Systems and methods for making encapsulated hourglass shaped stents

Abstract

Systems and methods for the manufacture of an hourglass shaped stent-graft assembly comprising an hourglass shaped stent, graft layers, and an assembly mandrel having an hourglass shaped mandrel portion. Hourglass shaped stent may have superelastic and self-expanding properties. Hourglass shaped stent may be encapsulated using hourglass shaped mandrel assembly coupled to a dilatation mandrel used for depositing graft layers upon hourglass shaped mandrel assembly. Hourglass shaped mandrel assembly may have removably coupled conical portions. The stent-graft assembly may be compressed and heated to form a monolithic layer of biocompatible material. Encapsulated hourglass shaped stents may be used to treat subjects suffering from heart failure by implanting the encapsulated stent securely in the atrial septum to allow blood flow from the left atrium to the right atrium when blood pressure in the left atrium exceeds that on the right atrium. The encapsulated stents may also be used to treat pulmonary hypertension.

What is claimed is: 
     
         1 . A method for making an encapsulated stent-graft, the method comprising:
 providing a mandrel comprising a first conical region having a first apex and a second conical region having a second apex, the first conical region and the second conical region aligned so that the first and second apexes contact one another;   placing an expandable stent having an hourglass shape in an expanded form on the mandrel so that a first flared end region of the expandable stent conforms to the first conical region and a second flared end region of the expandable stent conforms to the second conical region;   associating a biocompatible material with the expandable stent to form a stent-graft assembly; and   compressing the stent-graft assembly against the mandrel to form the encapsulated stent-graft.   
     
     
         2 . The method of  claim 1 , wherein the biocompatible material has first and second ends and associating the biocompatible material with the expandable stent comprises placing the biocompatible material within a lumen of the expandable stent. 
     
     
         3 . The method of  claim 1 , wherein the biocompatible material has first and second ends and associating the biocompatible material with the expandable stent comprises placing the biocompatible material over the mandrel and within a lumen of the expandable stent. 
     
     
         4 . The method of  claim 2 , further comprising placing a second biocompatible material over the expandable stent. 
     
     
         5 . The method of  claim 3 , wherein compressing the stent-graft assembly comprises winding a layer of tape over the biocompatible material to compress the stent-graft assembly against the mandrel. 
     
     
         6 . The method of  claim 4 , wherein the expandable stent comprises through-wall openings, the method further comprising heating the stent-graft assembly to cause the biocompatible material and the second biocompatible material to bond to one another through the through-wall openings. 
     
     
         7 . The method of  claim 6 , wherein heating the stent-graft assembly causes the biocompatible material and the second biocompatible material to become sintered together to form a monolithic layer of biocompatible material. 
     
     
         8 . The method of  claim 1 , further comprising applying a layer of Fluorinated Ethylene Propylene (FEP) to biocompatible material or second biocompatible material. 
     
     
         9 . The method of  claim 1 , wherein the biocompatible material is pre-formed. 
     
     
         10 . The method of  claim 1 , further comprising manipulating the encapsulated stent-graft to a compressed shape and loading the encapsulated stent-graft into a delivery sheath. 
     
     
         11 . The method of  claim 1 , wherein a first end diameter of the expandable stent is different in size from a second end diameter. 
     
     
         12 . The method of  claim 1 , wherein the mandrel has a neck region disposed between a first conical region and a second conical region, the mandrel configured to be removably uncoupled at the neck region into a first half comprising at least the first conical region and a second half comprising at least the second conical region. 
     
     
         13 . An hourglass shaped mandrel assembly comprising:
 a first portion comprising at least a first conical region having a flared end with a first diameter and an apex end with a second diameter;   a second portion comprising at least a second conical region having a flared end with third diameter and an apex end with a fourth diameter; and   a tapered region coupled to the flared end of the first portion and extending away from the flared end of the first portion, the tapered region having a flared end with a fifth diameter and a tapered end with a sixth diameter, the fifth diameter being equal to the first diameter and the sixth diameter being smaller than the fifth diameter,   wherein the first conical region of the first portion and the second conical region of the second portion are aligned so that apexes of the first portion and second portion are contacting one another.   
     
     
         14 . The hourglass shaped mandrel assembly of  claim 13 , further comprising a neck region positioned between the apex end of the first portion and the apex end of the second portion, wherein the neck region is affixed to at least the first portion or the second portion. 
     
