Genetic determinants of carotid ultrasound traits

Assessment of atherosclerosis: should coronary calcium score and intima-media thickness be replaced by ultrasound measurement of carotid plaque burden and vessel wall volume?

PURPOSE OF REVIEW

To describe the uses of vessel wall volume (VWV) and measurement of carotid plaque burden, as total plaque area (TPA) and total plaque volume (TPV), and to contrast them with measurement of carotid intima-media thickness (IMT) and coronary calcium (CAC).

RECENT FINDINGS

Measurement of carotid plaque burden (CPB) is useful for risk stratification, research into the genetics and biology of atherosclerosis, for measuring effects of new therapies for atherosclerosis, and for treatment of high-risk patients with severe atherosclerosis. It is as predictive of risk as CAC, with important advantages. IMT is only a weak predictor of risk and changes so little over time that it is not useful for assessing effects of therapy.

SUMMARY

Measurement of CPB and VWV are far superior to measurement of carotid IMT in many ways, and should replace it. Vessel wall volume can be measured in persons with no plaque as an alternative to IMT. There are important advantages of CPB over coronary calcium; CPB should be more widely used in vascular prevention.

Ultrasound carotid plaque segmentation via image reconstruction-based self-supervised learning with limited training labels

Carotid total plaque area (TPA) is an important contributing measurement to the evaluation of stroke risk. Deep learning provides an efficient method for ultrasound carotid plaque segmentation and TPA quantification. However, high performance of deep learning requires datasets with many labeled images for training, which is very labor-intensive. Thus, we propose an image reconstruction-based self-supervised learning algorithm (IR-SSL) for carotid plaque segmentation when few labeled images are available. IR-SSL consists of pre-trained and downstream segmentation tasks. The pre-trained task learns region-wise representations with local consistency by reconstructing plaque images from randomly partitioned and disordered images. The pre-trained model is then transferred to the segmentation network as the initial parameters in the downstream task. IR-SSL was implemented with two networks, UNet++ and U-Net, and evaluated on two independent datasets of 510 carotid ultrasound images from 144 subjects at SPARC (London, Canada) and 638 images from 479 subjects at Zhongnan hospital (Wuhan, China). Compared to the baseline networks, IR-SSL improved the segmentation performance when trained on few labeled images (n = 10, 30, 50 and 100 subjects). For 44 SPARC subjects, IR-SSL yielded Dice-similarity-coefficients (DSC) of 80.14-88.84%, and algorithm TPAs were strongly correlated (r=0.962-0.993, p < 0.001) with manual results. The models trained on the SPARC images but applied to the Zhongnan dataset without retraining achieved DSCs of 80.61-88.18% and strong correlation with manual segmentation (r=0.852-0.978, p < 0.001). These results suggest that IR-SSL could improve deep learning when trained on small labeled datasets, making it useful for monitoring carotid plaque progression/regression in clinical use and trials.

Assessment of Atherosclerosis in Ischemic Stroke by means of Ultrasound of Extracranial/Intracranial Circulation and Serum, Urine, and Tissue Biomarkers

It is a common practice to take into consideration age, diabetes, smoking, treated and untreated systolic blood pressure, total cholesterol, and high-density lipoprotein cholesterol for the prediction of atherosclerosis and stroke. There are, however, ultrasound markers in use for the assessment of atherosclerosis and the evaluation of stroke risk. Two areas of investigation are of interest: the carotid artery and the intracranial arterial circulation. Again, within the domain of the carotid artery, two ultrasonic markers have attracted our attention: intima media thickness of the carotid artery and the presence of carotid plaque with its various focal characteristics. In the domain of intracranial circulation, the presence of arterial stenosis and the recruitment of collaterals are considered significant ultrasonic markers for the above-mentioned purpose. On the other hand, a series of serum, urine, and tissue biomarkers are found to be related to atherosclerotic disease. Future studies might address the issue of whether the addition of proven ultrasonic carotid indices to the aforementioned serum, urine, and tissue biomarkers could provide the vascular specialist with a better assessment of the atherosclerotic load and solidify their position as surrogate markers for the evaluation of atherosclerosis and stroke risk.

Increased circulating levels of MIP-1α and CD14 are associated with the presence of severe stenosis and hypoechoic plaques in patients with carotid atherosclerosis

OBJECTIVE

Carotid atherosclerosis, a major cause of ischemic cerebrovascular events, is characterized by a pro-inflammatory and pro-oxidant vascular microenvironment. The current risk score models based on traditional risk factors for cardiovascular risk assessment have some limitations. The identification of novel blood biomarkers could be useful to improve patient management. The aim of the study was to evaluate the association of selected inflammation- and oxidative stress-related markers with the presence of severe stenosis and/or vulnerable plaques.

METHODS

Circulating levels of soluble CD40 ligand, interleukin-10, macrophage inflammatory protein (MIP)-1α, endoglin, CD163, CD14, E-selectin, tumor necrosis factor-α, monocyte chemoattractant protein-1, C-Reactive protein, CD40 L + T lymphocytes, total antioxidant capacity, glutathione reductase activity, and protein carbonyl content were determined in patients with carotid atherosclerosis.

RESULTS

Multiparametric analysis showed significantly higher levels of MIP-1α in patients with stenosis ≥70% than in patients with stenosis <70%, and significantly higher levels of CD14 in patients with hypoechoic (vulnerable) lesions compared to those with hyperechoic (stable) ones. The area under the curve obtained by the receiver operating characteristic curve analysis was 0.7253 for MIP-1α and 0.6908 for CD14.

CONCLUSIONS

Our data suggest that circulating MIP-1α and CD14 levels are associated with the presence of advanced stenosis and of vulnerable carotid plaques.

