Morphometric and Mechanical Analyses of Calcifications and Fibrous Plaque Tissue in Carotid Arteries for Plaque Rupture Risk Assessment.

Frank J H Gijsen,Ali C Akyildiz,Amir A Zadpoor,Anton F W Van Der Steen,Bas Vis,Hilary E Barrett,Hence J Verhagen,Daniel Bos

doi:10.1109/tbme.2020.3038038

Morphometric and Mechanical Analyses of Calcifications and Fibrous Plaque Tissue in Carotid Arteries for Plaque Rupture Risk Assessment.

Frank J H Gijsen, Ali C Akyildiz + Show 6 more

Open Access

https://doi.org/10.1109/tbme.2020.3038038

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Abstract

Atherosclerotic plaque rupture in carotid arteries is a major source of cerebrovascular events. Calcifications are highly prevalent in carotid plaques, but their role in plaque rupture remains poorly understood. This work studied the morphometric features of calcifications in carotid plaques and their effect on the stress distribution in the fibrous plaque tissue at the calcification interface, as a potential source of plaque rupture and clinical events. A comprehensive morphometric analysis of 65 histology cross-sections from 16 carotid plaques was performed to identify the morphology (size and shape) and location of plaque calcifications, and the fibrous tissue fiber organization around them. Calcification-specific finite element models were constructed to examine the fibrous plaque tissue stresses at the calcification interface. Statistical correlation analysis was performed to elucidate the impact of calcification morphology and fibrous tissue organization on interface stresses. Hundred-seventy-one calcifications were identified on the histology cross-sections, which showed great variation in morphology. Four distinct patterns of fiber organization in the plaque tissue were observed around the calcification. They were termed as attached, pushed-aside, encircling and random patterns. The stress analyses showed that calcifications are correlated with high interface stresses, which might be comparable to or even above the plaque strength. The stress levels depended on the calcification morphology and fiber organization. Thicker calcification with a circumferential slender shape, located close to the lumen were correlated most prominently to high interface stresses. Depending on its morphology and the fiber organization around it, a calcification in an atherosclerotic plaque can act as a stress riser and cause high interface stresses. This study demonstrated the potential of calcifications in atherosclerotic plaques to cause elevated stresses in plaque tissue and provided a biomechanical explanation for the histopathological findings of calcification-associated plaque rupture.

Highlights

T HE majority of the cardiovascular events are caused by the rupture of atherosclerotic plaques, which may lead to ischemia in the organs located distally from the plaque [1]–[3]
For the encircling fiber pattern calcifications, there was an even distribution between the internal carotid (50%) and the common carotid region (50%), whereas the random fiber pattern cases were mainly located in the internal carotid artery (94%)
We studied the effects of arterial calcifications on the stress distribution in the fibrous plaque tissue at the calcification interface, as a potential source of plaque rupture in carotid arteries and clinical cerebrovascular events

Summary

Introduction

T HE majority of the cardiovascular events are caused by the rupture of atherosclerotic plaques, which may lead to ischemia in the organs located distally from the plaque [1]–[3]. Plaque stress analysis studies have provided mechanistic explanations for these histology findings by demonstrating that the enlargement of the lipid pool and/or the thinning of the cap may result in elevated plaque stresses [8]–[10], a functional marker of mechanical plaque instability [7], [11], [12]. Another highly prevalent structural component of atherosclerotic plaques is calcification [13].

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