Stent With Reduced Weld Profiles and a Closed-End Wire Configuration
A method for making an implantable stent includes the steps of (i) providing a plurality of elongate stent wires; (ii) forming said wires into a hollow tubular structure having opposed first and second open ends; (iii) terminating said wires at the second end; (iv) aligning the wires at the second end into a plurality of mated adjacent wires to define a plurality of abutting regions; (v) welding the mated adjacent wires to one and the other at the abutting regions to define a plurality of welds; and optionally (vi) chemically or electro-chemically removing a portion of the welds. The method may further include the steps of (a) extending at least one of the mated stent wires to provide an extended stent wire; (b) looping the extended stent wire so the extended end abuts a proximal pair of stent wires; and (c) welding the extended and looped wire to the proximal pair of wires. The step of looping may include the forming of the wire into a equilaterally arched loop having an apex, but not having other sharp bends.
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This application is a continuation of U.S. application Ser. No. 10/845844 filed May 14, 2004, the contents of which is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to stents having welded portions and atraumatic looped ends. The present invention also relates to such stents having their welded portions electro-chemically polished to reduce their profile and/or having a suture loop threaded at one or both extremities and/or being manufactured with a wire having a radiopaque core, and/or being fully or partially covered with a polymer such as silicone.
BACKGROUND OF THE INVENTIONStents made from interconnecting, often braiding, elongate wires may be made less traumatic, i.e., atraumatic, by closing the loose wire ends at the ends of the stents. The loose wire ends have typically been closed by mechanical means, such as by clamps, for example clamped microtubes, or by welding. Such mechanical means, however, provide regions of high profile as compared to the other regions of the stents, see e.g., U.S. Pat. No. 6,083,257. The high profile regions are undesirable, often leading to deployment concerns, including higher deployment forces.
Electropolishing or electro-chemical polishing of laser cut nitinol stents to improve surface finishes has been previously mentioned, see e.g. U.S. Pat. No. 6,325,825 B1 and U.S. Patent Application Publication No. 2003/0024534 A1. Further, electro-polishing or electrochemical polishing services are available, see e.g. from Admedes Schuessler GmbH. Such polishing, however, has not been attempted to alleviate the above-discussed deployment concerns.
The present invention provides a stent made from elongate wires in a closed-end design while avoiding the disadvantages of the prior art. More particularly, the present invention is directed to certain advantageous closed-end stent loop designs having reduced profiles to lower deployment forces and ease deployment of the stent.
SUMMARY OF THE INVENTIONIn one aspect of the present invention is a method for making an implantable stent. The method comprises the steps of (i) providing a plurality of elongate stent wires; (ii) forming the wires into a hollow tubular structure having opposed first and second open ends; (iii) terminating the wires at the second end; (iv) aligning the wires at the second end into a plurality of mated adjacent wires to define a plurality of abutting regions; (v) welding the mated adjacent wires to one and the other at the abutting regions to define a plurality of welds; and, optionally, (vi) chemically or electro-chemically removing a portion of the welding material from the plurality of welds. Desirably, the mated adjacent wires are substantially parallel to one and the other at the abutting regions.
In this aspect of the present invention, the step of welding may include the step of providing an inert gas proximal to the weld areas. Further, the step of welding includes laser welding, electron beam welding, resistance welding, tungsten inert gas welding, metal inert gas welding, and combinations thereof.
Desirably, the step of forming the tubular structure comprises braiding the wires, winding the wires, knitting the wires, and combinations thereof, preferably braiding the wires. The material of the wires and the material of the welds may be the same type of material.
Further, the stent wire may include a radiopaque material.
The step of chemically or electro-chemically removing the portion of the welding material may include chemical polishing or etching, chemical deburring, electrochemical polishing or etching, jet-electropolishing and combinations thereof. The step of electro-chemically removing the portion of the welding material further includes the step of providing an electrolyte, where the electrolyte is selected from the group consisting of NaClO3 electrolyte, NaNO3 electrolyte, NaCl electrolyte, Na2Cr2O7 electrolyte, HOCH2CH2OH electrolyte, and combinations thereof.
In further detail, the step of electro-chemically removing the portion of the welding material may further include the step of (i) providing an electrolyte; (ii) placing a cathode into the electrolyte; (iii) placing a portion of the stent having the welding material into the electrolyte; (iv) providing an electrical voltage or current so that the cathode is negatively charged and the stent portion is positively charged; and (v) partially dissolving the portion of the stent exposed to the electrolyte.
