Biomechanical Analysis of Age-Dependent Changes in Fontan Power Loss

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Pediatric Cardiology

Background:

• Fontan circulation hemodynamics are crucial for single-ventricle patients, relying on efficient flow and energetics.
• Age-related changes in Fontan procedure energetics, particularly for extracardiac conduits (ECC) and lateral tunnels (LT), are not fully understood.
• Vorticity (VOR) and viscous dissipation rate (VDR) are key metrics for analyzing flow dynamics and energy loss within Fontan pathways.

Purpose of the Study:

• To investigate the correlation between power loss (PL) and spatio-temporal flow descriptors (vorticity and VDR) in Fontan patients.
• To analyze how age-dependent changes in caval inflow affect Fontan energetics.
• To compare hemodynamic performance between extracardiac conduits and lateral tunnel Fontan procedures across different age groups.

Main Methods:

• Utilized data from 414 Fontan patients to establish the relationship between superior vena cava (SVC) to inferior vena cava (IVC) flow ratio and age.
• Performed computational flow modeling on ECC (n=16) and LT (n=25) Fontan pathways at caval inflow ratios of 2, 1, and 0.5, corresponding to ages 3, 8, and 15+.
• Correlated power loss with vorticity and viscous dissipation rate in both ECC and LT cohorts.

Main Results:

• Both vorticity and VDR showed strong correlations with power loss in all age groups for both ECC and LT Fontan procedures.
• The extracardiac conduit cohort demonstrated a slightly stronger correlation between power loss and vorticity/VDR compared to the lateral tunnel cohort.
• Absolute and indexed power loss increased non-linearly with age-related changes in caval inflow, exhibiting significant patient-specific variability.
• No statistically significant differences in indexed power loss were observed between ECC and LT cohorts across examined inflow ratios.
• A consistent rise in the pressure gradient across the total cavopulmonary connection (TCPC) was noted with increasing age and IVC flows in both ECC and LT patients.

Conclusions:

• Age-dependent changes in caval inflow significantly impact Fontan energetics, influencing power loss and pressure gradients.
• Vorticity and viscous dissipation rate serve as valuable indicators for assessing Fontan circulation energetics and long-term hemodynamic performance.
• The findings provide a framework for evaluating the sustainability of Fontan circulation and can inform the design of more efficient Fontan conduits.