An atrial septal defect allows oxygen-rich (red) blood to pass from the left atrium, through the opening in the septum, and then mix with oxygen-poor (blue) blood in the right atrium. An ostium secundum is an opening in the middle of the atrial septum which is the most common type of ASD. Atrial septal defects occur in 5 to 10 percent of all children born with congenital heart disease. For unknown reasons, girls have atrial septal defects twice as often as boys.
Atrial septal defect (ASD) – Causes, Symptoms, Diagnosis, Treatment and Ongoing care - Congenital defect or opening in the atrial septum allowing flow of blood between the 2 atria Read more: http://health.tipsdiscover.com/atrial-septal-defect-asd-causes-symptoms-diagnosis-treatment-and-ongoing-care/#ixzz2XphlrXBm