Stents having a hybrid pattern and methods of manufacture

Abstract

An intravascular stent and method of making an intervascular stent having a hybrid pattern a. The hybrid pattern comprises a plurality of circumferentially self-expansible members comprising a plurality of interconnected, geometrically deformable closed cells, adjacent self-expansible members interconnected by a plurality of bridge members linking a first interconnection between two closed cells in a first self-expansible member to a second interconnection between two closed cells in a second self-expansible member, wherein the second interconnection is circumferentially offset and non-adjacent to the first interconnection.

Claims

1. A method of making an intravascular stent, comprising the steps of: a. vacuum depositing a metal onto a substrate; b. patterning a stent pattern onto the deposited metal, wherein the pattern comprises a first plurality of interconnected closed cells connected along a first lateral axis, and at least a second plurality of interconnected closed cells connected along a second lateral axis longitudinally offset from the first lateral axis, the first plurality of interconnected closed cells and the at least a second plurality of interconnected closed cells interconnected by a plurality of bridge members along a longitudinal axis, each bridge member forming a continuous undulating waveform linking a first interconnection between two closed cells in the first plurality of interconnected closed cells at a peak or a trough of the continuous undulating waveform to a second interconnection between two interconnected closed cells in the at least second plurality of interconnected closed cell members at a respective trough or a respective peak of the continuous undulating waveform; and c. removing the stent pattern from the substrate.

2. The method of claim 1, wherein the step of patterning further comprises patterning each of the plurality of bridge members to be separated by at least two interconnected closed cells of the first plurality of interconnected closed cells along the first lateral axis of the first plurality of interconnected closed cells.

3. The method of claim 1, wherein the step of vacuum depositing further includes the step of providing a pre-patterned cylindrical substrate and the step of patterning includes forming the pattern by vacuum depositing the thin film onto the pre-patterned cylindrical substrate.

4. The method of claim 1, wherein the step of patterning comprises laser patterning to impart at least one feature on the at least one surface of the deposited metal.

5. The method of claim 4, wherein the laser patterning is an athermal process characterized by low slag formation during laser patterning.

6. The method of claim 1 wherein the metal is selected from the group of elemental titanium, vanadium, aluminum, nickel, tantalum, zirconium, chromium, silver, gold, silicon, magnesium, niobium, scandium, platinum, cobalt, palladium, manganese, molybdenum and alloys thereof.

7. The method of claim 1 wherein the step of patterning a stent onto the deposited metal and forming a first plurality of interconnected closed cells or forming a second plurality of interconnected closed cells further comprises forming each closed cell of the first plurality or second plurality of interconnected closed cells into a diamond expanded shape, circular expanded shape, elliptical expanded shape, triangular expanded shape, rectangular expanded shape, or square.

8. The method of claim 1, wherein the step of vacuum depositing further includes the step of providing a pre-patterned planar substrate and the step of patterning includes forming the pattern by vacuum depositing the thin film onto the pre-patterned planar substrate.

9. The method of claim 1, wherein the step of vacuum depositing metal onto a substrate further comprises the step of vacuum depositing a thin film metal having a thickness between 1 and about 1000 microns.

10. The method of claim 1, wherein the step of vacuum depositing metal onto a substrate further comprises the step of vacuum depositing layers of dissimilar metals.

11. The method of claim 1, further comprising the step of forming a plurality of grooves on a surface of the stent pattern.

12. The method of claim 1, further comprising the step of descale or oxide removal from the stent pattern.

13. The method of claim 1, further comprising the step of electropolishing the stent pattern.

14. The method of claim 1, further comprising the step of shape setting the stent pattern.

15. The method of claim 1, wherein the step of vacuum depositing a metal onto a substrate further comprises the steps of vacuum depositing plural layers of metal to form laminated layers of metal.

16. The method of claim 1, wherein the first plurality of interconnected closed cells, the second plurality of interconnected closed cells, and the plurality of bridge members are configured in a pattern having blood flow diversion properties.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying figures, like elements are identified by like reference numerals among the several preferred embodiments of the present invention.

(2) FIG. 1 is a combined logic flow and block diagram illustrating a method of manufacturing a hybrid pattern stent using ribbon wire.

(3) FIG. 2 is an isometric view of a hybrid pattern micro-stent.

(4) FIG. 3 is a side view of a hybrid pattern micro-stent.

