Miyazaki S, Horie T, Hachiya H, et al. - Given a need for repeat procedures following second-generation cryoballoon pulmonary vein isolation (CB-PVI) has been reported in 10%-15% of patients with paroxysmal atrial fibrillation (PAF), researchers investigated the mechanisms of recurrences post-cryoballoon ablation. From 122 PAF patients who underwent second procedures for recurrent arrhythmias 7.0 (4.0-12.0) months following the CB-PVI, data were obtained and analyzed. Exploration of non-PV AF foci was done with isoproterenol, adenosine, and repetitive cardioversions, during second procedures. According to the findings, an improved single procedure outcome in cryoballoon ablation might be achieved through improvement in the upper PV PVI durability, eliminating arrhythmogenic superior vena cavae and coexisting atrial arrhythmias, and bonus cryoballoon applications at PV antra.