Atrioventricular canal defect, also called atrioventricular septal defect, is a combination of heart problems affecting the center of the heart. The heart condition is present at birth (congenital heart defect). Children born with this condition have a hole between the heart's chambers and problems with the valves that control blood flow in the heart.

Atrioventricular canal defect allows extra blood to flow to the lungs. The extra blood forces the heart to work too hard, causing the heart muscle to enlarge.

Untreated, atrioventricular canal defect can cause heart failure and high blood pressure in the lungs. Doctors generally recommend surgery during the first year of life to close the hole in the heart and to reconstruct the valves.

Atrioventricular canal defect (atrioventricular septal defect) may also be called endocardial cushion defect. The condition is often associated with Down syndrome.

Atrioventricular canal defect can involve only the two upper chambers of the heart (partial defect) or all four chambers (complete defect). In both types, extra blood flows into the lungs. Signs and symptoms depend on whether the defect is partial or complete.

Complete defect

Signs and symptoms of a complete atrioventricular canal defect usually develop in the first several weeks of life. These signs and symptoms are generally similar to those associated with heart failure and might include:

• Difficulty breathing or rapid breathing
• Wheezing
• Fatigue
• Lack of appetite
• Poor weight gain
• Pale skin color
• Bluish discoloration of the lips and skin
• Excessive sweating
• Irregular or rapid heartbeat
• Swelling in the legs, ankles and feet (edema)

Partial defect

Signs and symptoms of a partial atrioventricular canal defect might not appear until early adulthood and might be related to complications that develop as a result of the defect. These signs and symptoms can include:

• Abnormal heartbeat (arrhythmia)
• Shortness of breath
• High blood pressure in the lungs (pulmonary hypertension)
• Heart valve problems
• Heart failure

Atrioventricular canal defect occurs before birth when a baby's heart is developing. Doctors aren't exactly sure what causes atrioventricular canal defect. Down syndrome might increase a person's risk of this congenital heart defect.

The normal heart

The heart is divided into four chambers, two on the right and two on the left.

The right side of the heart moves blood into vessels that lead to the lungs, where the blood receives oxygen. The oxygen-rich blood flows back to your heart's left side and into the body's main artery (aorta). From there, the blood flows to the rest of your body.

Valves control the flow of blood into and out of the chambers of your heart. These heart valves open to let blood in and close to keep blood from flowing backward.

What happens in atrioventricular canal defect

Partial atrioventricular canal defect:

• A hole in the heart's wall (septum) separates the upper chambers (atria).
• Often the valve between the upper and lower left chambers (mitral valve) is abnormal and leaks blood (mitral valve regurgitation).

Complete atrioventricular canal defect:

• There's a large hole in the center of the heart where the walls between the upper chambers (atria) and the lower chambers (ventricles) meet. Oxygen-rich and oxygen-poor blood mix through that hole.
• Instead of separate valves on the right and left, there's one large valve between the upper and lower chambers.
• The abnormal valve leaks blood into the ventricles.
• The heart is forced to work harder and becomes larger.

Things that might increase a baby's risk of developing atrioventricular canal defect include:

• Down syndrome in the baby
• German measles (rubella) or another viral illness in the mother during early pregnancy
• Poorly controlled diabetes during pregnancy
• Drinking alcohol during pregnancy
• Smoking during pregnancy
• Certain medications taken during pregnancy — talk to your doctor before taking any drugs while you're pregnant or trying to become pregnant
• Having a parent who had a congenital heart defect

Possible complications of atrioventricular canal defect include:

• Enlargement of the heart. Increased blood flow through the heart forces it to work harder than normal, causing it to become larger.
• High blood pressure in the lungs (pulmonary hypertension). When there is a hole in the heart that allows mixing of oxygenated (red) and deoxygenated (blue) blood, the amount of blood that goes to the lungs is increased. As a result, pressure builds up in the lungs.
• Respiratory tract infections. A person with atrioventricular canal defect may have repeated lung infections.
• Heart failure. Untreated, atrioventricular canal defect usually makes the heart unable to pump enough blood to meet the body's needs.

Treatment greatly improves the outlook for children with atrioventricular canal defect. However, some children who have surgery to treat atrioventricular canal defect may have heart problems when they are adults, including:

• Leaky heart valves
• Narrowing of the heart valves
• Abnormal heart rhythm
• Breathing problems due to lung damage

Pregnancy

Women who had an atrioventricular canal defect that was surgically corrected before any permanent lung damage occurred can generally expect to have normal pregnancies. However, pregnancy isn't recommended in women who had serious heart or lung damage before atrioventricular canal defect surgery.

Evaluation by a cardiologist trained in congenital heart disease (adult congenital cardiologist) is recommended for women with repaired or unrepaired atrioventricular canal defect before they attempt pregnancy.

Atrioventricular canal defect might be detected in a baby before birth using ultrasound and special heart imaging.

