SVC isolation
Empirical SVC isolations were performed in the first AF ablation session. The SVC potentials were recorded by a variable 20 polar, circular mapping catheter (7F Inquiry OptimaTM PLUS Catheter; Abbott, St Paul, Minnesota, USA) at the level of the lower border of the right pulmonary artery after SVC venography. The isolation line was set at the level of the lower border of the right pulmonary artery to avoid sinus node injury (Figure 1A). Phrenic nerve (PN) capture sites were confirmed following the execution of 5 V pacing protocols. The SVC was ablated on a point-by-point manner with an irrigated ablation catheter (FlexabilityTM; Abbott, St Paul, Minnesota, USA). Radiofrequency (RF) pulses (25 W) were applied for 30 s, and they were delivered circumferentially with the exceptions of the PN (Figure1B). If the SVC potential remained after the circumferential isolation, additional PN capture site applications were delivered for 20 s at 20 W, while the diaphragmatic movement was evaluated with fluoroscopy. The endpoint of SVC isolation was bidirectional block between the SVC and the atrium. Dormant SVC conduction was induced following the administration of adenosine triphosphate (20 mg) in the cases at which SVC automaticity was noticeable during the ablation process.