Introduction: There is increasing evidence of the epicardial connection between the right-sided pulmonary vein (PV) carina and right atrium interrupts right-sided PV isolation after circumferential PV ablation in patients with atrial fibrillation. In such cases, carina ablation is often required. This study aimed to assess the utility of the right atrial posterior wall (RAPW) pacing in the detection of the right-sided epicardial connection (EC), evaluate the requirement for additional carina ablation after circumferential pulmonary vein (PV) ablation depending on the presence of EC, and investigate the clinical characteristics including the amount of epicardial adipose tissue (EAT) in patients with ECs. Methods and Results: Forty-one patients scheduled for PV isolation were enrolled. Before ablation, activation mapping of the LA was prospectively performed during pacing from the RAPW. EC was observed in 12 patients (EC group, 29%), whereas no EC was observed in the remaining 29 patients (non-EC group, 71%). For PV isolation, carina ablation was required in addition to circumferential ablation in 7 patients (58%) in the EC group, compared to 2 patients (7%) in the non-EC group (p < 0.003). Periatrial and intercaval EAT volumes were significantly lower (12.8 ± 6.2 vs. 23.1 ± 13.9 ml/m 2, p < 0.02, and 1.1 ± 0.8 vs. 2.2 ± 1.6 ml/m 2, p< 0.02, respectively) and the patients were younger (66.5 ± 6.6 vs. 72.4 ± 8.3 years, p < 0.03) in the EC group than in the non-EC group. Conclusions: RAPW pacing revealed EC between the RA and right PV carina in nearly a quarter of the patients.