Currently, if the heart rate is 55 beats per minute at rest, this heart rate is theoretically abnormal. However, in practice, we believe that this heart rate is acceptable, because many patients may be due to family hereditary reasons, or long-term engaged in heavy physical labor or the patient himself is an athlete, relatively slow heart rate, but such patients often do not have any uncomfortable symptoms. There are also some elderly patients, may be taking a special drug caused by, and often the doctor is recommended to take such drugs, to control the heart rate deliberately relatively slow, because this can slow down the patient’s heart rate, reduce myocardial oxygen consumption, so as to better prevent angina pectoris as well as the re-emergence of heart failure symptoms.