Figure legends
Figure 1 12-lead ECG and intracardiac electrogram showed normal P-R/H-V interval during sinus rhythm and constant H-V during atrial extrastimulus. CS=coronary sinus; ECG=electrocardiogram; RV=right ventricle.
Figure 2 A: A sensed atrial extrastimulus delivered from CS5-6 during the wide QRS tachycardia, advanced the subsequent ventricular activation and reset the tachycardia, with unchanged QRS configuration. B: Termination of the tachycardia with an atrial signal. The 3 sinus beats after tachycardia showed prominent delta wave during isoproterenol infusion. See text for discussion. CS=coronary sinus; RV=right ventricle.
Supplementary Figure 1 An early-coupled atrial extrastimulus encountered the anterograde refractory period of the accessory pathway and terminated the tachycardia. See text for discussion. CS=coronary sinus; RV=right ventricle.