Study population and study design
This study enrolled 141 consecutive patients with drug-refractory persistent AF (age 62.5 ± 10.3 years, 84.4% male), who underwent RFCA between January 2013 and December 2015, in our institute. Persistent AF was defined as AF that was sustained beyond 7 days (including long-standing persistent AF) according to the guidelines.12 The study patients were followed up for at least 1 year after the AF ablation.
If AF was terminated before the RFCA, we artificially induced AF by high rate burst pacing with a high dose ISP infusion (starting at 5 µg and increasing it up to 10 µg and 20 µg/minute), and we initially performed IDF to identify the earliest site of the trigger premature atrial contraction (PAC) with spontaneously occurring AF. Defibrillation was performed with an output of 1 J. If the defibrillation failed to restore SR with the low output, the output was gradually increased up to 30 J (1, 3, 5, 10, 15, 20, and 30 J). After the RFCA, we attempted pacing-induced AF again to provoke other focuses of AF. When AF was induced artificially, we performed IDF again to terminate the AF with outputs of 1 to 30 J after we waited for two minutes. A change of IDF threshold to restore SR before and after RFCA was assessed. Furthermore, we investigated the relationship between the IDF threshold and recurrence of AF after RFCA.
This clinical study was a retrospective analysis of prospectively collected AF ablation data. The study protocol was approved by the Institutional Review Board (IRB) of Toho University Medical Center Omori Hospital (approval number: M20068). This study was a retrospective observational study, carried out by the opt-out method on our hospital website.