Catheter ablation of ventricular arrhythmias arising from the right ventricular septum close to the His bundle: features of the local electrogram at the optimal ablation site.

INTRODUCTION: The characteristics of the local electrogram at the optimal ablation site of ventricular arrhythmias (VAs) originating from the right ventricle close to the His bundle (HB) region have rarely been described.

METHODS AND RESULTS: Among 190 consecutive patients with idiopathic VAs with left bundle branch block morphology and inferior-axis deviation, 16 were found to have successful ablation site in the right ventricle close to the HB region (para-Hisian group). The electrophysiologic data were compared between the patients in the para-Hisian group and those with VAs arising from the right ventricular (RV) outflow tract (RVOT group). The distal bipolar electrogram at the successful ablation sites in the para-Hisian group exhibited a significantly greater R-wave duration, lower R-wave amplitude, and slower upright deflection of the initial R wave than did those in the RVOT group (all P < 0.001). In the para-Hisian group, a total of 56 radiofrequency (RF) energy applications were delivered, of which the local electrograms at 16 successful and 40 unsuccessful ablation sites were reviewed. High-frequency R-wave potentials of the bipolar electrogram were present in 14 (88%) of the successful ablation sites. An R-wave duration of greater than 34 ms had a discriminatory power for indicating the site of a successful ablation (area under the receiver-operator characteristics curve 0.90, sensitivity 94%, specificity 80%).

CONCLUSIONS: The successful ablation site of the para-Hisian VAs had distinctive local electrogram characteristics. A longer R-wave duration of the bipolar electrogram with high-frequency potentials could be a novel predictor of a successful ablation.