Process for making stent graft with braided polymeric sleeve

• US 6,500,203 B1
• Filed: 05/27/1999
• Issued: 12/31/2002
• Est. Priority Date: 01/23/1997
• Status: Expired due to Fees

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Inventors: Du, George W., Thompson, Paul J.
• Primary Examiner(s): Aftergut, Jeff H.
• Application Number:
  US09/321,181
• Time in Patent Office: 1,314 Days
• Field of Search: 623/1.13, 156/149, 156/172, 156/293, 156/148, 156/294
• US Class Current: 623/1.13
• CPC Class Codes: A61F 2/0077 Special surfaces of prostheses, e.g. for improving ingrowth A61F2/30767 takes precedence
• CPC Class Codes: A61F 2/07 Stent-grafts
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2002/072 Encapsulated stents, e.g. wire or whole stent embedded in lining
• CPC Class Codes: A61F 2002/075 the stent being loosely attached to the graft material, e.g. by stitching
• CPC Class Codes: A61F 2002/3008 radio-opaque, e.g. radio-opaque markers
• CPC Class Codes: A61F 2002/30448 using adhesives
• CPC Class Codes: A61F 2210/0076 multilayered, e.g. laminated structures
• CPC Class Codes: A61F 2220/005 using adhesives
• CPC Class Codes: A61F 2220/0075 sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2240/001 Designing or manufacturing processes
• CPC Class Codes: A61F 2250/0098 radio-opaque, e.g. radio-opaque markers
• CPC Class Codes: B29C 35/02 Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mouldcold vulcanisation B29C35/18 ; vulcanising tyres, presses therefor B29D30/0601
• CPC Class Codes: B29C 53/58 helically
• CPC Class Codes: B29C 63/18 using tubular layers or sheathings B29C63/26 and B29C63/38 take precedence; placing tubular labels around rigid containers B65C3/065
• CPC Class Codes: B29D 23/001 Pipes; Pipe joints pleated hoses B29D23/18
• CPC Class Codes: B29K 2105/0827 Braided fabrics
• CPC Class Codes: B29K 2105/0845 Woven fabrics
• CPC Class Codes: B29K 2223/065 HDPE, i.e. high density polyethylene
• CPC Class Codes: B29K 2223/12 PP, i.e. polypropylene
• CPC Class Codes: B29K 2227/18 : PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2267/00 : Use of polyesters or derivatives thereof as reinforcement
• CPC Class Codes: B29K 2271/00 : Use of polyethers , e.g. PEEK, i.e. polyether-etherketone or PEK, i.e. polyetherketone or derivatives thereof, as reinforcement
• CPC Class Codes: B29K 2275/00 : Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as reinforcement
• CPC Class Codes: B29K 2281/06 : PSU, i.e. polysulfones or derivatives thereof; PES, i.e. polyethersulfones, or derivatives thereof
• CPC Class Codes: B29L 2023/007 : Medical tubes other than catheters catheters B29L2031/7542
• CPC Class Codes: D04C 1/06 : Braid or lace serving particular purposes
• CPC Class Codes: D10B 2509/06 : Vascular grafts; stents

Abstract

A stent graft for transluminal implantation includes a resilient tubular interbraided latticework of metal or polymeric monofilaments, a tubular interbraided sleeve of polymeric multifilament yarns, and an adhesive layer between the sleeve and latticework for bonding them together. The monofilaments and multifilament yarns are arranged in respective sets of axially spaced apart and oppositely directed helices, concentric on a common axis of the stent graft. The respective braid angles of the monofilaments and multifilament yarns are carefully matched to ensure that the latticework and sleeve behave according to substantially the same relationship governing the amount of radial reduction that accompanies a given axial elongation. According to a process for fabricating the stent graft, the latticework and sleeve are braided and thermally set independently, then bonded to one another by a silicone polymer adhesive applied evenly to the latticework in a liquid spray that also incorporates an organic solvent. Especially preferred yarns are composed of essentially untwisted filaments that define non-circular yarn cross sections. Alternative stent graft constructions feature exterior and interior sleeves on opposite sides of the latticework, two or more sleeves axially spaced from one another on the same latticework, a latticework formed of a recovery metal, and a plastically deformable latticework.

