Reentrant ventricular tachycardia originating in the right ventricular outflow tract - Slow conduction identified by right coronary artery ostium pacing

A case of reentrant ventricular tachycardia (VT) originating from the right ventricular outflow tract (RVOT) is described. An electrophysiological study revealed that programmed stimulation from the right ventricle apex induced 2 types of VT with similar left bundle branch block configuration and inferior axis. Yet, VT cycle length (CL) was different; one was stable, sustained VT with a CL of 360 ms and the other was hemodynamically intolerable VT with a CL of 330 ms. Similarly for both VTs, perfect pace mapping was obtained at the anterior septum beneath the pulmonary valve in the RVOT, and exits of both VTs were very close. Entrainment mapping during stable VT was performed and the anterior septum RVOT was designated as the exit for the stable VT. Intriguingly, entrainment pacing from the ostium of the right coronary artery showed that the post-pacing interval was identical to VTCL. The stimulus to QRS interval was very long (340 ms) during entrainment with concealed fusion, and the right coronary artery ostium was therefore consistent with the VT reentry circuit inner loop or the upper portion of the VT reentry circuit exit. These findings suggest that the stable VT reentry circuit had a slow conduction zone from the ostium of the right coronary artery to the exit in the anterior septum RVOT. When radiofrequency catheter ablation was performed at the 2 exits of the anterior septum RVOT, both VTs then could not be induced.