Atrioventricular Canal Defect

What is an atrioventricular canal defect?

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

The condition makes your heart work too hard to pump blood. It also lets blood flow in the wrong direction. An AV canal defect can lead to a range of health conditions, including congestive heart failure.

The surgery to fix this has a high success rate. Without the operation, children usually only live two or three years.

How does blood flow through the heart?

Knowing how blood flows through your heart can make it easier to understand an AV canal defect.

Your heart has four chambers: two upper chambers (atria) and two lower chambers (ventricles). Valves with flaps connect the upper and lower chambers. The right chambers pump blood without oxygen from your body to your lungs. The lungs give oxygen to this blood, which then flows to the left chambers. The left chambers pump this blood with oxygen back to your entire body.

A wall (the septum) separates the right and left sides of your heart, which helps keep blood flowing in the right direction. Having an atrioventricular canal defect means there’s a hole in that wall. It’s 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 normally 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, the flow may go in the opposite direction, with more blood going to your body than to your lungs.

What is another name for AV canal defect?

Other names for AV canal defect include:

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

Types of AV canal defect

An atrioventricular canal defect can take different forms:

• Complete AV canal defect: The hole is big enough to provide an opening between all four chambers of your heart. Instead of the normal two valves between the upper and lower chambers, there’s just one valve. Its flap might not open and shut correctly.
• Partial AV 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 AV 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 AV 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.”

How common is AV canal defect?

About 1 in 1,900 babies are born with this defect each year in the U.S. It makes up between 3% and 5% of all congenital heart defects.

Atrioventricular septal defects are common in children with Down syndrome. They also occur in up to 40% of fetuses with trisomy 21.

What are the symptoms of AV canal defect?

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.

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

What is the cause of atrioventricular canal defect?

Atrioventricular septal defect causes are unclear. It’s likely a combination of genetic and environmental factors. There’s a strong correlation between this congenital heart condition and Down syndrome.

What are the risk factors for atrioventricular septal defect?

Experts haven’t identified the exact risk factors for AVSD. 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 defect include:

• Certain medications.
• Recreational drug or alcohol use.
• Exposure to environmental toxins or chemicals.
• Nutrient or vitamin deficiencies.
• Having obesity.
• Smoking or using tobacco products.
• Unmanaged chronic health conditions, such as diabetes or high blood pressure (hypertension).
• Viruses or fevers, like influenza (flu).

What are the complications of atrioventricular septal defect?

A severe atrioventricular canal defect can lead to:

• Arrhythmia.
• Congestive heart failure.
• Endocarditis.
• Pulmonary hypertension.

How is an atrioventricular septal defect diagnosed?

A healthcare provider can often diagnose an atrioventricular canal 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 on an ultrasound.
• A fetal echocardiogram creates images of the heart that have more detail than an ultrasound. It can give a healthcare 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 baby’s heart.
• Electrocardiogram (EKG) to track the electrical activity of your baby’s heart.
• Cardiac catheterization to learn more about the defect’s severity.
• 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 do you fix AV canal defect?

An AV canal defect usually requires open-heart surgery. During atrioventricular septal defect repair, your surgeon will put patches on the hole in your baby’s septum. In the case of a complete defect, your surgeon also will 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 will need several operations leading to a Fontan procedure.

It’s best to do surgery as early as possible, before the heart sustains lasting damage. 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 that isn’t healthy enough for surgery may need medication to manage symptoms until they gain weight and strength. Another option is a short-term procedure: pulmonary artery banding. This allows less blood to go through their pulmonary artery to their lungs. Babies who receive pulmonary artery banding can have a permanent repair later.

Complications of the treatment

After surgery, a child may have:

• Heart block.
• 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 septal defect be prevented?

There’s no way to prevent an AV 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 body weight that’s healthy for you.
• Managing chronic health conditions.
• Taking prenatal vitamins, including folic acid, as directed by your healthcare provider.

What is the prognosis for AV canal defect?

Without surgery, most children with an AV canal defect 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 decade 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 detect 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, 5% to 10% of them for the leaky (regurgitant) valve.

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

How do I take care of my child?

You may need to limit your child’s physical activity. Ask your child’s pediatric cardiologist 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 a 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 doctor?

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

• What type of 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?