US20050102022A1 - Stent-graft with rails - Google Patents

Abstract

A stent-graft with increased longitudinal flexibility that is deployed within a body lumen for supporting the lumen and repairing luminal aneurysms. In a preferred embodiment, the stent-graft is located and expanded within a blood vessel to repair aortic aneurysms. The stent-graft is comprised of an expandable stent portion, an expandable graft portion and at least one elongated rail. The stent portion and graft portion are moveable between the terminal ends of the rail(s) and relative to the rails so that it can conform to the shape of a vessel in which it is deployed. The stent-graft provides increased longitudinal flexibility within a vessel. Also, the stent-graft of the present invention does not kink after expansion, and thus, eliminates the potential for the graft portion occluding the blood flow lumen of the vessel in which it is deployed. Moreover, the wear on the graft is reduced and its longevity increased.

Description

RELATED APPLICATION
• This application claims the benefit of and incorporates by reference U.S. Provisional Patent Application No. 60/403,361 filed on Aug. 15, 2002.
FIELD OF THE INVENTION
• The present invention relates to a stent-graft for use as a prosthetic within a body lumen to support the lumen, and particularly, to a stent-graft having improved longitudinal structural flexibility and graft wear that can be used within a body to support a lumen.
BACKGROUND OF THE INVENTION
• It is generally known to insert a resiliently expandable stent into a body lumen, such as a blood vessel, to provide radial hoop support within the lumen in the treatment of atherosclerotic stenosis and other conditions. For example, it is generally known to open a blocked cardiac blood vessel by conventional methods (e.g., balloon angioplasty or laser ablation) and to keep that blood vessel open using an expandable stent.
• Stents are tubular structures formed of biocompatible materials, usually metals like stainless steel or Nitinol, which are radially expandable. The radial strength of the stent material keeps the stent and the lumen into which the stent is deployed in an open configuration. Expandable stents typically include a mesh-like surface pattern of slots or holes cut therein so that a balloon can expand the stent after the stent has been deployed into the body lumen and positioned at a predetermined location. However, these mesh-like surface patterns also permit the passage of endothelial and other cells through the openings in the stents that can cause restenosis of the vessels. For example, the mesh-like surface patterns can permit thrombus formations and plaque buildup within the vessel.
• Expandable stents have been combined with coverings of biocompatible materials to form “stent-grafts” that provide benefits in addition to those provided by conventional expandable stents. For example, the expandable stent-grafts can be used as a graft within a body lumen, such as a blood vessel. Intraluminal vascular stent-grafts can be used to repair aneurysmal vessels, particularly aortic arteries, by inserting an intraluminal vascular stent-graft within the aneurysmal vessel so that the prosthetic stent-graft support the vessel and withstand the forces within the vessel that are responsible for creating the aneurysm.
• Polytetrafluroethylene (PTFE) has been used as a material from which to fabricate blood vessel grafts or prostheses used to replace damaged or diseased vessels. This is partially because PTFE is extremely biocompatible causing little or no immunogenic reaction when placed within the human body. Additionally, in a preferred form, expanded PTFE (ePTFE) has been used. This material is light and porous and is potentially colonized by living cells becoming a permanent part of the body. The process of making ePTFE of vascular graft grade is well known.
• Enclosing a stent with ePTFE can create a vascular prosthetic that limits the amount of cellular material that can enter the stent and the blood vessel. However, such a stent-graft tends to be rather inflexible. Conventional stent-grafts tend not to conform to the natural curved shape of the blood vessel in which they are deployed. In particular, conventional stent-grafts can be longitudinally inflexible (i.e., along a length of the stent portion and the graft portion), and therefore tend to be resistant to transverse deformation. As a result, these stent-grafts may not effectively seal the intended aneurysm(s) within the blood vessel in which the stent-graft is deployed.
• Conventional stent-grafts include circumferential support members (hoops) that are securely spaced from each other and from the ends of the stent portion so that they do not experience relative axial movement. The spacing between adjacent support elements is maintained by rigid connections or bridge elements (sometimes referred to in the art as “bridges”) between adjacent support elements and at least one elongated member that extends from a first end of the stent portion to a second end of the stent portion. The circumferential support members are also secured to the graft portion of material extending along the stent portion so that the graft portion cannot move along the length of the stent portion. These secure, rigid connections prevent the support elements and the graft portion from moving longitudinally along the elongated member(s) of the stent and prevent the stent-graft from conforming to the curvature of the blood vessel in which it is deployed. The interaction of the conventional stent material and the conventional graft material, along with the large expanded diameter of a stent-graft, create conformability, performance and manufacturing issues that are in addition to those issues associated with conventional stents and discussed in copending U.S. patent application Ser. No. 10/100,986 which is hereby incorporated by reference. For example, poor longitudinal flexibility of the stent-graft can lead to kinking of the graft portion and the ultimate occlusion of the flow lumen. Additional disadvantageous of conventional stent-grafts can include graft wear on the stent portion, blood leakage through suture holes in the graft portion that receive the sutures that anchor the graft portion to the stent portion and labor intensive manufacturing processes.
