Initiation and termination of a wide complex tachycardia by an atrial beat

A 28-year-old man with recurrent palpitations and no structural heart disease presented with a documented wide QRS complex tachycardia (WCT). He had a history of slow pathway ablation for atrioventricular nodal reentrant tachycardia three months ago. A standard electrophysiologic study was performed using multipolar-electrode catheters in the high right atrium, His bundle, right ventricular apex, and coronary sinus. The introduction of atrial extra-stimulus from the lateral tricuspid annular region during tachycardia terminated the tachycardia but recurred after one sinus beat (Figure 1).