Introduction: Cryoablation therapy for pulmonary vein isolation (PVI) to treat paroxysmal atrial fibrillation (PAF) is well established. A novel 28 mm cryoballoon system designed to operate under low pressure to safely reach a lower nadir temperature and maintain constant balloon size during cooling has not been prospectively studied in a large patient population for safety and efficacy. The FROZEN AF (NCT04133168) trial was an international multi-center, open-label, prospective, single-arm study on the safety and performance of a novel cryoballoon system for treatment of PAF. Methods and Results: The study enrolled patients at 44 sites in 10 countries across North America, Europe, and Asia. Subjects were indicated for PVI treatment of PAF and had failed or were intolerant of 1 or more antiarrhythmic drugs. Procedural outcomes were defined based on the 2017 HRS consensus statement. Follow-up was performed at 7 days, 3, 6, and 12 months. Data are reported as mean±SD or Median (IQR). PVI was performed with a 28mm cryoballoon in 325 drug refractory PAF patients. Complete PVI was achieved in 95.7% of patients. In cryoablation lesions longer than 60s, 60.1% of PV isolations required only a single cryoballoon application. Procedure related complications included: phrenic nerve palsy [transient 4 (1.2%), persistent 0 (0.0%)], cardiac tamponade/perforation 2 (0.6%), and air embolism 1 (0.3%). Freedom from documented atrial arrhythmia recurrence at 12 months was 79.9% (AF 82.7%, AFL 96.5%, AT 98.1%), Antiarrhythmic drugs (AAD) were continued or re-initiated in 26.8% of patients after the 3-month blanking period. Additionally, an extension arm enrolled 50 pts for treatment with 28/31mm variable size cryoballoon. A single temporary PNP occurred in this group, which resolved prior to discharge. Freedom from documented recurrence at 12 months in these pts was 82.0%. Conclusions: This novel cryoballoon may facilitate PVI to treat PAF, providing more options to address the variety of anatomy present in patients with PAF. This cryoballoon system was safe and effective for treatment of patients with drug refractory or drug intolerant PAF.

Reply by Casella et al to Letter Regarding Article,

Introduction: Left atrial posterior wall isolation (LAPWI) is often performed in addition to pulmonary vein isolation (PVI) to improve outcome in patients with persistent atrial fibrillation (AF). In this setting, LAPWI + PVI using cryoballoon ablation had comparable results with radiofrequency ablation (RFA). The aim of the study is to evaluate the feasibility and safety of a new cryoballoon ablation system in PVI + LAPWI isolation, comparing it with the historical platform. Methods: The study was a prospective, non-randomized, single center study. Forty consecutive patients, undergoing PVI + LAPWI with the novel POLARx™, were compared to 40 consecutive patients who underwent the same procedure with the established Arctic Front Advance PRO™. Results: Acute isolation was achieved in all PVs in both groups and LAPWI was achieved in 38 patients (95%) in the POLARx group and in 36 patients (90%) in Arctic Front group. Procedural outcomes were similar between the two groups, except for lower temperatures during cryoapplications in the POLARx group, for both PVI and LAPWI. The complication rate was low and similar between groups. Conclusion: LAPWI+PVI with the novel POLARx™ Cryoballoon is feasible and safe; the results are comparable with the Arctic Front Advance PRO™ system.