Linking Eulerian-based wall shear stress topological skeleton to near-wall low-density lipoproteins and oxygen transport in arterial flow

Atherosclerosis is a systemic inflammatory disease of the large and medium-sized arteries that involves a characteristic accumulation of fatty material (e.g. lipid, cholesterol) on the inner surface of the vessel walls. This process leads to the formation of atherosclerotic plaques which in turn cause the hardening, thickening and loss of elasticity of the arterial wall. Mass transport in arteries plays a key role in vascular disease. In particular high levels of low-density lipoproteins (LDL) and low levels of oxygen in the arterial wall are involved in the atherosclerotic process. In addition to that, also hemodynamic factors, in particular wall shear stress (WSS), contribute to the onset and progression of atherosclerosis. For this reason, in the last decades, several descriptors have been proposed as hemodynamic markers of “disturbed flow” and personalized computational fluid dynamics (CFD) has been adopted to elucidate the links (if any) among disturbed flow, atherogenesis and mass transport in human arteries. In this context, a growing interest has recently emerged on WSS vector field topological skeleton, due to its ability to properly describe near-wall mass transfer, overcoming the main limitation represented by the high computational costs necessary to model mass transfer solving the conventional advection-diffusion equations. The present thesis aims to test the ability of a recently-proposed Eulerian-based method for the identification of WSS topological skeleton, to provide a reliable template of the near-wall mass transport in subject-specific computational hemodynamic models of human arteries. More in detail, in this study blood flow, together with LDL and oxygen mass transfer, was simulated using image-based CFD models of carotid bifurcation, right coronary artery (RCA) and left coronary artery (LAD). The relationship between the well-established WSS-based hemodynamic descriptors, WSS topological skeleton and the LDL/oxygen polarization at the vessel wall has been investigated through a co-localization analysis. The results confirm the ability of the Eulerian-based method for the identification of WSS topological skeleton to provide an effective template of the mass transport in arteries with a significative reduction of both the computational costs and the complexity of classical techniques.