What is stroke volume (stroke volume)

Stroke volume refers to the amount of blood ejected from one ventricle during a single contraction of the heart, which is approximately 60-80 milliliters in the resting state of a normal adult. It is one of the core indicators for evaluating the pumping function of the heart. The main factors affecting stroke volume include myocardial contractility, ventricular filling volume, peripheral vascular resistance, heart rate changes, and autonomic nervous system regulation.

1. Myocardial contractility:

The degree of myocardial fiber shortening directly affects stroke volume, and when contractility increases, ejection volume increases. Positive inotropic drugs such as digoxin can enhance contractility, while pathological conditions such as myocardial ischemia and heart failure can lead to a decrease in contractility. During exercise, sympathetic nervous system excitation increases myocardial contractility by releasing norepinephrine.

2. Ventricular filling volume:

The preload of ventricular end diastolic volume determines the initial length of the myocardium. According to the Frank Starling mechanism, an increase in filling volume can correspondingly increase stroke volume. But when it exceeds physiological limits, such as acute heart failure, excessive filling actually reduces pumping efficiency. Venous reflux, changes in body position, and blood volume can all affect filling volume.

3. Peripheral vascular resistance:

Aortic pressure constitutes the cardiac afterload, and when resistance increases, such as hypertension, it will increase ventricular ejection resistance, leading to a temporary decrease in stroke volume. The body maintains cardiac output by compensatory enhancement of myocardial contraction, and long-term high load may cause adaptive changes such as ventricular hypertrophy.

4. Heart rate changes:

A heart rate greater than 160 beats per minute will shorten ventricular filling time and reduce stroke volume; Although a heart rate of less than 40 beats per minute increases single ejection volume, the total cardiac output decreases. Atrial fibrillation and other arrhythmias can lead to uneven ventricular filling, causing fluctuations in stroke volume.

5. Autonomic nervous regulation:

The sympathetic nervous system enhances myocardial contractility and heart rate through β 1 receptors, while the parasympathetic nervous system inhibits cardiac activity through the vagus nerve. Physiological changes such as emotional stress and postural regulation are finely regulated by the autonomic nervous system in terms of stroke volume.

Regular aerobic exercise can enhance myocardial contraction reserve capacity. It is recommended to engage in 150 minutes of moderate intensity exercise such as brisk walking and swimming per week. Pay attention to controlling sodium intake in diet to avoid excessive blood volume. Increasing bananas and dark green vegetables rich in potassium and magnesium can help maintain normal electrocardiogram activity. Smoking can damage vascular elasticity and increase afterload, so strict smoking cessation is necessary. Regularly monitor blood pressure and resting heart rate. When there are abnormal cardiac functions such as shortness of breath and lower limb edema after activity, timely cardiac ultrasound and exercise stress tests should be performed to evaluate changes in stroke volume.