Effect of blood rheology on haemodynamics and stent-based drug delivery for coronary arteries

Given the significant influence of blood flow characteristics on haemodynamics and the drug transport from stents into arterial tissue, accurately simulating blood flow is essential in numerical studies of arteries, including those involving drug-eluting stents (DES). The complexity of near-wall blood behavior and the numerous rheological models available make blood modeling challenging. In addition, the wide variation in the geometric features of arteries, such as their diameter, can also significantly affect these simulations. On the other hand, the cross-section of the stent strut can also be influential, as it changes the streamlines of blood flow. This work involved comparing various non-Newtonian models with the conventional Newtonian model for coronary arteries using a series of steady-state computational fluid dynamics (CFD) evaluations. The drug transport behavior at different Reynolds numbers and hemodynamic features, like streamlines and wall shear stress (WSS), were analyzed to clarify the influence of these rheological models on both streamlined (semi-circular) and non-streamlined (square) strut cross sections. Furthermore, given that previous research indicated a negligible impact of blood rheology on drug delivery in larger arteries such as renal arteries, the results were compared with outcomes from renal arteries to determine if this holds for coronary arteries with smaller diameters. The results indicate that the smaller the artery, the more significant the role of blood rheology becomes. Specifically, the impact of blood rheology on drug uptake for square strut cross sections was approximately 20 % in coronary arteries, compared to just 5 % in renal arteries. However, the influence of blood rheology in coronary arteries with semi-circular strut profiles was negligible. Regarding haemodynamic features, recirculation lengths were considerably affected by both the Reynolds number and the selected blood rheological model, with these effects being more pronounced in smaller arteries and with square cross sections. Furthermore, the choice of blood viscosity model had a notable effect on the WSS distribution.