Perturbations of tryptophan catabolism via the kynurenine pathway are associated with stage 2 postoperative outcomes in single ventricle heart disease.

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.