Atrial Septal Defect (ASD) is a congenital heart condition characterised by an opening in the wall (septum) that separates the two upper chambers of the heart. This abnormal communication allows oxygen-rich and oxygen-poor blood to mix, increasing blood flow to the lungs and placing extra strain on the heart. Many small defects may remain unnoticed for years, while larger defects can cause symptoms such as shortness of breath, palpitations, recurrent respiratory infections or delayed growth in children. If not appropriately managed, significant ASDs may lead to complications involving the heart and pulmonary circulation over time.