An ejection fraction (EF) is a percentage based on how much blood is pumped out of the heart. While no heart pumps every drop of blood back to the body, those with heart failure and other cardiovascular issues may have an EF percentage that is below normal or dangerously low. A variety of image testing technologies measure ejection fraction.
The most common method of measuring ejection fraction is an echocardiogram. Also called an echo, this is a form of ultrasound that uses sound waves to create a real-time, moving series of images of the heart and blood vessels. An ultrasound technician will run a transducer over your chest, then your cardiologist can observe and measure how much blood is leaving your left ventricle each time your heart pumps.
A catheter, which is essentially a very thin plastic tube, is inserted into one of the larger arteries of the body, generally the leg. The vessel is followed up into the heart. From here, it is possible to take pictures of what is happening inside the heart. In addition to allowing your doctor to check the blood-oxygen content of the heart and evaluate how well your heart pumps, your doctor can measure EF.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) testing can be used in numerous ways. MRIs use radio waves and magnetic imagery to create cross-sectional imaging of your body; viewing a certain part of the body in this way allows your doctor to see many different views from one diagnostic test (as opposed to the single perspective offered by a radiograph or x-ray). A cardiovascular MRI can measure EF.
Another common form of imaging technology used for diagnostic purposes is computerized tomography, also called a CT or CAT scan. Like an MRI, CT scans form cross-sectional images of a particular area of the body. Unlike MRIs, CT scans use a form of x-ray technology to do so. The goal is to take these images to coincide with the contraction, relaxation, filling, and emptying of the ventricles in the heart, thus allowing an accurate measurement of EF.
Nuclear Medicine Scan
During a nuclear medicine scan, a radioactive material is injected into your blood vessels (a common chemical is thallium). Gamma cameras designed to detect radiation follow it through the heart, lungs, and blood vessels and then creates images. When the material gets to your heart, your doctor can see how it empties or fails to empty from the heart.
To evaluate ejection fraction a stress test is conducted. The patient is usually asked to perform in some way, such as walking on a treadmill, to gradually increase the heart rate. This can affect the answers received from the nuclear scan, potentially allowing a better idea of how the blood flows.
MUGA scan is the shortened term for a radionuclide ventriculography (RVG or RNV) or angiography (RNA). It works very similarly to the nuclear medicine scan, taking pictures at key points while the blood is flowing and heart pumping. One of its specific functions is to measure ejection fraction, and it is generally used after previous tests (like an electrocardiogram) suggest there is something amiss.