Sinus arrhythmia, including sinus tachycardia, sinus bradycardia, and sinus arrhythmia, is first and foremost a normal source of heart rate, that is, sinus rhythm. Based on this, its frequency is somewhat abnormal, and we differentiate it into sinus tachycardia or sinus bradycardia. There are cases where, although the frequency is between 60-100 beats per minute, the rhythm is irregular, which we refer to as sinus arrhythmia. So, sinus arrhythmia generally refers to these three conditions. In terms of management, sinus tachycardia often has a specific cause that needs correction. Sinus bradycardia, in some cases, leads to symptoms of insufficient cardiac output, such as fainting, which may require the installation of a pacemaker. Sinus arrhythmia usually does not require special treatment.