A hole in the septum between the heart's two upper chambers is called an atrial septal defect (ASD). An atrial septal defect (ASD) is a hole in the part of the septum that separates the atria (the upper chambers of the heart). This hole allows oxygen-rich blood from the left atrium to flow into the right atrium instead of flowing into the left ventricle as it should.
Causes of Atrial Septal Defect :
ASDs occur during faetal development of the heart and are present at birth. During the first weeks after conception, the heart develops. If a problem occurs during this process, a hole in the atrial septum may result. If the ASD is persistent, blood continues to flow from the left to the right atria. This is called a shunt.
Individuals with ASD are at an increased risk for developing a number of complications including Atrial fibrillation (in adults), Heart failure, Pulmonary overcirculation, Stroke etc.