Refrigeration source for a cryoablation catheter

Abstract

An apparatus and method for automatic operation of a refrigeration system to provide refrigeration power to a catheter for tissue ablation or mapping. The primary refrigeration system can be open loop or closed loop, and a precool loop will typically be closed loop. Equipment and procedures are disclosed for bringing the system to the desired operational state, for controlling the operation by controlling refrigerant flow rate, for performing safety checks, and for achieving safe shutdown. The catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (−40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about −88° C. In operation, the working pressure is computer controlled to obtain an appropriate outflow pressure for the coldest possible temperature in the tip section.

1 . A cryogenic medical system comprising: 
 a medical device;    a refrigeration system for cooling the medical device including 
 a primary cooling loop circulating a coolant through the medical device; and  
 a precooling loop cooling the coolant before the coolant reaches the medical device;  
   wherein the primary cooling loop includes a recovery system which recovers the coolant after it passes through the medical device and wherein the primary cooling loop is substantially an open loop.    
     
     
         2 . The cryogenic medical system of  claim 1  wherein the primary cooling loop includes: 
 a pressure bottle supplying the coolant to the primary cooling loop; and    a compressor interposed between the medical device and a recovery bottle.    
     
     
         3 . The cryogenic medical system of  claim 1   wherein the precooling loop includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling loop; and    wherein the precooling loop is a substantially closed loop further comprising a compressor and an aftercooler.    
     
     
         4 . The cryogenic medical system of  claim 1   wherein the precooling loop includes a heat exchanger having an inlet and an outlet, the heat exchanger defining a coolant flow path and enveloping a portion of the primary cooling loop; and    further comprising a compressor in fluid communication with an aftercooler outputting coolant to the inlet of the heat exchanger and receiving coolant from the outlet of the heat exchanger.    
     
     
         5 . A cryogenic medical system comprising: 
 a medical device;    a console;    a primary cooling system directing a coolant to the medical device; and,    a precooling system cooling the coolant before the coolant reaches the medical device;    wherein the primary cooling system includes a recovery system which recovers the coolant after it passes through the medical device and wherein the primary cooling system is substantially an open loop.    
     
     
         6 . The cryogenic medical system of  claim 5  wherein the primary cooling system includes: 
 a pressure bottle supplying the coolant to the primary cooling system; and    a compressor interposed between the medical device and a recovery bottle.    
     
     
         7 . The cryogenic medical system of  claim 5   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling system; and    wherein the precooling system is a substantially closed loop further comprising a compressor and an aftercooler.    
     
     
         8 . The cryogenic medical system of  claim 5   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger defining a coolant flow path and enveloping a portion of the primary cooling system; and    further comprising a compressor in fluid communication with an aftercooler outputting coolant to the inlet of the heat exchanger and receiving coolant from the outlet of the heat exchanger.    
     
     
         9 . A cryogenic medical system comprising: 
 a medical device having a connection point;    a console;    a primary cooling system directing a coolant to the medical device; and    a precooling system cooling the coolant before the coolant reaches the connection point;    wherein the primary cooling system includes a recovery system which recovers the coolant after it passes through the medical device and wherein the primary cooling system is substantially an open loop.    
     
     
         10 . The cryogenic medical system of  claim 9  wherein the primary cooling system includes: 
 a pressure bottle supplying the coolant to the primary cooling system; and    a compressor interposed between the medical device and a recovery bottle.    
     
     
         11 . The cryogenic medical system of  claim 9   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling system; and    wherein the precooling system is a substantially closed loop further comprising a compressor and an aftercooler.    
     
     
         12 . The cryogenic medical system of  claim 9   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger defining a coolant flow path and enveloping a portion of the primary cooling system; and    further comprising a compressor in fluid communication with an aftercooler outputting coolant to the inlet of the heat exchanger and receiving coolant from the outlet of the heat exchanger.    
     
     
         13 . A cryogenic medical system comprising: 
 a medical device having a connection point;    a console, the console being used to cool the medical device and being connectable to the medical device at the connection point, the console including 
 a primary cooling system directing a coolant to the medical device along a supply conduit; and  
 a precooling system cooling the coolant within the supply conduit before the coolant reaches the connection point;  
   wherein the primary cooling system includes a return conduit leading from the medical device to a recovery system which recovers the coolant after it passes through the medical device and wherein the primary cooling system is substantially an open loop.    
     
     
         14 . The cryogenic medical system of  claim 13  wherein the primary cooling system includes: 
 a pressure bottle in fluid communication with the supply conduit; and    a compressor interposed between the medical device a recovery bottle.    
     
     
         15 . The cryogenic medical system of  claim 13   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the supply conduit; and    wherein the precooling system is a substantially closed loop further comprising a compressor and a condenser.    
     
