Sinus bradycardia is diagnosed when the body’s heart is paced by the sinus node and the heart rate is less than 60 beats per minute. The causes of sinus bradycardia are: 1, vagus nerve excitation, vagus nerve excitation can directly inhibit the frequency of sinus node excitation, resulting in slow heart rate. 2, sinus node function is impaired: inflammation, ischemia, degenerative changes can lead to the sinus node is damaged, resulting in the sinus node automatic depolarization ability is weakened, the emergence of sinus bradycardia. Short-term damage to the sinus node can be recovered, so the patient will only have a transient sinus bradycardia.3., acute myocardial infarction is the site of the lower wall infarction, so the early onset of sinus bradycardia is about 20%-40%.4. Extracardiac factors, such as vagal hyperactivity, deep breathing, the application of β-blockers, and so on. When sinus bradycardia occurs, patients may have symptoms of insufficient blood supply to the heart, brain, kidneys and other vital organs. Patients with mild symptoms show weakness, dizziness, poor memory, etc. In severe cases, patients may experience blackout, syncope, angina, oliguria, etc.