Flexible and conformable stent and method of forming same

• US 20040024444A1
• Filed: 07/31/2002
• Published: 02/05/2004
• Est. Priority Date: 07/31/2002
• Status: Active Grant

• Current Assignee: Union Theapeutics A/S
• Original Assignee: Union Theapeutics A/S
• Inventors: Moore, Brian E.
• Granted Patent: US 7,025,777 B2
• Time in Patent Office: Days
• US Class Current: 623/1.15
• CPC Class Codes: A61F 2/915 with bands having a meander structure, adjacent bands being connected to each other
• CPC Class Codes: A61F 2002/91533 characterised by the phase between adjacent bands
• CPC Class Codes: A61F 2002/91558 connected peak to peak
• CPC Class Codes: A61F 2002/91575 connected peak to trough
• CPC Class Codes: A61F 2230/0054 V-shaped
• CPC Class Codes: A61F 2250/0036 differing in thickness

Abstract

An expandable stent is fabricated from a plurality of circumferential rings, each pair of adjacent circumferential rings being interconnected by a multiplicity of links, each link contacting a portion of a strut in one ring along one longitudinal axis and a portion a strut in a directly adjacent ring along a different longitudinal axis. Each link is circumferentially S-shaped and adjacent links are mirror images of each other. The resulting stent is both flexible and strong when expanded thereby providing good scaffolding. In one embodiment, the strut material is fabricated of shape memory alloy such that when the strut is compressed so as to be insertable into a vessel, the strut will automatically expand to its previous dimension upon rising to the temperature of the vessel in which it is placed, thereby to expand and hold open the vessel without need for a balloon catheter.

Claims

1. An unexpanded stent comprising:

a plurality of radially expandable undulating rings, each radially expandable undulating ring comprising a strut with a plurality of apices;

a plurality of arcuate flex members connecting adjacent first and second radially expandable undulating rings;

the first radially expandable undulating ring comprises a strut with more than one complete sinusoidal cycle of strut material which is coupled to two circumferentially adjacent arcuate flex members; and

the second radially expandable undulating ring comprises a strut with less than one complete sinusoidal cycle of the strut material being coupled to said two circumferentially adjacent arcuate flex members, wherein said arcuate flex members are not connected to a common sinusoidal portion of either of said first or second undulating rings.

2. The stent of claim 1, wherein each arcuate flex member comprises an S-shaped member.

3. The stent of claim 2, wherein the S-shaped member comprises a first apex in substantial longitudinal alignment with an apex of a strut in one of said plurality of radially expandable undulating rings.

4. The stent of claim 2, wherein the S-shaped member comprises a second apex in substantial longitudinal alignment with an apex of a strut in a second of said plurality of radially expandable undulating rings.

5. The stent of claim 2, wherein the S-shaped member comprises a first apex and a second apex, each of the first apex and the second apex in substantial longitudinal alignment with an apex of the first and second expandable undulating rings.

6. The stent of claim 1, wherein adjacent first and second radially expandable undulating rings are disposed with respect to one another along the stent such that apices in each of the first and second radially expandable undulating rings are in longitudinal alignment.

7. The stent of claim 1, wherein the flex member connects longitudinally unaligned apices of the struts comprising adjacent first and second radially expandable undulating rings.

8. The stent of claim 1, further comprising a biocompatible surface treatment or coating thereon.

9. The stent of claim 1, further comprising a medicinal agent included in or applied to the undulating rings and the arcuate flex numbers.

10. The stent of claim 1, wherein the plurality of radially expandable undulating rings and the plurality of arcuate flex members are constructed of a plastically deformable material wherein an expansion of said stent to a deployment diameter involves substantially plastic deformation.

11. The stent of claim 1, wherein the plurality of radially expandable undulating rings and the plurality of arcuate flex members are constructed of a material wherein an expansion of said stent to a deployment diameter involves substantially elastic deformation.

12. The stent of claim 1, wherein the plurality of radially expandable undulating rings and the plurality of arcuate flex members are constructed of stainless steel.

13. The stent of claim 1, wherein the plurality of radially expandable undulating struts and the plurality of arcuate flex members are constructed of a shape memory material.

