Limitations
First, because this was a retrospective observational study with a relatively small number of patients, biases common to non-randomized studies could not be eliminated. Second, we excluded patients who could not return or maintain sinus rhythm before PVI. Therefore, the prevalence of an EC in the total AF ablation cohort remains unknown. In addition, we confirmed the presence of an EC during RA pacing by Ripple mapping and Coherent mapping. If we had changed the pacing site in each case, we might have detected more or lesser ECs. In the EC-negative group, eight patients required additional carina ablation. In these cases, an EC might have been overlooked. This may partly explain the low success rate of first-pass isolation in the EC-negative group. Third, the duration of follow-up was relatively short, and there were only two cases in which the second procedure was performed. We could not evaluate long-term outcomes and PVI durability in this study.