The heart rhythm that is paced by the sinus node, the pacing point of the normal heart, is known as sinus rhythm, and sinus rhythm is a normal heart rhythm. Sinus rhythm is a heart rhythm paced by the sinus node, the normal pacing point of the heart, which is a normal heart rhythm with a heart rate of 60 to 100 beats per minute. The pacing of the heart relies on the conduction of electrical activity. The conduction system within the heart includes the sinus node, inter-nodal bundle, atrioventricular node, Hitchcock’s bundle, right and left bundle branches and Purkinje fiber network. The sinus node is located in the upper part of the right atrium, near the epicardium in the terminal sulcus at the junction of the right atrium and superior vena cava, and contains many autoregulatory cells. The rhythms paced by the sinus node are collectively referred to as sinus rhythms and are included in the normal rhythm of a healthy person. The diagnosis of sinus rhythm and non-sinus rhythm must be based on the electrocardiogram, and when the electrocardiogram indicates a sinus rhythm, it is a normal rhythm and there is no need to be nervous. When sinus node abnormalities cause some arrhythmias, they are called sinus arrhythmias, including sinus bradycardia, sinus tachycardia and pathological sinus syndrome. Symptoms of sinus arrhythmia may include palpitations, chest tightness, dizziness, and dark haze, while sick sinus syndrome may produce symptoms of inadequate blood supply to other organs. Most sinus arrhythmias are caused by physiological factors and have a good prognosis after treatment for the cause, so there is no need to overstress. When the duration of cardiac arrest is too long, it may be life-threatening and should be treated with a pacemaker when medication is not effective.