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 <0.15 in V5 (P <.001) could distinguish apical crux VA from other VAs with high accuracy. All patients with VA underwent attempted ablation in the endocardium (success rate: LPF 89%, PPM 80%, crux 14%). Only 1 of 7 patients with apical crux VA had acute success with ablation in the middle cardiac vein. In 2 of apical crux patients, epicardial ablation using subxiphoid approach was performed successfully. CONCLUSION We could distinguish LPF VA, PPM VA, and apical crux VA using a combination of clinical and ECG characteristics. These findings might be useful for counseling patients and planning an ablation strategy.