With each heartbeat, the heart contracts (or squeezes) and relaxes. Every contraction pushes blood out of the two pumping chambers (ventricles). When when heart relaxes, the ventricles refill with blood. The ejection fraction (EF) refers to the amount, or percentage, of blood that is pumped (or ejected) out of the ventricles with each contraction. This percentage, or EF number, helps your health care provider determine if you have heart failure or other types of heart disease.
A normal heart pumps just over half the heart's volume of blood with each beat – a normal EF is 50 to 75 percent.
EF is typically measured by a simple, painless test called an echocardiogram. A special imaging machine uses sound waves to create a videotaped image of the heart, showing the four chambers of the heart, the valves and how well the heart is pumping.
Most often, the left ventricle, the heart’s main pumping chamber, is measured during an echocardiogram. A normal left ventricular ejection fraction (LVEF) is 55 to 75 percent. Other tests used to measure EF include cardiac catheterization, magnetic resonance imaging (MRI), computed tomography (CT), and nuclear medicine scans.
Ejection Fraction Numbers:
|50-75%||Heart's pumping ability is Normal|
|36-49%||Heart's pumping ability is Below Normal|
|35% and Below||Heart's pumping ability is Low|
A low EF number is an early sign of heart failure. This is a condition where the heart does not pump enough blood to the rest of the body. With treatment, many people live well with heart failure. If you have a low EF number, it is important that you recognize the signs of heart failure, which may include:
A low EF can also cause a very rapid heartbeat, which can make your heart pump ineffectively. If you have heart disease, your doctor will check your EF periodically, closely monitoring your condition.
Depending on your EF number, your doctor may make recommendations to help you improve your EF. In some cases, medication may be prescribed. There are also other things you can do to improve how well your heart pumps.
Many people who have a reduced EF can benefit from a medical device called an implantable cardiac defibrillator (ICD). An ICD is a pacemaker-like device that treats ventricular fibrillation (VF), the deadly heart rhythm that causes sudden cardiac arrest (SCA).
Several large clinical studies have been conducted in recent years to see if ICDs could help prevent SCA in those people whose heart muscle, and its pumping ability, is damaged by a heart attack. People in the studies had an ejection fraction (EF) of 40 or below. In these studies, survival rates were significantly higher for people with ICDs compared to those who received traditional medical care.