1. cardiac output
(1) output per stroke and output per minute: the amount of blood discharged from a ventricle in a heartbeat is called output per stroke. The blood output per minute of a ventricle is called the output per minute, which is equal to the product of heart rate and stroke volume. The output of the left and right ventricles is basically equal. Cardiac output is adapted to the metabolic level of the body, and the metabolic level may be different due to gender, age and other physiological conditions. For example, in a quiet state, the stroke volume of an adult is about 70ml(60-80ml) and the cardiac output is 5 L/min (5-6 L/min). The cardiac output of women is about 10% lower than that of men of the same weight. The cardiac output can be as high as 25 ~ 35 min during strenuous exercise and can be reduced to 2.5 l/min under anesthesia.
(2) Heart index: the cardiac output per square meter of body surface area is called the heart index, and the heart index in quiet and fasting state is called the resting heart index. The resting heart index of middle-height adults in China (body surface area is about 1.6 ~ 1.7m2) is 3.0-3.5/(min ㎡). When analyzing and comparing the cardiac function between different individuals, cardiac index is a commonly used evaluation index.
2. Ejection fraction
The percentage of stroke volume to ventricular end-diastolic volume is called ejection fraction. In a quiet state, the ejection fraction of healthy adults is 55% ~ 65%. It is not comprehensive to evaluate the pumping function of the heart only by using stroke output as an index without considering ventricular end-diastolic volume. Under normal circumstances, the stroke volume always adapts to the ventricular end-diastolic volume, that is, when the ventricular end-diastolic volume increases, the stroke volume increases accordingly, and the ejection fraction remains basically unchanged. However, in the case of abnormal ventricular enlargement and decreased cardiac function, the stroke volume may not be significantly different from that of normal people, but its ejection fraction decreased significantly. If we only evaluate the pumping function of the heart according to the stroke output, we may make a wrong judgment.
3. Heart does work
The work done by ventricular contraction is called stroke work, which can be expressed by the increase of kinetic energy and pressure energy of pumping blood. The unit of work per stroke is g.m. The unit of stroke work multiplied by heart rate is kg. m/min. The simplified formula for calculating left ventricular stroke work and stroke work is as follows: stroke work (g.m) = stroke output (cm3) × (11000 )× (mean arterial pressure-mean left atrial pressure mmHg).
Work per minute (kg m/min) = Bo Gong (g m) × Heart rate × (11000)
The left ventricular work was 83.65438±0g·m；; ; The work per minute is 6.23 kg m/min.
The stroke volume of the right ventricle is equal to that of the left ventricle, but the average pressure of the pulmonary artery is only about 1/6 of that of the aorta, so the work done by the right ventricle is only 1/6 of that of the left ventricle. The advantage of stroke work index is that it considers the influence of arterial blood pressure on cardiac pumping function, so it is more meaningful to evaluate cardiac pumping function as work than stroke volume and cardiac output.