     
         16 . The cryogenic medical system of  claim 13   wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger defining a coolant flow path and enveloping a portion of the supply conduit; and    further comprising a compressor in fluid communication with an aftercooler outputting coolant to the inlet of the heat exchanger and receiving coolant from the outlet of the heat exchanger.    
     
     
         17 . A cryogenic medical system comprising: 
 a medical device;    a console, the console being connectable to the medical device at a connection point, the console controlling temperature of the medical device, and the console including 
 a first cooling system directing coolant to the medical device at a first temperature along a coolant supply line; and  
 a second cooling system chilling the coolant within the coolant supply line to a temperature below the first temperature before the coolant reaches the connection point;  
   wherein the first cooling system includes a coolant return line leading from the catheter to a coolant scavenging system, and wherein the first cooling system and the catheter comprise a substantially open-loop.    
     
     
         18 . The cryogenic medical system of  claim 17  wherein the first cooling system includes: 
 a coolant reservoir in fluid communication with the fluid supply line; and    a vacuum pump interposed between the catheter and the coolant collection tank.    
     
     
         19 . The cryogenic medical system of  claim 17   wherein the second cooling system includes an enclosure having an inlet and an outlet; the enclosure defining a fluid path from the inlet to the outlet, and the enclosure enveloping a portion of the coolant supply line; and    further comprising a compressor in fluid communication with a condenser outputting coolant to the inlet of the enclosure and receiving coolant from the outlet of the enclosure.    
     
     
         20 . A cryogenic medical system comprising: 
 a medical device, wherein the medical device includes a catheter;    a refrigeration system for cooling the medical device including 
 a primary cooling loop circulating a coolant through the medical device; and  
 a precooling loop cooling the coolant before the coolant reaches the catheter;  
   wherein the primary cooling loop includes a recovery system which recovers the coolant after it passes through the catheter and wherein the primary cooling loop is substantially an open loop; and    wherein the precooling loop includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling loop.    
     
     
         21 . The cryogenic medical system of  claim 20   wherein the coolant is supplied to the primary cooling loop in a substantially gaseous state; and    wherein the precooling loop cools the coolant within the primary cooling loop from a substantially gaseous state to a substantially liquid state.    
     
     
         22 . A cryogenic medical system comprising: 
 a medical device, wherein the medical device includes a catheter;    a console;    a primary cooling system directing a coolant to the catheter;    a precooling system cooling the coolant before the coolant reaches the catheter;    wherein the primary cooling system includes a recovery system which recovers the coolant after it passes through the catheter and wherein the primary cooling system is substantially an open loop; and    wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling system.    
     
     
         23 . The cryogenic medical system of  claim 22   wherein the coolant is supplied to the primary cooling system in a substantially gaseous state; and    wherein the precooling system cools the coolant within the primary cooling system from a substantially gaseous state to a substantially liquid state.    
     
     
         24 . A cryogenic medical system comprising: 
 a medical device having a connection point, wherein the medical device includes a catheter;    a console;    a primary cooling system directing a coolant to the catheter;    a precooling system cooling the coolant before the coolant reaches the connection point;    wherein the primary cooling system includes a recovery system which recovers the coolant after it passes through the catheter and wherein the primary cooling system is substantially an open loop; and    wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the primary cooling system.    
     
     
         25 . The cryogenic medical system of  claim 24   wherein the coolant is supplied to the primary cooling system in a substantially gaseous state; and    wherein the precooling system cools the coolant within the primary cooling system from a substantially gaseous state to a substantially liquid state.    
     
     
         26 . A cryogenic medical system comprising: 
 a medical device having a connection point, wherein the medical device includes a catheter;    a console, the console being used to cool the catheter and being connectable to the medical device at the connection point, the console including 
 a primary cooling system directing a coolant to the catheter along a supply conduit; and  
 a precooling system cooling the coolant within the supply conduit before the coolant reaches the connection point;  
   wherein the primary cooling system includes a return conduit leading from the catheter to a recovery system which recovers the coolant after it passes through the catheter and wherein the primary cooling system is substantially an open loop; and    wherein the precooling system includes a heat exchanger having an inlet and an outlet, the heat exchanger enveloping a portion of the supply conduit.    
     
     
         27 . The cryogenic medical system of  claim 26   wherein the coolant is supplied to the primary cooling system in a substantially gaseous state; and    wherein the precooling system cools the coolant within the primary cooling system from a substantially gaseous state to a substantially liquid state.    
     
