Patent ID: 7070594

Claim:
A method for assessing an ice ball formation during the cryoablation of a target tissue in the vasculature of a patient, said method comprising the steps of: providing a cryocatheter having a cryotip wherein said cryotip includes an expansion chamber; contacting said patient with a reference electrode; positioning said cryotip proximate said target tissue; measuring a first impedance between said cryotip and said reference electrode; cooling said cryotip by expanding a refrigerant in said expansion chamber; measuring a second impedance between said cryotip and said reference electrode after said cooling step; determining a ratio of said first impedance to said second impedance to assess the formation of an ice ball and an extent of the cryoablation of target tissue; and expanding said refrigerant in said expansion chamber until a ratio of two measured impedances is substantially zero.