What is congestive heart failure? Congestive heart failure, also called CHF or heart failure, is a serious and complex disease in which the heart muscle has been damaged or has to work too hard because of heart disease and other conditions, such as obesity. Although the heart continues to beat, the damaged heart muscle is too weak to efficiently pump enough oxygen-rich blood to and from the body, resulting in potentially life-threatening congestion in the lungs and other tissues of the body. Congestive heart failure is a common complication of heart attack and other types of heart disease that damage the heart muscle. These diseases include hypertension, heart valve disorders, arrhythmias, and cardiomyopathy. Congestive heart failure can also be caused by anemia. In general, congestive heart failure affects both the left and right sides of the heart, but it can affect one side more than the other, depending on the location and severity of damage. In left-sided CHF, the left side of the heart is damaged and unable to effectively pump blood from the heart to the body. This results in blood backing up into the lungs and increasing blood pressure in the lungs. The increase in pressure causes a buildup of fluid in the lungs, which can lead to a life-threatening condition called acute pulmonary edema. In right-sided CHF, the right side of the heart is damaged and unable to effectively relax to permit blood flowing from the body back into the heart. This results in a backup of blood and an increase in pressure in the veins that carry blood from the body to the heart. In turn, this leads to swelling (edema) of the lower extremities and sometimes of other areas of the body. Acute CHF, in which fluid builds up rapidly in the lungs and causes pulmonary edema, is an immediately life-threatening condition that can quickly lead to respiratory failure, cardiac arrest and death. Immediate emergency treatment best minimizes the risk of these and other serious complications of heart failure. Seek immediate medical care (call 911) if you, or someone you are with, have symptoms of acute congestive heart failure, such as shortness of breath, difficulty breathing, congested cough, and chest pain. If you do not have the above symptoms, but have swelling in the extremities, abdomen or face, seek prompt medical care.