LAUSR

BACKGROUND Right-bundle branch block (RBBB) ventricular tachycardia (VT) morphology is a criterion for left ventricular (LV) involvement in arrhythmogenic right ventricular cardiomyopathy (ARVC). OBJECTIVE We sought to determine the frequency and chamber of origin of RBBB VT in patients with ARVC and VT. METHODS We studied 110 consecutive patients with VT who met the diagnostic International Task Force Criteria for ARVC and underwent VT mapping/ablation. Patients with ≥1 RBBB VT were identified. RV origin for the RBBB VT was determined based on standard mapping criteria and elimination with ablation. RESULTS Nineteen patients (17%) had 26 RBBB VTs. Eleven of these 19 patients (58%) had 16 RBBB VTs from the RV and 9 patients (47%) had 10 RBBB VTs originating from the LV with one patient demonstrating both. RBBB VT from RV, most commonly (13/16 RBBB VTs), had an early precordial QRS transition, V2 or V3, with superiorly and typically leftward directed frontal plane axis, consistent with exit from dilated RV adjacent to inferior LV septum, whereas all 10 VTs from LV had RBBB morphology had positive R waves to V5 or V6 and rightward axis in 6 VTs characteristic of basal, lateral origin. CONCLUSIONS In patients with ARVC and VT presenting for VT ablation, RBBB VT occurs in 17% of cases with most RBBB VTs (62%) actually originating from the RV and not indicative of LV origin. The precordial R wave transition and frontal plane axis can be used to identify the anticipated chamber of origin of RBBB VT.