Electrophysiological study
Two quadripolar mapping catheters including a His bundle catheter and a right ventricular apex (RVA) catheter were placed via the right femoral vein under fluoroscopy guidance. A decapolar (inter-electode spaces being 2-8-2 mm) coronary sinus (CS) vein catheter was placed via the left/right femoral vein. Intracardiac electrocardiograms during sinus rhythm and arrhythmias were analyzed. EPS techniques including burst pacing, programmed stimulation (S1, S1S2, S1S2S3), right ventricular apex (RVA) entrainment, and His bundle refractory period premature ventricular stimuli were used for differential diagnosis.