Two Arrhythmias, One Diagnosis, All from Surface ECGs

A 48-year-old male with known supraventricular tachycardia presented with wide complex tachycardia and he was cardioverted. The patient was initially diagnosed with both ventricular tachycardia and supraventricular tachycardia. After reviewing electrocardiograms, a correct diagnosis of orthodromic atrioventricular reciprocating tachycardia with left-sided accessory pathway was made which was confirmed and successfully ablated in subsequent electrophysiological study. Not all wide complex tachycardias are ventricular tachycardia. If the rate of narrow complex supraventricular tachycardia becomes slower with the development of a bundle branch block, it is diagnostic for the presence and participation of the ipsilateral accessory pathway, which is called Coumel’s law