Eccentric drive shaft for atherectomy device and method for manufacture

• US 6,132,444 A
• Filed: 03/19/1998
• Issued: 10/17/2000
• Est. Priority Date: 08/14/1997
• Status: Expired due to Term

• Current Assignee: Cardiovascular Systems Incorporated (Boston Scientific Corporation)
• Original Assignee: Shturman Cardiology Systems, Inc.
• Inventors: Shturman, Leonid, Nevzorov, Andrei, Spassky, Mikhail
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): Lewis, William W.
• Application Number:
  US09/044,550
• Time in Patent Office: 943 Days
• Field of Search: 606/1, 606/159, 606/170, 606/171, 606/180, 604/22, 128/898
• US Class Current: 606/159
• CPC Class Codes: A61B 17/320725 with radially expandable cutting or abrading elements A61B17/32075 takes precedence
• CPC Class Codes: A61B 17/320758 with a rotating cutting instrument, e.g. motor driven A61B17/320725, A61B17/32075 and A61B17/320783 take precedence; for removing intra-ocular material A61F9/00763; endoscopic rotatable cutting instruments A61B17/32002
• CPC Class Codes: A61B 2017/00526 Methods of manufacturing
• CPC Class Codes: A61B 2017/00553 using a turbine
• CPC Class Codes: A61B 2017/00853 low friction, hydrophobic and corrosion-resistant fluorocarbon resin coating (ptf, ptfe, polytetrafluoroethylene)
• CPC Class Codes: A61B 2017/22039 eccentric
• CPC Class Codes: A61B 2017/320004 abrasive
• CPC Class Codes: A61B 2017/320766 eccentric

Abstract

A method of manufacturing a rotational atherectomy drive shaft having an asymmetrical tissue removal section. One or more strands of wire are helically wound about an elongated mandrel having an enlarged diameter section with a predetermined shape, thereby forming an elongated, flexible drive shaft which has an enlarged diameter tissue removal section. A portion of the drive shaft, including the enlarged diameter tissue removal section, is placed into a first clamp and given a first heat treatment to give the wire turns of the enlarged diameter tissue removal section an initial set, thereby preserving the initial shape of the enlarged diameter tissue removal section of the drive shaft. The drive shaft is then removed from the first clamp and the mandrel is dissolved. The enlarged diameter section of the drive shaft is then deformed to an asymmetrical shape by placing a portion of the drive shaft, including the enlarged diameter tissue removal section, into a second clamp. The clamped portion of the drive shaft is then heat treated for a second time to give wire turns of the enlarged diameter tissue removal section a new set, thereby preserving the asymmetrical shape of the enlarged diameter section. In its asymmetrical shape the enlarged diameter tissue removal section has a longitudinally flat "side"--i.e., all wire turns of the tissue removal section may be connected by an imaginary straight line which throughout its length is parallel to the rotational axis of the drive shaft.

Claims

1. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire to form an elongated, flexible drive shaft having wire turns defining an enlarged diameter tissue removal section having an initial shape; and

deforming at least a portion of the enlarged diameter tissue removal section to a desired shape that is asymmetrical with respect to a rotational axis of the drive shaft.

2. The method of claim 1 wherein the enlarged diameter tissue removal section is helically wound to an initial shape that is symmetrical with respect to the rotational axis of the drive shaft.

3. The method of claim 1 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape an outer surface of each wire turn of the enlarged diameter tissue removal section includes a point that is collinear with a point on the outer surface of each other wire turn of the enlarged diameter tissue removal section, such points defining a straight line that is parallel to the rotational axis of the drive shaft.

4. The method of claim 1 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape all wire turns of the tissue removal section may be connected by an imaginary straight line which throughout its length is parallel to the rotational axis of the drive shaft.

5. The method of claim 1 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape each wire turn of the enlarged diameter tissue removal section includes a point on its outer surface that is spaced the same distance from the rotational axis of the drive shaft as a point on the outer surface of each other wire turn of the enlarged diameter tissue removal section of the drive shaft.

6. The method of claim 1 wherein the deforming step includes the step of placing the enlarged diameter tissue removal section into a clamp which is sized and shaped to give the enlarged diameter tissue removal section the desired asymmetrical shape.

7. The method of claim 6 further comprising the step of heat treating the enlarged diameter tissue removal section, after it has been placed in the clamp, to give the wire turns of the enlarged diameter tissue removal section a set in the desired asymmetrical shape.

8. The method of claim 6 wherein the deforming step includes the steps of:

(a) deforming the enlarged diameter tissue removal section to an asymmetrical shape by placing it in the clamp,

(b) elastically stretching the enlarged diameter tissue removal section within the clamp and then securing it in such stretched position by tightening the clamp, and

(c) heat treating the enlarged diameter tissue removal section to give the wire turns of the enlarged diameter tissue removal section a set in such stretched position.

