Stent and method and apparatus for forming and delivering the same

• US 5,540,712 A
• Filed: 06/01/1994
• Issued: 07/30/1996
• Est. Priority Date: 05/01/1992
• Status: Expired due to Fees

• Current Assignee: NMT Medical Incorporated
• Original Assignee: Nitinol Medical Technologies Incorporated
• Inventors: Kleshinski, Stephen J., Rabkin, Dmitry, Simon, Morris A.
• Primary Examiner(s): Brown, Michael A.
• Application Number:
  US08/252,198
• Time in Patent Office: 790 Days
• Field of Search: 606/191, 606/192, 606/195, 606/198, 604/96, 604/104-106, 604/284, 623/1, 623/12
• US Class Current: 623/1.19
• CPC Class Codes: A61F 2/0077 Special surfaces of prostheses, e.g. for improving ingrowth A61F2/30767 takes precedence
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2/95 Instruments specially adapted for placement or removal of stents or stent-grafts
• CPC Class Codes: A61F 2002/8483 Barbs
• CPC Class Codes: A61F 2002/9534 for repositioning of stents
• CPC Class Codes: A61F 2210/0023 operated at different temperatures whilst inside or touching the human body, heated or cooled by external energy source or cold supply
• CPC Class Codes: A61F 2210/009 magnetic
• CPC Class Codes: A61F 2220/0008 Fixation appliances for connecting prostheses to the body
• CPC Class Codes: A61F 2220/0016 with sharp anchoring protrusions, e.g. barbs, pins, spikes
• CPC Class Codes: A61F 2230/0013 Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2230/0017 Angular shapes
• CPC Class Codes: A61F 2240/001 Designing or manufacturing processes
• CPC Class Codes: A61F 2250/0018 differing in elasticity, stiffness or compressibility
• CPC Class Codes: Y10S 623/901 Method of manufacturing prosthetic device

Abstract

A stent including a wire skeletal frame, the frame being adapted to assume a first condition in which the frame is relatively rigid and substantially tubular in configuration and a second condition in which the frame is flexible, of reduced stress, and collapsible, such that in the second condition walls of the frame are adapted to be positioned against each other to form a stent diameter substantially equal to the combined thickness of the frame walls in abutting engagement with each other, the frame in its second condition being substantially devoid of bias therein urging the frame to assume the first configuration.

Claims

1. A stent comprising an elongate body member having a longitudinal axis with a skeletal frame formed to define an elongate chamber which extends through said body member, the body member being formed of thermal shape memory material which operates in response to temperature to expand or contract said skeletal frame between a first expanded configuration and a second compressed configuration, said body member including a plurality of interconnected, open cells forming the skeletal frame of said body member, each of said cells including two substantially parallel, spaced side portions which are substantially parallel to said longitudinal axis and end wall means extending between said side portions at an angle to said longitudinal axis, said end wall means operating to maintain said cell straight side portions substantially parallel to said longitudinal axis in both said first expanded configuration of said skeletal frame and in said second collapsed configuration.

2. The stent of claim 1 wherein said cells are formed of at least one elongate strand of shape memory material and joined together only along the lengths of said straight portions.

3. The stent of claim 1 wherein said shape memory material has a temperature transformation level above which said skeletal frame assumes a first expanded configuration relative to said longitudinal axis and below which said cell end wall means permit movement of said straight portions toward said longitudinal axis to collapse said skeletal frame to a second collapsed configuration, said cells being interconnected only at said straight side portions with no connection between the end wall means thereof.

4. The stent of claim 3 wherein said cell end wall means operate at a temperature above said temperature transformation level when said skeletal frame is in the second collapsed configuration to expand the skeletal frame to the first expanded configuration.

5. The stent of claim 4 wherein said end wall means operate to cause the space between the straight side portions of said cells to decrease in order to collapse said skeletal frame to the second collapsed configuration.

6. The stent of claim 5 wherein said cell end wall means are relatively pliable when said skeletal frame is subjected to temperatures below said temperature transformation level and are resiliently deformable but relatively rigid when said skeletal frame is subjected to temperatures above said temperature transformation level.

7. The stent of claim 5 wherein said cells are polygonal in shape.

8. The stent of claim 7 wherein said cells are hexagonal in shape.

9. The stent of claim 5 wherein said cells are joined together only along the lengths of said straight portions.

10. The stent of claim 5 wherein said cell end wall means each include first and second wall sections, each said wall section having a first end joined to one of the side portions of said cell, said wall section extending at an angle to the side portion to which the first end thereof is joined, and each said wall section having a second end opposite to said first end, the second ends of said first and second wall sections being joined.

