Mitral valve atresia is a rare congenital (present at birth) defect of the heart’s mitral valve. The mitral valve connects the heart’s left atrium (upper chamber) and left ventricle (lower chamber). In mitral valve atresia blood from the left atrium does not flow to the left ventricle, causing the left ventricle to become underdeveloped, while the body's blood is not properly oxygenated. Mitral valve atresia is often associated with other congenital heart defects, such as transposition of the great arteries, patent ductus arteriosus, and coarctation of the aorta, among others.

Symptoms of mitral valve atresia depend on its severity and any associated congenital heart defects and may include difficulty breathing; rapid breathing; bluish or gray skin, lips, or nails (cyanosis); pale, cool, or clammy skin; poor peripheral pulses; rapid heart rate; failure to thrive; and congestive heart failure.

Treatment for mitral valve atresia may include oxygen, mechanical ventilation, diuretics, vasopressors, antibiotics, shunts, and staged corrective surgeries.