ObjectivesThis study was conducted to compare the efficacy of histidine-tryptophan-ketoglutarate (HTK) cardioplegia and cold blood cardioplegia (CBC), especially for postoperative right ventricle (RV) function after Tetralogy of Fallot (TOF) repair. DesignRandomized, double-blinded, parallel group, controlled, clinical trial. SettingAin Shams University Hospitals.) ParticipantsA total of 100 children (1-5 years-old) scheduled for TOF repair. InterventionsPatients were allocated (double blinded one: one allocation ratio), to either HTK Group that received HTK cardioplegia (30 ml/kg by antegrade route) or CBC Group that received cold blood cardioplegia with blood to Ringer solution (4:1) in volume of 20 ml/kg. Measurements and Main ResultsThe HTK group showed a statistically significant reduction of the vasoactive inotropic score on admission to pediatric intensive care unit (13.0±4.1) in comparison to CBC (15.5±5.4) with P-value of 0.011 but after 24 hours Vasoactive-Inotropic Score was comparable. Lactate level during the first 24 hours in HTK group (6.2±0.7) mmol/l and (6.9±0.4) mmol/l in CBC group with P-value < 0.0001. Serial troponin measurements were lower in the HTK group (1.49 ± 0.45) in comparison to the CBC group (1.69 ± 0.18) with P-value of 0.005 at the first 72 hours postoperatively. Postoperative echocardiographic assessment of RV function by mean of tricuspid annular plane systolic excursion and myocardial performance index were better in HTK than CBC (P-value<0.05). ConclusionsHTK cardioplegia may offer better cardiac protection to pediatric patients undergoing TOF repair than our institutional standard CBC with better recovery for the hypertrophic RV.