Transposition of the great arteries with ventricular septal defect and pulmonary stenosis: Hemodynamic simulation for palliative strategies.

Background: Transposition of the great arteries (TGA) with ventricular septal defect (VSD) and pulmonary stenosis (PS) presents complex hemodynamic challenges, frequently requiring staged palliative interventions. To inform optimal treatment strategies, we developed computational cardiovascular models to simulate the hemodynamics of TGA/VSD/PS. Methods: These models yielded critical hemodynamic parameters, including systemic oxygenation, pulmonary-to-systemic flow ratio (Qp/Qs), and mean pulmonary artery pressure (mPAP). By modulating resistances of the atrial septal defect (ASD), systemic-to-pulmonary shunt (SPS), and PS, we evaluated the impacts of diverse palliative interventions, such as ASD enlargement, SPS placement, and pulmonary artery banding (PAB). Results: Our model with severe PS revealed that a moderate or larger ASD or SPS is indispensable for achieving adequate blood mixing and systemic oxygenation. Both ASD enlargement and SPS placement enhanced oxygenation; however, ASD enlargement resulted in a smaller increase in Qp/Qs and a reduction in mPAP, fostering hemodynamic stability. The combined application of SPS and PAB demonstrated superior efficacy in reducing Qp/Qs and mPAP compared to SPS placement alone. The analysis of ASD flow patterns revealed that an inadequate ASD size accentuated the late component of ventricular systolic left-to-right flow (σ-wave), resulting in a square-shaped pattern, independent of SPS or PS. Echocardiographic flow patterns thus present a clinical reliable indicator of ASD adequacy beyond morphologic assessment. Conclusions: These findings support a palliative treatment strategy in which percutaneous ASD enlargement is prioritized, guided by echocardiographic ASD flow patterns. If adequate ASD enlargement cannot be achieved, SPS placement should be performed, with concomitant consideration of PAB.