Carotid Plaque Rupture Research Articles

Advanced glycation endproducts and plaque instability: a link beyond diabetes

This editorial refers to ‘Higher levels of advanced glycation endproducts in human carotid atherosclerotic plaques are associated with a rupture-prone phenotype’[†][1], by N.M.J. Hanssen et al. , on page 1137 Despite clear advances in the treatment of vascular disease, we are still far from the understanding and valid assessment of the natural history of atherosclerotic plaque. Several studies have shown that the vulnerable plaque is the main culprit for ischaemic cardiac and cerebral events, but reliable indicators of plaque instability remain elusive in clinical practice.1 This aspect deserves attention since rupture of carotid plaques explains at least 15–20% of all ischaemic strokes or transient ischaemic attacks.2 Over 15 million people per year suffer strokes worldwide, resulting in 5 million deaths, and an additional 5 million remain permanently disabled.2 Treatment of carotid artery stenosis by endoarterectomy or stenting can significantly reduce stroke risk, but it is also accompanied by surgery-related morbidity and mortality.1,2 Moreover, not all carotid artery plaques become symptomatic and result in ischaemic events. In this perspective, the identification of carotid plaques at high risk for neurological events is fundamental to the selection of patients for vascular interventions. Different processes involved in the progression of atherosclerotic lesions have been associated with plaque vulnerability.3 Previous seminal investigations have clearly shown that inflammation, proteolysis, and apoptosis are major drivers of plaque complexity and fragility.3 Pathological features of unstable plaques are represented by an atheromatous thin fibrous cap, large necrotic core, infiltration of inflammatory cells, and scarce calcification. Despite available imaging techniques providing an exhaustive macroscopic characterization of the plaque, the inner mechanisms involved remain to be largely elucidated and characterization of the molecular processes is achieved only at post-operative or post-mortem examination.1 The assessment of early markers of plaque vulnerability is an attractive … [1]: #fn-2

C: POSITRON EMISSION TOMOGRAPHY TO IDENTIFY RUPTURED AND VULNERABLE CORONARY PLAQUES

<h3>Background</h3> Non-invasive imaging to identify vulnerable or ruptured coronary artery plaque would represent a major clinical advance. Using positron emission tomography (PET) and computed tomography (CT), we investigated coronary uptake of 18F-fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) in patients with acute myocardial infarction or stable angina. <h3>Methods</h3> Forty patients with acute myocardial infarction and 40 with stable angina underwent electrocardiogram-gated 18F-NaF and 18F-FDG PET-CT and invasive coronary angiography. 18F-NaF uptake was compared with virtual histology intravascular ultrasound in patients with stable angina, and with histology in 12 carotid endartectomy specimens. <h3>Results</h3> Intense focal 18F-NaF uptake occurred at the site of plaque rupture in 37 (93%) patients with myocardial infarction (tissue-to-background ratio [TBR], 1.66 [1.40–2.25] versus 1.24 [1.06–1.38]; culprit versus maximal non-culprit, P&lt;0.001). In patients with stable angina, 18 (45%) had focal plaque 18F-NaF uptake (2.10 [1.71–2.81]) that, compared to plaques without uptake, had more high-risk features: positive remodeling (vessel area 24 [17–27] versus 14 [12–18] mm2; P=0.002), necrotic core (24.6% [20.5–28.8] verses 18.0% [14.0–22.4], P=0.001) and microcalcification (73 versus 21%, P=0.002). Carotid plaque rupture also co-localized with ex vivo 18F-NaF uptake and was associated with areas of apoptosis, necrosis and active calcification. Myocardial uptake markedly hampered 18F-FDG assessment in most patients (55%) and even where coronary uptake was discernible, there were no differences between culprit and non-culprit lesions (1.71 [1.40–2.13] versus 1.58 [1.28–2.01]; P=0.34). <h3>Conclusions</h3> 18F-NaF holds major promise as a novel biomarker of coronary plaque vulnerability and rupture with implications for the diagnosis, investigation and treatment of coronary artery disease.

