Slide show: Common types of congenital heart defects
Image of heart with atrioventricular canal defect
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This is a combination of defects, including a large hole in the center of the heart and a single common valve instead of the separate tricuspid and mitral valves. Also called atrioventricular septal defect, this defect is classified by whether it's only partial (involving only the upper chambers of the heart), or complete (in which blood can travel freely among all four chambers of the heart). Both forms of the defect allow extra blood to circulate to the lungs, causing the heart to enlarge.

The condition occurs most often in children with Down syndrome. Infants may also have trouble breathing and not grow well. Surgery is often done in infancy to close the hole and reconstruct the valves.

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