Syncope is a clinical syndrome, also known as fainting. This syndrome is caused by a sudden decrease in total cerebral blood flow, a temporary lack of blood or oxygen supply to the brain, which inhibits the function of the reticular structure and causes loss of consciousness; it lasts from seconds to minutes; during the attack, the patient cannot maintain posture tension, so he cannot stand and faints, but recovers quickly. The causes of the sudden decrease in cerebral blood flow include: a sharp drop in blood pressure; a sudden decrease in cardiac output; acute and widespread blood supply insufficiency in the cerebral arteries. The above three abnormalities are caused by a variety of different factors, which can be interconnected. Syncope in some patients is multifactorial.