Atrioventricular Canal Defect in Children

  • If your infant or child has been diagnosed with atrioventricular canal defect (AV canal), an understanding of the condition will help you to cope with this unusual but treatable  congenital (present at birth) heart defect.

    A complete atrioventricular canal defect is actually a combination of several closely associated heart problems that result in a large defect in the center of the heart:

    • Defects include holes such as atrial septal defect (ASD) and  ventricular septal defect (VSD), and abnormalities of the atrioventricular valves (usually mitral and tricuspid).
    • Blood can move freely among the four heart chambers, mixing oxygen-rich (red) blood with oxygen-poor (blue) blood.
    • AV canal occurs in two out of 10,000 births.
    • The condition is common in children with    Down syndrome (about 20%).
    • Surgery in the first six months of life is often necessary to correct the defects.
    • After surgery, most children lead healthy lives but will need lifelong follow-up care.
    • A small proportion (~10%) will need additional surgery later in life

    Comparison with normal heart

    In a normal heart, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs, where it receives oxygen. And oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, then is pumped through the aorta out to the body.

    AVC Heart

    A cluster of defects

    Like many congenital heart conditions, atrioventricular canal defect isn’t actually a single defect, but rather a group or cluster of closely associated defects in various combinations and with varying degrees of severity:

    • atrial septal defect (ASD)
      • The wall of tissue (septum) that separates the two upper heart chambers (left and right atria) has a hole.
      • The defect allows oxygen-rich (red) blood to pass from the left atrium through the hole, and then mix with oxygen-poor (blue) blood in the right atrium.
    • ventricular septal defect (VSD)
      • The wall of muscle tissue (septum) that separates the two lower chambers of the heart (left and right ventricles) has a hole.
      • The defect allows oxygen-rich (red) blood to pass from the left ventricle through the opening, and then mix with oxygen-poor (blue) blood in the right ventricle.
    • abnormalities of the atrioventricular (AV) valves (mitral and tricuspid)
      • The valves that separate the upper heart chambers (atria) from the lower chambers (ventricles) are abnormally formed. Often this results in one large “common” valve rather than two separate valves.

    This cluster of defects can result in what is essentially a common AV valve that sits between the four heart chambers, with holes above and below the valve. This allows blood to pass between the chambers above and below the valve. Blood moves freely among the four heart chambers, mixing oxygen-rich and oxygen-poor blood, and typically results in more blood flow than normal to flow from the heart to the lungs. This extra blood flow to the lungs is often responsible for many of the symptoms seen in such children.

    How Boston Children's Hospital approaches AV canal

    The experienced surgeons in Boston Children’s Cardiac Surgery Department understand how distressing a diagnosis of an atrioventricular canal defect can be for parents. You can have peace of mind knowing that our surgeons treat some of the most complex pediatric heart conditions in the world, with overall success rates approaching 98 percent—among the highest in the nation among large pediatric cardiac centers.

    In particular, the methods used to repair AV canal have improved greatly in the past two decades, and the operation has a high likelihood of success.

    At Boston Children’s, we provide families with a wealth of information, resources, programs and support—before, during and after your child’s treatment. With our compassionate, family-centered approach to expert treatment and care, you and your child are in the best possible hands.

    Atrioventricular canal defect: Reviewed by David Brown, MD
    © Boston Children's Hospital, 2010

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