Background: Cryoballoon (CB) based Pulmonary vein isolation (PVI) is an effective treatment option for patients with atrial fibrillation (AF). However the extension of created lesion sets adjacent to the pulmonary veins (PVs) remain unclear, especially when performing CB ablation with individualized time to isolation (TTI) protocols. This study sought to investigate the extension of lesions at the posterior wall and the roof of the left atrium (LA).

Methods and Results:  30 patients with paroxysmal or persistent AF underwent ablation with the fourth generation CB. Individual freeze-cycle duration was set at TTI+120 seconds. A total of 120 pulmonary veins (PV) were identified and all PVs were successfully isolated. 3D electroanatomical high density (HD) Maps of the LA were performed in every patient before and after PVI. Surface area of the posterior wall and LA- roof were measured and correlated to lesion extension after PVI.  After CB ablation 65.6±16.9 % of the posterior wall and 75.4±18.4% of the LA roof remained unablated. In addition, a non antral lesion formation was observed in every patient in at least one PV. Anterior antral parts of the superior PVs displayed after CB ablation greatest  unablated areas compared to the remaining antral areas .

Conclusion: High Density Re-Maps after CB based PVI demonstrated that main parts of the posterior wall and roof remained electrically normal and unaffected. Unablated antral areas were predominantly in the anterior parts of the superior PVs and may translate into recurrence of AF.