Procedures for introducing stents and stent-grafts

Abstract

This invention is a medical device and a method of using it. The device is a foldable stent or stent-graft which may be percutaneously delivered with (or on) a catheter, typically an endovascular catheter, to a body cavity or lumen and then expanded. It may also be delivered or via surgical (or other) techniques. The expandable stent structure utilizes torsional members which distribute bending and folding loads in such a way that the stent is not plastically deformed. The stent's configuration allows it to be folded or otherwise compressed to a very small diameter prior to deployment without changing the length of the stent. The graft component cooperating with the stent is tubular and preferably is blood-compatible material which may, if desired, be reinforced with fibers. The stent is able to provide collapsible support for otherwise frangible graft material. The invention also involves procedures for folding stents and for deploying stents or stent-grafts which have been folded, bound, or otherwise collapsed to significantly smaller diameters for insertion into a human or animal body. When used with super-elastic alloys, the stent may be collapsed at a convenient temperature either above or, preferably, below the transition temperature of the alloy. The deployment procedures may involve the use of an outer sleeve to maintain the stent or stent-graft at a reduced diameter or may involve one or more external or internal “slip-lines” or “tether wires” to hold and then to release the device.

We claim as our invention:  
     
         1 . A method for preparing a self-expanding stent having two ends, a longitudinal axis between those ends, a passageway between those ends, torsion members having a component approximately parallel to said longitudinal axis, said torsion members storing and releasably restoring angular torsion upon flexing of the stent for introduction into a human body comprising: 
 folding said self-expanding stent along the longitudinal axis to form at least one fold line.    
     
     
         2 . The method of  claim 1  further including the step of introducing a removable slip line into the stent to maintain the stent in a folded condition.  
     
     
         3 . The method of  claim 2  in which the self-expanding stent comprises loops along at least one fold line in the stent through which the slip line is introduced.  
     
     
         4 . The method of  claim 2  in which the removable slip line is woven into the stent at a fold line using a sack knot so to allow removal of the slip line by unweaving the sack knot through axial movement of the slip line.  
     
     
         5 . The method of  claim 1  in which the stent is metallic.  
     
     
         6 . The method of  claim 1  in which the stent is a super-elastic alloy.  
     
     
         7 . The method of  claim 1  in which the stent is nitinol.  
     
     
         8 . The method of  claim 1  where the stent comprises at least one helically aligned torsion member having undulating elements defining said passageway.  
     
     
         9 . The method of  claim 8  where the stent additionally comprises at least one flexible link passing through said helically aligned torsion member and maintaining said at least one helically aligned torsion member in alignment.  
     
     
         10 . The method of claim, 8  where the stent additionally comprises at least one flexible link passing through said undulating elements on adjacent helical turns.  
     
     
         11 . The method of  claim 9  where said undulating elements are arranged in an intercooperating phased relationship between adjacent helical turns.  
     
     
         12 . The method of  claim 11  where said flexible link maintains said undulating elements in phased relationship between adjacent helical turns.  
     
     
         13 . The method of  claim 1  where the stent comprises at least one ring assembly extending circumferentially about said passageway, said ring assembly containing at least one torsion member approximately parallel to said axis, said torsion member being situated so that when said ring assembly is distorted, said torsion member is twisted.  
     
     
         14 . The method of  claim 1  further comprising a graft attached to the stent.  
     
     
         15 . The method of  claim 14  in which the graft is a polymeric nonthrombogenic material.  
     
     
         16 . The method of  claim 14  where the graft comprises a material selected from DACRON, TEFLON, KEVLAR, GORETEX, and porous polyurethane.  
     
     
         17 . The method of  claim 14  where the graft comprises a collagen-based material.  
     
     
         18 . The method of  claim 14  where the graft additionally comprises reinforcing fibers within said tubular member.  
     
     
         19 . The method of  claim 14  where the tubular member additionally comprises radiopaque fibers within said tubular member.  
     
     
         20 . A method for the introduction into a human body of a self-expanding stent having two ends, a longitudinal axis between those ends, a passageway between those ends, torsion members having a component approximately parallel to said longitudinal axis, said torsion members storing and releasably restoring angular torsion upon flexing of the stent, which stent has been folded along said longitudinal axis to form one or more fold lines, comprising the steps of: 
 introducing said folded self-expanding stent to a selected site in a human body,    releasing the folded self-expanding stent so to allow the stent-graft to expand at the selected site in the body.    
     
     
         21 . The method of  claim 20  in which the selected site is a vascular site.  
     
     
         22 . The method of  claim 20  wherein the stent is maintained in a folded condition prior to release by a removable slip line.  
     
     
         23 . The method of  claim 20  in which the self-expanding stent comprises loops along at least one fold line in the stent through which the slip line is introduced.  
     