• There is a need in the art for a stent-graft that is longitudinally flexible, while providing a smooth inner surface for blood flow.
SUMMARY OF THE INVENTION
• The present invention relates to a stent-graft with increased longitudinal flexibility relative to conventional stent-grafts. Longitudinal flexibility as used herein relates to the flexibility of the stent-graft structure (or portions thereof) to move relative to its major, longitudinal axis of extension. The stent-graft is deployed within a body lumen for supporting the lumen and repairing luminal aneurysms. In a preferred embodiment, the stent-graft is located and expanded within a blood vessel to repair aortic aneurysms.
• In an embodiment, the stent-graft can be comprised of an expandable stent portion, an expandable graft portion and at least one elongated rail. The stent portion and graft portion are moveable between the terminal ends of the rail(s) and relative to the rails so that the stent-graft can conform to the shape of a vessel in which it is deployed. Additionally, longitudinally adjacent circumferential support elements of the stent portion can be secured together by at least one bridging element. Alternatively, each circumferential support elements can be free of a connection to a longitudinally adjacent circumferential support element. The use of the rail(s) and the bridging elements allows the support elements to separate as needed, assume the outer radius of a vessel bend and shorten to assume an inner radius of a vessel bend. The stent-graft eliminates the poor longitudinal flexibility associated with conventional stent-grafts. As a result, the stent-graft of the present invention provides greater resistance to kinking after expansion, and thus, eliminates the potential for the graft portion occluding the blood flow lumen. Moreover, the wear on the graft is reduced and its longevity increased.
• Furthermore, according to an aspect of the present invention, the graft portion of the stent-graft is coupled to at least one longitudinal extending rail at locations spaced from the ends of the stent-graft. In one embodiment, the graft portion is coupled to the rails at the locations spaced from the ends of the stent-graft without the use of sutures that would extend through the graft portion and compromise the fluid retention integrity of the graft portion at these spaced locations. Instead, circumferential coupling members positioned about the graft portion and secured to the graft portion can receive the rails. These coupling members include circumferentially spaced openings that receive the rail(s). Alternatively, the rails extend through cauterized holes that were mechanically created in a substrate of the graft portion. Passing the rail(s) through these openings and holes reduces manufacturing costs and time. Passing the rail(s) also provides greater expanded longitudinal flexibility, prevents apices of the stent portion from protruding into the graft portion and the blood vessel and reduces wear on the material forming the graft portion. The securing of the rail(s) relative to the graft portion according to the present invention eliminates the blood leakage that is typically seen with conventional stent-grafts that employ sutures. In this or any of the embodiments discussed herein, the ends of the graft portion may be secured to the stent portion by sutures.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be even better understood with reference to the attached drawings, in which:
• FIG. 1 illustrates a stent-graft according to an embodiment of the present invention;
• FIG. 2 is an enlarged view of a portion of the stent-graft shown inFIG. 1;
• FIG. 3 illustrates a graft portion and rail receiving coupling members of the stent-graft shown inFIG. 1;
• FIG. 4 is an enlarged view of an end of the graft portion and rail receiving coupling members illustrated inFIG. 3;
• FIG. 5 is an end view of the graft portion and rail receiving coupling members shown inFIG. 3;
• FIG. 6 illustrates an opening of a rail receiving coupling member along the circumference of the stent graft;
• FIG. 7 is a side view of the rail receiving coupling members with at least two rails extending along the length of the stent-graft;
• FIG. 8 is a perspective view of the rail receiving coupling members spaced along the stent-graft with the graft portion and stent portion removed;
• FIG. 9 illustrates a portion of an alternative stent-graft embodiment according to the present invention;
• FIGS. 10 and 11 illustrate portions of an additional alternative stent-graft embodiment according to the present invention;
• FIGS. 12-15 illustrate another alternative embodiment of the stent-graft according to the present invention in which the rails are extended through cauterized openings in the graft portion;
• FIG. 16 illustrates a graft portion of a stent-graft according to another embodiment of the present invention;
• FIG. 17 illustrates a stent-graft according to the present invention including the graft portion illustrated inFIG. 16; and
• FIGS. 18-20 illustrate a vascular support member including rail receiving coupling members according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• Referring to the figures where like numerals indicate the same element throughout the views,FIG. 1 illustrates a stent-graft10 according to the present invention. The stent-graft10 includes agraft portion100 and astent portion20 with flexibleelongated rail elements50. Thestent portion20 provides support to thegraft portion100 when the stent-graft10 is deployed and located in an expanded condition within a portion of a mammalian body such as a vascular lumen.
