Characteristic changes in acute myocardial infarction with Q-wave myocardial infarction appear on leads facing the transmural myocardial necrotic zone, such as wide and deep Q waves, ST-segment elevation with an arch-back-up pattern, and inverted T waves, often wide and deep, with symmetry in both limbs. The opposite changes occur in leads dorsal to the myocardial infarction zone, namely, increased R waves, ST-segment depression, and upright and increased T waves. In subendocardial in Q-wave-free myocardial infarction, patients with myocardial infarction do not have pathologic Q waves, and ST-segment depression of ≥0.1 mV occurs, but ST-segment elevation in the aVR leads or symmetric T-wave inversion. The ECG is often suggestive of dynamic changes. The localization and scoping of myocardial infarction with Q waves can be determined by the number of leads showing characteristic changes.