     
         24 . The method of  claim 22  in which the removable slip line is woven into the stent at a fold line using a sack knot so to allow removal of the slip line by unweaving the sack knot through axial movement of the slip line.  
     
     
         25 . The method of  claim 20  in which the stent is metallic.  
     
     
         26 . The method of  claim 20  in which the stent is a super-elastic alloy.  
     
     
         27 . The method of  claim 20  in which the stent is nitinol.  
     
     
         28 . The method of  claim 20  where the stent comprises at least one helically aligned torsion member having undulating elements defining said passageway.  
     
     
         29 . The method of  claim 28  where the stent additionally comprises at least one flexible link passing through said helically aligned torsion member and maintaining said at least one helically aligned torsion member in alignment.  
     
     
         30 . The method of  claim 28  where the stent additionally comprises at least one flexible link passing through said undulating elements on adjacent helical turns.  
     
     
         31 . The method of  claim 28  where said undulating elements are arranged in an intercooperating phased relationship between adjacent helical turns.  
     
     
         32 . The method of  claim 30  where said flexible link maintains said undulating elements in phased relationship between adjacent helical turns.  
     
     
         33 . The method of  claim 20  where the stent comprises at least one ring assembly extending circumferentially about said passageway, said ring assembly containing at least one torsion member approximately parallel to said axis, said torsion member being situated so that when said ring assembly is distorted, said torsion member is twisted.  
     
     
         34 . The method of  claim 20  further comprising a graft attached to the stent.  
     
     
         35 . The method of  claim 34  in which the graft is a polymeric nonthrombogenic material.  
     
     
         36 . The method of  claim 34  where the graft comprises a material selected from DACRON, TEFLON, KEVLAR, GORETEX, and porous polyurethane.  
     
     
         37 . The method of  claim 34  where the graft comprises a collagen-based material.  
     
     
         38 . The method of  claim 34  where the graft additionally comprises reinforcing fibers within said tubular member.  
     
     
         39 . The method of  claim 34  where the tubular member additionally comprises radiopaque fibers within said tubular member.  
     
     
         40 . A prosthetic device for introduction into the human body comprising: 
 a.) a self-expanding stent suitable for introduction into the body, said stent having two ends, a longitudinal axis between those ends, a passageway between those ends, torsion members having a component approximately parallel to said longitudinal axis, said torsion members storing and releasably restoring angular torsion upon flexing of the stent and wherein the stent is folded along the longitudinal axis to form at least one fold line, and    b.) a removable slip line holding said at least one fold line closed.    
     
     
         41 . The device of  claim 40  in which the self-expanding stent comprises loops along at least one fold line in the stent through which the slip line is introduced.  
     
     
         42 . The device of  claim 40  in which the removable slip line is woven into the stent at a fold line using a sack knot so to allow removal of the slip line by unweaving the sack knot through axial movement of the slip line.  
     
     
         43 . The device of  claim 40  in which the stent is metallic.  
     
     
         44 . The device of  claim 40  in which the stent is a super-elastic alloy.  
     
     
         45 . The device of  claim 40  in which the stent is nitinol.  
     
     
         46 . The device of  claim 40  where the stent comprises at least one helically aligned torsion member having undulating elements defining said passageway.  
     
     
         47 . The device of  claim 46  where the stent additionally comprises at least one flexible link passing through said helically aligned torsion member and maintaining said at least one helically aligned torsion member in alignment.  
     
     
         48 . The device of  claim 46  where the stent additionally comprises at least one flexible link passing through said undulating elements on adjacent helical turns.  
     
     
         49 . The device of  claim 46  where said undulating elements are arranged in an intercooperating phased relationship between adjacent helical turns.  
     
     
         50 . The device of  claim 48  where said flexible link maintains said undulating elements in phased relationship between adjacent helical turns.  
     
     
         51 . The device of  claim 40  where the stent comprises at least one ring assembly extending circumferentially about said passageway, said ring assembly containing at least one torsion member approximately parallel to said axis, said torsion member being situated so that when said ring assembly is distorted, said torsion member is twisted.  
     
     
         52 . The device of  claim 40  further comprising a graft attached to the stent.  
     
     
         53 . The device of  claim 52  in which the graft is a polymeric nonthrombogenic material.  
     
     
         54 . The device of  claim 52  where the graft comprises a material selected from DACRON, TEFLON, KEVLAR, GORETEX, and porous polyurethane.  
     
     
         55 . The device of  claim 52  where the graft comprises a collagen-based material.  
     
     
         56 . The device of  claim 52  where the graft additionally comprises reinforcing fibers within said tubular member.  
     
     
         57 . The device of  claim 52  where the graft additionally comprises radiopaque fibers within said tubular member.