Computerized orthogonal electrocardiogram: relation of QRS forces to left ventricular ejection fraction

Several studies have suggested a relation between Q wave or R wave amplitude in the standard 12 lead electrocardiogram and the left ventricular ejection fraction. Accordingly, we analyzed the relation between Q wave and R wave amplitudes obtained with computerized orthogonal (Frank) electrocardiography and the angiographically determined left ventricular ejection fraction. A computerized orthogonal electrocardiogram was obtained before cardiac catheterization in 52 consecutive patients being evaluated for chest pain. The electrocardiographic diagnosis indicated 14 normal tracings, 20 inferior, 12 anterior and 6 lateral myocardial infarctions. Linear correlations were made between X, Y and Z axis lead voltages and ejection fraction. A significant correlation was obtained between the voltages of the R waves in the X, Y and Z leads (Rx, Ry, Rz) and of the Q waves in lead Z (Qz) as well as total amplitude Qx + Rx, Qy + Ry and ejection fraction (P <0.01). Arithmetic summation of Rx + Ry + Qz (∑R) significantly augmented the correlation with ejection fraction (r = 0.78, P <0.001); this was only slightly improved by multivariate analysis of Rx, Ry, Qz (r = 0.80, P <0.001) or Rx, Ry, Rz, Qx, Qy, Qz (r = 0.82, P <0.001). ∑R, utilized as a means of predicting whether an ejection fraction was more or less than 50 percent, had an accuracy rate of 92 percent. Thus, ∑R contains important information that can be used practically in the precatheterization evaluation of patients with chest pain and follow-up evaluation of patients with myocardial infarction.