A 2-year-old boy has cyanosis since birth, squatting posture during play, and hypercyanotic spells relieved by knee-chest position. Echocardiography confirms Tetralogy of Fallot. Which of the following is NOT a component of this defect?
- A Ventricular septal defect
- B Atrial septal defect ✓
- C Right ventricular hypertrophy
- D Overriding aorta
Correct answer: B. Atrial septal defect
Explanation
The four components of Tetralogy of Fallot are: (1) ventricular septal defect, (2) pulmonary stenosis/right ventricular outflow tract obstruction, (3) overriding aorta, and (4) right ventricular hypertrophy. ASD is NOT a component; its presence along with TOF constitutes 'Pentalogy of Fallot.' Squatting increases systemic vascular resistance, reducing right-to-left shunt and improving oxygen saturation.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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