Causes

Ebstein anomaly is a heart defect that you have at birth (congenital). The cause is unknown. To understand how Ebstein anomaly affects your heart, it helps to know how the heart works to supply your body with blood.

How your heart works

Your heart is made up of four chambers. The two upper chambers (atria) receive blood. The two lower chambers (ventricles) pump blood.

Four valves open and close to let blood flow in one direction through the heart. Each valve consists of two or three strong, thin flaps (leaflets) of tissue. A closed valve prevents blood from flowing to the next chamber or from returning to the previous chamber.

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

What happens in Ebstein anomaly

The tricuspid valve normally sits between the two right heart chambers (right atrium and right ventricle).

In Ebstein anomaly, the tricuspid valve sits lower than normal in the right ventricle. This makes it so that a portion of the right ventricle becomes part of the right atrium, causing the right atrium to enlarge and not work properly.

Also, the tricuspid valve's leaflets are abnormally formed. This can lead to blood leaking backward into the right atrium (tricuspid valve regurgitation).

The location of the valve and how poorly it's formed varies from person to person. Some people have a mildly abnormal valve. Others have a valve that leaks severely.

Other heart conditions associated with Ebstein anomaly

Common associated heart conditions include:

• Holes in the heart. Many people with Ebstein anomaly have a hole between the two upper chambers of the heart called an atrial septal defect or an opening called a patent foramen ovale (PFO). A PFO is a hole between the upper heart chambers that all babies have before birth that usually closes after birth. It can remain open in some people without causing issues.

  These holes can decrease the amount of oxygen available in your blood, causing a bluish discoloration of the lips and skin (cyanosis).

• Abnormal heartbeats (arrhythmias). An abnormal heart rhythm or rapid heartbeats make it difficult for the heart to work properly, especially when the tricuspid valve is leaking severely. Sometimes, a very fast heart rhythm causes fainting spells (syncope).
• Wolff-Parkinson-White (WPW) syndrome. People with WPW syndrome have an abnormal electrical pathway in the heart that can lead to fast heart rates and fainting spells.