AbstractBackgroundCryoballoon ablation is a first‐line therapy for atrial fibrillation. We compared the efficacy and safety of two ablation systems and addressed the influence of pulmonary vein (PV) anatomy on performance and outcome.MethodsWe consecutively enrolled 122 patients who were planned for first‐time cryoballoon ablation. Patients were assigned 1:1 for ablation with the POLARx or the Arctic Front Advance Pro (AFAP) system and followed‐up for 12 months. Procedural parameters were recorded during the ablation. Before the procedure, a magnetic resonance angiography (MRA) of the PVs was generated and diameter, area, and shape of each PV ostium were assessed. We applied an evaluated PV anatomical scoring system on our MRA measurement data ranging from 0 (best anatomical combination) to 5.ResultsProcedures performed with POLARx were associated with shorter time to balloon temperature −30°C (p< .001), lower balloon nadir temperature (p< .001), and longer thawing time till 0°C (p< .001) in all PVs, however, time to isolation was similar. We observed a decreasing performance with each increase in the score for the AFAP, whereas the POLARx performed constant regardless of the score. At 1 year, AF recurred in 14 of 44 patients treated with AFAP (31.8%) and in 10 of 45 patients treated with POLARx (22.2%) (hazard ratio, 0.61; 95% CI 0.28 to 1.37;p= .225). There was no significant correlation between PV anatomy and clinical outcome.ConclusionWe found significant differences in cooling kinetics, especially when anatomical conditions are difficult. However, both systems have a comparable outcome and safety profile.