Translational Application of Combining Magnetic Resonance Imaging and Biomechanical Analysis in Carotid Plaque Vulnerability Assessment

Stroke is the 3rd leading cause of death in the developed countries. It will rank the 2nd among the four leading causes of death globally by 2030 according to the World Health Organization. Carotid atherosclerotic disease is a predominant cause of stroke resulting from carotid plaque rupture. Degree of stenosis, which is the current criterion for assessment of atherosclerotic disease severity, has been observed to be insufficient. Atherosclerotic plaque is composed of various components, such as lipid-rich necrotic core, haemorrhage and calcium, covered by fibrous cap. Increasing evidence has shown that plaque vulnerability has a close relationship with these morphological features. Moreover, under physiological conditions plaque experiences mechanical loading due to blood pressure and blood flow. From the mechanical view point, rupture possibly occurs when the extra loading exceeds the material strength of the plaque. Therefore, anatomical and mechanical features should be considered in an integrated way for a more accurate assessment of plaque vulnerability. This review focuses on (1) the emerging high-risk morphological features and their association with clinical symptoms. Some related patents have been summarized; and (2) translational clinical application of biomechanical analysis in plaque vulnerability assessment. For completeness, the basis of atherosclerotic plaque, magnetic resonance imaging and finite element analysis will be introduced briefly.

Abstract 64: Mechanism Of Carotid Plaque Vulnerability: Associations Of Pro-and Anti-inflammatory Molecules

Background: Inflammation plays an important role in the development, progression, and rupture of carotid plaques. We examined the relationship between plaque vulnerability and inflammatory molecules using blood samples and histological specimens. Methods: We examined 58 patients with symptomatic or asymptomatic carotid stenosis, among which 41 underwent carotid artery stenting (CAS) and 17 underwent carotid endarterectomy (CEA). All of these patients were recruited in Mie University Hospital from Sept. 2009 to Mar. 2012 and underwent carotid plaque imaging with MRI. In the 41 patients with CAS, blood samples were obtained in the femoral artery as controls and in the carotid artery just before and after the operation. Emboli attached to the distal protection devices in CAS, or resected tissues after CEA were embedded in paraffin. The serum concentrations of IL-6, IL-10, E-selectin, adiponectin, hs-CRP and pentraxin 3 (PTX3) levels were measured by ELISA. Paraffin-embedded tissues were subjected to histopathologic and immunohistochemical analysis on IL-6, IL-10, E-selectin, PTX3. Results: The patients with CAS were classified to 22 with stable plaque (stable group) and 19 with vulnerable plaque (vulnerable group). The values of IL-6, E-selectin, hs-CRP and PTX3 in the vulnerable group were higher than those in the stable group, whereas adiponectin and IL-10 were decreased in the vulnerable group as compared to the stable group. The values of PTX3 in the control and intracarotid samples before and after CAS were higher from the vulnerable group than those from the stable group. Pathologically, IL-6 was immunostained in the vulnerable plaques with infiltration of inflammatory cells, and PTX3 was expressed in the endothelial and perivascular cells in the unstable plaques. Conclusions: The vulnerability of carotid plaques was modulated by upregulation of pro-inflammatory factors and downregulation of anti-inflammatory ones. In addition, PTX3 may be a novel determinant for plaque vulnerability.

Secreted proteins from carotid endarterectomy: an untargeted approach to disclose molecular clues of plaque progression

