Ejection fraction
Overview
The Ejection Fraction (EF) is a measurement in cardiology that indicates how well the heart is pumping blood with each beat. It is expressed as a percentage, representing the volumetric fraction of blood pumped out of the heart's main pumping chamber, the left ventricle, during each heartbeat. This measurement is crucial in diagnosing and monitoring various heart diseases.
Calculation
The ejection fraction is calculated by dividing the volume of blood pumped out of the ventricle (stroke volume) by the total volume of blood in the ventricle (end-diastolic volume). The formula is as follows:
EF = (EDV - ESV) / EDV
Where:
- EF is the ejection fraction
- EDV is the end-diastolic volume
- ESV is the end-systolic volume
Normal Values
In a healthy heart, the ejection fraction is generally between 50% and 70%. This means that with each heartbeat, the heart pumps out more than half of the blood within the left ventricle. However, these values can vary depending on factors such as age, sex, and measurement method.
Clinical Significance
The ejection fraction is a key indicator of heart function and is used in the diagnosis and management of various heart conditions. A lower than normal ejection fraction could indicate conditions like heart failure or cardiomyopathy, while a higher than normal ejection fraction could suggest hypertrophic cardiomyopathy or other conditions.
Measurement Methods
Several methods can be used to measure the ejection fraction, including echocardiography, MRI, CT scan, and nuclear medicine tests such as a MUGA scan or a PET scan. Each method has its advantages and limitations, and the choice of method depends on the patient's condition and the resources available.
Limitations
While the ejection fraction is a useful measure of heart function, it has its limitations. It does not provide information about the heart's filling phase (diastole) or about the function of the right ventricle. Furthermore, the ejection fraction can be normal in patients with heart failure with preserved ejection fraction (HFpEF), a condition in which the heart muscle becomes stiff and does not fill properly.