Cerebral ischemia leading to an ischemic stroke is a possible complication of a transcatheter aortic valve replacement (TAVR) procedure. This is because embolic debris can become dislodged and travel through the aortic arch, where they either continue to the descending aorta and join the systemic circulation or travel into the cerebral vasculature through the three daughter vessels that branch off the top of the aortic arch. These three vessels are the brachiocephalic artery, the left subclavian artery, and the left common carotid artery. These three vessels lead either directly or indirectly to the cerebral vasculature, where the diameter of vessels become very small. If a large enough embolus travels into the cerebral vasculature, it can become stuck in the small cerebral vessels, blocking blood flow and cutting off the supply of oxygen to brain cells. The purpose of this study is to expand upon previous work in order to 1) create a more accurate physics simulation of blood and debris flow through the aortic arch 2) report on embolic debris distribution through the aortic arch and 3) analysis on which physical parameters affect embolic debris distribution. The physical parameters analyzed were particle diameter and particle density. This study was performed by creating a finite element model in COMSOL Multiphysics™ using a SolidWorks model of an aortic arch, with dimensions taken from a patient’s CT scan. Computational fluid dynamics was performed using a pulsatile pressure waveform throughout the aortic arch with a non-constant viscosity model. Once the velocity profile through the aortic arch matched with value ranges from literature, the particle tracing study was implemented. Both a pulsatile pressure waveform and a constant pressure model were analyzed, as well as a constant viscosity model and a non-constant viscosity model. The pulsatile pressure waveform influenced particle distribution and is recommended for future studies since this model leads to pulsatile flow, which is representative of flow through the aorta. It was seen that the non-constant viscosity model did not have a large effect on the velocity profile, but more than doubled the surface average value of viscosity. It also had an effect on the particle distribution through the aortic arch. Small diameter emboli were more likely to flow into the descending aorta, the brachiocephalic artery, and the left subclavian artery; larger emboli were more likely to flow into the left common carotid. Lower density emboli were more likely to flow into the descending aorta and the brachiocephalic artery. Averaging all densities and sizes, it was determined 44.8% of emboli flow into the three daughter vessels, but ultimately only 30.61% of emboli flow into the cerebral vasculature and have the potential to cause an ischemic stroke.
| Identifer | oai:union.ndltd.org:CALPOLY/oai:digitalcommons.calpoly.edu:theses-3435 |
| Date | 01 June 2019 |
| Creators | Wirth, Jessica Lena |
| Publisher | DigitalCommons@CalPoly |
| Source Sets | California Polytechnic State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Master's Theses |
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