An ejection fraction (EF) is one of the measurements used by physicians to assess how well a patient’s heart is functioning. “Ejection” refers to the amount of blood that is pumped out of the heart’s main pumping chamber during each heartbeat. “Fraction” refers to the fact that, even in a healthy heart, some blood always remains within this chamber after each heartbeat. Therefore an ejection fraction is a percentage of the blood within the chamber that is pumped out with every heartbeat. An EF of 55 to 75 percent is considered normal. A higher than normal ejection fraction could indicate the presence of certain heart conditions, such as hypertrophic cardiomyopathy. A low ejection fraction could be a sign that the heart is weakened.

Ejection fraction is an important tool in the diagnosis and monitoring of heart failure and certain types of cardiomyopathies. An ejection fraction of less than 40 percent may be present in these conditions. Heart failure occurs when one of the heart’s pumping chambers is not pumping well enough to meet the body’s needs. It is most commonly caused by coronary artery disease, poorly controlled high blood pressure (hypertension), and cardiomyopathy, which is a condition in which the heart is abnormally enlarged, thickened or stiffened.