Luís Mendes Pedro

Changes Related to Age and Cerebrovascular Symptoms in the Extracellular Matrix of Human Carotid Plaques

Background and Purpose— Many processes involved in the pathogenesis of atherosclerosis result in modifications of the extracellular matrix. These changes not only determine the mechanical stability of atherosclerotic lesions but can directly or indirectly influence further development of the lesions. The purpose of the present study was to compare the matrix composition of human carotid plaques from symptomatic patients with those obtained from patients without symptoms. Furthermore, matrix changes related to age were studied. Methods— Thirty atherosclerotic carotid plaques were removed by endarterectomy from 27 patients and divided into 2 groups on the basis of the presence of ipsilateral symptoms. The plaques were homogenized, and the total levels of the major components of the extracellular matrix were determined. Results— Plaques associated with symptoms were characterized by increased levels of elastin (1.58±0.46 versus 1.24±0.40 mg/g wet wt;P =0.03) and decreased levels of hydroxyapatite (45.1±46.3 versus 131.4±111.7 mg/g wet wt;P =0.02) compared with asymptomatic plaques. The increase in elastin in plaques from symptomatic patients was due to elevated levels of an intermediate-size fraction, as determined by liquid chromatography. Collagen and sulfated glycosaminoglycans were present in equal amounts in both groups. Elastin content in carotid plaques decreased with age. Conclusions— Carotid plaques from symptomatic patients have lower levels of hydroxyapatite than those from asymptomatic patients. The present study also raises the possibility that non–cross-linked forms of elastin, increased in plaques associated with symptoms, could be a marker of plaque vulnerability and/or directly induce harmful cellular activities or increase lipoprotein retention in the vascular wall.

Elastin and Calcium Rather Than Collagen or Lipid Content Are Associated With Echogenicity of Human Carotid Plaques

Background and Purpose— Echolucent carotid plaques have been associated with increased risk for stroke. Histological studies suggested that echolucent plaques are hemorrhage- and lipid-rich, whereas echogenic plaques are characterized by fibrosis and calcification. This is the first study to relate echogenicity to plaque composition analyzed biochemically. Methods— Echogenicity of human carotid plaques was analyzed by standardized high-definition ultrasound and classified into echolucent, with gray-scale median (GSM) <32 and echogenic with GSM ≥32. The biochemical composition of the plaques was assessed by fast-performance liquid chromotography and high-performance thin-layer chromotography. Results— As assessed biochemically (milligrams per gram [mg/g]), echolucent plaques contained less hydroxyapatite (43.8 [SD 41.2] mg/g versus 121.6 [SD 106.2] mg/g; P=0.018), more total elastin (1.7 [SD 0.4] mg/g versus 1.2 [SD 0.4] mg/g; P=0.008), and more intermediate-size elastin forms (1.2 [SD 0.3] mg/g versus 0.8 [SD 0.4] mg/g; P=0.018). There was no difference in collagen amount between echogenic and echolucent plaques, neither biochemically (15.3 [SD 3.7] mg/g versus 14.4 [SD 3.4] mg/g) nor histologically (13.4 [SD 4.9] % versus 13.0 [SD 5.6] %). Cholesterol esters, unesterified cholesterol, and triglycerides were increased in plaques associated with symptoms (22.5 [SD 23.3] mg/g versus 13.3 [SD 3.2]; P=0.04), but no differences were detected between echolucent and echogenic plaques (13.5 [SD 4.0] versus 20.2 [SD 21.5] mg/g). Similar results were obtained by Oil Red O staining (symptomatic 7.6 [SD 4.7] % versus asymptomatic 4.2 [SD 3.6] %; P=0.03; echolucent 5.9 [SD 4.1] % versus echogenic 5.0 [SD 4.0] % of area). Conclusions— Echogenicity of carotid plaques is mainly determined by their elastin and calcium but not collagen or lipid content. In addition, echolucency is associated to higher elastin content.

A 3-D Ultrasound-Based Framework to Characterize the Echo Morphology of Carotid Plaques

Carotid atherosclerosis is the main cause of brain stroke, which is the most common life-threatening neurological disease. Nearly all methods aiming at assessing the risk of plaque rupture are based on its characterization from 2-D ultrasound images, which depends on plaque geometry, degree of stenosis, and echo morphology (intensity and texture). The computation of these indicators is, however, usually affected by inaccuracy and subjectivity associated with data acquisition and operator-dependent image selection. To circumvent these limitations, a novel and simple method based on 3-D freehand ultrasound is proposed that does not require any expensive equipment except the common scanner. This method comprises the 3-D reconstruction of carotids and plaques to provide clinically meaningful parameters not available in 2-D ultrasound imaging, namely diagnostic views not usually accessible via conventional techniques and local 3-D characterization of plaque echo morphology. The labeling procedure, based on graph cuts, allows us to identify, locate, and quantify potentially vulnerable foci within the plaque. Validation of the characterization method was made with synthetic data. Results of plaque characterization with real data are encouraging and consistent with the results from conventional methods and after inspection of surgically removed plaques.

