Guidelines from the European Society of Cardiology define heart failure as a clinical syndrome in which patients present the following key features:

1. Symptoms such as breathlessness at rest or with exercise; fatigue; tiredness; ankle swelling
2. Signs such as tachycardia (rapid heart rate), tachypnoea (rapid breathing), pulmonary rales (crackles heard in the lungs), pleural effusion (excess fluid around the lung), raised jugular venous pressure (raised pressure in the veins in the neck), peripheral oedema (swelling of the feet and ankles), hepatomegaly (abnormal enlargement of the liver)
3. Objective evidence of structural or functional abnormality of the heart at rest.