Which congenital heart defect is cyanotic and often presents with clubbing and a murmur?

• A. Atrial septal defect
• B. Tetralogy of Fallot
• C. Coarctation of the aorta
• D. Patent ductus arteriosus

Answer: (B)

This item tests recognizing a cyanotic congenital heart defect that causes chronic hypoxemia with clubbing and a murmur. Tetralogy of Fallot fits best because it combines a ventricular septal defect with obstruction of the right ventricular outflow tract, plus an overriding aorta and right ventricular hypertrophy. The RVOT obstruction creates a right-to-left shunt across the VSD, lowering blood oxygen levels and producing cyanosis. Over time, chronic hypoxemia leads to digital clubbing, while the murmur is a harsh systolic sound best heard along the left upper sternal border from the RVOT obstruction. A fixed or differential S2 can be present due to altered pulmonary flow.

In contrast, an atrial septal defect typically causes a left-to-right shunt with a systolic ejection murmur and a fixed split S2, and cyanosis is not present early unless Eisenmenger physiology develops. Coarctation of the aorta is not a cyanotic defect and presents with differential pulses and blood pressures rather than a characteristic cyanotic presentation. Patent ductus arteriosus features a continuous murmur and is usually acyanotic in infancy, unless late Eisenmenger changes occur.