Mitral valve: inlet valve in the left heart.
The mitral valve allows blood to pass from the left atrium to the left ventricle. Because of its location, it is considered one of the atrioventricular valves, along with the tricuspid valve. Like the other three heart valves, it consists of a double layer of the heart’s inner lining (endocardium) and is a so-called leaflet valve. In fact, it has two “leaflets”, one anterior and one posterior, which is why it is also called a bicuspid valve (Latin: bi-=two, cuspis=spike, tip).
The papillary muscles of the mitral valve
Tendinous cords attach to the edges of the leaflets, connecting them to the papillary muscles. These muscles are small protrusions of the ventricular muscle into the ventricle. They prevent the free-hanging leaflets of the mitral valve from recoiling into the atrium due to the resulting pressure when the ventricle contracts (the muscle contracts in systole).
Mitral valve function
Common mitral valve problems
In mitral stenosis, the mitral valve is narrowed, causing the ventricle to not fill properly during diastole. In most cases, mitral valve stenosis is due to valvular inflammation caused by rheumatic fever. Only rarely is it congenital or calcified purely due to wear and aging.
In mitral regurgitation, the mitral valve does not close tightly, allowing blood to return from the ventricle to the atrium during systole. This causes a certain amount of blood to “shuttle” back and forth between the atrium and the ventricle. Causes of mitral valve regurgitation include bacterial endocarditis (heart valve inflammation), torn papillary muscles and tendons (e.g., from chest wall injury, surgery, or a heart attack), or rheumatic diseases.
If one or both valve leaflets bulge into the atrium during systole, physicians refer to this as mitral valve prolapse. The valve may still be tight. However, more severe mitral valve prolapse also leads to valve insufficiency. Prolapse is sometimes congenital, but the cause is often unclear. It tends to affect women with connective tissue weakness more often. Sometimes the physician hears one or more “systolic clicks” with the stethoscope during prolapse of the mitral valve.
