heart with ejection fraction

Causes of an Abnormal Ejection Fraction

Ejection fraction (EF) is the measurement of how much blood is leaving the heart when it contracts. The left ventricle is particularly important to this measurement, as it is the chamber of the heart that sends freshly oxygenated blood all over the body. Here’s a look at some diseases that can cause a low ejection fraction. 

Heart Failure

Ejection fraction can be used to help diagnose various cardiovascular diseases. A normal ejection fraction runs between 50-70%; a percentage in the 40s is considered below normal, and under 40% is considered a low EF and is possibly indicative of a variety of heart issues. Heart failure, in particular, is diagnosed and evaluated through a changing ejection fraction. 

Some people may have heart failure with a perfectly normal ejection fraction, which is now called heart failure with normal or preserved ejection fraction. However, it isn’t necessarily that the EF is normal -- the heart muscle can become thick and stiff, preventing a normal amount of blood from entering it in the first place. This means when viewed, it appears that most of the blood is leaving the heart -- but there wasn’t enough blood to begin with. 


There are several different forms of cardiomyopathy that cause a low ejection fraction. Dilated cardiomyopathy, for example, is a disease characterized by a large but weak heart muscle. As the heart grows weaker over time, cardiomyopathy can lead to heart failure. According to the American Heart Association, dilated cardiomyopathy is often called by other terms, generally explanatory as to their cause. These causes may be:

  • Genetic
  • Excessive consumption of alcohol
  • Diabetes
  • Heart attack
  • Coronary artery disease
  • Peripartum (occurs during pregnancy)

Another form of cardiomyopathy, called hypertrophic cardiomyopathy, can actually be detected by a high ejection fraction -- over 75%. The cells of the heart grow larger, causing the ventricles to become thick. The ventricle may stay the same size, but its thickness can inhibit normal blood flow. 

Other Damage and Issues

A low ejection fraction can also be the result of sustained damage to the heart. When the ejection fraction is between 41-49%, it is generally due to a previous heart attack. According to the Mayo Clinic, if your heart’s valves, the little flaps that allow blood to flow between chambers, have something wrong with them, this too can cause a low EF. Additionally, if you have uncontrolled high blood pressure you can eventually experience heart damage to such an extent that it results in a low EF. If you suspect your ejection fraction isn’t where it should be, talk to your doctor as soon as possible. 

Last Updated: January 11, 2017