(5) FIG. 4 is a low magnification image showing high density (top) and low density (bottom) hybrid pattern micro-stents.

(6) FIG. 5A is a low magnification image showing a high density pattern micro-stent in a glass tube through a 90 degree bend; FIG. 5B is a high magnification image showing a high density pattern micro-stent in a glass tube through a 90 degree bend.

(7) FIG. 6 is a high density micro-stent crimped configuration constrained by a PTFE tube.

(8) FIG. 7 is a low magnification image of a low density micro-stent.

(9) FIG. 8 is a low density micro-stent shown in a 180 degree free bend.

(10) FIG. 9A is a low density micro-stent crimped configuration constrained by a sub-millimeter inner diameter PTFE tube; FIG. 9B is a zoomed in view of a section of the stent of FIG. 9A.

DETAILED DESCRIPTION OF THE INVENTION

(11) The foregoing and other features and advantages of the invention are apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.

(12) The present invention is an improved stent which has good radial strength to hold a vessel open and improved flexibility that is suitable for implantation in more sharply bent vessels.

(13) In accordance with the invention, the foregoing advantages have been achieved through the herein disclosed hybrid pattern intravascular stents and methods of manufacturing hybrid pattern intravascular stents utilizing thin ribbons of material having portions cut and etched therefrom to form hybrid patterns.

(14) In one embodiment, depicted in FIG. 1 as a combined logic flow and block diagram, disclosed is a method (100) of manufacturing an intravascular stent, comprising the steps of: providing a thin ribbon or wire of material (105) having a predetermined thickness and width; winding the thin ribbon around a mandrel (130); and shaping the wound thin ribbon into a desired stent frame shape.

(15) In some embodiments, the material is a nickel-titanium alloy. In some embodiments, materials to make the inventive stents are chosen for their biocompatibility, mechanical properties, i.e., tensile strength, yield strength, and their ease of deposition include the following: elemental titanium, vanadium, aluminum, nickel, tantalum, zirconium, chromium, silver, gold, silicon, magnesium, niobium, scandium, platinum, cobalt, palladium, manganese, molybdenum and alloys thereof, such as zirconium-titanium-tantalum alloys, nitinol, and stainless steel.

(16) In some embodiments, the predetermined thickness and width is obtained by passing the thin ribbon of material through at least one of a wire flattener and a width trimmer (110).

(17) In some embodiments, the method (100) further comprises the step of patterning at least one surface of the thin ribbon (115), prior to or simultaneous with the step of winding around the mandrel (130). In some embodiments, the patterning (115) comprises laser patterning to impart at least one feature on the at least one surface of the thin ribbon. In some embodiments, the pattern is a series of grooves on at least one surface of the thin ribbon, preferably the surface that will comprise the inner diameter of the finished stent. In other embodiments, the pattern may be a plurality of microgrooves imparted onto the luminal and/or abluminal surface of the thin ribbon, as is more fully described in International Publication No. WO 99/023977, published 20 May 1999, which is commonly assigned with the present application and is hereby incorporated by reference in its entirety.

(18) In some embodiments, the method (100) further comprises the step of laser cutting a stent strut pattern into the thin ribbon (120), prior to or simultaneous with the step of winding around the mandrel (130). In some embodiments, the laser cutting (120) is a cold process that produces minimal slag.

(19) In some embodiments, the method (100) further comprises the step of polishing the thin ribbon (125), prior to or simultaneous with the step of winding around the mandrel (130).

(20) In some embodiments, the mandrel is generally cylindrical in shape. In some embodiments, the formed stent frame is generally cylindrical in shape.

(21) It is further contemplated that the stent method uses a thin wire or ribbon of material, such metals like NiTi or other materials, and wind the wire or ribbon on a mandrel to create a stent frame. Prior to, or while winding, the ribbon surfaces are easily accessible from all sides, hence one side, possibly what will become the internal dimension of the stent, of the ribbon could be patterned with a tool such as a laser creating a grooved surface. This wound tube with a patterned internal dimension, would then be further processed, as necessary, like other stents disclosed in the prior art.

