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Endocardial Cushion Defect (Atrioventricular Septal Defect)


What is an endocardial cushion defect?

Endocardial cushion defect is a birth defect of the heart. It is also called atrioventricular canal defect or atrioventricular septal defect (AVSD). AVSD involves problems with the structure of the heart. The heart normally has 2 upper chambers (atria) and 2 lower chambers (ventricles). A normal heart also has 2 heart valves that separate the upper and lower chambers (the tricuspid and mitral valves).

In AVSD, there may be a large hole in the wall between the chambers of the heart (the atrioventricular septum). In some cases the tricuspid and mitral valves may not be separate. Instead, there can be one large valve between the upper and lower chambers of the heart (called the common atrioventricular valve).

The large opening in the center of the heart allows oxygen-rich and oxygen-poor blood to mix. The heart pumps blood in a way that is not efficient. The heart has to work harder and it becomes enlarged.

How does it occur?

AVSD can happen when the heart does not develop normally before birth. The cause is not known, but it is commonly found in babies with Down syndrome.

What are the symptoms?

The symptoms may start at any time from birth to several months after birth. Most babies with this problem do not eat well. They may not grow normally. They breathe fast. They often have colds and may get pneumonia. They may sweat and be clammy.

How is it diagnosed?

Children with AVSD usually have a heart murmur, which is an abnormal sound a healthcare provider can hear with a stethoscope. To diagnose the problem, the following tests may be done:

  • a chest X-ray to look for enlargement of the heart
  • an electrocardiogram (EKG), which is a recording of the electrical activity of the heart
  • an echocardiogram, which uses sound waves to make pictures of the heart
  • cardiac catheterization, which is a procedure for passing a small tube through an artery of the leg and into the heart to take special X-ray pictures of the heart with a dye.

How is it treated?

Surgery can repair the defect. The surgeon will close the hole in the septum and rebuild the valves if needed.

In rare cases, the defect is too complex to make all the repairs at one time. The surgeon may place a band around the lung artery to narrow the artery and reduce blood flow to the lungs. Then the heart will not have to work as hard, and the lungs will be protected from high blood pressure. When the child is older, the pulmonary artery band can be removed and corrective surgery done.

How long will the effects last?

If a child with AVSD is not treated, they may:

  • Often have pneumonia.
  • Have an enlarged heart, which means the heart won’t pump as well as it should.
  • Have high blood pressure in the lungs.
  • Have heart failure, which means the heart is not pumping as well as it should.

With treatment, a child has a much better chance for a healthier life. Sometimes, the heart valves are too small or the valves allow blood to leak backward. If the valves do not work properly after surgery, the child may need another operation to fix them. A child may also have damage to the lungs that makes it harder to breathe, or they may have abnormal heart rhythms.

A cardiologist who specializes in congenital heart disease will examine your child from time to time after the surgery.

Children with AVSD may need to take antibiotics before dental work and some other procedures to prevent infection of the heart.


Written by Reginald L. Washington, MD, FAAP, FACC, for RelayHealth.
Published by RelayHealth.
Last modified: 2009-08-23
Last reviewed: 2009-04-28

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a health care professional.

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