Plaque hemorrhage in carotid artery disease: pathogenesis, clinical and biomechanical considerations

Abstract

Stroke remains the most prevalent disabling illness today, with internal carotid artery luminal stenosis due to atheroma formation responsible for the majority of ischemic cerebrovascular events. Severity of luminal stenosis continues to dictate both patient risk stratification and the likelihood of surgical intervention. But there is growing evidence to suggest that plaque morphology may help improve pre-existing risk stratification criteria. Plaque components such a fibrous tissue, lipid rich necrotic core and calcium have been well investigated but plaque hemorrhage (PH) has been somewhat overlooked. In this review we discuss the pathogenesis of PH, its role in dictating plaque vulnerability, PH imaging techniques, marterial properties of atherosclerotic tissues, in particular, those obtained based on in vivo measurements and effect of PH in modulating local biomechanics.

Keywords: Atheroma; Atherosclerosis; Carotid; Hemorrhage; MRI; Mechanics; Stroke.

Fig. 1

Atherosclerotic plaque sample collected from carotid endarterectomy of a 72-year old symptomatic patient (male) showing both old thrombus and plaque hemorrhage around neovessels: (A and D) Van Gieson's (EVG) and Hematoxylin and eosin (HE) stains showing elastin (black in EVG), collagen (pink in HE) and erythrocyte and its debris (brown in EVG and red in HE); (B and E) local views of 1 in (A) and 3 in (B) showing neovessels in a old thrombus resulted from previous rupture (marked by arrow in A and D); (C and F) local views of 2 in (A) and 4 in (B) showing erythrocytes (fresh plaque hemorrhage) around neovessels; red asterisk: arterial lumen; green asterisk: the lumen of neovessels. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Aggregation of macrophages around neovessels (A) hematoxylin and eosin (HE) stain showing neovessels within a fibrotic region; (B) CD68 stain showing the surrounding macrophages; green asterisks: lumens of neovessels. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

A large plaque hemorrhage depicted by MR imaging from a 72-year old asymptomatic patient (A) and (B) 3D-CUBE T₁-weighted MR image in coronal and transverse planes; (C) and (D) direct thrombus image (DTI) at the same location in (A) in coronal and transverse planes; red asterisk: arterial lumen. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)