Ventricular Tachycardia May Masquerade as Supraventricular Tachycardia in Patients With Preexisting Bundle-Branch Block, ,

We present the cases of three patients with preexisting bundle-branch block in whom wide-complex tachycardias were considered to be of supraventricular origin because QRS morphologies were essentially unchanged from those during normal sinus rhythm. The patients experienced adverse effects from medications for supraventricular tachycardia. Ventricular tachycardia eventually was diagnosed in all three by means of invasive electrophysiologic studies. Ventricular tachycardia may masquerade as supraventricular tachycardia in patients with fixed intraventricular conduction disturbance. Emergency therapy based solely on the QRS identity criteria may result in poor clinical outcome.