Understanding electromechanics of left bundle branch area pacing: Association between electrical synchrony,...

During left bundle branch area pacing (LBBAP), several markers of electrical synchrony, (V6 R wave peak time [RWPT], aVL-RWPT, and the V6-V1 interpeak interval), are commonly used to assess LBB capture. Nevertheless, the relationship between these electrocardiographic (ECG) measurements and mechanical synchrony remains poorly understood.

We aimed to analyze the association between electrical parameters from the paced QRS (p-QRS) complex and mechanical performance assessed through 2-dimensional (2D) strain and myocardial work (MW) indices, following LBBAP implantation.

This prospective cohort study included 149 patients who underwent successful LBBAP implantation for bradycardia pacing. The association between paced ECG measurements, mechanical synchrony, and MW parameters was assessed using linear regression analysis.

A shorter paced V6-RWPT was associated to higher interventricular mechanical delay (IVMD) (β = -0.146; P = .096) and lower global wasted work (GWW) (β = 0.168; P = .057). Paced V1-RWPT was associated with greater GWW (β = 0.205; P = .048) and higher IVMD (β = 0.203; P = .046), as was the V6-V1 interpeak interval (β = 0.259; P = .009 for IVMD). Paced aVL-RWPT showed a strong relationship with mechanical synchrony and several MW indices, with longer values significantly related to increased peak strain dispersion (PSD) (β = 0.184; P = .050), global constructive work (GCW) (β = 0.263; P = .005), GWW (β = 0.253; P = .006) and decreased global work efficiency (GWE) (β = -0.205; P = .028). Additionally, longer p-QRS duration was associated with increased IVMD and GWW. Subgroup analyses revealed differences based on capture type.

Electrical p-QRS complex parameters in LBBAP were linked to mechanical synchrony and MW, emphasizing the importance of the QRS characteristics.