Vascular implant

Abstract

A medical implant (20) includes first and second ring members (22, 24), each including a resilient framework (26) having a generally cylindrical form. A tubular sleeve (28) is fixed to the first and second ring members so as to hold the ring members in mutual longitudinal alignment, thereby defining a lumen (32) passing through the ring members. A constricting element (30) is fit around the sleeve at a location intermediate the first and second ring members so as to reduce a diameter of the lumen at the location.

1 . A medical implant, comprising:
 first and second ring members, each comprising a resilient framework having a generally cylindrical form;   a tubular sleeve, fixed to the first and second ring members so as to hold the ring members in mutual longitudinal alignment, thereby defining a lumen passing through the ring members; and   a constricting element, which is fit around the sleeve at a location intermediate the first and second ring members so as to reduce a diameter of the lumen at the location.   
     
     
         2 . The implant according to  claim 1 , wherein the framework comprises a wire, which is bent in a serpentine form. 
     
     
         3 . The implant according to  claim 1 , wherein the ring members are adapted to be inserted in a radially-compressed form through a body passage to a target position within the passage, and then to expand radially at the target position so as to open the lumen therethrough. 
     
     
         4 . The implant according to  claim 3 , wherein the framework comprises an elastic material, which is compressible to provide the radially-compressed form of the ring members, and which expands radially when released at the target position. 
     
     
         5 . The implant according to  claim 1 , and comprising one or more longitudinal support members, fixed to the framework of the first and second ring members, alongside the sleeve, so as to join the first and second ring members together. 
     
     
         6 . The implant according to  claim 1 , wherein the sleeve comprises a fabric. 
     
     
         7 . The implant according to  claim 6 , wherein the fabric is stitched to the framework of the first and second ring members. 
     
     
         8 . The implant according to  claim 1 , wherein the lumen passing through the first and second ring members has first and second ends, and wherein the framework is configured to provide elongate protrusions at one or more of the ends of the lumen. 
     
     
         9 . The implant according to  claim 8 , wherein the sleeve is cut at one or more of the first and second ends in conformance with the protrusions. 
     
     
         10 . The implant according to  claim 9 , wherein the sleeve is cut at the first end in conformance with the protrusions, while the sleeve at the second end covers both the protrusions and interstices between the protrusions at the second end of the lumen. 
     
     
         11 . The implant according to  claim 1 , wherein the constricting element is adapted to expand under an outward radial force so as to permit the reduced diameter of the lumen to increase. 
     
     
         12 . The implant according to  claim 11 , wherein the constricting element comprises an elastic wire, having bends that are fastened shut so as to provide the reduced diameter, and which are adapted to open under the outward radial force. 
     
     
         13 . A method for restricting flow of a fluid through a body passage, comprising: providing an implant comprising first and second ring members, each comprising a resilient framework having a generally cylindrical form, with a tubular sleeve, fixed to the first and second ring members so as to hold the ring members in mutual longitudinal alignment, thereby defining a lumen passing through the ring members, and a constricting element fit around the sleeve at a location intermediate the first and second ring members so as to reduce a diameter of the lumen at the location; passing the implant, in a radially-compressed form, through the body passage to a target position within the body passage; and causing the implant to expand radially at the target position so as to open the lumen therethrough. 
     
     
         14 . The method according to  claim 13 , wherein the framework comprises an elastic material, which is compressible to provide the radially-compressed form, and which expands radially when released at the target position. 
     
     
         15 . The method according to  claim 13 , wherein the lumen passing through the first and second ring members has first and second ends, and wherein the framework is configured to provide elongate protrusions at one or more of the ends of the lumen, and wherein causing the implant to expand comprises anchoring the implant in the target position using the elongate protrusions. 
     
     
         16 . The method according to  claim 13 , wherein passing the implant comprises enclosing the implant within a catheter, which passes through the body passage, and wherein causing the implant to expand comprises ejecting the implant through an aperture in a distal end of the catheter. 
     
     
         17 . The method according to  claim 16 , wherein:
 the distal end of the catheter has generally conical shape, and wherein ejecting the implant comprises expanding the distal end so as to open the aperture so that the implant may pass therethrough; or   the distal end of the catheter comprises an elastic plug, which closes the aperture while the catheter passes through the body passage, and wherein ejecting the implant comprises radially compressing the plug so as to open the aperture and to allow the lumen of the implant to pass over the plug.   
     
     
         18 . The method according to  claim 13 , and comprising exerting an outward radial pressure from within the implant after the implant has expanded in the target position so as to open the constricting element, thereby permitting the reduced diameter of the lumen to increase. 
     
     
         19 . Apparatus for delivery of an implant to a target position in a body passage, the apparatus comprising: an elongate, tubular sheath, which is adapted to be passed through the body passage while containing the implant in a compressed state inside the sheath, wherein the sheath has a distal end having a generally conical shape with an aperture formed therein; and an ejector, which is adapted to force the implant in a distal direction, thus causing the distal end of the sheath to tear so as to expand the aperture, whereby the implant passes through the aperture. 
     
     
         20 . The apparatus according to  claim 19 , wherein the distal end of the sheath is scored with lines, along which the sheath tears.