Tetralogy of Fallot (TOF) is a common cyanotic congenital heart disease. Its surgical correction requires ventricular septal defect (VSD) closure and right ventricular outflow tract obstruction (RVOTO) relief, with transannular patch enlargement (TAPE) of the pulmonary valve. The first successful repair of TOF was reported in 1954 and consisted of closure of the VSD through a large right ventriculotomy, and RVOTO relief with TAPE of the pulmonary valve. To predict the intra-operative requirements and post-operative course of patients with this condition, various evaluation indices are available that can provide a good indication of patient prognosis. In this case report, we describe a novel pulmonary vein index (PVI) indicator that offers prognostic indications for pediatric cardiac patients who have undergone surgical correction of TOF.