In another aspect of the present invention, the method of making the stent may further include the steps of (i) extending at least one of the mated stent wires to provide an extended stent wire; (ii) looping the extended stent wire so the extended end abuts a proximal pair of stent wires; and (iii) welding extended and looped wire to the proximal pair of wires. Desirably, the step of looping includes forming the wire into an arch with equilateral sides, having an apex, but not having other sharp bends. Desirably, the step of looping includes forming the wire into an equilateral arch having one vertex having similar curvatures on either side of the one vertex, where the equilateral arch does not contain a second vertex having dissimilar curvatures on either side of the second vertex.
In another aspect of the present invention, the method of making the stent may further include the steps of (i) extending at least one of the mated stent wires past the abutting regions to provide an extended stent wire; and (ii) looping the extended stent wire at its extended end to form a coil thereat. A plurality of extended wires may also be formed into one coil or pig tail.
Desirably, the elongate wires comprise biocompatible materials selected from the group consisting of nitinol, stainless steel, cobalt-based alloy such as Elgiloy, platinum, gold, titanium, tantalum, niobium, and combinations thereof, preferably nitinol. The elongate wires may be composite wires for improved radiopacity, such as having an inner core of tantalum, gold, platinum, iridium or combination of thereof and an outer layer or member of nitinol.
In another aspect of the present invention, an implantable stent is provided. The stent of this aspect of the present invention may include a plurality of wires arranged to form a hollow tubular structure having a tubular wall to define an interior surface and an exterior surface and having opposed open first and second ends, where the wires terminate at the second open end ends and adjacently abutting wires are welded at the second open end with a welding material to provide welds, and further where at least a portion of the welded material has been removed to reduce the profile of the welds. Desirably, the portion of welded material has been removed by chemical or electro-chemical polishing. Preferably, at least 25 to 50% by weight of the stent material at or around the weld location has been removed. The reduced profile of the welds are from about 5 to about 50 linear percent of a diameter of the stent wires.
The stent includes wires made from bio compatible materials, such as nitinol, stainless steel, cobalt-based alloy such as Elgiloy, platinum, gold, titanium, tantalum, niobium, and combinations thereof. The weld material and the wire material may also be the same, for example nitinol. Further, the elongate wires have an inner core of tantalum gold, platinum, iridium or combination of thereof and an outer member of nitinol.
In another aspect of the present invention, at least one some of the adjacently abutting stent wires are extended past the welds and looped into an arch with equilateral sides having an apex, but not having other sharp bends, or in other words at least some of the adjacently abutting stent wires are extended past the welds and looped into an arch with equilateral sides having one vertex having similar curvatures on either side of the one vertex, where the arch design does not contain a second vertex having dissimilar curvatures on either side of the second vertex. Alternatively, at least some of the adjacently abutting stent wires are extended past the welds and looped to form a coil thereat in the shape of a pig tail. Still alternatively, at least some of the adjacently abutting stent wires are extended past the welds and looped to form one coil thereat.
The stent wires may be coated, for example coated with silicone. Further, the stent may be fully or partially covered with a polymeric covering, such as silicone, in order to prevent tissue or tumor ingrowth.
The stent may further include a hollow tubular graft disposed over the interior or the exterior surface. The graft may be a polymeric material, for example, a polyester, a polypropylene, a polyethylene, a polyurethane, a polynaphthalene, a polytetrafluoroethylene, an expanded polytetrafluoroethylene, a silicone, and combinations thereof.
Desirably, the stent is a braided stent.
The stent may further include a polymeric ring disposed over the exterior surface at the second open end. Additionally, the stent may further include a suture secured to one of the open ends. Such suture or sutures are useful for positioning, repositioning, and/or removing the stent. The suture can be a metallic, polymeric or textile suture loop threaded through the stent loops at one or both extremities of the stent. The suture loop may include a protruding part to help facilitate the capture or grabbing of the stent end.
In another aspect of the present invention, an implantable stent includes a plurality of wires arranged to form a hollow tubular structure having a tubular wall to define an interior surface and an exterior surface and having opposed open first and second ends, where the wires terminate at the second open end ends and adjacently abutting wires are welded at the second open end with a welding material to provide welds, and further where at least a portion of the welded material has been removed by chemical or electrochemical polishing to reduce the profile of the welds.
The present invention overcomes the deficiencies of the prior art by providing, among other things, low profile stent welds that reduce stent deployment forces.
A welded stent 10′ according to the present invention is depicted in
A pair of adjacently welded wires according to the present invention is depicted in
Useful welding methods include, but are not limited to, laser welding, electron beam welding, resistance welding, tungsten inert gas welding, metal inert gas welding and combinations thereof. In laser and electron beam welding the wires are partially melted by the energy provided by the laser or electron beam. In gas tungsten arc welding (GTAW or TIG welding), an arc is formed between an electrode, typically tungsten, and the metal being welded. In metal inert gas (MIG) welding, an arc is generated between a filler electrode and the metal being welded with metal melted from the filler electrode being added to the metal being welded. Resistance welding uses the application of electric current and sometimes mechanical pressure to create a weld between two pieces of metal. The weld areas may be shielded with an inert gas. Suitable, but non-limiting, inert gasses include argon and argon/gas admixtures, such as argon/hydrogen or argon/helium.
