Left Bundle Branch Area Pacing Reverts Electromechanical Window Negativity to a Similar Extent as Biventricular Pacing

BACKGROUND: Cardiac resynchronization therapy (CRT) through left bundle branch area pacing (LBBAP) has been associated with reduced arrhythmogenic risk compared to biventricular pacing (BiVP). Electromechanical window (EMW) is a marker of electromechanical instability, and a negative EMW is associated with ventricular arrhythmias. We hypothesized that LBBA-CRT increases EMW at least as much as BiVP-CRT does. METHODS: 129 CRT recipients (LBBAP: n = 63; BiVP: n = 66) were included. EMW and echocardiographic reverse remodeling were evaluated before and 6-12 months after CRT implantation in the entire cohort and in a subgroup of patients with a negative EMW at baseline. EMW is calculated by subtracting the QT interval from the time interval of QRS onset to the aortic valve closure artifact (QAoC) using CW-Doppler echocardiography. RESULTS: EMW measurements were feasible in 67% of patients (n = 86). No significant difference in ΔEMW was observed between LBBAP and BiVP. In patients with a negative EMW at baseline, both CRT strategies led to significant EMW increase (LBBAP: n = 21, ΔEMW +13 ms (IQR -1 to 70), p = 0.003; BiVP: n = 36, ΔEMW +26 ms (IQR -2 to 54), p = 0.006). There was no significant difference between CRT groups (p = 0.779). Left ventricular ejection fraction improved by 10% ± 11% and end-diastolic volume decreased by 37 ± 51 mL (<0.001), with no significant differences between LBBAP and BiVP. In multivariable analysis, a negative EMW at baseline, but not echocardiographic reverse remodeling, was the only independent predictor of EMW increase. CONCLUSION: In CRT patients with a negative EMW at baseline, LBBAP and BiVP revert EMW to a similar degree.