Atrioventricular Canal Defect

What is an atrioventricular canal defect?

An atrioventricular (AV) canal defect is a congenital (present at birth) heart condition. It describes a group of several heart issues, including a hole in the wall (septum) at the center of your heart and problems with the way your heart’s valves work.

Having a hole in the wall that separates the right and left sides of your heart is like a pipe with a leak. It allows oxygen-rich blood (normally from the left side of your heart) to mix with oxygen-poor blood (normally from the right side of your heart). These don’t mix in a properly functioning heart.

In most cases, the hole allows too much blood to flow into your lungs and not enough blood to flow to the rest of your body. If the hole is present for a long time, blood with less oxygen may flow in the opposite direction, with more of that blood going to your body than your lungs. This can result in lower oxygen levels and cyanosis (bluish coloring of your skin).

By making your heart work too hard to pump blood, an AV canal defect can lead to a range of health conditions like congestive heart failure.

AV canal defect can be fatal in children who don’t get treatment. Without an operation, children with this condition may only live two or three years. But the good news is that the surgery to fix this has a high success rate. Providers can diagnose an atrioventricular canal defect in a baby before it can cause fatal complications.

About 1 in 1,700 babies are born with this defect each year in the U.S. It makes up between 3% and 5% of all congenital heart defects.

Other names for AV canal defect include:

• Atrioventricular septal defect.
• AVSD.
• Atrioventricular canal defect.
• Endocardial cushion defect.

Types of atrioventricular canal defect

An atrioventricular canal defect can take various forms, with differences in hole size and number of valves.

Complete atrioventricular canal defect

The hole is big enough to make an opening between all four chambers of your heart. Instead of the typical two valves between the upper and lower chambers, there’s just one valve. Its flap might not open and shut correctly.

Partial atrioventricular canal defect

The hole is only between the wall of the two upper chambers (most typical) or the two lower chambers, not all four. There are two valves between the upper and lower chambers. But one of them (usually the mitral valve between the upper left atrium and lower left ventricle) doesn’t work correctly.

Transitional atrioventricular canal defect

There’s a hole between the two upper chambers and a smaller hole between the two lower chambers. The two AV valves are separate.

Unbalanced complete atrioventricular canal defect

The single (shared) AV valve is closer to one ventricle (lower chamber) than the other. The ventricle that gets more blood flow gets bigger than the other one. Providers call the smaller ventricle “hypoplastic.”

What are the symptoms?

Soon after birth, a baby may have atrioventricular canal defect symptoms like:

• Cyanosis (bluish tint to their skin).
• Difficulty feeding.
• Fatigue, especially when feeding.
• Heart palpitations or racing.
• Shortness of breath (dyspnea).
• Slow weight gain.
• Swelling (edema) in their abdomen (belly) or legs.
• Weak pulse.
• Sweating with feeding.

Babies with mild partial or transitional AV canal defect may not have symptoms until later in childhood or even their teen years or early adult years.

What causes an atrioventricular septal defect?

Researchers are unclear about what causes atrioventricular septal defect. It’s likely a combination of genetic and environmental factors. There’s a strong correlation between this congenital heart condition and Down syndrome. Atrioventricular septal defect occur in up to 40% of fetuses with this syndrome.

What are the risk factors for an atrioventricular canal defect?

Experts haven’t identified the exact risk factors for atrioventricular septal defect. Genetics may be a factor. A fetus can inherit an abnormal gene or genes from a parent, which may make them more likely to develop a heart condition in the uterus.

Other risk factors during pregnancy that may increase the chances of giving birth to a baby with a congenital heart issue include:

• Certain medications.
• Recreational drugs.
• Alcohol-containing beverages.
• Exposure to environmental toxins or chemicals.
• Nutrient or vitamin deficiencies.
• Obesity.
• Tobacco products.
• Unmanaged chronic health conditions like diabetes or high blood pressure (hypertension).
• Viruses or fevers, like influenza (flu).

What are the complications of an atrioventricular canal defect?

A severe atrioventricular canal defect can lead to:

• Abnormal heart rhythms (arrhythmia).
• Congestive heart failure.
• An infection in your heart (endocarditis).
• Pulmonary hypertension (high blood pressure in your pulmonary arteries).

How is it diagnosed?

A healthcare provider can often diagnose an atrioventricular septal defect before birth with a few tests:

• Prenatal ultrasound shows moving pictures of the fetus in the uterus, including its heart. A large septal defect may show up on an ultrasound.
• A fetal echocardiogram creates images of the heart with more detail than an ultrasound. It can give a provider information about the structure of the heart and how well it’s pumping blood.