     
         28 . A cryogenic medical system comprising: 
 a medical device, wherein the medical device includes a catheter;    a system component, the system component being connectable to the medical device at a connection point, the system component controlling temperature of the medical device, and the system component including 
 a first cooling system directing coolant to the medical device at a first temperature along a coolant supply line; and  
 a second cooling system chilling the coolant within the coolant supply line to a temperature below the first temperature before the coolant reaches the connection point,  
   wherein the first cooling system includes a coolant return line leading from the catheter to a coolant scavenging system, and wherein the first cooling system and the catheter comprise a substantially open-loop, and    wherein the second cooling system includes an enclosure having a fluid inlet and a fluid outlet; the enclosure defining a fluid path from the inlet to the outlet, and the enclosure enveloping a portion of the coolant supply line, and    wherein the inlet is provided inside the enclosure.    
     
     
         29 . The cryogenic medical system of  claim 28   wherein coolant is supplied to the first cooling system in a substantially gaseous state; and,    wherein the second cooling system chills the coolant within the first cooling system and coolant supply line from a substantially gaseous state to a substantially liquid state.    
     
     
         30 . Apparatus for performing cryosurgery, comprising: 
 a refrigerant supply source connectable to a high pressure duct;    a cryosurgery catheter having an inlet connectable to said high pressure duct, said catheter having a tip;    a Joule-Thomson refrigerant expansion element in said catheter;    a temperature sensor on said catheter;    a pressure sensor adapted to sense pressure inside said catheter tip;    a low pressure duct connectable to an outlet of said catheter;    a flow sensor in said low pressure duct downstream of said catheter; and    a control system connected and programmed to maintain a selected catheter temperature, in response to signals from said temperature sensor, said pressure sensor, and said flow sensor.    
     
     
         31 . An apparatus as recited in  claim 30 , further comprising: 
 a precool heat exchanger in said high pressure duct;    a precool compressor for compressing a secondary refrigerant; and    a precool expansion element connected to said precool compressor for expanding said secondary refrigerant to cool said precool heat exchanger.    
     
     
         32 . An apparatus as recited in  claim 31 , further comprising: 
 a bypass valve connected between an outlet of said precool compressor and an inlet of said precool compressor.    
     
     
         33 . An apparatus as recited in  claim 30 , wherein: 
 said refrigerant supply source comprises a pressure bottle; and    a fluid controller in said high pressure duct; and    further comprising a recovery bottle connected to said low pressure duct.    
     
     
         34 . An apparatus as recited in  claim 33 , wherein said fluid controller comprises a pressure controller.  
     
     
         35 . An apparatus as recited in  claim 33 , wherein said fluid controller comprises a flow controller.  
     
     
         36 . An apparatus as recited in  claim 33 , further comprising: 
 a vacuum pump having an inlet connected to said low pressure duct;    a recovery pump having an inlet connected to an outlet of said vacuum pump, said recovery pump having an outlet connected to said recovery bottle;    a bypass valve in a bypass duct connected between said high pressure duct and said low pressure duct; and    a vent valve connected to said bypass duct between said bypass valve and said high pressure duct.    
     
     
         37 . An apparatus as recited in  claim 30 , wherein: 
 said refrigerant supply source comprises a compressor;    said high pressure duct is connected to an outlet of said compressor;    a compressor controller; and    said control system operates said compressor controller to maintain refrigerant pressure above a selected level in said high pressure duct.    
     
     
         38 . An apparatus as recited in  claim 37 , further comprising a second compressor with a second compressor controller; 
 wherein:    said low pressure duct is connected to an inlet of said second compressor;    an outlet of said second compressor is connected to an inlet of said first compressor;    said control system operates said first compressor controller to maintain refrigerant pressure above a selected level in said high pressure duct; and    said control system operates said second compressor controller to maintain refrigerant pressure below a selected level in said low pressure duct.    
     
     
         39 . Apparatus for performing-cryosurgery, comprising: 
 a primary refrigerant pressure bottle connectable to a high pressure duct;    a fluid pressure controller in said high pressure duct;    a precool heat exchanger in said high pressure duct;    a precool compressor for compressing a secondary refrigerant;    a secondary expansion element connected to expand said secondary refrigerant to cool said precool heat exchanger;    a cryosurgery catheter having an inlet connectable to said high pressure duct;    a primary Joule-Thomson expansion element in said catheter connected to expand said primary refrigerant to cool a portion of said catheter;    a temperature sensor on said catheter;    a low pressure duct connectable to an outlet of said catheter;    a pressure sensor in said low pressure duct;    a flow sensor in said low pressure duct;    a vacuum pump having an inlet connected to said low pressure duct;    a recovery pump having an inlet connected to an outlet of said vacuum pump;    a recovery bottle connected to an outlet of said recovery pump;    a bypass valve in a bypass duct connected between said high pressure duct and said low pressure duct; and    a control system connected and programmed to operate said pressure controller to maintain a selected primary refrigerant flow rate, in response to signals from said temperature sensor, said pressure sensor, and said flow sensor.