A heart rate of 42 to 45 beats per minute is normal during sleep. Under normal circumstances, the human body’s normal heart rate of 60 to 100 beats per minute, in the state of sleep, due to the parasympathetic and vagus nerve excitability increases, metabolism slows down, the heart rate will be slowed down, if the human body’s mental state and physical state is normal, there is no dizziness, dyspnea, conduction block and so on, it is a normal phenomenon, do not have to worry about it too much. If the heart rate is lower than 30 beats per minute while sleeping, or there are phenomena such as stopping beating, dyspnea, conduction block, dizziness, chest pain, etc., it is necessary to go to the hospital in a timely manner through the 24-hour dynamic electrocardiogram, cardiac ultrasound and other imaging examinations to discover the condition in a timely manner and symptomatic treatment, so as to avoid affecting the health of the body.