Sinus arrhythmia is a normal physiological phenomenon, not a disease. Sinus arrhythmias are most common in children and adolescents, and are not uncommon in adults. The normal heartbeat is directed by a high command called the “sinus node”. The signal from the sinus node stimulates the heart to beat, and this signal from the sinus node causes the heart to beat, which is called normal “sinus rhythm”, with a frequency of about 60-100 beats per minute. This is how the number of heartbeats per minute, or heart rate, is derived. However, this rate can be influenced by many factors, even breathing. People diagnosed with “sinus arrhythmia” can pay attention to whether there is a relationship between the acceleration and deceleration of their heart rate and their breathing. As long as there are no other symptoms, you do not need treatment and can go about your normal studies and life. Sinus bradycardia is a condition in which the heart rate is below 60 beats per minute. Whether or not symptoms occur is related to the frequency of the bradycardia and the cause of the bradycardia. In a quiet state, adults who have a heart rate between 50-60 beats/min generally do not have significant symptoms. In particular, trained athletes and people who have been engaged in physical work for a long time will not experience significant symptoms even if their heart rate is around 40 beats per minute in a quiet state. If the heart rate drops to 35-40 beats/min, hemodynamic changes will occur, which will affect the blood supply to the heart and brain organs, resulting in chest tightness, fainting and even sudden death. If you do not have any discomfort, you do not need to pay attention to the “sinus bradycardia with arrhythmia” as stated in the ECG, but if you have chest tightness, weakness, dizziness and other discomforts, go to the hospital immediately and have an ambulatory ECG examination. In short, bradycardia can be ignored if there are no clinical symptoms and is generally not a big problem. In addition, people who exercise regularly have a slow heart rate, which is a good thing. The medical community has found that people with a moderately slow heart rate live longer than those with a fast heart rate if they are not severely bradycardic.