(22) In particular, a flat ribbon or wire comprised of biocompatible material is provided wherein the ribbon has predetermined length, width and thickness. In some embodiments, the ribbon or wire may be passed through a wire flattener and/or a width trimmer to achieve the desired thickness and/or width. A stent is formed from this material by forming cuts in the material so that the cut material can be stretched to form an undulating wave-like pattern. The cut ribbon is then spirally wound into a generally cylindrical shape to form a stent segment. Plural stent segments can be affixed to one another in longitudinal succession to form an elongate stent using a connector which is formed from the ribbon. Interconnection between adjacent stent segments is achieved by combining two connectors where the connectors may be fabricated at one-half their original width and bonded together by welding or other means.

(23) In particular, one skilled in the art commences with a spool or ribbon or wire with a predetermined thickness and width. In some embodiments, the ribbon or wire may be passed through a wire flattener and/or a width trimmer to achieve the desired thickness and/or width. In some embodiments, a pattern is imparted on the interior dimension surface of the ribbon. The pattern may be imparted by utilizing a laser to pattern the interior dimension surface. Next, a cut pattern for stent struts is imparted onto the ribbon. In some embodiments, a laser may be used to create the cut pattern for stent struts. In some embodiments, an optional surface polish is placed on the interior dimension surface. Finally, the wire or ribbon is wound on a mandrel altering and shaping the wire or ribbon in a predetermined shape/pattern, thus creating an expandable stent, or other medical device. In specific instances, particularly for Nitinol, it may make sense to “train” parts to expand to final diameters via shape setting using heat treatment(s)/annealing. This additional processing will likely be followed by descale/oxide removal chemical treatments and electropolishing to achieve final surface finish desired.

(24) FIG. 2 depicts an isometric view of an implantable medical device 200, such as but not limited to an intravascular stent, comprising: a plurality of circumferentially self-expansible members 210, each comprising a plurality of geometrically deformable closed cells 230, the closed cells 230 being interconnected at interconnections 250 to form a tubular structure; and a plurality of bridge members 260 interconnecting adjacent circumferentially self-expansible members 210, each bridge member 260 linking a first interconnection 250 between two adjacent closed cells 230 in a first circumferentially self-expansible member 210 to a second interconnection 250 between two adjacent closed cells 230 in a second circumferentially self-expansible member 210. In many embodiments, the second interconnection 250 is circumferentially offset and non-adjacent to the first interconnection 250. In some embodiments, the geometrically deformable closed cells 230 have a generally diamond expanded shape. FIG. 3 depicts a side view of the implantable medical device 200 of FIG. 2. In other embodiments, the geometrically deformable closed cells 230 may take other expanded shapes, including but not limited to circles, ovals, triangles, rectangles, squares, and/or the like.

(25) In some embodiments, the hybrid stent pattern may allow for improved stent actuation using a start tube comprised of laminated layers of nitinol, stainless steel, L-605, MP35N, PtCr, TiTa, or other stent making materials. In some embodiments, it may be feasible to use (although after galvanic coupling evaluations) dissimilar metals to “enhance” the mechanical performance with respect to strength, toughness and possibly shape memory effect if Nitinol is involved. Using the metals listed in conjunction with Nitinol may possibly enhance the radiopacity of the resulting device, and improve chemical/visual. In some embodiments, the stent may further comprise a layer of radiopaque material.

(26) In some embodiments, the plurality of circumferentially self-expansible members 210 each have a wall thickness of less than 75 micrometers. In some embodiments, the plurality of circumferentially self-expansible members 210 each have a wall thickness of between 40 microns and 50 microns. Alternatively, the thickness of the members 210 may be between 1 micron and 1000 microns depending on the strength and thickness desired. Generally, the thin wall nature of the hybrid pattern stent 200 serves to discourage thrombogenicity and allows for low delivery profile.

(27) Preferably, the hybrid pattern is a combination of closed cells 230 and open cells or bridges 260, which serves to simultaneously provide adequate scaffold strength (from the closed cells 230) and flexibility (from the open cells or bridges 260). In addition, long bridge lengths can allow for extreme and efficient propagation of stent longitudinal length in bends without significantly sacrificing longitudinal compliance. This may further allow high flexibility through torturous anatomy, as demonstrated in FIGS. 5A-B and 8. In some embodiments, the bridge interconnect interval or length may be altered to enhance or lessen longitudinal flexibility, as desired for a particular application of a given hybrid pattern stent. Bridge members may to enhance or lessen the longitudinal flexibility. In additional embodiments, varying the strut width or the shape (diversions from straight elements) of the bridge interconnect may adjust stiffness.

