Idiopathic Right Ventricular Outflow Tract Tachycardia: Which Substrate, Mechanism and Therapy?

Abstract

Ventricular tachycardias (VT) may occur in patients who have no clear evidence of organic heart disease. So-called idiopathic VT accounts for 12%–17% of all cases of VT [1, 2]. In approximately 70%–80% of cases idiopathic VT originates from the right ventricular outflow tract (RVOT) and the ECG aspect is characterized by left bundle branch block (LBBB) and inferior axis (IA) morphology [2, 3]. Idiopathic RVOT-VT presents two main clinical forms: (1) repetitive monomorphic VT, and (2) paroxysmal stress-mediated sustained VT. The first arrhythmic pattern includes repetitive ectopies and paroxysms of nonsustained VT with the same morphology, the second is typically characterized by episodes of VT induced by stress, exercise or catecholamine infusion. Some patients can have either form of RVOT-VT, and during exercise stress testing they show initial suppression of nonsustained VT, final induction of sustained VT or relapse of the arrhythmia immediately after the peak exercise. Finally, a third form of the RVOT arrhythmic syndrome includes frequent and/or repetitive monomorphic (LBBBIA) ventricular premature beats without sustained VT episodes.