Investigation of an Injection-Jet Self-Powered Fontan Circulation: A Novel Bridge and Destination Therapy for the Failing Fontan

A structurally normal heart consists of two separate pumping chambers, or ventricles. One pumps deoxygenated blood from the body to the lungs, while the other delivers oxygenated blood from the lungs to the body. Approximately 8% of all newborns with a congenital heart defect have only a single functioning ventricle (SV). These patients cannot survive without a series of staged palliative operations to ensure adequate blood flow to both the pulmonary and systemic circulations. The final step in this staged reconstruction is the Fontan operation. While lifesaving, this unique physiology directs systemic venous return passively into the pulmonary arteries without the need for a subpulmonary pump. This results in chronically elevated central venous pressure and reduced cardiac output. Over time, this non-physiologic flow leads to significant morbidity, including hepatic fibrosis, protein-losing enteropathy, and Fontan-associated liver disease. A 2018 study of 683 adult Fontan patients from the Australian and New Zealand Fontan Registry reported 20% mortality by age 40, with only 53% free of heart failure symptoms and 41% free of serious adverse events. Similar outcomes have been documented worldwide, with nearly half of the observed morbidity and mortality attributed directly to failure of the unique Fontan circulatory system. To address this growing clinical challenge, our team is developing a novel, surgically implantable Injection-Jet Shunt (IJS) as a passive support strategy for patients with a failing Fontan circulation. This approach challenges the prevailing paradigm that mechanical pumps are the only viable support option for this population. Our proposed mechanism utilizes an intra-corporeal, surgically feasible shunt that harnesses the patient’s own cardiac power to inject a high-velocity jet from the aorta into the Fontan conduit. This jet entrains ambient inferior vena cava (IVC) flow, facilitating momentum transfer into the pulmonary circuit and unloading proximal venous pressure, all without any external power source. Multi-scale CFD simulations have demonstrated that this mechanism can lower Fontan pressure by 3 to 4 mmHg while maintaining clinically acceptable systemic oxygen saturations. These encouraging in-silico findings are currently being cross-validated in-vitro using a dynamically calibrated MCL that replicates Fontan hemodynamics under both resting and simulated exercise conditions. To characterize the flow behavior and jet entrainment dynamics of the Injection-Jet Shunt (IJS), the experimental MCL integrates both Particle Image Velocimetry (PIV) and Light-Induced Fluorometry (LIF) systems. PIV enables high-resolution quantification of velocity fields and shear layers, while LIF captures real-time oxygen transport in benchtop Fontan surrogates, allowing for the assessment of systemic flow distribution and entrained volume fractions. A Proper Orthogonal Decomposition trained Radial Basis Function (POD-RBF) interpolation framework is applied to reconstruct and enhance the spatiotemporal flow fields. This combined optical and data-driven approach enables detailed mapping of jet structure, entrainment efficacy, and pulmonary perfusion, supporting the optimization of IJS configurations for future clinical translation. If successful, the IJS may provide a low-risk, fully passive alternative to conventional mechanical support, potentially delaying or obviating the need for heart transplantation and improving quality of life for children and young adults with single-ventricle physiology.