing component to the PTFE graft to seal suture holes or needle punctures (Mano, U.S. Patent No. 4,304,010); or vii) provide binding sites for ph~rm~ologically active agents (Greco, et al, U.S. Patent No. 4,749,585; Mano, U.S. Patent No. 4,229,838).
To date, however, the prior art is devoid of an tubular PTFE structure having means associated therewith to impart a le~ ce to longitll~lin~l co~ ession or axial shrinkage upon radial exr~n~ion of the tubular PTFE structure. The present invention offers a solution to this defic:iency in the prior art.

Sllmm~T~ of the Inventio~
It is an object of the present invention to provide a means for structurally leillfolcillg a tubular PTFE structure to impart resistance to longitll~lin~l c~ lplession or axial shrinkage which occurs during radial expansion of the tubular PTFE structure.

W O 96/35577 PCTrU3g6/05~0 It is a further object of the present invention to provide at least one ~ lly longitl~in~lly non-compressible, longihl-lin~lly non-compliant structure ~ ri~ g integrally bound and axially po~itio~ along a lon~it l-iin~l axis of the tubular structure PTFE.
It is a still further object of the present invention to provide at least one lcillçolcillg structure integrally bound and axially positioned along the longit l~in~l length of the tubular PTFE structure on at least one of a luminal wall surface, an abluminal wall surface or residing within the wall of the tubular PTFE structure.
It is yet a further object of the present invention to provide at least one ~ olcillg structure made of a biocomratihle melt thermoplastic which is integrally bound to the microporous matrix used to make the vascular graft.
It is a still further object of the present invention to provide at least one lCillL;~ g structure made of a melt thermoplastic having a melt viscosity sllffiripnt to pelleLl~te the microporous matrix of çxr~n(1e~1 polytetrafluoroethylene.
It is a still further object of the present invention to provide a l~.,~l~;illg structure made of a solvent borne, thermoplastic or photo-curable plastic capable of integrating into interstices in exran-le~l polytetrafluoroethylene.
It is yet another object of the present invention to provide a lcl-~rcillg structure made of plastic materials selected from the group co~ ting of polyamides, polyimides, polyesters, poly~l~ylenes, polyethylenes, polyfluoroethylenes, polyvinyl~yl~lidones, fluorinated polyolefins such as fluorinated ethylene/propylene copolymers ("FEP") such as tetrafluoro-ethylene/hexafluloplo~ylene copolymer, perfluoroalkoxy fluorocalbolls ("PFA") such as tetrafluoro-ethyl/perfluoro propyl vinyl ether copolymer, ethylene/tetrafluoroethylene copolymers ("ETFE"),polyvulyl~yll~lidone(~PVP") or similar bioc~mp~tihle plastics which are capable of being bound to e~cr~n-1~1PTFE at tempeldL~Ires below the sintering ltlll~ldLulc WO 96135577 PCT/IJS9SJO_91)~

of PTFE of at least 327~C, such as by cross-linking in the presence of cross-linking agents or mech:~nir~l bonding by application of ples~ul'e to cause the thermoplastic to flow into the microporous structure of the exran~ 1 PTFE substrate.
It is a still further object of the present invention to provide an aqueous dispersion of a leill~l.;ulg m~t~ri~l which is coated onto an ~xr~n-led PTFE tubular structure. After coating and drying the lCUlr~ ;illg m~t~ri~l onto the exran~led PTFE tubular ~Llu~;lulc the fe;llrol~ g material imparts lesi~ e to longibl-lin~l co~ ion or axial shrinkage upon radiale~r~n~ion of the tubular PTFE structure.
It is yet a further object of the present invention to provide an aqueous dispersion of polytetrafluoroethylene in surfactant, such as polyLeLldfluoroethylene octyphenoxy-polyetho~y~;ll~ol, as a coating mto~ m for coating the dispersion onto an expanded PTFE~
tubuLIr structure.
It a still further object of the present invention to provide a structural reinforcement member made of a bio-comr~tihle metal or plastic, either co-extruded with or integral with the tubular PTFE structure, to impart resi~t~nee to lon~it~ in~l cc,.~res~ion or axial shrinkage which occurs during radial expansion of the tubular PTFE structure Another object of the present invention is to provide an a~?~dlus for m~mlf~etllring the longinl-lin~lly non-compliant PTFE tubular structure and a method of m~mlf~etllre thereof, employing a tubular mandrel for canrying the tubular PTFE structure, the mandrel having a plurality of openings passing through the tubular mandrel and co~n~ tinE between a mandrel lumen and an outer surface of the mandrel, a generally cylindrical mold having a plurality of longihl~lin~l grooves, whereby the exr~nr1Pd PTFE tubular structure is mounted onto the mandrel, the generally cylindrical mold is then concentrically disposed about the tubular PTFE structure and mandrel, there being tight tolerances between the components of W 096/35577 PCTrUS96/05909 the assembly. A melt thermoplastic, such as FEP, is injected into and through the longihl~in~l grooves in the mold, and a vacuum is applied through the lumen of the mandrel. The vacuum acts on the melt thermoplastic through the openings in the mandrel and the microporous matrix of the exp~n~le<~ PTFE to draw the melt thermoplastic into the microporous matrix of the expanded PTFE. After cooling the assembly, the assembly is tli~eng~ed, and the reslllting hubular PTFE structure has a plurality of substantially non-compliant longihl~lin~lly oriented ~c~lrOlCu~g ~Llu~;LulcS made of the melt thermoplastic integrated with the microporous matrix of the PTFE hlbular struchure.
These and other objects, r~,aLu.cs and advantages of the present invention will become more a~cllL to those skilled in the art when taken with refercuce to the following more detailed description of the pl~,rcl~cd embo(~ of the invention in conjull~;Lion with the accc,..l~lyiulg drawings.

