Early diagnosis of impaired left ventricle systolic function significantly improves prognostic results of this group of patients. Electrocardiogram (ECG) remains the simplest and most common test to direct therapeutic decisions in cardiology patients. The aim of this analysis is to assess the relationship between reduced left ventricular ejection fraction (LVEF) and parameters of lead aVR in standard ECG. Methods: The authors evaluated 157 consecutive patients with normal LVEF (≥50%) and reduced LVEF (<50%) who underwent a standard 12‑lead ECG to assess the amplitude of lead aVR. Results: There was a significant correlation between the LVEF and the amplitude of lead aVR (QRSaVR). In the analysis of the ROC curve for 5.5 mm cut‑off, sensitivity of this parameter to identify the reduced LVEF was 50.9%, and specificity – 93%. Conclusions: Amplitude in lead aVR calculated from standard ECG correlate with LVEF calculated by echocardiography.