     
         15 . The hourglass shaped mandrel assembly of  claim 13 , wherein the first portion and the second portion are removably coupled at the apex end of the first portion and the apex end of the second portion. 
     
     
         16 . The hourglass shaped mandrel assembly of  claim 13 , wherein the hourglass shaped mandrel is configured to expand radially. 
     
     
         17 . A method for making an encapsulated stent-graft, comprising:
 providing a mandrel assembly having an asymmetric shape;   providing an expandable stent in an expanded form, the expandable stent configured to conform to the asymmetric shape formed by the mandrel assembly;   coupling a biocompatible material to the expandable stent to form a stent-graft assembly; and   compressing the stent-graft assembly on the mandrel assembly to form the encapsulated stent-graft.   
     
     
         18 . The method of  claim 17 , wherein the expandable stent and the biocompatible material are coupled on the mandrel assembly or before placement on the mandrel assembly. 
     
     
         19 . The method of  claim 17 , further comprising coupling a second biocompatible material to an opposing surface of the expandable stent to form the stent-graft assembly, wherein the second biocompatible material is formed of a same or different material as the biocompatible material. 
     
     
         20 . The method of  claim 19 , wherein the mandrel assembly comprises a first mandrel and a second mandrel, the method further comprising:
 positioning the first mandrel within the first end of the expandable stent such that a portion of the second biocompatible material is positioned between the first mandrel and the expandable stent; and   positioning the second mandrel within the second end of the expandable stent such that a portion of the second biocompatible material is positioned between the second mandrel and the expandable stent.   
     
     
         21 . The method of  claim 17 , wherein the biocompatible material comprises a pre-formed biocompatible graft layer having the expandable stent;
 wherein the pre-formed biocompatible graft layer engages the expandable stent on the mandrel assembly.   
     
     
         22 . A method for making an encapsulated stent-graft, comprising:
 providing an asymmetrical stent;   placing a first biocompatible material over the asymmetrical stent;   providing a second biocompatible material for placement within the asymmetrical stent;   inserting a balloon catheter having an inflatable balloon within the asymmetrical stent in a deflated state such that the second biocompatible material is between the asymmetrical stent and the inflatable balloon; and   inflating the inflatable balloon to an inflated state conforming to the shape of the asymmetrical stent, thereby causing the second biocompatible material to engage with the asymmetrical stent to form the encapsulated stent-graft.   
     
     
         23 . The method of  claim 22 , further comprising controlling the pressure within the balloon to achieve a desired adhesion between the first biocompatible material and the second biocompatible material. 
     
     
         24 . The method of  claim 22 , further comprising controlling the pressure within the balloon to achieve a desired inter-nodal-distance of the graft material. 
     
     
         25 . The method of  claim 22 , wherein the second biocompatible material is placed within the asymmetrical stent prior to inserting the balloon catheter within the asymmetrical stent. 
     
     
         26 . The method of  claim 22 , wherein the second biocompatible material is disposed on the inflatable balloon, and wherein inflating the inflatable balloon causes the second biocompatible material disposed on the inflatable balloon to contact and inner surface of the asymmetrical stent thereby engaging the second biocompatible material with the asymmetrical stent. 
     
     
         27 . A method for making an encapsulated stent-graft, comprising:
 providing a funnel having a large end and a small end;   placing an asymmetric stent with a first end, a second end, an exterior surface and an interior surface within the large end of the funnel;   placing a biocompatible tube over the small end of the funnel, the biocompatible tube having a stent receiving portion and a remaining portion;   advancing the asymmetric stent through the funnel and out the small end of the funnel, thereby depositing the asymmetric stent into the biocompatible tube such that the stent is positioned within the stent receiving portion of the biocompatible tube, thereby engaging an exterior surface of the asymmetric stent with the biocompatible tube;   pulling the remaining portion of the biocompatible tube through the first end of the asymmetric stent and out the second end;   introducing a first mandrel having a shape similar to the first side of the asymmetric stent into the first side of asymmetric stent thereby engaging the interior surface of the first side of the asymmetric stent with a portion of the remaining portion of the biocompatible tube; and   introducing a second mandrel having a shape similar to the second side of the asymmetric stent into the second side of the asymmetric stent thereby engaging the interior surface of the second side of the asymmetric stent with a portion of the remaining portion of the biocompatible tube.