Stent-graft assembly with thin-walled graft component and method of manufacture

Abstract

A stent-graft assembly having a thin-walled membrane and method of preparing the same are disclosed. In a first embodiment, the assembly comprises a stent, a coating and a porous membrane, wherein the membrane is less than 0.040 inch thick or less. Portions of the coating extend into the pores of the thin membrane to sealingly engage the membrane to achieve secure adhesion. In a second embodiment the coating and thin membrane bond to form a homogenous structure. In an alternative embodiment, the assembly comprises an inner and outer thin membrane bound to one another through the interstices of the support member and a coating at the proximal and distal regions. In any of the foregoing embodiments, the proximal and distal regions of the stent-graft assembly may comprise an additional coating, whereby layers of material are sealed, thereby minimizing thrombogenic potential of free ends of the assembly.

We claim:  
     
         1 . A stent-graft assembly comprising: 
 a generally cylindrical stent comprising at least one support member, an exterior and an interior, a medial region, a proximal region and a distal region, said at least one support member defining a passageway through the stent;    at least one membrane, said at least one membrane affixed to at least a portion of at least one of said interior and exterior, wherein the at least one membrane defines at least one of a luminal surface and a vascular surface, said at least one membrane being less than 0.040 inch thick.    
     
     
         2 . The stent-graft assembly according to  claim 1  wherein the membrane is less than 0.0016 inch thick.  
     
     
         3 . The stent-graft assembly according to  claim 1  wherein the at least one membrane is of generally uniform thickness.  
     
     
         4 . The stent-graft assembly according to  claim 1  wherein the stent further comprises: 
 a first polymeric coating substantially encapsulating at least a portion of the at least one support member; and  
 the at least one membrane is affixed to the coating.  
 
     
     
         5 . The stent-graft assembly according to  claim 4  wherein the at least one membrane is porous and the coating extends into the pores of the membrane.  
     
     
         6 . A stent-graft assembly according to  claim 4  wherein the at least one membrane and the coating are homogeneously bound to one another.  
     
     
         7 . The stent-graft assembly according to  claim 1  wherein the stent comprises at least one interstice, and the at least one membrane comprises a first inner membrane defining a luminal surface and a second outer membrane defining a vascular surface, wherein the first and second membranes are bound together through the at least one interstice.  
     
     
         8 . The stent-graft assembly according to  claim 7  wherein the at first one membrane is sintered to the second membrane.  
     
     
         9 . The stent-graft assembly according to  claim 1  wherein the assembly also comprises a coating at the proximal and distal regions of the assembly.  
     
     
         10 . The stent-graft assembly according to  claim 9  wherein the coating substantially encapsulates the exterior and the interior of the at least one membrane at the proximal and distal regions of the assembly.  
     
     
         11 . The stent-graft assembly of  claim 4  wherein the assembly also comprises a second coating at the proximal and distal regions of the assembly.  
     
     
         12 . The stent-graft assembly of  claim 11  wherein the second coating substantially encapsulates the exterior and the interior or the at least one membrane at the proximal and distal regions of the assembly.  
     
     
         13 . The stent-graft assembly of  claim 1  wherein said at least one membrane is a polymer selected from the group consisting of polyurethane, polytetrafluoroethylene, dimethyl terephthalate, polyester, polyethylene terephthalate and silicone.  
     
     
         14 . The stent-graft assembly of  claim 4  wherein the coating is a polymer selected from the group consisting of polyurethane, flourinated ethylene propylene and silicone.  
     
     
         15 . The stent graft assembly of  claim 1  wherein the at least one support member comprises: 
 at least one stent element formed of a plurality of substantially straight segments and configured to provide a plurality of upper and lower peaks; and  
 the at least one stent element being capable of retaining a compressed configuration while mounted onto an outer surface of a catheter for delivery to an affected area of a vessel until application of an outward radial force to form an expanded configuration.  
 
     
     
         16 . The stent-graft assembly of  claim 1  wherein the membrane comprises a primary diameter and wherein the membrane is distensible over a range of between 7 and 100% beyond the primary diameter.  
     
