Epicardial cryoablation of myocardial tissue using endocardial thermal isolation.

Surgical cure of right atrial arrhythmias may be accomplished by excision, exclusion, or cryoablation of the arrhythmogenic focus. Cryoablation may be performed epicardially without cardiopulmonary bypass but carries an operative recurrence rate of 57%. Successful cryoablation of a right atrial arrhythmia requires the reliable creation of transmural tissue necrosis. Heat transferred to the endocardium from normothermic circulating blood in the atrium or within the atrial wall may prevent full-thickness, lethal freezes. This study demonstrates that compression of myocardial tissue between an external cryoprobe and an endocardial template produces endocardial thermal isolation of the target area by displacing warm solutions from the endocardium. This is essential to achieve consistently lethal transmural freezes of -60 degrees C. Use of this technique may reduce the high operative recurrence rate of right atrial tachycardias treated with conventional cryoablation techniques.