Desirably, the wires 22 are made from nitinol, stainless steel, cobalt-based alloy such as Elgiloy, platinum, gold, titanium, tantalum, niobium, and combinations thereof. Further, the wires 22 have an inner core of tantalum gold, platinum, iridium or combination of thereof and an outer member or layer of nitinol to provide a composite wire for improved radiocapicity or visibility. Further details of such composite wires may be found in U.S. Patent Application Publication 2002/0035396 A1, the contents of which is incorporated herein by reference. Preferably, the wires 22 are made from nitinol. Further, the filling weld material, if required by welding processes such as MIG, may also be made from nitinol, stainless steel, cobalt-based alloy such as Elgiloy, platinum, gold, titanium, tantalum, niobium, and combinations thereof, preferably nitinol. The material of the cathode is no critical and can be made out of any suitable metal. The filling weld material and the wire 22 may be made of the same material, for example nitinol.
As the chemical electro-chemical polishing 30 removes material from portions of the stent 10 that are disposed within the electrolyte 32, there are several means to selectively remove material from the stent 10, such as welds 24, 24′, burrs or other imperfections (not shown), and the like. One technique for selectively removing material is through the use of a photoresist or insulator, which is an organic polymer or resin that can be applied to selective areas of the stent 10 to avoid the electrochemical polishing of covered parts 30 as the photoresist insulates the selected from the action of the electrolyte. For example, as depicted in
Alternatively, chemical polishing, chemical etching and the like may be used to remove portions of the weld 24, 24′ and optionally portions of the stent wire 22. Chemical polishing or etching is similar to the above described electrochemical methods, expect an oxidizing acid is added to the electrolyte and associated equipment (current or voltage source, cathode, etc.) is optionally not necessary. Useful, but not limiting, oxidizing acid-containing electrolytes include electrolytes having hydrofluoric acid, nitric acid, and combinations thereof.
The present invention, however, is not limited to low profile welds just at terminatingly adjacent wires, such as wires 22 of
As depicted in
Desirably, the extended loop portions 66, 67 are of an arch with equilateral sides design, which can be referred to as a cathedral type of arch or loop. As depicted in
The equilaterally arched loop design offers several advantages, including reduced deployment force, as compared to prior art loop designs having a plurality of vertices or sharp bends. When a stent is constrained on or in a delivery system (not shown) the multiple sharp bends in the end loops of the stent typically impinge on the wall of the delivery system and become slightly imbedded thereat, thereby distorting the outer sheath of the delivery system. This results in significantly greater deployment force values. Further, as the equilaterally arched loop has only one sharp bend, i.e., its apex, and is defined otherwise by a gradual curvature, the gradual curvature portions do not become imbedded in the wall of the delivery system, thereby significantly reducing the resultant deployment force.
In another aspect of the present invention as depicted in
In still a further aspect of the present invention, the stent 10 may have other designs at open end 12 that are useful for positioning, repositioning, and/or removing stent 10. As depicted in
As depicted in
With any embodiment of the stent 10, 10′ is usable to maintain patency of a bodily vessel, such as in the coronary or peripheral vasculature, esophagus, trachea, bronchi colon, biliary tract, urinary tract, prostate, brain, and the like. Also, the stent 10, 10′ may be treated with any of the following: anti-thrombogenic agents (such as heparin, heparin derivatives, urokinase, and PPack (dextrophenylalanine proline arginine chloromethylketone); anti-proliferative agents (such as enoxaprin, angiopeptin, or monoclonal antibodies capable of blocking smooth muscle cell proliferation, hirudin, and acetylsalicylic acid); anti-inflammatory agents (such as dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, and mesalamine); antineoplastic/antiproliferative/anti-miotic agents (such as paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine, epothilones, endostatin, angiostatin and thymidine kinase inhibitors); anesthetic agents (such as lidocaine, bupivacaine, and ropivacaine); anti-coagulants (such as D-Phe-Pro-Arg chloromethyl keton, an RGD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, aspirin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet peptides); vascular cell growth promotors (such as growth factor inhibitors, growth factor receptor antagonists, transcriptional activators, and translational promoters); vascular cell growth inhibitors (such as growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin); cholesterol-lowering agents; vasodilating agents; and agents which interfere with endogenous vascoactive mechanisms.
The invention being thus described, it will now be evident to those skilled in the art that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention and all such modifications are intended to be included within the scope of the following claims.
