Fig. 1
Protocol flowchart depicting cryoenergy dosing performed according to the TT-PVI or balloon temperature (Cryo-AFDosing group) or conducted with a conventional ablation protocol (Cryo-AFConventional group). In the Cryo-AFConventional group, cryoablation of 180 s was applieduntil bidirectional block of the vein was demonstrated. Following successful PVI, an additional 180-s freeze cycle was applied. In the Cryo-AFDosing group, the freeze duration was modified depending on the observed TT-PVI or balloon temperature. If a spontaneous TT-PVI was detectable, cryoenergy applications lasted for the TT-PVI plus 60–90 s. If the TT-PVI was < 60 s, a TT-PVI plus 60 s freeze cycle was applied. If the TT-PVI was between 60 and 90 s, a TT-PVI plus 90 s freeze cycle was applied. Additionally,if the TT-PVI was unavailable, according to the time from the beginning of ablation to the balloon temperature achievement of − 40 °C, cryoenergy of 120–180 s was applied until the vein was blocked. In other words, if the temperature reached − 40 °C within 60 s, a 120-s freeze cycle was applied, and if the temperature reached − 40 °C within 60–90 s, a 180-s freeze cycle was applied. In both cases, a 120-s bonus application was immediately administered. Cryo-AF = cryoablation of atrial fibrillation; PV = pulmonary vein; TT-PVI = time-to-pulmonary vein isolation; Time to − 40 °C, defined as the balloon freezing time from the beginning of the application to the moment of achievement of − 40 °C; 90S PVI, defined as pulmonary vein isolation in 90 s