Ablation procedure
The ablation procedure, previously described in
detail,10 was performed under general anesthesia. A
single transseptal puncture was created under fluoroscopic and
intracardiac echocardiographic guidance (Acuson, AcuNav, Biosense
Webster, Diamond Bar, CA). A 28-mm cryoballoon catheter (Arctic Front
Advance, Medtronic, Minneapolis, USA) was introduced into the LA through
a steerable sheath (Flexcath Advance, Medtronic) with a circular mapping
catheter (Achieve, Medtronic), and cryothermal energy was applied
through a cryoballoon, occluding each PV. The compound motor action
potentials of the diaphragm, provoked by phrenic nerve pacing, were
continuously monitored during CBA of the right PV to prevent phrenic
nerve injury. PVI was confirmed using a dual-decapolar circular mapping
catheter (EPstar Libero, Japan Lifeline, Tokyo, Japan). If successful
PVI was not achieved solely with a cryoballoon, touch-up ablation was
performed using an irrigated RF catheter (FlexAbility or TactiCath,
Abbott, Illinois). After successful PVI, linear ablation of the LA roof
was performed using a cryoballoon. An Achieve catheter was inserted into
the left and right superior PVs; the cryoballoon was shifted along the
LA roof by changing the direction of the steerable sheath and adjusting
the position of the cryoballoon and sheath, ensuring that each
cryoballoon location overlapped with the previous location. After CBA of
the LA roof, complete conduction block was confirmed based on activation
and voltage maps created via an electrical, impedance-based mapping
system (Ensite NavX, Abbott, Illinois), using a duo-decapolar circular
mapping catheter (EPstar Libero, Japan Lifeline, Tokyo) (Figure
2 ). If complete conduction block was not obtained after CBA, we then
performed touch-up ablation using an irrigated RF catheter. Cryothermal
energy was then applied for 180–240 s at the surgeon’s discretion. We
performed CBA under luminal esophageal temperature (LET) monitoring
using esophageal temperature probes (Esophaster, Japan Lifeline, Tokyo)
with a cutoff value of 15°C. RF applications were prematurely
interrupted when the LET reached 39°C.