US20030114918A1 - Stent graft assembly and method - Google Patents

Abstract

A method for assembling a stent graft onto a balloon delivery catheter is disclosed. The method includes the steps of: assembling a graft over a stent with attached security rings and inserting the ends of the graft between the stent and the rings; placing the assembled stent graft on the delivery balloon of the delivery catheter; and crimping the stent graft onto the balloon. The stent may include a plurality of axially aligned belts that include a plurality of mid belts, and first and second end belts, where each of the mid belts includes a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements, and each of the first and second end belts includes at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements. Also disclosed is a stent graft for use in practicing the method.

Description

• This application is a continuation-in-part of U.S. application Ser. No. 09/560,427 filed Apr. 28, 2000, which is incorporated by reference herein in its entirety.[0001]
FIELD OF THE INVENTION
• The present invention relates to a stent graft assembly and method, and more particularly to a stent graft assembly which includes security rings.[0002]
BACKGROUND OF THE INVENTION
• A composite expandable device with polymeric covering and bioactive coating thereon, delivery apparatus and method are disclosed in U.S. Pat. No. 6,371,980, issued Apr. 16, 2002. In connection with the expandable stent and the polymeric covering forming a graft carried thereby it has been found that it may be possible for the graft to move or become dislodged from its most desirable position on the stent. There is therefore a need for a new and improved stent graft assembly and method which overcomes this possible difficulty.[0003]
SUMMARY OF THE INVENTION
• In one aspect, the invention includes a stent graft that includes a stent and a graft in the form of a polymeric sleeve extending over at least a portion of the stent. Security rings are attached on opposite ends of the stent graft to prevent inadvertent displacement of the graft with respect to the stent during deployment of the stent graft into a vessel in a patient. In another embodiment, the security rings can readily accommodate expansion of the stent graft. One or both of the security rings may be attached to the stent with a weld. Preferably, the weld is a laser weld.[0004]
• In one embodiment, the stent includes a plurality of axially aligned belts which include a plurality of mid belts, and first and second end belts. Each of the mid belts includes a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements. Each of said first and second end belts includes at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements compared to the number of the struts in the mid belts.[0005]
• In another embodiment, the first and second sinusoidal-shaped elements have hinge points, and the second sinusoidal-shaped elements have narrower hinge points relative to the hinge points of the first sinusoidal-shaped elements.[0006]
• The graft may be formed of ePTFE. In one embodiment of the invention, the graft includes a bioactive coating that is disposed on the graft.[0007]
• One or more of the security rings of the invention may include a radiopaque marker carried thereon. In one embodiment, one or both of the security rings includes an eyelet and the radiopaque material is disposed in the eyelet.[0008]
• Another aspect of the invention includes a method for assembling a stent graft onto a balloon delivery catheter. The method includes the steps of: assembling a graft over a stent with attached security rings and inserting the ends of the graft between the stent and the rings; placing the assembled stent graft on the delivery balloon of the delivery catheter; and crimping the stent graft onto the balloon. One or both of the security rings may be attached to the stent with a weld. Preferably, the weld is a laser weld.[0009]
• In one embodiment of the method of the invention, the stent includes a plurality of axially aligned belts which include a plurality of mid belts, and first and second end belts. Each of the mid belts includes a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements. Each of said first and second end belts includes at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements compared to the number of the struts in the mid belts.[0010]
• In another embodiment, the first and second sinusoidal-shaped elements have hinge points, and the second sinusoidal-shaped elements have narrower hinge points relative to the hinge points of the first sinusoidal-shaped elements.[0011]
• The graft may be formed of ePTFE. In one embodiment of the invention, the graft includes a bioactive coating that is disposed on the graft.[0012]
