This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cyanotic Congenital Heart Disease, Subject name: Pediatrics
Essential criteria for TOF includes all except, 
Select and explain. 
A. Valvular stenosis, B. Infundibular stenosis, C. Overriding of aorta, D. RVH
A: Valvular stenosis
Answer: A: Valvular stenosis 
Explanation: Ans. is 'a' i.e. Valvular stenosis Right ventricular outflow obstruction is one of the characteristic of tetralogy of fallot.This right ventricular outflow obstruction is mainly caused due to infundibular stenosis.Pulmonary valve stenosis (alone) rarely contributes to the right ventricular outflow obstruction in tetralogy of fallot..Hurst cardiology says "The pulmonary valve is often malformed, usually being either bicuspid or unicuspid. The valve may contribute to pulmonary stenosis, but, only uncommonly, it is the only site of significant obstruction to the pulmonary flow".Causes of right ventricular outflow tract obstruction.Infundibular stenosis (45%).Obstruction at the pulmonary level (10%).Combination of infundibular and valvular obstruction (30%).Pulmonary atresia (15%).