Limitations:
FROZEN AF is a large, multicenter, multicountry prospective trial to assess the safety and effectiveness of POLARx for cryoablation of PAF in drug-refractory patients. While all endpoints were met and the study conclusions are clear, the trial design has limitations: 1) This study enrolled drug refractory PAF patients, thus did not directly address use in other patient populations, such as those with persistent AF or patients with early AF that have not yet been on AADs, 2) Though the study was conducted with a primary arm of 325 patients that received PVI with POLARx and an extension arm of 50 pts treated with the variable size POLARx FIT, it was essentially a single arm design and did not directly compare cryoablation to alternative therapies, 3) The trial was run across 55 centers with a wide range of patients treated per center with a minimum of 1 and a maximum of 48. Thus, many operators were relatively inexperienced with the device. While this precluded examination of learning curves, as few operators treated enough patients to make examination of procedure times or outcomes over time meaningful, the high freedom from recurrence with so little device use speaks to the ease of use of the device. 4) Additionally, the size of the extension arm limits the conclusions that can be reached about the novel variable size cryoballoon, which allows ablation at either 28mm or 31mm without catheter change out. To better understand how this new option may transform workflow and patient outcomes, future studies should examine acute and chronic endpoints in larger patient cohorts.