Patent ID: 7794454

Claim:
A method for ablating a target region of cardiac tissue, comprising the steps of: providing a medical instrument having a flexible body having at least one lumen, proximal and distal end portions, the distal end portion enclosing a thermally transmissive cryochamber in fluid communication with the at least one lumen; a thermally transmissive coil eccentric with respect to the flexible body and in fluid communication with the at least one lumen, positioning the instrument to dispose the cryochamber proximate the target region of cardiac tissue, injecting a cryogenic fluid flow into the at least one lumen in the instrument body, expanding the cryogenic fluid flow inside the cryochamber, controlling the flow of cryogenic fluid remote from the thermally-transmissive cryochamber to vary the temperature and rate of cooling of the cryochamber, wherein the step of positioning the instrument to dispose the cryochamber proximate the target region of cardiac tissue comprises: percutaneously inserting the distal end portion of the instrument through the pericardium for accessing the target region of cardiac tissue, and advancing the instrument through the pericardium to dispose the cryochamber proximate the target region of cardiac tissue; and sensing electrical activity of the cardiac tissue to be treated, wherein sensing electrical activity and ablating the tissue occur substantially simultaneously.