Claims

1. A process for making a medical device, including:

braiding a plurality of structural strands into a tubular open latticework in which the strands form multiple first intersections and define a first braid angle when in a nominal state, wherein the structural strands along the length of the tubular open latticework are free of bonding to one another at the first intersections, said tubular open latticework being adjustable between the nominal state and a radially-reduced axially-elongated state according to a first relationship of radial reduction versus axial elongation;

braiding a plurality of compliant textile strands into a tubular sleeve in which the textile strands form multiple second intersections and define a second braid angle substantially the same as said first braid angle when in a nominal state, wherein the textile strands along the length of the tubular sleeve are free of bonding to one another at the second intersections, said tubular sleeve being adjustable between the nominal state and a radially-reduced axially-elongated state according to a second relationship of radial reduction versus axial elongation substantially equivalent to said first relationship; and

attaching a selected one of the latticework and sleeve within and in an axial alignment with the other of said latticework and sleeve so that said other surrounds the selected one.

2. The process of claim 1 wherein:

said forming of structural strands includes arranging the structural strands as first and second sets of helices wound in opposite directions about a common longitudinal axis, thereby forming rhombic interstices between adjacent structural strands.

3. The process of claim 2 wherein:

said forming of textile strands includes arranging the textile strands as third and fourth sets of helices wound in opposite directions at the second braid angle when the sleeve is in its nominal state.

4. The process of claim 3 wherein said second braid angle is between 100.91 and 105.45 percent of said first braid angle and the sleeve is attached about and in axial alignment with the latticework.

5. The process of claim 3 wherein said second braid angle is between 97.72 and 102.27 percent of said first braid angle and the sleeve is attached within and in axial alignment with the latticework.

6. The process of claim 2 wherein:

said structural material is thermally formable, and said forming of structural strands further includes winding the structural strands around a selectively sized first mandrel, then heating the strands while so wound to a heat forming temperature sufficient to thermally impart a nominal size and shape for the latticework when in its nominal state; and

wherein said textile strands are thermally formable, and said forming of textile strands further includes winding the textile strands around a selectively sized second mandrel, then heating the textile strands while so wound to a second heat forming temperature sufficient to thermally impart a nominal size and shape to the sleeve when in the nominal state.

7. The process of claim 6 wherein:

said selected one of the latticework and sleeve is the latticework, and said disposing includes positioning the latticework within and surrounded by the sleeve.

8. The process of claim 7 wherein:

said first mandrel has a diameter less than that of said second mandrel.

9. The process of claim 2 wherein:

said forming of structural strands further includes heat setting the structural strands when they are wound about a first mandrel at a first braid angle to determine a nominal latticework size and shape, said forming of textile strands includes thermally setting the textile strands when they are wound about a second mandrel at a second braid angle to determine a nominal sleeve size and shape.

10. The process of claim 9 wherein:

the second mandrel has a diameter greater than that of the first mandrel, and said first and second braid angles are within one degree of one another.

11. The process of claim 9 wherein:

said first and second mandrels have substantially the same diameters, and the first braid angle is larger than the second braid angle.

12. The process of claim 1 further including:

prior to said disposing, applying an adhesive to at least one of the latticework and the sleeve over at least a portion of its axial length, wherein said forming an attachment includes maintaining the latticework and the sleeve in said engagement for a time sufficient for the adhesive to bond the latticework and the sleeve to form the composite stent graft.

13. The process of claim 12 wherein:

said applying includes dissolving the adhesive in a liquid solvent, spraying the combined solvent and adhesive onto the at least one of the latticework and sleeve, and then evaporating the solvent whereby said coating is formed of a residue consisting essentially of the adhesive.

14. The process of claim 13 wherein:

said applying further includes providing the adhesive in the form of a siloxane polymer and dissolving the siloxane polymer in an organic solvent at about 6 percent siloxane polymer by weight.

15. The process of claim 13 wherein:

said adhesive is heat curable, and said forming an attachment includes maintaining the composite stent graft at a temperature of about 125-200 degrees C. for about 20 minutes to one hour.

16. The process of claim 12 wherein:

said adhesive is curable, and applied uncured to said at least one of the latticework and sleeve; and

said forming of the attachment includes curing said adhesive to bond the latticework and sleeve.