BackgroundAtherosclerosis is the main cause of morbidity and mortality in Western countries and carotid plaque rupture is associated to acute events and responsible of 15-20% of all ischemic strokes. Several proteomics approaches have been up to now used to elucidate the molecular mechanisms involved in plaque formation as well as to identify markers of pathology severity for early diagnosis or target of therapy. The aim of this study was to characterize the plaque secretome. The advantage of this approach is that secretome mimics the in vivo condition and implies a reduced complexity compared to the whole tissue proteomics allowing the detection of under-represented potential biomarkers.MethodsSecretomes from carotid endarterectomy specimens of 14 patients were analyzed by a liquid chromatography approach coupled with label free mass spectrometry. Differential expression of proteins released from plaques and from their downstream distal side segments were evaluated in each specimen. Results were validated by Western blot analysis and ELISA assays. Histology and immunohistochemistry were performed to characterize plaques and to localise the molecular factors highlighted by proteomics.ResultsA total of 463 proteins were identified and 31 proteins resulted differentially secreted from plaques and corresponding downstream segments. A clear-cut distinction in the distribution of cellular- and extracellular-derived proteins, evidently related to the higher cellularity of distal side segments, was observed along the longitudinal axis of carotid endarterectomy samples. The expressions of thrombospondin-1, vitamin D binding protein, and vinculin, as examples of extracellular and intracellular proteins, were immunohistologically compared between adjacent segments and validated by antibody assays. ELISA assays of plasma samples from 34 patients and 10 healthy volunteers confirmed a significantly higher concentration of thrombospondin-1 and vitamin D binding protein in atherosclerotic subjects.ConclusionsTaking advantage of the optimized workflow, a detailed protein profile related to carotid plaque secretome has been produced which may assist and improve biomarker discovery of molecular factors in blood. Distinctive signatures of proteins secreted by adjacent segments of carotid plaques were evidenced and they may help discriminating markers of plaque complication from those of plaque growth.

Treatment with Evasin-3 Reduces Atherosclerotic Vulnerability for Ischemic Stroke, but Not Brain Injury in Mice

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactivity and related neutrophilic inflammation in two mouse models of carotid atherosclerosis and ischemic stroke, respectively. In the first model, the chronic treatment with Evasin-3 as compared with Vehicle (phosphate-buffered saline (PBS)) was investigated in apolipoprotein E-deficient mice implanted of a 'cast' carotid device. In the second model, acute Evasin-3 treatment (5 minutes after cerebral ischemia onset) was assessed in mice subjected to transient left middle cerebral artery occlusion. Although CXCL1 and CXCL2 were upregulated in both atherosclerotic plaques and infarcted brain, only CXCL1 was detectable in serum. In carotid atherosclerosis, treatment with Evasin-3 was associated with reduction in intraplaque neutrophil and matrix metalloproteinase-9 content and weak increase in collagen as compared with Vehicle. In ischemic stroke, treatment with Evasin-3 was associated with reduction in ischemic brain neutrophil infiltration and protective oxidants. No other effects in clinical and histological outcomes were observed. We concluded that Evasin-3 treatment was associated with reduction in neutrophilic inflammation in both mouse models. However, Evasin-3 administration after cerebral ischemia onset failed to improve poststroke outcomes.

Ligation of Macrophage Fcγ Receptors Recapitulates the Gene Expression Pattern of Vulnerable Human Carotid Plaques

Stroke is a leading cause of death in the United States. As ∼60% of strokes result from carotid plaque rupture, elucidating the mechanisms that underlie vulnerability is critical for therapeutic intervention. We tested the hypothesis that stable and vulnerable human plaques differentially express genes associated with matrix degradation. Examination established that femoral, and the distal region of carotid, plaques were histologically stable while the proximal carotid plaque regions were vulnerable. Quantitative RT-PCR was used to compare expression of 22 genes among these tissues. Distal carotid and femoral gene expression was not significantly different, permitting the distal carotid segments to be used as a paired control for their corresponding proximal regions. Analysis of the paired plaques revealed differences in 16 genes that impact plaque stability: matrix metalloproteinases (MMP, higher in vulnerable), MMP modulators (inhibitors: lower, activators: higher in vulnerable), activating Fc receptors (FcγR, higher in vulnerable) and FcγR signaling molecules (higher in vulnerable). Surprisingly, the relative expression of smooth muscle cell and macrophage markers in the three plaque types was not significantly different, suggesting that macrophage distribution and/or activation state correlates with (in)stability. Immunohistochemistry revealed that macrophages and smooth muscle cells localize to distinct and non-overlapping regions in all plaques. MMP protein localized to macrophage-rich regions. In vitro, treatment of macrophages with immune complexes, but not oxidized low density lipoprotein, C-reactive protein, or TNF-α, induced a gene expression profile similar to that of the vulnerable plaques. That ligation of FcγR recapitulates the pattern of gene expression in vulnerable plaques suggests that the FcγR → macrophage activation pathway may play a greater role in human plaque vulnerability than previously appreciated.