Brief Description of the Drawin~
Figure 1 is a perspective view of a vascular graft having a r~iu~.ciu.~ structure to resist axial shrinkage during radial expansion.
Figure 2 is a cross-section~l view taken along line 2-2 of Figure 1.
Figure 3 is a diag.,.."",~tir elevational view of a second embodiment of the present invention illustrating application of a solvent-borne lch~c~lciulg structure to a vascular graft.
Figure 4 is a diagl~""-~tic end elevational view of the second embodiment of thepresent invention illustrating application of a solvent-borne lch~rolcillg structure to a vascular graft.
Figure 5A is a perspective view of a third embodiment of the present invention illustrating a plurality of reinforcing rib structures associated with a tubular vascular graft.

W 096/35577 PCTrUS96105909 Figure 5B is a cross-sectional view taken along line 5B-5B of Figure 5A.
Figure 6 is partially exploded dia~-,...,."i1~;r view of the present invention illnstr~ting the method for applying an integral i~:ulrvl~ g structure to a tubular vascular graft.
Figure 7 is a partial cross-sectional view illu~ a~illg a mandrel and a mold used to apply S an integral ~ rOlcillg structure to a tubular graft in accordallce with the method of lhe present invenl:ion.
Figure 8 is a cross-sectional view taken along line 8-8 of Figure 7, illustrating a mandrel, mold and vascular graft assembly in accordance with the method of the present invem:lon.
Figure 9 is a cross-sectional end-elevational view illustrating a second embodirnent of the m,andrel, mold and vascular graft assembly in accordance with the present invention.

D~.t~iled Desc~i~lion of the PlC~r~ d Fmho~iime~tc Turning now to Figures 1-2, there is illustrated a first ~l~Ç~ d embodiment of avascular graft 10 with structural means 16 for imparting the graft 10 with resi.ct~nre to lon~ in~l co~ es~.ion or axial shrinkage operably associated with a tubular graft member 12. Tubular graft mPmhe.r 12 has an outer wall surface 13 and a central lumen 14 defining an inner lnmin~l surface 15. Structural means 16 consists generally of a lei~c,lchlg member which. is co-extruded with, bonded to or integral with either the outer wall surface 13 or the luminal wall surface 15. Where the ~.Llu~;Lulal means 16 is bonded to the graft 10, bonding may be accomplished by a variety of bonding methods. For example, a bond may be created by mech:~nic~l means, such as applying positive or negative pressure which causes physical interaction between the structural means 16 and the microporous matrix of the graft member 12. M;ech~nic~l bonding may be accomplished by application by use of melt thermoplastics as W 096/35577 PCTrUS96105909 the structural means 16, caused to flow under the influence of a heat source, such as ultr~ound, resistive heating, l~er irr,~ tion, etc. ~llr~ iv~ly, the ~Llu~;lulal means 16 may be çh~mir~lly bound, such as by cross-linking agents or bioco...r.~ le adhesives, to the tubular graft member 12 during m,lm~f~t~lre.
S The ~tlu~;luldl means 16 may further consist of a l~ illrulcillg region 19 formed within the graft ..~ 12 wall thir~n~os~ between the ]~lminAl surface 15 and the outer wall surface 13 of the tubular graft member 12. The method used to form the ~eulroleulg member 16 or the reiurolci-lg region 19 will be more fully described helei.lar~r with lcfe.cllce to the best mode ~lcsellLly known to the UlvenlOls hereof.
In accol~lce with the yl~r~l~cd embodiment of the present invention, the tubular graft member 12 is made of microporous ~r~n~ poly~t;L.dnuoroethylene (e-PTFE). The method of making microporous e-PTFE plc,~llleses by paste extrusion and exr~n~iQn of the extrudate is well known in the art. Miclu~ul~us e-PTFE is comprised of characteristic nodes and fibrils interconnPcting the nodes. Interstices between the nodes and fibrils form pores which exist throughout the material matrix of the e-PTFE. E-PTFE vascular grafts have met with considerable acce~Lallce due, in large part, to their bioc~ )ility and suscey~ibility to tissue ingrowth into the microporous material matrix.
Tubular vascular grafts made of e-PTFE are well suited for endolllmin~l use. A
~lill~;i~al difficult associated with en~ lllmin~l grafts lies in the means used to attach or anchor the endoluminal graft to elimin~te displacement of the graft due to body movements or fluid flow through the anatomical passageway in which the graft is placed, e.g., a blood vessel. As exemplified by Barone, et al, U.S. Patent No. 5,360,443, issued November 1, 1994, which is hereby incorporated by reference, endovascular stents have been used as an anchoring m~ch~ni~m when sutured to a graft, endovaccnl~rly delivered and radially exr~n~led to exclude W O 96135'-.77 PCTrUS9C/0~90~