Hemorheological parameters are related to subclinical atherosclerosis in systemic lupus erythematosus and rheumatoid arthritis patients

OBJECTIVES Rheological characteristics of blood are strongly linked to atherothrombosis in the general population, but its contribution to atherosclerosis in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) is currently unclear. This work examines the relationship between blood rheology, traditional cardiovascular (CV) risk factors, inflammation and subclinical atherosclerosis in SLE and RA. METHODS Whole blood viscosity (WBV), plasma viscosity (PV), erythrocyte deformability (ED), aggregation (EA) and erythrocyte NO production were measured in 197 patients (96 SLE and 101 RA) and compared to 97 controls, all females without previous CV events. Clinical information was obtained and fasting lipids and acute phase reactants were measured. The relationship between hemorheological parameters, CV risk factors and inflammation was assessed in patients and the impact of these variables on carotid intima-media thickness (cIMT) was evaluated in univariate followed by multivariate regression analyses. RESULTS WBV and ED are significantly lower in patients, while EA is elevated as compared with controls. Hemorheological disturbances correlate with CV risk factors and markers of inflammation and are more profound in patients with metabolic syndrome. Multivariable analysis showed that menopause (OR 34.72, 95%CI 4.44-271.77), obesity (OR 4.09, 95%CI 1.00-16.68) and WBV (OR 3.98; 95%CI 1.23-12.83) are positively associated whereas current corticosteroid dose (OR 0.87; 95%CI 0.78-0.98), and erythrocyte NO production (OR 0.16; 95%CI 0.05-0.52) are negatively associated with cIMT. CONCLUSION Disturbed hemorheological parameters in SLE and RA women are related to the presence of CV risk factors and inflammation. WBV and erythrocyte NO are independently associated with the early stages of atherosclerosis.

Plaque Tissue Characterization and Classification in Ultrasound Carotid Scans: A Paradigm for Vascular Feature Amalgamation

The selection of carotid atherosclerosis patients for surgery or stenting is a crucial task in atherosclerosis disease management. In order to select only those symptomatic cases who need surgery, we have, in this work, presented a computer-aided diagnostic technique to effectively classify symptomatic and asymptomatic plaques from B-mode ultrasound carotid images. We extracted several grayscale features that quantify the textural differences inherent in the manually delineated plaque regions and selected the most significant among these extracted features. These features, along with the degree of stenosis (DoS), were used to train and test a support vector machine (SVM) classifier using threefold stratified cross-validation using a data set consisting of 160 (50 symptomatic and 110 asymptomatic) images. Using 32 features in an SVM classifier with a polynomial kernel of order 1, we obtained the best accuracy of 90.66%, sensitivity of 83.33%, and specificity of 95.39%. The DoS was found to be a valuable feature in addition to other texture-based features. We have also proposed the plaque risk index (PRI) made up of a combination of significant features such that the PRI has unique ranges for both plaque classes. PRI can be used in monitoring the variations in features over a period of time which will provide evidence on how and which features change as asymptomatic plaques become symptomatic.

Multi-Modality Atherosclerosis Imaging and Diagnosis

Stroke is one of the leading causes of death in the world, resulting mostly from the sudden ruptures of atherosclerosis carotid plaques. Understanding why and how plaque develops and ruptures requires a multi-disciplinary approach such as radiology, biomedical engineering, medical physics, software engineering, hardware engineering, pathological and histological imaging. Multi-Modality Atherosclerosis Imaging, Diagnosis and Treatment presents a new dimension of understanding Atherosclerosis in 2D and 3D. This book presents work on plaque stress analysis in order to provide a general framework of computational modeling with atherosclerosis plaques. New algorithms based on 3D and 4D Ultrasound are presented to assess the atherosclerotic disease as well as very recent advances in plaque multimodality image fusion analysis.The goal of Multi-Modality Atherosclerosis Imaging, Diagnosis and Treatment is to fuse information obtained from different 3D medical image modalities, such as 3D US, CT and MRI, providing the medical doctor with some sort of augmented reality information about the atherosclerotic plaque in order to improve the accuracy of the diagnosis. Analysis of the plaque dynamics along the cardiac cycle is also a valuable indicator for plaque instability assessment and therefore for risk stratification. 4D Ultrasound, a sequence of 3D reconstructions of the region of interest along the time, can be used for this dynamic analysis. Multimodality Image Fusion is a very appealing approach because it puts together the best characteristics of each modality, such as, the high temporal resolution of US and the high spatial resolutions of MRI and CT.

