Heart failure is the inability of the heart to provide sufficient oxygen to the tissues. This results in chemical messenges sent to the heart and vessels that improve blood flow in the near term, but may actually worsen the problem over time.

Congestive heart failure (CHF) is a chronic condition that results from overload of the heart with blood and backup of blood into the lungs and/or body. This often causes leakage into the tissues, or leakage into or around the lungs.

CHF is a sign of an underlying problem of overload of the heart causing backup of blood into the circulation. Maybe there is a valve problem, or a congenital "hole in the heart" causing inability of the heart to pump properly. Maybe the heart muscle itself is weakened or damaged by some cause. There are multiple causes in humans and horses. The point is that CHF is often the unintended result of the body trying to simply get blood and oxygen to its tissues.

An example of a reversible cause might be an arrhythmia that is causing poor heart performance and CHF. Once the arrhthmia is effectively treated, the heart failure improves. On the other hand, a heart tumor or aneurysm is unlikely to be treated and so the CHF can only be managed and is expected to worsen over time.

Signs of congestive heart failure in horses include swelling of the legs and abdomen, rapid shallow breathing, high heart rate, jugular pulse, among many others.

Diagnosis of heart failure is through clinical examination and ultrasound (echocardiography) that shows the heart's inability to pump sufficiently and evidence of blood backed up from it.

Treatment is, first and foremost, the treatment or management of the underlying condition causing the heart's poor performance. Beyond that, drugs can be given that reduce total circulating volume (diuretics) or increase the heart's performance in various ways.