In 10 infant patients with cyanotic or single-ventricle heart disease, patient-specific computational fluid dynamics modeling revealed that shunt insertion angle and diameter are primary geometric drivers of thrombogenic hemodynamics in the modified Blalock-Taussig-Thomas shunt (mBTTS). Peak wall shear rate (WSR) and elongational strain rate (ESR) consistently localized to the shunt-subclavian junction in 8 of 10 cases, including all 4 thrombosed shunts. Deviation from perpendicular insertion angle correlated strongly with elevated WSR (ρ = 0.94, p < 0.001) and ESR (ρ = 0.82, p = 0.007), while larger shunt diameter was protective.
This preprint, not yet peer-reviewed, addresses a genuinely lethal clinical gap. mBTTS thrombosis strikes 8–12% of an already critically vulnerable population — neonates whose pulmonary circulation depends entirely on the shunt's patency — and systemic anticoagulation has historically offered incomplete protection. The finding that a modifiable surgical parameter (insertion angle) mechanistically explains thrombogenic flow shifts the therapeutic frame from pharmacology toward intraoperative geometry optimization. Broader context matters here: computational hemodynamics has previously informed adult vascular graft design, but translating these principles to neonatal anatomy with individualized Windkessel-calibrated models represents meaningful methodological progress. Limitations are significant: the n=10 cohort is very small, restricting statistical power; causality cannot be confirmed from retrospective imaging; and simulation fidelity depends on model assumptions about blood rheology and wall compliance. If validated prospectively, this approach could enable real-time surgical decision support — a potentially paradigm-shifting application in congenital cardiac surgery.
