Congestive heart failure is a syndrome in which the heart cannot pump blood adequately. “Heart failure” does not mean that the heart has stopped working; rather, it means that each beat of the heart ejects less blood than the body requires. The most common causes of congestive heart failure are coronary artery disease, heart attack, and high blood pressure.

There are two types of heart failure, systolic and diastolic. Systolic heart failure, which accounts for about 60 percent of cases, occurs when the heart muscle becomes weak. During a normal heartbeat, the ventricles (lower chambers of the heart) eject about 60 percent of the blood that fills them. In a patient with systolic heart failure, the weakened ventricles eject less than 60 percent of the blood that fills them, so each heartbeat provides less blood to the body than it needs. Because the heart muscle becomes weak during systolic failure, the shape of the heart often changes—it looses its normal oval shape and becomes spherical (a process called “remodeling”).

Diastolic heart failure, which accounts for about 40 percent of cases, occurs when the ventricle walls become stiff. Because these stiff walls are less flexible than they are in a healthy heart, the ventricles cannot hold as much blood as normal and the heart requires higher pressure to fill. Even though the stiff ventricles still eject 60 percent of the blood that fills them, there is less blood in them to begin with, so each heartbeat provides less blood to the body than it needs.

Because a failing heart cannot eject blood as fast as it enters, blood tends to build up, or congest, in vessels near the heart. When blood flow slows, the fluid part of blood (the part without blood cells) tends to leak through vessel walls and enter bodily tissues. This fluid buildup in tissues, called edema, occurs often in the lungs, which is why a common symptom in patients with heart failure is difficulty breathing. Patients with heart failure also frequently suffer from edema in the ankles and feet, and they have difficulty exercising.

The primary treatment for congestive heart failure is drug therapy. Although it was previously believed that the progression of heart failure could only be slowed, not stopped, recent pharmaceutical advances have enabled doctors to stop and even reverse heart failure in some patients. There are also devices that can be surgically implanted to assist a failing heart.

Congestive heart failure can be caused by many diseases that affect the heart. Coronary artery disease is a common cause. When coronary blood flow is impeded, the heart muscle cannot function properly. If the artery clogs completely, a myocardial infarction (heart attack) occurs. This kills heart muscle, which impairs the heart’s ability to pump and can cause systolic heart failure. Other causes of systolic failure include high blood pressure, inflammation of the heart muscle (myocarditis), heart-valve disorders, and excessive alcohol intake.

Diastolic heart failure usually results from high blood pressure combined with a natural stiffening of the heart that occurs with age.

Diabetes can cause both types of heart failure.

In the United States, coronary artery disease, high blood pressure, diabetes, and old age are the primary risk factors for both types of heart failure. Men and women are equally likely to get systolic heart failure, although men tend to develop the disorder about 10 years before women. For unknown reasons, women are more likely than men to develop diastolic heart failure.

Heart failure is first diagnosed with a physical examination. Possible findings are a weak or rapid pulse, difficulty breathing, abnormal heart sounds, fluid sounds in the lungs, and edema in the legs and abdomen. An electrocardiogram (ECG) can reveal abnormal heart rhythms and the existence of a prior heart attack. The most important diagnostic tool is an echocardiogram, which can show whether the heart is pumping normally, whether the valves are functioning normally, and how much blood is ejected with each contraction (a low figure may indicate systolic failure).

Patients with certain types of heart failure may experience a sudden buildup of fluid in the lungs, leading to a life-threatening emergency (acute pulmonary edema). The fluid buildup can also trigger spasms in the airway (cardiac asthma). Because blood moves slowly in heart-failure patients, clots may form. These clots can cut off circulation to a limb or cause a stroke. All patients with heart failure are at risk of sudden death from heart-rhythm abnormalities, which can cause cardiac arrest.

Patients with congestive heart failure should aggressively treat the underlying disease that has caused their heart failure, if it can be discovered. They should eat a low-salt diet (weighing themselves to gauge water buildup in tissues), control obesity, and abstain from smoking and excessive alcohol drinking. Patients should adhere to medication schedules rigorously.