A 3-month-old infant is brought to the clinic for intermittent cyanosis, especially during feeding or crying spells. On examination, a harsh systolic ejection murmur is heard at the left upper sternal border. Chest X-ray shows a 'boot-shaped' heart. Which congenital heart defect is most likely present?

The correct answer to the question "A 3-month-old infant is brought to the clinic for intermittent cyanosis, especially during feeding or crying spells. On examination, a harsh systolic ejection murmur is heard at the left upper sternal border. Chest X-ray shows a 'boot-shaped' heart. Which congenital heart defect is most likely present?" is Option D: Tetralogy of Fallot.

The other options — A) Ventricular septal defect, B) Atrial septal defect, C) Transposition of the great arteries — are incorrect for this USMLE Exam Prep question. As explained above: The classic presentation of Tetralogy of Fallot includes cyanotic spells (tet spells), a harsh systolic murmur from right ventricular outflow tract obstruction, and a 'boot-shaped' heart on CXR due t…