9. The method of claim 6 wherein the deforming step includes the steps of:

(a) stretching the enlarged diameter tissue removal section sufficiently to inelastically deform at least a middle portion of the enlarged diameter section, thereby creating spaces (of a predetermined width) between the wire turns of the middle portion of the enlarged diameter tissue removal section,

(b) deforming the enlarged diameter tissue removal section to an asymmetrical shape by placing it in the clamp, and

(c) heat treating the enlarged diameter tissue removal section to give the wire turns of the enlarged diameter tissue removal section a set in such stretched position and asymmetrical shape.

10. The method of claim 7, 8 or 9 wherein the heat treatment is at a temperature of between about 230°

C. and about 600°

C. for at least about ten minutes.

11. The method of claim 7, 8 or 9 wherein the heat treatment is at a temperature of between about 360°

C. and about 600°

C. for at least about a half hour.

12. The method of claim 7, 8 or 9 wherein the heat treatment is at a temperature of between about 470°

C. and about 530°

C. for at least about half an hour.

13. The method of claim 7, 8 or 9 wherein the heat treatment is at a temperature of between about 470°

C. and about 530°

C. for at least about an hour.

14. The method of claim 7, 8 or 9 wherein the heat treatment is conducted in an inert gas environment.

15. The method of claim 14 wherein the inert gas is argon.

16. The method of claim 7, 8 or 9 wherein the heat treatment is conducted in a gas environment of SF₆.

17. The method of claim 1 further comprising the step of heat treating the drive shaft after the helically winding step and before the deforming step to give the wire turns of the drive shaft a set in the initial shape.

18. The method of claim 17 wherein the heat treatment is at a temperature of between about 230°

C. and about 600°

C. for at least about ten minutes.

19. The method of claim 17 wherein the heat treatment is at a temperature of between about 360°

C. and about 600°

C. for at least about a half hour.

20. The method of claim 17 wherein the heat treatment is at a temperature of between about 540°

C. and about 580°

C. for at least about half an hour.

21. The method of claim 17 wherein the heat treatment is at a temperature of between about 540°

C. and about 580°

C. for at least about an hour.

22. The method of claim 17 wherein the heat treatment is conducted in an inert gas environment.

23. The method of claim 22 wherein the gas is argon.

24. The method of claim 17 wherein the heat treatment is conducted in a gas environment of SF₆.

32. The method of claim 1 further comprising the step of securing several wire turns of the drive shaft to each other just distal and just proximal to the enlarged diameter section of the drive shaft.

33. The method of claim 1 wherein the winding step includes helically winding one or more strands of wire about an elongated mandrel having an enlarged diameter section with a predetermined shape, thereby forming an elongated, flexible drive shaft which has an enlarged diameter tissue removal section, defined by wire turns of the drive shaft and having an initial shape which corresponds to the shape of the enlarged diameter section of the mandrel.

34. The method of claim 33 further comprising the step of immersing at least the enlarged diameter tissue removal section of the drive shaft into an acidic solution to dissolve at least the enlarged diameter section of the mandrel from within the drive shaft.

35. The method of claim 34 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in a solution containing between about 30% and about 40% nitric acid.

36. The method of claim 35 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in the nitric acid for at least about four hours at a temperature of at least about 50°

C.

37. The method of claim 35 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in the nitric acid for at least about eight hours at a temperature of at least about 80°

C.

38. The method of claim 33 further comprising the step of immersing the entire drive shaft, including the enlarged diameter tissue removal section, in a solution of at least about 10% nitric acid for at least about four hours.

39. The method of claim 33 further comprising the step of immersing the entire drive shaft, including the enlarged diameter tissue removal section, in a solution of at least about 15% nitric acid for at least about eight hours.

40. The method of claim 34 wherein the drive shaft wire and at least the enlarged diameter section of the mandrel are made from different metals, the metal of the enlarged diameter section of the mandrel being dissolvable in nitric acid without substantially adversely affecting the wire of the drive shaft.

41. The method of claim 34 wherein the enlarged diameter section of the mandrel is made from brass, and the drive shaft wire is made from stainless steel.

42. The method of claim 34 wherein the mandrel includes a round mandrel shaft to which the enlarged diameter section is secured, the mandrel shaft being made from high carbon steel.

81. The method of claim 34 wherein the acidic solution is a solution including nitric acid.

25. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire to form an elongated, flexible drive shaft having wire turns defining an enlarged diameter tissue removal section having an initial shape;

deforming at least a portion of the enlarged diameter tissue removal section to a desired shape that is asymmetrical with respect to a rotational axis of the drive shaft; and

forming an abrasive surface on at least a portion of the enlarged diameter tissue removal section.