14. The stent of claim 1, wherein the plurality of radially expandable undulating rings and the plurality of arcuate flex members are constructed of nitinol.

53. The stent of claim 1 wherein the plurality of radially expanding undulating rings and the plurality of arcuate flex members comprise a bio-absorbable material.

54. The stent of claim 53 wherein the bio-absorbable material is poly-L-lactic acid.

55. The stent of claim 14 wherein the first and second radially expanding undulating rings and the mirrored pair of first and second arcuate flex members.

56. The stent of claim 55 wherein said bio-absorbable material is poly-L-lactic acid.

15. A stent comprising:

a first radially expandable undulating ring comprising a first apex and a second apex;

a second radially expandable undulating ring comprising a third apex and a fourth apex longitudinally unaligned with respect to the first and second apices;

a mirrored pair of first and second arcuate flex members wherein the first arcuate flex member interconnects the first apex and the third apex, and the second arcuate flex member connects the second and the fourth apex.

16. The stent of claim 15, wherein the first radially expandable undulating strut and the second radially expandable undulating strut are connected by a plurality of arcuate flex members.

17. The stent of claim 16, wherein the first radially expandable undulating ring comprises more than one complete sinusoidal cycle which is coupled to two radially adjacent arcuate flex members.

18. The stent of claim 16, wherein the second radially expandable undulating ring comprises less than one complete sinusoidal cycle which is coupled to two radially adjacent arcuate flex members.

19. The stent of claim 16, wherein:

(i) the first radially expandable undulating ring comprises more than one complete sinusoidal cycle which is coupled to two circumferentially adjacent arcuate flex members, and (ii) the second radially expandable undulating ring comprises less than one complete sinusoidal cycle which is coupled to two circumferentially adjacent arcuate flex members.

20. The stent of claim 15, wherein the arcuate flex members comprise S-shaped members.

21. The stent of claim 20, wherein the S-shaped member comprises a first apex in substantial longitudinal alignment with apices of the plurality of radially expandable undulating struts.

22. The stent of claim 20, wherein the S-shaped member comprises a second apex in substantial longitudinal alignment with apices of the plurality of radially expandable undulating rings.

23. The stent of claim 20, wherein the S-shaped member comprises a first apex and a second apex, each of the first apex and the second apex in substantial longitudinal alignment with apices of the plurality of radially expandable undulating rings.

24. The stent of claim 15, wherein adjacent first and second radially expandable undulating struts are disposed such that longitually aligned apices in each of the first and second radially expandable undulating rings are pointed in the same direction.

25. The stent of claim 15, further comprising a biocompatible surface treatment or coating thereon.

26. The stent of claim 15, further comprising a medicinal agent included in or applied to the surface of the undulating rings and arcuate flex members.

27. The stent of claim 15, wherein the plurality of radially expandable undulating rings and a plurality of arcuate flex members are constructed of a material, wherein an expansion of said stent to a deployment diameter involves substantially plastic deformation.

28. The stent of claim 15, wherein the plurality of radially expandable undulating rings and a plurality of arcuate flex members are constructed of a material wherein an expansion of said stent to a deployment diameter involves substantially elastic deformation.

29. The stent of claim 15, wherein the first radially expandable undulating ring, the second radially expandable undulating ring and the arcuate flex members comprise stainless steel.

30. The stent of claim 15, wherein the first radially expandable undulating ring, the second radially expandable undulating ring and the arcuate flex members comprise a shape memory material.

31. The stent of claim 15, wherein the first radially expandable undulating ring, the second radially expandable undulating ring and the arcuate flex members comprise nitinol.

