The ejection fraction is the proportion of blood that is pumped from the left ventricle
(the main pumping chamber of the heart) with each heart beat. Typically, the left ventricle ejects 50% or more of its blood volume with each beat, so a "normal" ejection fraction is 0.5 (50%) or higher.
A reduced ejection fraction (below 50%) often indicates that cardiac muscle weakness - or cardiomyopathy - is present. The amount of reduction in the ejection fraction often reflects the severity of cardiomyopathy. Patients with heart failure due to cardiomyopathy most often have ejection fractions below 40%.
The ejection fraction is most often measured with an echocardiogram, but it can also be measured by a MUGA scan or during a cardiac catheterization.
Also Known As: cardiac ejection fraction, left ventricular ejection fraction