(12) United States Patent ao) Patent No.: us 7,004,936 B2
Ryba et al. (45) Date of Patent: Feb. 28,2006
A 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.
17 Claims, 3 Drawing Sheets