Activation of calpain-1 in human carotid artery atherosclerotic lesions

BackgroundIn a previous study, we observed that oxidized low-density lipoprotein-induced death of endothelial cells was calpain-1-dependent. The purpose of the present paper was to study the possible activation of calpain in human carotid plaques, and to compare calpain activity in the plaques from symptomatic patients with those obtained from patients without symptoms.MethodsHuman atherosclerotic carotid plaques (n = 29, 12 associated with symptoms) were removed by endarterectomy. Calpain activity and apoptosis were detected by performing immunohistochemical analysis and TUNEL assay on human carotid plaque sections. An antibody specific for calpain-proteolyzed α-fodrin was used on western blots.ResultsWe found that calpain was activated in all the plaques and calpain activity colocalized with apoptotic cell death. Our observation of autoproteolytic cleavage of the 80 kDa subunit of calpain-1 provided further evidence for enzyme activity in the plaque samples. When calpain activity was quantified, we found that plaques from symptomatic patients displayed significantly lower calpain activity compared with asymptomatic plaques.ConclusionThese novel results suggest that calpain-1 is commonly active in carotid artery atherosclerotic plaques, and that calpain activity is colocalized with cell death and inversely associated with symptoms.

Physical activity and cardiorespiratory fitness, but not sedentary behavior, are associated with carotid intima-media thickness in obese adolescents

AbstractThis study aimed to analyze the associations between sedentary behavior, physical activity (PA), and cardiorespiratory fitness (CRF), with carotid intima-media thickness (cIMT), a marker of atherosclerosis already present at an early stage among obese adolescents. The associations between anthropometric measures, sedentary time, PA, CRF, and cIMT of 54 Caucasian obese adolescents were analyzed using partial correlations (controlling for age and sex) and multiple linear regressions. Differences between participants with and without a healthy CRF were also analyzed using independent sample t test. Sedentary time did not correlate with any of the variables. Light physical activity correlated positively with mean cIMT (r(38) = 0.36, p = 0.024). Moderate physical activity (MPA) correlated positively with both mean (r(38) = 0.37, p = 0.018) and maximum (r(38) = 0.33, p = 0.039) cIMT. CRF was inversely associated with mean cIMT (r(40) = −0.36, p = 0.019), even when controlling for sedentary time (r(37) = −0.35, p = 0.030). The best predictors of cIMT were MPA and weight. No significant differences in cIMT were found between participants with healthy and unhealthy CRF. Conclusion: Although we need to be cautious due to the limitations of the study, the results suggest that despite the importance of decreasing sedentary time, increasing PA intensity may be more effective in improving endothelial structural health among obese adolescents.What is Known:• Pediatric obesity is associated with increased carotid intima-media thickness (cIMT).• Physical activity may have a relevant role in cIMT development.What is New:• Cardiorespiratory fitness (CRF) may be a key moderator of this process.• Inherited CRF may be protective against cIMT development in obese adolescents.

Ultrasonographic characterization and identification of symptomatic carotid plaques

Carotid plaques are the main cause of neurological symptoms due to distal embolization or flow reduction. An objective classification of such lesions into symptomatic or asymptomatic is crucial for optimal treatment planning.

Carotid Plaque 3D Compound Imaging and Echo-Morphology Analysis: a Bayesian Approach

This paper describes a method for volume reconstruction of the carotid plaque and presents a novel local characterization of its echo-morphology. The data is composed by a series of nearly parallel ultrasound images (3D Compound Imaging) and the acquisition is performed using traditional noninvasive ultrasound equipment available in most medical facilities, without need of a spatial locator device. The reconstruction algorithm uses the observed pixels inside the plaque, which were obtained in a pre-segmentation stage performed under medical guidance [1]. The paper proposes a Bayesian algorithm which estimates the underlying volume inside the plaque, by filtering and interpolating the data in order to remove speckle noise and fill non- observed regions, respectively. This volume is further used in plaque echo-morphology analysis. The observation model is based on the Rayleigh distribution, commonly used to model speckle noise in ultrasound images. A prior model based on the edge preserving Total Variation Gibbs distribution is also used to fill the gaps on non-evenly spaced observations. An energy function is derived from these models and an iterative algorithm computes its minimizer. The estimated function, defined in a given volume of interest, is used in global and local plaque characterization, namely to estimate its average levels of stenosis, echo-morphology and to identify vulnerable foci inside the plaque. The goal is to make atherosclerosis diagnosis more accurate and complete than using traditional 2D ultrasound analysis.