A congenital cardiovascular malformation in which there is an interatrial communication confined to the region of the oval fossa (fossa ovalis), most commonly due to a deficiency of the primary atrial septum (septum primum) but deficiency of the septum secundum (superior interatrial fold) may also contribute.
Also indexed as
Atrial septal defect within oval fossaOstium secundum atrial septal defectSecundum atrial septal defect