Limitations
This study had some potential limitations. First, it was a retrospective and observational study at a single institute. We did not have many patients with persistent AF, which might have caused a statistical bias. Second, we did not perform a substrate ablation such as a line, complex fractionated atrial electrogram (CFAE), rotor, and LVZ ablation. However, recent studies have revealed that only the efficacy of the PVI has been proven.25-28 In this study, there was no significant difference in the non-PV foci between the two groups. Third, we also considered the effects of the confounding predictors for AF recurrence. However, the IDF threshold was a useful predictor for AF recurrence because the IDF remained after a multivariate analysis after adjusting for the patient factors.