Blood constantly flows through the heart. The right side of the heart receives low oxygen blood, sends it to the lungs for oxygenation, and the left side distills oxygen-rich blood to the body. However, the amount of blood and the time during which this occurs is of great importance to health. The heart should be able to receive and expel enough blood to maintain oxygen supply to the whole body. It is necessary for life.
What is cardiac output?
Cardiac output is the amount of blood that is pumped out of the heart in a minute. It is calculated by the heart rate (beats per minute) multiplied by the stroke volume (the amount of blood pushed out of the heart during the contraction). If the cardiac output is too low, then the body does not receive enough oxygen to function normally.
The heart is a muscle pump. It can stretch to hold blood but it can also compress with force. This contributes to the expulsion by the heart of blood to the body. At rest (diastole), blood from the body or lungs fills the atria (the only atrium). There are two atria – the right atrium and the left atrium.
The right atrium receives blood with low oxygen content from the body, and the left atrium receives oxygen-rich blood from the lungs. This blood from the atria then enters the ventricles. When the heart contracts (systole), blood is expelled from the ventricles and sent to the lungs and body.
The right ventricle sends low oxygen blood to the lungs for oxygenation. The left ventricle sends oxygen-enriched blood to the rest of the body. This process (cardiac cycle) is carefully coordinated so that the heart can work at its peak without undue stress on the heart muscle. There are a number of factors that should be considered for cardiac output.
How much blood does the heart pump?
The amount of blood that the heart pumps per minute (cardiac output) varies in different people. It depends on various factors. For example, the heart needs to pump more blood during exercise because the body’s need for oxygen increases. On average, an adult’s heart pumps 3 to 4 liters of blood per minute when the person is at rest.
Causes of low or high cardiac output
Low cardiac output is a problem because the body cannot receive enough oxygen for its needs. On the other hand, high cardiac output can also be dangerous, as it can lead to heart stress with many serious complications.
Any heart disease in which the function of the heart is reduced can lead to a decrease in cardiac output. It could be:
- Myocardial infarction (heart attack);
- Cardiomyopathy;
- Heart failure (due to various reasons);
- Excessive blood loss;
- Sepsis (blood poisoning).
High cardiac output can be provoked by:
- Anemia;
- Hyperthyroidism;
- Sepsis.
It is important to note that various methods can affect cardiac output, even when the heart is healthy. Cardiac activity is determined by many factors – from hormones to nerve impulses. Therefore, cardiac output can suddenly change when there is a disorder elsewhere in the body that affects the cardiovascular system.