In infants with congenital heart defects, which defect is most likely to present with cyanosis?

Cyanosis in infants with congenital heart defects typically arises from decreased oxygenation of blood, resulting in a bluish discoloration of the skin and mucous membranes. Among the defects listed, transposition of the great arteries is particularly notable for presenting with significant cyanosis.

In transposition of the great arteries, the aorta and pulmonary artery are switched, leading to systemic and pulmonary circulations being separate. This condition prevents oxygenated blood from effectively reaching the body, while the deoxygenated blood returns to the lungs. Unlike the other mentioned defects, transposition creates a situation where there is no mixing of oxygen-rich and oxygen-poor blood without the presence of other defects or shunts, which leads to pronounced cyanosis at birth.

The other congenital heart defects listed typically cause different patterns of blood flow and are less likely to lead to cyanosis in the same immediate manner. For example, atrial septal defect and ventricular septal defect allow for some mixing of oxygenated and deoxygenated blood, usually resulting in relatively less severe or absent cyanosis. Patent ductus arteriosus can also allow for mixing but typically does not produce the level of cyanosis seen in transposition of the great arteries. Therefore, transposition of the great arteries