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Ejection fraction

The meaning of «ejection fraction»

An ejection fraction (EF) is the volumetric fraction (or portion of the total) of fluid (usually blood) ejected from a chamber (usually the heart) with each contraction (or heartbeat). It can refer to the cardiac atrium,[1] ventricle,[2] gall bladder,[3] or leg veins,[4] although if unspecified it usually refers to the left ventricle of the heart. EF is widely used as a measure of the pumping efficiency of the heart and is used to classify heart failure types. It is also used as an indicator of the severity of heart failure, although it has recognized limitations.[5]

The EF of the left heart, known as the left ventricular ejection fraction (LVEF), is calculated by dividing the volume of blood pumped from the left ventricle per beat (stroke volume) by the volume of blood collected in the left ventricle at the end of diastolic filling (end-diastolic volume). LVEF is an indicator of the effectiveness of pumping into the systemic circulation. The EF of the right heart, or right ventricular ejection fraction (RVEF), is a measure of the efficiency of pumping into the pulmonary circulation. A heart which cannot pump sufficient blood to meet the body's requirements (i.e., heart failure) will often, but not invariably, have a reduced ventricular ejection fraction.[6]

Modalities applied to measurement of ejection fraction is an emerging field of medical mathematics and subsequent computational applications. Perhaps the first common bedrock measurement method was echocardiography,[7][8] although cardiac magnetic resonance imaging (MRI),[8][9] cardiac computed tomography,[8][9] ventriculography and nuclear medicine (gated SPECT and radionuclide angiography)[8][10] scans may also be used. Measurements by different modalities are not easily interchangeable.[11] Historically, the gold standard for measurement of the ejection fraction was ventriculography,[12] but cardiac MRI is now considered the best method.[13] Prior to these more advanced techniques, the combination of electrocardiography and phonocardiography was used to accurately estimate ejection fraction.[14]

In a healthy 70-kilogram (150 lb) man, the stroke volume is approximately 70 mL, and the left ventricular end-diastolic volume (EDV) is approximately 120 mL, giving an estimated ejection fraction of .mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}70⁄120, or 0.58 (58%). Healthy individuals typically have ejection fractions between 50% and 65%,[15] although the lower limits of normality are difficult to establish with confidence.[16]

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