<unk>  or<unk>  is a type of congenital heart<unk>  in which the wall separating the upper chambers of the heart does not fuse completely. During fetal development, the opening between the two<unk> (the upper chambers of the heart) is needed to allow blood to bypass the lungs. Eventually, as the fetus becomes more developed, the lungs can support circulation and the opening fuses shut.  An<unk>  can result in shunting of blood disproportionately between the right and left sides of the heart.
Atrial septal defect
Atrioventricular canal defect
Atrioventricular septal defect
Ventricular septal defect
Tricuspid atresia
Persistent truncus arteriosus
Patent ductus arteriosus 
Patent ductus arteriosus