What Is Heart Failure?

Medically Reviewed

Heart failure is a chronic condition caused by a weakening of the heart’s ability to pump blood. About 825,000 new cases are diagnosed each year in the U.S. The most common cause of heart failure is heart damage because of coronary heart disease or high blood pressure.

Less often, heart failure is caused by heart valve abnormalities or infection of the heart valves or heart muscle. Sometimes the cause cannot be pinpointed.

Symptoms of heart failure

If you have heart failure, you may experience fatigue, shortness of breath, fluid retention, and excessive urination at night.

Initial symptoms are mild—feeling overly tired after physical exertion, for example—but eventually even slight activity becomes exhausting. As fluid accumulates in the lower extremities, swelling of the feet, ankles, legs and, sometimes, the abdomen may occur.

Fluid may also settle in the lungs, particularly when you are lying down, which can cause extreme shortness of breath that may awaken you at night. Severe shortness of breath, accompanied by wheezing, coughing, and blood-tinged phlegm, is a sign of pulmonary edema (a buildup of fluid in the lungs) that requires immediate medical treatment. Older individuals with heart failure may also experience lightheadedness or confusion.

Heart failure classifications

Your doctor may use the following system to classify the severity of your heart failure:

• Class I: No symptoms and no limitation in ordinary physical activity

• Class II: Mild symptoms and slight limitation in ordinary physical activity; comfortable at rest

• Class III: Marked limitation of ordinary physical activity; comfortable only at rest

• Class IV: Discomfort occurs with any physical activity, and symptoms of heart failure may occur at rest.

Diagnosis of heart failure

There is no specific test to diagnose heart failure. Your doctor will begin with a medical history and physical examination, looking for the characteristic symptoms—swollen ankles, shortness of breath, fatigue, and weight gain associated with fluid buildup.

The doctor will use a stethoscope to listen for abnormal heart sounds that arise from fluid accumulation in the lungs.

In addition, urine and blood tests may be performed to measure B-type natriuretic peptide (BNP). Blood levels of BNP are increased in people with heart failure.

An ECG and an exercise stress test may be performed, as well as an echocardiogram to obtain images of the heart’s function.