Deep Learning-Based Carotid Plaque Segmentation from B-Mode Ultrasound Images

Carotid ultrasound measurement of total plaque area (TPA) provides a method for quantifying carotid plaque burden and monitoring changes in carotid atherosclerosis in response to medical treatment. Plaque boundary segmentation is required to generate the TPA measurement; however, training of observers and manual delineation are time consuming. Thus, our objective was to develop an automated plaque segmentation method to generate TPA from longitudinal carotid ultrasound images. In this study, a deep learning-based method, modified U-Net, was used to train the segmentation model and generate TPA measurement. A total of 510 plaques from 144 patients were used in our study, where the Monte Carlo cross-validation was used by randomly splitting the data set into 2/3 and 1/3 for training and testing. Two observers were trained to manually delineate the 510 plaques separately, which were used as the ground-truth references. Two U-Net models (M1 and M2) were trained using the two different ground-truth data sets from the two observers to evaluate the accuracy, variability and sensitivity on the ground-truth data sets used for training our method. The results of the algorithm segmentations of the two models yielded strong agreement with the two manual segmentations with the Pearson correlation coefficient r = 0.989 (p < 0.0001) and r = 0.987 (p < 0.0001). Comparison of the U-Net and manual segmentations resulted in mean TPA differences of 0.05 ± 7.13 mm² (95% confidence interval: 14.02-13.02 mm²) and 0.8 ± 8.7 mm² (17.85-16.25 mm²) for the two models, which are small compared with the TPA range in our data set from 4.7 to 312.8 mm². Furthermore, the mean time to segment a plaque was only 8.3 ± 3.1 ms. The presented deep learning-based method described has sufficient accuracy with a short computation time and exhibits high agreement between the algorithm and manual TPA measurements, suggesting that the method could be used to measure TPA and to monitor the progression and regression of carotid atherosclerosis.

Deep Learning-Based Measurement of Total Plaque Area in B-Mode Ultrasound Images

Measurement of total-plaque-area (TPA) is important for determining long term risk for stroke and monitoring carotid plaque progression. Since delineation of carotid plaques is required, a deep learning method can provide automatic plaque segmentations and TPA measurements; however, it requires large datasets and manual annotations for training with unknown performance on new datasets. A UNet++ ensemble algorithm was proposed to segment plaques from 2D carotid ultrasound images, trained on three small datasets (n = 33, 33, 34 subjects) and tested on 44 subjects from the SPARC dataset (n = 144, London, Canada). The ensemble was also trained on the entire SPARC dataset and tested with a different dataset (n = 497, Zhongnan Hospital, China). Algorithm and manual segmentations were compared using Dice-similarity-coefficient (DSC), and TPAs were compared using the difference ( ∆TPA), Pearson correlation coefficient (r) and Bland-Altman analyses. Segmentation variability was determined using the intra-class correlation coefficient (ICC) and coefficient-of-variation (CoV). For 44 SPARC subjects, algorithm DSC was 83.3-85.7%, and algorithm TPAs were strongly correlated (r = 0.985-0.988; p < 0.001) with manual results with marginal biases (0.73-6.75) mm ² using the three training datasets. Algorithm ICC for TPAs (ICC = 0.996) was similar to intra- and inter-observer manual results (ICC = 0.977, 0.995). Algorithm CoV = 6.98% for plaque areas was smaller than the inter-observer manual CoV (7.54%). For the Zhongnan dataset, DSC was 88.6% algorithm and manual TPAs were strongly correlated (r = 0.972, p < 0.001) with ∆TPA = -0.44 ±4.05 mm ² and ICC = 0.985. The proposed algorithm trained on small datasets and segmented a different dataset without retraining with accuracy and precision that may be useful clinically and for research.

Uses of ultrasound in stroke prevention

Ultrasound methods are useful in stroke prevention in several ways. Measurement of carotid plaque burden, as either total plaque area (TPA) or total plaque volume (TPV) are strong predictors of cardiovascular risk: much stronger than intima-media thickness, which does not represent true atherosclerosis, but a biologically and genetically distinct phenotype. Measurement of plaque burden is also useful for the study of genetics, and of new risk factors such as toxic products of the intestinal microbiome. Carotid plaque burden is highly correlated with and as predictive of risk as coronary calcium scores, but is less costly and does not require radiation. Furthermore, because carotid plaques change in time over a period of months, they can be used for a new approach to vascular prevention: "Treating arteries instead of treating risk factors". In high-risk patients with asymptomatic carotid stenosis (ACS), this approach, implemented in 2003 in our clinics, was associated with a >80% reduction of stroke and myocardial infarction over 2 years. "Treating arteries without measuring plaque would be like treating hypertension without measuring blood pressure". Ultrasound methods can also be used to assess plaque vulnerability, by detecting echolucency, ulceration and plaque inhomogeneity on assessment of plaque texture. Transcranial Doppler (TCD) embolus detection is useful for risk stratification in patients with ACS; patients with two or more microemboli in an hour of monitoring have a 1-year risk of 15.6%, vs. 1% without microemboli, so this very clearly distinguishes which patients with ACS could benefit from intervention. TCD saline studies are more sensitive than trans-esophageal echocardiography for detection of patent foramen ovale, and more predictive of recurrent stroke. These methods should be more widely used, to reduce the increasing burden of stroke in our aging populations.

Traffic-Related Air Pollution and Carotid Plaque Burden in a Canadian City With Low-Level Ambient Pollution

Background

The association between fine particulate matter and cardiovascular disease has been convincingly demonstrated. The role of traffic‐related air pollutants is less clear. To better understand the role of traffic‐related air pollutants in cardiovascular disease development, we examined associations between NO₂, carotid atherosclerotic plaque, and cardiometabolic disorders associated with cardiovascular disease.

Methods and Results

Cross‐sectional analyses were conducted among 2227 patients (62.9±13.8 years; 49.5% women) from the Stroke Prevention and Atherosclerosis Research Centre (SPARC) in London, Ontario, Canada. Total carotid plaque area measured by ultrasound, cardiometabolic disorders, and residential locations were provided by SPARC medical records. Long‐term outdoor residential NO₂ concentrations were generated by a land use regression model. Associations between NO₂, total carotid plaque area, and cardiometabolic disorders were examined using multiple regression models adjusted for age, sex, smoking, and socioeconomic status. Mean NO₂ was 5.4±1.6 ppb in London, Ontario. NO₂ was associated with a significant increase in plaque (3.4 mm² total carotid plaque area per 1 ppb NO₂), exhibiting a linear dose‐response. NO₂ was also positively associated with triglycerides, total cholesterol, and the ratio of low‐ to high‐density lipoprotein cholesterol (P<0.05). Diabetes mellitus mediated the relationship between NO₂ and total carotid plaque area (P<0.05).

