24-hour cardiac dynamics, also known as dynamic electrocardiogram, can show ST-segment elevation myocardial infarction and old myocardial infarction, but is mainly used for the judgment of the type of arrhythmia, such as, supraventricular tachycardia, atrial fibrillation, atrial flutter and so on. 1. ST-segment elevation myocardial infarction: When this kind of myocardial infarction occurs, the electrocardiogram shows that the ST arch is obviously elevated, and the patient often has severe chest pain, and the pain is persistent. If the patient has this kind of change in dynamic electrocardiogram during chest pain, acute ST-segment elevation myocardial infarction should be considered. 2. Chronic myocardial infarction: dynamic electrocardiogram will show pathological Q waves in ECG leads. Patients usually have shortness of breath or chest tightness. If abnormal ECG changes are found in dynamic ECG examination, it is necessary to consult the doctor in time, and the doctor will determine what the problem is and whether timely treatment is needed.