Spatiotemporal blood viscosity by local hematocrit under pulsatile flow: Whole blood experiments and computational...

Blood viscosity is inversely proportionate with shear rate mainly due to red blood cell (RBC) aggregation under steady flow. However, this inverse relation cannot explain the spatiotemporal variation of RBC dynamics under pulsatile flow. This study aimed to clarify the relationship between hemodynamics and hemorheology based on a novel computational model that couples RBC dynamics with blood viscosity under pulsatile flow. By integrating both whole-blood experiments with ultrasound imaging and numerical simulations, the spatiotemporal variations of local hematocrit were shown to drive local variations of blood viscosity under pulsatile flow. The results suggest that the local parabolic distribution of high hematocrit is influenced by RBC aggregation and pulsatile flow characteristics, which in turn affect blood viscosity. Computational analysis supports that local blood viscosity increased in regions with elevated hematocrit during the acceleration phase of pulsatile flow. Local hematocrit and RBC dynamics play critical roles in influencing blood viscosity under pulsatile flow, highlighting the importance of incorporating hemorheological and hemodynamic factors. These are crucial for understanding large arterial flow and potentially enhancing diagnostic and therapeutic approaches for cardiovascular diseases.