Asymptomatic carotid plaque rupture with unexpected thrombosis over a non-canonical vulnerable lesion

ObjectiveSeveral studies have demonstrated that carotid plaque rupture and thrombosis represent the most important factors correlated with the onset of acute cerebrovascular symptoms. Nevertheless, ruptured thrombotic plaques have been described also in asymptomatic patients. What still needs to be clarified is why a plaque rupture leads either to an acute ischemic syndrome or, in a minor group of patients, remains asymptomatic. The purpose of this study was to systematically compare the histologic features of thrombotic plaques both in asymptomatic and symptomatic patients in order to identify specific findings that could explain the peculiar clinical behavior that characterizes each of the clinical settings. MethodsA total of 157 thrombotic plaques from 60 asymptomatic patients and 97 with major stroke who consecutively underwent CEA were serially sectioned and studied by histology. ResultsA minute cap disruption very frequently characterizes thrombotic plaques of asymptomatic patients and it was always smaller than large ulcers observed in thrombotic symptomatic plaques (651±687μm vs. 4150±3526, p=0.001). In asymptomatics this typical feature was associated with fewer inflammatory cells (20.1±8.8 vs. 33.9±26.1cells×hpf, p=0.001), smaller lipidic–necrotic core (33.9%±2.9% vs. 42.0%±2.4%; p=0.04) and larger calcification (16.2±12.8% vs. 8.1±12.2%, p=0.02). Symptomatic patients with thrombotic plaques showed higher incidence of metabolic syndrome (p=0.002) and moderate-high Framingham risk scores (p=0.001) comparing to asymptomatic individuals. ConclusionThe transformation from a stable to a vulnerable plaque is a gradual process in the natural history of the disease and plaque rupture is an event not necessarily occurring at a late phase but also at earlier one. In this case, the rupture will be most likely smaller and clinically asymptomatic.

In Vivo Serial MRI-Based Models and Statistical Methods to Quantify Sensitivity and Specificity of Mechanical Predictors for Carotid Plaque Rupture: Location and Beyond

It has been hypothesized that mechanical risk factors may be used to predict future atherosclerotic plaque rupture. Truly predictive methods for plaque rupture and methods to identify the best predictor(s) from all the candidates are lacking in the literature. A novel combination of computational and statistical models based on serial magnetic resonance imaging (MRI) was introduced to quantify sensitivity and specificity of mechanical predictors to identify the best candidate for plaque rupture site prediction. Serial in vivo MRI data of carotid plaque from one patient was acquired with follow-up scan showing ulceration. 3D computational fluid-structure interaction (FSI) models using both baseline and follow-up data were constructed and plaque wall stress (PWS) and strain (PWSn) and flow maximum shear stress (FSS) were extracted from all 600 matched nodal points (100 points per matched slice, baseline matching follow-up) on the lumen surface for analysis. Each of the 600 points was marked "ulcer" or "nonulcer" using follow-up scan. Predictive statistical models for each of the seven combinations of PWS, PWSn, and FSS were trained using the follow-up data and applied to the baseline data to assess their sensitivity and specificity using the 600 data points for ulcer predictions. Sensitivity of prediction is defined as the proportion of the true positive outcomes that are predicted to be positive. Specificity of prediction is defined as the proportion of the true negative outcomes that are correctly predicted to be negative. Using probability 0.3 as a threshold to infer ulcer occurrence at the prediction stage, the combination of PWS and PWSn provided the best predictive accuracy with (sensitivity, specificity) = (0.97, 0.958). Sensitivity and specificity given by PWS, PWSn, and FSS individually were (0.788, 0.968), (0.515, 0.968), and (0.758, 0.928), respectively. The proposed computational-statistical process provides a novel method and a framework to assess the sensitivity and specificity of various risk indicators and offers the potential to identify the optimized predictor for plaque rupture using serial MRI with follow-up scan showing ulceration as the gold standard for method validation. While serial MRI data with actual rupture are hard to acquire, this single-case study suggests that combination of multiple predictors may provide potential improvement to existing plaque assessment schemes. With large-scale patient studies, this predictive modeling process may provide more solid ground for rupture predictor selection strategies and methods for image-based plaque vulnerability assessment.