• Thestent portion20 includes a plurality of spaced, circumferentially extending support elements (hoops)22. Eachcircumferential support element22 is generally annular in shape as shown inFIG. 1. Eachcircumferential support element22 is made from a flexible, biocompatible material (i.e., from a material that is, for example, non-reactive and/or non-irritating). In one embodiment, thestent portion20 can be formed from a tube of biocompatible material. For example, thestent portion20 can be formed by laser cutting thestent portion20 and itssupport elements22, etc. from the tube. In another embodiment, eachcircumferential support element22 is made from medical-grade metal wire formed as a closed loop (i.e., as an annular hoop) in a known manner, including, for example, micro-welding two ends of a wire segment together.
• Stainless steel, metal alloys, shape-memory alloys, super elastic alloys and polymeric materials used in conventional stents are representative examples of materials from whichcircumferential stent portion20 and itssupport elements22 can be formed. The alloys can include NiTi (Nitinol). The polymers forcircumferential support elements22 may, for example, be bioabsorbable polymers so that the stent can be absorbed into the body instead of being removed.
• In a first embodiment, illustrated inFIGS. 1 and 2, eachcircumferential support element22 has a sinusoidal or otherwise undulating form, such as a wave shape. As shown inFIGS. 1 and 2, the undulating form of thesupport elements22 includespeaks12 and troughs13 (space behind the peaks). Thetroughs13 include the open spaces between adjacent substantiallylinear struts14 that are connected to acurved member16 that forms therespective peak12. Each peak12 points in a direction that is opposite that of the immediately preceding or following, circumferentially positionedpeak12. The same is true of thetroughs13. Eachtrough13 points in a direction that is opposite the immediately preceding or following, circumferentially positioned trough.
• In the embodiment illustrated inFIGS. 1 and 2, thepeaks12 all face in the one direction, toward afirst end54 of thestent20. Similarly, thetroughs13 all face in one direction, toward asecond end56 of thestent20, which is opposite the first end. Eachcircumferential support element22 is connected to a longitudinally adjacentcircumferential support element22 by a respective bridge element24 (FIGS. 1 and 2). As shown, thebridge elements24 connect peaks of adjacent and circumferentially out-of-phase peaks12 ofadjacent support elements22. As a result,adjacent support elements22 can be rigidly spaced from each other at the area where they are joined by thebridge element24.
• In the embodiment shown inFIGS. 1 and 2, only a limited number ofbridge elements24 are provided between respectiveadjacent support elements22. For example,adjacent support elements22 may be connected to each other by between about one and threebridge elements24. In an embodiment, only onebridge element24 extends betweenadjacent support elements22. If toomany bridge elements24 are provided between adjacent support elements, the coupling between thesupport elements22 becomes similar to providing a rigid coupling between support elements, such that the desired longitudinal flexibility according to the present invention is lost. By providing only a limited number of bridge elements24 (including, without limitation, one bridge element24), the resultant assembly can still provide a good approximation of using completely independentcircumferential support elements22.
• Furthermore, the peripheral location at which bridge element(s)24 are provided between respectiveadjacent support elements22 has an effect on longitudinal flexibility. For example, if two bridge elements are provided between a respective pair ofadjacent support elements22 at diametrically opposite sides of thesupport elements22, then, generally, the longitudinal flexibility there between is at a maximum at diametrically opposite sides of thesupport elements22 located at about 90 degrees from thebridge elements24, and decreases along the circumference of thesupport elements22 in a direction approaching therespective bridge elements24.
• For the foregoing reasons, it may be useful or otherwise beneficial to provide, for example, onebridge element24 betweenadjacent support elements22, as illustrated inFIG. 1. Furthermore, it may be additionally useful to offset eachbridge element24 from a longitudinallyadjacent bridge element24 in a circumferential direction, as is also illustrated inFIG. 1. The circumferential offset can be staggered by one set ofpeaks12 along the length of thestent portion20 betweenadjacent support elements22. Alternatively, thebridge elements24 can be circumferentially offset by up to 180 degrees for adjacent pairs ofsupport elements22. The above-discussed circumferential offset embodiments provide the structural integrity benefits of using abridge element24, but distribute the resultant restriction in longitudinal flexibility so that no one transverse direction of stent deflection is overly restricted.
