Background : The optimal dosage for cryoablation of atrial fibrillation (Cryo-AF) is still unknown. To evaluate the efficacy of an individualized freeze duration, we compared the clinical outcome of patients treated with a time-to-pulmonary vein isolation (TT-PVI) or temperature-guided ablation protocol to the outcome of patients treated with a conventional ablation protocol.
Methods: A total of 164 consecutive patients were included in the study. One method employed was a conventional dosing protocol (at least 2 applications of 180 seconds each)(the Cryo-AF Conventional group n=84), and the second method had a shorter protocol that was based on the TT-PVI or achievement of -40°C within 60 seconds (the Cryo-AF Dosing group n=80).
Results: We treated 656 pulmonary veins (PVs) with 1420 cryotherapy applications. The mean number of applications per patient was 8.7±0.8, with no difference between groups (Cryo-AF Conventional , 8.7±0.8 versus Cryo-AF Dosing ,8.6±0.8; P =0.359). The Cryo-AF Dosing group required significantly less total cryotherapy application time (990.60±137.77versus 1501.58±89.60 seconds; P <0.001) and left atrial dwell time (69.91±6.91 versus 86.48±7.03 minutes; P <0.001) than the Cryo-AF Conventional group. Additionally, the Cryo-AF Dosing group required significantly less total procedure time (95.03±6.50 versus 112.43±7.11 minutes; P <0.001). We observed acute ATP-induced or spontaneous vein electric reconnections in 13 veins (1.98%) after 20 minutes. The reconnection rates between the Cryo-AF Conventional and Cryo-AF Dosing groups were similar in that 2.98% and 0.94% of the initially isolated veins were reconnected, respectively, ( P =0.061). There was no difference in the recurrence rate of free atrial arrhythmia after a 1-year follow-up, which were 78.75% in the Cryo-AF Dosing group versus 78.57% in the Cryo-AF Conventional group ( P =0.978).
Conclusion: A novel Cryo-AF dosing protocol guided by temperature or the TT-PVI can be used to individualize an ablation strategy. This new protocol can lead to a significant reduction in duration of the procedure, the cryoenergy dosage and the left atrial dwell time. The procedure had equal safety and similar acute and 1-year follow-up outcomes compared to the conventional approach.