Prolonged QRS duration (ORS equal to or greater than 170 ms) and left axisdeviation in the presence of left bundle branch block: A marker of poor left ventricular systolic function?

Background Left bundle branch block (LBBB) is commonly associated with stru ctural heart disease and left ventricular dysfunction. We propose that the QRS duration and degree of left-axis deviation (LAD) identify significant l eft ventricular systolic dysfunction in patients with LBBB. Methods In this prospective study the ejection fraction (EF) of 300 consecu tive patients with LBBB was evaluated by echocardiography. The relationship between QRS duration and LAD (axis between -30 degrees and -90 degrees) an d EF were derived. Results There was no significant difference in age, sex, presence of ischem ic or nonischemic cardiomyopathy and valvular heart disease, and EF among t he patients with or without LAD. The EF of patients with QRS greater than o r equal to 170 milliseconds with LAD (n = 20) and without LAD (n = 18) was 25% +/- 16% and 23% +/- 13%, respectively (P = .71). The mean EF (24% +/- 1 0%) of the patients with a QRS duration of greater than or equal to 170 mil liseconds (n = 38) was significantly lower than the mean EF (36% +/- 16%) o f the patients with a QRS duration of < 170 milliseconds (n = 262, P < .015 ). The QRS duration also had a significant (P < .001) inverse correlation w ith EF (R = 0.37, adjusted R-2 = 0.13, SE of estimate = 16.21). However, th e QRS axis was not significantly correlated with EF and did not have added predictive value. Conclusions The QRS duration has a significant inverse relationship with EF and prolongation of QRS duration (greater than or equal to 170 millisecond s) in the presence of LBBB is a marker of significant left ventricular syst olic dysfunction. The presence of LAD in LBBB does not signify a further de crease in EF.