The most common symptom of myocardial ischemia is angina pectoris, which is actually a transient manifestation of myocardial ischemia and hypoxia. However, angina is not the only manifestation of myocardial ischemia, because some myocardial ischemia may have no symptoms, or persistent symptoms such as chest tightness, shortness of breath, dyspnea and so on. Angina attacks are mostly related to exertion factors, i.e., they tend to occur at the time of physical activity, and can be quickly relieved by stopping for rest or taking nitroglycerin. The pain may radiate to other parts of the body and last for several minutes or ten minutes, which can be relieved after taking nitroglycerin or resting. Of course, the above are typical angina manifestations, but some angina manifestations are not typical enough to be easily detected. Myocardial ischemia may also be asymptomatic, the patient’s auxiliary examination suggests the existence of myocardial ischemia, but the patient does not feel, this situation is clinically known as asymptomatic myocardial ischemia. Myocardial ischemia can also have some serious symptoms, such as persistent chest tightness, shortness of breath, dyspnea and other manifestations, affecting cardiac function and so on.