Apparatus and method for cryogenic inhibition of hyperplasia

Abstract

Post-angioplasty hyperplasia in blood vessels is treated using a cryosurgical balloon catheter. The balloon catheter is positioned at a target region within the blood vessel, and the balloon inflated by expanding a cryogenic fluid, such as liquid nitrogen, across an expansion orifice into a balloon. The balloon will be constructed so that cooling is achieved primarily in the central regions of the balloon, with the proximal and distal regions being less cold and acting to insulate adjacent regions of the blood vessel from excessive cooling.

1 . A system for treating a blood vessel having a vessel wall, the system comprising: 
 a flexible catheter body having a proximal end and a distal end with a cooling fluid lumen and an exhaust lumen therebetween;    an intravascular balloon in fluid communication with the cooling fluid lumen and the exhaust lumen near the distal end of the catheter body, the balloon expandable to radially engage a surrounding vessel wall and having an inner surface; and    a cooling fluid source coupleable to the cooling fluid lumen adjacent the proximal end of the catheter body, the source configured so that liquid cooling fluid flows from the source through the cooling fluid lumen into the balloon so as to engage at least a portion of the inner surface of the balloon when the balloon is disposed within the blood vessel, the liquid engaging the inner surface of the balloon vaporizing within the balloon to cool the vessel wall.    
     
     
         2 . The system of  claim 1 , wherein the vaporizing cooling fluid expands from the liquid cooling fluid to a gas cooling fluid within the balloon, and wherein the expansion of the vaporizing cooling fluid effects inflation of the balloon.  
     
     
         3 . The system of  claim 1 , wherein the at least a portion of the inner surface of the balloon wall is coated by the liquid cooling fluid when a cooling fluid path through the cooling fluid lumen and the exhaust lumen is open.  
     
     
         4 . The system of  claim 3 , wherein the liquid coats the at least a portion of the inner surface of the balloon wall so as to enhance even cooling over at least a portion of the vessel wall engaged by the balloon.  
     
     
         5 . The system of  claim 1 , wherein the cooling fluid supply and balloon are configured for treating hyperplasia or neoplasia in a body lumen by cooling an inner surface of the body lumen to a temperature and for a time sufficient to inhibit subsequent cell growth.  
     
     
         6 . The system of  claim 5 , wherein the catheter body and balloon comprise a balloon catheter configured for dilating a stenosed artery subject to hyperplasia.  
     
     
         7 . The system of  claim 5 , wherein the latent heat of vaporization of the cooling fluid is sufficient to cool the vessel wall to from 0° C. to −80° C., and wherein a quantity of the cooling fluid is sufficient for cooling in a range from 1 second to 10 seconds.  
     
     
         8 . The system of  claim 1 , wherein a pressure within the balloon is maintained at from 30 psi to 100 psi during cooling.  
     
     
         9 . The system of  claim 1 , wherein the temperature at each end of the balloon is above 0° C. during cooling.  
     
     
         10 . The system of  claim 9 , wherein a temperature profile over a length of the balloon has a temperature between the ends below 0° C. and temperatures at each end above 0° C. during cooling.  
     
     
         11 . The system of  claim 10 , wherein the balloon has a length of at least 1 cm.  
     
     
         12 . The system of  claim 1 , further comprising a thermocouple mounted outside the balloon for measuring a temperature of the vessel wall.  
     
     
         13 . A system for treating a blood vessel having a vessel wall, the system comprising: 
 a flexible catheter body having a proximal end and a distal end;    an intravascular balloon disposed near the distal end of the catheter body, the balloon expandable to radially engage a surrounding vessel wall, the balloon having an inner surface; and    a cooling liquid coating at least a portion of the inner surface of the balloon, the cooling liquid vaporizing within the balloon to cool the vessel wall.    
     
     
         14 . A cryosurgical catheter for use in a blood vessel having a vessel wall, the cryosurgical catheter comprising: 
 a flexible catheter body having a proximal end, a distal end, and a lumen defining an axis therebetween;    an axially elongate balloon disposed at the distal end of the catheter body in fluid communication with the lumen, the balloon having a balloon wall that can expand radially to engage the surrounding vessel wall;    a diffuser head having at least one port in fluid communication with a cooling fluid supply, the diffuser head movable axially within the balloon between a first position and a second position.