Background 
Cryoballon ablation is highly effective to achieve acute pulmonary vein isolation (PVI). However, repeat ablation of patients with atrial fibrillation (AF) recurrence revealed a relevant number of pulmonary vein (PV) reconnections.

Objective 
The purpose of this study was to investigate whether the negative temperature (°C) to time (sec.) (TTT) catch up during freezing with the second-generation cryoballon (CB2) is associated with durable PVI.

Methods 
All patients with symptomatic AF recurrences and repeat ablation using high-density mapping (January 2018 to April 2020) after previous cryoballon ablation were enrolled. Procedural data of 186 PVs, including 2 left common ostia, were assessed.

Results 
47 patients (male: 62%; median age: 60 years) underwent repeat ablation using high-density mapping after a mean of 367±244 days. 56 PVs (30.1%; 1.2 per patient) in 38 patients (80.9%) showed PV reconnection. Temperature at 30 sec., at 60 sec. and nadir temperature of the initially performed PVI were significantly lower in durable isolated PVs, whereas thaw time (-30 C° to 15 °C; sec.) was significantly longer. Temperature ≤40 °C at 60 sec. (49% vs. 18%, p<0.0001), time to isolation (TTI) ≤ 60 sec. (55% vs. 23%, p<0.0001) and TTT catch up (58% vs. 7%, p<0.0001) were significant more common in durable isolated PVs. In the multivariate analysis, thaw time (HR 1.1, p<0.01) and TTT catch up (HR 8.2, p<0.01) were the only independent predictors of durable PVI.

Conclusion 
Temperature to time catch up significantly predicts PVI durability in patients with arrhythmia recurrence after cryoballon ablation.