17. The process of claim 16 wherein:

said applying includes electrostatically depositing an adhesive onto the at least one of said latticework and sleeve.

18. The process of claim 16 further including:

after said curing, plastically deforming the latticework to reduce the radii of the latticework and the sleeve to their respective states.

19. The process of claim 1 wherein:

said disposing includes adjusting the selected one of the latticework and sleeve to reduce its radius below that in its nominal state, axially aligning the selected one with the other while the other remains in its nominal state, and then radially expanding the selected one toward said engagement with the other.

20. A stent graft formed according to the process of claim 1.

21. The process of claim 1 wherein:

the forming of the compliant textile strands into a tubular sleeve comprises imparting to the sleeve in the nominal state a diameter substantially the same as a corresponding diameter of the tubular open latticework in the nominal state.

22. A process for making a medical device, including:

providing a tubular stent comprised of a plurality of structural strands and adjustable between a nominal state and a radially-reduced axially-elongated state according to a first relationship of radial reduction vs. axial elongation;

winding a plurality of complaint and thermally formable textile strands, to form a tubular sleeve having substantially the same size and shape as the stent in its nominal statem and heating the sleeve to a heat forming temperature sufficient to thermally impart said size and shape to the sleeveas the nominal size and shape of the sleeve when in a nominal state, wherein the sleeve is adjustable between said nominal state and a radially-reduced axially-elongated state according to a second relationship of radial reduction vs. axial elongation substantially equivalent to said first relationship, and provides a graft;

disposing a selected one of the stent and the sleeve within and in an axial alignment with the other of the stent and sleeve, so that said other surrounds the selected one, then bringing the stent and sleeve into an engagement; and

while maintaining the stent and sleeve in said engagement, binding the latticework and the sleeve together.

23. The process of claim 22 further including:

applying an adhesive to at least one of the stent and the sleeve over at least a portion of its axial length; and

wherein said binding includes maintaining the sleeve and the stent in said engagement for a time sufficient for the adhesive to bond the sleeve and the stent.

24. The process of claim 23 wherein:

said adhesive is a curable adhesive, and is applied uncured to the at least one of said stent and sleeve; and

said binding of the stent and sleeve includes curing the adhesive.

25. The process of claim 22 wherein:

said disposing includes adjusting said selected one of the stent and sleeve to reduce its radius below that in its nominal state, axially aligning the selected one while radially reduced with the other of said stent and sleeve while said other remains in its nominal state, then radially expanding said selected one toward said engagement with the other.

26. The process of claim 22 wherein:

said disposing places the stent within and surrounded by the sleeve.

27. The process of claim 22 wherein:

said structural strands are thermally formable, and said providing a tubular stent comprises winding the structural strands around a selectively sized first mandrel, then heating the strands while so wound to a first heat forming temperature sufficient to thermally impart a nominal size and shape for the stent when in its nominal state.

28. The process of claim 27 wherein:

said winding a plurality of textile strands comprises winding the textile strands around a selectively sized second mandrel.

29. The process of claim 22 wherein:

said providing a tubular stent comprises arranging the structural strands as first and second sets of helices wound in opposite directions about a common longitudinal axis, thereby forming rhombic interstices between adjacent structural strands.

30. The process of claim 29 wherein:

said arranging of the structural strands further includes heat setting the structural strands when they are wound about a first mandrel at a first braid angle to determine a nominal stent size and shape.

31. The process of claim 30 wherein:

said winding a plurality of textile strands comprises arranging the textile strands as third and fourth sets of helices wound in opposite directions at a second braid angle when the sleeve is in its nominal state; and

said heating the tubular sleeve includes thermally setting the textile strands when they are wound about a second mandrel at a second braid angle to determine the nominal sleeve size and shape.

32. The process of claim 31 wherein:

the second mandrel has a diameter greater than that of the first mandrel, and the first and second braid angles are within one degree of one another.

33. The process of claim 31 wherein:

said first and second mandrels have substantially the same diameters, and the first braid angle is larger than the second braid angle.

34. A stent graft formed according to the process of claim 22.

35. The process of claim 22 wherein:

said winding a plurality of textile strands further includes winding the textile strands around a selectively sized mandrel.

