Objectives:The aim of this study was to relate changes in energy expenditure and growth in infants with congenital heart disease (CHD), to the timing of corrective cardiac surgery.Methods:Prospective cohort study of infants less than 1 year with CHD admitted for cardiac surgery to Royal Children's Hospital, between January to September 2005. Infants were assessed using anthropometry and indirect calorimetry and compared to healthy age-matched controls.Results:Infants (38) underwent corrective (n=25) or palliative (n=13) cardiac surgery either at </=10 days or at >10 days. Infants undergoing corrective surgery after 10 days had deficits in z-scores for weight compared with infants undergoing early surgery (-1.15+/-1.02 vs -0.24+/-0.98; CI 95%: -1.736 to -0.085; P<0.05) and height (-1.47+/-1.16 vs -0.12+/-0.66; CI 95%: -2.262 to -0.428; P<0.01). However, 6 months following surgery, weight and height were similar in both groups. Resting energy expenditure was increased before surgery compared to healthy controls (247+/-36 vs 210+/-22 kJ kg(-1 )day(-1); 95% CI: -57.29 to -16.71; P<0.001) however, normalized 1 week following cardiac surgery. Standard equations did not accurately predict measured REE.Conclusion:Increased REE observed in infants with CHD normalizes within 1 week following corrective cardiac surgery. Deficits in weight and growth were greater in infants undergoing corrective cardiac surgery>10 days of age compared with infants undergoing surgery in the first 10 days of life.European Journal of Clinical Nutrition advance online publication, 14 November 2007; doi:10.1038/sj.ejcn.1602956.