• One or more of the security rings of the invention may includes a radiopaque marker carried thereon. In one embodiment, one or both of the security rings includes an eyelet and the radiopaque material is disposed in the eyelet.[0013]
• Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.[0014]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a side elevational view of a stent graft assembly incorporating the present invention mounted on the distal extremity of a balloon delivery catheter;[0015]
• FIG. 2 is a side elevational view of another embodiment of a stent graft assembly incorporating the present invention also mounted on the distal extremity of a balloon delivery catheter;[0016]
• FIG. 3 is a cross-sectional view taken along the line[0017]3-3 of FIG. 2;
• FIG. 4 is a view similar to FIG. 3 showing an alternate embodiment;[0018]
• FIG. 5 is a side elevational view of a stent graft assembly with a certain portion of the stent graft being removed and showing the use of different types of security rings;[0019]
• FIG. 6 is an enlarged view of one of the security rings shown in FIG. 5;[0020]
• FIG. 7 is a view of a balloon with the stent graft with security rings mounted thereon according to one embodiment of the invention;[0021]
• FIG. 8 is a detailed view of the stent graft with security rings;[0022]
• FIG. 9 is a plan view of a stent which has been split apart longitudinally and spread out to show its construction; and[0023]
• FIG. 10 is an enlarged view of a portion of the stent shown in FIG. 9.[0024]
DETAILED DESCRIPTION OF THE INVENTION
• In general, the stent graft assembly incorporating the present invention is for use in placing a stent graft in a vessel of a patient and comprises a balloon delivery catheter having a distal extremity and having an inflatable balloon on the distal extremity. A stent graft is disposed over the inflatable balloon and is comprised of a stent and an outer polymeric sleeve, the sleeve having first and second ends. First and second expandable security rings are disposed over the first and second ends of the graft and serve to secure the first and second ends of the graft to the stent to prevent inadvertent displacement of the sleeve with respect to the stent during deployment of the stent graft into the vessel of the patient.[0025]
• More particularly as shown in FIG. 1 of the drawings, the[0026]stent graft assembly10 includes astent graft11 which consists of astent12 which is covered by apolymeric sleeve13. As shown in FIG. 1, thestent graft11 is disposed over aninflatable balloon16 on the distal extremity of aballoon delivery catheter17 of a conventional type and forming a part of theassembly10. Theballoon delivery catheter17 includes amulti-lumen shaft18 which incorporates a balloon inflation lumen (not shown) and may incorporate a guide wire lumen (not shown).
• The[0027]balloon delivery catheter17 and thestent graft11 consisting ofstent12 and thepolymeric sleeve13 are disclosed in U.S. Pat. No. 6,371,980, issued Apr. 16, 2002, which is incorporated by reference herein in its entirety, and therefore will not be described in detail. As disclosed therein, thestent12 is in the form of an expandable frame and consists of a plurality of axially spaced-apartcircular belts21 which are interconnected bysinusoidal interconnector22. Eachbelt21 is comprised of a plurality of circumferentially spaced-apart elongate struts24. Sinusoidal-shaped elements26 and27 adjoin the ends of the struts24 and form in conjunction therewith thecircular belts21. The sinusoidal-shaped interconnectors22 provided for interconnecting thebelts21 are at circumferentially spaced-apart positions to provide astent12 which when expanded is capable of providing circumferential support while at the same time being axially flexible.
• The[0028]stent12 is typically formed of a suitable metal such as stainless steel, titanium and other metals and alloys thereof. It is desirable that the material utilized for the frame be biocompatible with the fluids and tissue of the human body.
• The[0029]sleeve13 is in the form of a tubular member of a size so that it can slip over thestent12 when it is in an unexpanded condition and preferably has a length so that the extreme ends of thestent12 extend beyond the sleeve as shown in FIG. 1. Thesleeve13 is typically formed of a polymeric material such as ePTFE.
• In order to ensure that the[0030]polymeric sleeve13 remains in the desired position on thestent12,security rings36 and37 have been positioned over the outer ends of thesleeve13. The security rings36 and37 typically can be formed of a metal and preferably the same metal which is used for thestent12, for example, stainless steel or titanium or alloys thereof. Therings36 and37 have sinusoidal-shapedconvolutions38 so that they can be expanded with the stent graft when the stent graft is expanded as hereinafter described. By way of example, the security rings can be formed from laser cut tubing in the same manner as stents having a suitable wall thickness of 0.003″ to 0.006″. The inner surfaces of the security rings can be left unpolished so that they have a rougher inner surface finish to enhance gripping to the outer surface of thesleeve13. Alternatively, a texture can be applied to the inner surface to enhance the gripping capabilities of the security ring.