Conclusions

Our results demonstrate that even low levels of traffic‐related air pollutants are linked to atherosclerotic plaque burden, an association that may be partially attributable to pollution‐induced diabetes mellitus. Our findings suggest that reducing ambient concentrations in cities with NO₂ below current standards would result in additional health benefits. Given the billions of people exposed to traffic emissions, our study supports the global public health significance of reducing air pollution.

Usefulness of Carotid Plaques as Predictors of Obstructive Coronary Artery Disease and Cardiovascular Events in Asymptomatic Individuals With Diabetes Mellitus

Carotid intima-media thickness (CIMT) measurement and carotid plaque detection by B-mode ultrasound are frequently used as surrogates to predict coronary artery disease (CAD). However, their systematic use in routine clinical management of asymptomatic patients with diabetes mellitus (DM) has not been studied. The aim of the study was to identify carotid parameters that predict cardiovascular events in patients with asymptomatic type 2 DM by evaluating the relation between carotid disease and CAD. This multicenter, observational, prospective study included 259 asymptomatic patients with type 2 DM followed-up for 34 months after measurement of CIMT and carotid plaque with carotid ultrasound, and CAD assessment with computed tomography coronary angiography. Statistically significant differences between patients with and without carotid plaque were found for coronary plaque >50% stenosis (59 vs 36, p = 0.02). Greater maximal CIMT was associated with an increased risk of coronary plaque >50% (odds ratio 1.21 [1.02, 1.44], p = 0.03) and >70% stenosis (odds ratio 1.23 [1.01, 1.50], p = 0.04) after adjusting for traditional risk factors. At 34-month follow-up, the occurrence of total major adverse cardiovascular event was estimated to be 7.1% (mean age 68 years, 6% male and 1.1% female) in the whole study population. The subgroup of patients with carotid plaque showed increased incidence of major adverse cardiovascular event compared with patients with no carotid plaque (p = 0.005). In conclusion, carotid plaque was a strong predictor of future cardiovascular events and may be a prognostic marker in asymptomatic patients with type 2 DM. Carotid plaque and maximal intima-media thickness were independently associated with obstructive CAD.

Association of body flexibility and carotid atherosclerosis in Japanese middle-aged men: a cross-sectional study

OBJECTIVE

This study examined the associations of body flexibility with carotid arterial remodelling, including intima-media thickness (IMT) and plaque formation in middle-aged men.

METHODS

The subjects of this cross-sectional study included 1354 Japanese men aged 35-59 years without histories of stroke or cardiac diseases. The arm extensibility test, which can estimate flexibility of the upper extremity (composed of shoulder external rotation and forearm supination), and the sit-and-reach test were performed. Common carotid IMT and plaque formation (≥1.1 mm) were estimated by ultrasound.

RESULTS

The proportion of subjects who fully completed the arm extensibility test was 55.0%, and who had plaques in the common carotid artery was 37.8%. IMT was associated with poor arm extensibility (β=-0.073, 95% CI -0.02224 to -0.00041, P=0.004), while plaque formation was associated with poor sit-and-reach (OR 0.98579, 95% CI 0.97257 to 0.99919, P=0.038) after adjustment by all covariates.

CONCLUSIONS

This study demonstrated that poor upper extremity and trunk flexibility were associated with characteristics of early onset of atherosclerosis. Furthermore, these associations were independent of covariates such as age, blood pressure, blood lipids glucose levels and abdominal fat accumulation, handgrip strength and lifestyle, including sleeping, drinking, exercise and smoking habits. Poor flexibility may reflect subclinical atherosclerosis in middle-aged men.

Genome-wide admixture and association study of subclinical atherosclerosis in the Women's Interagency HIV Study (WIHS)

Cardiovascular disease (CVD) is a major comorbidity among HIV-infected individuals. Common carotid artery intima-media thickness (cCIMT) is a valid and reliable subclinical measure of atherosclerosis and is known to predict CVD. We performed genome-wide association (GWA) and admixture analysis among 682 HIV-positive and 288 HIV-negative Black, non-Hispanic women from the Women’s Interagency HIV study (WIHS) cohort using a combined and stratified analysis approach. We found some suggestive associations but none of the SNPs reached genome-wide statistical significance in our GWAS analysis. The top GWAS SNPs were rs2280828 in the region intergenic to mediator complex subunit 30 and exostosin glycosyltransferase 1 (MED30 | EXT1) among all women, rs2907092 in the catenin delta 2 (CTNND2) gene among HIV-positive women, and rs7529733 in the region intergenic to family with sequence similarity 5, member C and regulator of G-protein signaling 18 (FAM5C | RGS18) genes among HIV-negative women. The most significant local European ancestry associations were in the region intergenic to the zinc finger and SCAN domain containing 5D gene and NADH: ubiquinone oxidoreductase complex assembly factor 1 (ZSCAN5D | NDUF1) pseudogene on chromosome 19 among all women, in the region intergenic to vomeronasal 1 receptor 6 pseudogene and zinc finger protein 845 (VN1R6P | ZNF845) gene on chromosome 19 among HIV-positive women, and in the region intergenic to the SEC23-interacting protein and phosphatidic acid phosphatase type 2 domain containing 1A (SEC23IP | PPAPDC1A) genes located on chromosome 10 among HIV-negative women. A number of previously identified SNP associations with cCIMT were also observed and included rs2572204 in the ryanodine receptor 3 (RYR3) and an admixture region in the secretion-regulating guanine nucleotide exchange factor (SERGEF) gene. We report several SNPs and gene regions in the GWAS and admixture analysis, some of which are common across HIV-positive and HIV-negative women as demonstrated using meta-analysis, and also across the two analytic approaches (i.e., GWA and admixture). These findings suggest that local European ancestry plays an important role in genetic associations of cCIMT among black women from WIHS along with other environmental factors that are related to CVD and may also be triggered by HIV. These findings warrant confirmation in independent samples.

