An atrioventricular (AV) canal is a large hole in the center of the heart between the upper chambers and lower chambers. Also, the tricuspid and mitral valves that normally separate the heart's upper and lower chambers aren't formed as individual valves. Instead, a single large valve forms that crosses the defect.
The large opening in the center of the heart lets oxygen-rich (red) blood from the heart's left side (blood that has just gone through the lungs) pass into the heart's right side. There, the oxygen-rich blood, along with venous (bluish) blood from the body, is sent back to the lungs. The heart pumps an extra amount of blood and may enlarge. Most babies with an atrioventricular canal don't grow normally and may become malnourished.
In some babies, the common valve between the upper and lower chambers doesn't close properly; this allows blood to leak backward from the heart's lower chambers to the upper ones. This leak (called regurgitation or insufficiency) can occur on the right side, left side, or both sides of the heart. With a valve leak, the heart pumps an extra amount of blood, becomes overworked and enlarges.
Heart with Atrioventricular Canal
The exact cause of an AV canal is unknown. We know that the heart is formed abnormally early in fetal development. We also know that there is a high association between AV canal and Down syndrome; however, not all children with an AV canal have Down syndrome.
Most infants and children with an AV canal have symptoms such as:
The physical examination usually demonstrates an abnormal murmur with other features that increase the suspicion for this type of defect. However, in newborn infants, no symptoms or abnormal murmurs may be present since the pressures in the right and left ventricle may be nearly equal. The symptoms and abnormal murmurs may not appear until a few weeks after birth. The diagnosis is then confirmed with an echocardiogram.
Your doctor may suggest open heart surgery to repair the issue. The risks of open-heart surgery include bleeding, infection and the need for cardiopulmonary bypass. Special risks include injury to the electrical system of the heart, the possibility of a residual hole in the heart and the possibility of residual leakiness or obstruction of the repaired valve.
The long-term outlook for AV canal depends in part on the success of the heart surgery. Long-term follow-up with a pediatric cardiologist is recommended.