The American Heart Association defines ejection fraction as “a measurement, expressed as a percentage, of how much blood the left ventricle pumps out with each contraction.”

Ejection fraction is most commonly measured via an echocardiogram, which is an ultrasound of the heart.

Seems simple enough. Now here’s why ejection fraction is important to know more about.

What happens when ejection fraction is too low?

A low ejection fraction means the heart muscle has become weak, which can create a number of issues.

“One thing that may happen is a patient could develop heart failure,” said Dr. Kelley Anderson, a cardiologist at Marshfield Clinic Health System. “Fluid in the lungs and shortness of breath also can occur because of the way the heart is struggling.”

A low ejection fraction has a cascading impact on the whole body because the body is trying to compensate for a lack of blood being pumped. Anderson said you’re more likely to have abnormal heart rhythms with a low ejection fraction, which can cause cardiac arrest.

How low can you go?

Anderson broke down ejection fraction in the following way:

• 55 percent and above is considered normal
• 50-55 percent is considered low-normal
• 40-50 percent is mildly depressed
• 30-40 percent is moderately depressed
• 30 percent or below is severely depressed

What makes ejection fraction drop?

Previous heart attacks, a strong viral infection or extreme stress weakens the heart muscle and lowers your ejection fraction.

Treatment

Treatment for a low ejection fraction depends on the underlying cause.

“If it’s due to blockage in the arteries, heart attack, not getting enough blood flow, that means we correct the blood flow issue,” Anderson said. “Heart muscle weakness also may respond to a certain set of medications.”

Anderson cautions that, while ejection fraction is important to know, it doesn’t provide a full picture of your heart health. For questions about your heart health, talk with your provider.