Characterization of healing following atherosclerotic carotid plaque rupture in acutely symptomatic patients: an exploratory study using in vivo cardiovascular magnetic resonance.

BackgroundCarotid plaque rupture, characterized by ruptured fibrous cap (FC), is associated with subsequent cerebrovascular events. However, ruptured FC may heal following stroke and convey decreased risk of future events. This study aims to characterize the healing process of ruptured FC by assessing the lumen conditions, quantified by the lumen curvature and roughness, using in vivo carotid cardiovascular magnetic resonance (CMR).MethodsPatients suffering from transient ischemic attack underwent high resolution carotid MR imaging within 72 hours of the acute cerebrovascular ischemic event. CMR imaging was repeated at 3 and 12 months in 26 patients, in whom FC rupture/erosion was observed on baseline images and subsequent cerebrovascular events were recorded during the follow-up period. Lumen curvature and roughness were quantified from carotid CMR images and changes in these values were monitored on follow-up imaging.ResultsHealing of ruptured plaque was observed in patients (23 out of 26) without any ischemic symptom recurrence as shown by the lumen surface becoming smoother during the follow-up period, characterized by decreasing maximum lumen curvature (p < 0.05), increasing minimum lumen curvature (p < 0.05) and decreasing lumen roughness (p < 0.05) during the one year follow-up period.ConclusionsCarotid plaque healing can be assessed by quantification of the lumen curvature and roughness and the incidence of recurrent cerebrovascular events may be high in plaques that do not heal with time. The assessment of plaque healing may facilitate risk stratification of recent stroke patients on the basis of CMR results.

Evolution of Atherosclerotic Carotid Plaque Morphology: Do Ulcerated Plaques Heal? A Serial Multidetector CT Angiography Study

Background: Atherosclerotic carotid plaque rupture may lead to thromboembolization, causing transient ischemic attack or ischemic stroke. Carotid plaque ulceration on angiography is associated with plaque rupture. Although healing of ruptured plaques has been described in coronary arteries, little is known about the natural development of plaque ulcerations in carotid arteries. We therefore explored the evolution of carotid plaque surface morphology with serial multidetector CT angiography (MDCTA). Methods: From a registry of patients with transient ischemic attack or minor ischemic stroke, we selected 83 patients who had undergone serial MDCTA of the carotid arteries. Arteries subjected to revascularization procedures between the two scans were excluded (n = 11). Plaque surface morphology was classified as smooth, irregular or ulcerated on both baseline and follow-up MDCTA. Progression (i.e. development of irregularities or ulceration) and regression (i.e. disappearance of irregularities or ulceration) in morphology were evaluated. Results: The mean time interval between the MDCTA scans was 21 ± 13 months. At baseline, 28 (18%) arteries were normal, 124 (80%) contained atherosclerotic plaque and 3 (2%) were occluded. Plaque surface morphology was smooth in 86 arteries (55%), irregular in 23 (15%) and ulcerated in 15 (10%). At follow-up, surface morphology was unchanged in 88% of arteries, had progressed in 8% and regressed in 4%. Most importantly, plaque morphology remained unchanged in most ulcerated plaques (10/15; 67%). One ulcerated plaque had progressed, whereas 4 had regressed. New ulcerations had developed in 2 nonulcerated plaques. Conclusion: MDCTA allows evaluation of temporal changes in atherosclerotic carotid plaque morphology. Plaque surface morphology remained unchanged in most arteries. Carotid ulcerations persist for a long time, and may remain a potential source of thromboembolism.

