Association Between Hemodynamic Parameters and Gut Microbiota in Fontan Circulation: A Cross‐Sectional Study

BACKGROUND: The Fontan operation results in chronic hemodynamic alterations, including central venous hypertension, which may contribute to gut dysbiosis. This study aimed to compare gut microbiota profiles between Fontan patients and age- and sex-matched healthy controls and to examine how catheter-measured hemodynamic and liver-related parameters relate to microbial alterations. METHODS: This cross-sectional study enrolled 23 Fontan patients and 23 matched controls. Fontan patients underwent cardiovascular assessments, and stool samples were collected from all participants. Gut microbiota profiles were analyzed using 16S rRNA gene sequencing. RESULTS: Compared with controls, Fontan patients exhibited distinct gut dysbiosis, with lower evenness and significant shifts in beta-diversity. Fontan patients had higher relative abundances of inflammation-associated taxa and lower abundances of short-chain fatty acid-producing or commensal genera. Higher catheter-measured pulmonary and Fontan-circuit pressures and greater transpulmonary gradients were associated with lower microbial diversity and depletion of several beneficial taxa. In contrast, better liver status-reflected by higher serum albumin-coincided with more favorable microbial profiles. CONCLUSIONS: Fontan patients show a characteristic pattern of gut microbiota disruption that parallels their hemodynamic and hepatic burden. Treating Fontan-related pressures as continuous variables revealed graded associations among circulatory congestion, liver involvement, and gut dysbiosis, supporting a hemodynamic-gut-liver axis in Fontan physiology. Specific bacteria may serve as potential microbial biomarkers for identifying patients at higher risk and for guiding therapeutic interventions aimed at improving clinical outcomes.