Sinus arrhythmia is an arrhythmia caused by an abnormality in the frequency of sinus node impulse delivery or a block in the conduction of sinus impulses to the atria. They are categorized according to electrocardiogram and clinical presentation as sinus tachycardia, sinus bradycardia, sinus arrest, sinus block, and sick sinus node syndrome. The impulses of normal sinus rhythm originate in the sinus node at a frequency of 60 to 100 beats per minute. The P wave of the ECG manifest rhythm is upright in leads I, II, and aVF, and inverted in lead aVR; the PR interval is 0.12 to 0.20 seconds. Arrhythmias can be caused by abnormalities in the frequency of sinus node impulse delivery or by blocked conduction of sinus impulses to the atria. In case of related diseases, it is recommended to visit the hospital in time and follow the doctor’s prescription for medication.