Expandable stent-graft covered with expanded polytetrafluoroethylene

Abstract

The expandable stent-graft generally defines a cylindrical lumen made from a stent having a discontinuous wall that is at least substantially covered with an expended polytetrafluoroethylene material. The expanded polytetrafluoroethylene covering may be a biaxially oriented, expanded polytetrafluoroethylene material having nodules and longitudinal and circumferential fibrils or a uniaxially oriented, expanded polytetrafluoroethylene material. The expandable stent-graft expands and compresses in association with the stent structure as it is contracted and expanded.

1. An expandable stent-graft comprising:
 (a) a braided self-expanding stent characterized by a longitudinal shortening upon radial expansion from a first longitudinal stent length to a second longitudinal stent length; and  
 (b) a least one tubular layer of biaxially oriented expanded polytetrafluoroethylene comprising nodules and fibrils affixed to the stent characterized by a shortening of average longitudinal inter-nodule distance upon radial expansion from a first average longitudinal inter-nodule distance to a second average longitudinal inter-nodule distance and having (i) a first average longitudinal inter-nodule distance of between about 50 and about 150 microns, and (ii) a second average longitudinal inter-nodule distance of between about 0 and about 50 microns; 
 wherein the ratio of first longitudinal stent length to second longitudinal stent length is within about 25 percent of the ratio of first average longitudinal inter-nodule distance to a second average inter-nodule distance.  
 
 
     
     
       2. The expandable stent-graft according to  claim 1  wherein the tubular layer of expanded polytetrafluoroethylene has a second average longitudinal inter-nodule distance of between about 5 and about 45 microns. 
     
     
       3. The expandable stent-graft according to  claim 2  wherein the tubular layer of expanded polytetrafluoroethylene has a second average longitudinal inter-nodule distance of between about 20 and about 30 microns. 
     
     
       4. The expandable stent-graft according to  claim 1  wherein the tubular layer of expanded polytetrafluoroethylene has a first average longitudinal inter-nodule distance of between about 60 and about 140 microns. 
     
     
       5. The expandable stent-graft according to  claim 4  herein the tubular layer of expanded polytetrafluoroethylene has a first average longitudinal inter-nodule distance of between about 80 and about 120 microns. 
     
     
       6. An expandable stent- graft comprising:    ( a )  a braided self - expanding stent having a first longitudinal stent length in an expanded position and a second longitudinal stent length in a contracted position; and      ( b )  at least one tubular layer of expanded polytetrafluoroethylene comprising nodules and fibrils affixed to the stent,        wherein the expanded polytetrafluoroethylene layer has an average longitudinal inter - nodule distance of between about  50  and about  150  microns when the stent is in an expanded position and an average longitudinal inter - nodule distance of between about  0  and about  50  microns when the stent is in a longitudinally contracted position, and wherein the average longitudinal inter - nodule distance shortens from a first average longitudinal inter - nodule distance to a second average longitudinal inter - nodule distance upon radial expansion.     
     
     
       7. The stent- graft of    claim 6   , wherein the ratio of first longitudinal stent length to second longitudinal stent length is within about  25  percent of the ratio of a first average longitudinal inter - nodule distance to a second average inter - nodule distance.   
     
     
       8. The stent- graft of    claim 6   , wherein the fibrils are substantially folded when the stent is in a contracted position and substantially extended when the stent is in an expanded position.   
     
     
       9. The stent- graft of    claim 6   , wherein the expanded polytetrafluoroethylene is biaxially oriented.   
     
     
       10. The stent- graft of    claim 6   , wherein the expanded polytetrafluoroethylene has an average longitudinal inter - nodal distance of between about  5  and about  45  microns.   
     
     
       11. The stent- graft of    claim 6   , wherein the expanded polytetrafluoroethylene has an average longitudinal inter - nodal distance of between about  20  and about  30  microns.   
     
     
       12. The stent- graft of    claim 6   , wherein the expanded polytetrafluoroethylene has an average longitudinal inter - nodal distance of between about  60  and about  140  microns.   
     
     
       13. The stent- graft of    claim 6   , wherein the expanded polytetrafluoroethylene has an average longitudinal inter - nodal distance of between about  80  and about  120  microns.   
     