Definition of common carotid wall thickness affects risk classification in relation to degree of internal carotid artery stenosis: the Plaque At RISK (PARISK) study

Background

Mean or maximal intima-media thickness (IMT) is commonly used as surrogate endpoint in intervention studies. However, the effect of normalization by surrounding or median IMT or by diameter is unknown. In addition, it is unclear whether IMT inhomogeneity is a useful predictor beyond common wall parameters like maximal wall thickness, either absolute or normalized to IMT or lumen size. We investigated the interrelationship of common carotid artery (CCA) thickness parameters and their association with the ipsilateral internal carotid artery (ICA) stenosis degree.

Methods

CCA thickness parameters were extracted by edge detection applied to ultrasound B-mode recordings of 240 patients. Degree of ICA stenosis was determined from CT angiography.

Results

Normalization of maximal CCA wall thickness to median IMT leads to large variations. Higher CCA thickness parameter values are associated with a higher degree of ipsilateral ICA stenosis (p < 0.001), though IMT inhomogeneity does not provide extra information. When the ratio of wall thickness and diameter instead of absolute maximal wall thickness is used as risk marker for having moderate ipsilateral ICA stenosis (>50%), 55 arteries (15%) are reclassified to another risk category.

Conclusions

It is more reasonable to normalize maximal wall thickness to end-diastolic diameter rather than to IMT, affecting risk classification and suggesting modification of the Mannheim criteria.

Trial registration

Clinical trials.gov NCT01208025.

Carotid Intima-Media Thickness is Not Associated with Markers of Atherosclerosis in Stroke Patients

BACKGROUND

It has been argued that carotid intima-media thickness (IMT) could better reflect an adaptive response of the vessel wall rather than being a marker of atherosclerosis. We explore this hypothesis by analyzing the ARTICO data.

METHODS

The ARTICO study was designed to evaluate the prognostic value of the pathological ankle-brachial index (ABI) for the emergence of new vascular events in patients who have suffered a noncardioembolic stroke. Collected variables were as follows: vascular risk factors, mean waist perimeter, quantification of carotid IMT, characteristics of carotid plaques, ABI, and presence of microalbuminuria.

RESULTS

A total of 591 patients with a complete carotid evaluation were available. There was no correlation between ABI and IMT (Spearman's, p NS). Logistic regression revealed that pathological ABI correlated significantly only with internal carotid artery stenosis greater than or equal to 50% (OR [odds ratio] 2.80, 1.66-4.71, P < .01) and peripheral artery disease (OR 3.33, 1.63-6.78, P < .01). However, multivariate regression analysis demonstrated that carotid IMT was independently associated with age (OR 1.05, 95% confidence interval [CI] 1.02-1.09, P < .01), hypertension (OR 1.83, 95% CI 1.02-3.26, P = .04), waist circumference (OR 1.03, 95% CI 1.01-1.05, P < .01), and microalbuminuria (OR 2.02, 95% CI 1.22-3.35, P < .01).

CONCLUSION

In our patients, carotid IMT does not seem to be associated with unequivocal markers of atheromatosis such as the existence of relevant carotid plaques or pathological ABI. These results as well as the association of IMT with age, hypertension, microalbuminuria, and mean waist perimeter support the hypothesis that IMT must be considered a risk factor for general vascular disease rather than a marker of atherosclerotic burden.

Compensatory intracranial arterial dilatation in extracranial carotid atherosclerosis: the Northern Manhattan study

BACKGROUND

There is a scarcity of data supporting the association between atherosclerosis and dolichoectasia in unbiased samples.

AIMS

To test the hypothesis that the association between dolichoectasia and extracranial carotid atherosclerosis depends on the degree of collateral circulation.

METHODS

The Northern Manhattan Study magnetic resonance imaging substudy consists of 1290 participants who remained stroke-free at the time of magnetic resonance imaging. Arterial diameters were collected in all participants with available magnetic resonance angiography. Dolichoectasia was defined as a head-size adjusted diameter >2 standard deviation for each artery. Carotid Doppler was used to evaluate for carotid atherosclerosis (carotid plaque, maximum plaque thickness and carotid intima media thickness).

RESULTS

We included 994 participants with available Doppler and magnetic resonance angiography data (mean age 63 years, 60% female). Any dolichoectasia was reported in 16% of participants, 54% had at least one carotid plaque and the mean carotid intima media thickness was 0·92 ± 0·09 mm. After adjusting for demographic and clinical characteristics, there was no association between markers of carotid atherosclerosis and dolichoectasia. However, stratifying by collaterals, it was observed that dolichoectasia was more likely in the anterior and posterior circulations when collaterals were available among participants with carotid atherosclerosis. These associations were confirmed by noting an increment in arterial diameters in the corresponding arteries ipsilateral and contralateral to each carotid as well as in the posterior circulation.

CONCLUSIONS

We did not find an association of extracranial carotid atherosclerosis with dolichoectasia. However, we found that dolichoectasia is more frequent when intracranial collaterals are available suggesting a compensatory process that needs further investigation.

Genetic epidemiology and genome-wide linkage analysis of carotid artery ultrasound traits in multigenerational African ancestry families

OBJECTIVE

Intima-media thickness, adventitial diameter and lumen diameter are indicators of cardiovascular disease risk. The influence of genetic factors on these measures in African ancestry populations is not well defined. Therefore, we estimated heritability and performed genome-wide linkage analysis of carotid ultrasound traits in 7 multigenerational families of African ancestry.

METHODS

A total of 395 individuals (7 pedigrees; mean family size = 56; 2392 relative pairs) aged ≥18 years had a common carotid artery ultrasound scan. Statistical analyses were conducted using pedigree-based maximum likelihood methods.

RESULTS

Significant covariates included age, sex, body mass index or height and waist, and systolic blood pressure. Residual heritabilities ranged from 0.35 ± 0.10 to 0.64 ± 0.12 (P < 0.0001). We identified a novel quantitative trait locus for adventitial and lumen diameters on chromosome 11 (max LOD = 4.09, 133 cm).

CONCLUSION

Further fine mapping of this region may identify specific mutations predisposing to subclinical vascular disease among African ancestry individuals.

