Expandable introducer sheath

Abstract

A system for delivering medical implants has an expandable introducer sheath which can locally expand and lengthen to accommodate passage of a delivery catheter and implant, such as a prosthetic heart valve secured to a balloon catheter. The expandable sheath may be configured so that the local expansion is proportional to the local surface lengthening.

1 . A delivery sheath, comprising:
 an insertion body, the insertion body comprising an outer elastic layer, an inner elastic layer, a stent-like frame between the inner elastic layer and outer elastic layer, and an adhesive between the inner elastic layer and the stent-like frame, wherein the stent-like frame is configured to locally radially expand in a section thereof proportional to local surface lengthening of the section thereof, wherein the stent-like frame comprises a plurality of circumferential links, a plurality of nodes, and a plurality of longitudinal links, wherein the stent-like frame comprises a plurality of ring-like elements, with each ring-like element extending about a circumference of the stent-like frame, each ring-like element comprising circumferential links alternating with nodes and extending circumferentially about the ring-like element, and wherein adjacent ring-like elements are secured to each other via longitudinal links extending longitudinally between and connecting the nodes of the adjacent ring-like elements, wherein in an unexpanded configuration of a portion of the stent-like frame the longitudinal links and circumferential links in that portion of the stent-like frame have more-curved shapes, and in an expanded configuration of a portion of the stent-like frame the longitudinal links and circumferential links in that portion of the stent-like frame have less-curved shapes; and   a hub.   
     
     
         2 . The delivery sheath of  claim 1 , wherein the stent-like frame is configured to maintain a constant overall linear length during local surface lengthening or local expansion of the stent-like frame. 
     
     
         3 . The delivery sheath of  claim 1 , wherein the stent-like frame is configured to locally radially expand responsive to local surface lengthening of the stent-like frame. 
     
     
         4 . The delivery sheath of  claim 1 , wherein the stent-like frame is configured to locally lengthen responsive to local radially expansion of the stent-like frame. 
     
     
         5 . (canceled) 
     
     
         6 . The delivery sheath of  claim 1 , wherein expansion of the stent-like frame causes one or more of the circumferential links to at least partially straighten, which causes one or more of the nodes to at least partially rotate, which causes one or more of the longitudinal links to at least partially straighten. 
     
     
         7 . The delivery sheath of  claim 1 , wherein lengthening of the stent-like frame causes one or more of the longitudinal links to at least partially straighten, which causes one or more of the nodes to at least partially rotate, which causes one or more of the circumferential links to at least partially straighten. 
     
     
         8 . The delivery sheath of  claim 1 , wherein the stent-like frame comprises a memory material, and wherein the stent-like frame is adapted to locally radially expand responsive to outward pressure, and is further adapted to return to an unexpanded state responsive to removal of the outward pressure. 
     
     
         9 . A delivery sheath, comprising:
 an insertion body, the insertion body comprising an outer elastic layer, an inner lining layer, and a stent-like frame between the outer elastic layer and the inner lining layer, wherein the stent-like frame comprises a plurality of ring-like elements and a plurality of longitudinally-extending links, each of the plurality of longitudinally-extending links comprising a thinner center portion and a plurality of wider end portions, each ring-like element comprising a plurality of circumferentially-extending links alternating with a plurality of nodes, a longitudinally-extending link of the plurality of longitudinally-extending links extending between two nodes of two adjacent ring-like elements, and a node of a portion of the stent-like frame in an expanded state being rotated relative to the node of the portion in an unexpanded state to locally radially expand the stent-like frame responsive to local surface lengthening of the stent-like frame; and   a hub.   
     
     
         10 . The delivery sheath of  claim 9 , wherein each of the plurality of circumferentially-extending links comprises a thinner center portion and wider end portions. 
     
     
         11 . The delivery sheath of  claim 9 , wherein expansion of the stent-like frame causes one or more of the circumferential links to at least partially straighten, which causes one or more of the nodes to at least partially rotate, which causes one or more of the longitudinal links to at least partially straighten. 
     
     
         12 . The delivery sheath of  claim 9 , wherein the node is rotated between 30 degrees to 90 degrees while the portion of the stent-like frame is in the expanded state relative to a position of the node while the portion of the stent-like frame is in the unexpanded state. 
     
     
         13 . The delivery sheath of  claim 9 , wherein each of the plurality of nodes comprises a circular shape having a circular internal cutout. 
     
     
         14 . The delivery sheath of  claim 9 , wherein the stent-like frame is adapted to locally radially expand responsive to outward pressure, and is further adapted to return to the unexpanded state responsive to removal of the outward pressure. 
     
     
         15 . The delivery sheath of  claim 14 , wherein the stent-like frame comprises a memory material. 
     
     
         16 . A delivery sheath, comprising:
 an insertion body, the insertion body comprising an outer elastic layer, an inner lining layer, and a stent-like frame between the outer elastic layer and the inner lining layer, wherein the stent-like frame comprises a plurality of ring-like elements and a plurality of longitudinally-extending links, each ring-like element comprising a plurality of circumferentially-extending links alternating with a plurality of nodes, each of the plurality of circumferentially-extending links comprising a thinner center portion and a plurality of wider end portions, a longitudinally-extending link of the plurality of longitudinally-extending links extending between two nodes of two adjacent ring-like elements, and a node of a portion of the stent-like frame in an expanded state being rotated relative to the node of the portion in an unexpanded state to locally radially expand the stent-like frame responsive to local surface lengthening of the stent-like frame; and   a hub.   
     
     
         17 . The delivery sheath of  claim 16 , wherein expansion of the stent-like frame causes one or more of the circumferential links to at least partially straighten, which causes one or more of the nodes to at least partially rotate, which causes one or more of the longitudinal links to at least partially straighten. 
     
     
         18 . The delivery sheath of  claim 16 , wherein the node is rotated between 30 degrees to 90 degrees while the portion of the stent-like frame is in the expanded state relative to position of the node while the portion of the stent-like frame is in the unexpanded state. 
     
     
         19 . The delivery sheath of  claim 16 , wherein each of the plurality of nodes comprises a circular internal cutout. 
     
     
         20 . The delivery sheath of  claim 16 , wherein the stent-like frame is adapted to locally radially expand responsive to outward pressure, and is further adapted to return to the unexpanded state responsive to removal of the outward pressure. 
     
     
         21 . The delivery sheath of  claim 20 , wherein the stent-like frame comprises a memory material.