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Atrioventricular Canal Defect

What Is an Atrioventricular Canal Defect?

An atrioventricular canal defect (AV canal for short) is a heart problem in which the center of a baby's heart does not form normally before birth.

AV canal is also called atrioventricular septal defect or endocardial cushion defect.

What Happens in an Atrioventricular Canal Defect?

The heart has four chambers — a left atrium and right atrium, and a left ventricle and right ventricle. The septum is a wall that divides the left and right sides of the heart. The tricuspid valve separates the right atrium from the right ventricle, and the mitral valve separates the left atrium from the left ventricle.

In AV canal, the center of the heart didn't form normally. Depending on whether the AV canal is complete or partial, there may be:

  • a hole between the atria in the top part of the septum (an atrial septal defect, or ASD)
  • a hole between the ventricles in the bottom part of the septum (a ventricular septal defect, or VSD)
  • a large common valve between the atria and ventricles, rather than two separate valves (the tricuspid valve and mitral valve) or abnormal tricuspid and mitral valves

A baby with a complete AV canal has an ASD, a VSD, and a large common valve between the atria and ventricles.

A baby with a partial AV canal has an ASD and a common or abnormal valve between the atria and ventricles, but no VSD.

Diagram of complete atrioventricular canal shows right atrium and right ventricle, left ventricle, left atrium, ASD, VSD and common atrioventricular valve.

What Problems Can Happen?

Normally, the heart pumps blood with low oxygen from its right side to the lungs, where it picks up oxygen. Then, it pumps the blood with oxygen from its left side to the body. There is no mixing of blood between the left and right sides of the heart.

But in AV canal, blood mixes freely within the heart because of the holes and abnormal valves. There is increased blood flow to the lungs, which can cause heart failure over time. And the blood that goes to the body doesn’t have enough oxygen in it for the baby to grow and thrive.

What Are the Signs & Symptoms of an Atrioventricular Canal Defect?

A baby with a complete AV canal usually starts showing symptoms in the first days or weeks of life. These can include:

  • wheezing or fast breathing
  • an irregular or fast heartbeat
  • not moving as much as other babies the same age
  • poor growth and weight gain
  • trouble feeding
  • blue lips, skin, and nails (called cyanosis)

A baby with a partial AV canal may have milder symptoms that aren't noticed until later in childhood or early adulthood.

Diagram of partial atrioventricular canal shows right atrium and right ventricle, left ventricle, left atrium, ASD, and abnormal atrioventricular valve.

What Causes Atrioventricular Canal Defects?

The exact cause of AV canal isn't known. It happens early in pregnancy while the fetus is first developing. There is no way to prevent it.

AV canal is more common in babies with Down syndrome.

How Are Atrioventricular Canal Defects Diagnosed?

Doctors might find AV canal on an ultrasound before a baby is born. Other times, the baby shows symptoms or has a heart murmur (an extra heart sound) after birth. Doctors will do tests to find the cause. These can include:

How Are Atrioventricular Canal Defects Treated?

Cardiologists (heart doctors) and cardiothoracic surgeons (heart surgeons) work with a team of pediatric specialists to treat AV canal. Most babies with AV canal will need surgery. Other treatments include:

  • nutritional support: Some babies get too tired to eat a full meal and need to be fed through a nasogastric tube that goes from their nose into their stomach.
  • medicines: Different medicines can help a baby’s heart pump better, make sure the baby gets enough oxygen, and help with symptoms caused by heart failure.

How Can Parents Help?

Learn as much as you can about AV canal and the treatments your child needs. This will help you work with the care team and better help your child. Be sure to ask when you have questions.

Your baby’s heart will work better after surgery, but problems can still happen. Take your child to a cardiologist for regular follow-up visits. Your child should continue these visits as an adult. The cardiologist can watch for any new problems and treat them early.

You play a big role in your child's treatment. Keep a record of:

  • your child’s medical visits, medicines, and any symptoms
  • any special instructions for taking care of your child at home
  • any questions you have for the care team

What Else Should I Know?

Children with AV canal will need many follow-up doctor visits and tests. The doctors, nurses, social workers, and other members of the care team are there to help you and your child. Talk to any of them about resources that can help your family.

Take time to take care of yourself too. Parents who get the support they need are better able to support their children.

It can help to find a support group for parents of children with heart conditions. Ask the care team for recommendations.

You also can find more information and support online at:

Reviewed by: Abbas H. Zaidi, MD
Date Reviewed: 01-06-2022

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