From Wikipedia, the free encyclopedia  View original article

ejection fraction (EF) is the fraction of blood in the left and right ventricles pumped out with each heartbeat. In mathematics allowed by medical imaging, EF is applied to both the right ventricle, which ejects blood via the pulmonary valve into the pulmonary circulation, and the left ventricle, which ejects blood via the aortic valve into the cerebral and systemic circulation. RVEF + LVEF = EF.
Imaging of the heart allows for mathematical expressions defining flow of blood into and out of the heart. EF is essentially a ratio; a mathematical expression of forward movement of blood out of the heart contrasted to the amount retained in a single cardiac cycle. One important mathematical expression involves easily reproduced volumetrics. As a volumetric mathematical term, ejection fraction is an extension of work by Adolph Fick entitled Cardiac Output. EF=CO. Fick's theory was gradually merged to fit the precision of wall motion mathematics first defined by Laplace. This led to the introduction of compliance and lengthtension in the Frank–Starling law of the heart. Echocardiography, computed tomography (CT scan), magnetic resonance imaging (MRI) and radionuclide angiography (MUGA) scanning have allowed the study of ischemia, congenital heart disease, conduction disease, infectious disease, granulomatous disease and resulting heart failure.
This section does not cite any references or sources. (March 2013) 
By definition, the volume of blood within a ventricle immediately before a contraction is known as the enddiastolic volume (EDV). Likewise, the volume of blood left in a ventricle at the end of contraction is endsystolic volume (ESV). The difference between EDV and ESV represents a ratio between the ventricles full and emptied. This ratio allows many variables such as stroke volume (SV). SV describes the volume of blood ejected from the right and left ventricles with each heartbeat. Ejection fraction is the fraction of the enddiastolic volume that is ejected with each beat; that is, it is stroke volume (SV) divided by enddiastolic volume (EDV):^{[1]}
Where the stroke volume is given by:
Measure  Typical value  Normal range 

enddiastolic volume (EDV)  120 mL^{[2]}^{[nonprimary source needed]}  65–240 mL^{[2]}^{[nonprimary source needed]} 
endsystolic volume (ESV)  50 mL^{[2]}^{[nonprimary source needed]}  16–143 mL^{[2]}^{[nonprimary source needed]} 
stroke volume (SV)  70 mL  55–100 mL 
ejection fraction (E_{f})  58%  55–70%^{[3]} 
heart rate (HR)  75 bpm  60–100 bpm^{[4]} 
cardiac output (CO)oo  5.25 L/minute  4.0–8.0 L/min^{[5]} 
In a healthy 70kilogram (150 lb) man, the SV is approximately 70 mL and the left ventricular EDV is 120 mL, giving an ejection fraction of ^{70}⁄_{120}, or 0.58 (58%).
Right ventricular volumes being roughly equal to those of the left ventricle, the ejection fraction of the right ventricle physiologically matches that of the left ventricle within mathematically narrow beattobeat limits.
Healthy individuals typically have ejection fractions between 50% and 65%.^{[6]} However, normal values depend upon the modality being used to calculate the ejection fraction, and some sources consider an ejection fraction of 55% to 75% to be normal. Damage to the muscle of the heart (myocardium), such as that sustained during myocardial infarction or in atrial fibrillation or a plurality of etiologies of cardiomyopathy, compromises the heart's ability to perform as an efficient pump (ejecting blood) and, therefore, reduces ejection fraction. This reduction in the ejection fraction can manifest itself clinically as heart failure. A low ejection fraction has its cutoff below 40% with symptomatic manifestations constant at 25%.^{[7]} In the USA, a chronically low ejection fraction less than 30% is qualifying support for eligibility of disability benefits from the Social Security Administration.^{[8]}
Healthy older adults favorably adapt as the ventricles become less compliant and are routinely echocardiographically proven to have an EF from 55–85% with the help of good genetics and a healthy lifestyle. Compliance changevolume /changepressure is a property of the heart that allows contractility. Encyclopedic documentation of the commonly documented "hyperdynamic" ventricle remains sparse.
The ejection fraction is one of the most important predictors of prognosis; those with significantly reduced ejection fractions typically have poorer prognoses. However, recent studies have indicated that a preserved ejection fraction does not mean freedom from risk.^{[9]}^{[nonprimary source needed]}^{[10]}^{[nonprimary source needed]}
The QT interval as recorded on a standard electrocardiogram (EKG) represents ventricular depolarazation and ventricular repolarazation and is ratedependent.^{[11]}^{[nonprimary source needed]}
This section does not cite any references or sources. (March 2013) 
Ejection fraction is commonly measured by echocardiography, in which the volumes of the heart's chambers are measured during the cardiac cycle. Ejection fraction can then be obtained by dividing stroke volume by enddiastolic volume as described above.
Accurate volumetric measurement of performance of the right and left ventricles of the heart is inexpensively and routinely echocardiographically interpreted worldwide as a ratio of the dimension between the ventricles in systole and diastole. For example, a ventricle in greatest dimension could measure 6 cm while in least dimension 4 cm. Measured and easily reproduced beat to beat for ten or more cycles, this ratio may represent a physiologically normal EF of 5060%. Mathematical expression of this timedependent ratio can then be interpreted as the greater half as cardiac output and the lesser half as cardiac input.
Other methods of measuring ejection fraction include cardiac MRI, fastscan cardiac computed axial tomography (CT) imaging, ventriculography, gated SPECT, and the MUGA scan. A MUGA scan involves the injection of a radioisotope into the blood and detecting its flow through the left ventricle. The historical gold standard for the measurement of ejection fraction is ventriculography.
