The mitral valve is located between the left atrium (upper heart chamber that receives oxygenated blood from the lungs) and the left ventricle (the heart’s main pumping chamber).
Normally, blood flows one way through the valve's two flaps (leaflets), which open and close with each heartbeat. In mitral valve stenosis, the opening is narrowed (stenotic), usually due to scarring from childhood rheumatic fever – a condition that is related to strep throat. Less common causes for mitral valve stenosis are tumors, blood clots, age-related calcium deposits and birth defects. When the mitral valve opening narrows, it prevents blood from flowing into the left ventricle. Sometimes these stenotic valves also leak (mitral valve regurgitation).