A heart defect involving the septum which is present at birth. The defect is a hole in the wall of the heart that separates the right and left chambers and allows blood to flow through the hole. An atrial septal defect is a hole between the two upper heart chambers and a ventricular septal defect is a hole between the two lower heart chambers. Symptoms are determined by the size and exact location of the defect. See also Congenital heart septum defect
