A heartbeat of 56 beats per minute while sleeping is normal because the metabolism of the body organs is much less at night than during the day, thus the metabolism requires less energy and the heart is less burdened, so the number of heartbeats will be lower than during the day. In addition to a slower heartbeat during nighttime sleep, blood pressure will also decrease. If the heartbeat simply slows down, there is no significant change in blood pressure, and there is no discomfort such as panic, chest tightness, chest pain, or blackness, no special treatment is needed. If the heartbeat is below 40 beats per minute, an ambulatory electrocardiogram and cardiac ultrasound are needed to clarify whether there is any abnormality. If there is sinus arrest lasting longer than three seconds or other severe slow arrhythmia, it is possible that a pacemaker may need to be placed.