Idiopathic Ventricular Arrhythmias Originating From the Pulmonary Sinus Cusp: Prevalence, Electrocardiographic/Electrophysiological Characteristics, and Catheter Ablation.

BACKGROUND Idiopathic ventricular arrhythmias (VAs) originating from the pulmonary sinus cusp (PSC) have not been sufficiently clarified. OBJECTIVES The goal of this study was to investigate the prevalence, electrocardiographic characteristics, mapping, and ablation of idiopathic VAs arising from the PSC. METHODS Data were analyzed from 218 patients undergoing successful endocardial ablation of idiopathic VAs with a left bundle branch block morphology and inferior axis deviation. RESULTS Twenty-four patients had VAs originating from the PSC. In the first 7 patients, initial ablation performed in the right ventricular outflow tract failed to abolish the clinical VAs but produced a small change in the QRS morphology in 3 patients. In all 24 patients, the earliest activation was eventually identified in the PSC, at which a sharp potential was observed preceding the QRS complex onset by 28.2 ± 2.9 ms. The successful ablation site was in the right cusp (RC) in 10 patients (42%), the left cusp (LC) in 8 (33%), and the anterior cusp (AC) in 6 (25%). Electrocardiographic analysis showed that RC-VAs had significantly larger R-wave amplitude in lead I and a smaller aVL/aVR ratio of Q-wave amplitude compared with AC-VAs and LC-VAs, respectively. The R-wave amplitude in inferior leads was smaller in VAs localized in the RC than in the LC but did not differ between VAs from the AC and LC. CONCLUSIONS VAs arising from the PSC are not uncommon, and RC-VAs have unique electrocardiographic characteristics. These VAs can be successfully ablated within the PSC.