(28) In some embodiments, the device 200 comprises a biocompatible material. Materials to make the inventive devices are chosen for their biocompatibility, mechanical properties, i.e., tensile strength, yield strength, and their ease of deposition include the following: elemental titanium, vanadium, aluminum, nickel, tantalum, zirconium, chromium, silver, gold, silicon, magnesium, niobium, scandium, platinum, cobalt, palladium, manganese, molybdenum and alloys thereof, such as zirconium-titanium-tantalum alloys, nitinol, and stainless steel. Alternatively, other biocompatible pseudo-metals and polymers may be used.

(29) In some embodiments, the pattern of closed cells 230 and bridge members 260 provides flow diversion properties.

(30) In some embodiments, the orientation of the plurality of bridge members 260 alternates between adjacent pairs of circumferentially self-expansible members 210, thereby allowing for a smooth and uniform crimp and/or expansion mechanism. In some embodiments, the orientation of the plurality of bridge members 260 is the same between adjacent pairs of circumferentially self-expansible members 210.

(31) In some embodiments, the device 200 is crimpable to an outer diameter of less than 1 mm. In some embodiments, the device 200 has an expanded diameter of between 3 mm and 5 mm. In some embodiments, the device 200 is capable of bending without severe buckling on an inner surface proximate the position of the bend (see FIGS. 5A and 8).

(32) In some embodiments, as shown in FIGS. 4-6, a dense hybrid pattern 400 may serve to constrain plaque, especially vulnerable plaque.

(33) FIG. 4 depicts two distinct hybrid pattern embodiments of the present invention—a high density hybrid pattern stent 400 and a low density hybrid pattern stent 450. Both patterns have a plurality of circumferentially self-expansible members 410, 460, each comprising a plurality of geometrically deformable closed cells 420, 470, the closed cells 420, 470 being interconnected at interconnections 423, 473 to form a tubular structure; and a plurality of bridge members 425, 475 interconnecting adjacent circumferentially self-expansible members 410, 460, each bridge member 425, 475 linking a first interconnection 423, 473 between two adjacent closed cells 420, 470 in a first circumferentially self-expansible member 410, 460 to a second interconnection 423, 473 between two adjacent closed cells 420, 470 in a second circumferentially self-expansible member 410, 460, wherein the second interconnection 423, 473 is circumferentially offset and non-adjacent to the first interconnection 423, 473.

(34) FIG. 5A illustrates a high density pattern stent 400 in a glass tube 500 having a 3 mm inner diameter, through a 90 degree bend. FIG. 5B is an enlarged view of a portion of the high density pattern stent 400 of FIG. 5A.

(35) FIG. 6 illustrates is a high density pattern stent 400 in a crimped configuration constrained by a PTFE tube 600. In some embodiments, in the crimped configuration, the high density pattern stent 400 has an outer diameter between about 1 mm and about 1.5 mm.

(36) FIG. 7 illustrates a low density pattern stent 450 having an outer diameter of about 3.5 mm.

(37) FIG. 8 illustrates a low density pattern stent 450 in a 180 degree free bend.

(38) FIG. 9A illustrates a low density pattern stent 450 in a crimped configuration constrained by a less than 1 mm inner diameter PTFE tube 900. FIG. 9B illustrates an enlarged view of a portion of the low density pattern stent 450 of FIG. 9A.

(39) As illustrated in FIGS. 4 and 7, in some embodiments, for the low density hybrid pattern stent 450, the bridge members 475 are capable of expansion outward from the circumferential plane to serve as a distributed flare for device fixation to prevent migration in situ.

(40) Some embodiments of the present invention may be fabricated by employing a vapor deposition technique which entails vapor depositing a stent-forming metal onto a substrate. The substrate may be planar or cylindrical and is either pre-patterned with one of the preferred geometries of first and interconnecting members, in either positive or negative image, or the substrate may be un-patterned. Where the substrate is un-patterned, the deposited stent-forming metal is subjected to post-deposition patterning to pattern the deposited stent-forming metal into one of the preferred geometries of the first and interconnecting members. In all embodiments of the present invention fabricated by vapor deposition techniques, the need for post-deposition processing of the patterned endoluminal stent, e.g., modifying the surface of the stent by mechanical, electrical, thermal or chemical machining or polishing, is eliminated or minimized.

(41) While the invention has been described in connection with various embodiments, it will be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the invention following, in general, the principles of the invention, and including such departures from the present disclosure as, within the known and customary practice within the art to which the invention pertains.