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.