Stroke volume is a measurement of how much blood the heart pumps out of a ventricle with each beat. It is determined by subtracting the amount of blood left in a ventricle after contraction from the total volume of blood in the ventricle when it is filled. This is one among several measurements that can be taken to measure heart health and learn more about a patient's general level of physical condition. In an average adult male, it is around 70 milliliters.
There are two ventricles in the four-chambered human heart. The right ventricle directs blood to the lungs for oxygenation, while the left ventricle pumps blood into the circulation. In healthy individuals, the stroke volume for both ventricles is about the same. Together, this measurement and the heart rate provide a measure of cardiac output, indicating how much blood the heart pumps out in a minute.
The process of filling the ventricle is known as diastole. At the end of diastole, the ventricle is filled with blood that is squeezed out with a contraction during systole. The contraction does not force all of the blood in the ventricle out, however. Only a fraction is pumped out and this fraction is the stroke volume. Medical imaging studies with contrast dyes can be used to measure this amount in a patient if there is a concern that it is abnormal. Catheterization is another tool that can be used to take measurements.
In athletes, stroke volume increases with training. This reduces the number of times the heart needs to beat per minute because it is pumping out more blood with each beat. This is why the resting heart beats of athletes are lower than those of the general population, and it also explains why athletes who are very fit need to work harder to get their heart rates up.
There are other measures that can be used to assess heart health, including listening to the heart, studying it with an electrocardiogram, and measuring other components of the cardiac cycle, the series of stages the heart goes through as it beats. A cardiologist is usually involved in assessment of a patient with a suspected heart problem and this medical professional can determine the appropriate tests to use to diagnose the patient accurately and effectively. If the testing uncovers a medical issue, there are many treatment options to explore.