Theoretically, the electrocardiogram cannot return to normal after infarction, and the necrotic type of Q wave will persist. After acute myocardial infarction, the changes of electrocardiogram show a certain evolutionary pattern with the development and recovery of myocardial ischemia, injury and necrosis, which can be divided into hyperacute, acute, subacute and stale phases in terms of time. 1. Hyper-acute stage: It occurs several minutes after the onset of myocardial infarction, which produces high T wave on electrocardiogram, and then ST segment upward slanting or upward elevation of the bow back appears rapidly, which is connected with the high and upright T wave. 2. Acute phase: This phase begins a few hours or days after infarction and lasts for a few weeks. The electrocardiogram shows a dynamic process of evolution, the ST segment is elevated upward in a bow-backed manner, followed by a gradual decline. Necrotic Q-wave, ST-segment elevation of injury type and T-wave inversion of ischemic type can coexist in this phase. 3. Subacute phase: It occurs weeks to months after infarction. The elevated ST segment returns to the baseline, the ischemic T wave inversion gradually becomes shallow, and the necrotic Q wave persists. 4. Stale phase: After a few months, the ST segment and T wave return to normal or the T wave continues to be inverted and flattened and tends to be constant. Theoretically, necrotic Q waves will persist. Detailed prognosis of infarction and ECG changes are recommended to consult a specialist for guidance.