Atrioventricular canal defect, also called atrioventricular septal defect, is a combination of heart problems affecting the center of the heart. The heart condition is present at birth (congenital heart defect). Children born with this condition have a hole between the heart's chambers and 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 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 (atrioventricular septal defect) may also be called endocardial cushion defect. The condition is often associated with Down syndrome.


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

Complete defect

Signs and symptoms of a complete atrioventricular canal defect 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 color
  • Bluish discoloration of the lips and skin
  • Excessive sweating
  • Irregular or rapid heartbeat
  • Swelling in the legs, ankles and feet (edema)

Partial defect

Signs and symptoms of a partial atrioventricular canal defect 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 occurs before birth when a baby's heart is developing. Doctors aren't exactly sure what causes atrioventricular canal defect. Down syndrome might increase a person's risk of this congenital heart defect.

The normal heart

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

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

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

What happens in atrioventricular canal defect

Partial atrioventricular canal defect:

  • A hole in the heart's wall (septum) separates the upper chambers (atria).
  • Often the valve between the upper and lower left chambers (mitral valve) is abnormal and leaks blood (mitral valve regurgitation).

Complete atrioventricular canal defect:

  • There's a large hole in the center of the heart where the walls between the upper chambers (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 becomes larger.

Risk factors

Things that might increase a baby's risk of developing atrioventricular canal defect include:

  • Down syndrome in the baby
  • German measles (rubella) or another viral illness in the mother during early pregnancy
  • Poorly controlled diabetes during pregnancy
  • Drinking alcohol 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


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 (pulmonary hypertension). When there is a hole in the heart that allows mixing of oxygenated (red) and deoxygenated (blue) blood, the amount of blood that goes to the lungs is increased. As a result, pressure builds up in the lungs.
  • Respiratory tract infections. A person with atrioventricular canal defect may have repeated lung infections.
  • Heart failure. Untreated, atrioventricular canal defect usually makes the heart unable to pump enough blood to meet the body's needs.

Treatment greatly improves the outlook for children with atrioventricular canal defect. However, some children who have surgery to treat atrioventricular canal defect may have heart problems when they are adults, including:

  • Leaky heart valves
  • Narrowing of the heart valves
  • Abnormal heart rhythm
  • Breathing problems due to lung damage


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 in women who had serious heart or lung damage before atrioventricular canal defect 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.

July 23, 2021
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