36. A process for making a medical device, including:

braiding a tubular stent of open construction including a plurality of structural strands forming multiple first intersections and defining a first braid angle with the tubular stent in a nominal state, wherein the structural strands along the length of the tubular stent are free of bonding to one another at the first intersections, the tubular stent being adjustable between the nominal state and a radially-reduced axially-elongated state according to a first relationship of radial reduction versus axial elongation;

braiding a compliant tubular sleeve including a plurality of compliant textile strands forming multiple second intersections and defining a second braid angle substantially the same as said first braid angle with the tubular sleeve in a nominal state, wherein the textile strands along the length of the tubular sleeve are free of bonding to one another at the second intersections, the tubular sleeve being adjustable between said nominal state and a radially-reduced axially elongated state according to a second relationship of radial reduction versus axial elongation substantially equivalent to said first relationship; and

attaching a selected one of the stent and the sleeve within and in an axial alignment with the other of said stent and sleeve so that said other surrounds the selected one.

37. The process of claim 36 further including:

prior to said attaching, applying an adhesive to at least one of the stent and the sleeve over at least a portion of its axial length, wherein said attaching includes maintaining the stent and the sleeve engaged with one another for a time sufficient for the adhesive to bond the stent and the sleeve.

38. The process of claim 36 wherein:

the selected one of the stent and sleeve is the stent, and said attaching includes positioning the stent within and surrounded by the sleeve.

39. The process of claim 36 wherein:

said forming of a tubular stent comprises arranging the structural strands as first and second sets of helices wound in opposite directions to form rhombic interstices between adjacent structural strands; and

said forming the tubular sleeve comprises arranging the textile strands as third and fourth sets of helices wound in opposite directions about a common longitudinal axis.

40. The process of claim 36 wherein:

said forming the stent includes heat setting the structural strands when they are wound about a first mandrel at the first braid angle to determine the nominal stent size and shape, and said forming the tubular sleeve includes thermally setting the textile strands when they are wound about a second mandrel at the second braid angle to determine the nominal sleeve size and shape.

41. The process of claim 36 wherein:

said forming a compliant tubular sleeve comprises imparting to the sleeve in the nominal state a diameter and shape substantially the same as a corresponding diameter and shape of the tubular stent in the nominal state.

42. A process for making a medical device, including:

providing a tubular stent adjustable between a nominal state and a radially-reduced axially-elongated state according to a first relationship of radial reduction versus axial elongation;

forming a compliant tubular sleeve of a thermally formable material having substantially the same shape and diameter as the stent in its nominal state, heating the tubular sleeve while it is maintained in said shape and diameter to a heat forming temperature sufficient to thermally impart said shape and diameter to the sleeve when the sleeve is in a nominal state, wherein the sleeve is adjustable between said nominal state and a radially-reduced axially-elongated state according to a second relationship of radial reduction versus axial elongation substantially equivalent to said first relationship, and provides a graft;

disposing a selected one of the stent and the compliant sleeve within and in an axial alignment with the other of the stent and sleeve, so that said other surrounds the selected one, then bringing the stent and sleeve into an engagement; and

while maintaining the stent and compliant sleeve in said engagement, binding the stent and sleeve together.

43. The process of claim 42 further including:

applying an adhesive to at least one of the stent and the sleeve over at least a portion of its axial length; and

wherein said binding includes maintaining the sleeve and the stent in said engagement for a time sufficient for the adhesive to bond the sleeve and the stent.

44. The process of claim 42 wherein:

said disposing places the stent within and surrounded by the sleeve.

45. The process of claim 42 wherein:

said providing a tubular stent comprises arranging a plurality of structural strands into first and second sets of helices wound in opposite directions about a common longitudinal stent axis, and said forming a tubular sleeve comprises arranging a plurality of textile strands into third and fourth sets of helices wound in opposite directions about a common longitudinal sleeve axis.

46. The process of claim 45 wherein:

said structural strands are thermally formable, and said providing a tubular stent further comprises winding the structural strands around a selectively sized first mandrel, then heating the strands while so wound to a first heat forming temperature sufficient to thermally impart a nominal size and shape for the stent when in its nominal state; and

said forming a compliant tubular sleeve comprises winding the textile strands around a selectively sized second mandrel.