• A[0031]radiopaque marker41 is carried by at least one and, if desired, both of the security rings36 and37, as in FIGS. 1 and 2. Thus, as shown, aradiopaque marker41 is provided on thesecurity ring37 and can be of a suitable radiopaque material such as gold which has been cold worked or forged into aneyelet receptacle42 formed as a part of theconvolutions38. Alternately, as shown in FIGS. 8 and 9, theradiopaque marker148 is provided on either or both ends of the stent140 in asimilar eyelet receptacle150.
• In use of the[0032]stent graft assembly10 and thestent graft11 of the present invention with the method of the present invention, thestent12 can be placed upon a support mandrel (not shown) after which thesleeve13 is slipped onto the stent to provide thestent graft11. Thestent graft11 is then placed on theballoon16 of theballoon delivery catheter17. Thestent graft11 is then crimped onto theballoon16 with a crimping tool (not shown). The security rings36 and37 are then placed over thesleeve13 and crimped onto the ends of thesleeve13 by a crimping tool to ensure that the security rings36 and37 remain in place on the ends of thesleeve13 and also to ensure that the ends of thegraft11 frictionally engage thestent12 to retain thesleeve13 in the desired position on thestent12. Alternatively, the security rings36 and37 and thestent graft11 can be crimped simultaneously.
• The[0033]stent graft assembly10 shown in FIG. 1 can now be utilized for positioning thestent graft11 in a vessel of a patient in a conventional manner as for example by introducing the same through a femoral artery. The advancement of thestent graft11 can be ascertained by observing the positioning of theradiopaque marker41 and also by any radiopaque markers on thestent12 and theballoon catheter17. During advancement of the stent graft to the desired site, the security rings36 and37 serve to ensure that thesleeve13 will not accidentally become dislodged or shifted in position on thestent12. After the stent graft has been delivered to the desired position in the vessel of the patient, theballoon16 of theballoon delivery catheter17 can be expanded to expand thestent12 and thesleeve13 carried thereby as well as the security rings36 and37.
• After the[0034]stent graft11 has been delivered and then expanded the desired amount, theballoon16 of theballoon delivery catheter17 can be deflated and theballoon delivery catheter17 removed in a conventional manner. Thestent graft11 will remain in place. Its position can be ascertained by observing the position of theradiopaque marker41.
• Another embodiment of a stent graft assembly incorporating the present invention is shown in the[0035]stent graft assembly61 in FIG. 2. Theballoon delivery catheter62 shown therein shows the use ofradiopaque marker bands63 and64 positioned on ashaft66 on opposite ends of theballoon67 and held in place by suitable means such as an epoxy68 and disposed on opposite ends of thestent graft11 and serve as enlargements to prevent the inadvertent dislodgement of the stent and/or the graft from the balloon during deployment of thestent graft11.
• In addition, as in the previous embodiments, security rings[0036]71 and72 are provided on opposite ends of thestent12 and thesleeve13. Security rings71 and72 are each comprised of twoelongate elements76 and77 in the forms of waves or convolutions which are sinusoidal in shape and which are joined together by circumferentially spaced-apart axially extendingstruts78 and eyelets79. As with the security rings36 and37, it can be seen that the security rings71 and72 can be readily crimped into place and expanded in the same manner as the security rings36 and37. Theeyelets79 carryradiopaque markers81. As with the security rings36 and37 the inner surfaces of theelements76 and77 can be left unpolished or with a textured surface for frictionally engaging the outer surface of thepolymeric sleeve13.
• In order to further enhance the engagement between the[0037]polymeric sleeve13 on thestent12, theradiopaque marker81 as shown in FIG. 3 can protrude out of theeyelet79 so that it can form anindentation82 with thesleeve13 which extends into an open space in thestent12 to further ensure a good engagement between thesleeve13 and thestent12 to prevent dislodgement of thesleeve13 andring71 or72 from thestent12. In a similar manner as shown in FIG. 4, aneyelet86 provided on thestent12 may also carry aradiopaque marker87 protruding radially and forming anindentation88 in the inner surface of thesleeve13 and to extend into a space in thesecurity ring72 to further ensure good engagement between thesleeve13 and thestent12.