an abdominal aortic aneurysm. In Barone, stent is provided at proximal and distal ends of a graft a]ld is sutured thereto, such that a lon~itll~in~l section of the stent is UllcO~ d to provide direct contact between the stent and the intima. The entire assembly is delivered using a deliveIy c~thPter and exp~n~l~hle balloon. Upon positioning of the stent in the desired endovascular position, the exran~l~hle balloon is ~l~,S~7Ule ~ t~te~l. The radially e~al~.iv~;
force from the e~ a~ g balloon impinges upon the endovascular stent and causes the stent to radially expand into contact with a luminal surface of the graft and the intimal surface of the V~Cll~ re.
When used as a covering for an endovascular stent, an e-PTFE vascular graft is radially expanded contemporaneously with the expan~ion of the endovascular stent. One particular fliffis~lllty associated with balloon expansion of a stent-graft assembly is that the balloon will typica]ly assume an bulbous configuration at each of its proximal and distal ends. Balloon exr~n~ion typically forces the graft or the stent-graft assembly into a torroidal shape with the proximal and distal ends flaring away from the central axis of the stent-graft assembly wi~ a relatively narrow center section interm~ te the flared distal and ~lo~ lal ends. This phenomenon occurs because there is little resi~t~nre to inflation at each of the proximal and distal ends of the balloon relative to the balloon area covered by the stent-graft assembly. The e~p~n~io~ balloon thus a~sllm~s a "dog-bone" configuration with the proximal and distal ends radially exp~n-ling to a greater extent tnat a central region along the longit~-(1in~1 axis of the stent-graft or graft. The infl~tion ~ S~.ule within the balloon exerts an radially ~a~ e force against the balloon along its entire longitll-lin~l axis. However, because the device to be expanded, i.e., a stent-graft assembly or a graft, restrains against radial expansion, the expansion ~l~s~.ules within the balloon act first on the proximal and distal ends which are un-restrai]led by the device to be e~cp~ntle(l, thereby causing the ~,o~iulal and distal ends to inflate W O 96135577 PCTrUS9G~05~G~

first, causing the dog-boning effect. The rçsnlting effect is that the graft or the stent-graft assembly is non-uLuÇol.llly radially expanded along its lon~ih~in~l axis.
A ~.hl~i~al difficulty with stent-graft assemblies, i.e., those in which an endolnmin~l stent is covered or lined with a graft, lies in the axial foresho-~ ."lg of the graft relative to the stent upon radial exp~n~i~ n of the stent-graft assembly. Where either a proximal or distal end of the stent is exposed, there is a great probability that the stent will allow body fluids, such as blood in the vascular system or bile in where the stent-graft is employed in a biliary duct, to ci.~;u,..ve-l~ the stent-graft assembly c~llsing an undesirable leak. Thus, there is an appreciable danger of increased mortality or morbidity where a graft covering longitll~lin~lly foreshortens relative to the stent during radial expansion of the stent-graft assembly.
Axial foreshortening of a radially e~r~n-l.ocl graft complicates endolnmin~l graft or stent-graft delivery. As the graft is radially exr~ntle~l and longibl(1in~lly foreshortens, there is a b-lnrhing phenomenon which occurs. The b.~"rl~ g phe..o.lle--on results in a greater density of graft material per area of surface are of the expansion balloon. The result of graft material bnnrhing is to increase expansion p.es~u.es required to radially expand the graft or stent-graft assembly to the same (li~mPtrr over a non-longibl(lin~lly foreshortened graft.
To guard against undesirable axial foreshortening of the graft upon radial e~cr~n~ n, the inventive l~h~-~;ed graft member 12 has at least one ~,hlrulcil~g structural support means 16 operably associated therewith. The ~ei"r~ l-g ~Llu~;luldl support means 16 may consist of alternative .eh~-~;iu-g structures bonded to, co-extruded with or integrally incorporated within the graft member 12. In accordance with alLel.laLi~/e ~leÇ~ d embo~limrnt~ of the present invention, the rehlfclcillg structural support means 16 is either molded onto a tubular graft member 12 or coated onto tubular graft member 12 by application of a dispersion solution, either in aqueous or colloidal form.

