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Evidences of the carina area between the superior and inferior pulmonary veins (PVs) have been shown the importance on catheter ablation for atrial fibrillation (AF). However, electrical structure of the intervenous isthmus of PVs has not been elucidated fully.Methods: Thirty-six AF patients underwent extensive PV isolation (EPVI). Electrical connections of contiguous intervenous area were estimated with two ring catheters and 3D navigation system before and immediately after completion of EPVI.Results: Continuous pacing at the multisite of ipsilateral PVs revealed intervenous connection at the carina zone in 62.5% of left and 84.6% of right PVs. The courses of electrical connections were classified into three types. Cross band conduction from superior-anterior to inferior-posterior was observed in 31.3% and 38.5%, superior-posterior to inferior-anterior in 12.5% and 15.4%, and presumed epicardial conduction in 12.5% and 38.5% of left and right PVs, respectively. Completion of simultaneous isolation of ipsilateral PVs were higher observed in PVs with intervenous conduction than in PVs without connection (88.9% vs 28.6% in left, 100% vs 71.4% in right, respectively p