Most common type of Atrial septal defect is

The atrial septal defect can occur in any poion of the atrial septum(secundum, primum or sinus venosus)OSTIUM SECUNDUM:Most common type of ASD accounts for 7% of al congenital hea disease.Defect situated at fossa ovalis.Associated with structurally normal atrioventricular (AV)valves.OSTIUM PRIMUM/ ENDOCARDIAL CUSHION DEFECT:Defect situated inferior to fossa ovalis.Associated with the cleft in AV valves.Most common cardiac lesion in Down&;s syndrome is endocardial cushion defect.