Evaluation of the SVC area
The patients were followed up periodically in an outpatient clinic, and were evaluated for episodes of AF recurrence based on regular 12-lead electrocardiograms at 1, 4, 7, 10 and 13 months after the ablation, and an event recordings (Spiderflash-TTM; Japan Lifeline Co., Ltd. Tokyo, Japan) at 3, 6, and 12 months after the ablation. The SVC area was evaluated four months after the ablation via a contrast-enhanced CT scan (Figure 2A). The SVC area was measured by tracing at the isolation line with a commercially available software program (Ziostation2; Ziosoft, Inc., Tokyo, Japan). Cases with dimensional reduction > 50% were followed up and re-evaluated.