Congestive heart failure, or CHF, refers to the failure of the heart to perform its main function: to pump blood throughout the body. It occurs when the flow of blood, or cardiac output, from the heart decreases, or fluids back up or "congest" within the heart, or both. Insufficient cardiac output can only be considered congestive heart failure if the heart is receiving enough blood in the first place. Congestive heart failure is the eventual result of any number of numerous cardiac conditions that impede the heart's ability to pump blood. Therefore, it is a symptom of underlying disorders which require treatment.

The list of these associated disorders is lengthy and some of them may be present without a patient's knowledge. Some of the most common are high blood pressure, or hypertension, which forces the heart to pump against increased resistance to meet demand; ischemia, a condition stemming from coronary artery disease (CAD) in which the heart muscle receives insufficient oxygen and is damaged as a result; and valvular heart disease, in which some of the heart's valves become either narrowed or infected, or leak pumped blood back into the heart. Abnormal heart rhythms, or arrhythmia, as well as a heartbeat that is either too slow or too fast, can all reduce cardiac output. In individuals with an overactive thyroid gland or anemia, the heart works overtime to provide the body's tissues with enough oxygen and over time can lead to congestive heart failure. Furthermore, any diseases of the heart muscle itself, the surrounding pericardium, as well as birth defects of the heart, can result in congestive heart failure.

Because congestive heart failure stems from any number of these problems, it typically develops over time. Symptoms include weakness or fatigue, shortness of breath, reduced stamina, rapid heartbeat, and swelling of the ankles, legs, feet, or abdomen.

Congestive heart failure is almost always chronic; however, there are treatments available. The most common is medication. Categories of these drugs include ACE inhibitors that widen blood vessels to improve blood flow, beta blockers to slow the heart, and diuretics to prevent the body from retaining fluids. Some of the conditions that led to congestive heart failure may require surgery, such as a coronary bypass to treat narrowed arteries. There are also implantable devices that can help. Mechanisms such as implantable cardioverter-defibrillators or bioventricular pacemakers use electrical impulses to maintain a regular heartbeat. There are also mechanical heart pumps that can be implanted to help maintain healthy blood flow. Severe cases sometimes require heart transplants.

The best treatment however, is prevention. Lifestyle factors that place stress on an individual\'s heart include a diet excessive in salt and/or cholesterol, smoking, being overweight, or not taking prescribed medication. Addressing such risk factors early can prevent congestive heart failure entirely.