Ebstein’s anomaly is a congenital heart defect which means that part of the heart has not formed properly during pregnancy. To understand exactly what this condition is it is useful to first examine how a ‘normal’ heart works.

The heart is formed with four chambers, the top two being the right atrium and the left atrium. The two chambers below are the ventricles which pump the blood. The atria (top right and top left) and the ventricles are separated by “one way” valves whose main job is to keep the blood flowing through the heart in the right direction. Blood low in oxygen returns from the body and heads to the heart through the superior and inferior vena cava.  It enters the heart via the right atrium, on through the tricuspid valve and into the right ventricle.  As the ventricle contracts, the tricuspid valve is automatically closed forcing blood to flow out of the heart via the pulmopnary artery and on to the lungs.  Similarly, oxygenated blood retruns to the heart through the pulmonary veins into the left atrium.  It then passes through the mitral valve and on into the left ventricle.  Again, as the left ventricle contracts, the mitral valve is closed forcing blood to be pumped out of the heart through the aorta to the head and around the body.  This cycle is repeated millions of times during a normal lifetime.

The Structure of an Ebstein’s Heart

In hearts with Ebstein’s anomaly the tricuspid valve droops much further down into the right ventricle than in a heart without this condition, indeed it may be partially attached to the wall of the heart. Because of this, a part of what would be the right ventricle becomes part of the right atrium (it is atrialized), so the right atrium is larger than usual and the right ventricle is smaller than usual, meaning that the right ventricle doesn’t work as well as it should.

As well as the unsual positioning of the tricuspid valve there are further problems to contend with, because the three ‘leaflets’ which make up the tricuspid valve are not formed properly blood can ‘leak’ back (regurgitating) into the right atrium. In severe cases of Ebstein’s the leaflets can be attached to the wall of the right side of the heart. This can lead to severe leakage and a significant reduction in pumping capacity.

A normal heart and a heart with Ebsteins. Note how the tricuspid valve between the right atrium (RA) and the right ventricle (RV) droops down. Also note the gap between the chambers of the right atrium (RA) and left artium (LA) – this is the Atrial Septal Defect which is present in 50% of those with Ebstein's. (Reproduced courtesy of The Mayo Clinic)

The actual location of the valve, and how badly it is formed will vary from person to person. For example in some people the valve is only mildly abnormal, whereas in others it may be badly deformed and displaced quite significantly. As the valve leaks, the right atrium will enlarge further with the increased blood supply, whilst at the same time the right ventricle will get larger as it strives to deliver sufficient blood to the lungs. Thus the right chambers of the heart will enlarge and weaken which can ultimately lead to heart failure.

Conditions which are linked with Ebstein’s

  • Atrial septal defect

Around 50% of those with Ebstein’s will also have a small hole between the two upper chambers of the right atrium and the left atrium,  which is called an atrial septal defect (ASD).   One consequence of this hole is that blood with little oxygen from the right atrium may mix with oxygen-rich blood in the left atrium which causes lower overall levels of oxygen in the blood (this can be measured as saturations), and may lead to a symptom which causes the person to have bluish coloured lips and skin/nails (cyanosis).  ASD can also increase the risk of a clot passing through the heart to your brain resulting in a stroke.  If surgery is performed to repair/replace the tricuspid valve then it is a simple procedure to close this hole at the same time.

  • Abnormal Heartbeats (arrthythmias)

Abnormal heart rythmns can be a symptom of Ebsteins, as well as very fast heartbeats (tachycardia).  These symptoms also lessen the effectiveness of the heart.  Where the heart is beating very fast then fainting spells may occur (syncope).

  • Wolff-Parkinson-White (WPW) syndrome

Some people with Ebstein’s may also have a condition known as Wolff-Parkinson-White syndrome, which is essentially an abnormal electrical pathway in the heart.  This condition can mean that very fast heartbeats and fainting spells may occur.  This condition can be treated with surgery, and the procedure can be done using a special catheter entering a vein through the groin.

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