The normal range of heart rate is 60-100/min, heart rate less than 60 beats/min and more than 55 beats/min belongs to bradycardia, if the pathological factors are abnormal, physiological factors are normal. Normal adult heart rate is 60-100 beats/min, adult heart rate is less than 60 beats/min, called bradycardia, there are physiological factors such as athletes, healthy adults, sleep state, physiological state without symptoms, there are pathologic factors, such as acute lower wall myocardial infarction, hyperkalemia, taking medications and so on. Physiological factors such as athletes, healthy adults, sleep state, etc. Due to the health of the body, blood oxygen saturation is high, the heart rate is lower than 60 times / min can also ensure the body’s normal blood oxygen demand. Sleep state when the body is in a dormant state, oxygen consumption is reduced, consumption is also reduced. Pathological factors such as acute lower wall myocardial infarction, hyperkalemia, taking medication and many other factors may lead to a decrease in heart rate and bradycardia. If the bradycardia is caused by pathologic factors, and there are uncomfortable symptoms such as tiredness, fatigue, chest tightness, chest pain, and so on, please consult a doctor in time, and comply with the doctor’s instructions for treatment.