There are two diagnostic criteria for sinus bradycardia on an ambulatory electrocardiogram, the first is transient bradycardia, which indicates that the heart rate is less than 60 beats per minute at a given time period, and the other is persistent bradycardia, which is diagnosed by a total number of heart beats of less than 80,000 beats in a 24-hour period. Before diagnosing sinus bradycardia, one should first know what a normal heart rhythm is. A normal heart rhythm is emitted from the sinus node, passed to the atria through the inter-nodal bundle, and then to the ventricles through the AV node, and the normal heart rate is between 60 and 100 beats per minute, and when the heart rate is less than 60 beats per minute, it is called sinus bradycardia. Sinus bradycardia is physiologic and pathologic, physiologic in athletes and pathologic in cardiomyopathy and myocarditis. Sinus bradycardia needs to be treated under the guidance of a doctor, and should not be used privately.