A provider may use a stethoscope to listen to your baby’s heartbeat after birth. An abnormal “whooshing” sound may mean that blood is flowing through a hole in their septum. Other tests after birth might include:

• Chest X-rays to show the size and shape of your child’s heart.
• Electrocardiogram (EKG) to track the electrical activity of your baby’s heart.
• Echocardiogram to look at the structure of your child’s heart in detail.
• Cardiac catheterization to learn more about the severity of your child’s condition.
• Heart MRI to show the parts of your baby’s heart and how well they work.

In some cases, your baby may have a small septal defect that doesn’t cause symptoms right after birth. It might be several years before a healthcare provider detects the condition.

How is it treated?

Atrioventricular canal defect treatment usually consists of open-heart surgery. During atrioventricular canal defect repair, your surgeon will put patches on the hole in your baby’s heart. In the case of a complete defect, they’ll also split the single heart valve into two separate valves on the right and left sides of your child’s heart.

A baby with an unbalanced AV canal defect may need several operations leading to a Fontan procedure.

It’s best to do surgery as early as possible, before the condition causes lasting damage to your child’s heart. Many babies have the surgery during infancy, within their first six months of life. Some babies with a partial defect but no symptoms may get the surgery during their first three years of life.

A baby who isn’t healthy enough or large enough for surgery may need medication to manage symptoms until they gain weight and strength. Diuretics help clear excess water, while digoxin helps your baby’s heart beat more strongly. ACE inhibitors widen blood vessels to make it easier for blood to flow through them.

Another option is a short-term procedure: pulmonary artery banding. This allows less blood to go through your child’s pulmonary artery to their lungs. Babies who receive pulmonary artery banding can have a permanent repair later.

Complications of the treatment

After surgery, your child may have:

• Heart block (a problem with their heartbeat signal reaching the lower part of their heart).
• A leaky left or right AV valve.
• A hole that remains in the lower chamber wall (ventricular septal defect).
• Narrowing (stenosis) of the left or right AV valve.
• Subaortic stenosis (a blood flow obstacle below the aortic valve).

Can an atrioventricular canal defect be prevented?

There’s no way to prevent an atrioventricular septal defect. But if you’re pregnant, you can reduce the risk of your baby having a congenital heart defect by:

• Avoiding recreational drugs, alcohol and tobacco products.
• Getting all necessary vaccinations to prevent illness.
• Maintaining a weight that’s healthy for you.
• Managing chronic health conditions.
• Taking prenatal vitamins, including folic acid, as your healthcare provider recommends.

What can I expect if my child has an atrioventricular canal defect?

Without surgery, children with an AV canal defect may have a life expectancy of two or three years. Some live to be young adults.

About 90% of children who have repair surgery have a 10-year survival rate. This means they live for at least another 10 years on average after treatment. About 65% are alive 20 years after surgery.

But even after surgery, someone with an atrioventricular canal defect won’t have a typical heart. They’ll need periodic echocardiograms to monitor their heart’s function and catch complications early.

The patch over the hole can usually stay in place for the rest of a person’s life. But over time, one of the repaired heart valves may begin to leak. About 10% to 20% of people need a second surgery.

After surgery, many people don’t need medications or more operations for their heart. But cardiac arrhythmias may develop later in life. A provider may recommend minimally invasive procedures like ablation to treat an arrhythmia.

How do I take care of my child?

You may need to limit your child’s physical activity. Ask your child’s pediatric cardiologist (heart doctor for children) if you need to do this.

Children with an atrioventricular septal defect may need to take antibiotics before seeing the dentist. This can prevent endocarditis, a type of infection in your heart. Your child’s cardiologist can talk with you about this as well.

When should my child see their healthcare provider?

You should take your child to regular appointments with their pediatric cardiologist. They can monitor your child’s heart for any issues that develop. Some children with an AV canal defect need more treatment after surgery. A patch can leak and a repaired heart valve may develop a leak or get too narrow.

A child with an AV canal defect may also have neurological or developmental disorders. They may need help with these as well.

Once your child reaches adulthood, they should switch to an adult congenital heart specialist for annual visits.

What questions should I ask my child’s doctor?

Questions you may want to ask your child’s doctor include:

• Which type of AV canal defect does my child have?
• What symptoms might be signs that the condition is getting worse?
• When will they need surgery?
• Will my child need medication after the surgery?
• Will I need to limit my child’s activities?