     
       14. An expandable prosthesis comprising:
 ( a )  a discontinuous wall having a first longitudinal wall length in an expanded position and a second longitudinal wall length in a contracted position; and      ( b )  at least one tubular layer of expanded polytetrafluoroethylene comprising nodules and fibrils,        wherein the expanded polytetrafluoroethylene layer has an average longitudinal inter - nodule distance of between about  50  and about  150  microns when the discontinuous wall is in a longitudinally expanded position and an average longitudinal inter - nodule distance of between about  0  and about  50  microns when the discontinuous wall is in a longitudinally contracted position, wherein the average longitudinal inter - nodule distance shortens from a first average inter - nodule distance to a second average longitudinal distance upon radial expansion; and wherein the ratio of first longitudinal wall length to second longitudinal wall length is within about  25  percent of the ratio of a first average longitudinal inter - nodule distance to a second average inter - nodule distance.     
     
     
       15. An expandable stent- graft comprising:    ( a )  a braided self - expanding stent having a first longitudinal stent length in an expanded position and a second longitudinal stent length in a contracted position; and      ( b )  at least one tubular layer of expanded polytetrafluoroethylene comprising nodules and fibrils affixed to the stent,        wherein the expanded polytetrafluoroethylene layer has an average first inter - nodule distance of between about  50  and about  150  microns when the stent is in an expanded position and an average longitudinal inter - nodule distance of between about  0  and about  50  microns when the stent is in a longitudinally contracted position, and wherein the ratio of the first longitudinal stent length to the second longitudinal stent length is within about  25  percent of the ratio of a first average longitudinal inter - nodule distance to a second average inter - nodule distance.     
     
     
       16. An expandable prosthesis comprising:
 ( a )  a discontinuous wall having a first longitudinal wall length in an expanded position and a second longitudinal wall length in a contracted position; and      ( b )  at least one tubular layer of expanded polytetrafluoroethylene comprising nodules and fibrils affixed to the wall;        wherein the expanded polytetrafluoroethylene layer has an average inter - nodule distance of between about  50  and about  150  microns when the wall is in an expanded position and an average longitudinal inter - nodule distance of between about  0  and about  50  microns when the wall is in a longitudinally contracted position, and wherein the ratio of the first longitudinal wall length to the second longitudinal wall length is within about  25  percent of the ratio of a first average inter - nodule distance to a second average inter - nodule distance.     
     
     
       17. An expandable stent- graft comprising:    ( a )  a braided self - expanding stent that is capable of longitudinal shortening upon radial expansion from a first longitudinal stent length to a second longitudinal stent length; and      ( b )  at least one layer of expanded polytetrafluoroethylene defining spaced - apart nodes interconnected by longitudinally directed fibrils, said nodes having a first average longitudinal inter - nodule distance in a free state, the layer of polytetrafluoroethylene affixed to the stent such that it has a second average longitudinal inter - nodule distance when the stent is in a longitudinally contracted state, the second average longitudinal inter - nodule distance being less than the first average longitudinal inter - nodule distance, said longitudinally directed fibrils being extended in said free state and being folded in said longitudinally contracted state.     
     
     
       18. An expandable stent- graft comprising:    ( a )  a braided self - expanding stent that is capable of longitudinal shortening upon radial expansion;      ( b )  at least one layer of expanded polytetrafluoroethylene comprising spaced apart nodes interconnected by fibrils,        wherein the fibrils are extended when the layer is in a free state and folded in a contracted state, said fibrils defining openings of between about  50  to about  150  microns when the layer is in the free state and openings of about  0  to about  50  microns when the layer is in the contracted state.     
     
     
       19. An expandable prosthesis comprising:
 ( a )  a discontinuous wall defining a lumen adapted to assume a longitudinally contracted position and a longitudinally expanded position; and      ( b )  at least one layer of expanded polytetrafluoroethylene comprising spaced apart nodes interconnected by fibrils,        wherein the fibrils are extended when the discontinuous wall is in an expanded position and folded when the discontinuous wall is in a contracted position, said fibrils defining openings of between about  50  to about  150  microns when the wall is in a longitudinally expanded position and openings of between about  0  to about  50  microns when the wall is in a longitudinally contracted position.