There are two common types of atrioventricular canal defects - 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.  Both types allow extra blood to circulate to the lungs, causing the heart to enlarge.

Atrioventricular Canal Defect is often associated with Down Syndrome.  Infants with atrioventricular canal defect may have trouble breathing, and they may not grow normally.  If left untreated, atrioventricular canal defect may cause congestive heart failure and high blood pressure in the lungs.  To correct this defect, doctors often recommend surgery during the first year of life to close the hole and reconstruct the valves.

Signs and Symptoms

Signs and symptoms of partial atrioventricular canal defect may not appear until later in life, often in the 20s and 30s.  When they do become noticeable, signs and symptoms are usually related to complications that develop as a result of the defect, such as abnormal heart rhythm, congestive heart failure and high blood pressure in the lungs.

Causes

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

- A Hole In The Wall
In PAPVR, a hole exists in the wall (septum) that separates the upper chambers and the mitral valve between the upper and lower left chambers that do not close completely.

Risk Factors

Although the exact cause of atrioventricular canal defect is unknown, several factors may increase the risk of your baby being born with this condition.

Children born with Down Syndrome, a genetic condition resulting from an extra 21st chromosome, are at increased risk of congenital heart defects.  Forty-five percent of children with Down Syndrome have congenital heart disease.  Of these, 20 percent to 25 percent have atrioventricular canal defect.

Other factors that may increase the risk of congenital heart defects include:
- A mother who had German measles (rubella) or another viral illness during early pregnancy
- A parent who had a congenital heart defect
- Excessive alcohol consumption during pregnancy
- A mother w ho has diabetes
- Taking some type of medications during pregnancy

When To Seek Medical Advice

Contact your doctor if your baby 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
- Shortness of breath
- Easily tiring
- A persistent cough or wheezing with white or pink blood-tinged phlegm
- Swelling of the legs, ankles or feet
- Swelling of the abdomen
- 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, years or even decades, depending on the extent of the defect.  But, anytime the signs or symptoms above start to appear, seek medical advice.

Screening and Diagnosis

If your baby has a PAPVR, his or her doctor may not detect anything 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.

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.

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.

In some cases, doctors may use cardiac catherization 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 make pressure in the chambers of the heart and in the blood vessels.

Complications

Potential complications of atrioventricular canal defect include:
- Pneumonia
- Enlargement of the heart
- Congestive heart failure
- High blood pressure in the lungs

Complications Later In Life

People who have surgery to correct atrioventricular canal defect sometimes have the following associated conditions later in life:
- Leaky heart valves
- Narrowing of the heart valves
- Heart rhythm abnormalities
- Breathing difficulties associated with damage to the lungs

Common signs and symptoms of these complications include shortness of breath, fatigue, fever, and a rapid, fluttering heartbeat, among others.

Treatment

Surgery is necessary to correct atrioventricular canal defect.  During this procedure, a surgeon closes the hole in the septum with one or two patches.  The patches remain in the heart permanently, becoming a 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.

After Surgery

After corrective surgery, your child will need lifelong follow-up care with a pediatric cardiologist.

Your child will also need to take antibiotics before dental procedures and other surgical procedures to prevent infection.

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.

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, before future pregnancies talk with a genetic counselor and a cardiologist experienced in congenital heart defects.

Coping Skills

Caring for a child with a congenital heart defect can be 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.

- Record your baby's health history - - You may want to write down your child's diagnosis, medications, surgery and other procedures and 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.

- Talk about your concerns - - As your child grows, you may worry about activities in which he or she can safely participate in.  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 then with your child's cardiologist, too.

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