Ebstein's anomaly is a rare heart defect in which parts of the tricuspid valve are abnormal. The tricuspid valve separates the right lower heart chamber (right ventricle) from the right upper heart chamber (right atrium).

The condition is congenital, which means it is present from birth.

See also:

• Atrial septal defect
• Congenital heart disease

The tricuspid valve is normally made of three parts, called leaflets or flaps. The leaflets open to allow blood to move from the right atrium (top chamber) to the right ventricle (bottom chamber) while the heart relaxes. They close to prevent blood from moving from the right ventricle to the right atrium while the heart pumps.

In persons with Ebstein's anomaly, the leaflets are unusually deep in the right ventricle. The leaflets are often larger than normal. The defect usually causes the valve to work poorly, and blood may go the wrong way back into the right atrium. The backup of blood flow can lead to heart swelling and fluid buildup in the lungs or liver. Sometimes, blood can't get out of the heart into the lungs and the person may appear blue.

In most cases, patients also have a hole in the wall separating the heart's two upper chambers and blood flow across this hole may cause oxygen-poor blood to go to the body. There may be narrowing of the valve that leads to the lungs (pulmonary valve).

Ebstein's anomaly occurs as a baby develops in the womb. The exact cause is unknown, although the use of certain drugs (such as lithium or benzodiazepines) during pregnancy may play a role. The condition is rare. It is more common in white people.