Spatial distribution of carotid intimal-medial thickness as measured by B-mode ultrasonography

KD Diagnosis Does Not Increase Cardiovascular Risk in Children According to Dynamic Intima-Media Roughness Measurements

Background: Kawasaki Disease (KD) is a generalized vasculitis in childhood with possible long-term impact on cardiovascular health besides the presence of coronary artery lesions. Standard vascular parameters such as carotid intima–media thickness (cIMT) have not been established as reliable markers of vascular anomalies after KD. The carotid intima–media roughness (cIMR) representing carotid intimal surface structure is considered a promising surrogate marker for predicting cardiovascular risk even beyond cIMT. We therefore measured cIMR in patients with a history of KD in comparison to healthy controls to investigate whether KD itself and/or KD key clinical aspects are associated with cIMR alterations in the long-term. Methods: We assessed cIMR in this case-control study (44 KD, mean age in years (SD); 13.4 (7.5); 36 controls, mean age 12.1 (5.3)) approximately matched by sex and age. Different clinical outcomes such as the coronary artery status and acute phase inflammation data were analyzed in association with cIMR values. Results: When comparing all patients with KD to healthy controls, we detected no significant difference in cIMR. None of the clinical parameters indicating the disease severity, such as the persistence of coronary artery aneurysm, were significantly associated with our cIMR values. However, according to our marginally significant findings (p = 0.044), we postulate that the end-diastolic cIMR may be rougher than the end-systolic values in KD patients. Conclusions: We detected no significant differences in cIMR between KD patients and controls that could confirm any evidence that KD predisposes patients to a subsequent general arteriopathy. Our results, however, need to be interpreted in the light of the low number of study participants.

Carotid Intima-media Thickness Measurements: Relations with Atherosclerosis, Risk of Cardiovascular Disease and Application in Randomized Controlled Trials

Advances in the field of carotid ultrasound have been incremental, resulting in a steady decrease in measurement variability. Improvements in edge detection algorithms point toward increasing automation of CIMT measurements. The major advantage of CIMT is that it is completely noninvasive and can be repeated as often as required. It provides a continuous measure since all subjects have a measurable carotid wall. It is also relatively inexpensive to perform, and the technology is widely available. A graded relation between raising LDL cholesterol and increased CIMT is apparent. Increased CIMT has been shown consistently to relate the atherosclerotic abnormalities elsewhere in the arterial system. Moreover, increased CIMT predicts future vascular events in both populations from Caucasian ancestry and those from Asian ancestry. Furthermore, lipid‑lowering therapy has been shown to affect CIMT progression within 12–18 months in properly designed trials with results congruent with clinical events trials. In conclusion, when one wants to evaluate the effect of a pharmaceutical intervention that is to be expected to beneficially affect atherosclerosis progression and to reduce CV event risk, the use of CIMT measurements over time is a valid, suitable, and evidence‑based choice.

Carotid intima-media thickness studies: study design and data analysis

BACKGROUND

Carotid intima-media thickness (CIMT) measurements have been widely used as primary endpoint in studies into the effects of new interventions as alternative for cardiovascular morbidity and mortality. There are no accepted standards on the use of CIMT measurements in intervention studies and choices in the design and analysis of a CIMT study are generally based on experience and expert opinion. In the present review, we provide an overview of the current evidence on several aspects in the design and analysis of a CIMT study on the early effects of new interventions.

SUMMARY OF ISSUES

A balanced evaluation of the carotid segments, carotid walls, and image view to be used as CIMT study endpoint; the reading method (manual or semi-automated and continuously or in batch) to be employed, the required sample size, and the frequency of ultrasound examinations is provided. We also discuss the preferred methods to analyse longitudinal CIMT data and address the possible impact of, and methods to deal with missing and biologically implausible CIMT values.

CONCLUSIONS

Linear mixed effects models are the preferred way to analyse CIMT data and do appropriately handle missing and biologically implausible CIMT values. Furthermore, we recommend to use extensive CIMT designs that measure CIMT at regular points during the multiple carotid sites as such approach is likely to increase the success rates of CIMT intervention studies designed to evaluate the effects of new interventions on atherosclerotic burden.

Biomarkers of subclinical atherosclerosis in patients with autoimmune disorders

Atherosclerosis is accelerated in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). We investigated a possible association of oxidized low-density lipoproteins (ox-LDLs), nitric oxide (NO), 3-nitrotyrosine, vitamin A, vitamin E, and β-carotene serum levels with subclinical atherosclerosis in RA and PsA. By the use of ELISA, we observed higher ox-LDL levels in patients with intima-media thickness (IMT) > 1 than in patients with IMT ≤ 1 and a negative correlation between NO levels and IMT values. By the use of high-performance liquid chromatography, we determined higher levels of vitamin A in patients with PsA and IMT ≤ 1 than in controls and lower levels of β-carotene in patients with RA and PsA than in controls. β-carotene concentrations were negatively correlated to the duration of disease in RA. Our study confirms that ox-LDLs and NO may be markers of accelerated atherosclerosis in RA and PsA whereas vitamins seem to be associated only to the presence of the autoimmune disorders.

Asymmetrical distribution of atherosclerosis in the carotid artery: identical patterns across age, race, and gender

BACKGROUND

Small autopsy studies and clinical practice indicated that carotid atherosclerosis develops in an asymmetrical helical pattern coinciding with regions of low shear stress. We investigated the distribution of carotid atherosclerosis as determined by maximum carotid intima-media thickness (CIMT), to assess if we could confirm this atherosclerotic configuration across various populations with different cardiovascular risk.