• In an alternative embodiment illustrated inFIG. 9-15, thecircumferential support elements22 are formed by a plurality of connected, substantially diamond shapedsupport members30. Each diamond shapedsupport member30 has a firstcircumferential peak32 and a secondcircumferential peak33 that point in opposite circumferential directions. Eachsupport member30 also includes a firstlongitudinal peak34 and a secondlongitudinal peak35 that point toward different ends of thestent portion20. Circumferentially successive diamond shapedsupport members30 are connected to each other at ajunction36 that is formed as part of thesupport element22 during the pressing or molding of thesupport elements22. Alternatively, thejunctions36 can be applied using conventional techniques such as welding, hooks or friction fitting.
• As shown inFIGS. 1 and 2, thesupport elements22 are freely mounted on flexible, elongated rail elements50 (hereinafter “rails”) such that thesupport elements22 can move along therails50. Therails50 extend along the length of the stent-graft10 between theoutermost peaks12 ofterminal support elements22 at afirst end54 and theinnermost peaks12 of theterminal support element22 at asecond end56. As illustrated, theterminal support elements22 can extend beyond the terminal ends of the graft-portion100.
• Rails50 are desirably sufficiently flexible to accommodate bends, curves, etc. in a blood vessel. In one embodiment, therails50 are free of longitudinal expansion. Also, therails50 may be made from, for example and without limitation the following biocompatible materials: metals, metallic alloys including those discussed above, glass or acrylic, and polymers including bioabsorbable polymers. Therails50 can have any form. For example, therails50 can be solid cylindrical members, such as wires or extrusions with a circular, elliptical or other known cross sections. Alternatively, therails50 can be ribbons or spring wires.
• In contrast to bridgeelements24 which are generally the same thickness and thecircumferential support element22 that they join and thus relatively inflexible, the thickness of therails50 can be designed to provide a desired degree of flexibility to a given stent-graft10. Eachrail50 can have a thickness (diameter) of about 0.001 inch to about 0.010 inch. In an embodiment, eachrail50 has a thickness of about 0.0011 inch to about 0.005 inch. In another embodiment, eachrail50 has a thickness of about 0.005 inch. Therails50 can be passed or “snaked” through thecircumferential support elements22 as discussed in copending U.S. patent application Ser. No. 10/100,986, which has been incorporated by reference. Additionally, therails50 can be passed through thestent portion20 and thegraft portion100 as discussed below.
• At least some ofrails50 may include end structures for preventing thecircumferential support elements22 from unintentionally passing beyond theends54,56 of therails50. The end structures may have several forms as illustrated in copending U.S. patent application Ser. No. 10/100,986, which has been incorporated by reference. In an example, the end structures may be mechanical protrusions or grasp structures by which the endmostcircumferential support elements22 are fixed in place relative to theends54,56 ofrails50. In yet another embodiment, the structures may also be a weld (made by, for example, a laser) for bonding a portion of an endmostcircumferential support element22 to ends54,56 ofrails50.
• As illustrated inFIG. 1, thestent portion20 can include eightrails50 that extend between theends54,56. However, it is also contemplated that any number ofrails50 up to the number ofpeaks12 along the circumference of thesupport element22 could be used. For example, if thesupport elements22 include three sets ofpeaks12, then threerails50 could be used. If the support elements included fourteen sets ofpeaks12, then up to fourteenrails50 could be used. In between thesupport elements22 at the terminal ends54,56, thesupport elements22 that are connected to each other by thebridge elements24 are free to move along the rail(s)50. These remainingsupport elements22 slide along the rail(s)50 so that thestent50 can conform to the shape of the blood vessel. It is also contemplated that theterminal support elements22 can move along therails50.
• In the embodiment illustrated inFIG. 1, thecircumferential support elements22 includeapertures17 in thecurved members16 through which therails50 extend.Apertures17 extend through thepeaks12 in a direction that is substantially parallel to the length of thestent portion20. Theseapertures17 retain and orient the supporting rail(s)50 in a direction parallel to the length of the stent-graft10. Also, in an embodiment, therails50 are completely contained within the walls (within the outer surface) of the stent-graft10 so that they do not protrude beyond the outer surface of the stent-graft10.