11. The stent of claim 5 wherein said skeletal frame includes cells of different sizes.

12. The stent of claim 5 wherein the side portions and end wall means of some cells in said skeletal frame are formed to have a greater cross-sectional area than the side portions and end wall means of other cells in said skeletal frame.

13. The stent of claim 5 wherein the thermal shape memory material forming the side portions and end wall means of some cells in said skeletal frame has a temperature transformation level which differs from the temperature transformation level of the thermal shape memory material forming the side portions and end wall means of other cells in said skeletal frame.

14. The stent of claim 4 wherein said body member includes opposed open ends, said elongate chamber extending between said open ends, the skeletal frame adjacent to at least one of said open ends being formed to provide laterally extending means annularly of said open end in said first expanded configuration.

15. A stent for insertion in a body vessel comprising an elongate body means having a longitudinal axis, a first end, a second end, and an elongate chamber extending through said body means between said first and second ends, the body means being formed of thermal shape memory material which is relatively pliable at temperatures below a transition temperature to permit said body means to be collapsed toward said longitudinal axis to a collapsed configuration, for insertion in said body vessel, said thermal shape memory material operating to expand said body means radially outward from said collapsed configuration toward an expanded memory configuration in response to said transition temperature to contact and apply force to said body vessel, said body means operating at said transition temperature to apply less force to said body vessel in the area of at least one of said first and second ends than the force applied by the remainder of said body means to said body vessel at the transition temperature.

16. A method for forming a stent of thermal shape memory material which becomes pliable to permit the stent to be collapsed at temperatures below a temperature transformation level and which expands the collapsed stent to a preset memory shape at temperatures above the temperature transformation level which includes the steps of

forming a plurality of open cells from thermal shape memory material,

fusion welding the thermal shape memory material to form a stent body member with an elongate chamber extending therethrough,

and subsequently annealing said body member at a temperature sufficient to set the memory shape of said stent while rendering ductile the fusion welds.

17. The method of claim 16 which includes placing at least one elongate strand of thermal shape memory material on a heat conductive mandrel to form said plurality of open cells,

joining said open cells on said heat conductive mandrel by fusion welding to form said stent body member, and subsequently annealing said stent body member on said heat conductive mandrel.

18. The method of claim 17 which includes forming a plurality of adjacent open cells which extend completely around said mandrel, each such cell being formed with two spaced, substantially parallel side walls arranged to extend substantially parallel to the longitudinal axis of said mandrel and joining said cells by fusion welding only along the sidewalls of adjacent cells.

19. A stent comprising an elongate body member having a longitudinal axis with a skeletal frame formed to define an elongate chamber which extends through said body member, the skeletal frame being formed to assume a first expanded configuration relative to said longitudinal axis and to be collapsible toward said longitudinal axis to a second collapsed configuration, said skeletal frame further being formed to define a plurality of interconnected open cells with each of said cells including two substantially parallel, spaced side walls which are substantially parallel to said longitudinal axis in both the first expanded configuration and the second collapsed configuration of said skeletal frame and end walls extending between said sidewalls at an angle to said longitudinal axis, said cells being arranged around said elongate chamber with sidewalls of adjacent cells arranged in adjacent coextensive relationship, said cells joined together by an attachment connecting adjacent, coextensive cell sidewalls, this being the only connection between said cells.

20. The stent of claim 19 wherein said cells are polygonal in shape.

21. The stent of claim 20 wherein said cells are hexagonal in shape.

22. The stent of claim 19 wherein said cell end walls each include first and second wall sections, each said wall section having a first end joined to one of the sidewalls of said cell, said wall section extending at an angle to the sidewall to which the first end thereof is joined, and each said wall section having a second end opposite to said first end, the second ends of said first and second wall sections being joined.

23. A stent comprising an elongate body member having a first section, a second section, a longitudinal axis and an elongate chamber which extends through said body member, the body member being formed of thermal shape memory material having a temperature transformation level above which said body member assumes an expanded configuration relative to said longitudinal axis and below which said body member may be collapsed to a collapsed configuration, the shape memory material in said first section of said body member having a temperature transformation level which differs from the temperature transformation level of the shape memory material in said second section of said body member.

24. A stent comprising an elongate body member having a longitudinal axis with a skeletal frame formed to define an elongate chamber which extends through said body member, the body member being formed of thermal shape memory material which has been annealed at a temperature sufficient to set a memory shape for said body member and impart to said shape memory material a temperature transformation level above which said skeletal frame assumes a first expanded configuration relative to said longitudinal axis and below which said skeletal frame will be collapsible toward said longitudinal axis to a second collapsed configuration, said thermal shape memory material being formed to define a plurality of interconnected open cells forming the skeletal frame of said body member with each of said cells including two substantially parallel, spaced side portions which are substantially parallel to said longitudinal axis in both the first expanded configuration and the second collapsed configuration of said skeletal frame and end wall means extending between said side portions at an angle to said longitudinal axis, said cells being joined together only along said side portions by fusion welds formed prior to the annealing of said shape memory material.

