Investigating the effect of aortic valve inflow profile in ascending thoracic aortic aneurysm

Abstract

Ascending thoracic aortic aneurysm is a dangerous condition which is hard to locate in patients. CFD can be used to assess someone’s risk of suffering from such an aneurysm and also to assess any possible relation of an aneurysm with relevant parameters, like the shape of the aorta or how blood flows into the aorta.

Existing research on ascending aortic CFD flow generally focuses on assessing relatively high wall shear stress, seen as the cause for aortic wall damage and aneurysms, in patients and not much on any possible relationships between aortic shape and inflow with ascending aortic aneurysm. Work that does exist often uses 4D flow MRI, shown to produce results regarding peak wall shear stresses with less accuracy compared to CFD.

This thesis aims to supply that information using an aortic geometry from a large dataset of synthetically generated aortas together with synthetically generated inlet velocity profiles, showing a possibility to work with-out the need for patient measurements. The main work in this thesis focuses on finding any possible relationship between aortic inflow angle and relatively high wall shear stress, such that the results may better explain how aortic inflow can influence the appearance of aneurysms.

For this, a workflow has been established that allows working with large aortic geometry and inflow profile datasets with relative ease. This workflow process uses a mix of OpenFoam and Ansys Fluent usage.

Results have shown that the flow jet angle in the core of the flow has a significant negative correlation with peak WSS within the ascending aorta for the chosen aortic geometry. This is in contrast with other work showing positive correlations with WSS. This may suggest aortic geometry dependence together with the need to look at other flow variables, like jet impingement angle, to explain how aortic inflow can influence high WSS within the ascending aorta.

Recommendations for future work include: The same study but with a focus on aortas of healthy young people to see if aortas at risk can be found, as existing work mainly focuses on old people with ascending thoracic aortic aneurysm, a similar study with a focus on the inclusion of various aortic geometries to find how aortic geometry may influence the effect inflow variables can have on high WSS, the creation of a tool to easily calculate the impingement angle from aortic flow data and research into if aortic jet flow disruption could reduce peak WSS in the ascending aorta for use in aortic reconstruction.