Beating-heart epicardial radiofrequency ablation: optimal temperature setting

Pulmonary vein isolation is a simple procedure, which has recently been reported as an effective treatment for the termination of atrial fibrillation. Although there are several clinical reports of beating-heart epicardial ablation, the optimal temperature has not been experimentally investigated. We evaluated the effective temperature for the placement of circular lesions around the pulmonary vein–left atrial junction. Twelve swine underwent epicardial ablation to create linear conduction block lesions around the pulmonary vein–left atrial junction by a seven-electrode ablation catheter. The ablation was performed at 60°C (group I), 70°C (group II), 80°C (group III), and 90°C (group IV) for 120 seconds. The creation of a firm conduction block across the ablated lesion under pacing was compared. Complete conduction block was observed in all groups except group I. However, heat injury to adjacent structures in group IV and transient discoloration of the tissue surrounding coronary arteries in groups III and IV were observed. The effective temperature for epicardial radiofrequency pulmonary vein isolation was 120 minutes and above 70°C.