A normal ejection fraction is 55 percent, according to Mayo Clinic. An ejection fraction of 50 percent or below is considered reduced and usually indicates some degree of damage to the heart. Doctors differ in their interpretations of ejection fractions in the 50 to 55 percent range.
The ejection fraction is a measure of the amount of blood that leaves the heart with each heartbeat, explains Mayo Clinic. Also called the LV-ejection fraction, it typically is measured only in the left ventricle, which is largely responsible for the pumping action of the heart. Weakness of the heart muscle, or dilated cardiomyopathy, often causes the ejection fraction to decrease. Other causes include damage to the heart muscle due to a prior heart attack, prolonged high blood pressure or damaged heart valves.