Acute heart failure is a rapid weakening of the heart’s ability to supply blood to the body Typical symptoms Breathlessness Leg or ankle swelling Extreme fatigue Often a life-threatening medical emergency Underlying problem(s) with the heart’s structure or function, e.g. Enlarged ventricles Thickened ventricular muscle Stiffened ventricle walls Poorly functioning valves Relaxation Contraction Ventricular muscle Right atrium Right ventricle Left atrium Left ventricle Aorta Notes Very simply, heart failure occurs when the heart is no longer able to pump blood properly. Usually, people with heart failure are breathless. They may have leg swelling or ankle swelling and they often feel tired. At times, heart failure can be a life-threatening medical emergency and patients need to be admitted to hospital for urgent care. Nearly anything that can damage the heart can lead to heart failure, whether it affects the ventricles (the main pumping chambers), the valves or the heart rhythm.