Idiopathic ventricular arrhythmia originating from the para-Hisian area: Prevalence, electrocardiographic and electrophysiological characteristics

Background: We investigated the prevalence and the electrocardiographic and electrophysiological characteristics of ventricular arrhythmias (VAs) originating from the para-Hisian area. Methods: Among 250 patients with idiopathic VAs, 8 (3.2%) had an ablation site in the para-Hisian region. For comparison with right ventricular (RV) para-Hisian VAs (n=6), 27 patients with VAs originating from the posterior RV outflow tract (RVOT) were studied. Results: Para-Hisian VAs had an R wave in leads I and aVL. The VAs originating from the site below the His bundle region were determined to have a superior axis (n=4, 50%). A His potential was recorded at the proximal bipole of the successful ablation site in 6 patients. RV para-Hisian VAs had a narrower QRS width (114±12 ms vs. 139±12 ms, P=0.003), as well as a higher incidence of R waves in lead aVL (83.3% vs. 0%, P<0.001) and QS waves in lead V₁ (83.3% vs. 22.2%, P=0.004) compared to posterior RVOT VAs. A greater R wave amplitude in lead I (1.15±0.34 mV vs. 0.34±0.18 mV, P=0.001) and a smaller R wave amplitude in the inferior leads (0.68±0.23 mV vs. 1.58±0.55 mV, P<0.001), with a higher R wave amplitude ratio in leads II/III (4.2±2.0 vs. 1.1±0.2, P=0.01) were the major ECG characteristics. Conclusions: Para-Hisian VAs have distinctive electrocardiographic features and can be successfully eliminated without disturbance of atrioventricular conduction.