2.3 Electrophysiologic study with 3D voltage mapping
All antiarrhythmic drugs had been discontinued for at least 5 half-lives, and the electrophysiologic study with voltage mapping was performed under conscious sedation achieved with dexmedetomidine, propofol, and fentanyl.8,9 Two long sheaths (an Agilis steerable sheath and an SL0 sheath; St. Jude Medical Inc., St. Paul, MN, USA) were positioned in the LA, and LA pressure was measured. An activated clotting time >300 seconds was maintained during the procedure by administration of heparin. The study was performed with use of a 3D mapping system (CARTO 3, Biosense Webster, Diamond Bar, CA, USA) and a multispline catheter with 2-mm interelectrode spacing (Pentaray NAV; Biosense Webster).
High-density electroanatomical maps were obtained during sinus rhythm. If the patient was in AF rhythm, low energy (10–20 joules) intracardiac cardioversion was performed with use of a BeeAT catheter (Japan Lifeline, Tokyo, Japan) placed in the coronary sinus. Bipolar signals were acquired, with a high-pass filter set at 30 Hz and low-pass filter set at 500 Hz. LVZs were identified as areas with a bipolar peak-to-peak voltage amplitude of <0.5 mV.4‑7,10,11 In addition, the ascending aorta was reconstructed by means of the 3D mapping system and merged with the LA voltage map. The electroanatomical maps were merged with the CT images that had been obtained.
For the purpose of the study, we measured the LVZs on the anterior LA wall in the areas of contact between the LA and the ascending aorta and sinus of Valsalva.