Impact of blood rheology on left heart haemodynamics: Newtonian vs. non-Newtonian modelling

Although blood exhibits non-Newtonian properties, it is often modelled as a Newtonian fluid in numerical studies. However, the impact of this assumption on the accuracy of the predictions of computational models is not thoroughly assessed. For this reason, in this work, we compare the effect of Newtonian and shear-thinning blood rheological models on computational haemodynamics in the left heart. The analysis is based on the fluid–structure-electrophysiology interaction (FSEI) within a patient-specific anatomy of an individual with low ejection fraction to better highlight viscosity changes at low strain rates. Owing to the pulsatile nature of the flow, considerable spatio-temporal variations of the kinematic viscosity are observed for the non-Newtonian case. Integral quantities as well as blood pressure within the cardiac chambers are found to be weakly affected by the rheological model. Substantial differences are reported, instead, between the Newtonian and non-Newtonian cases, for the wall shear stress and local haemolysis index since they are sensitive to the local kinematic viscosity, which decreases within the shear layers of the systolic and diastolic jets, as well as in the near-wall regions.