Osmosis (Elsevier)

Atrial Septal Defect - Physiology, Pathology, Clinical Manifestations, Diagnosis, Treatment

The video explains atrial septal defect (ASD), a congenital opening between the heart’s atria that persists after birth when the septum primum and septum secundum fail to fuse properly. It details embryologic formation—septum primum creates the ostium primum, followed by the ostium secundum and the overlapping septum secundum that normally form a one‑way fetal shunt. In the newborn, the left‑to‑right pressure gradient forces blood from the left atrium into the right, producing a volume‑loaded right heart, fixed splitting of S2, and a systolic murmur at the upper left sternal border. Secundum ASD accounts for roughly 90 % of cases, while primum defects are linked to Down syndrome and other anomalies. The video highlights complications such as right‑atrial dilation, atrial fibrillation, paradoxical emboli, and, in large untreated lesions, pulmonary hypertension progressing to Eisenmenger syndrome. Because many ASDs remain asymptomatic until adulthood, clinicians must recognize the characteristic murmur and consider echocardiography. Treatment ranges from percutaneous device closure for suitable defects to open‑heart surgery for larger or complex lesions, preventing long‑term heart failure and stroke risk.