Atrioventricular canal defect

Definition

Atrioventricular canal defect is a combination of several abnormalities in the heart present at birth (congenital abnormalities). This defect, which is sometimes called endocardial cushion defect or atrioventricular septal defect, occurs when there's a hole between the chambers of the heart and problems with the valves that regulate blood flow in the heart.

Atrioventricular canal defect allows extra blood to circulate to the lungs. Ensuing problems overwork the heart and cause it to enlarge.

Atrioventricular canal defect is often associated with Down syndrome. If left untreated, atrioventricular canal defect may cause heart failure and high blood pressure in the lungs. To fix this defect, doctors often recommend surgery during the first year of life to close the hole and reconstruct the valves.

Symptoms

There are two common types of atrioventricular canal defect — partial and complete. The partial form involves only the two upper chambers of the heart. The complete form allows blood to travel freely among all four chambers of the heart. In either type, extra blood circulates in the lungs.

Complete atrioventricular canal defect
Signs and symptoms of complete atrioventricular canal defect usually develop in the first several weeks of life. They include:

• Difficulty breathing (dyspnea)
• Lack of appetite
• Poor weight gain
• Bluish discoloration of the lips and skin (cyanosis)

If your baby has complete atrioventricular canal defect, he or she may also develop signs and symptoms of heart failure, including:

• Fatigue
• Wheezing
• Swelling (edema) in the legs, ankles and feet
• Sudden weight gain from fluid retention
• Excessive sweating
• Decreased alertness
• Irregular or rapid heartbeat

Partial atrioventricular canal defect
Signs and symptoms of a partial atrioventricular canal defect may not appear until early adulthood. When they do become noticeable, signs and symptoms may be related to complications that develop as a result of the defect, and may include:

• Abnormal heartbeat (arrhythmia)
• Heart failure
• High blood pressure in the lungs (pulmonary hypertension)

When to see a doctor
Contact your doctor if you or your child develops any of the following signs or symptoms. These could be indications of heart failure or another complication of atrioventricular canal defect:

• Poor appetite
• Failure to gain weight, in infants and children
• Shortness of breath
• Easily tiring
• Swelling of the legs, ankles or feet
• Bluish discoloration of the skin

Some babies with the partial form of atrioventricular canal defect may not have any signs or symptoms for weeks, months or even years, depending on the extent of the defect. But, anytime the signs or symptoms above start to appear, seek medical care.

Causes

Atrioventricular canal defect occurs during fetal growth when your baby's heart is developing. While some factors, such as Down syndrome, may increase the risk of atrioventricular canal defect, in most cases the cause is unknown.

The normal-functioning heart
Your heart is divided into four chambers, two on the right and two on the left. In performing its basic job — pumping blood throughout your body — your heart uses its left and right sides for different tasks. The right side moves blood into vessels that lead to your lungs. In your lungs, oxygen enriches your blood, which circulates to your heart's left side. The left side of your heart pumps blood into a large vessel called the aorta, which circulates blood to the rest of your body. Valves control the flow of blood into and out of the chambers of your heart. These valves open to allow blood to move to the next chamber or to one of the arteries, and they close to keep blood from flowing backward.

A hole in the wall
In partial atrioventricular canal defect, a hole exists in the wall (septum) that separates the upper chambers (atria) of the heart. Also, the mitral valve between the upper and lower left chambers may not close completely (mitral valve regurgitation).

In complete atrioventricular canal defect, there's a large hole in the center of the heart where the walls between the upper chambers (atria) and lower chambers (ventricles) meet. Instead of two separate valves — one on the right (tricuspid) and one on the left (mitral) — one large common valve exists between the upper and lower chambers. And, this valve may not close tightly.

Oxygen-rich and oxygen-poor blood mix through the hole in the septum, and the abnormal valves leak blood into the heart's lower chambers (ventricles). These problems make the heart work harder, causing it to enlarge.

Chambers and valves of the heart

Chambers and the valves of the heart

A normal heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood ...

Atrioventricular canal defect

Atrioventricular canal defect

Atrioventricular canal defect includes a hole in the wall between the heart's chambers and flaws in the heart's valves. This defect is classified by whether it's partial, involving only the upper two ...

Risk factors

Although the exact cause of atrioventricular canal defect is unknown, several factors may increase the risk of a congenital heart defect, such as:

• Down syndrome in the baby. Down syndrome is a genetic condition resulting from an extra 21st chromosome.
• German measles (rubella) or another viral illness during early pregnancy.
• Having a parent who had a congenital heart defect.
• Drinking too much alcohol during pregnancy.
• Poorly controlled diabetes during pregnancy.
• Taking some types of medications, such as the acne drug isotretinoin (Accutane), during pregnancy. Check with your doctor before taking any drugs while you're pregnant and even when you're trying to get pregnant.

Complications

Treating an atrioventricular canal defect helps your child avoid potential complications, such as:

• Pneumonia. If your baby has an untreated atrioventricular canal defect, he or she may have recurrent bouts of pneumonia — a serious lung infection.
• Enlargement of the heart (cardiomegaly). Increased blood flow through the heart forces it to work harder than normal, causing it to enlarge.
• Heart failure. Untreated, atrioventricular canal defect will usually result in heart failure — a condition in which the heart is unable to pump enough blood to meet the body's needs.
• High blood pressure in the lungs (pulmonary hypertension). When the heart's left ventricle weakens and can't pump out enough blood, the increase in pressure backs up through the pulmonary veins to the arteries in the lungs, causing high blood pressure in the lungs.

