Need-to-know Anatomy: Ejection Fraction and Cardiomyopathy

The primary pumping action of the heart is like a spring that contracts and relaxes. When the heart is relaxed, the ventricles simultaneously fill with blood. When the heart contracts, the ventricles eject a portion of the blood they contain to either the lungs (via the pulmonary artery from the right ventricle) or the rest of the body (via the aorta from the left ventricle). That exact portion of blood pumped out of the ventricles is called the ejection fraction. In a healthy heart, the ejection fraction is greater than 55-60 percent. If the ejection fraction falls below 55 percent, the heart is no longer able to circulate an adequate amount of blood to the body at a normal heart rate. A decrease in the volume of blood circulating throughout the body can cause a cascade of changes in the body's metabolism.

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Like a spring, if a ventricle is continually overextended or stiff, it no longer functions properly. An overextended ventricle can lose the ability to contract, reducing the ejection fraction. The inverse problem can also occur where the ventricle is abnormally stiff. In this scenario, the ventricle no longer relaxes enough to fill adequately with blood. As a result, the volume of blood ejected from the heart is abnormally low because less blood has entered the heart.