OBJECTIVE: To study the protective effect of cold autologous blood cardioplegic solution on the heart of infants with cyanotic congenital heart disease (CCHD). METHODS: Ninety-six infants with CCHD who underwent cardiopulmonary bypass (CPB) were randomly and equally divided into three groups: histidine-tryptophan-ketoglutarate (HTK) solution, cold non-autologous blood cardioplegic solution, and cold autologous blood cardioplegic solution. The right auricular tissues were taken before aortic cross-clamping and at 30 minutes after aortic declamping, and ATP level and energy charge (EC) in the myocardium were measured. Venous blood was collected before and immediately after CPB, and the serum levels of creatine kinase (CK)-MB and cardiac troponin I (cTnI) were measured. The clinical parameters, such as the re-beat time and re-beat rate during CPB, cardiac index, dependence on positive inotropic agents, and left ventricular ejection fraction (LVEF) at 2 hours after CPB, the incidence rate of arrhythmia within 24 hours after CPB, and postoperative complications and mortality, were recorded. RESULTS: At 30 minutes after aortic declamping, the three groups showed significantly decreased ATP and EC levels (P<0.05), and the cold autologous blood group had significantly higher ATP and EC levels than the other two groups (P<0.05). Immediately after CPB, the three groups showed significantly increased serum levels of CK-MB and cTnI (P<0.05), and the cold autologous blood group had significantly lower serum levels of CK-MB and cTnI than the other two groups (P<0.05). The cold autologous blood group had significantly better outcomes than the other two groups in terms of the re-beat time during CPB and the dependence on positive inotropic agents and LVEF at 2 hours after CPB (P<0.05). CONCLUSIONS: Cold autologous blood cardioplegic solution is superior to HTK and cold non-autologous blood cardioplegic solutions in preserving myocardial energy and reducing myocardial injury in infants with CCHD who undergo CPB, thus providing a better protective effect on the heart.