Electrocardiographic Characteristics and Ablation Outcomes Associated With Para-Hisian Ventricular Arrhythmias

Background: Ventricular arrhythmias (VAs) near the His-bundle comprise 9% of unexplained VAs and present challenges for ablation caused by the risk of atrioventricular block. Objectives: The authors studied the electrocardiographic (ECG) and electrophysiological characteristics of Para-Hisian (PH) VAs, comparing them with septal right ventricular outflow tract VAs. Methods: From 210 patients with VAs between 2018 and 2024, 31 (14.7%) with PH-VAs and 23 (10.9%) with septal right ventricular outflow tract VAs were included. ECG characteristics of both were compared, and features differentiating left and right PH and supra- and infra-Hisian VAs were identified. Results: Of 31 patients, 15 had VAs from the right PH site and 16 from the left. Median follow-up was 15 months (Q1-Q3: 14-21 months) for left infra-Hisian, 16 months (Q1-Q3: 14-20 months) for left supra-Hisian, and 14 months (Q1-Q3: 14-16 months) for right infra-Hisian and right supra-Hisian VAs (Q1-Q3: 14-15 months). PH-VAs had narrower QRS complexes (134 ± 19.6 ms vs 169 ± 24 ms; P < 0.05), R-wave in lead aVL (100% [31 of 31] vs 4.3% [1 of 23]; P < 0.001), and earlier R-wave transition at or before lead V₃ (80.6% [25 of 31] vs 47.8% [11 of 23]; P < 0.05). Left PH-VAs had earlier R-wave transition at lead V₂ (50% [8 of 16] vs 20% [3 of 15]; P = 0.036). Right PH VAs had deeper S-wave relative to the preceding sinus beat in lead V₁ (73.3% [11 of 15] vs 37.5% [6 of 16]; P = 0.04) and lead aVR (80% [12 of 15] vs 56.3% [9 of 16]; P = 0.01). Postprocedure heart block occurred in 1 patient. Conclusions: PH-VAs exhibit unique ECG features based on their origins, and can be effectively treated without affecting atrioventricular conduction.