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Abstract Preliminary evidence suggests perturbations of the kynurenine pathway (KP) of tryptophan metabolism in infants with single ventricle heart disease (SVHD). In 72 infants with SVHD undergoing stage 2 palliation (S2P) and 41 controls, we quantified serum KP metabolite concentrations via tandem mass spectroscopy pre‐S2P and post‐S2P at 2, 24, and 48 h and assessed metabolite relationships with post‐S2P outcomes (length of stay, hypoxemia burden, and intubation duration). Pre‐S2P, SVHD infants had lower tryptophan and serotonin levels and higher kynurenic acid, 3‐hydroxykynurenine, and picolinic acid levels than controls. Post‐S2P, metabolites peaked at 2 h, with return to baseline by 48 h for all except kynurenic acid, which remained elevated. Metabolite concentrations pre‐S2P were poorly associated with outcomes. A lower serotonin peak 2 h post‐S2P was associated with longer length of stay and intubation duration. Multiple metabolites at 24 and 48 h correlated with outcomes; notably, elevated kynurenic acid was associated with worse results for all three outcomes. Our results confirm that interstage SVHD infants have altered KP activity compared to controls. Further, the link between outcomes and KP metabolites post‐S2P—but not at baseline—demonstrates that acute, perioperative changes in tryptophan catabolism may be more important to tolerating S2P physiology than chronic interstage changes.

IntroductionChildren with single ventricle heart disease (SVHD) experience significant morbidity across systems and time, with 70% of patients experiencing acute kidney injury, 33% neurodevelopmental impairment, 14% growth failure, and 5.5% of patients suffering necrotizing enterocolitis. Proteomics is a method to identify new biomarkers and mechanisms of injury in complex physiologic states.MethodsInfants with SVHD in the interstage period were compared to similar-age healthy controls. Serum samples were collected, stored at −80°C, and run on a panel of 1,500 proteins in single batch analysis (Somalogic Inc., CO). Partial Least Squares-Discriminant Analysis (PLS-DA) was used to compare the proteomic profile of cases and controls and t-tests to detect differences in individual proteins (FDR 500 circulating proteins distinguishing the groups. These proteomic data identify widespread protein dysregulation across multiple biologic systems with promising biological plausibility as drivers of SVHD morbidity.