There are many people who look healthy on a regular basis, with no history of heart disease or symptoms such as palpitations or chest pain, but are found to have significant signs of myocardial ischemia on their ECG during a health checkup. Usually patients with myocardial ischemia are accompanied by symptoms of chest tightness and chest pain. There are also many patients with myocardial ischemia, whose ECG shows myocardial ischemia but the patient does not have symptoms such as chest tightness, chest pain, shortness of breath, etc. This is the medical term “occult coronary artery disease”, also called “asymptomatic myocardial ischemia”. Most patients with asymptomatic myocardial ischemia have predisposing factors for coronary artery disease, such as hypertension, hyperlipidemia, diabetes and smoking. Therefore, even asymptomatic myocardial ischemia should be treated with lipid-lowering drugs, beta-blockers, nitrates and calcium channel blockers. Through early application of drugs, angina pectoris and myocardial infarction can be prevented and treated. Coronary heart disease without chest pain symptoms is usually seen in the elderly or diabetic patients. When myocardial infarction occurs in the elderly and diabetic patients, they may not have chest pain but show symptoms such as pallor, drop in blood pressure and shock. Why do middle-aged people, who are neither elderly nor diabetic, not necessarily show symptoms when they have coronary heart disease? Research has linked this to long-term, heavy smoking. Scientists in the United States conducted a group study of long-term heavy smokers and nonsmokers, placing a metal probe on a human limb and gradually heating it up until the subject could not tolerate it. The investigation showed that after each cigarette, the pain threshold for high temperatures increased, while the pain threshold of nonsmokers did not change. Studies have shown that nicotine affects the nerves and reduces sensitivity to pain, masking the truth about the coronary condition. Asymptomatic patients with coronary artery disease can develop angina pectoris or even sudden death coronary artery disease, so it is important not to be paralyzed. Patients should pay attention to self-care, must quit smoking, and receive regular treatment. If the patient has objective manifestations of myocardial ischemia, i.e. ECG, radionuclide myocardial imaging or echocardiography shows that the heart has been affected by insufficient coronary artery blood supply, it can be considered as early coronary heart disease. This should be treated and prevented as early as possible.