Thawing plateau time indicating the duration of phase transition from ice to water is the strongest predictor for long-term durable pulmonary vein isolation after cryoablation for atrial fibrillation

Type of funding sources: Foundation. Main funding source(s): Helse Vest, Norway (LBS), and the Research Council of Norway (SYC). Cryoballoon ablation is an important method for pulmonary vein (PV) isolation in treatment of atrial fibrillation (AF). Previous studies have shown that thawing time, but not freezing time or temperature, impacts PV reconnection during long-term follow-up. However, it is unknown whether the entire or only part of the thawing stage plays a critical role. This study aimed to clarify the relationship between the durability of PV isolation and the time of phase transition from ice to water indicated by thawing plateau (TP) time during a cryoballoon ablation. In this retrospective study, 241 PVs from 71 patients who underwent a repeat AF ablation 526 (IQR: 412, 675) days after a cryoballoon ablation were analyzed. The predictive value of procedural parameters for the durability of PV isolation were evaluated. Definitions of different phases of the temperature-time curve are shown in Figure 1. TP Time is defined as the time from 0 to 10°C inside the balloon in the thawing period (the plateau on the curve). Reconnection was observed in 101 (41.9%) PVs of 53 patients (74.6%). Durable PV isolation was associated with significantly longer TP Time compared with PV reconnection (26.0 vs. 11.0 s, P<0.001). The proportion of durable PV isolations increased with TP Time in a dose-proportional manner (Figure 2). The cut point for PV reconnection was TP Time <15 s with a positive predictive value of 82.1% (sensitivity=63.4%, specificity=90.0%) while for durable PV isolation the cut point was TP Time >25 s with a positive predictive value of 84.6% (sensitivity=55.0%, specificity=86.1%). After the analysis of multivariable logistic regression, location of PV (P<0.01), and TP Time (P<0.05) were shown as independent predictors for durable PV isolation. None of nadir temperature, initial cooling time, effective freezing time, initial thawing time, or late warming time was independent predictor. Accumulated TP Time for all PVs showed a positive linear correlation with the plasma level of troponin T (ρ=0.624, P<0.01). TP Time is an independent predictor for the durability of PV isolation, and it presents in a dose-proportional manner. TP Time <15 s predicts long-term reconnection while TP Time >25 s predicts durable PV isolation.