26. The method of claim 25 wherein the abrasive surface is formed only on a portion of the enlarged diameter tissue removal section, thereby defining an abrasive segment of the enlarged diameter section of the drive shaft.

27. The method of claim 26 wherein the abrasive segment extends only part of the way around the enlarged diameter tissue removal section of the drive shaft.

28. The method of claim 25 wherein the abrasive surface is formed after the enlarged diameter tissue removal section has been deformed to the desired shape.

29. The method of claim 25 wherein the step of forming the abrasive surface includes securing abrasive particles with a bonding material to outer surfaces of at least some of the wire turns of the enlarged diameter section.

30. The method of claim 29 wherein the bonding material is gold, platinum, iridium or alloys made therefrom.

31. The method of claim 29 further comprising the step of longitudinally stretching the enlarged diameter section to create spaces between at least some of the wire turns before securing abrasive particles to the wire turns so that the abrasive particle bonding material may be applied to the wire turns without securing the wire turns to each other.

43. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire to form an elongated, flexible drive shaft having wire turns defining an enlarged diameter tissue removal section having an initial shape;

deforming the enlarged diameter tissue removal section by placing it into a clamp that is shaped and sized to give the enlarged diameter tissue removal section a desired asymmetrical shape; and

heat treating the enlarged diameter tissue removal section to give the wire turns of the enlarged diameter tissue removal section a set in a desired final asymmetrical shape.

44. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire to form an elongated, flexible drive shaft having wire turns which define an enlarged diameter tissue removal section having an initial shape;

deforming the enlarged diameter tissue removal section to a desired shape that is asymmetrical with respect to a rotational axis of the drive shaft; and

heat treating the deformed enlarged diameter tissue removal section so that the tissue removal section retains the desired shape.

45. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire to form an elongated, flexible drive shaft having wire turns which define an enlarged diameter tissue removal section having an initial shape;

deforming the enlarged diameter tissue removal section to a desired shape in which the center of mass of the enlarged diameter tissue removal section is spaced away from a rotational axis of the drive shaft; and

heat treating the deformed enlarged diameter tissue removal section so that the tissue removal section retains the desired shape.

46. A method of manufacturing a drive shaft having an asymmetrical tissue removal section comprising the steps of:

helically winding one or more strands of wire about an elongated mandrel having an enlarged diameter section with a predetermined shape, thereby forming an elongated, flexible drive shaft which has an enlarged diameter tissue removal section defined by wire turns of the drive shaft and having an initial shape which corresponds to the shape of the enlarged diameter section of the mandrel;

placing a portion of the drive shaft, including the enlarged diameter tissue removal section, into a first clamp and heat treating that portion of the drive shaft (the "first heat treatment") to give the wire turns of the enlarged diameter tissue removal section an initial set, thereby preserving the initial shape of the enlarged diameter tissue removal section of the drive shaft;

removing the drive shaft from the first clamp and immersing at least the enlarged diameter tissue removal section of the drive shaft into an acidic solution to dissolve at least the enlarged diameter section of the mandrel from within the drive shaft;

deforming the enlarged diameter section of the drive shaft to an asymmetrical shape by placing a portion of the drive shaft, including the enlarged diameter tissue removal section, into a second clamp; and

heat treating the clamped portion of the drive shaft (the "second heat treatment") to give wire turns of the enlarged diameter tissue removal section a set, thereby preserving the asymmetrical shape of the enlarged diameter section.

47. The method of claim 46 wherein the enlarged diameter tissue removal section is helically wound to the initial shape that is symmetrical with respect to the rotational axis of the drive shaft.

48. The method of claim 46 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape an outer surface of each wire turn of the enlarged diameter tissue removal section includes a point that is collinear with a point on the outer surface of each other wire turn of the enlarged diameter tissue removal section, such points defining a straight line that is parallel to the rotational axis of the drive shaft.

49. The method of claim 46 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape all wire turns of the tissue removal section may be connected by an imaginary straight line which throughout its length is parallel to the rotational axis of the drive shaft.

50. The method of claim 46 wherein the enlarged diameter tissue removal section is deformed so that in its desired shape each wire turn of the enlarged diameter tissue removal section includes a point on its outer surface that is spaced the same distance from the rotational axis of the drive shaft as a point on the outer surface of each other wire turn of the enlarged diameter tissue removal section of the drive shaft.

