Stent and method for manufacturing such a stent

• US 6,240,978 B1
• Filed: 11/02/1999
• Issued: 06/05/2001
• Est. Priority Date: 07/17/1997
• Status: Expired due to Term

• Current Assignee: Boston Scientific Corporation
• Original Assignee: Schneider Electric SE
• Inventors: Gianotti, Marc
• Primary Examiner(s): Hughes, S. Thomas
• Assistant Examiner(s): Cozart, Jermie E.
• Application Number:
  US09/431,988
• Time in Patent Office: 581 Days
• Field of Search: 294/47, 294/52, 623/1, 623/1.15, 623/1.18, 623/1.19, 623/1.2, 623/1.22, 606/194, 148/580, 148/402, 140/107, 140/108, 723/421
• US Class Current: 140/107
• CPC Class Codes: A61F 2/88 the wire-like elements formed as helical or spiral coils forming a net-like or mesh-like structure A61F2/90
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2002/3011 Cross-sections or two-dimensional shapes
• CPC Class Codes: A61F 2230/0002 Two-dimensional shapes, e.g. cross-sections
• CPC Class Codes: D04C 1/06 Braid or lace serving particular purposes
• CPC Class Codes: D04C 3/48 Auxiliary devices
• CPC Class Codes: D10B 2403/0241 enhancing mechanical properties
• CPC Class Codes: D10B 2509/06 Vascular grafts; stents
• CPC Class Codes: Y10T 29/49874 Prestressing rod, filament or strand

Abstract

A prosthetic stent with a tubular wall having local inwardly or outwardly formed elevations. Stents having such elevations have a higher mechanical stability if bend according to the curvature of the body vessels to be supported or repaired. Also a method for manufacturing a stent with such elevations is described.

Claims

1. A method for manufacturing a stent comprising:

(a) providing an elongated mandrel having an outer diameter and at least one local outwardly bound elevation;

(b) forming an elongated metallic tubular braid having proximal and distal ends, the braid having an inner diameter commensurate with the outer diameter of the mandrel;

(c) engaging the tubular braid over the mandrel, thereby forming an outwardly extending relief in the elongated metallic tubular braid along a portion of the tubular braid overlying the outwardly bound elevation;

(d) heating the tubular braid while it is engaged over the mandrel;

(e) cooling the tubular braid; and

(f) disengaging the braid from the mandrel.

2. The method of claim 1 wherein prior to disengaging the braid from the mandrel the braid is compressed in an axial direction.

3. The method of claim 1 wherein the steps of heating and cooling the tubular braid are performed under a vacuum condition.

4. The method of claim 1 wherein the tubular braid is made of spring steel.

5. A process for fabricating a stent, including:

providing a mandrel having a generally cylindrical outer surface, and at least one discontinuity in said outer surface selected from the group of discontinuities consisting of an outwardly bound elevation and an inwardly bound elevation;

providing a mesh structure having a generally cylindrical inner surface commensurate with the outer surface of the mandrel;

causing the mesh structure to engage the mandrel in surrounding relation to the mandrel such that the mesh structure substantially conforms to the outer surface of the mandrel and thereby incorporates a relief commensurate with the discontinuity, wherein the relief is formed as an outwardly extending relief when the discontinuity is an outwardly bound elevation, and is formed as an inwardly extending relief when the discontinuity is an inwardly bound elevation;

heating the mesh structure while the mesh structure is so engaged with the mandrel; and

after said heating, cooling the mesh structure.

6. The process of claim 5 wherein:

said discontinuity comprises an outwardly bound elevation in the mandrel, whereby said causing the mesh structure to engage the mandrel comprises forming the relief as an outwardly extending relief.

7. The process of claim 6 wherein:

said at least one outwardly bound elevation is helical, whereby said causing the mesh structure to engage the mandrel comprises forming at least one helical outwardly extending relief in the mesh structure.

8. The process of claim 7 wherein:

said providing a mesh structure comprises forming a tubular braid.

9. The process of claim 8 wherein:

said providing the mesh structure further comprises braiding pluralities of first and second wires helically in respective first and second different directions at respective first and second pitch angles to form multiple crossing points of one of the first wires and one of the second wires.

