What is ejection fraction and what does it measure?

Ejection fraction is a measurement of the percentage of blood leaving your heart each time it contracts.

During each heartbeat pumping cycle, the heart contracts and relaxes. When your heart contracts, it ejects blood from the two pumping chambers (ventricles). When your heart relaxes, the ventricles refill with blood. No matter how forceful the contraction, it never is able to pump all of the blood out of a ventricle. The term "ejection fraction" refers to the percentage of blood that's pumped out of a filled ventricle with each heartbeat. Ejection fractions are calculated during an echocardiogram.

Typically, the left ventricle is the heart's main pumping chamber that pumps oxygenated blood through the aorta to the rest of the body, so ejection fraction is usually measured only in the left ventricle (LV). An LV ejection fraction of 55 percent or higher is considered normal. An LV ejection fraction of 50 percent or lower is considered reduced. Experts vary in their opinions about an ejection fraction between 50 and 55 percent, and some would consider this a "borderline" range.

For individuals with hypoplastic left heart syndrome (HLHS), the right ventricle is the heart’s main pumping chamber. A good ejection fraction for someone with HLHS would be above 50 percent. Many individuals with HLHS have right ventricular ejection fractions that are somewhat less than this range but do not have any significant limitations. One of the goals of our HLHS program is to better understand what is a good measure of ventricular function in a person with HLHS and how to best clinically describe it so that we can recognize a decline in function and treat it.

The Todd and Karen Wanek Family Program for Hypoplastic Left Heart Syndrome (HLHS) is a collaborative network of specialists bonded by the vision of delaying or preventing heart failure for individuals affected by congenital heart defects including HLHS. The specialized team is addressing the various aspects of these defects by using research and clinical strategies ranging from basic science to diagnostic imaging to regenerative therapies. To learn more or to participate in the research, email HLHS@mayo.edu.