Wide QRS Tachycardia With Left Bundle Branch Block Morphology: What Is the Mechanism?
A 55‐year‐old woman was referred for radiofrequency catheter ablation of narrow QRS tachycardia that was terminated with intravenous adenosine. Twelve‐lead ECG was normal during sinus rhythm. The electrophysiological study showed an Atrio‐Hisian (AH) interval of 114 ms and Hisio‐Ventricular (HV) interval of 42 ms during sinus rhythm. Ventricular pacing showed concentric activation of the atrium with nondecremental conduction. Atrial pacing reproducibly induced regular broad and narrow QRS tachycardias.