<prompt> Essential criteria for TOF includes all exceptValvular stenosisInfundibular stenosisOverriding of aortaRVH  <response>: 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 saysThe 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 45Obstruction at the pulmonary level 10.Combination of infundibular and valvular obstruction 30.Pulmonary atresia 15. 