Non-Newtonian Endothelial Shear Stress Simulation: Does It Matter?

Vikas Thondapu; Daisuke Shishikura; Jouke Dijkstra; Shuang J Zhu; Eve Revalor; Patrick W Serruys; William J van Gaal; Eric K W Poon; Andrew Ooi; Peter Barlis

doi:10.3389/fcvm.2022.835270

Non-Newtonian Endothelial Shear Stress Simulation: Does It Matter?

Front Cardiovasc Med. 2022 Apr 14:9:835270. doi: 10.3389/fcvm.2022.835270. eCollection 2022.

Authors

Vikas Thondapu^{1

2

3}, Daisuke Shishikura⁴, Jouke Dijkstra⁵, Shuang J Zhu², Eve Revalor^{1

6}, Patrick W Serruys^{7

8}, William J van Gaal^{1

9}, Eric K W Poon¹, Andrew Ooi², Peter Barlis¹

Affiliations

¹ Department of Medicine, Faculty of Medicine, Melbourne Medical School, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC, Australia.
² Department of Mechanical Engineering, Melbourne School of Engineering, University of Melbourne, Parkville, VIC, Australia.
³ Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States.
⁴ Department of Cardiology, Osaka Medical and Pharmaceutical University, Osaka, Japan.
⁵ Department of Radiology, Division of Image Processing, Leiden University Medical Center, Leiden, Netherlands.
⁶ Department of Biomedical Engineering, Melbourne School of Engineering, University of Melbourne, Parkville, VIC, Australia.
⁷ Department of Cardiology, National University of Ireland Galway (NUIG), Galway, Ireland.
⁸ National Heart and Lung Institute, Imperial College London, London, United Kingdom.
⁹ Department of Cardiology, Northern Hospital, Epping, NSW, Australia.

Abstract

Patient-specific coronary endothelial shear stress (ESS) calculations using Newtonian and non-Newtonian rheological models were performed to assess whether the common assumption of Newtonian blood behavior offers similar results to a more realistic but computationally expensive non-Newtonian model. 16 coronary arteries (from 16 patients) were reconstructed from optical coherence tomographic (OCT) imaging. Pulsatile CFD simulations using Newtonian and the Quemada non-Newtonian model were performed. Endothelial shear stress (ESS) and other indices were compared. Exploratory indices including local blood viscosity (LBV) were calculated from non-Newtonian simulation data. Compared to the Newtonian results, the non-Newtonian model estimates significantly higher time-averaged ESS (1.69 (IQR 1.36)Pa versus 1.28 (1.16)Pa, p < 0.001) and ESS gradient (0.90 (1.20)Pa/mm versus 0.74 (1.03)Pa/mm, p < 0.001) throughout the cardiac cycle, under-estimating the low ESS (<1Pa) area (37.20 ± 13.57% versus 50.43 ± 14.16%, 95% CI 11.28-15.18, p < 0.001). Similar results were also found in the idealized artery simulations with non-Newtonian median ESS being higher than the Newtonian median ESS (healthy segments: 0.8238Pa versus 0.6618Pa, p < 0.001 proximal; 0.8179Pa versus 0.6610Pa, p < 0.001 distal; stenotic segments: 0.8196Pa versus 0.6611Pa, p < 0.001 proximal; 0.2546Pa versus 0.2245Pa, p < 0.001 distal) On average, the non-Newtonian model has a LBV of 1.45 times above the Newtonian model with an average peak LBV of 40-fold. Non-Newtonian blood model estimates higher quantitative ESS values than the Newtonian model. Incorporation of non-Newtonian blood behavior may improve the accuracy of ESS measurements. The non-Newtonian model also allows calculation of exploratory viscosity-based hemodynamic indices, such as local blood viscosity, which may offer additional information to detect underlying atherosclerosis.

Keywords: computational fluid dynamics – CFD; non-Newtonian; optical coherence tomography; rheology; shear stress (fluid); viscosity.