Myocardial ischemia is very common in clinical practice, and the following tests are commonly used: 1) electrocardiogram and ambulatory electrocardiogram, which mainly observe whether there is any ischemic ST change on the electrocardiogram, so as to indirectly determine whether there is myocardial ischemia. 2) cardiac ultrasound, which mainly examines whether there is any abnormality in the structure and function of the heart. If the ischemia is more serious, it will cause the contraction of the heart muscle to decrease, and the cardiac ultrasound will indicate the segmental weakness, which is a strong indication of myocardial ischemia. 3.Coronary CT angiography is to directly observe whether the heart blood vessels have narrowing lesions and the degree of narrowing by injecting contrast agent under X-ray, which is the most intuitive and direct test and the gold standard for diagnosing myocardial ischemia.