Index ablation procedure
The ablation procedure was performed as previously
described.6 In brief, the procedure was performed
under general anesthesia. A single transseptal puncture was made under
fluoroscopic and intracardiac echocardiographic (Acuson and AcuNav;
Biosense Webster, Diamond Bar, CA, USA) guidance. A 28-mm cryoballoon
catheter (Arctic Front Advance; Medtronic, Minneapolis, MN, USA) was
introduced into the LA through a steerable sheath (Flexcath Advance;
Medtronic) with a circular mapping catheter (Achieve; Medtronic).
Cryothermal energy was applied through a cryoballoon occluding each
pulmonary vein (PV). The compound motor action potentials of the
diaphragm provoked by phrenic nerve pacing were continuously monitored
during ablation of the right PVs. When a successful PVI was not achieved
solely by a cryoballoon, a touch-up ablation with an RF catheter
(FlexAbility or TactiCath; Abbott, Abbot Park, IL, USA) was performed.
Additional ablations were performed according to the operator’s
decision. When LA roof cryoballoon ablation was performed, an Achieve
catheter was inserted into the left and right superior PVs, and a
cryoballoon was shifted along the LA roof by changing the direction of
the steerable sheath and adjusting the position of the cryoballoon and
sheath so that each cryoballoon location overlapped with the previous
cryoballoon location. Cryoballoon ablation of the bottom line of the
LAPW was performed in the same manner, with the Achieve catheter
positioned in each inferior PV (Figure 1). Cryothermal energy was
applied for 180 to 240 seconds according to the operator’s decision.
Touch-up ablation of the LAPW with an RF catheter was permitted. LAPW
bottom line ablation was performed using an RF catheter. Cryoballoon
ablation was performed under luminal esophageal temperature (LET)
monitoring using esophageal temperature probes (Esophaster; Japan
Lifeline, Tokyo, Japan) with a cutoff value of 15°C. RF applications
were also prematurely interrupted when the LET reached 39°C. Linear
ablation at the cavo-tricuspid isthmus (CTI) was performed by delivering
RF energy from the tricuspid annulus to the inferior vena cava in a
point-by-point fashion. After each linear ablation, the status of the
conduction block was confirmed by an electrophysiological method, an
activation map, and a voltage map created with an electrical
impedance-based mapping system (Ensite NavX; Abbott). PVI was confirmed
using a duo-decapolar circular mapping catheter (EPstar Libero; Japan
Lifeline). All the procedures were performed by either of the two main
operators skilled with the technique.