Pediatric Settings Road Map Practice Test

The most common cyanotic congenital heart defect is Tetralogy of Fallot. This condition combines four anatomical features—ventricular septal defect, pulmonary stenosis (which creates right ventricular outflow tract obstruction), right ventricular hypertrophy, and an overriding aorta. The pulmonary stenosis limits blood flow to the lungs while the VSD allows mixing of deoxygenated blood with oxygenated blood, promoting right-to-left shunting and cyanosis. Among cyanotic lesions, this combination appears more frequently than others like transposition of the great arteries, truncus arteriosus, or hypoplastic left heart syndrome, making Tetralogy of Fallot the most common cyanotic defect. (For context, the overall most common congenital heart defect is actually acyanotic VSD, but among cyanotic lesions ToF holds that distinction.)