Insufficient blood supply to the heart often has no obvious precursors, and only a very small number of patients may show atypical symptoms, such as discomfort in the precordial region after activity, chest tightness, panic, and palpitations. Insufficient blood supply to the heart refers to ischemia and hypoxia or necrosis of the heart muscle due to narrowing or blockage of the coronary arteries. It manifests as chest tightness and chest pain. When the coronary artery lumen stenosis is 50-75% and above, quiet fashion can ensure myocardial blood supply through compensatory mechanism. However, when exercise, tachycardia, and emotional excitement cause increased myocardial oxygen demand, it can lead to increased oxygen demand myocardial ischemia, which is the mechanism of most chronic stable angina attacks. The local accumulation of excessive metabolites after myocardial ischemia and hypoxia stimulates cardiac nerves, which travel through the spinal cord and to the brain, producing the sensation of pain. However, most patients do not have particular symptoms until chest tightness and chest pain occur. In some patients with coronary artery disease, although the ECG shows myocardial ischemia, the patient has no clinical symptoms, probably because the lesion is mild or the patient has a high pain threshold and no pain symptoms. Therefore, patients with the presence of high-risk factors for coronary heart disease, such as hypertension, diabetes, and hyperlipidemia, should not be neglected because there is no manifestation of chest tightness and chest pain. They should be monitored by electrocardiogram etc. during daily physical examination.