Cryoballoon Ablation Procedure
Index Procedure: Procedural guidance (described here) was provided to inform use of the novel study device, but in general procedures were performed in accordance with local standard of care at physician discretion.
Dosing recommendation: Cryoapplications were recommended based on an algorithm measuring time to isolation (TTI), with a 180s application where TTI occurred in less than 60s and a 240s application where TTI occurred after 60s or was not detected, but the duration and number of cryoapplications was at physician discretion.
Esophageal management: Esophageal monitoring was required with a recommended cut-off temperature of 20°C.
Phrenic Monitoring: Phrenic nerve monitoring with the integrated DMS (Diaphragm Movement Sensor) was recommended, in conjunction with local standard of care monitoring. The integrated DMS allows the physician to monitor the amplitude of paced electromyogram like potential based movement recorded from an external sensor and visible as real time changes in amplitude on the cryoablation system, with an adjustable threshold and automatic recommendations to stop the cryoablation if the electrogram amplitude decreases by a pre-set percentage, see Supplement. In this study the DMS was recommended to be set at 65%. Phrenic nerve impairment was confirmed with a “sniff test” or radiography during the index procedure, discharge, and follow-up visits until resolved.
PVI Procedure: Procedural guidance (described here) was provided to inform use of the novel study device, but in general procedures were performed in accordance with local standard of care at physician discretion. Cardioversion was performed at operator discretion. Anti-coagulation was recommended to be uninterrupted or minimally interrupted prior to procedure. PVI procedures were conducted based on local standard of care and cryoablation system instruction for use. Acute success was confirmed by entrance and exit block, lack of confirmed or recorded block was reported as acute procedural failure.
Additional ablations: Additional ablation of non-PV foci that initiate AF (including locations in the left atria, right atrium, or superior vena cava), targeting complex fractionated electrograms or ganglionated plexi or performing LA mitral isthmus or roof lines was not allowed. Additional ablation of the cavo-tricuspid isthmus (CTI) with a market approved RF catheter was allowed in cases where typical atrial flutter was documented by patient history or occurred during the case (either spontaneously or inducible).
Redo Ablations: One repeat ablation was allowed during blanking, use of ‘non-study’ device for redo was considered a failure.
Follow-Up: Follow-up was performed at discharge, 7 days, 3 months, 6 months, and 12 months post index procedure. Trans telephonic monitoring (TTM) was collected by patients 2 times per month (either symptomatic or asymptomatic) from 3 to 12m post procedure. Only 43 subjects had monitoring related deviations. 24h Holter monitoring was provided at the 12m FU visit.