Modeling Flow Characteristics in Carotid Artery Bifurcation Afflicted with Atherosclerotic Plaques
Braun, Alexandra; Ford, Stellie Justin; Shumakovich, Marina; Sonnenfeldt, Alden
Atherosclerosis is a condition characterized by the hardening of arteries due to the buildup of fatty substances, dead monocytes, and oxidized LDL particles. In advanced cases, atherosclerotic plaques form within artery walls which results in arterial narrowing. In the worst case scenario, the plaque ruptures causing blood clotting and the complete blockage of blood flow. Heart attacks and strokes can result from this event, depending on the site of the blockage. Atherosclerotic plaque rupture in a carotid artery can be catastrophic because a blockage in a carotid will cut off a primary source of blood to the brain. The goal of this project was to model the blood flow in the bifurcation point of the carotid artery and use COMSOL particle tracing to deposit and add a plaque. Additionally, this project seeks to analyze the effects using aspirin, a blood thinner, as a commonly recommended treatment for patients suffering from atherosclerosis on blood pressure, blood flow, and shear rate in the bifurcation point of a carotid artery with a plaque. Aspirin reduces blood viscosity and facilitate flow, thereby potentially reducing some of the health risks associated with atherosclerosis. The following assumptions were made to allow for COMSOL implementation: the cardiac output is constant; the artery is rigid and non-compliant; all fluid properties are estimated; blood is a uniform Newtonian fluid; treatments and preventative measures affect only a single aspect of fluid flow; and blood follows laminar flow pattern. To interpret the model, it was important to consider the potential sources of error. Most of the error originated from the physical approximation from the assumptions listed above. Out of these assumptions, the rigid non-compliant artery simplification was likely the single largest source of error. Additionally, a small amount of error is introduced by COMSOL’s interpolation between discrete points. Despite the error, the results of this project were consistent with experimental data in literature. Particle tracing and velocity profiles demonstrated that a plaque would most likely form in the internal carotid. By iteratively repeating building the plaque using particle tracing as a guide, three representative geometries (34%, 50%, and 55% stenosis) were created to compare to the healthy artery. It was then determined that the reduction in viscosity due to aspirin decreased the shear rate at the walls causing less stress on the artery. Similar effects of blood pressure reduction and exercise increase were observed in this model. This project could be advanced in the future if the vessels could be modeled as compliant and the blood could be modeled as a non-Newtonian fluid.
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