Sintered ring supported vascular graft

• US 20060149361A1
• Filed: 12/31/2004
• Published: 07/06/2006
• Est. Priority Date: 12/31/2004
• Status: Active Grant

• Current Assignee: Lifeshield Sciences LLC (Acacia Research Corporation)
• Original Assignee: Boston Scientific Scimed, Inc. (Boston Scientific Corporation)
• Inventors: Henderson, Jamie, Kujawski, Dennis
• Granted Patent: US 7,806,922 B2
• Time in Patent Office: Days
• US Class Current: 623/1.320
• CPC Class Codes: A61F 2/06 Blood vessels
• CPC Class Codes: A61F 2250/0018 differing in elasticity, stiffness or compressibility
• CPC Class Codes: B29C 35/0266 Local curing for repairing B29C73/34
• CPC Class Codes: B29C 43/006 Pressing and sintering powders, granules or fibres
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29L 2031/7532 Artificial members, protheses
• CPC Class Codes: B29L 2031/7534 Cardiovascular protheses

Abstract

The vascular graft includes a PTFE tube having non-expanded portions formed from sintering a PTFE green tube extrudate. The non-expanded portions are distributed longitudinally along the PTFE tube. The PTFE tube also has expanded portions formed subsequent to the sintering of the PTFE green tube extrudate. The expanded and non-expanded portions are integral with one another, and alternate with one another along the length of the PTFE tube. The expanded and non-expanded portions each have a respective stiffness, where the stiffness of the non-expanded portion is greater than that of the expanded portion.

Claims

1. A vascular graft for implantation within a body, said vascular graft comprising

a PTFE tube having a length and inner and outer wall surfaces,

said tube having a non-expanded portion formed from sintering a PTFE green tube extrudate and an expanded portion formed subsequent to the sintering of the PTFE green tube extrudate,

said expanded and non-expanded portions being of the same extrudate,

said expanded and non-expanded portions each having a respective stiffness, said stiffness of said non-expanded portion being greater than said stiffness of said expanded portion.

2. A vascular graft according to claim 1, wherein said non-expanded and expanded portions have respective crystalline structures, said crystalline structure of said expanded portion having a higher energy relative to said crystalline structure of said non-expanded portion.

3. A vascular graft according to claim 1, wherein said non-expanded portion has an annular cross-section.

4. A vascular graft according to claim 1, and further comprising multiple non-expanded and expanded portions alternating along the length of the graft.

5. A vascular graft according to claim 1, and further comprising a longitudinal guideline printed on an outer surface of said expanded portion.

6. A PTFE tube comprising first and second ends defining a length therebetween and inner and outer wall surfaces defining a lumen between said first and second ends and a plurality of expanded portions and sintered non-expanded portions along said length.

7. A PTFE tube according to claim 6, wherein said expanded and sintered non-expanded portions have respective crystalline structures, said crystalline structures of said sintered non-expanded portions having lower energies relative to said crystalline structures of said expanded portions.

8. A PTFE tube according to claim 6, and further comprising a longitudinal guideline printed on the outer surface of each of said expanded portions, said longitudinal guidelines being collinear relative to one another.

9. A PTFE tube according to claim 6, wherein said expanded portions are sintered.

10. A tubular intermediate which may be manufactured into a vascular graft for implantation within a body, said tubular intermediate comprising

a PTFE green tube extrudate having a pre-sintered portion and an un-sintered portion, said pre-sintered portion having a stiffness which is greater than the stiffness of said un-sintered portion.

11. A tubular intermediate according to claim 10, wherein said pre-sintered and un-sintered portions have respective crystalline structures, said crystalline structure of said pre-sintered portion having a lower energy relative to said crystalline structure of said un-sintered portion.

12. A tubular intermediate according to claim 10, and further comprising a plurality of pre-sintered portions distributed longitudinally between a plurality of un-sintered portions.

13. An apparatus for making a tubular intermediate for a vascular graft, said apparatus comprising:

a support fixture for supporting a PTFE green tube extrudate; and

an energy source for heating a selected portion of the extrudate for sintering thereof.

14. An apparatus according to claim 13, wherein said energy source comprises a plurality of filaments each of which has a longitudinal central axis defining a filament axis, each of said filament axes being circular and contained in a corresponding filament plane,

each said filament encircling a filament center which is contained in said corresponding filament plane,

said apparatus further comprising an elongate fixture on which each said filament is mounted such that said filament planes are parallel to one another and said filament centers coincide with an alignment axis,

each of said circular filaments having an inner diameter which is larger than the outer diameter of a corresponding portion of the extrudate such that the extrudate can be positioned relative to each of said filaments such that each said filament encircles the corresponding portion of the extrudate.

15. An apparatus according to claim 13, wherein said energy source comprises a plurality of filaments each of which has a longitudinal central axis defining a filament axis, each of said filament axes being semi-circular and contained in a corresponding filament plane,

each of said filaments partially encircling a filament center which is contained in said corresponding filament plane,

said apparatus further comprising a pair of corresponding elongate fixtures, each said filament being supported on one of said fixtures such that, in each said fixture, said filament planes are parallel to one another and said filament centers coincide with an alignment axis, said support of said filaments on said fixtures further providing for each said filament to mate with a corresponding filament in said other fixture when said fixtures are closed together, said mating providing for said corresponding pairs of said filaments to be circular,

each said corresponding pairs of filaments having an inner diameter which is larger than the outer diameter of a corresponding portion of the extrudate such that the extrudate can be positioned relative to each of said corresponding pairs of said filaments such that said corresponding pairs of filaments encircle the corresponding portion of the extrudate.

16. An apparatus according to claim 15, wherein corresponding longitudinal side edges of said fixtures are hinged together to provide for said fixtures to pivotally open and close in the manner of a clam shell.

17. An apparatus for making a tubular intermediate for a vascular graft, said apparatus comprising:

a support fixture for supporting a PTFE green tube extrudate; and

a means for applying energy to a selected portion of the extrudate for sintering thereof.

18. A method for making a vascular graft comprising:

providing a PTFE green tube extrudate which is un-sintered; and

pre-sintering a portion of the extrudate to produce a pre-sintered portion having a stiffness which is greater than the stiffness of the un-sintered portion of the extrudate.

19. A method for making a vascular graft according to claim 18, wherein said pre-sintering step comprises:

providing a filament for heating a portion of the extrudate;

positioning the filament in sufficient proximity to the outer surface of the extrudate to transfer heat thereto; and

heating the filament to cause a portion of the extrudate to expand radially outward into engagement with the filament to sinter a portion of the extrudate constituting the pre-sintered portion.

20. A method for making a vascular graft according to claim 19, and further comprising

reducing the temperature of the filament to cause the portion of the extrudate expanded by the heating step to contract radially inward such that the extrudate disengages from the filament resulting in the portion of the extrudate which engaged the filament having an outer diameter which is less than the outer diameter of the adjoining portions of the extrudate.

21. A method for making a vascular graft according to claim 18, wherein said pre-sintering step comprises sintering a plurality of annular portions of the extrudate such that the pre-sintered annular portions are located longitudinally between un-sintered portions of the extrudate, said pre-sintered portions each having an annular cross-section.

22. A method for making a vascular graft according to claim 18, wherein said pre-sintering step comprises heating an elongate portion of the extrudate such that the pre-sintered portion has a longitudinal axis which is parallel to a longitudinal axis of the extrudate.