The purpose of the heart is to pump blood to the body in order to nourish it. Heart failure doesn't mean that the heart has stopped working, but that it just isn't able to pump enough blood to meet the needs of the body.
This may happen when the heart muscle itself is weaker than normal or when there is a defect in the heart that prevents blood from getting out into the circulation. When the heart does not circulate blood normally, the kidneys receive less blood and filter less fluid out of the circulation into the urine. The extra fluid in the circulation builds up in the lungs, the liver, around the eyes, and sometimes in the legs. This is called fluid "congestion" and for this reason doctors call this "congestive heart failure".
Older children with congestive heart failure may be tired and have problems keeping up with their friends on the playground, while infants with congestive heart failure usually have symptoms during feeding including sweating, fast breathing and fatigue. In addition, these infants may not gain weight well. Fluid may also build up in the rest of the body, causing swelling of the feet, the legs or around the eyes.
Medicines called diuretics ("water pills"), e.g., furosemide (Lasix), help get rid of the extra fluid by increasing urination. To help the body rid itself of the extra fluid, a low-salt diet may sometimes be necessary. Blood vessel relaxing medications (captopril, enalapril) may sometimes be used to make it easier for the heart to pump. Another medication, digoxin, may help the heart contract with more force.