Global Myocardial Work Efficiency and Left Ventricular Ejection Fraction After Left Bundle Branch Area Pacing Versus Right Ventricular Pacing: Extended Follow-Up of a Prospective Cohort

Background/Objectives: Evidence on myocardial-work indices beyond 12 months after left bundle branch area pacing (LBBAP) remains limited. We compared global myocardial work efficiency (GWE) and the left ventricular ejection fraction (LVEF) after LBBAP and right ventricular mid-septal pacing (RVP). Methods: This prospective, non-randomised cohort included 63 patients with advanced atrioventricular block and preserved pre-implantation LVEF: 34 assigned to an LBBAP strategy and 29 to RVP. Ventricular pacing burden was 100%. GWE was the primary endpoint; LVEF was the principal adjusted secondary endpoint. Analyses adjusted for age, sex, hypertension and atrial fibrillation. Follow-up averaged approximately two years, with an individual range of 0.64–4.23 years. Results: GWE was higher with LBBAP (85.23 ± 6.82% versus 80.00 ± 9.41%; p = 0.016), with an adjusted difference of +4.96 percentage points (95% CI 0.87 to 9.04; p = 0.018). The adjusted LVEF difference was +5.73 percentage points (95% CI 2.77 to 8.68; p < 0.001). Exploratory within-patient LVEF analyses showed mean changes of +1.20 percentage points with LBBAP (95% CI −1.25 to +3.65) and −6.15 with RVP (95% CI −9.16 to −3.14), with an unadjusted between-group difference of +7.35 percentage points (95% CI 3.55 to 11.16; p < 0.001). Conclusions: LBBAP was associated with higher GWE and LVEF at extended follow-up, although some propensity-score GWE confidence intervals included zero. LVEF-change findings are exploratory and do not estimate a common-time trajectory. These observational findings do not establish causality or clinical benefit.