What is Ejection Fraction?

The significance of this measurement of heart health

heart chamber and valves
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Ejection fraction (EF) is a measurement cardiologists use to assess the strength of the heart. It represents a comparison of how much blood is retained by one ventricle of the heart at the beginning of a beat with how much blood remains after the ventricle completes the beat.

The measurement reflects the proportion of blood the ventricle is strong enough to move and most often is expressed as a percentage. For example, if 60% of the blood in the ventricle is pushed out, then the EF is expressed as either 60% or written as a decimal—0.6.

Ejection fraction is a useful factor in diagnosing and monitoring heart failure. It's most easily determined with an echocardiogram, although there are other tests that can be used to measure EF.

Although the heart has two ventricles, it is the ejection fraction of the left ventricle—often referred to as LVEF (left ventricular ejection fraction)—cardiologists focus on when measuring ejection fraction.

Significance of LVEF

When the heart becomes weak, the muscle fibers become unable to contract fully, decreasing the volume of blood pumped per beat— what is known as "stroke volume."

To compensate, the heart becomes larger in order to hold more blood, allowing for a more normal stroke volume to be maintained. Cardiac dilation that occurs with heart muscle disease is known as "remodeling."

Enlargement of the heart, cardiomegaly, is a compensatory mechanism that staves off symptoms of heart failure by maintaining a normal cardiac output for as long as possible. The fact that the heart is dilated indicates the heart muscle is weakened.

As a measure of the overall strength of the heart, ejection fraction is helpful for diagnosing cardiomegaly, as well as other heart problems such as cardiomyopathy (weakness of the heart muscle that can be a precursor of heart failure) and coronary artery disease (CAD).

Therefore, a cardiologist might choose to measure the ejection fraction of someone who has symptoms associated with poor heart function, such as:

  • Dyspnea (shortness of breath)
  • Edema (swelling) of the feet and lower legs
  • Unexplained fatigue
  • Muscle weakness
  • Rapid, forceful, uncomfortable, or irregular heart beat
  • Abdominal swelling or pain
  • Nausea
  • Confusion

Doctors also use ejection fraction to monitor cardiac health after a heart attack, determine the treatment for heart failure, and assess the effectiveness of that treatment.

How LVEF Is Measured

Ejection fraction can be determined in one of three ways:

  • Echocardiogram. Regarded as the most efficient way to monitor ejection fraction over time, this non-invasive imaging test uses ultrasound to view the heart in motion.
  • Multigated acquisition (MUGA) scan. Also a non-invasive test, the MUGA scan is considered the most accurate and reproducible method of measuring ejection fraction. It typically is repeated—precise measurements are needed— to monitor heart health in someone taking a chemotherapy medication known to be damaging to the heart muscle, such as doxorubicin.
  • Cardiac catheterization, the most invasive way to measure ejection fraction. The procedure involves inserting a catheter into blood vessels in the groin, wrist, neck, or arm. It is the only method of measuring LVEF that has potential risks and complications.

Interpreting Results

The more blood the left ventricle can push out with each heartbeat the stronger the heart. This makes it relatively easy to understand what an LVEF reading means: The higher the percentage, the healthier the heart.

Cardiologists do use certain standards when interpreting LVEF results in terms of evaluating heart health based on the fact the left ventricle typically ejects 55% or more of its blood volume per beat.

Normal 50% to 70%
Below normal 41% to 49%
Indication of heart failure Equal to or less than 40%
Source: American Heart Association

An LVEF of 40% or less is referred to as heart failure with preserved ejection fraction (HFpEF) or diastolic heart failure—an indication that as a result of remodeling, the heart muscle has become thick or rigid, preventing the normal volume of blood from filling up ventricles.

An ejection fraction of greater than 75% also can indicate a heart condition known as hypertrophic cardiomyopathy that causes the heart muscle to thicken and can lead to cardiac arrest.

A Word from Verywell

"Ejection fraction" may sound like a complicated clinical term but in fact it simply is a measurement of how much blood your heart can pump with each beat. Because the left ventricle of the heart is the one cardiologists test, if your doctor shares with you that you have an LVEF of less than 40%, it means you may have heart failure. With this knowledge, they can develop a treatment plan that is appropriate for you so you can begin to deal with your condition right away. Doing so can potentially prevent your heart from weakening further and lowering your risk of long-term complications.

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  3. Gazewood JD, Turner PL. Heart failure with preserved ejection fraction: Diagnosis and management. Amer Fam Phys. Nov 1, 2017;96(9):582-588.