2.3 Electrophysiologic study and voltage mapping
All antiarrhythmic drugs were discontinued for at least 5 half-lives before the ablation procedure. Electrophysiologic study was undertaken with patients under conscious sedation achieved with dexmedetomidine, propofol, and fentanyl.8,9 Two long sheaths (Agilis steerable sheath and SL0 sheath, St. Jude Medical Inc., St. Paul, MN) were positioned in the LA. Heparin was used to maintain an activated clotting time >300 seconds throughout the procedure.
For each patient, a high-density LA voltage map was created by means of a 3-dimensional mapping system (CARTO3, Biosense Webster, Diamond Bar, CA) and a multispline catheter with 2-mm interelectrode spacing (PentaRay NAV; Biosense Webster). The map was created during sinus rhythm, and if before ablation the patient was in AF rhythm, the map was created after sinus rhythm was restored by means of low-energy (10–20 joules) internal cardioversion performed with a catheter (BeeAT; Japan Lifeline, Tokyo, Japan) placed in the coronary sinus. Bipolar signals were acquired with a high-pass filter at 30 Hz and a low-pass filter at 500 Hz. For each of the 3 segments on the roof line and each of the 3 segments on the floor line where the CT-based measurements of LAPW thickness were obtained, voltage was measured at 3 sites closest to the ablation line, and the 3 measured voltages were averaged for the analysis (Figure 2). Obviously dull potentials, suggesting the electrograms were recorded by the catheter not in contact with the LA, were excluded. In addition, the modified AI was calculated for each of the 3 segments on both ablation lines.