First described in 1866, Ebstein’s anomaly is an uncommon heart condition that is present at birth (a congenital heart condition), in which the right side of the heart, especially the tricuspid valve, is abnormally formed. There are several characteristics that may be associated with Ebstein's anomaly:

• A tricuspid valve that droops into the right lower chamber (ventricle) so the valve does not function properly.
  
  
• An abnormally formed tricuspid valve that is too firmly attached to the ventricle wall and does not function properly.
  
  
• The right ventricle is atrialized, or unusually thin and enlarged in the region of the tricuspid valve and does not pump adequately. At the same time, the right atrium and tricuspid valve may be enlarged.
  
  
• The lower portion right ventricle may be unusually small, and there is an outflow obstruction that reduces the amount of blood that can flow from the chamber into the pulmonary arteries, which carry blood to the lungs.

These conditions may exist in various degrees among patients with Ebstein's anomaly. Their severity depends on the severity of symptoms and the need for treatment. Ebstein's anomaly is the most important congenital cause of tricuspid regurgitation, which occurs when oxygen-poor blood flows backward from the right ventricle into the right atrium. In very severe cases, the right ventricle is essentially non-functioning and greatly enlarged, which compromises the left ventricle also. This condition is a medical emergency that must be dealt with immediately after birth. In less severe cases, symptoms may not be apparent for many years and intervention is based on the severity of symptoms.

In addition to the leaky tricuspid valve, patients with Ebstein’s anomaly also tend to have associated heart defects, including a patent foramen ovale or atrial septal defect (ASD). The ASD is the more serious of the two. It is a hole between the left and right atria that allows oxygen-poor blood from the right atrium to mix with oxygen-rich blood in the left atrium. These two types of blood should always remain separate.

Other heart defects that are associated with Ebstein’s anomaly include a ventricular septal defect, patent ductus arteriosus, coarctation of the aorta or left ventricular cardiomyopathy.

Ebstein’s anomaly causes the heart to work harder to meet the body’s demand for oxygen-rich blood. As a result of the additional burden placed on the heart, any of the following complications could occur:

Ebstein’s anomaly is a rare condition, occurring in about 1 in 50,000 to 1 in 100,000 people. Males and females are equally affected, with the disease showing higher prevalence in whites. It is not believed that Ebstein’s is a genetic (and therefore inherited) disease. Studies show that most cases occur randomly, although a few cases have occurred within families.