Atrial septal defect
What is an atrial septal defect?
The heart is divided into four separate chambers. The upper chambers, or atria, are divided by a wall called the atrial septum.
A defect between the heart's two upper chambers (the atria) is called an atrial septal defect (ASD). Atrial septal defects are one of the most common heart defects, and are caused by incomplete growth of the septal wall during fetal development.
There are several types of atrial septal defects - they are classified by where they occur and their size. A secundum ASD is a hole in the middle of the atrial septum, which lets blood flow from the left chamber to the right chamber or from the right chamber to the left chamber, depending on the pressures in the atria.
When an atrial septal defect is present, blood flows through the hole, usually from the left atrium to the right atrium. This increases the blood volume in the right atrium, which causes more blood to be pumped to the lungs. Because it is receiving extra blood, the right side does more than the normal share of work. This may cause you to feel tired, have difficulty in breathing or be sick more often with respiratory infections such as cold or pneumonia. It also causes the right sided pumping chamber to become stretched and enlarged.