W 096/35577 PCTrUS9C/OJ~09 Regardless of the manner in which the le~rorcu~g structural sup~o.~ means 16 is produced in association with the tubular graft member 12, the reil~lcilly, structural ,u~po~L
means 16 will impart resict~n~e to longi~ in~l colll~l~ssion and axial foreshortening of the tubular graft member 12. The plOp~y of l.,.~i!iL~ e to lon~ in~l colll~ ssion and axial S foresho.l~ g exists irrespective of the force or impetus which causes the lon~ in~l cc,lll~l, ssion or shrinkage. Thus, the property of resict~n~e to longihl(lin~l colll~lession and axial foreshortening will restrain the tubular graft member 12 during radial exp~ncion of the tubular graft member 12, during application of an externally col..~.~ssive force, or will operate against recoil properties of the e-PTFE material.
As illustrated in Figures 1 and 2, the ~ rolc~llg structural support means 16 is either applied to the outer 13 or inner 11 wall surface of the tubular graft m~mh~r 12 or inc(3-~-J-d~d as an integral rei lrorcillg region 19 of the material matrix forming the tubular graft member 12. ln accordance with this first ~l~Ç~..ed embodiment of the reinro.ced vascular graft 10, the reinroicillg structural support means 16 is formed of a biocompatible longihl~lin~lly inc~ p.e3sible plastic rnaterial, such as a melt thermoplastic selected from the group concicting of polyamides, polyimides, polyesters, poly~lo~ylenes, polyethylenes, polyfluoroethylenes, polytetrafluoroethylenes, polyvinylpyrolidones, fluorinated polyolefm3 such as fluorinated ethylene/propylene copolymers ("FEP") such as tetrafluorethylene/h~Y~ .. o~ ylene copolymer, perfluoroaLkoxy fluorocarbons ("PFA") such as tetrafluoroethyl/perfluoro propyl vinyl ether copolymer, ethylene/tetrafluoroethylene copolymers ("ETFE") or similar biocompatible plastics which are capable of being integrally bound to e~pan~le~l PTFE.
r~ ively~ the reinforcing structural support means 16 may be formed of a curable plastic materiial, such as polyv",yl~yllolidone, which is curable upon exposure to thermal energy, such as application of laser irradiation, or upon exposure to light, such as a W curable W O 96135577 PCTrUS96/05909 "late,ial. ~llr~ iv~ly, the leillforcing structural support means 16 may be formed of a biological tissue, such as collagen, which is capable of being cured by cross-linking agents into a s~lkst~nti~lly monolithic structure bonded or integral with the e-PTFE tubular graft material 12.
The rehlro,~ structural support means 16 may also consist of a m~.t~llic wire co-extruded with the e-PTFE tubular graft material 12 and po~itit n~l within the wall thif kn~ss of the e-PTFE tubular graft material 12. Al~ dliv~ly, the m~t~llir~ wire structural member is capable of being co-extruded with plastic beading, such as non-exp~n-l~od PTFE, as is known in the wire-making arts where PTFE is employed as an electric~l in~ ting covering for electrical wires, and the co-extruded metal-PTFE beading then mech~nir~lly or cht~mically bonded to the outer 13 or inner 11 wall surface of the e-PTFE tubular graft material 12.
Those skilled in the art will a~plecid~ that a myriad of biocol,~aLible materials exist which may be molded with or coated onto an e-PTFE tubular graft member. However,opLil~um material will have a flow viscosity sufficient to p~ Llale into a microporous node-fibril matrix of e-PTFE having an average pore size of 5-200 microns at l~",~ldl~lles below the sintering temperature of PTFE. In addition, the o~ "ull, material must be substantially inco",~lcssible, yet pliable to allow for flexion of the resnlt~nt vascular graft.
In accordance with the most ~,~relled embodiment, and the best mode contemplated for the invention the r~il~l-;illg ~Llu~;Luldl support means 16 consists of at least one of a plurality of low-profile rib members bonded to the inner 11 or outer wall surface 13 of the tubular graft member. Bonding of the rib member is enh~n~ec~ by driving the material used to form the low profile rib member into the microporous material matrix of the e-PTFE material forming the tubular graft member 12. Integration of at least a portion of the rib member into the e-PTFE
microstructure may be accomplished by application of the material used for the reinforcing W Og6~S~577 PCTnUS9~0~909 structllral support means 16 under the influence of positive ~res~ule, while simlllt~n~ously el~atiLIg a negative ~lCS~ul~ on an opposing wall surface of the tubular graft member, such as within the lumen 14 of the tubular graft member 12. The applied positive and negative S:jul~S cooperate to drive the material used for the lc..~ rcillg structural support means 16 into the material matrix of the tubular graft member 12 and create a ~ region 19 within the wall of the tubular graft member 12. The method and a~Lus for ~ ,S~iUlC~
forming the reinforcing region 19 and the structural support means 16 will be more fully described hereinafter with rer~ ce to Figures 6-9.
It is important that the l~ulrOl~ci~g structural support means 16 or the l~...rOl.;ill~ region 19 extend along an entire lon~ihl~lin~l length of the tubular graft m~mher 12. In this ,~ el, at least one longit~ in~l aspect of the tubular graft member 12 is supported by the ltil~ULCillg structural support means 16 against lt ngi~ldin~l co~ ,ssion or axial shrinkage.

