Tetralogy of Fallot is classically characterized by four features which are: Right ventricular outflow tract obstruction (RVOTO) due to infundibular stenosis or hypoplastic pulmonary valve annulus or bicuspid pulmonary valve and/or hypoplasia of pulmonary aery Overriding of aoa Right ventricular hyperophy (only develops after bih) Ventricular septal defect. Figure showing TOF with 'Boot shaped hea'