1. Introduction
Carotid artery disease is the principal cause of ischemic stroke and the
benefit of carotid surgical revascularization in both symptomatic and
asymptomatic patients has been demonstrated by several trials [1-4].
Atherosclerotic plaque formation is associated with endothelial cells
damage, which leads to lipid accumulation, immigration of
monocyte-derived macrophages, release of growth factors and activation
of vascular smooth muscle cells (VSMC) [5]. Atherosclerotic plaque
rupture leads to local platelet activation and thrombosis that may
result in embolization and the onset of clinical symptoms [6].
Accumulating evidence confirm the key role of matrix metalloproteinase
(MMP) in plaque development and pathogenesis of atherosclerosis
[7-9]. MMP, among which is MMP-9, are enzymes that are produced by
infiltrating macrophages and VSMC and may have an important role in
plaque remodelling and destabilization by promoting the degradation of
extracellular matrix [8-10]. Increased serum levels of MMP-9 have
been detected in the coronary circulation among patients with acute
coronary syndrome, which suggested active process of plaque rupture and
increased risk of cardiovascular adverse events [11-13]. Similarly,
it was found that serum level of MMP-9 was significantly higher in
patients with carotid artery stenosis and unstable carotid plaques
undergoing carotid endarterectomy (CEA) [8, 14]. However,Baroncini et al. reported that MMP-9 is a part of atherogenesis
process but may not be a factor associated with acute disruption events
[15, 16].
Several non-invasive imaging techniques have been evaluated for the
characterization of the carotid plaque because carotid angiography is
able to detect plaque ulceration but is unable to demonstrate plaque
morphology [17]. Despite the fact that duplex ultrasound is the
first-line imaging modality, magnetic resonance imaging (MRI) has the
advantage to image the aortic arch with supra-aortic arteries as well as
to detect the presence of specific plaque features (vulnerable plaque,
intra-plaque haemorrhage, lipid-necrotic core) suggesting higher stroke
risk [18-22]. Recent reports suggested that preoperative MRI may be
useful in the detection of the vulnerable plaque and can help in
identifying patients with high risk of cardiovascular events [19,
20]. Increased MMP-9 expression in plaques with increased neovascular
changes along with MRI scan of carotid arteries was studied but this
analysis was performed in an animal study model.[23]
The aim of the present prospective pilot study is to analyse
histological characteristics and expression of MMP-9 in carotid plaques
of patients undergoing CEA and to investigate the correlation with
preoperative clinical symptoms and MR features.