Genetic architecture of carotid artery intima-media thickness in Mexican Americans

BACKGROUND- Intima-media thickness (IMT) of the common and internal carotid arteries is an established surrogate for atherosclerosis and predicts risk of stroke and myocardial infarction. Often IMT is measured as the average of these 2 arteries; yet, they are believed to result from separate biological mechanisms. The aim of this study was to conduct a family-based genome-wide association study (GWAS) for IMT to identify polymorphisms influencing IMT and to determine if distinct carotid artery segments are influenced by different genetic components. METHODS AND RESULTS- IMT for the common and internal carotid arteries was determined through B-mode ultrasound in 772 Mexican Americans from the San Antonio Family Heart Study. A GWAS using 931219 single-nucleotide polymorphisms was undertaken with 6 internal and common carotid artery IMT phenotypes using an additive measured genotype model. The most robust association detected was for 2 single-nucleotide polymorphisms (rs16983261, rs6113474; P=1.60e(-7)) in complete linkage disequilibrium on chromosome 20p11 for the internal carotid artery near wall, next to the gene PAX1. We also replicated previously reported GWAS regions on chromosomes 19q13 and 7q22. We found no overlapping associations between internal and common carotid artery phenotypes at P<5.0e(-6). The genetic correlation between the 2 carotid IMT arterial segments was 0.51. CONCLUSIONS- This study represents the first large-scale GWAS of carotid IMT in a non-European population and identified several novel loci. We do not detect any shared GWAS signals between common and internal carotid arterial segments, but the moderate genetic correlation implies both common and unique genetic components.

Value of carotid intima-media thickness and significant carotid stenosis as markers of stroke recurrence

BACKGROUND AND PURPOSE

Data on the predictive value of carotid intima-media thickness (IMT) for stroke recurrence are scarce. We sought to analyze outcome differences in stroke patients with high IMT values compared with patients with significant carotid stenosis (SCS).

METHODS

The multicenter observational ARTICO study included 620 independent patients older than 60 years with a first-ever noncardioembolic stroke. Patients were followed-up for 1 year. The primary end point was a composite of cardiovascular events and death. The IMT-ARTICO substudy analyzed ultrasonographic data from 599 patients. After Doppler carotid echography, patients were classified into the SCS group (carotid stenosis ≥50%; 117 cases), high IMT group (patients with the common carotid IMT in the highest quartile ≥1.11 mm and without SCS; 110 cases), and control group (stroke patients with an IMT <1.11 mm and without SCS; 372 cases). We analyzed the impact of both conditions on the primary end point.

RESULTS

During follow-up, 88 patients (14.7%) had an end point event. Univariate analysis showed that male gender, diabetes, symptomatic peripheral arterial disease, ankle brachial index ≤0.9, SCS, and high IMT were related to the primary end point. Cox regression showed that peripheral arterial disease (hazard ratio [HR], 2.06; 95% confidence interval [CI], 1.18-3.59; P=0.011), SCS (HR, 3.02; 95% CI, 1.78-5.13; P=0.0001), and high IMT (HR, 1.86; 95% CI, 1.05-3.29; P=0.032) were related to the primary end point. If patients with scheduled revascularization procedures were excluded from the Cox regression, then ultrasonographic markers were SCS (HR, 1.84; 95% CI, 1.03-3.28; P<0.039) and high IMT (HR, 1.86; 95% CI, 1.06-3.27; P=0.030).

CONCLUSIONS

Both SCS and high IMT have an independent impact as markers of major cardiovascular events or death after a first-ever noncardioembolic stroke.

Modern ultrasound methods and atherosclerosis assessment in patients with familial hypercholesterolemia

Familial hypercholesterolemia (FHCH) is characterised by early atherosclerosis development and its fast progression. The prevalence of FHCH inRussiahas been increasing, therefore, it is important to evaluate the potential of various methods for atherosclerosis diagnostics. Arterial ultrasound is an informative, accessible, and safe method for evaluating atherosclerotic vascular changes. The modern ultrasound methods allow describing vascular wall status in detail, including qualitative and quantitative characteristics of its structure and function. At the same time, most ultrasound characteristics of arterial wall are used in research settings or are under development, and not implemented into clinical practice. The most promising parameters, applicable for clinical use in FHCH patients, simultaneously describe atherosclerosis severity and its localization, such as total plaque height, ankle-brachial index, and plaque number.

Genomewide linkage and peakwide association analyses of carotid plaque in Caribbean Hispanics

BACKGROUND AND PURPOSE

Atherosclerosis is a complex subclinical cardiovascular disorder with a substantial genetic component. This study sought to identify genetic loci influencing carotid plaque in 2 independent samples.

METHODS

B-mode ultrasound was performed to determine the presence and area of carotid plaque. Variance components analysis was used to test for linkage using 383 autosomal microsatellite markers in 1308 subjects from 100 Dominican families. Multiple linear and logistic regression models were used to investigate the association between plaque traits and 18,904 single nucleotide polymorphisms under the 1-logarithm of odds unit down regions of linkage peaks in an independent community-based data set (N = 941, 41% Dominicans) from the Northern Manhattan Study.

RESULTS

After adjustment for age, hypertension, diabetes mellitus, cigarette pack-years, body mass index, and waist-to-hip ratio, significant heritability was detected for plaque presence (h² = 0.50 ± 0.14, P < 0.0001) and plaque area (h²=0.17 ± 0.04, P < 0.0001). Quantitative and dichotomous trait linkage analyses obtained similar results and identified 4 regions with multipoint logarithm of odds scores ≥ 2.00 on 7q36, 11p15, 14q32, and 15q23. In the association analysis of the 4 linkage peaks, several single nucleotide polymorphisms in or near SOX6, FSD2, AP3S2, EFTUD1, and MYOD1 were associated with carotid plaque traits with a nominal P ≤ 0.0005 in the Northern Manhattan Study data set and with a P ≤ 0.01 in Northern Manhattan Study Dominican subset.

CONCLUSIONS

Carotid plaque has considerable heritability and may be influenced by loci on chromosomes 11p15, 14q32, and 15q23. The SOX6 gene within the bone morphogenic protein pathway could be a candidate for carotid plaque. Larger independent studies are needed to validate these findings.

