A heart rate of 40 beats/min means bradycardia, which requires active search for the cause. Common causes include sinus bradycardia, sinus atrial block, atrioventricular block, etc. Prompt treatment is recommended. The normal heart rate of human body is 60~100 beats/min, and the heart rate of 40 beats/min is not normal. 1. Sinus bradycardia: sinus rhythm is lower than 60 beats/min, commonly seen in young people, athletes or sleep, belong to the physiological situation, can also be seen in some patients with acute myocardial infarction, the heart rate <50 beats/min is more serious, if combined with severe organic heart disease may be dizziness, fatigue, chest tightness, palpitations and other symptoms, can be used to treat the medication, such as atropine, salbutamol and so on, if necessary, the pacemaker treatment. 2. Sinus atrioventricular block: often combined with underlying diseases, such as acute myocardial infarction, acute myocarditis, etc., need to actively treat the primary disease, and if necessary, give pacemaker treatment. 3. Atrioventricular block: especially common in third-degree atrioventricular block, need to actively treat the primary disease, such as all kinds of acute myocarditis, etc., can be treated with drugs such as salbutamol, atropine, etc., and if necessary, can be taken to the artificial pacemaker for treatment. If the heart rate is 40 beats per minute, you need to go to the hospital for timely examination and clarify the cause, and follow the doctor's instructions for diagnosis and treatment.