Atrioventricular canal defect


Atrioventricular canal defect is a mix of problems affecting the center of the heart. The heart condition is present at birth. That means it's a congenital heart defect. Children born with this condition have a hole in the wall between the heart's chambers. They also have 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 grow larger.

Untreated, atrioventricular canal defect can cause heart failure and high blood pressure in the lungs. Treatment usually involves surgery during the first year of life to close the hole in the heart and to repair the valves.

Other names for this condition are:

  • Atrioventricular septal defect (AVSD)
  • Endocardial cushion defect


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

Complete defect

The condition affects all of the heart's chambers. Symptoms of a complete atrioventricular canal defect usually develop in the first weeks of life. Symptoms are generally similar to those of heart failure. They may include:

  • Blue or gray skin color due to low oxygen levels
  • Difficulty breathing or rapid breathing
  • Excessive sweating
  • Fatigue
  • Irregular or rapid heartbeat
  • Lack of appetite
  • Poor weight gain
  • Swelling in the legs, ankles and feet
  • Wheezing

Partial defect

The condition affects only the two upper heart chambers. Symptoms of a partial atrioventricular canal defect may not appear until early adulthood. The symptoms may be due to complications such as heart valve problems, high blood pressure in the lungs or heart failure. Symptoms may include:

  • Fatigue and weakness
  • Nausea and lack of appetite
  • Persistent cough or wheezing
  • Rapid or irregular heartbeat, also called an arrhythmia
  • Reduced ability to exercise
  • Shortness of breath
  • Swelling in the legs, ankles and feet
  • Chest pressure or pain


Atrioventricular canal defect occurs before birth when a baby's heart is developing. Experts aren't sure of the cause. Having Down syndrome might increase the risk.

How the heart works

To understand congenital heart defects, it may be helpful to know how the heart typically works.

The heart is divided into chambers. The two upper chambers are called the atria. The two lower chambers are called the ventricles.

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 the heart's left side and into the body's main artery, called the aorta. From there, the blood flows to the rest of the body.

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

What happens in atrioventricular canal defect

In a partial atrioventricular canal defect:

  • There's a hole in the heart's wall between the upper chambers.
  • There are also changes in the tricuspid and mitral valves.
  • The changes prevent the valves from closing all the way.
  • Blood can move the wrong way through the irregular valve opening.
  • The mitral valve between the upper and lower left chambers is most often affected.

In a complete atrioventricular canal defect:

  • There's a large hole in the center of the heart. The hole is where the walls between the upper and the lower chambers meet.
  • Oxygen-rich and oxygen-poor blood mix through the hole.
  • There's one large valve between the heart's upper and lower chambers, instead of separate ones.
  • Blood leaks through the one large valve into the lower heart chambers.
  • The heart must work harder to pump blood. The heart becomes larger.
Chambers and valves of the heart
A typical 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 out of the heart. The heart valves, which keep blood flowing in the right direction, are gates at the chamber openings.
Illustration showing atrioventricular canal defect
Atrioventricular canal defect is a type of congenital heart defect. A person born with atrioventricular canal defect has a hole in the wall separating the heart's chambers and problems with the heart valves. The condition may be partial, involving only the two upper chambers, or complete, involving all four chambers.

Risk factors

Things that might increase the risk of atrioventricular canal defect include:

  • Genetics. Congenital heart disease appears to run in families. It's associated with many genetic syndromes. For instance, children with Down syndrome often have heart problems present at birth.
  • German measles, also called rubella. Having rubella during pregnancy may affect how the baby's heart develops while in the womb.
  • Diabetes. Poorly controlled diabetes during pregnancy may affect a baby's heart development. Gestational diabetes generally doesn't increase the risk of congenital heart disease.
  • Alcohol use. Drinking alcohol while pregnant has been linked to an increased risk of heart defects in the baby.
  • Smoking. If you smoke, quit. Smoking during pregnancy increases the risk of congenital heart defects in the baby.
  • Some medicines. Taking certain medications while pregnant may cause heart problems and other birth defects in the baby. Always tell your health care provider about the medications you take.


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. This condition is also called pulmonary hypertension. A hole in the heart lets oxygen-rich blood mix with oxygen-poor blood. The lungs get too much blood. Pressure builds up in the lungs.
  • Respiratory tract infections. A hole in the heart can lead to repeated lung infections.
  • Heart failure. If atrioventricular canal defect is not treated, the heart can't pump enough blood to meet the body's needs.