Magnetic Resonance Imaging of Carotid Atherosclerotic Plaque in Clinically Suspected Acute Transient Ischemic Attack and Acute Ischemic Stroke

Carotid atherosclerotic plaque rupture is thought to cause transient ischemic attack (TIA) and ischemic stroke (IS). Pathological hallmarks of these plaques have been identified through observational studies. Although generally accepted, the relationship between cerebral thromboembolism and in situ atherosclerotic plaque morphology has never been directly observed noninvasively in the acute setting. Consecutive acutely symptomatic patients referred for stroke protocol magnetic resonance imaging/angiography underwent additional T1- and T2-weighted carotid bifurcation imaging with the use of a 3-dimensional technique with blood signal suppression. Two blinded reviewers performed plaque gradings according to the American Heart Association classification system. Discharge outcomes and brain magnetic resonance imaging results were obtained. Image quality for plaque characterization was adequate in 86 of 106 patients (81%). Eight TIA/IS patients with noncarotid pathogenesis were excluded, yielding 78 study patients (38 men and 40 women with a mean age of 64.3 years, SD 14.7) with 156 paired watershed vessel/cerebral hemisphere observations. Thirty-seven patients had 40 TIA/IS events. There was a significant association between type VI plaque (demonstrating cap rupture, hemorrhage, and/or thrombosis) and ipsilateral TIA/IS (P<0.001). A multiple logistic regression model including standard Framingham risk factors and type VI plaque was constructed. Type VI plaque was the dominant outcome-associated observation achieving significance (P<0.0001; odds ratio, 11.66; 95% confidence interval, 5.31 to 25.60). In situ type VI carotid bifurcation region plaque identified by magnetic resonance imaging is associated with ipsilateral acute TIA/IS as an independent identifier of events, thereby supporting the dominant disease pathophysiology.

The Role of Infection in Carotid Plaque Pathogenesis and Stability: The Clinical Evidence

Chlamydia pneumoniae was the first pathogen linked with carotid atherosclerotic changes and plaque rupture. Currently, other common pathogens are also under investigation as potential contributors. A systematic review of PubMed and Scopus databases was performed. Studies evaluating the infectious burden between symptomatic and asymptomatic patients with carotid plaque disease (CPD) were included. Furthermore, trials referring to common infectious agents (other than C. pneumoniae) incriminated for contribution in CPD were analyzed separately. Forty four studies were identified; 6 investigated the connection of infection with the plaque destabilization, 3 of which reported a significant association between infection and symptoms. Studies retrieved for the investigation of agents other than C. pneumoniae were: 18 about viruses, 16 about other bacteria and 4 examining both. Significant association or high detection rates of agents' genome or specific antibodies with CPD characteristics (intima media thickness values > 1 mm or symptoms) were found in a number of studies: 3 for HCV, 2 for CMV and 1 for enterovirus, EBV, HBV, and HIV. Moreover 4 studies about dental pathogens (i.e. Porpyromonas gingivalis), 5 about H. Pylori strains and 1 about Borrelia burgdorferi were identified supporting a positive association. There is considerable evidence supporting the contribution of other commonly encountered pathogens in the pathogenesis and rupture of the carotid plaque. Research in this direction should not be abandoned and further studies are necessary to elucidate the exact role of common infections in the pathogenesis and development of CPD and how this can be translated into novel pharmacological approaches for prevention and treatment.

Introduction to the biomechanics of carotid plaque pathogenesis and rupture: review of the clinical evidence.

