Atrial septal defect (ASD) is one of the most common congenital disorders which affect the upper chamber of the heart. A baby suffering from ASD is born with an opening in the partition of the heart, called as septum, that separates the right atrium and the left atrium.
It is characterized by the presence of a hole in the inter-atrial septum present between the walls of the atria. This hole develops during the stages of fetal development. As a result of the hole between the septa, the nonfunctional fetal lungs are bypassed as the blood reaches directly from the right atrium to the left atrium.
By the time of birth, this hole between the septa gets closed naturally. If the septum is still defective at the time of birth, the oxygen-rich blood leaks from the right atrium and gets mixed with oxygen-poor blood present in the left atrium. This may result in serious complications due to a drastic impact on the performance of the heart and lungs.