Effect of the carotid geometry on the onset of atherosclerotic plaques

Atherosclerosis is an inflammatory cardiovascular disease that leads to a gradual narrowing of blood vessels due to the formation of plaques inside the artery. The plaques result from the accumulation of lipidic substances over the years and could obstruct the blood flow to downstream vessels and organs. We aim to predict through Computational Fluid Dynamics (CFD) simulations the possible onset of carotid plaques and to analyze the influence of hemodynamic and geometric parameters on the early stages of the disease. 

We combine CFD simulations with two different plaque growth models: the Wall Shear Stress (WSS) model that correlates the thickening of the innermost intimal layer of the arterial vessel to the CFD-computed wall shear stress exerted on the wall through a linear algebraic relation; and the Low-Density Lipoprotein (LDL) model that considers also the first phases of the inflammation process of the pathology, in which ordinary differential equations describe the plaque growth linked to the wall shear stress and to LDL concentration in the intima. For both cases, the thickening of the intima normal to the wall towards the arterial lumen is considered through a morphing procedure. We found in our previous studies that both models accurately predict the onset region of the disease and that the LDL model better estimates the plaque growth rate in the early stages of the pathology.

We consider herein a clinical dataset including the 3D segmented geometries of left and right carotids and the flow rate waveforms in common, external, and internal carotid arteries. From the patient-specific case, we build a parametric geometry to single out which among the different geometrical parameters describing the carotid bifurcation is responsible for the possible onset and growth of the arteriosclerotic plaque. Continuous response surfaces in the parameter space are obtained by using the stochastic collocation methods with sparse grids.