A length of e-PTFE vascular graft was mounted on a cylindrical mandrel. A
corresponding length of non-exr~n-led PTFE beading was longihl~in~lly applied to the outer wall of the e-PTFE vascular graft. The beading and graft were tied with wire at each end to . . .~; . .l ~; . ~ the positioning of the beading on the graft. A heat gun mounted with a thermal tip, was applied only to the beading to sinter the beading. After untying the wire restraints, the graft visually inspected. Upon visual inspection, the beading appeared to adhere to the graft.
Upon In~nual inspection, however, the beading could be peeled from the outer wall surface of the graft.
In the second run of the test, a length of e-PTFE vascular graft was mounted onto a cylindrical mandrel. A corresponding length of non-exr~ntled PTFE beading was longihldin~lly applied to the outer wall surface of the e-PTFE vascular graft and restrained onto W 096/35577 ~CTrUS96/05909 the e-PTFE graft with wire ties at each end. The assembly was loaded into a ~ e..llg oven prehP~te~l to 375~ C for six Illill-lles, after which the assembly was allowed to cool. Upon visual inspection, the beading a~pealed to be fully adhered to the graft. The graft was mounted onto an angioplasty balloon and expanded. During radial expansion, the beading dislodged from the graft.
A third run of the test was alLc~ Led using FEP tubing having an inner ~ mPter of 0.020 inches (7.9 mm) and an outer diameter of 0.035 inches (13.8 mm). The FEP tubing was longitl-tlin~lly applied to the outer wall surface of a length of e-PTFE vascular graft mounted onto a cylindrical mandrel. The FEP tubing was ,e~Lldilled by helically winding high ~l~ ,ldture PTFE tape about the entire length of the e-PTFE graft and FEP tubing. The wrapped assembly was placed into a sintering oven prehP-~tPcl to 375~ C for six ."i,...~t;s.
During heating, the FEP tape unraveled and the FEP melted and beaded on the e-PTFE graft.
A fourth run of the test was contillctecl, subsl;~ g TEFLON thread tape for the high temperature PTFE tape and heating con-lllct~Pd at 265~ C, the melt point of FEP, for 5 ~ PS.
The FEP tubing did not melt or stick to the e-PTFE graft.
Sllr~essive runs of the test were con~ ct~Pd, each repeating the steps of the fourth test run, but "lclea~ing the heating lclll~eldture 10~C with each run. It was not until heating was performed at 295~ C that the FEP melted and adhered to the graft. The FEP-adhered graft from this final test was mounted onto a PALMAZ stent and radially e~r~n~l~cl using an angioplasty balloon. Upon radial expansion on the PALMAZ stent, the FEP longibl~lin~l segment m~int~inP~l adhesion to the graft and did not exhibit any measurable foreshortening from the non-radially ~xr~ntlt-cl condition.
Turning now to Figures 34, there is described a process for applying a coating of a material used to form the lchlrolcillg structural support means 16. In this second preferred W 096135577 PCTnUS9610~909 embodirnent of the present invention, a tubular graft member 20 is co-axially moullted onto a rotatable mandrel 22. Rotatable mandrel is, in turn, operably coupled to a drive motor 26 which imparts a rotational force to the rotatable mandrel 22. The material used to form the rehlfolcillg structural support means 16 is carried in a dipping tank 24. In this embodiment S of the invention, the ~ cillg material is formed as one of an aqueous dispersion, a solvent-borne system, or a colloidal ~u~ellsion of poly",~ ion mono~ls in the presence of cross-linkin;g agents or photo curing agents. In either case, the leil rOl ;i~lg material is applied in a fluid c~n~lition as a coating onto at least one continuous lt-n~ tlin~l section of the outer wall surface 13 of the tubular graft ll.P..,hel 20. After coating, the lc;il~l._~ material is cured by application of thermal energy or light energy to form a structural coating on the outer wall surface 13 of the tubular graft member 20. Prior to curing, the fluid coating may be driven into the l licLoporous e-PTFE matrix of the tubular graft member 20 by drawing a negative pressure from the central lumen 14 of the tubular graft member 20.

An e-PTFE vascular graft having rçsict~n~ e to axial foresholL~nillg was may be coating the outside surface with polytetrafluoroethylene octyphenoxy-polyetho~ye~ol aqueous dispersion (FLUON AD-1, ICI Advanced Materials). The FLUON AD-l aqueous dispersion contains negatively charged PTFE particles having a mean size in the range of 0.1-0.3 ll~lClOnS.
The aqueous dispersion co,.~lillll~s about 60% PTFE by weight and is stabilized with non-ionic surf~- t~nt~.
A 3 mrn outer ~ m~t~r thin-wall IMPRA graft, 25 cm in length was dipped in FLUONAD-1 to wet the outside surface of the graft. The graft was air dried, blow dried and sintered at 37S~ C for four l~ s.

W O 96/35577 PCTrUS96/05909 T on~ihlAin~l co~ cssion was measured by placing two l~rc;lellce ,.~.k;l~g~ one inch apart, m~ml~lly cull~ ,ssillg the lmro~t~l and coated graft on a mandrel to the greatest extent possible and then measuring the ~ t~nre between the ,crt:-cnce m~rking~ after colllpl~ssion.
The pre-coating initial length was 1.3 inches and was m~ml~lly com~lessible to 0.5 S inches. Post-coating, the uncolll~lcssed length was 1.35 inches and was m~ml~lly co.ll~,cssible to 0.98 inches, yielding longi~ in~lly co.lll"essibility of 61.5% pre-coating and 27.4% post-coating. Peak radial exp~n~iQn pressure was 8 Atm and rem~in~-l llnrh~nged for the coated and the llnro~t~l grafts.
To facilitate loading of the fluid-state IeillÇo,eulg agent onto the e-PTFE graft, the 10 tubular e-PTFE graft may, alternatively, be a carbon-c~ ;ig graft. In this embo~lim~nt~ the component of the carbon-cont~ining graft is used as an adsorbent for the fluid-state lGillr~JlCillg agent. After adsorption onto the cont~in~oA within the e-PTFE microporous rnatrix, the fluid-state Leillrulcillg agent may be processed as described above to form the lcillfolcillg structural support means 16. Carbon-cont~ining PTFE grafts are a variant of vascular grafts in which the e-PTFE llli~lU~Ul~US matrix has micro particulate, such as activated, dispersed throughout the matrix, or lining the luminal or abluminal walls thereof. A ~lcrel~,d process for producing a carbon-co~ ,g graft is that more fully described in co-pending U.S. Patent Application Serial No. 08/311,497, filed S~Le-l-b~ 23, 1994, filed by McHaney, et al., and co-owned by the assignee hereof, which is hereby expressly incorporated by lefercllce for the purposes of setting forth a process for making a carbon-cont~ininp vascular graft and a carbon-coll~ .;.-g vascular graft produced by such process.
Turning now to Figures 5 and 6, there is disclosed a third embodiment of the invention in which there is a graft member 30 having a central lumen 32 and at least one of a plurality of longihl~lin~lly e~ l;.,g rib m~tnhers 36. The graft member 30 is made in acc~,dallce with W O 96/3~iS77 PCT~US~610 the exl~rusion process described in co-pending application Serial No. 08/134,072, filed October 8, 1993 by R. Kalis, which is coll"llollly ~si~nP~l to the ~C~ignPe hereof, and which is incorporated by ler~lellce. Under the Kalis co-~e~ g application, a tubular e-PTPE graft is formed with integral rib ~,LIu.;Lul~s by extrusion of a PTFE billet, expansion and sin~ering. In S accordance with the pler~.L~d embodiment of the present invention, the plurality of lon~ihl~lin~lly ex~ rib ..,~"hel, 36 are ~ n~ifi~cl by application of thermal energy to only the rib m-omhers 36 without exposing the e-PTFE tubular graft wall surface 33 to thermal energy sufficient to densify the wall surface 33. The th~nn~l energy may include selective heating of the rib ~PIII1'~1~ 36 or selective cooling of the rib lllelllber", 36 during lon~ lin~l ex~ ;on of the graft to restrain the rib-members from expancion This third plerellcd embodiment of the present invention also contemplates that the rib mtomhers 36 are selectively integrated with a lei,lfo,cillg structural support means 16. After curing the leil~l~ g StrUCtllral ~7U~J~1Ull means 16, each of the plurality of rib members 32 operate as structural suppûrt members which resist longi~ in~l cc,l~ ,,ion or shrinkage of the tubular graft member 30.

