Ebstein's Anomaly

Abnormalities Related to Ebstein's Anomaly

Summary of Ebstein's Anomaly

• Downward displacement of the tricuspid valve into the right ventricle with variable malformation of the valve and resultant leaking of blood backwards into the right atrium (tricuspid regurgitation)
• Enlarged right heart chambers
• Atrial septal defect (present in 50 percent of patients)
• Irregular heart rhythms, particularly atrial fibrillation

Downward displacement of the tricuspid valve into the right ventricle

The tricuspid valve separates the top right heart chamber (right atrium) from the bottom chamber (right ventricle). In Ebstein's anomaly, the tricuspid valve is displaced downwards into the right ventricle so that a portion of the right ventricle becomes part of the right atrium (atrialized). The right atrium, therefore, is larger than usual and the functional right ventricle is smaller than normal. The right ventricle is the pumping chamber of the side of the heart which propels blood to the lungs.

In addition to the displacement downwards, the tricuspid valve is usually malformed. Under normal circumstances, the three leaflets or "flaps" of the valve allow only forward flow of blood through the right side of the heart. If the leaflets are malformed or absent, then blood may leak backwards (regurgitation) into the right atrium.

Often in Ebstein's anomaly the leaflets are so malformed that they may be "tethered" to the wall of the right ventricle so that a significant amount of blood leaks back into the right atrium. One leaflet (the anterior leaflet) is often enlarged to compensate for the malformation of the other two leaflets.

The degree of downward displacement and malformation of the tricuspid valve is variable. In some patients, the valve is only mildly abnormal.

In our clinic, the oldest patient with Ebstein's anomaly is 82 years old and has not yet required surgery. In other patients, however, the valve may be very malformed and very displaced and may leak severely. This may even require surgery early in life.

With greater malformation and leakage of the tricuspid valve, the right atrium enlarges as it receives a greater blood volume; and the right ventricle will also dilate as it tries to cope with the leaky valve and still push blood forward to the lungs. Thus the right-sided chambers enlarge; and as they do so, they weaken.

Atrial septal defect

The most common defect associated with Ebstein's anomaly is an atrial septal defect (ASD).

An ASD can allow a blood clot from the veins (e.g., in the leg if you get phlebitis) to pass into the general circulation and cause a stroke. This is somewhat more common with Ebstein's anomaly than when an ASD occurs alone, since there is often a degree of right-to-left shunt across the ASD.

Heart rhythm disturbances

In a normal heart, a special group of cells in the right atrium generates electrical impulses. It is the heart's own "pacemaker" and sends impulses around the heart via special electrical conduction. This makes the heart beat orderly and efficiently.

Approximately 25 percent of patients with Ebstein's anomaly have an additional pathway: a so-called accessory pathway which can bypass the normal impulse circuit and cause fast and irregular heart rhythm (arrhythmias).

These rhythms can reduce heart performance particularly when the tricuspid valve is leaking severely. One rhythm disturbance is called atrial fibrillation and may cause a rapid heart rate and marked shortness of breath or even fainting.