Methods of making an expandable sheath

Abstract

Disclosed herein are expandable introducer sheaths and methods of making and using the same. The sheaths minimize trauma to a patient's vasculature by allowing for temporary expansion of a portion of the sheath to accommodate passage of a delivery system for a cardiovascular device, then return to a non-expanded state after the passage of the device. The sheath includes an elongated annular member through which the cardiovascular device and its delivery system pass. In an embodiment, the annular inner member can be formed by coextruding a first and second material. The first material includes a fold, and the second material radially spaces the different parts of the fold from each other during fabrication and provides support for maintaining the tubular structure. The second material is removed once the coextrusion process is complete.

1 . A method of making an expandable sheath comprising:
 coextruding a first material and a second material; and   removing the second coextruded material from the first coextruded material;   wherein the first coextruded material defines an annular member; and   wherein the second coextruded material defines a first and a second set of longitudinally extending ribbons.   
     
     
         2 . The method of  claim 1 , wherein the second coextruded material does not adhere to the first coextruded material. 
     
     
         3 . The method of  claim 1 , wherein the second coextruded material comprises nylon, polyethylene terephthalate, polybutylene terephthalate, or a combination thereof. 
     
     
         4 . The method of  claim 1 , wherein the first and second set of longitudinally extending ribbons form inward and outward extending channels of the annular member, wherein the first set of ribbons extends inwardly from an outer surface toward an inner surface of the annular member forming inward extending channels in the annular member, wherein the second set of ribbons extends outwardly from an inner surface toward an outer surface of the annular member forming outward extending channels in the annular member. 
     
     
         5 . The method of  claim 4 , wherein each ribbon of a selected set is positioned circumferentially between two ribbons of the other set. 
     
     
         6 . The method of  claim 1 , wherein the second coextruded material is removed from the first coextruded material by at least one of applying a thermal treatment to at least one of the first and the second coextruded materials, or applying a chemical treatment to at least one of the first and the second coextruded materials. 
     
     
         7 . The method of  claim 1 , further comprising coextruding the first and second material with a third material, wherein the third material is in contact with a portion of the first coextruded material and a portion of the second coextruded material, where the third coextruded material adheres to both the first and the second coextruded materials and wherein the second coextruded material does not adhere to the first coextruded material. 
     
     
         8 . The method of  claim 1 , further comprising adding a taper tube, at least a portion of the taper tube having a diameter greater than a diameter of the annular member, where the taper tube is added without using a thermal bonding process. 
     
     
         9 . The method of  claim 1 , further comprising adding a taper tube, at least a portion of the taper tube having a diameter greater than a diameter of the annular member, where the taper tube is added without using a bonding process. 
     
     
         10 . The method of  claim 1 , further comprising adding a taper tube, at least a portion of the taper tube having a diameter greater than a diameter of the annular member, where the taper tube is added as part of the coextrusion process. 
     
     
         11 . The method of  claim 1 , further comprising covering the annular member with an outer layer comprising a material having a lower elastic modulus than the annular member, where the annular member and the outer layer expand in a radial direction between an unexpanded state and an expanded state. 
     
     
         12 . The method of  claim 1 , wherein the annular member comprises a plurality of base members arranged around a circumference of the annular member, where the plurality of base members abut a plurality of bridge members extending between opposing pairs of base members,
 wherein the plurality of base members and the plurality of bridge members have rotational degrees of freedom around a longitudinal axis of the annular member,   wherein each of the plurality of bridge members has a first end coupled to a radially inward end of a corresponding one of the plurality of base members, and a second end coupled to a radially outward end of the corresponding one of the plurality of base members.   
     
     
         13 . An expandable sheath comprising:
 an annular member including:
 inward extending channels extending channel extending from an outer surface of the annular member toward an inner surface of the annular member, and 
 outward extending channels extending outwardly from the inner surface toward the outer surface of the annular member, 
   wherein the annular member configured to locally expand from an unexpanded state in which the annular member has a first diameter to an expanded state in which the annular member has a second, larger, diameter,   wherein upon expansion of the annular member, a width of each of the inward extending channels and outward extending channels increases.   
     
     
         14 . The expandable sheath of  claim 13 , wherein the annular member comprises a first material,
 wherein the expandable sheath further comprises a second material that is coextruded with the annular member, the second material defining a first and a second set of longitudinally extending ribbons that occupy the inward and outward extending channels of the annular member.   
     
     
         15 . The expandable sheath of  claim 14 , wherein each ribbon of a selected set is positioned circumferentially between two ribbons of the other set. 
     
     
         16 . The expandable sheath of  claim 14 , wherein the second material does not adhere to the first material. 
     
     
         17 . The expandable sheath of  claim 14 , wherein the second coextruded material is removable from the first coextruded material by applying at least one of a thermal treatment to at least one of the first and the second coextruded materials, or by applying a chemical treatment to at least one of the first and the second coextruded materials. 
     
     
         18 . The expandable sheath of  claim 14 , further comprising a third material coextruded with the first and second material, wherein the third material is in contact with a portion of the first coextruded material and a portion of the second coextruded material, where the third coextruded material adheres to both the first and the second coextruded materials and wherein the second coextruded material does not adhere to the first coextruded material. 
     
     
         19 . The expandable sheath of  claim 14 , further comprising:
 an outer layer covering the annular member configured to locally expanded between the unexpanded state and the expanded state, the outer layer comprising a material having a lower elastic modulus than the annular member.   
     
     
         20 . The expandable sheath of  claim 14 , wherein the annular member comprises a plurality of base members arranged around a circumference of the annular member, wherein the plurality of base members abut a plurality of bridge members extending between opposing pairs of base members,
 wherein the plurality of base members and the plurality of bridge members have rotational degrees of freedom around a longitudinal axis of the annular member,   wherein each of the plurality of bridge members has a first end coupled to a radially inward end of a corresponding one of the plurality of base members, and a second end coupled to a radially outward end of the corresponding one of the plurality of base members.