Main Findings
The main findings were as follows. First, the IDF threshold to restore SR in patients with persistent AF was significantly decreased after the RFCA. Second, the IDF threshold in the no-recurrence group was significantly lower than that in the AF recurrence group, however, before the RFCA, there was no difference in the IDF threshold between the recurrence and no-recurrence groups. Third, the outputs of the IDF (threshold > 5 J) after RFCA were an independent predictor of a recurrence of AF.