Prediction of Left Ventricular Dysfunction on the Basis of Ventricular Depolarization Time and Electrical Axis in Patients with Left Bundle Branch Block

Background- Prolongation of ventricular depolarization time (QRS duration), particularly in left bundle branch block (LBBB), is commonly associated with many cardiac diseases. We posit that the QRS duration and degree of left-axis deviation (LAD) identify significant left ventricular (LV) systolic dysfunction in patients with LBBB. Methods- In this prospective study, 150 patients with diagnosis of LBBB were divided into two groups (QRS≥160 and QRS<160 milliseconds). Then the relationships between QRS duration, left axis deviation (LAD: axis between –30 ° and –90°), and echocardiographic LV ejection fraction (EF) were derived by t-test, chi-square, and linear regression analysis in a step-wise method. Results- There was no significant difference in age and sex among the patients with or without LAD and QRS duration less or more than 160 ms (p>0.05). The EF of patients with LAD (n=64) and without LAD (n=86) was 48.64±14.63 % and 52.10±13.98%, respectively (p=0.143). The mean±SD EF (54.5±10.54%) of the patients with a QRS duration of ≥160 milliseconds (n=19) was significantly more than the mean ± SD EF (23.89±5.46%) of the patients with a QRS duration of <160 milliseconds (n=131, p<0.001). The QRS duration also had a significant (p<0.001) inverse correlation with EF (R = 0.926, adjusted R2 = 0.857, SE of estimate = 5.42). However, the QRS axis was not significantly correlated with EF and did not have added predictive values. Conclusion- The QRS duration has a significant inverse relationship with EF. Furthermore, the prolongation of QRS duration (≥160 milliseconds) in the presence of LBBB is a marker of significant left ventricular systolic dysfunction. The presence of LAD in LBBB does not signify a further decrease in EF (Iranian Heart Journal 2006; 7 (4):17-25)