10. The process of claim 9 further comprising:

causing the mesh structure to engage the mandrel with at least selected ones of said crossing points aligned with the outwardly bound elevation, whereby the outwardly extending relief of the tubular braid incorporates said crossing points.

11. The process of claim 10 wherein:

the outwardly extended relief has a third pitch angle different from the first pitch angle and the second pitch angle.

12. The process of claim 5 wherein:

the discontinuity comprises a plurality of outwardly bound elevations, whereby said causing the mesh structure to engage the mandrel comprises forming a plurality of outwardly extended reliefs in the mesh structure.

13. The process of claim 12 wherein:

the outwardly bound elevations are arranged circumferentially about the mandrel, whereby said causing the mesh structure to engage the mandrel comprises forming a plurality of circumferential outwardly extending reliefs in the mesh structure.

14. The process of claim 12 wherein:

the outwardly bound elevations extend axially along the mandrel, whereby said causing the mesh structure to engage the mandrel comprises forming a plurality of axially extended and outwardly extended reliefs in the mesh structure.

15. The process of claim 5 wherein:

said providing the mesh structure comprises intertwining pluralities of first and second wires at predetermined first and second pitch angles.

16. The process of claim 15 wherein:

said discontinuity comprises a helical outwardly bound elevation formed at a third pitch angle different from the first and second pitch angles.

17. The process of claim 16 wherein:

the third pitch angle is less than the first and second pitch angles, whereby said causing the mesh structure to engage the mandrel comprises forming an elevation pattern in said mesh structure having a fourth pitch angle less than the first and second pitch angles and substantially the same as the third pitch angle.

18. The process of claim 5 wherein:

said heating the mesh structure comprises maintaining the mesh structure at a selected process temperature for a predetermined period of time.

19. The process of claim 18 wherein:

said mesh structure is formed of stainless steel wires, said selected temperature is 550°

C., and the predetermined time is about two hours.

20. The process of claim 18 wherein:

said heating of the mesh structure is carried out under vacuum conditions.

21. The process of claim 20 wherein:

said cooling of the mesh structure is performed under vacuum conditions.

22. The process of claim 5 further including:

after said cooling of the mesh structure, disengaging the mesh structure from the mandrel.

23. The process of claim 22 wherein:

the mesh structure is enlargeable radially, and said disengaging the mesh structure from the mandrel comprises radially enlarging the mesh structure.

24. The process of claim 23 wherein:

the mesh structure is radially enlargeable responsive to an axial compression thereof and radially contractible responsive to an axial elongation thereof, and said disengaging the mesh structure from the mandrel comprises axially compressing the mesh structure.

25. A process for selectively shaping a prosthesis, including:

providing a cylindrical prosthesis structure;

placing the cylindrical prosthesis structure onto a mandrel having a generally cylindrical outer surface including at least one discontinuity in the surface, selected from the group of discontinuities consisting of an outwardly bound elevation and an inwardly bound elevation, to form the cylindrical prosthesis structure into a selected shape determined by a substantially conforming relation to the outer surface of the mandrel, wherein a portion of the cylindrical prosthesis structure overlying the discontinuity is formed as an outwardly extending relief when the discontinuity is an outwardly bound elevation, and is formed as an inwardly extending relief when the discontinuity is an inwardly bound elevation;

heating the cylindrical prosthesis structure while the cylindrical structure is disposed on the mandrel in said substantially conforming relation; and

allowing the cylindrical prosthesis structure to cool after said heating.

26. The process of claim 25 further including:

removing the cylindrical prosthesis structure from the mandrel after allowing the cylindrical structure to cool.

27. The process of claim 26 wherein:

the cylindrical prosthesis structure is adapted to undergo radial enlargement in conjunction with an axial shortening thereof, and radial contraction in response to an axial elongation thereof, and said removing the cylindrical structure comprises axially compressing the cylindrical structure.

