Atrioventricular septal defect (AVSD)

Atrioventricular septal defect (AVSD)—also called atrioventricular canal defect or endocardial cushion defect—is a complex heart defect made up of several structural problems.

A healthy heart is a strong, muscular pump that pushes blood through the circulatory system to carry oxygen and nutrients to the body. The heart has four chambers — two on the right and two on the left. Blood is pumped through these chambers and regulated by valves that open and close like tiny doors, so that blood can move in only one direction.

After its trip through the body to deliver oxygen, blood is a blue color because it’s no longer oxygen-rich. The blue blood returns to the heart through the right chambers and is pumped through the pulmonary artery into the lungs. In the lungs, it picks up more oxygen and becomes bright red. It then goes back through the pulmonary vein to the left chambers and is pumped through the aorta and out into the body again.

In a heart with AVSD, several defects prevent the heart from working normally:

Atrial septal defect: A hole that allows oxygen-rich (red) blood from the left atrium to mix with oxygen-poor (blue) blood in the right atrium.
Ventricular septal defect: Another hole, which allows oxygen-rich (red) blood from the left ventricle to mix with oxygen-poor (blue) blood in the right ventricle.
Abnormalities of the mitral or tricuspid valves: These defects allow blood that should flow forward through the system to instead flow backward.

There are two types of AVSD:

Partial AVSD: A hole exists in the wall between the heart’s upper chambers, and the valve between the left chambers does not close completely.
Complete AVSD: A large hole exists in the center of the heart where the walls between the upper and lower chambers meet. Instead of two separate valves on the right and left, one large common valve sits between the upper and lower chambers. Often, this valve doesn’t close tightly.

Either way, the AVSD allows oxygen-rich and oxygen-poor blood to mix through the hole in the wall of the heart and the abnormal valves leak blood into the heart’s lower chambers. These problems make the heart work harder, causing it to enlarge.

As a result, infants with AVSD may have trouble breathing and they may not grow normally. Left untreated, the potential complications of AVSD also include:

Pneumonia: Untreated AVSD may lead to repeated problems with this lung infection.
Enlargement of the heart (cardiomegaly): Increased blood flow through the heart forces it to work harder, which causes it to grow larger.
Congestive heart failure: Left untreated, AVSD causes congestive heart failure, a condition in which the heart cannot pump enough blood to meet the body’s needs.
High blood pressure in the lungs (pulmonary hypertension): When the heart weakens and can’t pump enough blood, this increases blood pressure in the heart and lungs. High blood pressure in the blood vessels in the lungs can cause lung damage.
Bacterial endocarditis: A serious infection of the lining of the heart.

What causes AVSD?

Atrioventricular septal defect occurs during the first eight weeks of fetal development, when the heart is forming.

The heart begins as a hollow tube. Then septa, or walls, form that divide the tube into four chambers. AVSD occurs when the walls between the right and left sides of the heart do not form incompletely, leaving openings that should not be there. Additionally, the valves that separate the upper and lower chambers of the heart do not develop properly, either.

AVSD accounts for about 4-10% of all congenital (from birth) heart defects, occurring in about two out of every 10,000 live births. It appears equally in boys and girls.

Although the exact cause of AVSD is unknown and, in most cases, it cannot be prevented, several risk factors may increase the risk of your baby being born with the condition. Children born with Down syndrome are at increased risk of congenital heart defects. Forty-five percent of children with Down syndrome have congenital heart disease. Of these, 20-25% percent have AVSD.

Other risk factors include a mother who had a viral illness (such as measles) while pregnant, a mother who has diabetes, alcohol abuse during pregnancy, the use of some medications during pregnancy, and a parent who had a congenital heart defect. Fourteen percent of mothers with an atrioventricular defect give birth to a child with the condition.

What are the signs and symptoms?

The size of the openings will affect the type and severity of symptoms, as well as the age at which they first occur. The larger the openings, the more serious the condition.

