Tetralogy of Fallot comprises four anatomic defects, including VSD, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy.

• A. Two anomalies
• B. Three anomalies
• C. Four anomalies
• D. Five anomalies

Answer: (C)

Tetralogy of Fallot is defined by four structural heart defects. The four components are ventricular septal defect, pulmonary stenosis, an overriding aorta, and right ventricular hypertrophy. Because there are four distinct abnormalities, the correct choice is the one that indicates four anomalies. Selecting fewer would omit a defining feature, while five would imply an extra abnormality not part of the classic presentation. These four defects together cause a right-to-left shunt and cyanosis: the pulmonary stenosis creates outflow obstruction, the VSD allows mixing of blood, and the overriding aorta receives deoxygenated blood from the right ventricle. The right ventricular hypertrophy reflects the chronic pressure load from the pulmonary stenosis. Surgical repair aims to relieve the outflow obstruction and close the VSD to improve oxygenation.