     
         17 . A method of forming a stent-graft assembly, the method comprising the steps of: 
 preparing at least one tube by first providing a polymeric tape of less than 0.010 inch thickness;    winding the polymeric tape helically around at least a portion of the length of the mandrel;    placing the wrapped mandrel in an oven at a sufficient temperature and for a sufficient time to achieve sintering of the tape;    providing a generally cylindrical stent having an interior and an exterior, first and second ends and at least one support member;    coating at least a portion of the at least one support member with a coating to substantially encapsulate at least a portion of the at least one support member;    placing the at least one tube contiguous with at least a portion of the interior or the exterior of the stent to define at least one of a luminal surface or a vascular surface; and    introducing a solvent in order to bond the at least one tube to the coating.    
     
     
         18 . The method of  claim 17  wherein the step of coating the stent comprises: 
 mounting an end of the stent on a rotating mandrel; heating the stent;  
 spraying the rotating stent with polymer in solution; curing the stent;  
 alternating the end of the stent that is mounted on the mandrel;  
 repeating the foregoing steps.  
 
     
     
         19 . The method of  claim 17  wherein the step of coating the stent comprises a vapor deposition process.  
     
     
         20 . The method of  claim 17  wherein the step of coating the stent comprises dipping the stent into a polymeric solution.  
     
     
         21 . The method of  claim 17  wherein the coating is a polymer selected from the group consisting of polyurethane, silicone and flourinated ethylene propylene.  
     
     
         22 . The method of  claim 17  wherein the tape comprises a polymer selected from the group consisting of ePTFE, polyurethane, dimethyl terephthalate, polyester, polyethylene terephthalate and silicone.  
     
     
         23 . The method of  claim 17  wherein the stent-graft assembly also comprises a proximal region and a distal region, with the additional step of coating the proximal and distal regions of the stent-graft assembly.  
     
     
         24 . The method according to  claim 17  wherein the tape comprises a width and a plurality of edges, wherein the tape is wound around the mandrel such that adjacent edges of tape overlap 10-60 per cent of the width of the tape.  
     
     
         25 . The method according to  claim 17  wherein the tape is wound about the mandrel at an angle to the longitudinal axis of the mandrel, wherein the angle is between 30 and 60 degrees.  
     
     
         26 . The method according to  claim 17  wherein the wrapped mandrel is heated in an oven for between 30 and 45 minutes.  
     
     
         27 . The method according to  claim 17  wherein the step of introducing a solvent comprises placing the assembly within a super-saturated atmosphere of solvent.  
     
     
         28 . A method for preparing a stent-graft assembly, the method comprising the steps of: 
 providing a polymeric tape of less than 0.010 inch thickness;    helically winding the tape about a mandrel;    heating the wrapped mandrel at sufficient temperature for sufficient time to achieve sintering of the tape to prepare a first thin-walled polymeric tube;    removing the tube from the mandrel;    repeating the foregoing steps to prepare a second thin-walled polymeric tube;    providing a generally cylindrical stent having an interior and an exterior, a proximal region and a distal region, at least one interstice and at least one support member;    lining at least a portion of the interior of the stent with the first tube to define a luminal surface;    placing the second tube over at least a portion of the exterior of the stent to define a vascular surface; and    bonding the first and second tubes to one another through the at least one interstice of the stent.    
     
     
         29 . The method according to  claim 28  with the added step of dipping the proximal and distal regions of the assembly into a polymeric solution.  
     
     
         30 . The method according to  claim 28  wherein the step of bonding the first tube to the second tube comprises heating the assembly for sufficient time at sufficient temperature to achieve sintering of the tubes to one another through the at least one interstice.  
     
     
         31 . A method for preparing a thin-walled graft tube, the method comprising the steps of: 
 providing a polymeric tape of less than 0.010 inch thickness;    helically winding the tape about a mandrel;    applying pressure to the wrapped mandrel; and    heating the wrapped mandrel under pressure at a sufficient temperature for a sufficient time to achieve sintering of the tape.