Correlation between Electrical Synchrony Index values measured by Synchromax® and left ventricular mechanical dispersion assessed by strain echocardiography

BACKGROUND Left ventricular (LV) mechanical dyssynchrony results from nonuniform myocardial activation, leading to inefficient LV contraction and worse clinical outcomes. Synchromax® is a noninvasive system that performs real-time spatial variance analysis of QRS complexes from a standard electrocardiogram, generating an electrical synchrony index (ESI) that may be a potential marker of LV mechanical dyssynchrony. This study evaluated the efficacy of the ESI in predicting LV mechanical dyssynchrony compared to the gold standard: LV mechanical dispersion (LVMD) > 60 ms as measured by speckle-tracking strain echocardiography. METHODS A cross-sectional study was conducted with consecutive adult patients undergoing echocardiography in San Salvador, El Salvador. Clinical, electrocardiographic (rhythm, QRS duration, ESI), and echocardiographic (LVMD, LV ejection fraction, global longitudinal strain) data were collected. RESULTS Eighty-four studies from 83 patients were analyzed. Mean ESI was 0.36 ± 0.31 and mean LVMD was 58.4 ± 27.1 ms. The ESI showed a sensitivity of 70.0% and a specificity of 88.9%, with negative and positive predictive values of 84.2% and 77.8%, respectively. Agreement with the gold standard was moderate (kappa = 0.60; p < 0.001). ROC curve analysis demonstrated good discriminative performance (area under the curve = 0.81), superior to QRS duration (area under the curve = 0.71) for identifying LV mechanical dyssynchrony. CONCLUSIONS The optimal ESI cutoff was 0.42. ESI correlated consistently and significantly with LVMD, indicating that it may be a more sensitive functional marker than QRS duration, especially in cases without evident dyssynchrony. The ESI is a simple, accessible tool for complementary assessment of ventricular electromechanical synchrony.