When Your Child Has an Atrioventricular (AV) Canal Defect

The heart is divided into 4 chambers. The 2 upper chambers are called atria and the 2 lower chambers are called ventricles. The heart contains 4 valves. The valves open and close to keep blood flowing forward through the heart. An atrioventricular (AV) canal defect is a large hole in the center of the heart. It’s caused by the following problems with heart structure:

• Atrial septal defect (ASD). A hole in the dividing wall (atrial septum) that separates the atria in the heart.

• Ventricular septal defect (VSD). A hole in the dividing wall (ventricular septum) that separates the ventricles in the heart.

• A single atrioventricular (AV) valve. A single valve that develops in place of the separate tricuspid (right side) and mitral valves (left side). These valves control the flow of blood from the atria to the ventricles.

When all of these heart problems are present, the AV canal defect is considered “complete.” The doctor can tell you more about your child’s heart and the exact defects he or she has. An AV canal defect can usually be treated.

Normal heart	An AV canal defect causes more blood than normal to pass through the right side of the heart and lungs through an ASD and VSD.

What causes an atrioventricular canal defect?

An AV canal defect is a congenital heart defect. This means it is a problem with the heart’s structure that your child was born with.The exact cause is unknown. Children with Down syndrome (trisomy 21) are at higher risk of having this heart defect.

Why is an atrioventricular canal defect a problem?

Blood normally flows from chamber to chamber in one direction through the left and right sides of the heart. With an AV canal defect, blood flows through the ASD and VSD from the left side of the heart to the right side. This is called a left-to-right shunt. It causes more blood than normal to pass through the right side of the heart. It causes the left side of the heart to become enlarged (dilated). More blood than normal has to be pumped to the lungs. Over time, the extra blood flow causes the lungs to become filled with extra blood and fluid. This leads to a condition called congestive heart failure (CHF). Problems can also occur with the single AV valve. Because it's malformed, blood may leak backward from the ventricles to the atria (valve insufficiency or regurgitation). This causes the heart to need to work even harder. 

What are the symptoms?

Children with an AV canal defect usually have signs and symptoms of CHF in infancy. These include:

• Tiredness

• Trouble breathing or rapid breathing

• Trouble feeding

• Poor weight gain and growth

• Sweating

• Blue or purple coloring of the lips, skin, and nails (cyanosis)

• Heart murmur

Depending on how serious the defect is and several other factors, symptoms may not show up until adulthood.

How is an atrioventricular canal defect diagnosed?

During a physical exam, the doctor checks for signs of a heart problem such as a heart murmur. This is an extra noise caused when blood doesn’t flow smoothly through the heart. If a heart problem is suspected, your child may be referred to a pediatric cardiologist. This is a doctor with special training to diagnose and treat heart problems in children. To check for an AV canal defect, the following tests may be done:

• Chest X-ray. X-rays are used to take a picture of the heart and lungs.

• Electrocardiogram (ECG). The test records the electrical activity of the heart.

• Echocardiogram (echo). Sound waves (ultrasound) are used to create a picture of the heart and look for structural defects.

• Pulse oximetry. The test looks at how much oxygen is in the blood.

• Cardiac catheterization. The test measures blood pressure and oxygen inside the heart. It also lets the doctor look at the inside of the heart. The test is done with a long thin tube (catheter) that is put in through a blood vessel in the groin or other area and moved to the heart.

• Cardiac MRI. This test gives 3-D images of the heart. It can show any defects.

How is an atrioventricular canal defect treated?

Children with a complete AV canal defect are treated early in infancy with heart surgery, usually within the first 6 months of life. Medicines may be prescribed to help manage symptoms until surgery is scheduled. These can include:

• Water pills (diuretics), which help rid the body of excess water. This reduces fluid in the lungs and may improve breathing.

• Digoxin, which helps the heart pump blood with more force. This improves how heart works.

• ACE inhibitors, which make blood vessels relax and allow blood to flow more easily from the heart.

• Nutrition. A baby with an atrioventricular canal defect may need supplemental nutrition with a feeding tube.

Your child’s experience: heart surgery

Heart surgery to repair an AV canal defect is done by a pediatric heart surgeon. The surgery lasts about 4 to 6 hours. It takes place in an operating room in a hospital. You’ll stay in the waiting room during your child’s surgery:

• Before surgery. You’ll be told to keep your child from eating or drinking anything for a certain amount of time before surgery. Follow these instructions carefully.

• During surgery. Your child is given medicine (sedative and anesthesia) to sleep and not feel pain during surgery. A breathing tube is placed in your child’s windpipe (trachea). Special equipment monitors your child’s heart rate, blood pressure, and oxygen levels. Your child is also placed on a heart-lung bypass machine. This allows blood to continue flowing to the body while the heart is stopped so that it can be operated on. An incision is made in the chest through the breastbone (sternum) to access the heart. The ASD and VSD are repaired with 1 or 2 patches. The single AV valve is rebuilt into 2 separate valves. Once the repair is complete, your child is taken off the bypass machine and the chest is closed.

• After the surgery. Your child is taken to a critical care unit to be cared for and monitored. You can stay with your child during this time. He or she may remain in the hospital for 7 to 10 days. When your child is ready to leave the hospital, you’ll be given instructions for home care and follow-up.

Risks and complications of heart surgery

• Reaction to sedative or anesthesia

• Leakage of blood through one or both of the new valves back into the atria (valve insufficiency)

• Stenosis of 1 or both of the new valves

• Incomplete closure of the ASD, VSD, or both. This requires more treatment.

• Abnormal heart rhythm (arrhythmia)

• Infection

• Bleeding

• Nervous system problems

• Abnormal buildup of fluid around the heart and lungs

What are the long-term concerns?

• After treatment, most children with an AV canal defect can be active. The level and extent of physical activity will vary with each child. Certain contact sports, such as football, may need to be avoided. Check with the cardiologist about what activities are appropriate for your child.

• Regular follow-up visits with the cardiologist are needed for the rest of your child’s life. The rebuilt valves will always be abnormal. They need to be checked to make sure they’re working properly without too much leakage, especially the mitral valve. Further valve treatment or replacement may be needed later in life.

• Depending on the details of the surgical repair, your child may need to take antibiotics before having any surgery or dental work to prevent infection of the inside lining of the heart and valves. This infection is called infective endocarditis. Antibiotics should be taken as directed by the cardiologist.

• Most children born with AV canal defects today go on to lead productive lives as adults.