BACKGROUND: The modified Blalock-Taussig-Thomas shunt (mBTTS) is a critical palliative procedure for infants with single-ventricle physiology, but thrombosis-related occlusion affects 8-12% of cases and carries nearly 50% mortality. Meanwhile, existing antithrombotic strategies fail to address the hemodynamic factors driving thrombosis, highlighting the need for a deeper understanding of flow dynamics in shunt failure. OBJECTIVES: This study aims to identify how mBTTS geometry influences hemodynamics and thrombosis risk, providing quantitative guidance for surgical planning and shunt design optimization. METHODS: We used patient-specific imaging data to construct 54 idealized mBTTS configurations, systematically varying key geometric factors
pulmonary artery diameter, shunt diameter, and insertion angle. Using computational fluid dynamics, we analyzed how these variables influence wall shear rate (WSR), elongational strain rate (ESR), and turbulence intensity (TI)
hemodynamic parameters known to affect thrombosis risk, to identify patterns linked to thrombosis. RESULTS: We computationally identified optimal geometric configurations. Peak WSR and ESR were primarily located at bifurcation points, while peak TI was concentrated within the shunt channel. Shunt insertion distal to the right carotid artery with a 60° insertion angle and with a 4.0mm shunt graft demonstrated the most favorable hemodynamic profiles to prevent clots. Statistical analysis confirmed strong correlations between geometric parameters and flow characteristics. CONCLUSION: Results provide a framework for optimizing mBTTS design to reduce thrombosis risk based on hemodynamic risk factors, including actionable recommendations for shunt placement and design. These insights provide a foundation for hemodynamically guided surgical interventions with potential to improve survival rates in this high-risk patient population and for broader applications in cardiovascular surgery.