Left bundle branch area pacing vs right ventricular pacing for atrioventricular block: the MELOS RELOADED study.

BACKGROUND AND AIMS Left bundle branch area pacing (LBBAP) promotes physiological synchronous activation of the left ventricle and may be particularly beneficial in patients with atrioventricular block (AVB), but its mortality benefit remains unclear. This study aims to compare long-term survival in AVB patients receiving either LBBAP or right ventricular pacing (RVP) and to analyse predictors of mortality during LBBAP. METHODS MELOS RELOADED, a multicentre European collaboration, was a registry-based study of pacemaker patients with AVB, left ventricular ejection fraction (LVEF) >40% and ventricular pacing >20%. The primary outcome was all-cause mortality based on national registries. A 1:1 propensity score matching was performed between the RVP and LBBAP groups. Kaplan-Meier curves and multivariable Cox proportional hazards models were used to estimate survival. RESULTS In total, 3382 patients receiving LBBAP or RVP were matched. At 4-year follow-up, the Kaplan-Meier curve showed an absolute difference in survival of 11.8% in favour of LBBAP (P < .001). LBBAP was a robust predictor of reduced mortality with a hazard ratio (HR) of 0.53 (95% confidence interval 0.42-0.65, P < .001). Within the LBBAP group, the following independent predictors of increased mortality were identified: lack of confirmed left bundle branch capture (HR 1.85, P < .001), lower percentage of ventricular pacing (HR 1.12), and age. CONCLUSIONS This is the first large study demonstrating the long-term survival benefit of LBBAP. This strengthens the use of LBBAP in AVB patients with preserved/mildly reduced LVEF while awaiting the results of randomized trials. Confirmation of left bundle branch capture seems advisable to achieve optimal results with LBBAP.