Study on Wall Shear Stress Changes in the Aortic Arch and Isthmus in Fetuses With Aortic Coarctation Using Vector Flow Mapping

To evaluate segmental peak systolic wall shear stress (WSS_max) in the aortic arch and isthmus of fetuses with coarctation of the aorta (CoA) and to explore its relationships with conventional anatomical and hemodynamic parameters.

This prospective study included 58 CoA fetuses and 58 gestational age-matched normal controls. Vector flow mapping measured WSS_max at the inner and outer curvatures of the aortic arch and isthmus. Within the CoA group, Spearman correlation was used to assess relationships between isthmus WSS_max and the isthmus Z-score, PA/AO, TV/MV, isthmus V_max, and RV/LV. Multivariable linear regression was performed using the isthmus Z-deficit (-Z), PA/AO, and isthmus V_max.

Arch WSS_max did not differ between groups (all p > 0.05). Isthmus WSS_max (general, inner, and outer curvature) was significantly higher in the CoA group than in controls (all p < 0.05). Within the CoA group, isthmus WSS_max was lower than arch WSS_max (all p < 0.05). Isthmus WSS_max was correlated with the isthmus Z-score, PA/AO, and isthmus V_max. In multivariable regression, isthmus Z-deficit (B = 0.271, 95% CI 0.031-0.510, p < 0.05) and isthmus V_max (B = 0.01, 95% CI 0.001-0.020, p < 0.05) were independently associated with isthmus WSS_max, whereas PA/AO was not significant (p > 0.05).

Isthmus WSS_max is elevated in fetuses with CoA and is independently associated with greater isthmus hypoplasia and higher isthmus flow velocity, suggesting a role in CoA pathophysiology. Its incremental diagnostic value could not be assessed because the control group consisted of normal fetuses. WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?: Prenatal diagnosis of aortic coarctation (CoA) has a high false‑positive rate. Hemodynamic changes in CoA include increased velocity and turbulence, but biomechanical assessment in fetuses is limited. WHAT DOES THIS STUDY ADD?: This study uses VFM to quantify WSS_max in the fetal aortic arch and isthmus. Isthmus WSS_max is significantly elevated in fetuses with CoA and is independently associated with greater isthmus hypoplasia and higher isthmus flow velocity, providing mechanistic insights into the biomechanical alterations of fetal CoA.