• Thestruts14 of thestent portion20 can have substantially any radial thickness that provides them with the needed strength to support the graft portion i00 and a blood vessel when deployed and expanded within the vessel. Eachstrut14 has a substantially low profile that will not damage the vessel as it is deployed. In one example, thestruts14 can have a radial thickness of between about 0.0001 inch and about 0.020 inch. In an embodiment, the radial thickness is about 0.002 inch to about 0.008 inch. In another embodiment, thestruts14 have a radial thickness of between about 0.004 inch and about 0.005 inch. These thicknesses provide the stent-graft10 with the needed structural and expansion properties to support thegraft100, to support the vessel in which it is deployed and the longitudinal flexibility to conform to the natural elongated shape of the vessel.
• In an embodiment, the areas of thecurved members16 are formed to have the same radial thickness as that of thestruts14 in order to accommodate theapparatus17 and the received rail(s)50. In another embodiment, the areas of thecurved members16 are formed with a greater radial thickness than thestruts14 in order to accommodate theapertures17. For example, the radial thickness of thecurved members16 can be between about 0.001 inch and about 0.006 inch greater than that of thestruts14. Theapertures17 can have a diameter of about 0.005 inch for receiving therails50. Between therails50 where expansion occurs, the thickness could be about 0.004 inch. Astent portion20 having 0.002 inchthick strut14 walls could have acurved member16 with a radial thickness of about 0.009 inch where therails50 are passed.
• In the embodiments illustrated inFIGS. 9-15 and17, therails50 extend throughapertures39 located at the first and secondlongitudinal peaks34,35 of thesupport elements22. In a first embodiment, the areas of thesupport members30 forminglongitudinal peak34 andlongitudinal peak35 and surroundingapertures39 can have the same radial thickness as that oflongitudinal struts37 extending between the peaks32-35. In an alternative embodiment, theareas surrounding apertures39 can have a greater radial thickness than that of thelongitudinal struts37. As discussed above, the radial thickness of theareas surrounding apertures39 can be between about 0.001 inch and about 0.006 inch greater than that of thestruts37. For example, a diamond shapedsupport member30 havingstruts37 with a radial thickness of about 0.002 inch could have alongitudinal peak34,35 with a radial thickness of between about 0.006 inch and about 0.009 inch.
• Eachaperture39 can have a diameter that is large enough to slidably receive arail50. The diameter of eachaperture39 can be between about 0.0014 inch and about 0.012 inch. In an embodiment, the rail receiving area has an opening of between about 0.0014 inch and 0.006 inch. However, any diameter that slidably receives arail50 could also be used.
• In alternative embodiments illustrated inFIGS. 18-20, therails50 are slidably received withinrail receiving members130 that extend from a surface of thesupport member30 forming thesupport element22. Theserail receiving members130 slidably couple arail50 to thesupport element22. As illustrated, therail receiving members130 are located proximate thelongitudinal peaks34,35 of theirrespective support member30. However, therail receiving members130 could be located at other positions along the length of theirrespective support elements22. Any of the above-discussed embodiments can includesupport elements22 having therail receiving members130.
• In a first embodiment illustrated inFIG. 18, therail receiving members130 are located proximate thelongitudinal peaks34,35 of thesupport members30. The receivingmembers130 of this embodiment include anarm137 with agroove139 that receives therail50. Thegroove139 has a bearing surface that is sized large enough to couple thesupport element22 to therail50, while still permitting movement of thesupport element22 along therail50 and relative to thegraft portion100.
• In the embodiment illustrated inFIG. 19, each receivingmember130 can include two opposingarms158 that are offset from each other along the length of thesupport member30. Likearm137, eacharm158 includes agroove159 sized to couple thesupport member30 to therail50 while permitting sliding movement of the support member andstent portion20 relative to therails50.
• In either embodiment illustrated inFIGS. 18 and 19, thearms137,158 can be formed by being punched, or otherwise mechanically formed, from a portion of itssupport member30. Alternatively, thearms137,158 could be secured to theirrespective support members30 by welding or other known connection techniques. Eacharm137,158 can be formed to extend inwardly away from itssupport member30 in the direction of thegraft portion100. In such an embodiment, thearms137,158 are not intended to contact the inner surface of the vessel into which the stent-graft10 is deployed. Alternatively, thearms137,158 of the receivingmembers130 can project outwardly away from thestent portion100 and the outer surface of theirsupport members30 that are intended to contact the inner wall of the vessel in which the stent-graft10 is deployed. As with the above-discussed embodiments, thegrooves139,159 provide rail receiving areas having openings of between about 0.0014 inch and 0.012 inch. In an embodiment, the rail receiving areas ofgrooves139,159 has an opening of between about 0.0014 inch and 0.006 inch.
