Atrioventricular Canal Defect (Atrioventricular Septal Defect)

An atrioventricular canal defect (also known as an atrioventricular septal defect, or an AV canal defect or AV septal defect) is a condition that develops before birth, when the central area of a baby’s heart doesn’t form properly during pregnancy.

With this condition, the wall dividing the left and right side of the heart has one or more holes in it (known as atrial septal defects or ventricular septal defects). Sometimes the two valves that connect the heart’s upper and lower chambers don’t develop correctly either. Instead of forming as separate valves, they may form just one common valve.

This can allow blood to mix between the heart’s chambers and leak from the valves, and cause too much blood to flow to the lungs. As a result, both the heart and the lungs have to work harder than they should, putting a strain on the body.

Many babies with an AV canal defect often have other heart problems too. Connecticut Children’s uses echocardiography and cardiac magnetic resonance imaging (MRI) to take detailed pictures of the heart. Our specialists work as a team to understand each patient’s unique heart conditions, and make a plan for treatment.

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What Are the Signs and Symptoms of an AV Canal Defect?

Many children and adults only have mild signs or symptoms, or none at all. More serious cases may have the following symptoms.

  • Bluish or greyish skin, lips and nails
  • Heart murmur
  • Heart beat that’s too fast, too slow or irregular
  • Trouble breathing
  • Chest pain
  • Low energy
  • Swelling in the legs, ankles and feet

At Connecticut Children’s, we can diagnose many congenital heart problems in utero before babies are even born. We work with our award-winning neonatologists, fetal cardiologists, the mother’s labor and delivery doctors, and our other pediatric specialists to plan ahead for the birth and the important moments that follow.
 

What Causes AV Canal Defects?

AV canal defects develop before birth, when the baby’s heart doesn’t form properly during the first eight weeks of pregnancy.

Doctors don’t fully understand what causes this condition, but have noticed that it often occurs in in children with Down syndrome (trisomy 21). It may also be passed down from a parent, or caused by contact during pregnancy with certain chemicals or illnesses.

How Are AV Canal Defects Treated?

Babies born with this condition typically need to have surgery within their first six months of life. The timing and type of surgery depends on their unique condition and health.

Connecticut Children’s cardiac surgeons specialize in cutting-edge techniques to treat atrioventricular canal defects. Our team is known for performing complex surgeries on even the tiniest babies, with outstanding surgical outcomes.

Medication to manage the condition until the baby is big enough for surgery

  • Two-ventricle (biventricular) repair: Complex procedure to repair or replace any valves that didn’t form correctly, creating a normal, two-ventricle arrangement
  • Less often, staged reconstruction known as “single ventricle palliation”: A series of open-heart surgeries to rebuild the heart and redirect how blood flows through it. This approach may be used when the AV canal is “unbalanced,” meaning it can’t support two ventricles.
  • Norwood procedure: Allows the right ventricle to pump blood to the body
  • Glenn procedure: Connects a large vein to the pulmonary artery, allowing blood to flow directly to the lungs
  • Fontan procedure: Directs blood from the lower half of the body directly into the lungs to receive oxygen