The , a left and a right, each with two chambers - the atrium and the ventricle. Between the chambers are the which ensure the blood runs only in one direction. There are also situated between the ventricles and the major arteries - the aorta and pulmonary artery - where they have the same function. Failure in a valve in the left side of the heart - the aortic or the - results in left-sided heart failure. This leads to an accumulation of fluids in the lungs, or pulmonary oedema. of the right side of the heart - the pulmonary and tricuspid valve - are rare but can occur as the result of some forms of congenital or long-term left-sided heart failure. Right-sided heart failure is characterised by fluid accumulation in the body, particularly in the legs, abdominal cavity and the liver. can be divided into two categories: narrowed (stenosed) valves and leaking (regurgitant) valves - or a combination of both. | 
