DEAR DOCTOR K: My husband has heart failure. His doctor often uses the term “ejection fraction.” Can you explain what this means?
DEAR READER: Before I explain what an ejection fraction is, let’s say what “heart failure” is, and isn’t. Many of my patients think that heart failure means a heart that stops pumping completely. But that’s not heart failure; that’s sudden death.
Heart failure can lead to a range of symptoms, from fatigue and shortness of breath to a buildup of fluid in the body. With heart failure, the heart is still pumping — it’s just not pumping effectively enough to completely do the job the rest of the body needs it to do.
What is that job? Every cell in the body needs a constant supply of nutrition (sugar, fat and oxygen) and needs to eliminate waste. In that sense, every cell in our body is just like us.
The heart pumps nutrition-rich blood out to the body, and as the blood delivers the nutrition, it picks up the waste. The heart also pumps blood through the lungs to receive a fresh supply of oxygen. The heart has four chambers. Two chambers, called the atria, receive blood. Two larger chambers, the ventricles, pump blood out to the lungs and the rest of the body.
That’s how a healthy heart works. However, disease (particularly high blood pressure and clogged arteries), injury, and years of wear and tear can take their toll. Heart failure is usually a gradual decline in the heart’s ability to pump. Sometimes heart failure begins suddenly, such as when someone has a heart attack that kills a part of the heart muscle.
Whether it begins gradually or suddenly, in many cases of heart failure the muscle tissue in the heart’s left ventricle becomes thin and weak. It can’t contract strongly enough to send sufficient blood throughout the body.
Which brings us to ejection fraction. A low ejection fraction is a defining characteristic of a common type of heart failure called systolic heart failure. An ejection fraction is a measurement of the volume of blood pumped out of the left ventricle each time the heart contracts, expressed as a percentage of the total amount of blood expelled. (I’ve put an illustration of ejection fraction on my website, AskDoctorK.com.)
Even a healthy heart doesn’t expel its full contents at every beat. A normal ejection fraction lies in the range of 55 percent to 65 percent.
A doctor can measure ejection fraction with an echocardiogram. This test uses sound waves to create a moving picture of the heart. The resulting video can determine ejection fraction.
The ability to measure the ejection fraction has helped doctors more precisely determine the effectiveness of treatment, and the best type of treatment. It also helped doctors to discover a second type of heart failure that we now recognize as another common type: diastolic heart failure. But that’s a topic for another column.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.