Central vs peripheral LBB capture: does location matter for mechanical synchrony and myocardial work?

Background

Left bundle branch pacing (LBBP) enables physiological activation, yet whether left-ventricular (LV) mechanical synchrony and efficiency differ across capture locations remains unclear.

Purpose

To compare LV synchrony and myocardial work (MW) between central (trunk or septal fascicle) and peripheral LBB capture (anterior or posterior fascicle), and to assess how paced beats replicate intrinsic LV mechanics among different pacing locations within the LBB

Methods

Single-center prospective cohort of 114 patients with preserved LVEF undergoing LBBP for bradycardia. Follow-up echocardiography quantified strain-derived indices (IVMD, PSD, GLS) and MW (GWI, GCW, GWW, GWE). Within-patient comparisons were performed when intrinsic rhythm was present; adjusted mixed-effects models explored state (paced vs intrinsic), location, and their interaction.

Results

Echocardiography was analyzable in 106 patients; 60 had central capture and 46 peripheral. There were no between-group differences in synchrony (IVMD, PSD, GLS) or myocardial work indices (Figure 1). Specifically, no significant differences were observed in GWE between central and peripheral LBB capture (88.6±4.7% vs 89.0±4.2%, p=0.626), nor in GWI (1578.8±386.8 mmHg% vs 1621.7±437.1 mmHg%, p=0.605). Adjusted analyses using linear mixed models yielded similar results.

In the paired subset (n=56), myocardial work analysis revealed significantly higher GCW (2061.2±369.5 mmHg% vs 1948.6±344.0 mmHg%; p=0.022) and GWW (249.6±129.3 mmHg% vs 207.0±127.9 mmHg%; p=0.021) during LBBP. In contrast, no significant differences were found in GWI (1490.5±379.2 mmHg% vs 1498.6±377.8 mmHg%; p=0.883) or GWE (88.6±4.7% vs 89.3±5.3%; p=0.330). In the adjusted linear mixed models, findings were consistent across capture locations, with no differences in GWI or GWE between paced and intrinsic beats.

The change in echocardiographic parameters from intrinsic to paced rhythm (Δ = paced − intrinsic) was then compared between patients with central and peripheral LBB capture. No statistically significant differences were observed between groups for any of the parameters evaluated (Figure 2). Likewise, ANCOVA models showed no independent association between capture location and Δ values across mechanical synchrony and myocardial work variables.

Conclusion(s)

In patients with preserved LVEF, LV mechanical synchrony and efficiency are similar across central and peripheral LBB capture, and paced activation closely replicates intrinsic mechanics irrespective of location. A pragmatic strategy prioritizing conduction system capture over specific anatomical targeting is supported.Figure 1Figure 2.