The ejection fraction is a measurement of the heart's efficiency
and can be used to estimate the function of the left ventricle, which pumps
blood to the rest of the body.
The left ventricle pumps only a fraction of the blood it contains.
The ejection fraction is the amount of blood pumped divided by the amount of
blood the ventricle contains. A normal ejection fraction is more than 55% of
the blood volume. If the heart becomes enlarged, even if the amount of blood
being pumped by the left ventricle remains the same, the relative fraction of
blood being ejected decreases. For example:
A healthy heart with a total blood volume of
100 mL that pumps 60 mL to the aorta has an ejection fraction of
A heart with an enlarged left ventricle that has a total blood
volume of 140 mL and pumps the same amount (60 mL) to the aorta has an ejection
fraction of 43%.
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology