Reassessment of the relation between QRS forces of the orthogonal electrocardiogram and left ventricular ejection fraction.

Previous studies have demonstrated the existence of a strong positive correlation between the amplitude of QRS forces of the orthogonal electrocardiogram and the angiographically determined left ventricular ejection fraction. In a large group of patients evaluated for chest pain, we examined the relationship between the arithmetic summation of RX + RY + QZ (sigma R), the maximal and mean spatial QRS vectors and the ejection fraction (EF). In a total of 252 patients, there was a statistically significant correlation between sigma R and EF but a low correlation coefficient value (r:0.22, P less than 0.001). This relationship was essentially due to the group of patients with coronary artery disease and myocardial infarction (r:0.24, P less than 0.015) whereas there was no correlation in the group of normal subjects or in patients with coronary artery disease without myocardial infarction. In the group with myocardial infarction, a significant correlation between sigma R and EF existed only in patients with anterior myocardial infarction (r:0.41, P less than 0.025). In conclusion, both ejection fraction and amplitude of QRS forces decrease in coronary artery disease especially when an anterior myocardial infarction is present. However, despite the positive association between these angiographic and electrocardiographic indices, the low value of the correlation coefficient indicates that it is not possible to predict ejection fraction from the value of sigma R in individual patients.