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 (HAS) 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 I-IVC patients showed a non-linear 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 (RPA), 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 (VOR) and viscous dissipation rates (VDR), key metrics of flow disturbances, also increased with lower-body flow dominance, showing strong correlations with PL (R = 0.58–0.76). Kruskal-Wallis based statistical analysis identified significant statistical differences in absolute PL (p = 0.0045) and flow disturbances (p < 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.