A heart rate of about 40 beats/minute may be associated with myocardial infarction and other pathologic factors, and is more dangerous. A heart rate of about 40 beats per minute is considered bradycardia, and a physiologic slow heart rate is usually not as low as about 40 beats per minute, and there are often no symptoms of dizziness or other discomforts, and the heart rate tends to increase and return to normal after exercise. Therefore, a heart rate level of about 40 beats per minute is most likely to be pathologic. Heart disease such as myocardial infarction, sinus node disease, atrioventricular block, and myocarditis, as well as hypothyroidism and intracranial disease, may result in a heart rate of about 40 beats per minute. Pathological bradycardia is more dangerous, may lead to dizziness, blackout, fainting and other manifestations of the patient, the serious can appear organs blood supply shortage, even induced cerebral infarction, coronary heart disease, or life-threatening. Therefore, it is recommended to consult a doctor as soon as possible to standardize the diagnosis and treatment.