Impact of freezing time and balloon size on the thermodynamics and isolation efficacy during pulmonary vein isolation using the second generation cryoballoon.

BACKGROUND The differences in ablation characteristics of freezing time and balloon size using second generation cryoballoon are still unknown. METHODS AND RESULTS Twenty-six dogs underwent pulmonary vein (PV) isolation. Balloon and tissue temperatures (left atrial-PV junction, phrenic nerve, and internal esophagus) were monitored. The ablation duration was randomized to either 3 or 4 minutes, which did not show significant differences in temperature profiles, PV isolation success rate, complications, or histological changes. Twenty dogs underwent cryoablation using 28-mm cryoballoon, 6 dogs were done using the 23-mm cryoballoon. Positioning of the 23-mm cryoballoon was more distal in the PV, which resulted in better PV occlusion. Temperature profiles showed lower temperatures in the 23-mm cryoballoon than in the 28-mm cryoballoon (inner balloon, median [range]: -51.5 [-66.0 to -31.0] versus -43.0 [-64.0 to -26.0]°C, P<0.001; balloon surface: -43.0 [-60.0 to -15.8] versus -6.5 [-46.2 to 28.9]°C, P<0.001; left atrial-PV junction: -6.7 [-20.0 to 21.4] versus 15.8 [-14.4 to 35.1]°C, P<0.001), and trended toward a higher PV isolation success rate in the 23-mm cryoballoon. Histologically, deeper extensions of ablative lesions into the PV were seen with 23-mm cryoballoon, and larger ablative lesions were seen in the left atrial antrum using 28-mm cryoballoon. CONCLUSIONS The efficacy of 3-minute ablation was not significantly different from 4-minute ablation in dogs. The 23-mm cryoballoon had a greater cooling effect than the 28-mm cryoballoon for small PVs, but showed narrower ablative lesions in the left atrial antrum.