The First Human-Based In Vitro Flow Loop and Quantification for Fetal Aortic Hemodynamics
Coarctation of the aorta (CoA) is a common congenital defect that remains difficult to diagnose prenatally due to subtle and evolving anatomical features. In the fetus, the ductus arteriosus creates a dual-inflow configuration that generates complex three-dimensional flow patterns not captured by standard imaging. Improved characterization of fetal hemodynamics may enhance diagnostic accuracy beyond anatomy-based assessment. This study presents the first human-based in vitro flow loop of the fetal aorta, constructed from anatomies reconstructed using medical imaging data. Models representing normal and coarctation conditions were fabricated and integrated into a physiological flow loop. Velocity fields were measured using planar and stereoscopic particle image velocimetry (PIV) to resolve near-wall and three-dimensional flow structures, enabling quantitative assessment of velocity gradients and wall shear stress (WSS) under normal and coarctation configurations. The in vitro flow loop closely reproduced target fetal flow segmentation, with segmental flow-rate errors generally below 6%. High-resolution planar and stereoscopic PIV revealed dual jets from the ascending aorta and the ductus arteriosus and predominantly planar flow in the normal aorta, but strong jet acceleration, separation, and reattachment in the coarcted geometry. Coarctation produced markedly elevated and spatially heterogeneous WSS, and 2-component PIV underestimated WSS by up to ~29% compared with 3-component measurements, especially in high-shear regions. These findings show that accurate three-component velocity measurements are critical for reliable WSS estimation and suggest that detailed hemodynamic metrics, such as WSS, may serve as potential biomarkers to enhance fetal CoA diagnosis beyond anatomy alone.