Definition of Ebstein's anomaly:

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

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

See also:

• Atrial septal defect
• Congenital heart disease

Causes, incidence, and risk factors:

The tricuspid valve is normally made of three parts, called leaflets or flaps. The flaps 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, one or two of the flaps may stick to the heart wall and cannot move. The flaps are often larger than normal. Sometimes two flaps are in the wrong position in the bottom heart chamber.

The defects can cause blood to leak into the wrong areas of the heart. The backup of blood flow can lead to heart swelling and fluid buildup in the lungs or in the liver. Sometimes, blood can't get out of the heart into the lungs and the person may appear blue.

In some cases, patients also have a hole in the wall separating the heart's two upper chambers. 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.