Clinical and electrocardiographic characteristics of idiopathic ventricular arrhythmias with right bundle branch block and superior axis: Comparison of apical crux area and posterior septal left ventricle

Background Right bundle branch block (RBBB) with superior axis electrocardiographic (ECG) morphology is common in patients with idiopathic ventricular arrhythmia (VA) originating from the left posterior fascicle (LPF), from the left ventricular (LV) posterior papillary muscles (PPM), and rarely from the cardiac apical crux. Objective The purpose of this study was to describe the ECG and clinical characteristics of idiopathic VA presenting with RBBB and superior axis. Methods We studied 40 patients who underwent successful catheter ablation of idiopathic VAs originating from the LPF (n = 18), LV PPM (n = 15), and apical crux (n = 7). We investigated clinical and ECG characteristics, including maximum deflection index and QRS morphology in leads aVR and V6. Results Syncope was more frequently seen in apical crux VA compared with other VAs (57% vs 6%, P < .001). Patients with apical crux VA more frequently had an maximum deflection index ≥0.55 compared with LPF VA and PPM VA ( P = .02). A monophasic R wave in aVR and QS or r/S ratio