Electrophysiological Study
All antiarrhythmic drugs were discontinued for at least five half-lives, except for amiodarone, which was stopped at least two weeks before the procedure. Transesophageal echocardiography was performed to exclude the presence of thrombus in left atrial appendage prior to the procedure. Electrophysiology study was performed under conscious sedation and local anesthesia. Twelve-lead surface electrocardiograms (ECG) (filtered 0.05-100Hz) and bipolar intracardiac electrograms (filtered 30-250Hz, sweep speed 100 mm/second) were amplified and displayed on a computer-based digital amplifier/recorder system (Bard Electrophysiology, Lowell, MA, USA).
Following vascular access, a 6F quadripolar electrode was placed in the right ventricular apex, and a 6F decapolar catheter was positioned in the coronary sinus via the left femoral vein. One 8.5F long sheath was advanced into the right atrium through the right femoral vein. A transseptal puncture was performed in the patients with AT originating from left atrium. Regular doses of heparin were administered to maintain an activated clotting time of 300-350 seconds throughout the whole procedure.