Around 8% of all newborns with a Congenital Heart Defect (CHD) have only a single functioning ventricle. The Fontan operation has served as palliation for this anomaly for decades, but the surgery entails multiple complications, and the survival rate is less than 50% by adulthood. A rapidly testable novel alternative is proposed by creating a bifurcating graft, or Injection Jet Shunt (IJS), used to “entrain” the pulmonary flow and thus provide assistance while reducing the caval pressure. A dynamically scaled Mock Flow Loop (MFL) has been configured to validate this hypothesis. Three IJS nozzles of varying diameters 2, 3, and 4 mm with three aortic anastomosis angles and pulmonary vascular resistance (PVR) reduction have been tested to validate the hypothesis and optimize the caval pressure reduction. The MFL is based on a Lumped-Parameter Model (LPM) of a non-fenestrated Fontan circulation. The best outcome was achieved with the experimental testing of a 3 mm IJS by producing an average caval pressure reduction of more than 5 mmHg while maintaining the clinically acceptable pulmonary flow rate (Q_p) to systemic flow rate (Q_s) ratio of ~1.5. Furthermore, alteration of the PVR helped in achieving higher caval pressure reduction with the 3 mm IJS at the expense of an increase in Q_p/Q_s ratio.

Single ventricle (SV) anomalies account for one-fourth of all congenital heart disease cases. The existing palliative treatment for this anomaly achieves a survival rate of only 50%. To reduce the trauma associated with surgical management, the hybrid comprehensive stage II (HCSII) operation was designed as an alternative for a select subset of SV patients with the adequate antegrade aortic flow. This study aims to provide better insight into the hemodynamics of HCSII patients utilizing a multiscale Computational Fluid Dynamics (CFD) model and a mock flow loop (MFL). Both 3D-0D loosely coupled CFD and MFL models have been tuned to match baseline hemodynamic parameters obtained from patient-specific catheterization data. The hemodynamic findings from clinical data closely match the in-vitro and in-silico measurements and show a strong correlation (r = 0.9). The geometrical modification applied to the models had little effect on the oxygen delivery. Similarly, the particle residence time study reveals that particles injected in the main pulmonary artery (MPA) have successfully ejected within one cardiac cycle, and no pathological flows were observed.

Fontan circulation is a fragile system in which imperfections at any of multiple levels may compromise the quality of life, produce secondary pathophysiology, and shorten life span. Increased inferior vena caval pressure itself may play a role in “Fontan failure”. This study describes a mock flow loop model (MFL) designed to quantitatively estimate pulmonary flow entrainment induced by continuous and pulsed flow injections. A patient generic 3D-printed phantom model of the total cavopulmonary connection (TCPC) with average dimensions matching those of a 2–4-year-old patient was inserted in an MFL derived from a reduced lumped parameter model (LPM) representing cardiovascular circulation. The LPM comprises four 2-element Windkessel compartments (compliance and resistance), approximating the upper and lower systemic circulations and the right and left pulmonary circulations. The prescribed cardiac output is about 2.3 L/min for a body surface area of 0.675 m2. The injections originate from an external pump through a 7–9 fr catheter, following a strict protocol suggested by the clinical team, featuring a variation in injection rate (flow rate), injection volume, and injection modality (continuous or pulsed). The key measurements in this study are the flow rates sampled at the distal pulmonary arteries, as well as at the upper and lower body boundaries. These measurements were then used to calculate effective entrainment as the difference between the measured and expected flow rates, as well as jet relaxation (rise and fall time of injection). The results show that for continuous or pulsed injections, varying the total volume injected has no significant influence on the entrainment rate across all injection rates. On the other hand, for both injection modalities, increasing the injection rate results in a reduction in entrainment that is consistent across all injected volumes. This study demonstrates the effectiveness of a high-speed injection jet entraining a slow co-flow while determining the potential for fluid buildup, which could ultimately cause an increase in caval pressure. To avoid the increase in caval pressure due to mass accumulation, we added a fenestration to our proposed injection jet shunt-assisted Fontan models. It was found that for a set of well-defined parameters, the jet not only can be beneficial to the local flow, but any adverse effect can be obviated by careful tuning. These results were also cross-validated with similar in silico findings.

The U.S. Centers for Disease Control and Prevention estimates that approximately 1 in 4000 infants annually in the United States is born with a single functioning ventricle. Fontan surgery represents the final stage of palliation for these patients, yet elevated inferior vena cava (IVC) pressure remains a significant contributor to Fontan failure. We propose to energize the Fontan circulation with an injection jet shunt (IJS) drawing flow directly from the aortic arch balanced by a conduit-to-atrial fenestration. The high-velocity jet generated by the IJS induces flow entrainment, reducing upstream IVC pressure and enhancing downstream flow. The presence of a fenestration may decrease systemic oxygen content (CaO₂), depending on its size and its interaction with the IJS flow. Thus, oxygen tracking is critical to determining the optimal IJS-assisted Fontan models. In this feasibility study we describe a dynamically controlled mock flow loop model (MFL) designed to estimate, quantitatively and qualitatively, the volume fraction of IJS flow (VFijs) absorbed by the fenestration. An innovative light-induced fluorescence-based high-speed imaging technique was developed to quantify the volume fraction of VFijs diverted through a fenestration. A patient-generic 3D-printed total cavopulmonary connection (TCPC) surrogate phantom representing the anatomy of 2- to 4-year-old fenestrated Fontan patients was integrated into the MFL. The MFL incorporates a reduced lumped parameter model (LPM) with Windkessel compartments to simulate systemic and pulmonary circulations. To this end, a response surface based on a radial basis function (RBF) interpolation network trained by a proper orthogonal decomposition (POD) of the solution fields is developed for fast and accurate approximations of systemic blood volume fraction absorbed by the fenestration for various total cavopulmonary connection configurations. The POD−RBF method was used to spatially enhance the high temporal measurements (high frame rate [HFR]), and statistical comparisons were performed against the highly resolved spatial (Hi-Res) ground truth. The residual errors between the POD-RBF enhanced HFR fields and the Hi-Res measurements exhibited a Pearson correlation coefficient of approximately −0.41, a p value of .34, and a variance of 0.0002. These statistical results indicate no significant differences between the enhanced and hi-res fields, substantiating the robustness and feasibility of the proposed interpolation framework for high-fidelity, real-time systemic oxygen saturation estimation.