The objective of this study was to determine if perioperative elevation of cardiac troponin I (cTnI) predicts mortality in infants and children after surgical correction of congenital heart defects. One hundred infants and children having open heart surgery were studied. Blood samples for cTnI analysis were collected before cardiopulmonary bypass (CPB) and at 4, 8, 12, and 24 h after initiation of CPB. Demographic information, cardiac defect, repair performed, duration of CPB, complications, and outcome were recorded. Cardiac defects were categorized as atrial septal defect (ASD), ventricular septal defect (VSD), hypoplastic left heart syndrome (HLHS), complex, and "other." Baseline cTnI was significantly lower in survivors (mean 0.42 ng/ml, median 0.35 ng/ml) than in nonsurvivors (mean 1.89, median 1.30), p = 0.0001. Baseline cTnI was significantly higher in the HLHS group (mean 1.47, median 1.10) than in all other subgroups (mean 0.62, median 0.35), p </= 0.009. There were no significant differences between survivors and nonsurvivors at the remaining sampling times. Children who died from cardiac failure (n = 2) were more likely to have 4 h cTnI >125 ng/ml compared to survivors (2 of 90). Within cardiac defect subgroups, 4 h cTnI was significantly higher in the complex group (mean = 53.51, median = 32.30) than in the ASD (mean = 23.84, median = 19.85) and other (mean = 21.59, median 21.50) subgroups. Perioperative measurement of cTnI identifies children within specific cardiac defect subgroups at risk of mortality after cardiac surgery. We speculate that detection of myocardial injury may decrease mortality and morbidity in children with complicated congenital cardiac lesions by leading to improvements in perioperative management.