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Date of Award

2025

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Biomedical Engineering (PhD)

Administrative Home Department

Department of Biomedical Engineering

Advisor 1

Hoda Hatoum

Committee Member 1

Jingfeng Jiang

Committee Member 2

Fernando Ponta

Committee Member 3

Sean J. Kirkpatrick

Abstract

Cardiovascular diseases and their treatments can significantly alter blood flow dynamics, impacting patient outcomes. Understanding these flow changes is critical for optimizing device design, refining treatment strategies, and improving clinical decision making. This dissertation is divided into a flow dynamics assessment of the aorta and left atrium (LA).

Aortic stenosis (AS) is the most common valvular heart disease worldwide, with aortic valve replacement (AVR) being the only effective treatment. Hypertension (HTN) is common in patients with AS, and blood pressure (BP) often remains high after AVR. While HTN is typically associated with negative outcomes, it is actually lower BP, not higher, that has been linked to worse outcomes after AVR. The studies presented in this dissertation suggest that higher BP after AVR may help maintain sufficient epicardial coronary flow to prevent myocardial ischemia. However, elevated BP may also contribute to the initiation and acceleration of calcific changes in bioprosthetic leaflets, potentially leading to valve degeneration.

Bioprosthetic valve performance is an important factor following AVR. Benchtop testing of AVs often excludes the aortic arch, yet findings show that the arch has a pressure recovery zone, which is relevant for catheter-based pressure measurements of bioprosthetic valve performance. Lastly, stroke remains a major concern after AVR, with no clear predictors identified for stroke risk following transcatheter aortic valve replacement (TAVR). Stroke risk assessments in TAVR candidates revealed that anatomical and geometric parameters may serve as potential correlates of stroke after TAVR.

Atrial fibrillation (AF) is the most common arrhythmia worldwide and is associated with an increased risk of stroke. While catheter ablation can restore the heart to sinus rhythm, its impact on left atrial flow dynamics remains unclear. Flow assessments of the left atrium (LA) before and after ablation revealed distinct changes in flow mixing, vortex patterns, velocity, and wall shear stress (WSS) distributions, suggesting that ablation techniques may induce flow alterations that could be thrombogenic over time. The left atrial appendage (LAA) is a common site of thrombosis in AF patients, and its occlusion can help reduce stroke risk. However, a small percentage of patients develop device related thrombosis (DRT) after left atrial appendage occlusion (LAAO). Findings from the LAAO study indicated that DRT positive patients exhibited worse flow parameters at the atrial surface of the LAAO device, with regions of low time averaged WSS (TAWSS) closely aligning with clinically identified thrombus locations.

This dissertation work aims to improve our understanding of aortic and atrial flow dynamics in the context of cardiovascular disease and its treatment, bridging the communication gap between engineers and clinicians to facilitate the translation of engineering research into clinical practice.

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