Hemodynamic Performance in Several Patient-Specific Fontan Anatomies

Approximately one in 3,000 children are born with a congenital heart defect characterized by a functional single ventricle. Patients may lack a heart valve, have an abnormality in pumping behavior, or have complex congenital heart defects. In many cases, the palliative Fontan operation is indicated, whereby blood flow from the vena cava is directly channeled into the pulmonary arteries, bypassing the morphological right heart. The surgery is performed typically before 5 years, and long-term patient outlooks are good, with a 12-year survival of 90% and 80% at 25 years. However, the hemodynamic performance of the patient-specific anatomy has been found to correlate strongly with patient outcomes such as exercise performance, and low cardiac output has been identified as the leading cause of death in these patients. Penn State is leading the development of a pump intended to improve cardiovascular performance in Fontan patients.

The aim of the current study is to quantify numerically the baseline hemodynamic performance for several patients with the later goal of performing simulations to determine the impact of implanting the Penn State Fontan pump. Patient morphologies are obtained by collaborators at the Children’s Hospital of Philadelphia via magnetic resonance imaging (MRI). The anatomies vary significantly. Inflow and outflow characteristics are reported in the MRI and are used to prescribe velocity boundary conditions. The fluid dynamics is modeled with pisoFoam with a Newtonian viscosity model. Outlet pressure boundary conditions are prescribed to preserve correct flow splits. Because Fontan patients have a heightened risk of pulmonary embolism, passive tracer species are used to track the destination of the flow from each inlet to investigate risk areas where emboli could lodge. Simulations are compared on the basis of their indexed power loss (IPL), an important clinical parameter correlated with patient outcomes.

The more complex geometries show larger indexed power loss, which may be indicative of higher risk of mortality. Given the higher clinical risks associated with poor hemodynamic efficiency in Fontan patients, the investigated patients with the most irregular circulations are most likely to benefit from circulatory support with an implanted pump. Future work will numerically investigate the implantation of such a pump into these anatomies to investigate improvements in power loss and mixing of blood from different inlets.