1. As the septum primum grows, the ostium primum progressively narrows. 2. Persistence of the ostium secundum is the most common atrial septal defect. 3. There is widening of the maxillary ostium that extends to the nasopharynx. 4. The ostium secundum progressively enlarges and the size of the septum primum diminishes. 5. This method avoids the symptoms that accompany most ostium secundum atrial septal defects. 6. The ostium secundum provides communication between the atria after the ostium primum closes completely. 7. The ostium secundum provides communication between the atria after the ostium primum closes completely. 8. The ostium secundum atrial septal defect accounts for 7 % of all congenital heart lesions. 9. The ostium secundum allows continued shunting of blood from the right atrium to the left. 10. About 10 to 20 % of individuals with ostium secundum ASDs also have mitral valve prolapse.
