While an ejection fraction (EF) is a tool to diagnose systolic heart failure, or heart failure that occurs during the pumping phase of the heartbeat, it is possible for a person to have heart failure without having an abnormal ejection fraction. There are two phases to the heart’s pumping motion. First is the filling phase (diastole) in which the heart chamber fills with blood. Second is the emptying phase (systole) in which the blood is pumped out of the chamber to the body. An ejection fraction is a measurement of the amount of blood pumped out during this second, emptying stage.

Heart failure may be caused by problems with the heart’s emptying phase, its filling phase or with both phases. Therefore, a person whose heart failure is caused by a problem with the filling phase (diastolic heart failure) could have a normal ejection fraction. 

Conditions that cause the heart muscle to stiffen may also cause heart failure without producing an abnormal ejection fraction. These conditions include cardiomyopathies in which the heart muscle becomes abnormally enlarged, thickened and/or stiffened. Other causes of heart stiffening include invasion of the heart muscle by foreign substances or fibrous tissue problems.

Finally, the ejection fraction is a measurement of the amount of blood pumped from the heart with each heartbeat. However, the number does not reflect the direction in which the blood is being pumped. If the valves are abnormal due to some form of valvular heart disease, blood may be flowing in the wrong direction. In this case, a patient might have a normal ejection fraction but an unhealthy heart. This can lead to heart failure with a normal ejection fraction (e.g., mitral insufficiency).

In the same way that blood pressure and heart rate typically increase during physical activity, a healthy person’s ejection fraction tends to increase about 5 percent while the person is exercising. When this healthy increase in EF during exercise does not occur, it indicates a heart function problem. Therefore a patient with a normal ejection fraction that fails to rise with exercise could be diagnosed with heart failure or cardiomyopathy. Such a problem may be diagnosed by a stress echocardiogram, in which the ejection fraction can be measured during both rest and exercise.

An ejection fraction is just one of many tools the physician uses to diagnose heart problems. One of its significant advantages is that it is easier for physicians to obtain this number through a simple, painless echocardiogram than to perform more extensive heart function tests. Consequently, the ejection fraction serves as a good baseline for monitoring the heart’s function over time.