What is the commonest site of RVOT obstruction in TOF?

What is the commonest site of RVOT obstruction in TOF?

What is the commonest site of right ventricular outflow tract obstruction in tetralogy of Fallot? The commonest site of right ventricular outflow obstruction in Tetralogy of Fallot is  infundibular (subvalvar) pulmonary stenosis. Obstruction can be at other locations like valvar pulmonary stenosis, supravalvar pulmonary stenosis and annular pulmonary stenosis. There could be a combination of these lesions as well. Infundibular spasm with dynamic worsening of right ventricular outflow obstruction is thought to be one of the pathophysiological mechanisms of cyanotic spells in Tetralogy of Fallot. Immature respiratory center has an important role in the tachypnea leading on to the spell.