Date of Award

Fall 2008

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Olson, Lars

Second Advisor

Audi, Said

Third Advisor

Koo, Bon-Kwon

Abstract

One-third of deaths in the United States are caused by cardiovascular disease and coronary artery disease (CAD) accounts for 52% of these deaths. Interestingly, CAD often localizes at bends, branches and bifurcations throughout the vasculature. Stenting is the preferred treatment for CAD and has been applied to coronary bifurcation lesions with limited success due to high levels of restenosis. Hemodynamic parameters including time-averaged wall shear stress (TAWSS) and oscillatory shear.index (OSI) correlate with restenosis but are not easily measured clinically. Computational fluid dynamics (CFO) is a simulation technique utilizing clinical data, making it well-suited for studying hemodynamics in stented coronary bifurcations. The objective of this work is to develop methods whereby geometric models of stented coronary bifurcations can be created and simulated with CFO using realistic boundary conditions. Initially, idealized models were generated to quantify hemodynamics after stenting the main branch and following post-stenting side branch balloon dilation since these procedures cause pronounced changes in the location of the bifurcation blood flow divider (i.e. carina). The first patient-specific models of stented coronary bifurcations to date were then conducted to quantify altered hemodynamics with increased physiologic realism. Lastly, methods of expanding a simple stent model using finite element analysis (FEA) were implemented for future use with more complex bifurcation stenting techniques. Stenting increased distal main branch diameter causing skewing of the velocity profile and high TAWSS towards the carina in idealized models, while also introducing eccentric regions of low TAWSS along the opposing lateral wall. Post-stenting side branch balloon dilation restored the carina to its native position thereby alleviating a partial stenosis introduced by stenting, but resulted in concentric regions of low TAWSS and high OSI in the distal main branch. Areas of low TAWSS were observed near stent struts in all simulations, consistent with previous work. Importantly, decreased TAWSS and increased OSI have been shown to correlate with restenosis. Therefore, the current results may partially explain why restenosis rates remain high in stented bifurcation lesions, and be amenable to improved bifurcation stent designs. Future work will leverage the methods and initial FEA developments of this work for this purpose.

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