Myocardial ischemia is common in clinical practice, and the following tests are commonly used: 1) electrocardiogram (especially the electrocardiogram during the onset of symptoms) and ambulatory electrocardiogram, which are mainly used to observe the dynamic changes of ischemia on the electrocardiogram, so as to indirectly determine whether there is myocardial ischemia. 2) cardiac ultrasound, which is mainly used to check the structure and function of the heart for abnormalities. If the ischemia is serious, it may cause the contraction of the myocardium to decrease, and the cardiac ultrasound will indicate the segmental weakness, which is the indication of myocardial ischemia. 3.Coronary artery imaging such as coronary CT or coronary angiography is to check whether there are narrowing lesions in the blood vessels of the heart and the degree of narrowing by injecting contrast agent and developing it under X-ray. Among them, coronary angiography is the most visual and direct test, and is the gold standard for diagnosing myocardial ischemia.