Which finding is NOT part of Tetralogy of Fallot?

• A. Ventricular septal defect
• B. Overriding aorta
• C. Atrial septal defect
• D. Pulmonary stenosis

Answer: (C)

Tetralogy of Fallot arises from abnormal development of the infundibular portion of the interventricular septum, producing four related problems that together cause right-to-left shunting and cyanosis. The defining features are a large ventricular septal defect, an overriding aorta that receives blood from both ventricles, and obstruction of the right ventricular outflow tract (pulmonary stenosis) with resultant right ventricular hypertrophy. An atrial septal defect is not part of this quartet; it’s a separate defect that can coexist but does not define Tetralogy of Fallot. So the finding that is not part of Tetralogy of Fallot is an atrial septal defect.