Safety
The present study reports a safety event free rate of 96% in the primary cohort, and 100% in the extension arm. The landscape of adverse events associated with cardiac ablation procedures has consistently improved from radiofrequency ablation, to irrigated RF, cryoablation, and pulsed field ablation. Early, landmark cryoablation trials demonstrated that though RF and cryoablation have similar overall adverse event rates, the primary adverse events in cryoablation were PV stenosis and phrenic nerve impairment, but more serious extremely rare events , like atrioesophageal fistula, could occur.3,4Technical and procedural advancements have reduced PV stenosis to negligible levels and use of esophageal temperature monitoring has significantly reduced esophageal damage (as well as AE fistula). Phrenic nerve impairment remains at an incidence of 2-4%,5varying based on definition (transient, temporary, chronic, or permanent), with permanent phrenic nerve palsy thought to occur in less than 1% of patients.5 The present study saw zero permanent phrenic nerve palsy , with all patients recovering, and a lower rate of temporary phrenic nerve impairment in the FIT extension arm. This observation may be attributable to multiple factors. One, DMS was recommended in this study, the integrated DMS sensor may allow better detection of early transient PNI during ablation, resulting in lower overall rates of PNP. Two, the lower pressure and controlled pressure during ablation of this cryoablation system may allow better contact to PV tissue avoiding seating of the balloon deep into the PVs. Three, the 31mm configuration in particular may allow a more antral positioning and thus further from the phrenic nerve.