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Ebstein's Anomaly
Introduction
Ebstein's anomaly is a rare heart defect that's present at birth (congenital). It primarily involves the lower right chamber of your heart (right ventricle) and the tricuspid valve — the valve between the upper right chamber (atrium) and the right ventricle.
In Ebstein's anomaly, your tricuspid valve doesn't work properly, so blood leaks back through the valve and into the right atrium. As a result, your heart works less efficiently. Ebstein's anomaly may also lead to enlargement of the heart. In addition, about half the people with Ebstein's anomaly have a hole in their heart, and one in four has episodes of fast heartbeats.
If no signs or symptoms are present, careful monitoring of your heart may be all that's necessary. If signs and symptoms become troublesome, or if the heart is enlarging or becoming weaker, treatment for Ebstein's anomaly may be necessary. Treatment options include medications and surgical repair.
Signs and symptoms
People with a mild form of Ebstein's anomaly may not experience any signs or symptoms until later in adulthood. Even some people with very abnormal valves may have minimal, if any, problems. Signs and symptoms may develop slowly over many years and include:
- Shortness of breath.
- Fatigue, especially with exertion.
- Leg swelling.
- Heart palpitations or abnormal heart rhythms (arrhythmias).
- A bluish discoloration of the lips and skin caused by low oxygen (cyanosis).
Older children may show signs of heart failure, such as tiring easily or becoming short of breath during play. They may also experience sensations of the heart pounding or racing or show signs of cyanosis, especially around the lips and fingertips.
Causes
Your heart is made up of four chambers. The top two chambers are the right and left atria (plural for atrium). The two lower chambers, the ventricles, are larger, thick-walled chambers that do the work of pumping blood. Separating the atria from the ventricles are flexible structures called 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.
Deoxygenated blood returning from your body 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, freshly oxygenated blood from your lungs flows into the left atrium, through the mitral valve and then into the left ventricle, which pumps the blood to the rest of your body.
What happens in Ebstein's anomaly
In Ebstein's anomaly, the tricuspid valve is displaced downward into the right ventricle so that a portion of the right ventricle becomes part of the right atrium (becomes atrialized). As a result, the right atrium is larger than usual and the functional right ventricle is abnormal.
In addition to the downward displacement of the tricuspid valve, the valve's leaflets are typically malformed. This can lead to blood leaking backward (regurgitating) into the right atrium. In cases of severe malformation, the leaflets may be tethered to the wall of the right heart, inhibiting their movement and leading to severe leakage of blood into the atrium. One leaflet — the anterior leaflet — is often enlarged (sometimes described as "sail-like") in contrast to the other two small leaflets.
The degree of downward displacement and malformation varies from person to person. In some, the valve is only mildly abnormal. In others, the valve may be extremely displaced and malformed, and there may be severe leakage. With greater leakage of the valve, the right atrium enlarges as it receives an increased volume of blood. At the same time, the right ventricle enlarges (dilates) as it tries to cope with the leaky valve and still propel blood to the lungs. Thus, the right-sided chambers of the heart enlarge, and as they do so, they weaken, leading to right heart failure.
Congenital heart defects arise early in the development of a baby's heart. What causes the defect to occur is uncertain. Genetic and environmental factors are both thought to play a role. In rare cases, a mother's exposure to lithium or a viral infection may lead to Ebstein's anomaly.
Associated disorders
Other heart disorders may be associated with Ebstein's anomaly. Two common conditions are:
- Atrial septal defect. About half the people with Ebstein's anomaly have a hole between the two upper chambers of the heart called an atrial septal defect. 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 and causing cyanosis. Depending on the size of the hole, an atrial septal defect associated with Ebstein's anomaly can increase your risk of a blood clot passing from your peripheral veins — which return deoxygenated blood to your heart — into your general circulation and causing a stroke. If you have surgery to repair your tricuspid valve, your surgeon will also close the atrial septal defect at the same time.
