AV valves are the atrioventricular valves which prevent the back flow of blood from the ventricles (lower chambers of the heart) when they contract. If the AV valves are not competent, the blood will flow back into the atria (upper thin walled chambers of the heart) when the ventricles contract. The AV valve between the left atrium and the left ventricle has two cusps and is known as the mitral valve. The AV valve separating the right atrium and the right ventricle is known as the tricuspid valve a it has three cusps. The mitral valve has been named so because it has a resemblance the the bishop’s official head ware known as the mitre. The functioning of the AV valves are aided by the papillary muscles which hold back the cusps of the valve back into the ventricle without billowing back into the atria during the contraction of the ventricles. The AV valves are attached to the papillary muscles by thread like structures known as chordae tendinae. Rupture of chordae tendinae or dysfunction of the papillary muscles can cause leakage of the AV valves.