• As illustrated inFIG. 20, therail receiving members130 can also include a pair of opposing, cooperatingarms163 that form agroove164 into which therail50 can be snap fitted. Thegroove164 is sized to receive therail50 such that thesupport member30 is coupled to therail50 and free to move longitudinally along therail50 as discussed above with respect to the other embodiments. Thearms163 can be formed as discussed above with respect to the embodiments illustrated inFIGS. 18 and 19. Additionally, thearms163 can extend from either the inner or outer surfaces of theirrespective support members30 as discussed above with respect to the embodiments illustrated inFIGS. 18 and 19.
• In any of the above-discussed embodiments, the illustratedgraft portion100 is formed of a well known biocompatible materials such as woven polyester including polyester terphthalate (PET, polyester, formerly available under the Dupont Trademark “Dacron”), polytetrafluroethylene (PTFE, Teflon) and fluorinated ethylene propylene (FEP, Teflon with additives for melt processing). Other polymer fabrics could be used including polypropylene, polyurethane, including porous polyurethane, and others. In an embodiment, the biocompatible material is expanded Polytetrafluroethylene (ePTFE). Methods for making ePTFE are well known in art, and are also described in U.S. Pat. No. 4,187,390 issued to Gore on Feb. 5, 1980, which is hereby incorporated herein by reference. Thegraft portion100 can be formed of either woven or a non-woven material(s).
• The porous structure of ePTFE consists of nodes interconnected by very small fibrils. The ePTFE material provides a number of advantages when used as a prosthetic vascular graft. The ePTFE is highly biocompatible, has excellent mechanical and handling characteristics, does not require preclotting with the patient's blood, heals relatively quickly following implantation, and is thromboresistant. Further, ePTFE has a microporous structure that allows natural tissue ingrowth and cell endothelialization once implanted into the vascular system. This contributes to long-term healing and graft patency.
• Thegraft portion100 can be surrounded by therails50 and thestent portion20 as illustrated inFIGS. 1-17. In the first embodiment, illustrated inFIGS. 1-8, the stent-graft10 includes a plurality of circumferentially extending, rail receivingcoupling members60 that are spaced from each other along the length of thegraft portion100. The rail receivingcoupling members60 eliminate the need to suture thestent portion20 to thegraft portion100 at locations spaced from the ends of thegraft portion100.
• Eachcoupling member60 is sized to be circumferentially and longitudinally coextensive with a portion of the outer surface of thegraft portion100. Thecoupling members60 can extend 360 degrees around the circumference of thegraft portion100 or only partially around the circumference of thegraft portion100. For example, each couplingmember60 may extend only about 270 or 180 degrees around the circumference of thegraft portion100. Thecoupling members60 expand with thestent portion20 and thegraft portion100 when the stent-graft10 is expanded within a vessel using either self-expansion or a balloon.
• Eachcoupling member60 is formed of a known material such as those discussed above relating to thegraft portion100 including PTFE, ePTFE, FEP, woven PET (DACRON), PET film, or any polymer that can be bonded to the exterior of thegraft portion100 and permits the smooth and easy passage of therails50 through their associatedpassageways62, hereinafter referred to as “openings 62”. The material for each couplingmember60 can vary depending on the material used for thegraft portion100.
• As shown inFIGS. 6 and 7, theopenings62 are formed between the inner surface of thecoupling member60 and theouter surface104 of thegraft portion100 so that theopenings62 retain their open position before and after therails50 have been passed through. Theopenings62 are equally or unequally spaced around the circumference of thecoupling members60. In an embodiment, theopenings62 are axially aligned along the length of thegraft portion100. However, in an alternative embodiment, theopenings62 ofadjacent coupling members60 can be circumferentially offset relative to each other. The number ofopenings62 circumferentially spaced about thecoupling member60 will equal the number of rails used for the stent-graft10. For example, if the stent-graft10 includes fiverails50, then each longitudinally spacedcoupling member60 could include at least fiveopenings62.
• In an embodiment, the number ofcoupling members60 will be equal to the number ofsupport elements22 that extend around thegraft portion100. As illustrated inFIG. 5, each couplingmember60 is formed of a single layer64 of material secured to the outer surface of thegraft portion100 by ultrasonic welding, adhesive bonding, thermal fusing or other known manners. In this embodiment, therails50 extend between theinner surface63 of each couplingmember60 at arespective opening62 and theouter surface104 of thegraft portion100.
• In an alternative embodiment, thecoupling member60 includes a first circumferentially extending member secured to theouter surface104 of thegraft portion100 and a second circumferentially extending member positioned over the first member. In this embodiment, theopenings62 are formed between the two circumferentially extending members.
