LVSP and nsLBBP reduce right ventricular and interventricular dyssynchrony in patient with right bundle branch block

Background Left bundle branch area pacing (LBBAP) primarily ensures early activation of the left ventricle resulting in delayed activation of the right ventricle (RV). It remains unclear whether this RV delay mirrors intrinsic RBBB or whether LBBAP capture types exert a resynchronizing effect on RV activation in patients with RBBB. Aim To determine whether any type of LBBAP have a resynchronizing effect on right-ventricular activation in patients with RBBB Methods This retrospective study included patients from two centres who underwent LBBAP implantation for bradycardia. Ventricular electrical activation was assessed using ultra-high-frequency ECG (UHF-ECG). Right ventricular dyssynchrony (rv-DYS) was calculated as the time difference between the earliest activated segment and latest activation in lead V1 or V2. Interventricular dyssynchrony (inter-DYS) was measured as the activation time difference between leads V7 and V1. Results A total of 55 patients were included in the study (mean age 79 ± 8 years; 80% male; 22 % with heart failure, 22% with coronary artery disease). Both, nsLBBP and LVSP reduced right ventricular dyssynchrony compared to spontaneous RBBB (rv-DYS for nsLBBP: -36 ± 13 ms vs. -64 ± 9 ms, p < 0.001 and for LVSP: -22 ± 18 ms vs. -62 ± 13 ms, p < 0.001) and interventricular dyssynchrony (inter-DYS for nsLBBP: -33 ± 12 ms vs. -61 ± 9 ms, p < 0.001, and for LVSP: -20 ± 20 ms vs. -59 ± 17 ms, p < 0.001). The reduction in both rv-DYS (−16 ± 10 ms vs. −40 ± 17 ms, p < 0.001) and inter-DYS (−15 ± 11 ms vs. −37 ± 16 ms, p < 0.001) was greater during LVSP than during nsLBBP. No difference was found between spontaneous RBBB and sLBBP in rv-DYS (-69 ± 9 ms vs. -66 ± 12 ms, p = 0.42) and inter-DYS (-64 ± 7 ms vs. -60 ± 10 ms, p = 0.15) Conclusion In patients with RBBB, both nsLBBP and LVSP provide RV resynchronization by reducing RV and interventricular dyssynchrony