Exploring Mechanical Synchrony and Myocardial Work Across Different Pacing Locations Within the Left Bundle Branch

Left bundle branch pacing (LBBP) enables physiological activation by capturing the left conduction system at various sites. However, whether mechanical synchrony and efficiency vary depending on the pacing location remains unclear.

The study aim was to evaluate whether left ventricular (LV) mechanical performance varies among different LBBP sites and whether paced mechanical synchrony replicates intrinsic LV activation across locations.

This prospective cohort study included 114 patients with preserved LV ejection fraction who received LBBP for bradycardia indications. At follow-up, echocardiographic analysis included strain-derived and myocardial work parameters. In patients with intrinsic rhythm, within-patient comparisons between intrinsic and paced beats were performed.

Central LBB capture (left bundle trunk or septal fascicle pacing) was achieved in 60 patients of 106 patients (56.6%) and peripheral LBB capture (left posterior or left anterior fascicle pacing) in 46 of 106 patients (43.4%). No significant differences in global longitudinal strain or myocardial work indices (global work index, global constructive work, global wasted work, or global work efficiency) were found between central and peripheral LBB captures. Compared with intrinsic rhythm, LBBP did not lead to significant differences in global work efficiency, global work index, global constructive work, or global wasted work, and the echocardiographic changes from intrinsic to paced rhythm were similar between study groups.

In patients with preserved LV ejection fraction, mechanical synchrony and work efficiency were similar across LBB pacing sites. These findings support a pragmatic approach centered on achieving conduction system capture rather than targeting specific anatomical locations.