25. The stent of claim 24 wherein the thermal shape memory material forming the side portions and end wall means of some cells in said skeletal frame has a temperature transformation level which differs from the temperature transformation level of the thermal shape memory material forming the side portions and end wall means of other cells in said skeletal frame.

26. The stent of claim 24 wherein said cell end wall means each include first and second wall sections, each said wall section having a first end joined to one of the side portions of said cell, said wall section extending at an angle to the side portion to which the first end thereof is joined, and each said wall section having a second end opposite to said first end, the second ends of said first and second wall sections being joined, said end wall means being relatively pliable when said skeletal frame is subjected to temperatures below said temperature transformation level and resiliently deformable but relatively rigid when said skeletal frame is subjected to temperatures above said temperature transformation level and operating while maintaining said cell straight side portions substantially parallel to said longitudinal axis to cause the space between the straight side portions of said cells to decrease in order to collapse said skeletal frame from the first expanded configuration to the second collapsed configuration and to cause the space between the straight side portions of said cells to increase to expand said skeletal frame from the second collapsed configuration to the first expanded configuration.

27. A stent comprising an elongate body member having a longitudinal axis and a skeletal frame formed to define an elongate chamber which extends through said body member, the body member being formed of thermal shape memory material which defines a plurality of interconnected, open cells forming the skeletal frame of said body member, each of said cells including two substantially parallel, spaced, straight side portions which are substantially parallel to said longitudinal axis and end wall means extending between said side portions at an angle to said longitudinal axis, said cells being joined together only along the lengths of said straight side portions, the shape memory material having a temperature transformation level above which said skeletal frame assumes a first expanded configuration relative to said longitudinal axis and below which said cell end wall means permit the space between straight side portions of said cell to decrease to permit movement of said straight portions toward said longitudinal axis to collapse said skeletal frame to a second collapsed configuration, said cell end wall means operating at a temperature above said temperature transformation level when said skeletal frame is in the second collapsed configuration to expand the skeletal frame to the first expanded configuration, and elastomeric sleeve means disposed around said elongate body and operating to expand when said skeletal frame assumes said first expanded configuration and to exert a compressive force on said skeletal frame in said first expanded configuration, said elastomeric sleeve means operating when said skeletal frame is at or below said transition temperature to collapse said skeletal frame to the second collapsed configuration.

28. The stent according to claim 27 wherein a first area of said skeletal frame includes cells which are larger than the cells in at least a second area of said skeletal frame, said cells in said first and second areas expanding at temperatures above said transition temperature to apply a radial force against said elastomeric sleeve means with the radial force applied by the cells in said first area being different from the radial force applied by the cells in said second area.

29. The stent of claim 27 wherein said skeletal frame, when expanded, is substantially tubular in configuration with rows of six interconnected cells defining the circumference of the frame and an even number of cells along the length of the frame.

30. A stent for insertion in a body vessel comprising an elongate body means having a longitudinal axis, a first end, a second end, and an elongate chamber extending through said body means between said first and second ends, the body means being formed of thermal shape memory material which is relatively pliable at temperatures below a transition temperature to permit said body means to be collapsed toward said longitudinal axis to a collapsed configuration for insertion in said body vessel, said thermal shape memory material operating to expand said body means radially outward from said collapsed configuration toward an expanded memory configuration in response to temperatures at or above said transition temperature to contact and apply radial force to said body vessel, said body means including a skeletal frame formed of said thermal shape memory material to define said elongate chamber, the skeletal frame including a plurality of interconnected open cells, each of which includes two substantially parallel, spaced, straight side portions which are substantially parallel to said longitudinal axis and end wall means extending between said side portions at an angle to said longitudinal axis, said cells being joined together only along the lengths of said straight side portions, said skeletal frame including a first area including cells which are designed differently from cells in at least a second area of said skeletal frame to cause different radial forces to be applied to said body vessel by said body means in the expanded memory configuration thereof.

31. The stent according to claim 30 wherein the cells in said first area of the skeletal frame are formed at a greater angle to the longitudinal axis of said body means than are the endwalls of the cells in the second area of said frame.

32. The stent according to claim 30 wherein each cell in said first area of said skeletal frame includes two substantially parallel spaced straight side portions which are spaced apart for a distance substantially equal to the distance between the substantially parallel spaced side portions of the cells in said second area of said skeletal frame, the endwall means of the cells in said first area being greater in length than the endwall means of the cells in said second area to form cells of greater length in the longitudinal direction of said body means.