• In any of the above embodiments relating toFIGS. 1-8, thecoupling members60 are secured to thegraft portion100 and thestent portion20 while receiving therails50 so that thecoupling members60 can move along and relative to therails50. Thecoupling members60 can be secured to thesupport elements22 by welding or other known conventional securing techniques. In an alternative embodiment, thecoupling members60 can extend through slots in thesupport elements22 or they can be adhesively secured in recesses formed on the inner surfaces of thesupport elements22.
• In the alternative embodiment illustrated inFIGS. 9-11, thecoupling members60 can be positioned along the length of the stent-graft10 and oriented so that theiropenings62 are circumferentially offset from theopenings62 of longitudinally adjacent coupling member(s)66,68. As shown inFIG. 9,coupling member66 can haveopenings62 that are positioned within the openings in circumferentially spacedsupport members30 so that arespective rail50 passes through theopening62 in thecoupling member60 at point A that is between thelongitudinal peaks34,35 of thesupport members30. Thecoupling member60 then passes under the circumferentially adjacent rail(s)50 that extends through the immediately, circumferentially adjacent support member(s)30 (SeeFIG. 9). Theopenings62 of the immediately, longitudinallyadjacent coupling member68 are circumferentially offset from those of couplingmember66 so that therail50 passes through theopenings62 of theadjacent coupling member68 at point B. As a result, immediately, longitudinally adjacent coupling members60 (66,68) slidably receive circumferentially spacedrails50 at offset points. This can increase the stability of the stent-graft10 without reducing its ability to conform to the shape of the vessel in which it is deployed.
• In an alternative embodiment, shown inFIGS. 10 and 11, the longitudinally spacedcoupling members60 receive therails50 outside thesupport members30 at point B. In this embodiment, theopenings62 of longitudinallyadjacent coupling members60 are circumferentially and longitudinally aligned.
• In the embodiments illustrated inFIGS. 12-15, therails50 could extend through cauterized openings in thegraft portion100 in place of using thecoupling members60. Hence, in these alternative embodiments, immediately, circumferentiallyadjacent rails50 could be extended through cauterizedopenings80 in thegraft portion100 at longitudinally and/or circumferentially offset points (A, B) as shown inFIGS. 9 and 12. Alternatively, theadjacent rails50 could be extended through cauterizedopenings80 thegraft portion100 at circumferentially and/or longitudinally aligned locations B, as shown inFIG. 14. In any of the above-discussed embodiments, thegraft portion100 will move withsupport elements22 as thesupport elements22 move along therails50.
• In the embodiment illustrated inFIGS. 16 and 17, therails50 pass through circumferentially extendingretainer coupling members200, hereinafter referred to as “loops 200”. Unlike couplingmembers60 shown inFIG. 9, theloops200 haveinterior regions202 that pass throughopenings195 in thegraft portion100 and extend along an inner surface of thegraft portion100. Theopenings195 can be welded, cauterized or otherwise closed about theloops200 using other known techniques. In an embodiment, theloops200 can be formed of yam that is stronger than thegraft portion100. In an embodiment, theloops200 are formed of a PET,80 denier loop yam. Theloops200 can also be formed of any of the materials discussed above with respect to thegraft portion100. Theloops200 can also be formed of a solid polymer fiber, braid, film, or the like. It is also possible to bond or otherwise secure theloops200 to thegraft portion100.
• Portions of theloops200 on the exterior of thegraft portion100 and in-between theinterior regions202form arches210 along the outer surface of thegraft portion100. Thearches210 slidably receive therails50 so that thegraft portion100 can move along therails50 and relative to thesupport elements22. Whilerounded arches210 are illustrated, any shaped opening that slidably receives therails50 can be used. For example, the opening of thearches210 can include a rectangular, elliptical or triangular shape. Thearches210 each include an opening sized to receive therails50. These opening can be between about 0.0014 inch and about 0.012 inch. In an embodiment, the arch openings can be between about 0.0014 inch and about 0.006 inch. In an embodiment, the arch openings can be about 0.005 inch.
• Each arch210 is spaced from circumferentially spacedarches210 by a distance that is substantially equal to the circumferential spacing of the adjacent rails50. Theadjacent arches210 can be equally spaced from each other around the circumference of thegraft portion100. Alternatively,adjacent arches210 can be circumferentially spaced at different intervals around the circumference of thegraft portion100 to provide different flexion capabilities to thestent graft10. Each arch210 can be spaced from anadjacent arch210 by a distance of about 0.10 inch to about 0.30 inch. In one embodiment,adjacent arches210 are spaced from each other by a distance of about 0.155 inch.