A 4mm inner ~ m~ter single ribbed graft made in accordance with the process described in co-pending Kalis patent application Serial No. 08/134,072, was obtained and sectioned into ten 3 inch (7.62 cm) sections. A two reference m~rking.c were placed in the center ûf each 3 inch (7.62 cm) section, ûne inch (2.54 cm) apart, and each sample was lûaded ~, onto a 3.56 mm outside ~ m~ter mandrel. The samples were longitll~in~lly co~ ssed m~ml~lly to the greatest extent possible and the distance between the lerelellce ",~,ki,-g.c measured. The samples were then returned to their original 3 inch length. Seven of the samples were again mounted onto a single 3.56 mm OD mandrel, and each sample was secured W 096/35577 PCTrUS~G/0~09 to the ~ 1 with wire ties. A Weller Model EC2001 soldering gun was set to 745~ F. The tip of the soldering iron was run down the rib of each of the seven samples using slight L)Ies~ulc until the rib began to melt and malform. After cooling, each graft was longi~ in~lly compressed m~ml~lly on the mandrel and the extent of coll~lession measured by l,leasul~
the tli~t~n~e belw~ll the two ler~l~nce ~ k;ll~,~. Qualitatively, the den~ifie~l ribs were very stiff and required application of more pr~s~,ul~ to COlllylc~SS than the pre~n~ifito~l ribbed grafts.
Table 1, below, ~ ,..",~",es the results of the pre~len.cifir~tion and post~len~ifi~tion ng~ in~l colll~l~s~,ionmeasulclL~

10Sample Pre-D~ ;r.~ .. n Compression Post-D.l~ ~r n (% Original Length) Compression (% Original Length) A 61.9 58 B 64.95 59 C 67.30 62 D 64.75 65 E 66.45 67 F 64.35 NT
G 64.95 NT
H 66.85 NT
64.25 NT
J 67.45 NT
AVG65.2 STD 1.54 62.2 STD 3.43 NT =Not Tested STD=Standard Deviation We turn now to Figures 6-9, which illustrate the ~rerelled method for rnaking the reinforced graft 10 of the present invention. With particular reference to Figures 6-8, there is illustrated an vacuum molding assembly 50 for making the inventive leillrorced graft 10 of WO 96135r.77 PCT/US!~610r~)0 the present invention. Vacuum molding assembly 50 con~i.ct~ generally of a molding "la"dl~l 52 andL a vacuum mandrel 62. Vacuum mandrel 62 consists generally of a rigid tubular member having a central vacuum lumen 64 and a plurality of vacuum ports 66 which pass through the rigid tubular member and c~ -----ir~l~ between the central vacuum lumen 64 and S an outer surface of the V~LCUUlll mandrel 62. Vacuum mandrel 62 has a vacuum connection, such as a hose barb (not shown), for connPcting a vacuum line to the vacuum mandrel 62 such that a negative ples~.ur~ may be drawn through the plurality of V~CUUlll ports 66 and the central vacuum lumen 64. Vacuum l"a.~dlel 62 has an outer ~ , having a close fit tolerance with an inner ~ m~ter of a tubular graft ",e",~el 60 such that the tubular graft member 60 may be co-axially engaged Ih~ ,~Oll and readily removed ~ ,crl.,lll. As an ~ 1 ivt; to the plurality of vacuum ports 66, various configurations of opening passing through the v~cuuln mandrel 62 may be employed. For example, at least one of a plurality of longihl~lin~l slots (not shown) may be formed in the vacuum mandrel 62. So long as at least one entire longihltlin~l section of the tubular graft member 60 is exposed to a negative ~,es~u,~: from the central vacuum lumen 64, any configuration of suitable vacuum openings may be employed.
The vacuum molding mandrel 52 has at least one of a plurality of injection ports 54 and at least one mold recess 56 in an inner luminal wall surface of the molding ll,a,~ ,l 52. The at least one mold recess 56 extends the entire longit~l-lin~l axis of the molding mandrel 52 and is in flllid flow c~ ir~rion wiun uhe piuraiiiy of injection ports 54.
In operation, a tubular graft member 60 is mounted onto the vacuum mandrel 62, and the graLft 60 mounted vacuum mandrel 62, is co-axially disposed within the lumen of the molding mandrel 52. A negative IJlCS~iUlC iS applied to the vacuum mandrel 62 and a fluid state lCUl~lCIll~ material (not shown) is injected, under positive ~lCS~UlC, through the plurality of injection ports 54. Upon entering the mold recess 56 through the injection ports 54, the W O 96/35577 PCTrUS96N5909 :illrOl~ulg material flows along the longitl~in~l axis of the mold recess 56 and is drawn into the microporous e-PTFE matrix of the tubular graft member 60, thereby r~nll~il~ a ~ ~r~illg region within the wall thicknPss of the tubular graft member 60.
An alternative embodiment of the molding assembly 80 is illustrated with ,er~-cllce to S Figure 9. As illu~Lldl~d in Figure 9, a mold block member 82 and mold cover member 86 are employed. Mold block member 82 has a mold cavity 84 formed therein, while mold cover member 86 has a molding cover cavity 88 formed therein. The mold cover member 86 has at least one fluid flow opening 90 passing from external the mold cover mPmher 86 to the mold cover cavity 88. Fluid flow ~e~ lg 90 is used to introduce the .ei~lcillg m~tPri~l, in a fluid state, into the mold cover cavity 88 such that it contacts a tubular graft member 60 resident in the mold cover cavity 88 and the mold cavity 84. As with the above-described embodiment, the tubular graft member 60 is carried co-axially on a vacuum mandrel 92 having a vacuum opening 96 passing through at least a portion of the mandrel wall. Vacuum opening 96 cO,... i~tPs between a central vacuum lumen 98 and an outer surface of the vacuum ll~ cl 92. Where the vacuum opening 96 is formed of a longit~ in~l slot in the vacuum mandrel 92, or where the vacuum opening 96 is sufficiently large to cause a large surface area of the tubular graft mPmhçr 60 into the vacuum opel.,-lg 96, thereby creating an increased risk of tearing or ~un~;Lul.~lg the tubular graft member 60, it is desirable to co-axially interdispose a permeable tubular b~cking member 92 b~lw~ll the tubular graft member 60 and the vacuum mandrel 94.
Permeable tubular backing member 92 reinforces the tubular graft member 60 and plotec~ it against tearing or puncturing by impingement upon the edges of the vacuum opening 96, but is sufficiently permeable to permit drawing a negative pressure through it to cause the fluid e-,lrulc.-lg material to penetrate the microporous matrix of the tubular graft member 60.