The relationship of menopausal status and rapid menopausal transition with carotid intima-media thickness progression in women: a report from the Los Angeles Atherosclerosis Study

CONTEXT

The onset of menopause has been associated with an increase in cardiovascular risk factors. However, little information is available about the rapidity of the menopausal transition and its relationship to the development of preclinical cardiovascular disease (CVD).

OBJECTIVE

Our objective was to assess whether the rate of carotid intima-media thickness (cIMT) progression over time differs according to 1) menopausal status and 2) rapidity of the menopausal transition.

DESIGN

We evaluated 203 community-based women aged 45-60 yr without previously diagnosed CVD who underwent three repeated measurements of cIMT as a measure of preclinical CVD over 3 yr. Menopausal status was ascertained at each visit based on menstrual cycle parameters and reproductive hormone profiles. Of these, 21 remained premenopausal, 51 transitioned, and 131 were postmenopausal throughout the observation period.

RESULTS

Age-adjusted cIMT progression rates were similar among premenopausal, transitioning, and postmenopausal women. In the 51 transitioning women, age was not related to rate of cIMT progression. However, the rapidity of menopausal transition was related to cIMT progression: women transitioning from pre- to postmenopause within the 3-yr period had a higher rate of cIMT progression compared with women with a slower transition. Statistical adjustments for the significant covariates of systolic blood pressure, body mass index, race, cigarette smoking, or hormone therapy use did not alter the findings.

CONCLUSIONS

Among healthy women undergoing repeated cIMT measurement, a more rapid menopausal transition was associated with a higher rate of preclinical CVD progression measured by cIMT. Further work is needed to explore potential mechanisms of this effect.

The Value of Carotid Intima-Media Thickness for Predicting Cardiovascular Risk

We reviewed prospective epidemiological data in the general population, mostly middle-aged to older persons, to determine the association of carotid intima-media thickness (CIMT) (assessed by B-mode ultrasonography) with cardiovascular risk. Reported risks were expressed as absolute (event risk per persons-years in subjects with a high CIMT) and relative (hazard ratio of high vs low CIMT). They were hardly comparable as the result of differences between the analyzed studies, including the site and procedure of CIMT measurement, the report of adjusted or unadjusted models, and the arbitrary cutoff point to evaluate the CIMTÆs ability to predict risk. Despite these heterogeneities, the following four main conclusions emerged: (1) CIMT was an independent but relatively modest (as judged by absolute risk) predictor of coronary heart disease (CHD); (2) CIMT was an independent predictor for stroke, slightly better than for CHD as judged by the relative risks of both events; (3) CIMT added little to the CHD prediction by risk factors, as judged by c statistic and receiver operating characteristic curve analysis (however, appropriate data for stroke on this important issue were lacking); and (4) the CHD prediction by CIMT was inferior to that by ultrasonography-assessed carotid plaque because plaque may be more representative of atherosclerosis than CIMT.

Multi-ethnic genetic association study of carotid intima-media thickness using a targeted cardiovascular SNP microarray

BACKGROUND AND PURPOSE

Identification of subclinical atherosclerosis by ultrasonographic measurement of carotid intima-media thickness (IMT) is a validated tool, in conjunction with traditional risk factors, for clinical assessment of cardiovascular disease risk. IMT has also been recognized as a quantitative measure of cardiovascular disease progression in asymptomatic individuals, and many candidate gene association studies have attempted to identify genetic variants associated with interindividual differences in IMT with limited success. We sought to test the association between subclinical atherosclerosis measured by IMT and approximately 50,000 SNPs, densely mapping approximately 2100 genes found on the gene-centric Illumina cardiovascular disease beadchip in a multi-ethnic population-based sample.

METHODS

IMT was measured by B-mode ultrasound and DNA was collected from a population-based sample of South Asian (n=328), Chinese (n=302), and European Caucasian (n=268) participants. Genetic association was measured using multivariate linear regression including adjustment for covariates.

RESULTS

The most robust association across all models tested was observed for a SNP (rs3791398) in histone deacetylase 4 (HDAC4; P=1.8e-5 to P=3.6e-5), while another strong association signal was observed with natriuretic peptide receptor a/guanylate cyclase A (NPR1) (rs10082235, P=5.4e-5). Seven of 13 previously reported functional candidate genes contained a SNP that was marginally associated (0.01 < P < or = 0.05).

CONCLUSION

This initial multi-ethnic high-density association study of carotid IMT suggests some novel loci requiring further evaluation in follow-up studies.

Carotid and femoral arterial wall changes and the prevalence of clinical cardiovascular disease

Abstract

The Cyprus Study is a prospective cohort study of cardiovascular disease (CVD). Its aim is to determine the relationship of intima–media thickness (IMT) of the common carotid (IMTcc), maximum thickness of IMT in the carotid bifurcation (IMTmax), number of carotid and femoral bifurcations with plaque and total plaque thickness (TPT) (sum of the maximum plaque measurements taken from the four bifurcations scanned) with the prevalence of clinical CVD. A total of 767 individuals (46% male) over the age of 40 years were recruited from a mountain village and a town outside the capital Nicosia. In addition to clinical examination, carotid and common femoral bifurcations were scanned with ultrasound. After controlling for conventional risk factors, there was little evidence of an association of IMTcc with CVD prevalence. However, IMTmax and TPT were associated with 2.9-fold (1.22 to 7.07) and 6.87-fold (2.42 to 19.43) increased odds of CVD prevalence, respectively. In conclusion, the TPT and number of bifurcations with plaque are more strongly associated with the prevalence of CVD. These findings warrant investigation in prospective studies to document associations with incident CVD events.

Risk factors for cardiovascular disease do not fully explain differences in carotid intima-media thickness between Indigenous and European Australians without diabetes

OBJECTIVE

To investigate whether cardiovascular risk factors can explain the higher carotid intima-media thickness (CIMT) in Indigenous compared with European Australians.

DESIGN

Cross-sectional study in three subgroups.

PATIENTS

Non-diabetic urban European (n = 86), urban Indigenous (n = 69), and remote Indigenous (n = 60) Australians aged 25-64 years.

