Atrioventricular septum

Canal defect (also known as atrioventricular septal defect) means there is a large hole in the septum.
The septum is the wall that separates the right and left sides of the heart.
A canal defect may be classified as partial or complete.
In a partial canal defect, either the upper (atrial) or lower (ventricular) part of the septum may be affected.
A complete canal defect, which is more common, means that the hole is located where the upper (atrial) and lower (ventricular) parts of the septum meet.
Canal defect is often associated with Down's syndrome.
During surgery, the surgeon closes the defects with one or two patches. The patch(es) will become a permanent part of the heart as the heart lining grows over it.
The surgeon also divides the single valve between the upper and lower chambers of the heart and constructs two separate valves to resemble normal valves as nearly as possible.