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Atrio Ventricular Septal Defect (AVSD)

Atrioventricular canal defect is a combination of heart problems resulting in a defect in the centre of the heart. The condition occurs when there's a hole between the heart's chambers and problems with the valves that regulate blood flow in the heart.

Sometimes called endocardial cushion defect or atrioventricular septal defect, atrioventricular canal defect is present at birth (congenital). The condition is often associated with Down syndrome.

Atrioventricular canal defect allows extra blood to flow to the lungs. The extra blood forces the heart to overwork, 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 can involve only the two upper chambers of the heart (partial) or all four chambers (complete). In either type, extra blood circulates in the lungs.

Complete atrioventricular canal defect

Signs and symptoms 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 colour
  • Bluish discoloration of the lips and skin
  • Excessive sweating
  • Irregular or rapid heartbeat
  • Swelling in the legs, ankles and feet (oedema)

Partial atrioventricular canal defect

Signs and symptoms 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 might be detected before birth through 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) caused by turbulent blood flow.

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

  • Electrocardiogram (ECG or EKG). Electrical signals are recorded as they travel through the heart. Your doctor can look for patterns that indicate abnormal heart function.
  • Echocardiogram. Sound waves produce live-action images of the heart. Echocardiogram can reveal a hole in the heart and abnormal heart valves, as well as abnormal blood flow through the heart.
  • Chest X-ray. The image can show evidence of 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 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.


Atrioventricular canal defect occurs before birth when a baby's heart is developing. Some factors, such as Down syndrome, might increase the risk of atrioventricular canal defect. But the cause is generally unknown.

The normal-functioning heart

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

The right side of your heart moves blood into vessels that lead to the lungs. There, oxygen enriches the blood. The oxygen-rich blood flows back to your heart's left side and is pumped into a large vessel (aorta) that 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 close to keep blood from flowing backward.

What happens in atrioventricular canal defect

In partial atrioventricular canal defect:

  • There's a hole in the wall (septum) that separates the upper chambers (atria) of the heart.
  • Often the valve between the upper and lower left chambers (mitral valve) also has a defect that causes it to leak (mitral valve regurgitation).

In complete atrioventricular canal defect:

  • There's a large hole in the centre of the heart where the walls between the 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 enlarges.

Risk factors

Factors that might increase a baby's risk of developing atrioventricular canal defect before birth include:

  • Down syndrome
  • German measles (rubella) or another viral illness during a mother's early pregnancy
  • Alcohol consumption during pregnancy
  • Poorly controlled diabetes 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


Complications of atrioventricular canal defect can include:

  • Enlargement of the heart. Increased blood flow through the heart forces it to work harder than normal, causing it to enlarge.
  • Pulmonary hypertension. When there is a hole (defect) that allows mixing of oxygenated (red) and deoxygenated (blue) blood, the amount of blood that goes to the lungs is increased. This results in pressure build-up in the lungs, causing high blood pressure in the lungs.
  • Respiratory tract infections. Atrioventricular canal defect can cause recurrent bouts of lung infections.
  • Heart failure. Untreated, atrioventricular canal defect usually results in the heart's inability to pump enough blood to meet the body's needs.

Complications later in life

Treatment greatly improves the outlook for children with atrioventricular canal defect. However, some children who have corrective surgery may still be at risk later in life of:

  • Leaky heart valves
  • Narrowing of the heart valves
  • Abnormal heart rhythm
  • Breathing difficulties associated with lung damage

Common signs and symptoms of these complications include:

  • Shortness of breath
  • Fatigue
  • Rapid, fluttering heartbeat

Additional surgery might be needed to correct complications of atrioventricular canal defect.



Atrioventricular canal defect generally can't be prevented.

Heredity may play a role in some heart defects. 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.

Immunization with rubella vaccine has been one of the most effective preventive strategies against congenital heart defects.



Surgery is needed to repair complete and partial atrioventricular canal defects. The procedure involves closing the hole in the wall (septum) between the heart chambers with one or two patches. The patches stay in the heart permanently, becoming part of the septum as the heart's lining grows over them.

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

For a complete atrioventricular canal defect, surgery also includes separation of the large single valve that separates the upper and lower chambers of the heart into two valves, on both the left and right sides of the repaired septum. If separating the single valve isn't possible, heart valve replacement of both the tricuspid and mitral valves might be needed.


After Surgery

If the heart defect is repaired successfully, your child will likely lead a normal life, often with no activity restrictions.

However, 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 as children 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 procedures, such as an operation which does not involve the heart.

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

  • Has remaining heart defects after surgery
  • Received an artificial heart valve
  • Received artificial (prosthetic) material during heart repair

The antibiotics are used to prevent a bacterial 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.



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 if serious heart or lung damage occurred before 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.