MEASUREMENTS

CIMT, age, sex, anthropometry, blood pressure, smoking status, fasting glucose and insulin, haemoglobin (Hb)A1c, homocysteine, C-reactive protein (CRP), lipids, urinary albumin and creatinine.

RESULTS

CIMT and levels of risk factors, except fasting glucose and total cholesterol, worsened across the three groups. Log(n) fasting insulin [beta = 0.022, 95% confidence interval (CI) 0-0.0439], age (beta = 0.006, 95% CI 0.004-0.007), gender (female beta = -0.005 vs. male, 95% CI -0.084 to -0.026), mean arterial pressure (MAP) (beta = 0.001, 95% CI 0.001-0.002) and ethnicity/location [urban Indigenous (beta = 0.027, 95% CI -0.010 to 0.064 vs. European); remote Indigenous (beta = 0.083, 95% CI 0.042-0.123 vs. European)] explained 41% of variance in CIMT. Significant interactions were seen for ethnicity/location with age (P = 0.014) and MAP (P = 0.018). Age was consistently associated with CIMT across the three populations, and was associated with larger increments in CIMT for the Indigenous subgroups (beta = 0.007, 95% CI 0.005-0.009 urban; beta = 0.007, 95% CI 0.004-0.010 remote) compared with Europeans (beta = 0.003, 95% CI 0.002-0.006) in models including age, sex and MAP. MAP was only associated with CIMT in the remote Indigenous subgroup.

CONCLUSION

After adjusting for selected risk factors, CIMT in remote Indigenous participants was still higher than in Europeans. The slope of the association between age and CIMT steepened from urban Europeans to remote Indigenous.

Heritability and linkage analysis for carotid intima-media thickness: the family study of stroke risk and carotid atherosclerosis

BACKGROUND AND PURPOSE

The aim of this study was to identify quantitative trait loci (QTL) for carotid intima-media thickness (CIMT) a risk factor for stroke and cardiovascular disease.

METHODS

Probands were selected from Caribbean Hispanic subjects of the population-based Northern Manhattan Study. CIMT was measured by high-resolution B-mode ultrasound and expressed as the mean (IMTx) and mean of the maximum (IMTm). Variance components methodology was used to detect linkage using SOLAR and calculate locus-specific heritability. Ordered-subset Analysis was done based on history of hypertension and total cholesterol levels.

RESULTS

Among 100 Dominican families, 1390 subjects had CIMT measured (848 females; mean age 46.2 years). CIMT had a heritability of 0.65 after adjusting for age, age(2), sex, cigarette pack-years, waist hip ratio, and BMI. Adjusted maximum multipoint LOD scores >2 were found on chromosomes 14q (D14S606) and 7p (D7S817). Linkage to chromosome 14q was significantly increased in a subset of families with the greatest history of hypertension (MLOD=4.12). The QTL on Ch14q accounted for 0.21 of the heritability of IMTm, and on Ch7p 0.27 of the heritability of BIFm.

CONCLUSIONS

Several QTLs for CIMT were found on chromosomes 7p and 14q. The QTL on 14q replicates a suggestive linkage peak delimited in the Framingham Heart Study. These QTLs accounted for a substantial amount of trait heritability and warrant further fine mapping.

Keloid scarring, but not Dupuytren's contracture, is associated with unexplained carotid atherosclerosis

BACKGROUND

Atherosclerosis, a response to injury, may be thought of as scarring in the artery wall. TGF-beta and associated signaling molecules have been implicated in the pathophysiology of keloid scarring, Dupuytren's Contracture and atherosclerotic plaques in independent studies.

PURPOSE

To test the hypothesis that excess cutaneous scarring and Dupuytren's contractures predispose independently to carotid atherosclerosis .

METHODS

Among 1,747 patients with plaque measurements and complete data for multivariable regression analysis, 57 Caucasian patients had Dupuytren's contractures and 12 had keloid scars. Carotid total plaque area (TPA) was measured by 2-Dimensional ultrasound.

RESULTS

In linear multivariable regression analysis with coronary risk factors, keloid scars were associated with TPA (P= 0.018), but Dupuytren's contractures were not. Patients with keloid scarring were younger (P < 0.0001), and more likely to be diabetic (P < 0.0001)

CONCLUSIONS

Keloid scarring is a clinical clue to excess atherosclerosis not explained by traditional risk factors. Such patients may benefit from therapy directed at targets related to signalling molecules common to both the process of keloid scarring and atherosclerosis. These findings suggest previously unexplored possibilities for the prevention and treatment of atherosclerosis. The differences between Dupuytren's and keloid scars that may identify such targets are discussed.

Carotid plaque compared with intima-media thickness as a predictor of coronary and cerebrovascular disease

Atherosclerosis is the underlying cause of most myocardial infarction (MI) and ischemic strokes. B-mode ultrasound of carotid arteries provides measures of intima-media thickness (IMT) and plaques, both widely used as surrogate measures of cardiovascular disease. Although IMT and plaques are highly intercorrelated, IMT's role as a marker of atherosclerosis has been questioned, especially when measurements include the common carotid artery (CCA) only. Plaque and intima-media thickening may reflect different biological aspects of atherogenesis with distinctive relations to clinical vascular disease. Plaque measured in the carotid bulb or internal carotid artery is stronger related to hyperlipidemia and smoking and is a stronger predictor for MI, whereas CCA-IMT is stronger related to hypertension and ischemic stroke. Echolucent plaque morphology (ie, lipid-rich plaques) seems to increase the risk for MI and stroke. New evidence suggests that total plaque area is the most strongly predictive of cardiovascular risk of the ultrasound phenotypes.

