Name two congenital heart defects that commonly cause left-to-right shunts and their potential pulmonary vascular consequences.

Name two congenital heart defects that commonly cause left-to-right shunts and their potential pulmonary vascular consequences.

• A. Ventricular septal defect and atrial septal defect; can cause pulmonary congestion and Eisenmenger syndrome with reversal of shunt
• B. Tetralogy of Fallot and transposition of the great arteries; result in decreased pulmonary blood flow
• C. Patent ductus arteriosus and coarctation; lead to systemic hypertension
• D. Aortic stenosis and mitral valve prolapse; lead to pulmonary edema

Answer: (A)

Left-to-right shunts occur when oxygenated blood from the left heart is diverted back into the right heart and lungs, increasing pulmonary blood flow. The two defects that most commonly produce this scenario are ventricular septal defect and atrial septal defect. The extra flow to the lungs subjects the pulmonary vasculature to higher pressures and shear, triggering vascular remodeling with medial hypertrophy and intimal proliferation. Over time this can lead to pulmonary hypertension and congestive changes. If the shunt persists, pulmonary vascular resistance can rise to systemic levels and the direction of flow may reverse, producing Eisenmenger syndrome with cyanosis due to right-to-left shunting. Other options describe conditions that typically reduce pulmonary blood flow or produce different hemodynamics, not the classic left-to-right overcirculation described here.

Left-to-right shunts occur when oxygenated blood from the left heart is diverted back into the right heart and lungs, increasing pulmonary blood flow. The two defects that most commonly produce this scenario are ventricular septal defect and atrial septal defect. The extra flow to the lungs subjects the pulmonary vasculature to higher pressures and shear, triggering vascular remodeling with medial hypertrophy and intimal proliferation. Over time this can lead to pulmonary hypertension and congestive changes. If the shunt persists, pulmonary vascular resistance can rise to systemic levels and the direction of flow may reverse, producing Eisenmenger syndrome with cyanosis due to right-to-left shunting. Other options describe conditions that typically reduce pulmonary blood flow or produce different hemodynamics, not the classic left-to-right overcirculation described here.