28. The process of claim 25 wherein:

the surface discontinuity comprises at least one outwardly bound helical elevation, whereby said placing the cylindrical prosthesis structure onto the mandrel comprises forming at least one outwardly extending helical relief in the cylindrical structure.

29. The process of claim 25 wherein:

the discontinuity comprises an outwardly bound elevation, whereby said placing the cylindrical prosthesis structure onto the mandrel comprises forming in the cylindrical prosthesis structure an outwardly extending relief.

30. The process of claim 29 wherein:

the discontinuity comprises a plurality of outwardly bound elevations, whereby said placing the cylindrical prosthesis structure onto the mandrel comprises forming the cylindrical structure a plurality of elevation patterns.

31. The process of claim 30 wherein:

the outwardly bound elevations extend circumferentially about the mandrel.

32. The process of claim 30 wherein:

the outwardly bound elevations extend axially along the mandrel.

33. The process of claim 25 wherein:

the cylindrical prosthesis structure comprises first and second pluralities of wires helically wound in respective first and second different directions to form multiple crossing points of one of the first wires and one of the second wires; and

said placing of the cylindrical structure onto the mandrel comprises aligning selected ones of the crossing points with the discontinuity whereby said overlying portion of the prosthesis structure incorporates the selected crossing points.

34. The process of claim 33 wherein:

the discontinuity comprises at least one outwardly bound elevation disposed helically about the mandrel at a first pitch angle, and the first and second wires are wound helically at second and third pitch angles greater than the first pitch angle.

35. The process of claim 25 wherein:

said heating of the mesh structure is conducted under vacuum conditions.

36. The process of claim 35 wherein:

said allowing the mesh structure to cool after heating occurs under vacuum conditions.

37. A process for fabricating a stent, including:

providing a mandrel having a generally cylindrical outer surface, and at least one helical discontinuity in said outer surface;

providing a mesh structure having a generally cylindrical inner surface commensurate with the outer surface of the mandrel;

causing the mesh structure to engage the mandrel in surrounding relation to the mandrel such that the mesh structure substantially conforms to the outer surface of the mandrel and thereby incorporates a helical relief commensurate with said discontinuity;

heating the mesh structure while the mesh structure is so engaged with the mandrel; and

after said heating, cooling the mesh structure.

38. The process of claim 37 wherein:

said helical discontinuity comprises an outwardly bound helical elevation, whereby said causing the mesh structure to engage the mandrel comprises forming said relief as a helical outwardly extending relief.

39. A process for selectively shaping a prosthesis, including:

providing a cylindrical structure;

placing the cylindrical structure onto a mandrel having a generally cylindrical outer surface including a discontinuity comprising an outwardly bound elevation in said surface, to form the cylindrical structure into a selected shape determined by a substantially conforming relation to said outer surface of the mandrel in which a portion of the cylindrical structure overlying the outwardly bound elevation is shaped as an outwardly extending helical relief;

heating the cylindrical structure while the cylindrical structure is disposed on the mandrel in said substantially conforming relation; and

allowing the cylindrical structure to cool after said heating.

40. A process for selectively shaping a prosthesis, including:

providing a cylindrical mesh structure comprising at least one first wire and at least one second wire helically wound in respective first and second different directions and at respective first and second pitch angles to form multiple crossing points;

placing the cylindrical mesh structure onto a mandrel having a generally cylindrical outer surface including a discontinuity in the surface, to form the cylindrical structure into a selected shape determined by a substantially conforming relation to the outer surface of the mandrel, and further disposing selected ones of the crossing points of the mesh structure in overlying relation to the discontinuity whereby the mesh structure comprises an elevation pattern commensurate with the discontinuity and incorporating the selected crossing points;

heating the cylindrical mesh structure while the cylindrical mesh structure is disposed on the mandrel in said substantially conforming relation; and

allowing the cylindrical structure to cool after said heating.

41. The process of claim 40 wherein:

the discontinuity is disposed helically about the mandrel at a third pitch angle different from the first pitch angle and the second pitch angle.

42. The process of claim 40 wherein:

the discontinuity is selected from the group of discontinuities consisting of an outwardly bound elevation and an inwardly bound elevation.