Sinus bradycardia is a common sinus arrhythmia, which refers to a sinus rhythm slower than 60 beats per minute. It can be seen in healthy young people, well-trained athletes, people who are always engaged in physical work, and healthy people during sleep; it can also be associated with a number of disorders, such as organic sinus node hypofunction (pathological sinus node syndrome), various disease states that cause vagal excitation, such as increased intracranial pressure, uremia, glaucoma, inferior wall myocardial infarction, hepatobiliary and other gastrointestinal diseases, and the effects of certain drugs. The effects of certain drugs, etc. The cause of sinus bradycardia 1, the vagus nerve tone increased due to the vagus nerve tone, can appear sinus bradycardia, the heart rate can be about 50 times / min, generally not less than 40 times / min. athletes at night individual can be as low as 38 times / min or so. Physical workers also often have sinus bradycardia. 2, drugs caused by some drugs can make the vagus nerve excitability increased or directly inhibit the sinus node function and cause sinus bradycardia. 3.Impaired sinus node function refers to sinus bradycardia caused by damage to the sinus node (such as inflammation, ischemia, poisoning or degenerative damage, etc.). In addition, it can be seen in myocardial damage such as myocarditis, pericarditis, endocarditis, cardiomyopathy, myocardial infarction, myocardial sclerosis, etc. It may also be caused by transient sinus node inflammation, ischemia and toxic damage. 4.Acute myocardial infarction The incidence of sinus bradycardia is 20% to 40%, with the highest incidence in the early onset of acute myocardial infarction (especially inferior wall infarction). Prevention and treatment of sinus bradycardia Effective treatment and prevention can be achieved only if the cause is found. It is necessary to find the true cause and to distinguish between physiological and pathological sinus bradycardia, which requires an ambulatory electrocardiogram. Because most sinus bradycardia is not clinically important and does not need to be treated. In China, due to economic, previous practice of the doctor in charge, patient’s willingness to accept or other medical circumstances, patients with symptomatic bradycardia are often preferred to try certain drugs and then consider pacemaker implantation if the results are unsatisfactory, including cholinergic receptor blockers (e.g. atropine), β2 agonists (e.g. salbutamol, terbutaline), β1 and β2 agonists (isoproterenol) and theophylline. epinephrine) and theophylline drugs, etc. Side effects of antiarrhythmic drugs It is worth noting that antiarrhythmic drugs have certain side effects, such as urinary retention, dry mouth, and increased eye pressure due to atropine, and increased blood pressure, ventricular arrhythmia, and angina pectoris due to catecholamines, etc. Many patients do find that palpitations, chest tightness, and other discomfort occur after use and discontinue the drugs. Albuterol can also have side effects such as hypokalemia and elevated blood glucose, which need to be monitored constantly during the course of use. Moreover, the efficacy of these drugs on slow arrhythmias is not satisfactory. A large number of clinical data show that in most patients with slow heart rate, after using these drugs, the original arrhythmia is corrected within a short period of time, but new arrhythmia is induced again. Therefore, for slow arrhythmias with clinical symptoms, various guidelines recommend cardiac pacing if the cause cannot be removed. The efficacy of anti-slow arrhythmia drugs is questionable and is not clearly recommended by guidelines or expert consensus.