The proportion, fraction, or percentage of blood pumped out of your heart with each beat is called the ejection fraction. A normal heart pumps out a little more than half the heart's volume of blood with each beat. A normal EF is 55 percent or higher. Your doctor can order simple, painless tests such as an echocardiogram that creates a moving picture of your heart using harmless soundwaves, or a nuclear medicine test that shows how well your heart is pumping. If your EF is abnormally low, you may need further tests to see if you have an abnormal heart rhythm.

Click the image to view an animation on ejection fraction

Many people who have survived a heart attack can benefit from an implantable cardiac defibrillator (ICD), a pacemaker-like device that treats ventricular fibrillation (VF), the deadly heart rhythm that causes sudden cardiac arrest (SCA).

Recently, several large clinical studies were conducted to see if ICDs could help prevent or treat sudden cardiac death or sudden cardiac arrest in 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 greater for people with ICDs than for people who received traditional medical care.

Do you know your EF?
If you don't, ask your doctor. It could save your life.