Premonitory syncope is a relatively common form of vascular syncope in young people, which is caused by a decrease in the effective beat volume due to reduced return blood volume and ventricular underfilling in a normal person in an upright tilted position, weakened inhibitory impulses from the arterial sinus and aortic arch pressure receptors to the vasomotor center, and increased sympathetic tone, causing an increased heart rate and maintaining blood pressure at a normal level. Bradycardia and/or lower blood pressure reduces cerebral blood flow and causes syncope. So, how to differentially diagnose syncope prognosis? The following is the differential diagnosis of syncope: 1. Hypertrophic cardiomyopathy (HCM) is a heart disease characterized by asymmetric, uneven hypertrophy of the myocardium and small ventricular chambers, with unknown causes. The onset of the disease is mainly in middle-aged and young people, with a high incidence of familial disease. But in recent years, the incidence of elderly people is gradually increasing. 2, vascular neurological syncope is common in vascular inhibitory syncope, also known as autonomic (vegetative nerve) dysfunction or simple syncope, upright hypotensive syncope, urinary syncope and cough syncope. This disease is mostly seen in young and weak women and is caused by the sudden dilation of extensive small blood vessels. Because of the large number of small blood vessels throughout the body, the sudden dilatation reduces the blood flow back to the heart and reduces the cardiac output accordingly, thus producing neurological ischemia in the brain and causing syncope. Vascular syncope is very common, and it often recurs, especially when under considerable emotional stress, extreme fatigue, pain, panic, or in a crowded, hot room. Because blood vessels in other parts of the body are not innervated by the vagus nerve except for the heart, some scholars have recently suggested that the term neurocardiogenic syncope may be more appropriate.