Those skilled in the art will understand and a~pleciale that while the present invention has been described with reference to its ~l~r~ ,d embo~limPnt~ and the best mode known to the hlvellLols for making the ~lere~l~d embo~limPnt~, various substitutions of materials, procPssing steps and process parameters may be made without departing from the spirit and S scope of the invention, which is to be limited only by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A polytetrafluoroethylene graft, comprising:
a tubular graft member formed of expanded polytetrafluoroethylene having a plurality of nodes and fibrils interconnecting the nodes, and forming a microporous material matrix; and structural support means for imparting resistance to longitudinal compression or axial shrinkage of the tubular graft member by reinforcing the microporous material matrix along a longitudinal axis of the tubular graft member, the structural support means being integrated into at least a portion of the microporous material matrix of the tubular graft member and extending axially along a substantial longitudinal section of the tubular graft member.

2. The graft of Claim 1, wherein the structural support means further comprises a rib member bonded to at least one of an outer wall surface and an inner wall surface of the tubular graft member.

3. The graft of Claim 2, wherein the rib member further comprises a biocompatible plastic selected from the group consisting of polyamides, polyimides, polyesters, polypropylenes, polyethylenes, polyfluoroethylenes, polyvinylpylolidones, fluorinated polyolefins, fluorinated ethylene/propylene copolymers, tetrafluorethylene/hexafluropropylene copolymer, perfluoroalkoxy fluorocarbons, tetrafluoroethyl/perfluoro propyl vinyl ether copolymer, ethylene/tetrafluoroethylene copolymers, and polyvinylpyrrolidone.

4. The graft of Claim 1, wherein the structural support means further comprises an aqueous dispersion of a biocompatible polymer in a coating medium, the aqueous dispersion being applied to at least one of an inner wall surface and an outer wall surface of the tubular graft member.

5. The graft of Claim 1, wherein the structural support means further comprises a metal member co-extruded with the tubular graft member.

6. The graft of Claim 1, wherein the structural support means further comprises a metal member co-extruded with a polytetrafluoroethylene beading member, the polytetrafluoroethylene beading member being sintered onto the tubular graft member.

7. The graft of Claim 1, wherein the structural support means provides resistance to at least one of longitudinal compression and axial shrinkage of the tubular graft member, the compression of the graft being less than or equal to about 27 percent of the uncompressed length of the graft.

8. The graft of Claim 1, wherein the structural support means further comprises a region integral within the wall thickness of the tubular graft member.

9. A polytetrafluoroethylene graft, produced by the process comprising the stepsof:
mounting a tubular expanded polytetrafluoroethylene graft member onto a mandrel, the mandrel having a central lumen and a plurality of openings passing through the mandrel perpendicular to the central axis of the mandrel and communicating between the central lumen and an outer surface of the mandrel;
applying a structural support means for reinforcing the microporous material matrix and imparting resistance to at least one of longitudinal compression and axial shrinkage to the tubular graft member in a pattern corresponding to the openings on the mandrel, the structural support means having a fluid state;
applying a negative pressure through the central lumen of the mandrel and to the plurality of longitudinally aligned openings passing through the mandrel, thereby drawing a negative pressure through the microporous matrix of the tubular graft member; and drawing at least a portion of the structural support means, in a fluid state, into the microporous matrix of the tubular graft member from at least one of an inner and an outer surface thereof.

