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.