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The heart is divided into four chambers. The two upper chambers are called atria and the two lower chambers are called ventricles. The heart contains four 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 and mitral valves. 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 lead to certain heart problems over time. But, it can often be treated.
An AV canal defect is a congenital heart defect. This means it’s 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.
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 enter the right side of the heart. As a result, 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 work even harder.
Children with an AV canal defect usually have symptoms of CHF in infancy. These include:
Poor weight gain and growth
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 will be referred to a pediatric cardiologist. This is a doctor who diagnoses and treats 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.
Electrocardiography (ECG or EKG): The electrical activity of the heart is recorded.
Echocardiography (echo): Sound waves (ultrasound) are used to create a picture of the heart and look for structural defects.
Children with a complete AV canal defect are treated early in infancy with heart surgery. Medications may be prescribed to help manage symptoms until surgery is scheduled. These can include:
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 the heart’s performance.
ACE inhibitors, which make blood vessels relax and allow blood to flow more easily from the heart.
Heart surgery to repair an AV canal defect is performed by a pediatric heart surgeon. The surgery lasts about 4–6 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 medication (sedative and anesthesia) to sleep and not feel pain during surgery. A breathing tube is placed in your child’s trachea (windpipe). 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 sternum (breastbone) to access the heart. The ASD and VSD are repaired with one or two patches. The single AV valve is rebuilt into two 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 7–10 days. When your child is ready to leave the hospital, you’ll be given instructions for home care and follow-up.
Reaction to sedative or anesthesia
Valve insufficiency (leakage of blood through one or both of the new valves back into the atria)
Incomplete closure of the ASD and/or VSD, requiring further treatment
Arrhythmia (abnormal heart rhythm)
Nervous system problems
Abnormal buildup of fluid around the heart and lungs
After heart surgery, call the doctor right away if your child has:
Increased pain, swelling, redness, bleeding, or drainage of an incision site.
In an infant under 3 months old, a rectal temperature of 100.4°F (38.0°C) or higher
In a child 3 to 36 months, a rectal temperature of 102°F (39.0°C) or higher
In a child of any age who has a temperature of 103°F (39.4°C) or higher
A fever that lasts more than 24-hours in a child under 2 years old, or for 3 days in a child 2 years or older
A seizure caused by the fever
Nausea or vomiting.
A cough that won’t go away.
An irregular heartbeat.
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 may be needed later in life.
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.