Left bundle branch pacing better preserves ventricular mechanical synchrony than right ventricular pacing: a two-centre study

AIMS: Left bundle branch pacing (LBBP) has been shown to better maintain electrical synchrony compared with right ventricular pacing (RVP), but little is known about its impact on mechanical synchrony. This study investigates whether LBBP better preserves left ventricular (LV) mechanical synchronicity and function compared with RVP. METHODS AND RESULTS: Sixty patients with pacing indication for bradycardia were included: LBBP (n = 31) and RVP (n = 29). Echocardiography was performed before and shortly after pacemaker implantation and at 1-year follow-up. The lateral wall-septal wall (LW-SW) work difference was used as a measure of mechanical dyssynchrony. Septal flash, apical rocking, and septal strain patterns were also assessed. At baseline, LW-SW work difference was small and similar in two groups. SW was markedly decreased, while LW work remained mostly unchanged in RVP, resulting in a larger LW-SW work difference compared with LBBP (1253 ± 687 mmHg·% vs. 439 ± 408 mmHg·%, P < 0.01) at last follow-up. In addition, RVP more often induced septal flash or apical rocking and resulted in more advanced strain patterns compared with LBBP. At 1 year follow-up, LV ejection fraction (EF) and global longitudinal strain (GLS) were more decreased in RVP compared with LBBP (ΔLVEF: -7.4 ± 7.0% vs. 0.3 ± 4.1%; ΔLVGLS: -4.8 ± 4.0% vs. -1.4 ± 2.5%, both P < 0.01). In addition, ΔLW-SW work difference was independently correlated with LV adverse remodelling (r = 0.42, P < 0.01) and LV dysfunction (ΔLVEF: r = -0.61, P < 0.01 and ΔLVGLS: r = -0.38, P = 0.02). CONCLUSION: LBBP causes less LV mechanical dyssynchrony than RVP as it preserves a more physiologic electrical conduction. As a consequence, LBBP appears to preserve LV function better than RVP.