An atrioventricular (AV) canal defect is a rare heart defect. There is a large hole in the center of the heart that connects all four chambers.

The heart is made up of two upper chambers and two lower chambers. Usually blood flows from the upper to lower chamber on the right side of the heart to the lungs. The blood picks up oxygen in the lungs and passes back into the upper chamber of the left side of the heart. It then passes to the lower chamber of the heart and out to the body.

The AV canal defect causes blood in the different chambers to mix. This means that some of the blood that is sent out to the body has not passed the lungs to pick up oxygen. The body does not get enough oxygen.

Heart Chambers and Valves
heart anatomy
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Blood Flow Through the Heart
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AV canal defect is a congenital defect. This means that the baby is born with it. It is not known exactly why some babies’ hearts develop abnormally.