Atrial Septal Defect (ASD) is a congenital heart condition characterized by a hole in the wall (septum) that separates the two upper chambers of the heart, known as the atria. This defect allows oxygen-rich blood from the left atrium to mix with oxygen-poor blood in the right atrium, which can lead to increased blood flow to the lungs and potential complications over time. ASD can vary in size and may not cause noticeable symptoms in some individuals. However, if left untreated, it can lead to heart failure, arrhythmias, or pulmonary hypertension. Diagnosis is typically made through echocardiography or other imaging techniques, and treatment options may include monitoring, medication, or surgical repair.