10. The polytetrafluoroethylene graft, produced by the process of Claim 9, wherein the step of applying a structural support means further comprises the step of bonding a rib member to at least one of an outer wall surface and an inner wall surface of the tubular graft member.

11. The polytetrafluoroethylene graft, produced by the process of Claim 10, wherein the step of applying a structural support means further comprises the step of selecting a biocompatible plastic from the group consisting of polyamides, polyimides, polyesters, polypropylenes, polyethylenes, polyfluoroethylenes, polyvinylpyrolidones, fluorinated polyolefins, fluorinated ethylene/propylene copolymers, tetrafluorethylene/hexafluropropylene copolymer, perfluoroalkoxy fluorocarbons, tetrafluoroethyl/perfluoro propyl vinyl ether copolymer, ethylene/tetrafluoroethylene copolymers, and polyvinylpyrrolidone.

12. The polytetrafluoroethylene graft, produced by the process of Claim 9, wherein the step of applying the structural support means further comprises the step of coating the tubular graft member with an aqueous dispersion of a biocompatible polymer in a coating medium, the aqueous dispersion being coated to at least one of an inner wall surface and an outer wall surface of the tubular graft member.

13. The polytetrafluoroethylene graft, produced by the process of Claim 9, wherein the step of applying the structural support means further comprises the step of co-extruding a metal member with the tubular graft member.

14. The polytetrafluoroethylene graft, produced by the process of Claim 9, wherein the step of applying the structural support means further comprises the steps of co-extruding a metal member with a polytetrafluoroethylene beading member, applying the polytetrafluoroethylene beading member to the tubular graft member and sintering the polytetrafluoroethylene beading member onto the tubular graft member.

15. The polytetrafluoroethylene graft, produced by the process of Claim 9, wherein the step of applying the structural support means further comprises the step of providing resistance to longitudinal compression and axial shirinkage of the tubular graft member being less than or equal to about 27 percent of the uncompressed length of the graft.

16. A method for making a tubular graft, comprising the steps of:
mounting a tubular expanded polytetrafluoroethylene graft member onto a mandrel, the mandrel having a central lumen and a plurality of openings passing through the mandrel disposed in a pattern upon a longitudinal extent of the mandrel and communicating between the central lumen and an outer surface of the mandrel;
applying a structural support means for reinforcing the microporous material matrix and imparting resistance to at least one of longitudinal compression and axial shrinkage to the tubular graft member in a pattern corresponding to the openings on the mandrel, the structural support means having a fluid state;
applying a negative pressure through the central lumen of the mandrel and to the plurality of openings passing through the mandrel, thereby drawing a negative pressure through the microporous matrix of the tubular graft member; and drawing at least a portion of the structural support means, in a fluid state, into the microporous matrix of the tubular graft member from an outer surface thereof.

17. The method of Claim 16, further comprising the step of mounting the mandrel and graft within a mold and injecting the structural support means into the mold and adjacent the openings in the mandrel.

18. An expanded polytetrafluoroethylene endoluminal graft, comprising:
a radially expandable tubular expanded polytetrafluoroethylene graft member characterized by a microporous material microstructure of nodes interconnected by fibrils and having a first unexpanded diameter and a second radially expanded diameter greater than the first unexpanded diameter; and a structural support member joined to the graft member, oriented substantially parallel to and extending substantially along an entire longitudinal axis of the tubular graft foreshortening of the graft member during radial expansion of the graft member from the first unexpanded diameter to the second radially expanded diameter.

19. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, further comprising a radially expandable stent member joined in intimate contact with the radially expandable tubular expanded polytetrafluoroethylene graft member.

20. The expanded polytetrafluoroethylene endoluminal graft according to Claim 19, wherein the radially expandable stent member is joined to a luminal surface of the radially expandable tubular expanded polytetrafluoroethylene graft member.

21. The expanded polytetrafluoroethylene endoluminal graft according to Claim 19, wherein the radially expandable stent member is joined to an abluminal surface of the radially expandable tubular expanded polytetrafluoroethylene graft member.

22. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member further comprises a rib member bonded to at least one of an outer wall surface and an inner wall surface of the tubular graft member.

23. The expanded polytetrafluoroethylene endoluminal graft according to Claim 22, wherein the rib member further comprises a biocompatible plastic selected from the group consisting of polyamides, polyimides, polyesters, polypropylenes, polyethylenes,polyfluoroethylenes, polyvinylpyrolidones, fluorinated polyolefins, fluorinated ethylene/propylene copolymers, tetrafluoroethylene/hexafluoropropylene copolymer, perfluoroalkoxy fluorocarbons, tetrafluoroethyl/perfluoro propyl vinyl ether copolymer, ethylene/tetrafluoroethylene copolymers, and polyvinylpyrrolidone.

24. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member further comprises an aqueous dispersion of a biocompatible polymer in a coating medium, the aqueous dispersion being applied to at least one of an inner wall surface and an outer wall surface of the tubular graft member.

25. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member further comprises a metal member co-extruded with the tubular graft member.

26. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member further comprises a metal member co-extruded with a polytetrafluoroethylene beading member, the polytetrafluoroethylene beading member being sintered onto the tubular graft member.

27. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member provides resistance to at least one of longitudinal compression and axial shrinkage of the tubular graft member, the compression of the graft being less than or equal to about 27 percent of the non-compressed length of the graft.

28. The expanded polytetrafluoroethylene endoluminal graft according to Claim 18, wherein the structural support member further comprises a region integral within the wall thickness of the tubular graft member.