In infants with congenital heart defects, which condition is associated with increased pulmonary blood flow?

In infants with congenital heart defects, the condition associated with increased pulmonary blood flow is patent ductus arteriosus. This occurs when there is an abnormal connection allowing blood to flow from the aorta back to the pulmonary artery because the ductus arteriosus, a normal fetal blood vessel, fails to close after birth. This results in increased blood flow to the lungs, leading to pulmonary congestion and potential damage to the pulmonary vasculature.

In contrast, transposition of the great vessels typically results in two separate circulatory systems and does not generally lead to increased pulmonary blood flow because the oxygenated and deoxygenated blood do not mix effectively. Ventricular septal defect can also cause increased pulmonary blood flow, but patent ductus arteriosus is more directly associated with the widespread effects of increased pulmonary circulation due to its unique vascular connection. Aortic stenosis primarily affects blood flow from the heart to the body and doesn't inherently lead to increased pulmonary blood flow since it causes obstruction rather than a shunt or connection that allows additional pulmonary circulation.