Ebstein's Anomaly is a rare defect, accounting for less than 1 percent of all congenital heart defects. The principal aberration occurring with Ebstein's Anomaly is a malformation of the tricuspid valve, which is located between the right atrium and right ventricle. Two of the three leaflets of the valve (the septal leaflet and the posterior leaflet) are displaced downward into the right ventricular cavity. These valve leaflets vary from mildly deformed to severely deformed. The third leaflet (the anterior leaflet) is not displaced but is typically large and redundant, often described as "sail-like". The portion of the right ventricle that sits above the displaced leaflets is usually thinner than normal and may be referred to as the atrialized portion of the right ventricle. A hole between the upper chambers of the heart, either an atrial septal defect or a patent foramen ovale, is virtually always present in association with Ebstein's anomaly. In some patients with this malformation, the pulmonary valve is also abnormal, either abnormally tight (pulmonary valve stenosis) or entirely closed (pulmonary valve atresia).
Most commonly, the deformed tricuspid valve has a tendency to leak, thus, as the right ventricle contracts some blood flows backwards from the right ventricle to the right atrium. Because of this backwards leakage of blood, a reduced volume of blood enters the right ventricle to be ejected to the lungs. The right atrium, which receives this leaking blood, is usually quite enlarged. Some of the blue blood from the right atrium may pass across the hole in the atrial septum into the left atrium. This blue blood then goes directly out to the body, which may be recognized as cyanosis in the patient. This is frequently present in newborns with Ebstein's anomaly and usually improves over the first weeks of life.
Infrequently, the deformed tricuspid valve forms an imperforate membrane. In this setting, rather than leaking, the tricuspid valve blocks blood from advancing into the right ventricle and out to the lungs.
In patients where the degree of valve deformity is mild and no symptoms are present, no intervention may be required other than prescribing antibiotics prior to dental or surgical procedures to prevent bacterial endocarditis. In patients with more severe involvement, cyanosis, shortness of breath, exercise intolerance and/or significant heart enlargement are often present and surgical intervention is warranted. The surgery usually consists of repairing or replacing the abnormal tricuspid valve and closing the hole between the atria.
View an animated heart with Ebstein's Anomaly