Efficacy and safety of circumferential pulmonary vein isolation using a novel cryothermal balloon ablation system

OBJECTIVES We sought to evaluate the efficacy and safety of a novel cryothermal balloon ablation system in creating pulmonary vein (PV) isolation. BACKGROUND Pulmonary vein isolation using standard radiofrequency ablation techniques is limited by procedure-related complications, such as thrombus formation and PV stenosis. Cryothermal ablation may reduce the risk of such complications. METHODS Eight dogs underwent circumferential ablation of both superior PVs for either 4 or 8 min using a cryothermal balloon catheter (CryoCath Technologies Inc., Kirkland, Canada). Both fluoroscopy and intracardiac ultrasound (ICE)-guided balloon and Lasso catheter positioning at the PV ostia assessed short-term PV integrity. In six additional dogs, long-term PV integrity was assessed by computed tomography at 16 weeks after ablation. RESULTS Successful electrical isolation was achieved acutely in 14 of 16 (87.5%) PVs and was confirmed in one-week survival studies in 10 of 12 (83%) PVs. Successful isolation was higher in the absence of any peri-balloon flow leak as seen by ICE (p = 0.015), and with balloon temperatures <= 80 degrees C (p = 0.015). Cryolesions were located at the veno-atrial junction and were homogeneous, with intact endothelium and free of thrombus formation. Although limited angiographic PV narrowing was noted in the early follow-up period, no significant PV narrowing was seen long-term. Right phrenic nerve injury was seen in 50% of the animals studied at one week. CONCLUSIONS This novel cryothermal balloon ablation system is effective for isolating PVs, but injury to the right phrenic nerve was noted in this early experience. Further studies are needed to assess the long-term efficacy and safety of this technique.