An atrial septal defect is an opening in the atrial septum, or dividing wall between the two upper chambers of the heart known as the right and left atria.

• （人的心脏有4个腔，位于上方的）称为右心房和左心房的两个腔之间（有一个本来应该完整的房间隔，如果）在心房间隔上有一个开口就叫做房间隔缺损。