Heart failure is a cardiac condition, that occurs when a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs.

Heart failure should not be confused with cardiac arrest (see Terminology, below). It can cause a large variety of symptoms (chiefly shortness of breath and ankle swelling) but some patients can be completely symptom free. Heart failure is often undiagnosed due to a lack of a universally agreed definition and challenges in definitive diagnosis, particularly in early stage. With appropriate therapy, heart failure can be managed in the majority of patients, but it is a potentially life threatening condition, and progressive disease is associated with an annual mortality of 10%. It is the leading cause of hospitalization in people older than 65.

Terminology

Heart failure is a global term for the physiological state in which cardiac output is insufficient for the body's needs.

This may occur when the cardiac output is low (often termed "congestive heart failure").

In contrast, it may also occur when the body's requirements are increased, and demand outstrips what the heart can provide, (termed "high output cardiac failure") . This can occur in the context of severe anemia, beriberi (vitamin B₁/thiamine deficiency), thyrotoxicosis, Paget's disease, arteriovenous fistulae or arteriovenous malformations.

Fluid overload is a common problem for people with heart failure, but is not synonymous with it. Patients with treated heart failure will often be euvolaemic (a term for normal fluid status), or more rarely, dehydrated.

Doctors use the word "acute" to mean of rapid onset, and "chronic" of long duration. Chronic heart failure is therefore a long term situation, usually with stable treated symptomatology. Acute Heart failure, which should just describe sudden onset HF, is also used to describe exacerbated or decompensated heart failure, referring to episodes in which a patient with known chronic heart failure abruptly develops symptoms.Fact: date=July 2008

There are several terms which are closely related to heart failure, and may be the cause of heart failure, but should not be confused with it:

• Cardiac arrest, and asystole both refer to situtations in which there is no cardiac output at all. Without urgent treatment, these result in sudden death.
• Heart attack refers to a blockage in a coronary (heart) artery resulting in heart muscle damage.
• Cardiomyopathy refers specifically to problems within the heart muscle, and these problems usually result in heart failure. Ischemic cardiomyopathy implies that the cause of muscle damage is coronary artery disease. Dilated cardiomyopathy implies that the muscle damage has resulted in enlargement of the heart. Hypertrophic cardiomyopathy involves enlargement and thickening of the heart muscle.