The main causes of bradycardia include the following: 1. Physiological bradycardia, which occurs in normal individuals such as athletes and some elderly people, mainly due to increased vagal tone; 2. Cardiac diseases, such as sick sinus syndrome, severe atrioventricular block, myocarditis, and acute inferior myocardial infarction; 3. Other diseases, such as hypothyroidism and hyperkalemia. Physiological bradycardia generally poses no harm and does not require intervention. Pathological bradycardia, when the heart rate significantly slows down, can lead to a decrease in cardiac output, causing insufficient blood supply to the brain, resulting in symptoms such as dizziness, visual obscurity, and fainting. It can also cause coronary artery supply insufficiency leading to angina, as well as symptoms of fatigue and reduced exercise tolerance, requiring timely treatment.