Numerical study of wall shear stress-based descriptors in the human left coronary artery

Abstract

The present work is about the application of wall shear stress descriptors – time averaged wall shear stress (TAWSS), oscillating shear index (OSI) and relative residence time (RRT) – to the study of blood flow in the left coronary artery (LCA). These descriptors aid the prediction of disturbed flow conditions in the vessels and play a significant role in the detection of potential zones of atherosclerosis development. Hemodynamic descriptors data were obtained, numerically, through ANSYS® software, for the LCA of a patient-specific geometry and for a 3D idealized model. Comparing both cases, the results are coherent, in terms of location and magnitude. Low TAWSS, high OSI and high RRT values are observed in the bifurcation – potential zone of atherosclerosis appearance. The dissimilarities observed in the TAWSS values, considering blood as a Newtonian or non-Newtonian fluid, releases the importance of the correct blood rheologic caracterization. Moreover, for a higher Reynolds number, the TAWSS values decrease in the bifurcation and along the LAD branch, increasing the probability of plaques deposition. Furthermore, for a stenotic LCA model, very low TAWSS and high RRT values in front and behind the stenosis are observed, indicating the probable extension, in the flow direction, of the lesion.

Keywords:

• Left coronary artery
• stenosis
• computational fluid dynamics
• time average wall shear stress
• oscillating shear index
• relative residence time

Acknowledgements

The authors gratefully acknowledge the financial support of Fundação para a Ciência e Tecnologia (FCT) under project PTDC/EME-MFE/102974/2008 and post-doctoral grant SFRH/BPD/78262/2011. POCTI (FEDER) also supported this work via CEFT. The authors also thank all the cardiovascular medical team of Vila Nova de Gaia/Espinho Hospital.