- Heart rhythm disturbances (arrhythmias). In a normal heart, a special group of cells in the right atrium generates electrical impulses that travel via specific pathways through the heart. These electrical impulses help your heart to beat in an orderly and efficient manner. But about 15 percent of people with Ebstein's anomaly have one or more extraneous (accessory) pathways that allow electrical impulses to bypass the normal circuit and cause an abnormal heart rhythm (arrhythmia) characterized by rapid heartbeats (tachycardia). These types of arrhythmias (tachyarrhythmias) can reduce your heart performance, especially when the tricuspid valve is leaking severely. In addition, other tachyarrhythmias, such as atrial fibrillation and atrial flutter, occur with increased frequency as the right atrium becomes dilated. In some cases, a very fast heart rhythm may cause fainting spells (syncope).
Treatment of Ebstein's anomaly depends on the severity of the defect and your signs and symptoms. The goal of treatment is to minimize symptoms and avoid future complications, such as progressive heart enlargement and heart failure, and arrhythmias. Treatment strategies may include:
Regular monitoring
If you have no signs or symptoms or abnormal heart rhythms, your doctor may simply recommend careful monitoring of your heart condition with regular checkups. Checkups typically include a thorough physical exam, electrocardiogram, chest X-ray, echocardiogram and, if necessary, a Holter monitor test. Your doctor may also ask you to undergo an exercise test, such as walking on a treadmill. This test measures your tolerance for activity and checks your heart's response to exertion (exercise).
Medications
If you have heart rhythm disturbances, medications may help control heart rate and maintain normal heart rhythm. Doctors commonly use medications, including calcium channel blockers, beta blockers, digitalis and anti-arrhythmic drugs, such as amiodarone.
Your doctor may also prescribe medications for signs and symptoms of heart failure, if you need them. These may include diuretics and digoxin. The role of angiotensin-converting enzyme (ACE) inhibitors and beta blockers, medications commonly used to treat other forms of heart failure, isn't well established in people with Ebstein's anomaly who have heart failure.
Surgical heart repair
Your doctor may recommend surgical repair when your signs and symptoms are troublesome or when your heart begins to enlarge and overall heart function begins to decrease. Because Ebstein's anomaly is rare, choose a surgeon who's familiar with the defect and who has experience performing the procedure. Different types of procedures can be used to surgically treat Ebstein's anomaly and associated defects, including:
- Tricuspid valve repair. This involves reducing the size of the valve opening and allowing the existing valve leaflets to come together in order to create a better functioning valve. This procedure is usually done when there's enough valve tissue to allow for repair. An experienced surgeon is more likely to perform a successful valve repair.
- Tricuspid valve replacement. If the existing valve can't be repaired, it may be replaced by removing the deformed valve and inserting either a mechanical valve or a specially treated biological tissue (bioprosthetic) valve. If a mechanical valve is used, you'll need to take a blood-thinning medication for the rest of your life. The durability of a bioprosthetic valve is favorable in this location. Consequently, a bioprosthetic valve is preferred in most circumstances when replacement is necessary.
- Closure of the atrial septal defect. If an atrial septal defect is present, your surgeon can close the channel during surgery to repair or replace the defective valve.
- Maze procedure. Another procedure that doctors may perform during valve repair or replacement surgery is called a maze procedure. It's used to address abnormally fast heart rhythms in the atrium (atrial tachyarrhythmias). To do the procedure, your surgeon makes a series of incisions in the right atrium with a scalpel or a cryoablation device that destroys tissue by freezing it. When these incisions heal, the scars they leave interrupt the extra electrical pathways and act as boundaries to force orderly electrical activation.
Some extraneous electrical pathways also can be treated using catheter ablation. In this procedure, one or more catheters are threaded through your blood vessels to your inner heart. They're positioned along electrical pathways identified by your doctor as causing your arrhythmia. Electrodes at the catheter tips are heated with radiofrequency energy. This destroys (ablates) a small spot of heart tissue and creates an electrical block along the pathway that's causing your arrhythmia. Usually, this stops your arrhythmia.
Heart transplantation
If you have Ebstein's anomaly with severe valve involvement and markedly reduced heart function, you may be eligible for heart transplantation.
Information obtained from National Institute of Health