Essential criteria for TOF includes all except –

Right ventricular outflow obstruction is one of the characteristics 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 biscuspid or unicuspid. The valve may contribute to pulmonary stenosis, but, only uncommonly, it is the only site ofsignificant 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%).