Although symptoms of myocardial ischemia are often present in coronary artery stenosis >70%, the severity of symptoms sometimes does not exactly parallel the degree of coronary artery stenosis. This is due to the fact that the symptoms of myocardial ischemia are influenced by a combination of factors: the number and size of the branches of the diseased coronary artery, the extent of blood supply and the degree of stenosis, the development of collateral circulation and the patient’s perception of pain, among which the degree of stenosis is only one factor determining the severity of ischemic symptoms. In recent years, it has been found that the stability of local plaque in diseased coronary arteries is an important factor in determining the clinical performance and prognosis of patients with coronary heart disease. Unstable plaques are not necessarily large in size, and the degree of luminal stenosis itself is not necessarily severe (often <50%), but after rupture, thrombosis can occur, resulting in rapid narrowing of the lumen within a short period of time or even complete occlusion, and the clinical manifestations of acute coronary syndrome including unstable angina and acute myocardial infarction can occur. Therefore, the lumen shown by coronary angiography performed at a certain time does not represent the development, regression and rate of change of the coronary artery lesion causing myocardial ischemia in the future period. Therefore, those who have clinical symptoms but have mild to moderate coronary stenosis on coronary angiography are recommended to review coronary angiography at certain intervals in order to keep abreast of lesion changes.