Beyond QRS Narrowing: left bundle branch area pacing enhances ventricular synchrony and myocardial work

Background Left bundle branch area pacing (LBBAP) is a physiological alternative to right ventricular (RV) pacing that allows near-normal ventricular activation¹. Combining high-resolution ECG, ventricular dyssynchrony imaging (VDI), and non-invasive myocardial work (MW) analysis provides a comprehensive evaluation of both electrical and mechanical synchrony in paced patients². This pilot study aims to evaluate the feasibility of the use of VDI and MW indexes to characterize the benefits of the LBBAP. Methods Five patients (80% male, 74±7 years) with complete atrioventricular block underwent permanent implant of Cardiac Implantable Electronic Devices (CIEDs) with a RV pacing lead positioned in the left bundle branch area. VDI mapping was performed at baseline and at follow-up in all patients to assess electrical dyssynchrony (QRS duration and interventricular activation delay) and identify those most likely to benefit from LBBAPLeft ventricular mechanical performance was assessed by echocardiographic pressure–strain loop analysis to derive global myocardial work index (GMWI) and efficiency. Results LBBAP significantly shortened QRS duration (from 135 ± 16 ms to 110 ± 10 ms) and markedly reduced electrical dyssynchrony, as assessed by the VDI index whose median [range] varied from 14 [−42; 44] to −19 [−30; −9]. Importantly, this improvement was confirmed at a median follow-up of 64 days, when median VDI dyssynchrony median [range] index was 33 [−35; 80], compared to −17 [−30; −13] with pacing, confirming stable LBBAP capture. In addition, at follow-up three patients demonstrated a significant increase in GMWI from baseline. At follow-up also echocardiographic ejection fraction improved by an absolute value of ≥5%. No complications or threshold rise were observed throughout follow-up. Conclusion In this pilot study a significant association was observed between reduced VDI index and increased ejection fraction, highlighting the physiological benefits of LBBAP. Pre-implant VDI may also assist in selecting patients most likely to benefit from a tailored, physiology-based pacing strategy.