Sinus rhythm is written on the ECG to indicate that the origin of the electrophysiologic activity of the heart is normal for that subject, but it is not a complete guarantee of a normal rhythm. Normal electrocardiographic activity of the human heart begins in the sinus node, excites the atria, conducts to the AV node via the interjunctional bundle, and then follows the sequence of conduction from the Hirschsprung’s bundle → the left and right bundle branches → the Purkinje fibers, and finally excites the ventricles. This sequential propagation of electrical excitation can cause a series of potential changes, forming the corresponding band on the electrocardiogram. Therefore, the normal heart rhythm should be sinus rhythm. However, sinus rhythm does not guarantee a normal rhythm, such as pathological sinus node syndrome. Sinus rhythm only determines the origin of the impulse of the cardiac electrical activity and the conduction in the atria is normal, it is recommended to combine the heart rate, rhythm, ECG waveforms and the patient’s symptoms, signs and symptoms, etc., to carry out a comprehensive analysis and judgment.