• Jun Ding, Jing Xu, Wei Ma, Bingwei Chen, Peigen Yang, Yu Qi, Shan Sun, and Aijuan Cheng.
• Department of Cardiology, Tianjin Chest Hospital, Tianjin, People's Republic of China, 261 South Taierzhuang Road, Jinnan District, Tianjin, 300200, China.
• Bmc Cardiovasc Disor. 2019 Dec 17; 19 (1): 299.

BackgroundThe 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.MethodsA total of 164 consecutive patients were included in the study. One method employed was a conventional dosing protocol (at least 2 applications of 180 s each) (the Cryo-AFConventional 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 s (the Cryo-AFDosing 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-AFConventional, 8.7 ± 0.8 versus Cryo-AFDosing,8.6 ± 0.8; P = 0.359). The Cryo-AFDosing group required significantly less total cryotherapy application time (990.60 ± 137.77versus 1501.58 ± 89.60 s; P < 0.001) and left atrial dwell time (69.91 ± 6.91 versus 86.48 ± 7.03 min; P < 0.001) than the Cryo-AFConventional group. Additionally, the Cryo-AFDosing group required significantly less total procedure time (95.03 ± 6.50 versus 112.43 ± 7.11 min; P < 0.001). We observed acute ATP-induced or spontaneous vein electric reconnections in 13 veins (1.98%) after 20 min. The reconnection rates between the Cryo-AFConventional and Cryo-AFDosing 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-AFDosing group versus 78.57% in the Cryo-AFConventional group (P = 0.978).ConclusionA 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.

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