Blood flows from the lungs, where it picks up oxygen, and into the heart through the mitral valve. When it opens, the mitral valve allows blood to flow into the heart's main pumping chamber called the left ventricle. It has two flaps, or leaflets. The mitral valve is highlighted on this illustration of a heart.
Blood flows from the lungs, where it picks up oxygen, and into the heart through the mitral valve.
Surgery may be necessary when the valve opens or closes incompletely. This makes it difficult for the heart to increase the amount of blood that it pumps with exercise, and may produce symptoms of shortness of breath - especially with activity. Since some of the blood leaks backwards, the heart has to pump more blood with each contraction in order to push the same amount of blood forward. This is called volume overload. The heart can compensate for this overload for many months or years, provided that the leakage came on slowly and progressively.