In summary, the electrocardiogram is limited in its ability to detect a myocardial infarction. Its sensitivity is compromised seriously by a substantial number of patients (table; see text) with non-Q wave infarction or regression of Q waves. Once a Q wave occurs, the predictive accuracy of those changes, in delineating the location of the infarction, is quite high. The ability of Q waves or ST segment elevation to predict or identify the "culprit artery" is less strong, primarily due to the variation in coronary anatomy commonly found. The relationship between anterior or inferior lead changes and anterior or inferior myocardial damage is close. However, lateral lead changes may more accurately represent anterolateral (I, AVL) or apical (V5-V6) infarction. Tall R waves in anterior precordial leads is most often associated with posterolateral infarction.