The management of patients with asymptomatic carotid disease is currently under debate and new methods are warranted for better risk stratification. The role of the biomechanical properties of the atherosclerotic arterial wall together with the effect of different stress types in plaque destabilisation has only been recently investigated. PubMed and Scopus databases were reviewed. There is preliminary clinical evidence demonstrating that the analysis of the combined effect of the various types of biomechanical stress acting on the carotid plaque may help us to identify the vulnerable plaque. At present, MRI and two-dimensional ultrasound are combined with fluid-structure interaction techniques to produce maps of the stress variation within the carotid wall, with increased cost and complexity. Stress wall analysis can be a useful tool for carotid plaque evaluation; however, further research and a multidisciplinary approach are deemed as necessary for further development in this direction.

Combined imaging, computational and histological analysis of a ruptured carotid plaque: A patient-specific analysis

Background Rupture of carotid plaques is an important cause of cerebrovascular events. Several factors, including wall shear stress (WSS), plaque morphology and peak cap stress, have been associated with plaque vulnerability. The aim of this study was to investigate the relationship between these factors in an in vivo human ruptured carotid plaque. Methods A 74-year-old male presenting with a transient ischemic attack underwent carotid magnetic resonance imaging (MRI), which indicated a ruptured plaque, followed by carotid endarterectomy, from which plaque histology was assessed. The carotid bifurcation was reconstructed from the MRI data, and three-dimensional flow simulations were performed using computational fluid dynamics to determine WSS and related parameters. Plaque vulnerability was assessed using a biomechanical method based on modified Glagov criteria. Results The plaque rupture was just distal to the site of maximum stenosis in a region of low WSS, where MRI and histology both demonstrated fibrous cap thinning, a large lipid pool and calcification in the shoulder region. Plaque vulnerability analysis indicated critically vulnerable plaque at the rupture site by a wide margin. Conclusions Both low and high WSS have been associated with plaque vulnerability, and high mechanical stress in the cap has been linked to plaque rupture, but these parameters are not routinely assessed clinically. This study demonstrates a complete analysis by combining imaging, histology and bio-fluid and biomechanical modelling.

P53 expression in human carotid atheroma is significantly related to plaque instability and clinical manifestations

ObjectiveThe expression of p53 has been associated with DNA damage, cell senescence, proliferation and apoptosis in human atherosclerotic plaques. However, it is largely unknown whether p53 expression is related to the stability and clinical manifestations of atherosclerotic plaques in humans. In the present study, we examined whether p53 expression is related to clinical symptoms and plaque integrity in patients with carotid atherosclerosis (n=62). We also investigated p53 expression and its relation to apoptosis and apoptosis-related cathepsin L and ferritin in the carotid lesions. Methods and resultsWe found that smooth muscle cells often had nuclear p53 in the shoulder region of carotid lesions while CD68-positive macrophages, which had both nuclear and cytoplasmic p53, frequently appeared in the surrounding areas of necrotic cores or plaque cap regions. Quantitative image analysis of immunohistochemistry showed that p53 expression was significantly increased in plaques with necrotic core formation or cap rupture and lesions from patients with transient ischemic attacks (TIAs). The levels of p53 expression was significantly increased in more severe stenosed lesions but decreased with prolonged time between symptom onset and carotid endarterectomy. Furthermore, p53 expression was significantly correlated with the expression of ferritin, lysosomal cathepsin L, and apoptosis. ConclusionThe increased p53 expression, particularly macrophage p53 levels, is associated with the enlargement of necrotic cores, plaque rupture and clinical manifestations of carotid plaques. Concomitant increases of lysosomal cathepsin, ferritin, and p53 levels may promote the apoptosis and atheroma progression in patients with carotid atherosclerosis.