Measurement of intima-media thickness vs. carotid plaque: uses in patient care, genetic research and evaluation of new therapies

Intima-media thickness (IMT) has been measured for over 20 years, and is widely regarded as a surrogate for atherosclerosis. However, in the carotid arteries atherosclerosis is focal, manifesting as plaques. IMT is often measured deliberately where no plaque exists, or multiple measurements may be averaged, including only one or two that intersect plaque. IMT and plaque are biologically and genetically distinct, so they can be expected to respond differentially to therapies for atherosclerosis. Furthermore, because plaques grow along the carotid arteries 2.4 times faster than they thicken, progression or regression of total plaque area is more sensitive to effects of therapy than IMT. Because plaques also grow and regress circumferentially, three-dimensional (3-D) plaque volume is two orders of magnitude more sensitive to effects of therapy than is IMT. While 3-D ultrasound requires special equipment, total plaque area can be measured using the same equipment as IMT. Because plaque and IMT are biologically and genetically distinct entities, representing different phenotypes of atherosclerosis, both should be measured in any situation where IMT is measured, with the exception of studies in children too young for the occurrence of plaque. IMT should not be called 'atherosclerosis': the phenotype being assessed should be specified.

Comparison of B-mode ultrasound, 3-dimensional ultrasound, and magnetic resonance imaging measurements of carotid atherosclerosis

OBJECTIVE

We compared the intraobserver and interscan variability of carotid atherosclerosis measured using B-mode ultrasound for quantifying intima media thickness (IMT), 3-dimensional ultrasound (3DUS) for quantifying vessel wall volume (VWV) and total plaque volume (TPV), and magnetic resonance imaging (MRI) for measuring VWV. We also evaluated the associations of these measurements and sample sizes required to detect specific changes in patients with moderate atherosclerosis.

METHODS

Ten patients were evaluated with B-mode ultrasound, MRI, and 3DUS twice within 14 +/- 2 days. Measurements of IMT, MRI VWV, 3DUS VWV, and 3DUS TPV were performed by single observers using manual (VWV and TPV) and semiautomated (IMT) segmentation.

RESULTS

Intraobserver coefficients of variation were 3.4% (IMT), 4.7% (3DUS VWV), 6.5% (MRI VWV), and 23.9% (3DUS TPV). Interscan coefficients of variation were 8.1% (MRI VWV), 8.9% (IMT), 13.5% (3DUS VWV), and 46.6% (3DUS TPV). Scan-rescan linear regressions were significant for 3DUS TPV (R(2) = 0.57), 3DUS VWV (R(2) = 0.59), and IMT (R(2) = 0.75) and significantly different (P < .05) for MRI VWV (R(2) = 0.87).

CONCLUSIONS

B-mode ultrasound-derived IMT provided the highest intraobserver and interscan reproducibility. Three-dimensional measurements of VWV derived from 3DUS and MRI provided both high sensitivity and high intraobserver and interscan reliability.

Heritability of carotid intima-media thickness: a twin study

OBJECTIVE

To estimate the heritability of carotid intima-media thickness (IMT), a surrogate marker for atherosclerosis, independent of traditional coronary risk factors.

METHODS AND RESULTS

We performed a classical twin study of carotid IMT using 98 middle-aged male twin pairs, 58 monozygotic (MZ) and 40 dizygotic (DZ) pairs, from the Vietnam Era Twin Registry. All twins were free of overt cardiovascular disease. Carotid IMT was measured by ultrasound. Bivariate and multivariate analyses were used to determine the association between traditional cardiovascular risk factors and carotid IMT. Intraclass correlation coefficients and genetic modeling techniques were used to determine the relative contributions of genes and environment to the variation in carotid IMT. In our sample, the mean of the maximum carotid IMT was 0.75+/-0.11. Age, systolic blood pressure and HDL were significantly associated with carotid IMT. The intraclass correlation coefficient for carotid IMT was larger in MZ (0.66; 95% confidence interval [CI], 0.62-0.69) than in DZ twins (0.37; 95% CI, 0.29-0.44), and the unadjusted heritability was 0.69 (95% CI, 0.54-0.79). After adjusting for traditional coronary risk factors, the heritability of carotid IMT was slightly reduced but still of considerable magnitude (0.59; 95% CI, 0.39-0.73).

CONCLUSION

Genetic factors have a substantial influence on the variation of carotid IMT. Most of this genetic effect occurs through pathways independent of traditional coronary risk factors.

Intensive management of risk factors for accelerated atherosclerosis: the role of multiple interventions

Patients at high risk of vascular events can reduce their risk by 75% to 80% through a combination of lifestyle changes and medical therapy. These include smoking cessation, a Mediterranean diet, daily exercise, maintaining a fit weight, moderate consumption of alcohol, effective control of blood pressure and diabetes, intensive treatment with lipid-lowering drugs and antiplatelet agents, and perhaps treatment with vitamins to lower homocysteine. Much of this is achieved primarily by the patient; physicians need to become better at assisting their patients in making lifestyle changes. Effective control of treatment-resistant hypertension can be improved by individualizing medical therapy to the underlying cause, based on measurement of plasma renin and aldosterone. Measurement of carotid plaque may be useful by providing feedback on the success of therapy.

Technology Insight: ultrasound measurement of carotid plaque--patient management, genetic research, and therapy evaluation

Various methods have been used to quantify atherosclerosis, beginning in the mid-1980s with ultrasound measurement of carotid intima-media thickness (IMT), and going on to coronary calcification assessed by electron-beam CT, measurement of carotid plaque by ultrasound, and measurement of carotid wall thickness by MRI. In recent years, it has become clear that carotid IMT, coronary calcification and carotid plaque reflect biologically and genetically different aspects of the atherosclerotic process, and will respond differentially to therapy. IMT represents mainly hypertensive medial hypertrophy; this measure is more predictive of stroke than of myocardial infarction, and is only weakly associated with traditional coronary risk factors. Carotid plaque area, on the other hand, is more strongly associated with traditional risk factors, and is more predictive of myocardial infarction than of stroke. A quantitative trait, called 'unexplained atherosclerosis', expresses the extent to which an individual has excess carotid plaque not explained by traditional risk factors, or the extent to which an individual is protected from traditional risk factors. Unexplained progression of plaque is an even more powerful tool for genetic research, because age, which accounts for the greatest proportion of baseline plaque, has much less influence on the rate of progression. Compared with IMT, measurement of carotid plaque volume by three-dimensional ultrasound reduces by two orders of magnitude the sample size and duration of treatment needed to evaluate new therapies. Measurement of carotid plaque is, therefore, an important tool for patient management, genetic research and evaluation of new therapies for stroke prevention.