51. The method of claim 46 wherein each heat treatment is at a temperature of between about 230°

C. and about 600°

C. for at least about ten minutes.

52. The method of claim 46 wherein each heat treatment is at a temperature of between about 360°

C. and about 600°

C. for at least about a half hour.

53. The method of claim 46 wherein the first heat treatment is at a temperature of between about 540°

C. and about 580°

C. for at least about half an hour.

54. The method of claim 46 wherein the first heat treatment is at a temperature of between about 540°

C. and about 580°

C. for at least about an hour.

55. The method of claim 46 wherein the second heat treatment is at a temperature of between about 470°

C. and about 530°

C. for at least about half an hour.

56. The method of claim 46 wherein the second heat treatment is at a temperature of between about 470°

C. and about 530°

C. for at least about an hour.

57. The method of claim 46 wherein each heat treatment is conducted in an inert gas environment.

58. The method of claim 57 wherein the inert gas is argon.

59. The method of claim 46 wherein each heat treatment is conducted in a gas environment of SF₆.

60. The method of claim 46 wherein the drive shaft wire and at least the enlarged diameter section of the mandrel are made from different metals, the metal of the enlarged diameter section of the mandrel being dissolvable in an acid without substantially adversely affecting the wire of the drive shaft.

61. The method of claim 60 wherein the metal of the enlarged diameter section of the mandrel is dissolvable in nitric acid.

62. The method of claim 46 wherein the enlarged diameter section of the mandrel is made from brass, and the drive shaft wire is made from stainless steel.

63. The method of claim 46 wherein the mandrel includes a round mandrel shaft to which the enlarged diameter section is secured, the mandrel shaft being made from high carbon steel.

64. The method of claim 46 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in a solution containing between about 30% and about 40% nitric acid.

65. The method of claim 64 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in the nitric acid for at least about four hours at a temperature of at least about 50°

C.

66. The method of claim 64 wherein the enlarged diameter tissue removal section of the drive shaft is immersed in the nitric acid for at least about eight hours at a temperature of at least about 80°

C.

67. The method of claim 46 further comprising the step of immersing the entire drive shaft, including the enlarged diameter tissue removal section, in a solution of at least about 10% nitric acid for at least about four hours.

68. The method of claim 46 further comprising the step of immersing the entire drive shaft, including the enlarged diameter tissue removal section, in a solution of at least about 15% nitric acid for at least about eight hours.

69. The method of claim 46 wherein the entire drive shaft is immersed in the acidic solution to remove the mandrel from within the drive shaft.

70. The method of claim 46 further comprising the step of heat treating the entire drive shaft at a temperature of between about 200°

C. and about 400°

C.

71. The method of claim 70 wherein the 200°

C.-400°

C. heat treatment is conducted after the second heat treatment.

72. The method of claim 46 further comprising the step of heat treating the entire drive shaft at a temperature of between about 250°

C. and about 350°

C.

73. The method of claim 46 further comprising the step of forming an abrasive surface on at least a portion of the enlarged diameter tissue removal section of the drive shaft.

74. The method of claim 73 wherein abrasive surface is formed only on a portion of the enlarged diameter tissue removal section, thereby defining an abrasive segment of the enlarged diameter section of the drive shaft.

75. The method of claim 74 wherein the abrasive segment extends only part of the way around the enlarged diameter tissue removal section of the drive shaft.

76. The method of claim 73 wherein the step of forming the abrasive surface includes securing abrasive particles with a bonding material to outer surfaces of at least some of the wire turns of the enlarged diameter section.

77. The method of claim 76 wherein the bonding material is gold, platinum, iridium or alloys made therefrom.

78. The method of claim 76 further comprising the step of longitudinally stretching the enlarged diameter section to create spaces between at least some of the wire turns before securing abrasive particles to the wire turns so that the abrasive particle bonding material may be applied to the wire turns without securing the wire turns to each other.

79. The method of claim 46 wherein the deforming step includes the steps of:

(a) deforming the enlarged diameter tissue removal section to an asymmetrical shape by placing it in the second clamp,

(b) elastically stretching the enlarged diameter tissue removal section within the second clamp and then securing it in such stretched position by tightening the second clamp, and

(c) heat treating the enlarged diameter tissue removal section to give the wire turns of the enlarged diameter tissue removal section a set in such stretched position.

80. The method of claim 46 wherein the deforming step includes the steps of:

(a) stretching the enlarged diameter tissue removal section sufficiently to inelastically deform at least a middle portion of the enlarged diameter section, thereby creating spaces (of a predetermined width) between the wire turns of the middle portion of the enlarged diameter tissue removal section,

(b) deforming the enlarged diameter tissue removal section to an asymmetrical shape by placing it in the second clamp, and

(b) heat treating the enlarged diameter tissue removal section to give the wire turns of the enlarged diameter tissue removal section a set in such stretched position and asymmetrical shape.