Ejection fraction

An ejection fraction (EF) is the fraction of blood ejected from a ventricle of the heart with each heartbeat. It is calculated by dividing the stroke volume by the end-diastolic volume, and is an inherent measure of the pumping efficiency of the heart. Hearts that beat busily but do not succeed in expelling much blood are said to be in heart failure. Left ventricular ejection fraction is a measure of the efficiency of pumping into the systemic circulation, whereas right ventricular ejection fraction is a measure of the efficiency of pumping into the pulmonary circulation.

Ejection fraction is commonly measured by an echocardiogram and serves as a general measure of a person's cardiac function. Ejection fraction is typically low in patients with the systolic form of congestive heart failure. In contrast, one way that ejection fraction can be normal and yet heart failure can still exist is if the end-diastolic volume is too small; if there is not much blood in the ventricle to begin with, then no matter how much of it you eject, stroke volume is still small and therefore so is cardiac output. Thus SV and CO are absolute measurements, whereas EF is inherently a relative measurement (as is any fraction, ratio, or percentage).

Ejection fraction is an important determinant of the severity of systolic heart failure. Causes of systolic heart failure include coronary artery disease, congenital heart disease, valvular heart disease, conduction disease, infectious disease, and granulomatous disease among others.

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