Catheter with tapered compliant balloon and tapered stent

Abstract

A balloon comprising: a center portion having a proximal end, a distal end opposite the proximal end, and a length between the proximal end and the distal end. The center portion comprises: a first nominal diameter and a first radial modulus at the proximal end; a second nominal diameter and a second radial modulus at the distal end; further wherein, the first nominal diameter is equal to the second nominal diameter, such that, when the balloon is inflated to a nominal pressure, the center portion has a constant diameter over the length; and further wherein, the first radial modulus is smaller than the second radial modulus, such that, when the balloon is inflated above a nominal pressure, the center portion adopts a tapered shape in which the proximal end has a first stretched diameter and the distal end has a second stretched diameter, the first stretched diameter being larger than the second stretched diameter.

We claim: 
     
         1 . A balloon for attachment to a distal portion of a medical catheter, the balloon comprising:
 a center portion having a proximal end, a distal end opposite the proximal end, and a length between the proximal end and the distal end,   wherein the center portion further comprises:
 a first nominal diameter and a first radial modulus at the proximal end; 
 a second nominal diameter and a second radial modulus at the distal end; 
 wherein, the first nominal diameter is equal to the second nominal diameter, such that, when the balloon is inflated to a nominal pressure, the center portion has a constant diameter over the length; and further 
 wherein, the first radial modulus is smaller than the second radial modulus, such that, when the balloon is inflated above a nominal pressure, the center portion adopts a tapered shape in which the proximal end has a first stretched diameter and the distal end has a second stretched diameter, the first stretched diameter being larger than the second stretched diameter. 
   
     
     
         2 . The balloon of  claim 1 , wherein the center portion comprises a compliant polymer membrane which has a first thickness at the proximal end and a second thickness at the distal end, wherein the first thickness is less than the second thickness. 
     
     
         3 . The balloon of  claim 1 , wherein the center portion comprises a compliant polymer membrane and wherein
 a plurality of successive threads are wrapped circumferentially around the center portion to reinforce the center portion, the threads being spaced along the center portion at a constant pitch and being adhesively attached to the center portion;   further wherein   an initial successive thread is located at the proximal end and has a first cross sectional area,   a final successive thread is located at the distal end and has a second cross sectional area, and   a medial successive thread is located between the initial successive thread wherein the final successive thread has a third cross sectional area, and   further wherein the first cross sectional area is smaller than the second cross sectional area and the third cross sectional area is larger than the first cross sectional area but smaller than the second cross sectional area.   
     
     
         4 . The balloon of  claim 1 , wherein the center portion comprises a compliant polymer membrane and wherein
 an initial two consecutive threads are located at the proximal end and have a first pitch between them,   a final two consecutive threads are located at the distal end and have a second pitch between them, and   a medial consecutive two threads are located between the initial two consecutive threads and the final two consecutive threads and have a third pitch between them,   wherein the first pitch is larger than the second pitch and the third pitch is smaller than the first pitch but smaller than the third pitch.   
     
     
         5 . The balloon of  claim 1 , wherein the center portion comprises a compliant polymer membrane and wherein a first thread is wound in a helix along the center portion and
 a first two successive windings are located at the proximal end and have a first pitch,   a final two successive windings are located at the distal end and have a second pitch, and a   medial two successive windings are located between the first two successive windings and the final two successive windings and have a third pitch,   wherein the first pitch is larger than the second pitch and the third pitch is smaller than the first pitch but larger than the third pitch.   
     
     
         6 . The balloon of  claim 1 , wherein the center portion comprises a compliant polymer membrane and wherein
 an initial successive thread is located at the proximal end and is formed from a material having a first elastic modulus,   a final successive thread is located at the distal end and is formed from a material having a second elastic modulus, and   a medial successive thread is located between the initial successive thread and final successive thread, and is formed from a material having a third elastic modulus;   wherein the first elastic modulus is smaller than the second elastic modulus and the third elastic modulus is larger than the first elastic modulus but smaller than the second elastic modulus.   
     
     
         7 . A stent for insertion into a vessel of a patient comprising:
 a plurality of rings that are successively connected to each other by a plurality of links, the plurality of rings extending in an axial direction from a first ring at a proximal end followed by a plurality of succeeding rings to a final ring at a distal end, wherein,
 each succeeding ring is preceded by a preceding ring; 
 each of the plurality of rings includes a plurality of adjacent peaks and valleys, wherein each valley is connected to an adjacent peak by a strut to provide an undulating pattern within each ring; and 
 each of the plurality of rings has a compressed condition for delivery into the patient and an expanded condition after deployment in the patient, wherein, in the compressed condition each preceding ring has a preceding ring length measured in the axial direction and each succeeding ring has a succeeding ring length measured in the axial direction, wherein a ratio of each succeeding ring length divided by each preceding ring length is a constant number that is smaller than unity. 
   
     
     
         8 . The stent of  claim 7 , wherein the first ring has a first ring length and is connected to a second ring by a first link having a first link length, the first link length being equal to the first ring length. 
     
     
         9 . The stent of  claim 7 , wherein the ratio is in a range of 0.90 to 0.95. 
     
     
         10 . A method of expanding a stent within a vasculature of a patient comprising:
 disposing a stent upon a balloon that is deflated, the balloon comprising a center portion having a proximal end, a distal end opposite the proximal end, and a length between the proximal end and the distal end;   inserting the balloon inside the vasculature of the patient;   inflating the balloon to a nominal pressure and, simultaneously, imparting a cylindrical shape to the center portion of the balloon; and   further inflating the balloon to a pressure beyond nominal pressure and, simultaneously, imparting a tapered shape to the center portion of the balloon.   
     
     
         11 . The method of  claim 10 , wherein imparting a cylindrical shape to the center portion of the balloon includes imparting a cylindrical shape to the stent. 
     
     
         12 . The method of  claim 10 , wherein imparting a tapered shape to the center portion of the balloon includes imparting a tapered shape to the stent.