Epicardial ablation on the beating heart: progress towards an off-pump maze procedure.

BACKGROUND: The treatment of atrial fibrillation with unipolar radiofrequency (RF) catheter ablation techniques has been fraught with difficulty. This study was designed to evaluate the potential advantages of bipolar RF energy and its ability to create transmural linear lesions on the beating heart. METHODS: A right thoracotomy was performed on eight adult sheep. A bipolar RF device was inserted and targeted tissue was clamped between the instrument arms. Ablation was performed on the beating heart. Energy was delivered until the tissue conductance between the two electrodes became constant. RESULTS: A total of 30 lesions were performed. Average ablation time for all lesions was 9.2+/-3.9 seconds with a mean peak temperature of 48.7+/-5.8 OC. Pacing studies demonstrated 100%(30/30) isolation and staining showed that all lesions were transmural. CONCLUSIONS: Epicardially delivered bipolar RF energy was able to reproducibly isolate atrial myocardium. As opposed to other energy sources, lesions were always transmural and can be created within seconds. On-line measurement of conductance correlates with lesion transmurality. This technology has the potential to perform a beating heart MAZE procedure.