Effect of pulmonary vein cryoballoon ablation in dogs with coolant-nitrogen

BACKGROUND: The Arctic Front Advance System with nitrous oxide (N(2)O) refrigerant is the leading system for the cryoballoon ablation of atrial fibrillation (AF). A novel cryoablation system with nitrogen (N(2)) refrigerant was developed with technical improvements seeking to improve outcomes. Cryoballoon ablation with the N(2) refrigerant may be effective and safe for pulmonary vein isolation (PVI). METHODS: In total, 16 dogs were included in the study, of which 13 underwent PVI procedures, and 3 served as baseline controls. Cryoballoons (Cryofocus, Int.) with N(2) refrigerant were used for the study group, which comprised 8 dogs, and second-generation cryoballoons with N(2)O refrigerant (Arctic Front Advance; Medtronic, Inc., MN, USA) were used for the control group, which comprised 5 dogs. Three dogs of the study group and 2 dogs of the control group were euthanized on the same day post-ablation. The other 8 dogs of the two groups were euthanized 1 month post-ablation. The removed organs were examined for gross anatomy and histological review. RESULTS: The average ablation times for each pulmonary vein (PV) in the study group were less than those in the control group (1.1±0.3 vs. 2.0±0.8; P=0.006). The procedure duration of the study group was shorter than that of the control group (379±46 vs. 592±162 s; P=0.013). And the time to isolation (TTI) was similar between the groups. The PVI rate of the single-ablation was higher in the study group than the control group (92.9% vs. 60.0%; P=0.05). In relation to safety, there was no evidence of thrombus, esophageal injury, or pericardial tamponade in any of the dogs. Only 1 incidence of self-limited phrenic nerve paralysis (PNP) was observed in the control group. CONCLUSIONS: The novel cryoablation system with the N(2) refrigerant had better efficacy than and similar safety to that of the system (Medtronic, Int.) with the N(2)O refrigerant.