Coarctation of the aorta (CoA) is a discrete narrowing of the aortic lumen, typically occurring at the aortic isthmus just distal to the left subclavian artery origin, near the insertion of the ductus arteriosus (juxtaductal). This narrowing creates a pressure gradient, with hypertension proximal to the coarctation (head, upper extremities) and hypotension distal to it (abdominal organs, lower extremities). The pathophysiology varies by age of presentation. Neonatal/infantile coarctation (preductal or juxtaductal) is often severe and presents when the ductus arteriosus closes, as ductal flow was providing perfusion to the lower body. This is a ductal-dependent lesion — closure of the PDA leads to acute hemodynamic collapse with severe lower extremity hypoperfusion, metabolic acidosis, and shock. Older children/adults with coarctation have milder narrowing and develop collateral circulation through intercostal, internal mammary, and subclavian arteries, compensating for the obstruction. The left ventricle faces chronic increased afterload from the obstruction, leading to left ventricular hypertrophy, heart failure, and increased risk for aortic dissection, cerebral aneurysm rupture, and endocarditis. Coarctation is strongly associated with bicuspid aortic valve (present in 50-85% of CoA patients) and...