Verification of a novel atrial fibrillation cryoablation dosing algorithm guided by time-to-pulmonary vein isolation: Results from the Cryo-DOSING Study (Cryoballoon-ablation DOSING Based on the Assessment of Time-to-Effect and Pulmonary Vein Isolation Guidance)

BACKGROUND There are no recommendations on the optimal dosing for cryoablation of atrial fibrillation (Cryo-AF). OBJECTIVE The purpose of this study was to develop and prospectively test a Cryo-AF dosing protocol guided exclusively by time-topulmonary vein (PV) isolation (TT-PVI) in patients undergoing a first-time Cryo-AF. METHODS In this multicenter study, we examined the acute/longterm safety/efficacy of Cryo-AF using the proposed dosing algorithm (Cryo-AF(Dosing); n = 355) against a conventional, nonstandardized approach (Cryo-AF(Conventional); n5400) in a nonrandomized fashion. RESULTS Acute PV isolation was achieved in 98.9% of patients in Cryo-AFDosing (TT-PVI 5 48 +/- 16 seconds) vs 97.2% in CryoAF(Conventional) (P =.18). Cryo-AFDosing was associated with shorter (149 6 34 seconds vs 226 +/- 46 seconds; P<001) and fewer (1.7 +/- 0.8 vs 2.9 +/- 0.8; P<001) cryoapplications, reduced overall ablation (1665 minutes vs 40 +/- 14 minutes; P<001), fluoroscopy time (1366 minutes vs 29613 minutes; P<001), left atrial dwell time (51 +/- 14 minutes vs 118 +/- 25 minutes; P<001), and total procedure time (84 +/- 23 minutes vs 145 +/- 49 minutes; P<001) but similar nadir balloon temperature (-47 degrees C 6 8 degrees C vs -48 degrees C 6 6 degrees C; P =.41) and total thaw time (436 27 seconds vs 45 +/- 19 seconds; P =.09) as compared to Cryo-AF(Conventional). Adverse events 2.0% vs 2.7%; P =.48), including persistent phrenic nerve palsy (0.6% vs 1.2%; P =.33) and 12-month freedom from all atrial arrhythmias (82.5% vs 78.3%; P =.14), were similar between Cryo-AF(Dosing) and Cryo-AF(Conventional). However, Cryo-AF(Dosing) was specifically associated with fewer atypical atrial flutters/tachycardias during long-termfollow-up (8.5% vs 13.5%; P=.02) as well as fewer late PV reconnections at redo procedures (5.0% vs 18.5%; P< 001). CONCLUSION A novel Cryo-AF dosing algorithm guided by TT-PVI can help individualize the ablation strategy and yield improved procedural endpoints and efficiency as compared to a conventional, nonstandardized approach.