Definition of Heart failure:

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

Causes, incidence, and risk factors:

Heart failure is a long-term (chronic) condition, but it can sometimes develop suddenly.

The condition may affect only the right side or only the left side of the heart. These are called right-sided heart failure or left-sided heart failure. More often, both sides of the heart are involved.

Heart failure is present when:

• Your heart muscle cannot pump (eject) the blood out of the heart very well. This is called systolic heart failure.
• Your heart muscles are stiff and do not fill up with blood easily. This is called diastolic heart failure.

Both of these problems mean the heart is no longer able to pump enough oxygen-rich 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. Fluid builds up in the lungs, liver, gastrointestinal tract, and the arms and legs. This is called congestive heart failure.

The most common cause of heart failure is coronary artery disease (CAD), 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: Heart disease - risk factors

Heart failure can also occur when an infection weakens the heart muscle. This condition is called cardiomyopathy. For more information, see: Cardiomyopathy

Other heart problems that may cause heart failure are:

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

Other diseases that can cause or contribute to heart failure:

• Emphysema
• Overactive thyroid
• Severe anemia
• Underactive thyroid