Optical Coherence Tomography Based Biomechanical Fluid-Structure Interaction Analysis of Coronary Atherosclerosis Progression

Summary

There is a need to determine which atherosclerotic lesions will progress in the coronary vasculature to guide intervention before myocardial infarction occurs. This article outlines the biomechanical modeling of arteries from Optical Coherence Tomography using fluid-structure interaction techniques in a commercial finite element solver to help predict this progression.

Abstract

In this paper, we present a complete workflow for the biomechanical analysis of atherosclerotic plaque in the coronary vasculature. With atherosclerosis as one of the leading causes of global death, morbidity and economic burden, novel ways of analyzing and predicting its progression are needed. One such computational method is the use of fluid-structure interaction (FSI) to analyze the interaction between the blood flow and artery/plaque domains. Coupled with in vivo imaging, this approach could be tailored to each patient, assisting in differentiating between stable and unstable plaques. We outline the three-dimensional reconstruction process, making use of intravascular Optical Coherence Tomography (OCT) and invasive coronary angiography (ICA). The extraction of boundary conditions for the simulation, including replicating the three-dimensional motion of the artery, is discussed before the setup and analysis is conducted in a commercial finite element solver. The procedure for describing the highly nonlinear hyperelastic properties of the artery wall and the pulsatile blood velocity/pressure is outlined along with setting up the system coupling between the two domains. We demonstrate the procedure by analyzing a non-culprit, mildly stenotic, lipid-rich plaque in a patient following myocardial infarction. Established and emerging markers related to atherosclerotic plaque progression, such as wall shear stress and local normalized helicity, respectively, are discussed and related to the structural response in the artery wall and plaque. Finally, we translate the results to potential clinical relevance, discuss limitations, and outline areas for further development. The method described in this paper shows promise for aiding in the determination of sites at risk of atherosclerotic progression and, hence, could assist in managing the significant death, morbidity, and economic burden of atherosclerosis.

Introduction

Coronary artery disease (CAD) is the most common type of heart disease and one of the leading causes of death and economic burden globally^1,2. In the United States, roughly one in every eight deaths is attributed to CAD^3,4, while most global deaths from CAD are now seen in low- and middle-income countries⁵. Atherosclerosis is the predominant driver of these deaths, with plaque rupture or erosion leading to coronary artery occlusion and acute myocardial infarction (AMI)⁶. Even after revascularization of cu....

Protocol

The following deidentified data was analyzed from a patient recruited into the ongoing COCOMO-ACS randomized-controlled trial (ACTRN12618000809235; Royal Adelaide Hospital HREC reference number: HREC/17/RAH/366), with additional ethics approval granted by Central Adelaide Local Health Network (CALHN) Research Services for the purpose of biomechanical simulation (CALHN Reference Number 14179). Figure 1 summarizes the complete workflow outlined in the following protocol, which can be applied to any FSI capable software or codes.

1. Image evaluation

1. Match baseline and OCT follow-up ima....

Results

Representative results are presented for both established and emerging biomechanical markers of atherosclerosis progression. Established metrics such as WSS and WSS-derived results (including time averaged wall shear stress (TAWSS) and oscillatory shear index (OSI)) are visualized in Figure 10. The wall shear stress over the cardiac cycle is largely driven by the blood velocity, however, artery geometry and its motion/contraction play a significant role in its spatial distribution. This can .......

Discussion

The use of FSI methods to analyze coronary biomechanics is still a developing field from both numerical modelling and clinical result aspects. Here we have described the outline of setting up a patient specific FSI analysis, based on the finite element/finite volume methods, utilizing OCT and angiographic imaging. While the method we describe here utilizes a commercial finite element solver, the procedure can be applied to any FSI capable software. There are still several limitations to be improved upon in the methodolog.......

Materials

Name	Company	Catalog Number	Comments
ANSYS Workbench (version 19.0)	ANSYS		Commercial finite element solver
MATLAB (version 2019b)	Mathworks		Commercial programming platform
MicroDicom/ImageJ	MicroDicom/ImageJ		Open Source DICOM reader
Visual Studio (version 2019)	Microsoft		Commercial Integrated Development Environment