Epicardial Pulmonary Vein Isolation: A Long-Term Histologic and Imaging Animal Study Comparing Cryothermy Versus Radiofrequency

Background Simplifications of the Cox-Maze procedure to treat atrial fibrillation (AF) include epicardial pulmonary vein (PV) isolation using various sources to create lines of conduction block. The creation of transmural lesions has been a concern. The heat-sink effect caused by blood flow has limited the effectiveness of unipolar radiofrequency and linear application of cryothermy, which should be abolished when clamp devices are used for PV isolation. The efficacy and safety of epicardial beating-heart PV isolation with clamp devices using cryothermy or bipolar radiofrequency energy was studied. Methods Twelve domestic pigs underwent beating-heart epicardial PV isolation using cryothermy (n = 6) or radiofrequency (n = 6) energy. Follow-up was 30 days for 3 animals of each group and 90 days for the others. Lesions were assessed by epicardial pacing, cardiac magnetic resonance imaging (MRI), and histologic analysis. Results Immediate and long-term electrical isolation of PVs was achieved with both energy sources. Histologic analysis showed transmural lesions in all animals at 30 and 90 days. Cardiac MRI showed no evidence of PV stenosis or thrombus formation. Mean left atrial ejection fraction was 0.36 ± 0.01, 0.36 ± 0.02, and 0.36 ± 0.01 at baseline and at 30 and 90 days, respectively (p = 0.360 and 0.230, respectively) and not significantly different with cryothermy or radiofrequency ablations. Conclusions Beating-heart PV isolation using epicardial cryothermy or radiofrequency ablation produces transmural lesions with complete electrical conduction block, with low or no risk of endocardial thrombosis or PV stenosis. This approach may be useful for PVI in selected patients with AF caused by PV triggers.