Non-Newtonian Blood Rheology Significantly Alters Hemodynamic Predictions During Cardiac Looping: A Computational Study

Hemodynamic forces play a key role in early cardiac morphogenesis, yet many computational studies assume Newtonian blood behavior. Here, we evaluate the impact of non⍰Newtonian shear⍰thinning rheology on flow patterns, pressure distributions, and wall shear stress (WSS) during cardiac looping using idealized three⍰dimensional models of the embryonic heart tube. Five geometries representing progressive looping stages, from a linear tube to an S⍰shaped configuration with ventricular ballooning, were analyzed under pulsatile flow using both Newtonian and power⍰law viscosity models. Across all stages, Reynolds numbers (Re ≈ 1–7) and Womersley numbers (Wo ≈ 0.3) indicated laminar, quasi⍰steady flow consistent with embryonic conditions. Incorporating shear⍰thinning rheology produced substantial deviations from Newtonian predictions, with peak systolic WSS differing by up to ∼40% and pressure drops by up to ∼20%. These effects were most pronounced in regions of increased curvature and geometric complexity. These findings demonstrate that non⍰Newtonian rheology significantly influences predicted hemodynamic environments during cardiac looping and should be incorporated into computational models aimed at understanding mechanobiological regulation of early heart development.