Complications later in life
Although treatment greatly improves the outlook for children with atrioventricular canal defect, some who have corrective surgery may still be at risk of the following associated conditions later in life:

• Leaky heart valves (regurgitation)
• Narrowing of the heart valves (stenosis)
• Heart rhythm abnormalities (arrhythmias)
• Breathing difficulties associated with damage to the lungs (pulmonary vascular disease)

Common signs and symptoms of these complications include shortness of breath, fatigue and a rapid, fluttering heartbeat, among others. In some cases, such as a leaky heart valve, a second surgery may be needed.

Preparing for your appointment

You're likely to first mention your concerns to your child's doctor or, in the case of a partial defect that's gone unnoticed into adulthood, your primary care physician. However, you or your child may then be referred to a doctor who specializes in disorders of the heart (cardiologist).

Because appointments can be brief, and there's often a lot of ground to cover, it's a good idea to arrive well prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you or your child experiences, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Make a list of all medications, vitamins and supplements that you or your child takes. Write down the dose usually taken, as well.
• Write down questions to ask your doctor.

Preparing a list of questions can help you make the most of your time with your doctor, and ensure that you cover all of the points that are important to you. For atrioventricular canal defect, some basic questions to ask your doctor include:

• What's the most likely cause of my or my baby's symptoms?
• Are there other possible causes for these symptoms?
• What kinds of tests are needed? Do these tests require any special preparation?
• What treatments are available for atrioventricular canal defect, and which do you recommend?
• What are the risks of surgery?
• Are there any alternatives to surgery?
• My child or I have other health conditions. How can we best manage these conditions together?
• Are there any activity restrictions after the surgery?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

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

What to expect from your doctor
Your doctor or your child's doctor is likely to ask you a number of questions, such as:

• When did you or your child first notice symptoms?
• Have the symptoms been continuous or occasional?
• Does anything seem to improve these symptoms?
• What, if anything, appears to worsen the symptoms?
• Is there a family history of congenital heart disease?

Tests and diagnosis

If your baby has a partial atrioventricular canal defect, his or her doctor may not detect that anything's wrong right away. However, if your baby has a complete atrioventricular canal defect, signs and symptoms usually become noticeable within the first few weeks of life.

Tests that help diagnose an atrioventricular canal defect include:

• Physical exam. Your baby's doctor may suspect a heart defect such as atrioventricular canal defect if your baby is having trouble breathing or having difficulty feeding and gaining weight. Your doctor may also suspect a heart defect if he or she hears a heart murmur — an abnormal whooshing sound caused by turbulent blood flow.
• Echocardiogram. Doctors typically use an echocardiogram to diagnose atrioventricular canal defect. This test uses high-pitched sound waves that bounce off the heart to produce moving images that the doctor can view on a video screen. In a baby with atrioventricular canal defect, the echocardiogram reveals a hole in the wall between the heart chambers and abnormal valves. Because this test can track blood flow, it also shows blood moving through the hole from the left side to the right side of the heart, allowing oxygen-rich and oxygen-poor blood to mix.
• Cardiac catheterization. In some cases, doctors may use cardiac catheterization to diagnose atrioventricular canal defect. During this procedure, the doctor inserts a thin flexible tube (catheter) into an artery or vein in the groin and advances it up to the heart. A dye is injected through the catheter to make the heart structures visible on X-ray pictures. The catheter also allows the doctor to measure pressure in the chambers of the heart and in the blood vessels.

Treatments and drugs

Surgery is necessary to fix both complete and partial atrioventricular canal defects. During the procedure, the hole in the septum is closed using one or two patches. The patches remain in the heart permanently, becoming part of the septum as the heart's lining grows over it.

For a partial atrioventricular canal defect, the surgery also involves repair of the mitral valve so it will close tightly. If repair isn't possible, the valve may need to be replaced instead.

If your baby has complete atrioventricular canal defect, the surgery also includes separation of the single valve into two valves, one on the left side and one on the right side of the repaired septum. If reconstruction of the single valve into two valves isn't possible, heart valve replacement may be necessary.

After surgery
If the atrioventricular canal defect has been successfully repaired with surgery, your child will likely lead a normal life, often with no activity restrictions.

However, your child will need lifelong follow-up care with a heart doctor (cardiologist) who specializes in congenital heart disease. The recommendation for follow-up is usually once a year, unless you have lingering problems, such as a leaky heart valve. In that case, follow-up will be more frequent.

Your child may also need to take preventive antibiotics before certain dental procedures and other surgical procedures if he or she is at risk of severe complications of endocarditis, a bacterial infection of the lining of the heart. Typically, this is when your child has some remaining defects after surgery, has received an artificial valve or has had repair with artificial (prosthetic) material.

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.

Pregnancy
When an atrioventricular canal defect has been surgically corrected before any permanent lung damage has occurred, women can generally expect to have normal pregnancies. Pregnancy is not recommended, however, if serious heart or lung damage occurred before surgery. An evaluation by a cardiologist is advised before women with repaired or unrepaired atrioventricular canal defect attempt pregnancy.

Coping and support

Caring for a child with a congenital heart defect can be scary and challenging. Here are some strategies that may help make it easier:

• Seek support. Ask for help from family members and friends. Talk with your child's cardiologist about support groups and other types of assistance that are available near you.
• Record your baby's health history. You may want to write down your child's diagnosis, medications, surgery and other procedures and the dates they were performed, the name and phone number of your child's cardiologist, and any other important information about your child's care. It's also helpful to include a copy of the operative report from your child's surgeon in your records. This information will help you recall the care your child has received, and it will be useful for doctors who are unfamiliar with your baby to review his or her health history. This information will also help as your child transitions from pediatric doctors to adult doctors.
• Talk about your concerns. As your child grows, you may worry about activities in which he or she can safely participate. Many children will have no limitations, but talk with the cardiologist about which activities are best 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. If other issues about your child's health concern you, discuss them with your child's cardiologist, too.

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

Prevention

In most cases, atrioventricular canal defect can't be prevented. 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.