Ejection fraction

Refers to the fraction of blood in the left and right ventricles pumped out with each heartbeat.

It 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.

EF is a ratio; a mathematical expression of forward movement of blood out of the heart contrasted to the amount retained in a single cardiac cycle.

Cardiac Imaging allowed visually enhanced mathematics of the folding and unfolding of the myocardium focused on a single cardiac cycle. 

Echocardiography, computed tomography (CT scan), magnetic resonance imaging (MRI) and radionuclide angiography (MUGA) scanning now provide the underpinning for the study of cardiac pathology such as ischemia, congenital heart disease, conduction disease, infectious disease, granulomatous disease and resulting heart failure.

Ejection fraction is most commonly measured by echocardiography: 

 cardiac magnetic resonance imaging (MRI), cardiac computed tomography, ventriculography and nuclear medicine with gated SPECT and radionuclide angiography scans may also be used. 

The volume of blood within a ventricle immediately before a contraction is known as the end-diastolic volume(EDV).

The volume of blood left in a ventricle at the end of contraction is end-systolic volume (ESV).

The difference between EDV and ESV represents a ratio between the ventricles when full and emptied.

The SV describes the volume of blood ejected from the right and left ventricles with each heartbeat.

Ejection fraction 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.

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, the stroke volume, by the volume of blood collected in the left ventricle at the end of diastolic filling.

Normal ranges:

End-diastolic volume (EDV)120 mL

End-systolic volume (ESV) 65-240 mL.

Stroke volume 70 cc.

Ejection fraction (Ef) 58%, 55–70%.

Heart rate (HR) 75 bpm, 60–100 bpm

Cardiac output 5.25 L/minute, 4.0–8.0 L/min.

In a healthy 70-kilogram (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 matches that of the left ventricle within narrow beat-to-beat limits.

Healthy individuals typically have ejection fractions between 50% and 65%.

The 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. 

With heart failure, there is often, but not invariably reduced ventricular ejection fraction.

Repeat measurements of LVEF in the same patient using the same methods in echocardiography vary by 70%, and their ability is greater in clinical practice.

It is likely that a significant number of patients with a LVEF of 40-50% could be reclassified as having an LVEF lower than 40% or higher than 50% if the measurement was repeated.

Patients with heart failure and reduced ejection fraction typically have evidence of increased circulating levels of proteins that reflect the occurrence of cardiomyocyte injury, loss, and stretch.

Patient to have heart failure and a LVEF higher than 50% typically show bio markers that reflect systemic inflammation and evidence of endothelial injury and myocardial fibrosis.

Patients with LVEF of 40-50% exhibit a pathophysiological profile that resembles patients with LVEF lower than 40%.

Damage to the myocardium, such as that by myocardial infarction, atrial fibrillation or a cardiomyopathy, compromises the heart’s ability to eject blood) and, therefore, reduces ejection fraction.

This reduction in the ejection fraction can manifest as heart failure, and a low ejection fraction is manifest at 40% with symptomatic findings constant at 25%.

The ejection fraction is an important predictor of prognosis.

Guidelines indicate that the low end of normal for LVEF is 52% in men and 54% in women.

A LVEF 41-51% in men and 41%-53% in women is required it is mildly reduced.

Commonly measured by echocardiography, in which the volumes of the heart’s chambers are measured during the cardiac cycle and the ejection fraction can then be obtained by dividing stroke volume by end-diastolic volume,

Other methods of measuring ejection fraction include cardiac MRI, 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 gold standard for the measurement of ejection fraction is ventriculography.

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