Claims
1. A prosthesis, the prosthesis comprising a plurality of wires, each wire comprising at least one weld region and at least one non-weld region, each non-weld region having a first diameter, each weld region having a second diameter less than the first diameter; and
- a plurality of welds, each weld comprising a weld region of at least two of the plurality of wires.
2. The prosthesis of claim 1, the prosthesis being a tubular mesh, the tubular mesh comprising the plurality of wires.
3. The prosthesis of claim 2, the tubular mesh being selected from the group consisting of a braid, a weave, or a knit.
4. The prosthesis of claim 1, wherein the weld regions forming a weld are substantially parallel to one another.
5. The prosthesis of claim 1, the prosthesis comprising a first end region and a second end region, the at least one first weld located in the first end region of the prosthesis, the first end region having a reduced diameter relative to other regions of the prosthesis.
6. The prosthesis of claim 1, the prosthesis further comprising a band of biocompatible material, the band being attached to an outer surface of a portion of the first end region.
7. The prosthesis of claim 1, each weld comprising a weld region of only two of the plurality of wires.
8. The prosthesis of claim 1, the plurality of welds comprising a plurality of first welds and a plurality of second welds, each first weld comprising a weld region of two of the plurality of wires, each second weld comprising a weld region of three of the plurality of wires.
9. The prosthesis of claim 8, wherein one of the three of the plurality of wires of a second weld also forms a part of a first weld.
10. The prosthesis of claim 9, the one of the three of the plurality of wires forming a loop.
11. The prosthesis of claim 10, the first welds and the second welds longitudinally aligned, each first weld being between two second welds and each second weld being between two first welds.
12. The prosthesis of claim 1, each wire having a first end region, the weld regions comprising first weld regions and second weld regions, each first weld region forming the first end region of a wire and each second weld region being a distance away from the first end region of a wire, the plurality of welds comprising a plurality of first welds, each first weld comprising one first weld region of a wire and one second weld region of a wire.
13. The prosthesis of claim 12, each first weld located at a first longitudinal position of the prosthesis, the plurality of welds further comprising second welds, each second weld comprising one first weld region of a wire and one second weld region of a wire, and each second weld located at a second longitudinal position of the prosthesis, the second longitudinal position being different than the first longitudinal position.
14. The prosthesis of claim 13, wherein the first and second welds have a wire in common.
15. The prosthesis of claim 13, the prosthesis further comprising a plurality of coils, each coil longitudinally aligned and forming a first end of the prosthesis, the second welds longitudinally aligned and positioned a first distance from the coils, the first welds longitudinally aligned and positioned a second distance from the coils, the second distance being greater than the first distance.
16. The prosthesis of claim 12, the prosthesis comprising a plurality of first welds, the first welds being a distance from a hook forming a first end of the prosthesis, the hook comprising wires with a second weld region forming a part of one of the plurality of first welds.
17. A prosthesis, the prosthesis having a first end and a second end, the prosthesis being a tubular mesh comprising a plurality of wires, each wire having a first diameter,
- the plurality of wires comprising: a plurality of first wires, each first wire comprising a first weld region, the first weld region including an end of the first wire; a plurality of second wires, each second wire comprising a first end and a first weld region, the first weld region positioned a first distance from the first end of the second wire; a plurality of third wires, each third wire comprising a first end and a first weld region, the first weld region being located a first distance away from the first end of the third wire; the prosthesis further comprising a plurality of first welds, each first weld positioned a first distance away from the first end of the prosthesis, each first weld comprising: the first weld region of one first wire and one of the first weld region of one second wire or the first weld region of one third wire.
18. The prosthesis of claim 17, each third wire comprising a coil portion, the coil portions of the plurality of third wires forming the first end of the prosthesis.
19. The prosthesis of claim 17, further comprising a plurality of second welds, each second weld positioned a second distance away from the first end of the prosthesis, where the second distance is less than the first distance.
20. The prosthesis of claim 19, each second wire further comprising a second weld region, the second weld region including the first end of the second wire;
- each third wire further comprising a second weld region, the second weld region being located a second distance away from the first end of the third wire, where the second distance is less than the first distance;
- each second weld comprising the second weld region of one second wire and the second weld region of one third wire.
Type: Application
Filed: Aug 8, 2011
Publication Date: Dec 1, 2011
Applicant: BOSTON SCIENTIFIC SCIMED, INC. (Maple Grove, MN)
Inventors: Claude O. Clerc (Marlborough, MA), Paul K. Norton (Lunenburg, MA), Michael Zupkofska (Rockland, MA), Gary J. Leanna (Holden, MA), George Tom Roberts (Lincoln, MA)
Application Number: 13/205,283