An AV canal is a large hole in the center of the heart. Essentially what this means is that the walls between the two upper chambers and the two lower chambers, as well as the valves may be deformed. This extra effort in turn can cause the heart to enlarge, in addition the body receives less oxygen since it receives red blood that is mixed with the low oxygen blue blood . Children that suffer from an AV canal defect, tend to grow very slow and remain small. Also because of the high volume of blood that is pumped through the lungs high blood pressure may also occur resulting in damage to the lungs and blood vessels.
Surgery can normally repair an AV canal defect to help restore normal blood circulation.
The VSD is a large opening between the ventricles in which, as with the AV canal defect oxygenated and deoxygenated blood mix. This results in similar problems as those mentioned for the AV canal. This happens when there is a large defect between the atria.