32. A stent of generally cylindrical shape having a longitudinal center axis running the length of the stent, comprising in the unexpanded state;

a plurality of rings, each ring made up of a multiplicity of “

U”

shaped sections, each “

U”

having an end section and two relatively straight arms, with adjacent “

U'"'"'s”

in the ring facing in opposite directions and with each “

U”

sharing an arm with the two directly adjacent “

U'"'"'s” and

with each arm of each U being approximately parallel to said longitudinal center axis;

a number of links connecting each ring to an adjacent ring, each link comprising;

a first section generally parallel to said longitudinal axis and connecting to the end section of a selected “

U”

in the first ring at a point on a first longitudinal line on the surface of said stent, said first longitudinal line being parallel to said axis,

a second section generally parallel to said longitudinal axis and connecting to the end section of a selected “

U”

in the adjacent ring, said connection to the end section of the selected “

U”

in the adjacent ring being on a second longitudinal line on the surface of said stent, said second longitudinal line being parallel to said axis and offset from said first longitudinal line, and

an “

S”

shaped section connecting said first section to said second section;

wherein each link in each pair of links in a multiplicity of links connecting a pair of rings has its first section and second section each connected to an apex to which no other link is connected.

33. The stent of claim 32, wherein the end section is curved.

34. The stent of claim 32 wherein the end section is approximately straight.

35. The stent as in claim 32, wherein the arms of each “

U”

in the unexpanded stent are such that the distal ends of the two arms relative to the end portion of the “

U”

are closer to each other than the proximal ends of the two arms connected to the end portion of the “

U”

.

36. The stent as in claim 32 wherein said “

S”

shaped section is such that the “

S”

shaped section extends circumferentially between the two adjacent rings being connected by said link.

37. The stent as in claim 32 wherein adjacent links connecting the same pair of rings are mirror images of each other.

38. The stent as in claim 37, wherein each link is capable of expanding as the stent expands such that the “

S”

shaped section becomes gradually straight.

39. The stent as in claim 38, wherein each link is capable of expanding such that the angle between the expanded “

S”

shaped section and the first section is greater than 90° and

the angle between the expanded “

S”

shaped section and the second section is greater than 90°

.

40. The method of making an unexpanded stent comprising:

forming a plurality of radially expandable undulating rings, each radially expandable undulating ring comprising a strut with a plurality of apices;

forming a plurality of arcuate flex members connecting adjacent first and second radially expandable undulating rings;

coupling more than one complete sinusoidal cycle of strut material in the first radially expandable undulating ring to two circumferentially adjacent arcuate flex members; and

coupling less than one complete sinusoidal cycle of the strut material in the second radially expandable undulating ring to said two circumferentially adjacent arcuate flex members.

41. The method of claim 40, wherein forming a plurality of arcuate flex members comprises forming each arcuate flex member into an S-shaped member.

42. The method of claim 41, wherein each S-shaped member is formed to have a first apex in substantial longitudinal alignment with an apex of the strut in one of said plurality of radially expandable undulating rings.

43. The method of claim 41, wherein each S-shaped member is formed to have a second apex in substantial longitudinal alignment with an apex of the strut in a second of said plurality of radially expandable undulating rings.

44. The method of claim 41, wherein each S-shaped member is formed to have a first apex and a second apex, each of the first apex and the second apex being in substantial longitudinal alignment with apices of the struts of the plurality of radially expandable undulating rings.

45. The method of claim 40, wherein forming a plurality of radially expandable undulating rings comprises forming adjacent first and second radially expandable undulating rings disposed with respect to one another along the stent such that apices in each of the first and second radially expandable undulating rings are in longitudinal alignment.

46. The method of claim 40, wherein forming a plurality of arcuate flex members comprises forming each flex member to connect longitudinally unaligned apices of the struts comprising adjacent first and second radially expandable undulating rings.

47. The method of claim 40, further comprising:

forming a biocompatible coating on said plurality of radially expandable undulating rings and on said plurality of arcuate flex members.

48. The method of claim 40, further comprising;

forming a medicinal coating on said plurality of radially expandable undulating rings and on said plurality of arcuate flex members.

49. The method of claim 40, further comprising:

forming the plurality of radially expandable undulating rings and the plurality of arcuate flex members of a plastically deformable material.

50. The method of claim 40, further comprising:

forming the plurality of radially expandable undulating rings and the plurality of arcuate flex members of stainless steel.

51. The method of claim 40, further comprising:

forming the plurality of radially expandable undulating struts and the plurality of arcuate flex members of a shape memory material.

52. The method of claim 40, further comprising:

forming the plurality of radially expandable undulating rings and the plurality of arcuate flex members of nitinol.