Abstract BACKGROUND: Heart failure (HF) due to left ventricular (LV) systolic dysfunction has lesser survival than diastolic HF .We examined the correlation of two new angles(a and b) of QRS complex in the electrocardiogram (ECG) with indices including left ventricular ejection fraction (LVEF),left ventricular end systolic dimension (LVESD) and left ventricular end diastolic dimension (LVEDD) for predicting LVEF. METHODS: In this cross–sectional study,159 subjects with clinical signs of LV systolic dysfunction who presented to the Al-Zahra hospital in Isfahan, Iran , underwent echocardiography .First ,on the ECG ,two new angles defined and then these two angles compared manually and with computerized analysis by two different observers blinded to the another data. After confirmation of excellent correlation between these two forms, then two angles measured manually with protractor in 159 patients (wide QRS complex in 59 and normal in 100 patients). Then, correlation between these angles and echocardiographic indices were assessed. RESULTS: Statistical analysis revealed that in normal QRS complex, there was no correlation between any of two angles and echocardiographic indices. In contrast, in wide QRS complex,b angle and b/a ratio was correlated with any three echocardiographic indices (negative correlation with LVEF and positive correlation with LVESD and LVEDD) i.e. with decrease in LVEF and increase in LVESD and LVEDD, b angle is widened and b/a ratio increases. A LVEF of 30% corresponded to b/a ratio of 2 in wide QRS complex patients on the regression line. Linear regression analysis generated the regression line equation for predicting the LVEF. The equation is LVEF = 60.6 – (14.5 ´b/a ratio). CONCLUSION: b angle and b/a ratio can predict LVEF in patients with suspected HF and wide QRS complex. Keywords: Left ventricular systolic dysfunction, QRS angle, Electrocardiogram, ejection fraction.