Fainting is a transient loss of consciousness due to severe cerebral insufficient blood supply. The reason for this occurrence, that is, the underlying disease, may be a problem of brain disease or a problem of heart disease. 1. Brain diseases: If severe cerebral ischemia or even large cerebral infarction occurs, or cerebral hemorrhage occurs, in these cases, the blood circulation of the brain tissue is affected, and severe ischemia or hemorrhage, both of which lead to damage of the brain tissue, and loss of consciousness occurs, i.e., syncope. 2. Heart disease: syncope may occur in patients with myocardial ischemia, cardiomyopathy, heart failure and arrhythmia. (1) Myocardial ischemia: if serious myocardial ischemia occurs, it may affect the blood supply of the sinus node of the heart, affect the cardiac conduction system, and there may be a serious slow heart rhythm or ventricular tachycardia which is a kind of malignant arrhythmia, which affects the heart beat and the blood supply of the brain tissue, and then fainting occurs. (2) cardiomyopathy, heart failure: such patients have a higher risk of malignant arrhythmia, affecting the heart blood flow, affecting the blood supply to brain tissue and syncope. (3) cardiac arrhythmia: for example, pathological sinus node syndrome, ventricular tachycardia, the occurrence of serious cardiac arrhythmia will affect the heart blood, affecting the blood supply to the brain tissue, the occurrence of syncope may. When syncope occurs, it should be treated urgently in the emergency department.