Catheter ablation protocol
The details of the catheter ablation protocol have been previously
published[6]. Under uninterrupted anticoagulants,
all patients underwent PVI and superior vena cava isolation (SVCI).
These were performed with geometric information based on reconstructed
3-D CT imaging system (CARTO 3, Biosense Webster, Inc., Diamond Bar,
CA). Two long sheaths with one circular multi-electrode catheter and a
3.5-mm open-irrigated tipped catheter (ThermoCool STSF; Biosense Webster
Inc., Diamond Bar, CA, USA) were used as ablation tools. To monitor the
esophageal temperature, a multi-electrode esophageal
temperature-monitoring probe was employed during the procedure
(Esophaster, Japan Lifeline, Tokyo, Japan).
The detail of radiofrequency power was 50 W with an upper limit
temperature of 42°C as recently denoted.[5]Disappearance of negative deflection in the unipolar electrogram
recorded at the distal tip of the ablation catheter (unipolar signal
modification, USM; Figure 1) was adopted as an indicator of sufficient
transmural necrosis.[4, 7] RFA was continued for
3–5 seconds after the USM in the segments other than those adjacent to
the esophagus (SAE). RF time was limited to 5 s or by the alert of the
temperature sensor (upper limit of 39°C) to avoid esophageal injury in
the SAE. During each RF application, the modification of the unipolar
atrial electrogram was monitored in real-time at a sweep speed of 200
mm/s and filtered with a 0.5–120 Hz by the CARTO system.
To clearly visualize unipolar signals, a 10-polar electrode catheter
with an indifferent electrode (DECANAV®, Biosense
Webster Inc., Diamond Bar, CA, USA) in the coronary sinus was used,
where a reference annotation signal was recorded from the bipolar
signals. Targeted lesion distance was <5 mm and contact force
(CF) was aimed at 5–20 g (target 10 g) and at <10g in the
segments other than SAE and in the SAE, respectively. RFA was stopped at
3 s after the USM in case CF was above 15 g or catheter was
perpendicularly placed on the atrial wall. RFA was continued for 5 s
after the USM if CF was below 10 g or RFA site was near the carina.
Intensive induction of atrial overdrive pacing with isoproterenol
infusion and the confirmation of the absence of dormant conduction with
adenosine-triphosphate (ATP) infusion was attempted. The confirmation
was conducted for at least 20 min after the isolation of the ipsilateral
PV pair.