Evolving hemodynamics in Fontan circulation: age-driven insights in patients with interrupted inferior vena cava and hepatoazygos shunt

Patients with interrupted inferior vena cava (I-IVC) and azygos continuation who undergo Fontan completion via hepatoazygos shunting exhibit unique hemodynamic challenges. This study evaluates age-related shifts in systemic venous return dominance, hepatic flow distribution (HFD), power loss (PL), and flow disturbances using patient-specific computational fluid dynamics (CFD). Data analysis from 95 patients with I-IVC showed a nonlinear shift in upper-to-lower body systemic flow dominance with ratios of 2, 1, and 0.5 (correlating to ages ∼3, ∼10, and ∼20, respectively). CFD simulations for 17 selected patients revealed a trend of increasing HFD toward the right pulmonary artery, with median splits of 45%-49%, 48%-52%, and 40%-60% for the respective flow ratios. Power loss increased significantly with lower-body flow dominance. Median values for absolute PL were 4.75 mW (ratio 2), 16.5 mW (ratio 1), and 33.7 mW (ratio 0.5). Indexed PL showed a similar trend, rising from 0.04 mW/m² to 0.11 mW/m² across the flow ratios. Vorticity and viscous dissipation rates, key metrics of flow disturbances, also increased with lower-body flow dominance, showing strong correlations with PL (<i>R</i> = 0.58-0.76). Kruskal-Wallis-based statistical analysis identified significant statistical differences in absolute PL (<i>P</i> = 0.0045) and flow disturbances (<i>P</i> < 0.001), emphasizing the impact of age-related flow dynamics on Fontan efficiency. Our findings emphasize the need for targeted interventions in patients with I-IVC with azygos continuation to mitigate evolving hemodynamic inefficiencies and optimize Fontan outcomes during critical growth periods.<b>NEW & NOTEWORTHY</b> Evaluate how age-driven changes in patients with interrupted inferior vena cava impact Fontan efficiency. Using patient-specific computational fluid dynamics, our study reveals nonlinear flow dynamics, increasing power loss, and evolving hepatic flow distribution, emphasizing the need for tailored interventions to optimize outcomes.