Ejection Fraction

the heart
sot/Getty Images

When doctors want to make an objective assessment of the heart’s ability to pump blood, they measure what is called the ejection fraction. Specifically, the ejection fraction compares the volume of blood held within a cardiac ventricle at the beginning of the heart beat, to the volume of blood that remains after the ventricle finishes beating. In the words, it is a measure of the proportion of blood that is actually ejected by a ventricle (most typically, the left ventricle) with each the heart beat. 

If the ventricle ejects 60% of the blood it holds at the beginning of each heart beat, its ejection fraction is 60% (sometimes expressed as a decimal, such as 0.6).

The ejection fraction is very commonly used in medicine for a number of reasons. It is easy to measure non-invasively; it is reproducible (so you get the same answer if you repeat the test); and it can be used as time goes by to assess changes in cardiac function.

Typically, the left ventricle ejects 55% or more of its blood volume with each beat, so a "normal" ejection fraction is 55% (0.55) or higher. An ejection fraction of 40 - 50% is considered “below normal.” People who have heart failure due to cardiomyopathy most often have ejection fractions that are less than 40%.

Terminology of “Ejection Fraction”

It is important to note that when doctors say the words “ejection fraction” they are referring to the ejection fraction of the left ventricle. More properly this would be called the “left ventricular ejection fraction” or “LVEF” and you may sometimes see or hear this terminology.

The right ventricle also has its own ejection fraction (the “right ventricular ejection fraction,” or RVEF). However, the RVEF is rarely mentioned or talked about by doctors, partly because it is much more difficult to measure than the LVEF, and partly because knowing the precise RVEF is usually not particularly useful.

So when your doctor says “ejection fraction,” he or she is referring to the LVEF.

Why Does Heart Disease Sometimes Cause a Reduced Ejection Fraction?

When the heart muscle becomes weak, the muscle fibers become incapable of contracting fully. That is, the shortening of the muscle fibers that occurs with muscle contraction is diminished. This means that, unless there is compensation for the poor muscle function, amount of blood pumped with each heartbeat (the “ stroke volume ”) would diminish.

To compensate for this shortcoming, the heart dilates, allowing for a normal (or near-normal) stroke volume to be maintained despite reduced muscle fiber shortening. This dilation means that the proportion of blood being ejected during each heartbeat is diminished (that is, the ejection fraction falls) — but the stroke volume tends to remain at a nearly normal level.

As an example, consider a person whose left ventricle holds 100 cc of blood and has an ejection fraction of 50%. That person has a stroke volume of 50cc. If his ejection fraction were later to drop to 40%, his heart would tend to dilate enough to still allow for a 50cc stroke volume with each heart beat — which would imply a dilation sufficient to hold 125 cc. (This is why people with heart failure tend to develop enlarged hearts.)

Another name for the compensatory cardiac dilation that occurs with heart muscle disease is “remodeling.”

How Is the Ejection Fraction Measured?

The ejection fraction is most often measured with an echocardiogram, but it can also be measured by a MUGA scan or during a cardiac catheterization. The MUGA scan is usually the most accurate and reproducible method of measuring the ejection fraction, and it is typically used in situations where repeated, precise measurements are needed; for instance, when chemotherapy is being used that can be toxic to the heart muscle - most commonly, doxorubicin (Adriamycin). However, in most cases the echocardiogram is the most efficient way to monitor a person’s ejection fraction over time.

How Do Doctors Use the Ejection Fraction Measurement?

The ejection fraction is useful as a measure of the overall strength of the heart. The lower the ejection fraction, the weaker the heart muscle (since more cardiac dilation is required to maintain the cardiac stroke volume). If the ejection fraction is falling, that generally means the heart muscle is becoming weaker. An increasing ejection fraction usually means the heart muscle strength is improving.

Doctors use the ejection fraction measurement to diagnose cardiomyopathy, to assess the effectiveness of medical therapy in stabilizing or improving heart failure, and to decide on the best treatment approaches for heart failure.

View Article Sources
  • Lang RM, Bierig M, Devereux RB, et al. Recommendations for Chamber Quantification: a Report From the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 2005; 18:1440.
  • American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Society of Echocardiography, American Heart Association, et al. ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Society of Echocardiography, American Heart Association, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Critical Care Medicine, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance American College of Chest Physicians. J Am Soc Echocardiogr 2011; 24:229. doi: 10.1016/j.echo.2010.12.008.