Ebstein's anomaly is a heart defect that you have at birth (congenital). Why it occurs is still unknown. To understand how Ebstein's anomaly affects your heart, it helps to know a little about how the heart works to supply your body with blood.

How your heart works

Your heart is made up of four chambers. The top two chambers are called the right and left atria ("atria" is plural for "atrium"). The two lower chambers, the ventricles, are larger, thicker walled chambers that do the work of pumping blood. Separating the atria from the ventricles are valves, which keep the blood flowing in the right direction through the heart. Each valve consists of two or three strong, thin flaps (leaflets) of tissue. When closed, a valve prevents blood from flowing to the next chamber or from returning to the previous chamber.

Blood returning from your body, which lacks oxygen, flows into the right atrium, through the tricuspid valve and then into the right ventricle, which pumps the blood to your lungs to receive oxygen. On the other side of your heart, oxygen-rich blood from your lungs flows into the left atrium, through the mitral valve and then into the left ventricle, which then pumps the blood to the rest of your body.

What happens in Ebstein's anomaly

In Ebstein's anomaly, the tricuspid valve is farther down into the right ventricle than it would be in a normal heart. This makes it so that a portion of the right ventricle becomes part of the right atrium (becomes atrialized), causing the right atrium to be larger than usual. Because of this, the right ventricle can't work properly.

In addition to the problems with the placement of the tricuspid valve, the valve's leaflets are abnormally formed. This can lead to blood leaking backward (regurgitating) into the right atrium.

Where the valve is placed and how poorly it's formed varies from person to person. In some people, the valve is only mildly abnormal. In others, the valve may be extremely displaced, and it may leak severely. The more the valve leaks, the more the right atrium enlarges as it receives more blood. At the same time, the right ventricle enlarges (dilates) as it tries to cope with the leaky valve and still deliver blood to the lungs. Thus, the right-sided chambers of the heart enlarge, and as they do, they weaken, leading to heart failure.

Other heart conditions associated with Ebstein's anomaly

Other heart conditions may be associated with Ebstein's anomaly. Three common conditions are:

  • Atrial septal defect. About half of those with Ebstein's anomaly have a hole between the two upper chambers of the heart called an atrial septal defect (ASD). This hole may allow deoxygenated blood in the right atrium to mix with oxygenated blood in the left atrium, decreasing the amount of oxygen available in your blood. This causes a bluish discoloration of the lips and skin (cyanosis).
  • Abnormal heartbeats (arrhythmias). Some people with Ebstein's anomaly have an abnormal heart rhythm (arrhythmia) characterized by rapid heartbeats (tachycardia). These types of arrhythmias (tachyarrhythmias) can make your heart work less effectively, especially when the tricuspid valve is leaking severely. In some cases, a very fast heart rhythm may cause fainting spells (syncope).
  • Wolff-Parkinson-White (WPW) syndrome. Some people with Ebstein's anomaly may also have a condition known as Wolff-Parkinson-White syndrome — an abnormal electrical pathway in the heart. The presence of WPW syndrome can lead to very fast heart rates and fainting spells.
Jan. 21, 2016