What is the clinical evidence from this study?

Study design: Cohort. Population: Patients requiring pacing (n=115). Intervention: Left bundle branch pacing (LBBP) vs. Spontaneous rhythm. Primary outcome: Left ventricular mechanical efficiency using myocardial work indices (GWI, GCW, GWW, GWE).

What question did this study set out to answer?

This study aims to compare left ventricular mechanical efficiency during spontaneous rhythm with left bundle branch pacing using myocardial work indices.

June 4, 2026Open Access

Impact of Left Bundle Branch Pacing on Left Ventricular Mechanical Efficiency

Key Result

Left bundle branch pacing preserved LV mechanical efficiency comparable to spontaneous rhythm, with strong correlations for global work index (r=0.685, p<0.001) in the non-LB group.

Key Points

This study aims to compare left ventricular mechanical efficiency during spontaneous rhythm with left bundle branch pacing using myocardial work indices.
Prospective analysis of 115 patients enrolled in the TREEBEARD study (NCT06324682).
Measurement of myocardial work indices before and after left bundle branch pacing.
Classification of patients based on QRS transition during pacing.
Left bundle branch pacing achieved mechanical efficiency like that during spontaneous rhythm.
In the left bundle group, all myocardial work indices showed strong correlations between spontaneous rhythm and LBBP.
In the non-left bundle group, global work index and global constructive work showed strong correlations, while global work efficiency and global wasted work showed moderate to weak correlations.

Study Design

Type

Cohort (n=115)

Structured PICO

Does left bundle branch pacing preserve left ventricular mechanical efficiency compared to spontaneous rhythm?

Population

115 patients enrolled in the prospective TREEBEARD study evaluated for left ventricular mechanical efficiency before and after left bundle branch pacing.

Intervention

Left bundle branch pacing (LBBP)

Comparator

Spontaneous rhythm (baseline before LBBP)

Outcome

Left ventricular mechanical efficiency measured by myocardial work (MW) indices (global work index, global constructive work, global wasted work, and global work efficiency)surrogate

Left bundle branch pacing preserves left ventricular mechanical efficiency comparably to spontaneous rhythm, particularly when direct engagement of the conduction system is achieved.

Abstract

BACKGROUND: Left bundle branch pacing (LBBP) restores physiological ventricular activation, yet its impact on left ventricular (LV) mechanical efficiency remains incompletely understood. OBJECTIVE: To compare LV mechanical efficiency during spontaneous rhythm and LBBP using myocardial work (MW) indices, and to evaluate the influence of QRS transition type. METHODS: In 115 patients enrolled in the prospective TREEBEARD study (NCT06324682), MW indices (i.e., global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE)) were measured before and after LBBP. Patients were classified according to QRS transition during decremental output as Left Bundle (LB) group (nonselective to selective LBB capture) or non-LB group (nonselective capture to LV septal pacing). RESULTS: Overall, LBBP achieved mechanical efficiency comparable to that observed during spontaneous rhythm. In the LB group, all MW indices showed strong correlations between spontaneous rhythm and LBBP. In the non-LB group, GWI (r = 0.685, p < 0.001) and GCW (r = 0.750, p < 0.001) remained strongly correlated, whereas GWE (r = 0.4224, p = 0.01) and GWW (r = 0.395, p = 0.002) showed moderate and weak correlations, respectively. CONCLUSION: Based on our findings, LBBP appears to preserve LV mechanical efficiency to a degree comparable to spontaneous rhythm. Direct engagement of the conduction system, reflected by a nonselective to selective LBBP QRS transition, is associated with greater concordance of MW indices.