In cardiovascular physiology, ejection fraction - Ef is the portion of
blood pumped out of a ventricle
with each heart strike. The term ejection fraction relates to both the
right and left ventricles;
One can speak equally of the left ventricular ejection fraction - LVEF and
the right ventricular ejection
fraction - RVEF. Without a specification,the expression Ejection Fraction
refers specifically to that of
the left ventricle.
By classification, the amount of blood within a ventricle immediately
before a contraction is known
as the end-diastolic volume. Likewise, the volume of blood left in a
ventricle at the end of contraction
is end-systolic volume. The difference between end-diastolic and
end-systolic amounts is the stroke volume,
the volume of blood ejected with each beat. Ejection fraction - Ef is the
fraction of the end-diastolic
volume that is ejected with each beat; that is,it is stroke volume (SV)
divided by end-diastolic volume (EDV):
Ef = SV/EDV = (EDV - ESV)/EDV
Normal Values of LVEF
In a healthy 160-lb man, the SV is approximately 70 ml and the left
ventricular EDV is 120 ml, calculating
an ejection fraction - LVEF of 70/120, or 0.58 (58%).
Right ventricular amount being approximately equal to those of the
left ventricle, the ejection fraction
of the right ventricle is usually equivalent to that of the left
ventricle within narrow limits.
Healthy individuals on average have ejection fractions between 50%
and 65%. Though, normal values depend upon
the modality being used to calculate the ejection fraction. Please
read E-book for more
details on that subject.
Damage to the muscle of the heart - Cardiomyopathy, weakens the
heart's capability to eject blood and as a result
reduces Ejection Fraction.
The ejection fraction is one of the most important predictors of
diagnosis. People with extensively reduced
ejection fractions typically have poorer prognoses. However, as I am
mentioning in my E-book
low LVEF is not
necessarily a major factor in diagnosis and treatment of dilated
cardiomyopathy.
Measurement of LVEF
Ejection Fraction is usually measured by echocardiography, in which
the volumes of the heart's chambers are
measured during the cardiac phase. Ejection Fraction - LVEF can
after that be obtained by dividing stroke
volume by end-diastolic volume as described above.
The most precise among commonly used methods of obtaining ejection
fraction is cardiac MRI.
Also it could be measured by fast scan 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
Please check my
E-book for more detailed
interpretation of LVEF. |
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