Ejection Fraction

the heart
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The ejection fraction is a measurement doctors very commonly use to assess how well the heart is able to pump blood. Specifically, the ejection fraction is the proportion of blood that is pumped from the left ventricle (the main pumping chamber of the heart) with each heart beat.

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.” Patients with heart failure 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.)

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.

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).

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.

For instance, an ejection fraction of less than 35% greatly increases a patient’s odds of developing cardiac arrest, and in general ought to provoke a discussion of an implantable defibrillator.

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.