• Operation and use of the[0038]stent graft assembly61 shown in FIG. 2 is very similar to that hereinbefore described with respect to FIG. 1 with the principal difference being that the security rings71 and72 have enhanced friction engaging capabilities over the security rings36 and37 shown in FIG. 1. In addition, theballoon delivery catheter62, by providing themarker bands63 and64 on opposite extremities of thestent graft11 also ensure that thestent graft11 cannot accidentally become dislodged during deployment of thestent graft11.
• Still another embodiment of a stent graft assembly incorporating the present invention is shown in FIG. 5 in which the[0039]balloon delivery catheter62 as shown therein is similar to the one hereinbefore described. Thestent graft11 is also similar to those hereinbefore described. However, in FIG. 5 there is shown the use of security rings91 or92 (showing two different designs) mounted on opposite ends of thesleeve13. Thesecurity ring91 is in the form of a stretchable polymer which can be stretched and fitted over one end of thesleeve13 to frictionally retain thesecurity ring91 on thesleeve13 and similarly to retain thesleeve13 on thestent12. Alternatively, as shown with thesecurity ring92, a less stretchable band of polymeric material can be utilized which is provided with circumferentially spaced-apartcutouts93 therein which as shown in detail in FIG. 6 are positioned in such a manner so as to provide weakenedregions94 associated with each of thecutouts93 but being staggered or provided on opposite sides of thesecurity ring92 so that when thestent graft11 is expanded, these weakened regions will or can break apart to provide a zig-zag shape or a substantially sinusoidal wave-like shape for the expandedsecurity ring92. Thus, it can be seen that a polymeric security ring can be provided which firmly secures the graft to the stent while still permitting expansion of the stent and graft after thestent graft assembly11 has been deployed to the desired position.
• As shown in FIG. 7, the[0040]stent graft100 is shown mounted on adelivery apparatus102. Theapparatus102 is provided with a central lumen103 which is adapted to receive a conventional guide wire. The lumen103 extends through theapparatus102 and an opening (not shown) is provided in the apparatus for expanding the apparatus. Theapparatus102 has a substantially continuous diameter and is provided with distal andproximal portions104 and106 and an intermediate portion107 which serves as a working portion of the apparatus, having a length which will accept the length of thestent graft100.Radiopaque marker bands110 and111 are provided on the portion of the central lumen103 extending through the apparatus and are mounted in the distal andproximal portions104 and106 as shown adjacent to theintermediate portion102.
• As illustrated in FIG. 10, the[0041]stent160 includes a plurality of serially-connectedbelts162 which are axially aligned with each other and are interconnected bysinusoidal interconnector164. Eachbelt162 includes a plurality of circumferentially spaced-apart elongate struts166. Sinusoidal-shapedelements168 and169 adjoin the ends of thestruts166 and form in conjunction therewith thecircular belts162. The sinusoidal-shapedinterconnectors164 provided for interconnecting thebelts162 are at circumferentially spaced-apart positions to provide astent160.Stent160 is capable of providing circumferential support while, at the same time, being axially flexible. The stent may be formed by forming the desired pattern directly out of a tube, e.g. by laser cutting or chemical etching. Alternatively, the desired pattern may be formed out of a flat sheet, e.g. by laser cutting or chemical etching, and then rolling that flat sheet into a tube and joining the edges, e.g. by welding. Any other suitable manufacturing method known in the art may be employed for manufacturing a stent in accordance with the invention. Furthermore, stents may be formed by etching a pattern into a material or mold and depositing stent material in the pattern, such as by chemical vapor deposition or the like. Such stents may be formed of plastic, metal or other materials and may exhibit a multitude of configurations. The metals from which such stents are formed may include stainless steels, titanium, Nitinol, and tantalum among others.
• In one embodiment,[0042]stent160 includes serially-connectedbelts162, and twoend belts170 and172. All belts are connected withserpentine interconnectors164. Eachend belt170 and172 includes a plurality of circumferentially spaced-apart elongate struts176.Belts162 also include spaced-apart elongate struts166.Serpentine interconnecting elements164 are provided for interconnecting the plurality ofbelts162 and theend belts170 and172 so that thebelts162 and endbelts170 and172 extend along an axis while permitting axial bending between thebelts162 and theend belts170 and172. Thus, with the construction shown in FIG. 10 there are provided fivebelts162 and twoend portions170 and172 with six sets of interconnectingelements164. The number of belts and interconnecting elements may vary depending on the desired length of the stent graft.
