Electrocardiographic characteristics of left bundle branch block and its capacity to predict decreased left ventricular ejection fraction

Abstract

Complete left bundle branch block is an uncommon abnormality that has been associated with adverse cardiovascular outcomes and structural abnormalities in the cardiac chambers. Some electrocardiographic criteria have been associated independently with reduced left ventricle ejection fraction. Nevertheless, it is uncertain if the signs of left ventricular hypertrophy, left atrial enlargement, left axis deviation, QRS duration, and Strauss criteria can predict reduced left ventricle ejection fraction. Objective: To evaluate the capacity of Strauss criteria, left ventricular hypertrophy, left atrial enlargement, QRS duration, and left axis deviation to predict reduced left ventricle ejection fraction. Methods: An observational, descriptive, cross-sectional study was conducted, that included adults with complete left bundle branch block diagnosed by traditional criteria, in whom left ventricular ejection fraction was evaluated with transthoracic echocardiography. Univariate, bivariate and multivariate analysis were done and the Oliveira score was validated. Additionally, prediction models as logistic regression were applied and operative characteristics of the electrocardiographic signs were determined. Results: There were 133 patients included in the analysis, 46 of them (34.5%) showed reduced left ventricle ejection fraction. In bivariate analysis, Cornell index, left atrial enlargement and Strauss criteria showed the highest sensitivity (80, 78 and 76% respectively), and Sokolow index showed the highest specificity (95%). In regression models, that included electrocardiographic and clinical variables, it was found that the variables that best predict reduced left ventricle ejection fraction were QRS amplitude, left axis deviation, hypertension, age and functional class according to NYHA scale. Conclusions: The prediction capacity of electrocardiographic and clinical variables in this study is modest, just as the Oliveira score with cutoff points for reduced left ventricle ejection fraction of 40 and 45%, respectively.