Treatment greatly improves the outlook for children with atrioventricular canal defect. But complications may still occur later in life. They may include:

  • Breathing problems due to lung damage
  • Irregular heart rhythms
  • Leaky heart valves, also called valve regurgitation
  • Narrowing of the heart valves


Those who had atrioventricular canal defect surgery before permanent lung damage occurred are often able to have a successful pregnancy. Pregnancy is not recommended if you had serious heart or lung damage before atrioventricular canal defect surgery.

Before becoming pregnant, talk to a heart doctor trained in congenital heart disease about the possible risks and complications. This type of care provider is called an adult congenital cardiologist. Together you can discuss and plan for any special care needed during pregnancy.


Atrioventricular canal defect might be diagnosed in a baby before birth during a pregnancy ultrasound or special heart imaging.

After birth, symptoms of complete atrioventricular canal defect are usually noticeable within the first weeks. When listening to a baby's heart, a health care provider might hear a whooshing sound. The sound is called a heart murmur.

Tests to diagnose atrioventricular canal defect may include:

  • Pulse oximetry. A sensor placed on the fingertip records the amount of oxygen in the blood. Too little oxygen may be a sign of a heart or lung problem.
  • Electrocardiogram. Also called an ECG or EKG, this noninvasive test records the electrical activity of the heart. Sticky patches with sensors are placed on the chest. Wires connect the patches to a computer, which displays results.
  • Echocardiogram. Sound waves are used to create pictures of the heart in motion. An echocardiogram can reveal a hole in the heart or heart valve issues. It also shows how blood flows through the heart.
  • Chest X-ray. A chest X-ray shows the condition of the heart and lungs. It can show if the heart is enlarged, or if the lungs contain extra blood or other fluid. These could be signs of heart failure.
  • Cardiac catheterization. A thin, flexible tube called a 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. During the procedure, a health care provider can measure pressure in different parts of the heart.


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

Other surgeries depend on whether the defect is partial or complete and what other heart problems exist.

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 large single valve between the upper and lower heart chambers into two valves. If this isn't possible, the mitral and tricuspid valves might need to be replaced.

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

Follow-up care

After congenital heart defect surgery, regular checkups are needed for life by a doctor trained in heart diseases. This type of care provider is called a cardiologist. Your provider will tell you how often you need an appointment or imaging tests.

Adults with a congenital heart defect treated in childhood may need care from an adult congenital cardiologist. Special attention and care may be needed around the time of future surgical procedures, even those that do not involve the heart.

Preventive antibiotics

Sometimes, a congenital heart defect can increase the risk of infection in the lining of the heart or heart valves. This infection is called infective endocarditis. You or your child might need to take preventive antibiotics before certain dental and other surgical procedures if either of you:

  • Has remaining heart problems after surgery
  • Received an artificial heart valve
  • Received artificial — or prosthetic — material during heart repair

Ask your or your child's health care provider if preventive antibiotics are necessary.

Coping and support

Many children with heart problems present at birth grow up to lead healthy lives.

But having a congenital heart defect or caring for a child with one can be challenging. These tips may be helpful.

  • Seek support. You may find that talking with other people who've experienced the same situation brings you comfort and encouragement. Ask your health care provider if there are any support groups in your area.
  • 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 other important information about your or your child's care. This information will be useful for health care providers who are unfamiliar with you or your child. It will also help your child transition from pediatric to adult providers.
  • Ask about sports and other activities. Many people with successful repair of a congenital heart defect usually have no activity restrictions. But some people with a congenital heart defect may need to limit exercise or sports activities. Your health care provider can tell you which sports and types of exercise are safe for you or your child.


There is no known prevention for atrioventricular canal defect.

Some heart problems are passed down in families, which means they are inherited. If you have a family or personal history of congenital heart disease, talk with a genetic counselor and a cardiologist before getting pregnant.

Preparing for your appointment

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

What you can do

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

What to expect from your doctor

Your health care provider is likely to ask many questions, such as:

  • When did you notice symptoms? Are they continuous or occasional?
  • What, if anything, makes the symptoms worse or better?
  • Did you have diabetes or a viral infection, such as measles, during pregnancy?
  • Did you take medications during pregnancy?
  • Did you use tobacco or alcohol during pregnancy?

Questions to ask your doctor

For atrioventricular canal defect, some questions might include:

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

Don't hesitate to ask other questions you have.

Last Updated Sep 13, 2022

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