• As described above, a[0043]polymer sleeve142 extends over substantially the entire length of thestent160. With reference to FIG. 10, there are twice asmany struts176 inend belts170 and172 as there arestruts166 inbelts162. The larger number ofstruts176 inend belts170 and172 provides more circumferential support for the ends of the polymer sleeve (not shown), without causing unduly high radial strength at the ends of the stent graft. This has the advantage of preventing prolapse of the sleeve into the lumen of the stent graft due to blood flow after the stent graft is implanted into the vessel.
• In addition, security rings[0044]144 and146 are provided on opposite ends of thestent160 and thesleeve142. The security rings144 and146 typically can be formed of a metal and preferably the same metal which is used for thestent160, as for example stainless steel or titanium or alloys thereof. The security rings144 and146 have sinusoidal-shaped convolutions so that they can be expanded with the stent graft when the stent graft is expanded. Aradiopaque marker148 may be carried by at least one, and if desired both, of the security rings144 and146. Alternatively, as shown in FIG. 9, aradiopaque marker148 is provided on both ends of thestent160 and is of a suitable radiopaque material which has been cold worked, forged into or deposited on aneyelet receptacle150 formed as a part of the convolutions. Examples of materials which can be employed as radiopaque materials include, but are not limited to, iodine and its salts or compounds, barium and its salts or compounds, tungsten, rhenium, osmium, noble metals, palladium, gold, colloidal gold, silver, platinum, tantalum, iridium or their alloys. Preferably, the radiopaque material is gold, platinum, iridium, titanium, tantalum, or alloys. Such materials are highly visible by fluoroscopy even at very minimal thicknesses.
• The security rings[0045]144 and146 may be attached to the stent140 by any suitable attachment mechanism to ensure that the security rings144 and146 remain in place on the ends of the stent graft. This includes, but is not limited to, suture attachment methods, e.g. where a suture going around one or more struts of the stent is attached to a security ring. Apart from suturing techniques, methods including adhesives also may be used. One can solder or braze the stent and security ring together. Preferably, the security rings144 and146 are welded to stent140 at one or more weld points152,153,154. One advantage of welding the security rings to the stent is to improve the mechanical integrity of the stent graft system. The welding connections may be created by welding techniques using welding technologies such as tungsten inert gas (tig) welds, metal inert gas (mig) welds, laser welds, friction welds, and electron beam welds. Other materials known to accelerate the welding process and improve the strength between the welded elements can be added. Electropolishing may be used to remove processing impurities and form a smooth surface following attachment of the stent to the security rings.
• In one embodiment, the stent graft is positioned in a vessel of a patient and the ends of the stent graft are opened first, and then the middle of the stent graft is opened. This method maximizes the ability of the stent graft to capture potential debris material from an underlying stenosis in the vessel. With reference to FIGS. 10 and 11, the hinge points[0046]201,202,203 and204 ofend belt170 are narrower than the hinge points210,211, and212 ofbelt162. This feature provides the advantage of requiring less force to open theend belts170 and172 thanbelts162.
• The stent design and functionality in the embodiments described above is not limited to a balloon-expandable stent, but may be employed with the so-called self-expanding stents that are formed for example from shape memory materials such as Nitinol.[0047]
• From the foregoing it can be seen that there has been provided a stent graft assembly and method which makes it possible to ensure that the graft is maintained in the desired position on the stent at all times and particularly during deployment of the stent graft while readily accommodating expansion of the stent graft after the stent graft has been deployed into the desired position. It also can be seen that use of the security rings serves to prevent inadvertent movement of the graft with respect to the stent or separation of the graft from the stent.[0048]

