Comparison of high power, medium power, and irrigated-tip ablation strategies for pulmonary vein isolation in a canine model

Background: We sought to compare the efficacy and collateral damage during pulmonary vein (PV) isolation in a canine model using three different ablation strategies. Methods: Normal dogs (three each) were randomized to high power (70 W, 20 seconds, 60°C, Hi), medium power (50 W, 60 seconds, 50°C; Med), or irrigated-tip (35 W, 60 seconds, 45°C; Cool) ablation. Two transseptal punctures were performed and right and left superior PV electrical isolation was performed using the assigned ablation strategy. Animals survived for 30 days. Results: There was no difference in the number of lesions required to achieve PV isolation (Hi vs Med vs Cool; 43 vs 38 vs 44 lesions; P = NS). At sacrifice, Hi and Med lesions showed gross evidence of endocardial cratering and eschar formation. Corresponding histopathology showed transmural atrial necrosis with granulation tissue and fibrosis. Cool lesions demonstrated superficial endocardial white patches. The corresponding histopathology was subendocardial fibrosis with full and partial thickness necrosis of the atrial wall. One Hi animal had a large thrombus adherent to the left atrial wall above the left superior PV. PV stenosis was noted in one of three Hi and one of three Med, and none of three Cool. There were visible burns to the lung overlying the left atrial wall in one of three Hi, one of three Med, and none of three Cool. The esophagus demonstrated no evidence of serosal injury. Conclusions: The Hi and Med power 8-mm-tip ablation strategies for achieving PV isolation appear to result in excessive tissue destruction. Irrigated-tip lesions resulted in less endocardial eschar formation, PV stenosis, and damage to collateral structures.