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Atrioventricular Septal Defect

(Atrioventricular Canal Defect; Endocardial Cushion Defect)

Pronounced: A-tree-o-ven-TREAH-q-lar sep-TAL DEE-fect


The heart is made up of four chambers. A wall divides the chambers inside the heart. It helps to keep blood flowing through the heart, in the right direction.

An atrioventricular septal defect (AVSD) is a problem with how this area develops. It can lead to one or more holes in the wall between the right and left chambers. It can also lead to defects in the two heart valves between the upper and lower chambers. This can make it harder for blood to flow through the heart. It can also decrease the amount of oxygen going out to the body in the blood. There are different types of AVSD:

  • Complete AVSD:
    • Hole develops in wall where all four chambers meet
    • Only 1 large heart valve forms instead of 2 smaller ones
  • Partial AVSD:
    • Hole only develops between upper or lower chambers, not both
    • There are 2 heart valves but one does not work well

Poor blood flow through the heart will decrease the amount of oxygen for the body. It will also make it hard to move blood flow through the lungs. This can lead to a backup of fluid in the lungs and lung damage. AVSD also puts extra strain in the heart. It can lead to heart failure.


An AVSD is present at birth. A specific area of the heart does not form well when the heart is developing. This leaves defects in the walls and valves inside the heart.

It's not always known why these problems happen. A change in certain genes is sometimes found. The genes may be passed down by the parent. The genes may also be changed by the mother's health, exposures, or medicines during pregnancy.

Ventricular Septal Defect
Ventral septal defect

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Risk Factors

The chances of a baby with AVSD are higher for mothers who:

  • Have diabetes
  • Smoked during pregnancy

AVSD are also common in people with other genetic conditions. These defects are common in people with Down syndrome.


AVSD may not be obvious at birth. It may be a few weeks before symptoms develop. For partial AVSD, symptoms may not appear until after infancy. Others may have severe issues. Symptoms may include:

  • Breathing problems
  • Fast heart beat— tachycardia
  • Feeding problems
  • Failure to gain weight
  • Weight loss
  • Repeated lung infections
  • Cool feeling to the hands and feet
  • Tiring easily


Some AVSD may be found before birth. It may be noticed during an ultrasound. A fetal echocardiogram may also be done to get more detail.

If the AVSD is not found before birth, it may not be noticed until symptoms develop. The doctor will ask about your baby’s symptoms and past health. AVSD may cause a heart murmur that can be heard during an exam.

Tests may include:


The first step may be to manage stress on heart and lungs. Once the baby is old enough, many will have surgery. Those with lesser symptoms may be able to delay surgery. Without treatment, AVSD can lead to heart failure and severe lung damage.


Surgery for complete AVSD is often done by 3 to 6 months of age. The goal is to close the hole before there is too much heart and lung damage. One or two patches may be placed over the hole in the wall. Over time, the heart lining will grow over it.

The surgery may also need to correct damaged valves. The work that is done will depend on individual needs. Some options include:

  • A single valve will need to be split into 2 separate valves
  • 2 valves may be present but need repair to work better


Medicine can not treat AVSD. It can reduce the workload on the heart and ease symptoms for a time. Medicine may be used to:

  • Relax the blood vessels
  • Help the heart pump more effectively
  • Lessen the work load on the heart
  • Remove excess fluid from the body
  • Lower blood pressure

Support Care

Babies with AVSD may have slower growth and harder time eating. A high calorie diet may be recommended. These babies also have a higher risk of severe infections. Respiratory or lung infections will be treated very carefully.

Some will need to have activity limits as they get older. This is more common if valves can not be fully repaired and blood flow is still mixed.

Long Term Care

Your baby will be watched throughout their life. Problems can happen as they get older. Watching them on a regular basis will let their doctor treat problems as they come up. This may involve:

  • A yearly exam with a heart specialist
  • Regular tests of heart function
  • Changes to treatment plan


There is no way to prevent AVSD since the cause is unknown.


American Heart Association

Family Doctor—American Association of Family Physicians


Canadian Adult Congenital Heart Network

Heart and Stroke Foundation


Atrioventricular (AV) canal defect. EBSCO DynaMed Plus website. Available at: Updated March 14, 2018. Accessed July 25, 2018.

Atrioventricular septal defect. Merck Manual Professional Version website. Available at: Updated November 2016. Accessed July 25, 2018.

Complete atrioventricular canal defect (CAVC). American Heart Association website. Available at: Updated January 19, 2018. Accessed July 25, 2018.

Facts about atrioventricular septal defect (AVSD). Centers for Disease Control and Prevention website. Available at: Updated May 29, 2018. Accessed July 25, 2018.

Last reviewed May 2018 by EBSCO Medical Review Board Michael J. Fucci, DO, FACC  Last Updated: 7/25/2018