Bradycardia has mainly physiologic and pathological causes such as atrioventricular block, and the main hazards are that it can cause dizziness, fatigue and angina pectoris, heart failure and so on. 1. Causes (1) Physiological: part of sinus bradycardia can be seen in healthy young people, athletes and sleep, hypothermia and so on. (2) Pathological: including the heart itself, such as pathological sinus node syndrome, acute inferior wall myocardial infarction, etc.; intracranial disease, severe hypoxia, hypothyroidism, obstructive jaundice and other systemic diseases. 2. Harm: Pathological bradycardia can cause insufficient blood supply to the heart, brain and other organs, leading to episodes of dizziness, palpitations (rapid heartbeat, often accompanied by panic), decreased exercise endurance and other symptoms. In severe cases, it may cause angina, heart failure, fainting and even sudden death. If you feel unwell, it is recommended that you seek prompt medical attention and treatment.