Claims (18)

It is claimed:

1. A stent graft, comprising

a stent and a graft in the form of a polymeric sleeve extending over at least a portion of the stent, and

security rings attached on opposite ends of the stent graft to prevent inadvertent displacement of the graft with respect to the stent during deployment of the stent graft into a vessel in a patient.

2. The stent graft ofclaim 1, wherein said stent comprises

a plurality of axially aligned belts comprising a plurality of mid belts, and first and second end belts;

where each of said mid belts comprises a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements, and each of said first and second end belts comprise at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements compared to the number of said struts in said mid belts.

3. The stent graft ofclaim 2, wherein the first and second sinusoidal-shaped elements have hinge points, and the second sinusoidal-shaped elements have narrower hinge points relative to the hinge points of the first sinusoidal-shaped elements.

4. The stent graft ofclaim 1, wherein said attachment is a weld.

5. The stent graft ofclaim 4, wherein said weld is a laser weld.

6. The stent graft ofclaim 1, wherein the graft is ePTFE.

7. The stent graft ofclaim 1, wherein the graft further includes a bioactive coating thereon.

8. The stent graft ofclaim 1, wherein one or both of the security rings further includes a radiopaque marker carried thereon.

9. The stent graft ofclaim 8, wherein one or both of the security rings includes an eyelet and wherein the radiopaque material is disposed in the eyelet.

10. A method for assembling a stent graft onto a balloon delivery catheter, comprising:

assembling a graft over a stent with attached security rings and inserting the ends of the graft between the stent and the rings;

placing the assembled stent graft on the delivery balloon of the delivery catheter; and

crimping the stent graft onto the balloon.

11. The method ofclaim 10, wherein said stent comprises

a plurality of axially aligned belts comprising a plurality of mid belts, and first and second end belts;

where each of said mid belts comprises a plurality of circumferentially spaced struts having first and second ends adjoining first sinusoidal-shaped elements, and each of said first and second end belts comprise at least about twice the number of circumferentially spaced struts adjoining second sinusoidal-shaped elements compared to the number of said struts in said mid belts.

12. The method ofclaim 11, wherein the first and second sinusoidal-shaped elements have hinge points, and the second sinusoidal-shaped elements have narrower hinge points relative to the hinge points of the first sinusoidal-shaped elements.

13. The method ofclaim 10, wherein said attachment is a weld.

14. The method ofclaim 13, wherein said weld is a laser weld.

15. The method ofclaim 10, wherein said graft is ePTFE.

16. The method ofclaim 10, wherein the graft further includes a bioactive coating thereon.

17. The method ofclaim 10, wherein one or both of the security rings further includes a radiopaque marker carried thereon.

18. The method ofclaim 17, wherein one or both of the security rings includes an eyelet and wherein the radiopaque material is disposed in the eyelet.

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