Heart failure, also called congestive heart failure, is a condition in which the heart can no longer pump enough blood to the rest of the body.

Heart failure is almost always a chronic, long-term condition, although it can sometimes develop suddenly.

The condition may affect the right side, the left side, or both sides of the heart.

• Right-sided heart failure means the right ventricle of the heart loses its pumping function.
• Left-sided heart failure means the heart's ability to pump blood forward from the left side of the heart is decreased. The left side of the heart normally receives blood rich in oxygen from the lungs and pumps it to the remainder of the body.

Heart failure is often classified as either systolic or diastolic.

• Systolic heart failure means that your heart muscle cannot pump, or eject, the blood out of the heart very well.
• Diastolic heart failure means that your heart's pumping chamber does not fill up with blood.

Both of these problems mean the heart is no longer able to pump enough blood out to the rest of your body, especially when you exercise or are active.

As the heart's pumping action is lost, blood may back up in other areas of the body, producing congestion in the lungs, the liver, the gastrointestinal tract, and the arms and legs. As a result, there is a lack of oxygen and nutrition to organs, which damages them and reduces their ability to work properly.

Perhaps the most common cause of heart failure is coronary artery disease, a narrowing of the small blood vessels that supply blood and oxygen to the heart. For information on this condition and its risk factors, see: Coronary artery disease.

Heart failure can also occur when an illness or toxin weakens the heart muscle or changes the heart muscle structure. Such events are called cardiomyopathies. There are many different types of cardiomyopathy. For information, see: Cardiomyopathy

Other heart problems that may cause heart failure are:

• Congenital heart disease
• Heart valve disease
• Some types of abnormal heart rhythms (arrhythmias)

Diseases such as emphysema, severe anemia, hyperthyroidism, or hypothyroidism, may cause or contribute to heart failure