Carotid plaque rupture

A 74-year-old man presented with left-sided monocular visual loss as a result of branch retinal artery occlusion. Carotid ultrasonography showed mild (20%) left carotid artery stenosis but no embolic source was identifi ed. MRI of the carotid artery showed a large atherosclerotic plaque at the origin of the left internal carotid artery, despite only mild luminal stenosis (fi gure A). Cross-sectional imaging (B-T1 weighted, C-T2 weighted), showed a thin fi brous cap with rupture and a large lipid core (fi gure A, B, and C). Carotid endarterectomy was done. In the pathological specimen, a large lipid laden plaque was present (fi gure D) showing evidence of plaque rupture and adherent thrombus. Carotid endarterectomy is usually considered only for carotid stenosis between 70% and 99%. This case demonstrates that this approach is simplistic and that plaque structure and vulnerability should also be considered.

A pathobiologic link between risk factors profile and morphological markers of carotid instability

ObjectiveAlthough cardiovascular risk factors have been strongly linked to carotid intimal-media thickness, their association with plaque progression towards instability is poorly understood.We evaluated a large database of endarterectomy specimens removed from symptomatic and asymptomatic patients to determine the correlation between major cardiovascular risk factors and carotid plaque morphology. MethodsIncidence of thrombotic, vulnerable and stable plaques together with the degree of plaque inflammatory infiltration was evaluated in 457 carotid atherosclerotic lesions. Clinical records were reviewed in all cases for risk factors profile. ResultsThrombotic plaques were more frequently observed in patients affected by stroke (66.9%) as compared to TIA (36.1%) and asymptomatic patients (26.8%, p<0.001). Out of 457 carotid plaques removed during carotid endarterectomy, 181 (39.6%) were represented by thrombotic plaques, 72 (15.8%) by vulnerable plaques (thin cap fibroateroma) and 204 (44.6%) by stable plaques. At the multivariate analysis, a strong association was observed between hypertension, low HDL-cholesterol (HDL-C) and ratio of total to HDL-C >5 with vulnerable and thrombotic carotid plaques. Hypertension (p=0.001), hypercholesterolemia (p=0.05) and low HDL-C (p=0.001) significantly also correlated with the presence of high inflammatory infiltrate of the plaque. When multivariate analysis was restricted to asymptomatic patients, hypertension (p=0.009, OR 2.29), low HDL-cholesterol (p=0.01 OR 2.21) and the ratio of total to HDL-C >5 (p=0.03, OR 2.07) were confirmed to be the risk factors most significantly associated to unstable plaques. The relative risk to carry an unstable plaque for asymptomatic patients with high Framingham Risk Score as compared with those with low risk score was 2.06 (95% C.I., 1.26–3.36). ConclusionsThe present histopathological study identifies risk factors predictive of increased risk of carotid plaque rupture and thrombosis. Asymptomatic patients with high risk factors profile may constitute a specific target to reduce the likelihood of cerebrovascular accidents even in the presence of non-flow-limiting plaque.

Computational fluid dynamics

Computational fluid dynamics

Noninvasive vascular ultrasound elastography of carotid arteries for stroke prevention

Carotid plaque rupture leading to stroke involves alteration of arterial wall mechanical properties. This paper addresses reproducibility and potential clinical impact of non‐invasive vascular elastography. Fifteen symptomatic and 15 asymptomatic patients with greater than 50% stenoses of their internal carotids, and 15 control subjects were scanned independently by two radiologists. Radio‐frequency cine‐loops were acquired on left and right common and proximal internal carotids. For control subjects, homogeneous strains with successive compression and dilatation of the vascular wall from systole to diastole and few shear patterns were observed. The axial strain did not differ between recording sites, sides and radiologists (ANOVA, p > 0.19). For patients, heterogeneous axial strain patterns with both compression and dilatation of tissues within plaques were noted along with shear concentrations at interfaces of tissue structures. Despite similar blood pressures, larger mean instantaneous axial strains were measured in symptomatic (1.5 ± 0.6%) versus asymptomatic (1.2 ± 0.5%) patients in systole for common carotids (t‐test, p < 0.02). To conclude, reproducible results were obtained for control subjects and in patients, larger axial strains in common carotids may be associated with plaque rupture. This new imaging method may become a unique approach to characterize vulnerable plaques for stroke prevention.