Atrioventricular valves are the two valves that control blood flow from the atria (the heart’s upper chambers) into the ventricles (the lower chambers), preventing backflow. The mitral valve lies between the left atrium and left ventricle, and the tricuspid valve lies between the right atrium and right ventricle. Together with the arterial (semilunar) valves at the ventricular outflow tracts, the atrioventricular valves ensure that blood flows in one direction through the heart.
Both atrioventricular valves open passively when ventricular pressure falls below atrial pressure during diastole, allowing blood to fill the ventricles. They close at the start of systole as the ventricles contract, preventing backflow into the atria. The characteristic ‘lub’ of the normal heart sound (S1) is produced by closure of the mitral and tricuspid valves at the onset of ventricular systole. The valves are supported by fibrous cords called chordae tendineae and papillary muscles attached to the ventricular wall, which prevent the valve leaflets from prolapsing backwards into the atria during the high pressures of systole.
Disease of the atrioventricular valves takes two main forms. Stenosis (narrowing) restricts forward flow through the valve and increases the pressure the atrium must generate to push blood forward. Regurgitation (leaking) allows blood to flow back into the atrium during systole, reducing the volume of blood that reaches the body with each beat. Both forms place a progressively increasing burden on the heart and, if severe and untreated, can lead to heart failure and arrhythmias.
For further detail on individual atrioventricular valve conditions, see the entries for Mitral Valve Regurgitation and the related information on mitral and tricuspid valve disease.
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