2. The heart rate of healthy adults is 60 ~ 100 beats/min, most of them are 60 ~ 80 beats/min, and women are slightly faster; Children under 3 years old often exceed 100 times/minute; Older people are slow to respond. When the adult's heart rate exceeds 100 beats per minute (generally not more than 160 beats per minute) or the infant exceeds 150 beats per minute, it is called sinus tachycardia. Common in normal people after exercise, excited, excited, smoking, drinking, drinking strong tea. It can also be seen in fever, shock, anemia, hyperthyroidism, heart failure and the application of atropine, adrenaline and ephedrine. If the heart rate is 160 ~ 220 beats/min, it is often called paroxysmal tachycardia. Heart rate lower than 60 beats/min (generally higher than 40 beats/min) is called sinus bradycardia. It can be seen in athletes who have been engaged in heavy physical labor for a long time; Pathological manifestations are hypothyroidism, increased intracranial pressure, obstructive jaundice, digitalis, quinidine or propranolol overdose or poisoning. If the heart rate is lower than 40 beats/min, atrioventricular block should be considered. Heart rate is too fast to exceed 160 beats/min, or less than 40 beats/min, which is more common in patients with heart disease. Patients often have palpitations, chest tightness and precordial discomfort, so detailed examination should be carried out as soon as possible to treat the cause. 3) Every time the heart contracts, the blood output from the ventricle to the artery is called stroke output, and the blood output from the heart per minute is called stroke output. The stroke output of a normal person in a quiet state is 70 ml. If the heart rate is 75 beats per minute, the stroke output is about 5250 ml. Cardiac output is an index to measure the working ability of the heart.