This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pediatrics
Most common type of Atrial septal defect is 
Select and explain. 
A. Ostium primum, B. Ostium secundum, C. Cushion defect, D. Endocardial hyperophy
B: Ostium secundum
Answer: B: Ostium secundum 
Explanation: 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.