Fig. 1. Electrocardiograms of the patient. (A) 12-lead ECG morphology showed a wide QRS complex tachycardia with LBBB morphology and superior axis. Intracardiac tracing demonstrated VA dissociation, which rendered the diagnosis of supraventricular tachycardia less likely. (B) ECG during sinus rhythm showed T wave inversion of precordial leads from V1-V4. (C) SAECG showed positive depolarization abnormalities, including fQRS, duration of terminal QRS <40 µV, and RMS voltage in terminal 40 ms. ECG: electrocardiogram, LBBB: left bundle branch block, VA: ventricular arrhythmia, SAECG: signal-averaged electrocardiogram, RMS: root means square.
