Mitral valve

The mitral valve (bicuspid valve, left atrioventricular valve) is the only heart valve with two leaflets (bi- from the Latin for double, and mitral- from the Latin for mitre-shaped). It lies between the left atrium and the left ventricle. The mitral valve is not to be confused with the congenital condition of a bicuspid aortic valve. The mitral valve and the tricuspid valve are known collectively as the atrioventricular valves because they lie between the atria and the ventricles of the heart and control the flow of blood.

During diastole, a normally-functioning mitral valve opens as a result of increased pressure from the left atrium as it fills with blood (preloading). As atrial pressure increases above that of the left ventricle, the mitral valve opens. Opening facilitates the passive flow of blood into the left ventricle. Diastole ends with atrial contraction, which ejects the final 20% of blood that is transferred from the left atrium to the left ventricle. This amount of blood is known as end diastolic volume (EDV). The mitral valve closes at the end of atrial contraction to prevent a reversal of blood flow.