Congenital Heart Defects Quiz

See Section. Option C describes hypoplastic left heart syndrome: severe underdevelopment of the left ventricle and associated left-sided structures. Hypoplastic means smaller or less developed than normal. The mitral and aortic valves and ascending aorta are also commonly very small or obstructed. The left heart therefore cannot provide an adequate systemic circulation after birth. Blood returning from the lungs must cross an atrial communication, and the right ventricle supplies the body through the ductus arteriosus, the foetal connection between the pulmonary artery and aorta. Reduced flow during foetal development may contribute, but one particular inflow abnormality is not a universal explanation for the syndrome.

Right ventricular hypertrophy from pulmonary artery stenosis (A) is a right-sided pressure-load problem, not the defining small left heart. A ventricular septal defect (B) is a hole between the ventricles and does not by itself explain severe left-sided underdevelopment. Transposition (E) means that the great arteries arise from the opposite ventricles, creating a different arrangement of the circulation. Isolated pulmonary valve narrowing (D) obstructs the right ventricular outlet while leaving the left-sided structures outside the defining lesion.