If your baby has complete AVSD, the signs and symptoms usually become clear in the first few weeks of life. Symptoms vary for each child, but commonly include:

Difficult or congested breathing
Poor appetite or poor weight gain
Lack of interest or unusual tiredness during feeding
Cyanosis: A blue tone to the skin, lips, or nails
Pale, cool or sweaty skin
A heartbeat that is too fast

Complete AVSD may lead to congestive heart failure. If your baby develops congestive heart failure, the signs and symptoms may include:

Fatigue, weakness, and lack of alertness
Sudden weight gain or swelling of the legs, ankles, feet or belly
A heartbeat that is irregular or too fast
Coughing or wheezing that doesn’t go away, sometimes with white or pink phlegm that has blood in it

If your child has partial AVSD, signs and symptoms may not become clear for weeks, months, or even years. Some people with partial AVSD don’t show signs until they are adults in their 20s or 30s, whey they may develop conditions such as abnormal heart rhythm, congestive heart failure and high blood pressure in the lungs.

Your baby’s doctor may also suspect partial AVSD if he or she hears a heart murmur — an abnormal whooshing noise, heard through a stethoscope exam, which may indicate a problem with blood flow. Most heart murmurs are called “innocent heart murmurs.” Children with innocent heart murmurs do not have a heart defect and do not experience heart problems. However, if a heart murmur is present along with other symptoms, your doctor may want to investigate further by ordering other tests.

How is AVSD diagnosed?

Typically, children with AVSD need corrective surgery by the age of six months. Children with both AVSD and Down syndrome may develop lung problems earlier than other children, and may need surgery at an earlier age.

Many children who undergo corrective surgery for AVSD don’t need further surgery and will live healthy lives, with activity levels, appetite and growth will eventually returning to normal.

A clear diagnosis is the first step to treatment. A pediatric cardiologist (a children’s heart doctor) can use several tests to confirm your child’s diagnosis. These tests may include:

Chest X-ray: A beam of electromagnetic energy creates images on film that show the inside structures of your baby’s body.
Cardiac Magnetic Resonance Imaging (MRI): This test produces a three-dimensional image of the heart so you’re your child’s doctors can examine blood flow and functioning of the heart as it is working.
Electrocardiogram (ECG or EKG): This test, conducted by attaching patches with wires (electrodes) to the baby’s skin, records the heart’s electrical activity. It will show if there are abnormal heart rhythms (arrhythmias or dysrhythmias) and heart muscle stress.
Echocardiogram (Echo): This test uses high-pitched sound waves to produce a moving image of the heart on a video screen. It is similar to an ultrasound. 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: During this procedure, your doctor inserts a thin flexible tube (a catheter) into a blood vessel in the groin, then guides it up to the inside of the heart. A dye injected through the catheter makes the heart structures visible on x-ray pictures. The catheter also measures blood pressure and oxygen levels.

How is it treated?

Once diagnosed, your child’s treatment may vary depending on his or her individual needs. Your child’s doctor may prescribe medications to help the heart and lungs function under strain until your child is ready for surgery.

Doctors often recommend surgery during the first year of life to correct AVSD by closing the hole and reconstructing the valves.

Surgical procedures vary, but typically the defects are closed with a patch made from either a piece of the heart’s membrane or a synthetic material. The patch is left in place permanently, and the heart’s lining grows over it in time. The operation has a high likelihood of success.

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 corrective surgery, your child will need lifelong follow-up care with a cardiologist (heart doctor) who specializes in congenital heart disease. Potential complications later in life, such as heart valve leaks, may require additional treatment. Your child will also need to take antibiotics before dental procedures and other surgical procedures to prevent bacterial infection of the heart

About treatment for AVSD at Children’s

Atrioventricular septal defect is treated through Children’s cardiovascular program one of the largest and oldest pediatric cardiovascular programs in the region. Team members consistently achieve treatment results that are among the best in the nation. Each year, care is provided for thousands of the region¹s sickest children with heart conditions, including fetuses, newborns, infants, children, adolescents, and adult, long-term patients with pediatric cardiovascular conditions.