Multiscale Modeling of a Geometrically Tunable Shunt for Growing Pediatric Patients With Single Ventricle Physiology

Univentricular circulations are initially established with the placement of a fixed-diameter blood shunt to facilitate physiologic stability during growth. This fixed-diameter shunt (FDS) is geometrically static in a dynamically growth-driven environment. The neonatal cardiovascular hemodynamics are sensitive to the presence of the FDS and its fluidic and resistive properties, which creates significant interdependency and mortality risks. Thus, we have developed a geometrically tunable shunt to mitigate these hemodynamic challenges. Here, the tunable shunt is established by computational characterization of the hemodynamics over shunt usage in a patient specific anatomy.

Two multiscale cardiovascular models were implemented at time-points spanning across the beginning and end of the shunt-use period. These models were customized with patient-specific data from a clinical trial, drawing on observed geometric and fluidic conditions. A patient growth model between time-points was also established. For two patients, the tunable shunt was simulated across those time-points to identify the appropriate diameter changes that produced favorable hemodynamic conditions, per the pulmonary-to-systemic flow ratio (Q_P/Q_S).

Changes in vessel morphology, cardiac output, and vascular resistance were characterized and represented growth in the shunt-use period. Compared to the diameter at the beginning of the shunt-use period, a diameter expansion of 12%-13% was required at the end of the shunt-use period to balance the Q_P/Q_S for optimal blood oxygenation.

These models are among the first to computationally study clinical time-points early in the post-operative univentricular patient. Using a complex model of growth, the tunable shunt design was investigated for its potential to alter and maintain hemodynamics over the growth months of infancy. These findings advanced the development of an innovative, tunable blood shunt for high-risk patients with complex congenital heart disease.