After birth, signs and symptoms of complete atrioventricular canal defect are usually noticeable within the first few weeks. When listening to your baby's heart, your doctor might hear an abnormal whooshing sound (heart murmur).

If your baby is having signs and symptoms of atrioventricular canal defect, your doctor might recommend the following tests:

• Electrocardiogram (ECG or EKG). Electrical signals are recorded as they travel through the heart. Your doctor can look for patterns that show abnormal heart function.
• Echocardiogram. Sound waves are used to create pictures of the heart in motion. An echocardiogram can reveal a hole in the heart, abnormal heart valves and abnormal blood flow through the heart.
• Chest X-ray. A chest X-ray can show an enlarged heart.
• Cardiac catheterization. A thin, flexible tube (catheter) is inserted into a blood vessel in the groin and up to the heart. A dye injected through the catheter makes the heart structures show up more clearly on X-rays. The catheter also allows the doctor to measure pressure in the chambers of the heart and in the blood vessels.

Surgery is needed to repair a complete or partial atrioventricular canal defect. More than one surgery may be needed. Surgery to correct atrioventricular canal defect involves using one or two patches to close the hole in the heart wall. The patches stay in the heart permanently, becoming part of the heart's wall as the heart's lining grows over them.

Other surgeries depend on whether you have a partial or complete defect and what other heart problems you may have. For a partial atrioventricular canal defect, surgery to repair the mitral valve is needed so that the valve will close tightly. If repair isn't possible, the valve might need to be replaced.

For a complete atrioventricular canal defect, surgeons separate the abnormal large single valve between the upper and lower heart chambers into two valves. If separating the single valve isn't possible, heart valve replacement of both the tricuspid valve and the mitral valve might be needed.

After surgery

If the heart defect is repaired successfully, you or your child will likely have no activity restrictions.

You or your child will need lifelong follow-up care with a cardiologist trained in congenital heart disease. Your cardiologist will likely recommend a follow-up exam once a year or more frequently if problems, such as a leaky heart valve, remain.

Adults whose congenital heart defects were treated in childhood may need care from a cardiologist trained in adult congenital heart disease (adult congenital cardiologist) throughout life. Special attention and care may be needed around the time of any future surgical procedures, even those that do not involve the heart.

You or your child might also need to take preventive antibiotics before certain dental and other surgical procedures if either of you:

• Have remaining heart defects after surgery
• Received an artificial heart valve
• Received artificial (prosthetic) material during heart repair
• Will receive a heart valve prosthetic in the next six months

The antibiotics are used to prevent inflammation and infection of the lining of the heart (endocarditis).

Many people who have corrective surgery for atrioventricular canal defect don't need additional surgery. However, some complications, such as heart valve leaks, may require treatment.

Having a congenital heart defect or caring for a child with a congenital heart defect can be challenging. To help make it easier:

• Seek support. Ask for help from family members and friends. Talk with your or your child's cardiologist about support groups and other types of assistance that are available near you.
• Record your or your child's health history. Write down medications, surgery and other procedures and the dates they were performed. Include the medical report from the surgeon, and any other important information about your or your child's care. This information will be useful for doctors who are unfamiliar with you or your child. It will also help your child transition from pediatric to adult doctors.
• Talk about your concerns for your child. Many children with atrioventricular canal defect will have no limitations. But talk with the cardiologist about activities that are safe for your child. If some are off-limits, encourage your child in other pursuits rather than focusing on what he or she can't do.

Although every circumstance is different, remember that many children with congenital heart defects grow up to lead healthy lives.

Atrioventricular canal defect generally can't be prevented.

Some heart defects are passed down in families (inherited). If you have a family history of heart defects or if you already have a child with a congenital heart defect, talk with a genetic counselor and a cardiologist before getting pregnant again.

You or your child might be referred to a doctor trained in heart conditions (cardiologist).

What you can do

• Write down any symptoms you or your child has, including any that may seem unrelated to the reason why you scheduled the appointment.
• Make a list of all your medications, vitamins and supplements.
• Write down important medical information, including other health conditions you or your child may have.
• Write down key personal information, including any recent changes or stress in your life.
• Write down questions to ask your doctor.
• Find out if your family has a history of heart disease.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may leave time to go over points you want to spend more time on. You may be asked questions such as:

• When did you first notice symptoms? Do they come and go or do you always have them?
• Does anything seem to improve or worsen these symptoms?
• Do you have a family history of congenital heart disease?
• Did you have diabetes or a viral infection, such as measles, during your pregnancy?
• Did you take any medications during pregnancy?
• Did you use tobacco or smoke during pregnancy?

Questions to ask your doctor

Preparing a list of questions can help you make the most of your time with your doctor. For atrioventricular canal defect, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms or my baby's symptoms?
• What tests are needed? Is there any special preparation for them?
• What kind of treatment do you recommend?
• How can we manage other health problems together with atrioventricular canal defect?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask other questions during your appointment.