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.