Ejection fraction is a measurement of the percentage of blood leaving your heart each time it squeezes (contracts). It is just one of many tests your doctor may use to determine how your heart works.

The heart contracts and relaxes. When your heart contracts, it pumps out (ejects) blood from the two lower chambers (ventricles). When your heart relaxes, the ventricles refill with blood. No matter how forceful the contraction, the heart can never pump all 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.

The ejection fraction is usually measured only in the left ventricle. The left ventricle is the heart's main pumping chamber. It pumps oxygen-rich blood up into your body's main artery (aorta) to the rest of the body.

• A normal ejection fraction is about 50% to 75%, according to the American Heart Association.
• A borderline ejection fraction can range between 41% and 50%.

Even if you have a normal ejection fraction, your overall heart function may not be normal. Talk with your doctor if you have concerns about your heart.

Some things that may cause a reduced ejection fraction are:

• Weakness of the heart muscle, such as cardiomyopathy
• Heart attack that damaged the heart muscle
• Heart valve problems
• Long-term, uncontrolled high blood pressure

Ejection fraction can be measured with imaging tests, including:

• Echocardiogram. This is the most common test used to measure ejection fraction. During an echocardiogram, sound waves are used to produce images of your heart and the blood pumping through your heart.
• Cardiac catheterization. During cardiac catheterization, a thin, plastic tube (catheter) is inserted into a blood vessel in your arm or leg and then gently guided to your heart. Images taken during catheterization can measure the ejection fraction of your heart.
• Magnetic resonance imaging (MRI). An MRI uses magnetic field and radio waves to create cross-sectional images of specific parts of your body. When an MRI is used to study the heart, it's called a cardiovascular MRI.
• Computerized tomography (CT). A CT scan uses X-rays to create cross-sectional images of specific parts of your body. When a CT scan is used to study the heart, it's known as a cardiac CT.
• Nuclear medicine scan. During a nuclear scan, trace amounts of radioactive material are injected into your bloodstream. Special cameras then detect the radioactive material in your blood as it flows through your heart and lungs.