Harvard Heart Letter

Ask the doctor: Understanding ejection fraction

Q . Can you explain exactly what "ejection fraction" means? And is there any way to increase it?

A. Ejection fraction refers to the volume of blood that's pumped out of the heart's left ventricle each time it contracts. Contrary to what many people believe, a normal ejection fraction is not 100%. Even a healthy heart pumps out only about half to two-thirds of the volume of blood in the chamber in one heartbeat. So a normal ejection fraction lies somewhere in the range of 55% to 65%.

Damage to the heart's muscle—from a heart attack, heart muscle disease (such as cardiomyopathy), or other causes—can lead to a lower ejection fraction. An ejection fraction of 40% or lower may signal heart failure, a condition in which the weakened heart struggles to circulate blood throughout the body.

For some people with heart failure and a low ejection fraction, medications such as ACE inhibitors and angiotensin-receptor blockers can improve or stabilize the ejection fraction. Exercise can also help by strengthening muscles in the arms and legs. Larger, more efficient muscles are better able to extract oxygen from circulating blood, which can compensate somewhat for the heart's decreased pumping ability. But be sure to check with your doctor before starting an exercise regimen. If possible, find a supervised cardiac rehabilitation program, which is the safest way for people with heart failure to start to exercise.

— Deepak L. Bhatt, MD, MPH
Editor in Chief, Harvard Heart Letter