Significance of the magnitude of a QS wave deflection in evaluating the uninvolved muscle in anterior wall myocardial infarction

The significance of dynamic changes in the QS wave magnitude, as demonstrated in the precordial leads, within the natural evolution of acute anterior wall myocardial infarction (AAMI) was assessed in 25 patients within two weeks of their admission to the intensive cardiac care unit. Two sets of tests, including 12-lead electrocardiogram and a full radionuclear study, were performed in two time periods: (1) within the first 48 hours of admission; and (2) between the 12th and 15th day after admission. Comparison and correlation between the electrocardiographic data, QS waves in leads V₂ and V₃ and in V₁ to V₆ (ΣQV_2-3 and ΣQV_1-6), and radionuclear regional ejection fractions of the noninfarcted posterior muscle (inferior, infero-apical, and posterolateral regions and posterior index) were done. Significant linear correlations were demonstrated between the electrocardiographic variant differences in percentages (ΣQV_2-3 and ΣQV_1-6) and the radionuclear variant differences, especially the posterolateral and the infero-apical regions, as well as the posterior radionuclear index (r between 0.5 and 0.75; p < 0.01). In addition, almost all of the patients who showed deepening of QS waves in the precordial leads also showed an increase in regional ejection fractions in uninvolved myocardium, and vice versa. It is concluded that the dynamic changes in the QS wave magnitude in the precordial leads within the evolution of acute anterior myocardial infarction well reflect the changes of the posterior noninfarcted muscle contraction and therefore offers a simple, inexpensive, and indirect electrocardiographic method for evaluating changes in contraction patterns of noninfarcted myocardium.