The proportion of blood pushed out of one of the heart’s two pumping chambers, the left and right ventricles, when it contracts. The ejection fraction, commonly expressed as a percentage, indicates how strong the ventricles are — that is, how well they pump blood. The right ventricle pumps blood to the lungs, and the left ventricle to the rest of the body. Typically, doctors measure the ejection fraction of the left ventricle. If the right ventricle is used, then the result is referred to specifically as the “right ventricular ejection fraction.”
When a ventricle in a healthy heart contracts, more than half the volume of blood in the chamber is pumped out. A normal ejection fraction is generally considered to lie between 55% (according to some authorities) and around 75%. An ejection fraction lower than this may indicate that the ventricle is weakened, suggesting some degree of heart failure — a condition in which the heart is not pumping enough blood to meet the body’s needs. An abnormally high ejection fraction may also indicate the existence of a heart problem, such as hypertrophic cardiomyopathy.
Among the methods that may be used to determine the ejection fraction are echocardiography, which produces an ultrasound image of the heart; various forms of nuclear medicine scanning, typically involving the use of a radioactive dye injected into a blood vessel or carried via a catheter to the heart; and the x-ray technique known as computed tomography (CT) scanning.