Ebstein's anomaly is a congenital downward displacement of the tricuspid valve (located between the upper and lower chambers on the right side of the heart) into the right bottom chamber of the heart (or right ventricle). It is usually associated with an atrial septal defect (see below) and can be associated with heart failure and rhythm problems to varying degrees.
People with Ebstein's anomaly, before and after treatment, are at risk for getting an infection within the heart valve (endocarditis). To help prevent this, they'll need to take antibiotics before certain dental and surgical procedures.