An atrioventricular (AV) canal defect is a congenital heart defect. This means that your child is born with it. AV canal defect is a large hole in the center of the heart. It is caused by a combination of problems with the heart's structure.

• Atrial septal defect. This is an opening in the wall (septum) between the two upper chambers of the heart. These are called the right and left atria.
• Ventricular septal defect. This is an opening in the wall between the two lower chambers of the heart. These are called right and left ventricles.
• Improperly formed mitral or tricuspid valves. This is when the valves that separate the upper heart chambers from the lower heart chambers aren't formed right.

Other heart problems, such as tetralogy of Fallot (TOF) and transposition of the great arteries (TGA), also commonly occur.

There are several types of this heart defect depending on how broad the defect is. These conditions cause oxygen-rich (red) blood and oxygen-poor (blue) blood to mix. This sends extra blood to your child's lungs.

Genes and family history may play a part in AV canal defects. AV canal defects are often linked to Down syndrome or other chromosome problems. Some cases may occur without a clear cause.

The symptoms of AV canal defect may be similar to symptoms caused by other heart problems.

Babies with AV canal defects often have symptoms. They can include:

• Tiredness
• Sweating
• Pale, cool skin
• Fast, heavy breathing
• Fast heart rate
• Chest congestion
• Trouble feeding
• Not enough weight gain

Your child's symptoms depend on the size of their septal openings. The larger the openings, the more blood is able to pass through them. This can overload your child's heart and lungs. This means that your child's symptoms may be more severe.

Over time, the pressure in your child's lungs will force blood back to their heart. This blood has low oxygen levels, and it's sent to the rest of the body. This causes your child's lips, nail beds, and skin to turn blue (cyanosis).

Your child may be diagnosed by ultrasound during pregnancy. Or your child's doctor may first suspect a heart defect when they hear an abnormal sound (heart murmur) when listening to your child's heart with a stethoscope. Your child may also have symptoms of a heart problem. Your child's doctor may refer your child to a heart doctor for children (pediatric cardiologist).

The heart doctor will check your child and listen to their heart and lungs. The location and loudness of the murmur will help the doctor make the diagnosis.

Your child's doctor may then do tests to confirm the diagnosis. The tests your child has depend on their age and condition, and the doctor's preferences.

A chest X-ray may show changes in the heart and lungs caused by an AV canal defect.

This test records the electrical activity of the heart. It also shows abnormal rhythms (arrhythmias) and spots heart muscle stress. These issues may be caused by an AV canal defect.

This test uses sound waves to make a moving picture of the heart and heart valves. An echo can show the pattern of blood flow through the septal openings. It can also show how large the openings are and how much blood is passing through them. Most AV canal defects are diagnosed with an echo.

A cardiac catheterization gives very detailed information about the structures inside the heart. In this test, a small, thin, flexible tube (catheter) is put into a blood vessel in your child's groin. Then the doctor guides it to your child's heart. Your child's doctor will inject your child with contrast dye to see their heart more clearly. Your child's doctor will give them medicine to help relax and prevent pain (sedation). Your child's blood pressure and oxygen levels will be checked during the procedure.

Treatment will depend on your child's symptoms, age, and general health. It will also depend on how severe the condition is.

All children with an AV canal defect will need to have surgery to fix it. They may also need other treatments.

Many children will need medicine to help their heart and lungs work better, such as:

• Digoxin. This medicine helps the heart pump better.
• Diuretics. This medicine helps the kidneys remove extra fluid from the body.
• ACE (angiotensin-converting enzyme) inhibitors. These medicines make it easier for the heart to pump blood to the body.

Babies may become tired when feeding. This may stop them from eating enough to gain weight. Your child may need:

• High-calorie formula or breast milk. Your child may need special nutritional supplements added to their formula or pumped breast milk.
• Supplemental tube feedings. Your child may need to be fed through a tube. This small, flexible tube passes through the nose, down into the esophagus, and into the stomach. Your child may have tube feedings in addition to or instead of formula or breast milk.

Children with heart problems are at risk for infections of the lining of the heart and heart valves (bacterial endocarditis). Tell all of your child's doctors that your child has an AV canal defect. Your child may need to take antibiotics before medical tests or procedures to prevent infections.

Your child will need surgery to repair the septal openings and heart valves. This is done to stop their lungs from becoming damaged further. Your child's heart doctor will decide when the best time for surgery is. After the surgery, your child's heart doctor may give them antibiotics. This is to prevent infections after they leave the hospital.

Most children have surgery by the age of 6 months. Children with Down syndrome may develop lung problems earlier and may need to have surgery at a younger age.

If left untreated, an AV canal defect can cause several problems.

This is because of higher than normal pressure in the blood vessels and lungs. This lung damage doesn't happen right away. The lungs are able to cope with extra volume of blood for a while.

As the arteries in the lungs get thicker, less blood will flow from the left to the right side of the heart and to the lungs. It will be easier for oxygen-poor (blue) blood to flow from the right side into the left side of the heart and on to the rest of the body. This stops the body from getting enough oxygen. This causes a blue coloring to your child's skin, lips, and nails.

Bacteria in the bloodstream can cause infections of the lining of the heart and heart valves.

All children with an AV canal defect will need to have surgery to repair it. Before surgery, it's important to follow the advised medicine and feeding schedules.

Many children who have had an AV canal defect will live active, healthy lives after their surgery. Their activity levels, appetite, and growth will return to normal over time. Some children will still have heart valve problems after surgery. They may eventually need another surgery to repair or replace the leaky or blocked valve or valves. Ask your child's doctor about your child's outlook.

• An AV canal defect is a heart problem that children can be born with.
• Children with an AV canal defect need to have surgery to repair it.
• Many children who have had an AV canal defect will live active, healthy lives after their surgery.

Tips to help you get the most from a visit to your child's doctor:

• Know the reason for the visit and what you want to happen.
• Before your visit, write down questions you want answered.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you for your child.
• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
• Ask if your child's condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if your child does not take the medicine or have the test or procedure.
• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your child's doctor after office hours and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.