Ejection fraction: What does it measure?

During each heartbeat cycle, the heart contracts and relaxes. When your heart contracts (systole), it ejects blood from the two pumping chambers (ventricles). When your heart relaxes (diastole), the ventricles refill with blood. No matter how forceful the contraction, it doesn't empty 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. This measures the capacity at which your heart is pumping.

Because the left ventricle is the heart's main pumping chamber, ejection fraction is usually measured only in the left ventricle (LV). A normal LV ejection fraction is 55 percent to 70 percent. The ejection fraction may decrease when the heart muscle has been damaged, such as due to:

• Heart attack
• Heart-muscle disease (cardiomyopathy)
• Heart valve problems

A doctor can measure ejection fraction by several methods, including:

• An ultrasound of the heart (echocardiography)
• Cardiac catheterization (left ventriculogram)
• A magnetic resonance imaging (MRI) scan of the heart
• A nuclear medicine scan (multiple gated acquisition, or MUGA) of the heart
• A computerized tomography (CT) scan of the heart