• Thesupport elements22 comprise the diamond shapedsupport members30 shown inFIGS. 9 and 17. However, as with the above-discussed embodiments, other known shapes may also be used. Similar to the embodiments illustrated inFIGS. 9-15, thesupport elements22 shown inFIG. 17 includeapertures39 and are free of a connection to theloops200. The support elements22 (FIG.17) are moveable along therails50 in a direction that is substantially parallel to the length of thegraft portion100 as discussed above.
• The movement of thesupport elements22 along the length of the stent-graft10 and relative to therails50 andgraft portion100 can be limited by one or both of thelongitudinal peaks34,35 abutting against asupport element200. As shown inFIG. 17, thearches210 of theloops200 can act as a stop for the longitudinal movement of thesupport element22. Therefore, the total distance that thesupport elements22 move along therails50 can be controlled and limited by the spacing between theloops200 along the length of thegraft portion100. In one embodiment, eachloop200 can be spaced fromadjacent loops200 along the length of thegraft portion100 by the same distance as thecoupling members60 so that thesupport elements22 can move a distance that permits the stent-graft10 to conform to the shape of the vessel in which the stent-graft10 is deployed. The spacing between adjacent loops200 (and60) can be less than the distance that eachsupport element22 extends in a direction parallel to the length of the stent-graft10.
• Unlike the other embodiments (for example the embodiment illustrated inFIG. 1), eachsupport elements22 illustrated inFIG. 17 is free of a connection to a longitudinallyadjacent support element22 by a bridging element. As a result, thesupport elements22, illustrated inFIG. 17, can move independently relative to each other along the length of thegraft portion100. Also, like the embodiments discussed above, therails50 can include a single, continuous member with multiple turns (FIG. 17), a plurality of separate members with at least one turn that are circumferentially spaced from adjacent members around thegraft portion100, or separate, individual members that are free of turns and that are free of a direct, secured attachment to anadjacent rail50. As used herein, the term “rail” includes each of these arrangements.
• In another alternative embodiment, thegraft portion100 can include integral, spaced areas that receive therails50 formed of the material used to form thegraft portion100. These spaced areas have an increased thickness with respect to the remainder of thegraft portion100.
• The present invention also includes introducing an agent, including those set forth in U.S. patent application Ser. No. 60/426,366, which is hereby incorporated by reference, into a body using the above-discussed stent-graft10. In a preferred embodiment, the agent(s) is carried by one or more of therails50 or thegraft portion100 and released within the body over a predetermined period of time. For example, these stents can deliver one or more known agents, including therapeutic and pharmaceutical drugs, at a site of contact with a portion of the vasculature system or when released from a carrier as is known. These agents can include any known therapeutic drugs, antiplatelet agents, anticoagulant agents, antimicrobial agents, antimetabolic agents and proteins. These agents can also include any of those disclosed in U.S. Pat. No. 6,153,252 to Hossainy et al. and U.S. Pat. No. 5,833,651 to Donovan et al., both of which are hereby incorporated by reference in their entirety. Local delivery of these agents is advantageous in that their effective local concentration is much higher when delivered by the stent than that normally achieved by systemic administration.
• Therails50, which have a relatively low elastic modulus (i.e. low force to elastic deformation) in their transverse direction, may carry one or more of the above-referenced agents for applying to a vessel as the vessel moves into contact with the agent carrying rail(s)50 after deployment of the stent-graft10 within the vessel. These agents can be applied using a known method such as dipping, spraying, impregnation or any other technique described in the above-mentioned patents and patent applications that have been incorporated by reference. Applying the agents to therails50 avoids the stresses at focal areas as seen in the struts of traditional stents. In this manner drug coatings applied to the stent rails50 may be used with support elements formed of materials that are otherwise unsuitable for coating.
• It is contemplated that the various elements of the present invention can be combined with each other to provide the desired flexibility. For example, therails50 can be formed of one or more radiopaque materials. Additionally, the support element designs can be altered and various support element designs that permit the passage of the rails could be used. Similarly, the number, shape, composition and spacing of the rail elements can be altered to provide the stent with different properties. Additionally, the device can have varying numbers and placement of the bridge elements. The properties of any individual stent would be a function of the design, composition and spacing of the support elements, rails and bridge elements.
• Thus, while there have been shown and described and pointed out fundamental novel features of the present invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, and in the method illustrated and described, may be made by those skilled in the art without departing from the spirit of the invention as broadly disclosed herein.

Claims (1)

1. A stent-graft comprising:

an elongated stent portion extending about an axis;

a graft portion being at least partially coextensive with said stent portion; and

at least one rail element extending along a length of said stent-graft, each rail element being movably coupled to said stent portion and/or said graft portion such that at least a portion of said stent portion and said graft portion are freely movable along a portion and relative to each rail element.

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