Tetralogy of Fallot consists of four heart defects. Which set correctly lists these defects?

• A. VSD; Pulmonary stenosis; Right ventricular hypertrophy; Overriding aorta
• B. VSD; Aortic stenosis; Right atrial hypertrophy; Overriding aorta
• C. ASD; Pulmonary atresia; Right ventricular failure; Overriding aorta
• D. VSD; Pulmonary stenosis; Left ventricular hypertrophy; Overriding aorta

Answer: (A)

Tetralogy of Fallot is defined by four defects: a ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. The pulmonary outflow obstruction from the stenosis increases the pressure the right ventricle must generate, promoting a right-to-left shunt across the VSD. This shunting and pressure load cause the right ventricle to hypertrophy. The aorta lies over the VSD, allowing mixed blood from both ventricles to enter systemic circulation. The other options include defects not part of this quartet (such as aortic or left-sided abnormalities, atrial defects, or left ventricular hypertrophy), or list wrong components, making them inconsistent with the characteristic four features.