METHODS AND RESULTS

We used the individual baseline CIMT data from 3364 subjects from four recent international multicentre randomized controlled trials in which the carotid artery was systematically examined using the same ultrasound protocol and method to quantify CIMT. For each subject, circumferential information on the maximum CIMT of the left and right carotid arteries was obtained for the common carotid, bifurcation, and internal carotid artery segments. In each segment (common, bifurcation, internal), mixed modelling was used to study the differences in CIMT between angles, sides, gender, age, race, and studies. Each segment showed a different circumferential CIMT pattern. In all segments there were statistically significant differences between maximum CIMT across circumferential angles (p < 0.001); on average CIMT was highest in the posteromedial wall of the bifurcation and internal carotid segments and in the anterolateral wall of the common carotid segment. This asymmetric circumferential pattern was found to be identical in men and women, in young and old age, in different race groups, and across the studies.

CONCLUSIONS

We confirmed the asymmetrical helix-like distribution of atherosclerosis in the carotid arteries and expand the evidence by showing that the atherosclerotic configuration is similar across populations with different vascular risks and across gender, age, and race. This has implications for future design of carotid ultrasound studies, as the angle of insonation is an important predictor of maximum CIMT.

The adiponectin gene is associated with adiponectin levels but not with characteristics of the insulin resistance syndrome in healthy Caucasians

Low concentrations of adiponectin, the protein product of the APM1 gene, have been reported to be associated with obesity and insulin resistance. However, contrasting results have been described on the genetic variability in APM1 and characteristics of the metabolic syndrome and adiponectin serum concentrations. In the present study, we investigated the association of the two most well-known SNPs of APM1 (+45T>G and +276G>T) and their haplotypes, with serum adiponectin concentrations, metabolic parameters and intima-media thickness of the carotid arteries in 1,745 well-phenotyped asymptomatic unrelated Caucasian subjects of the SAPHIR cohort. The common T-allele (88.5%) of SNP +45T>G and the common G-allele (70.5%) of SNP +276G>T were associated with significantly lower serum adiponectin levels (P = 0.0008 and P = 0.00005, respectively). The most frequent haplotype TG (59.0%) defined by both loci showed a strong association with lower serum adiponectin concentrations (P = 0.000000002). A clear effect per copy of the respective haplotype was observed. This association was most pronounced in lean and insulin-sensitive subjects. The two less common haplotypes TT (29.5%) and GG (11.5%) were associated with higher serum adiponectin levels in a dose-dependent association. Interestingly, no significant association between the adiponectin 45-276 haplotypes and the majority of parameters of the metabolic syndrome or intima-media thickness of the carotid arteries was found in our study. In summary, we replicated a strong association of the adiponectin 45-276 genotypes and haplotypes with adiponectin levels in healthy Caucasians. However, we could not confirm an association of this gene locus with metabolic parameters of the insulin resistance syndrome.

Are Your Arteries Older Than Your Age?

PURPOSE

To determine the effect of age and atherosclerotic risk factors on the carotid intima-media layer thickness and morphology characteristics.

PATIENTS AND METHODS

Three groups of subjects were included in the study: Individuals with atherosclerotic risk factors including a family history of CHD, hypertension, hyperlipidemia, diabetes, and/or smoking (group A, n=180), age- and sex-matched healthy subjects without risk factors (group B, n=60) and a group of significantly younger volunteers (group C, n=25). The carotid artery was imaged longitudinally with B-mode ultrasound. Intima media thickness (IMT) was measured in the common (CCA) and internal carotid (ICA) arteries. Surface irregularity and continuity of the intima-media layer (IML) were assessed by high definition imaging. Echogenicity of the wall was quantified using Adobe Photoshop. The presence of calcium deposits was recorded. The double line wall pattern seen in young healthy people was used as a control to assess patterns and texture of the carotid IML. Fifteen subjects had their measurements repeated for intraobserver variability.

RESULTS

IMT measurements were reproducible in both the CCA and ICA (coefficient of variation 6% and 9%). IMT increased linearly with age (adjusted R(2)=0.72, p<0.0001), which was also an independent risk factor for increased IMT. All the risk factors had a significant association with increased IMT. In the lowest (third) decade the wall/blood interface was smooth and the double line was visualized with an echolucent center. With increased age and number of risk factors present, the wall/blood interface became more irregular (p<0.01), the double line was distorted (p<0.01) and the IML was more echogenic (p<0.01). The increase in IMT and the changes in the echogenicity of the IML were more pronounced in the ICA.

CONCLUSIONS

Age is an independent risk factor for increased IMT. Atherosclerotic risk factors are associated with the age-related changes seen in the IML. Such changes are also seen in younger asymptomatic volunteers with risk factors indicating that their arteries are older than their age.

Homocysteine and carotid intima-media thickness: a critical appraisal of the evidence

This review examines the relationship between hyperhomocysteinemia, a risk factor for vascular disease, and carotid intima-media thickness (CIMT), a valid marker of generalized atherosclerosis and future vascular disease risk. The relationship between two important determinants of hyperhomocysteinemia in the general population-folate status and the 677C --> T methylenetetrahydrofolate reductase (MTHFR) polymorphism-and CIMT is also covered.

METHODS

We searched literature databases for articles examining homocysteine and CIMT published before September 2003.

RESULTS

We identified 54 studies. Observational studies generally failed to demonstrate a relationship between homocysteine and CIMT in homocystinuric, uremic, hypercholesterolemic or non-insulin-dependent diabetes mellitus patients or in subjects with insulin insensitivity. Weak associations, but usually only in certain sub-populations were found in vascular disease patients and in population-based studies. B vitamins reduce the progression of CIMT in renal transplant recipients and vascular disease patients as demonstrated by two trials. The majority of studies demonstrated increased CIMT in individuals with the MTHFR 677TT genotype. Folate status showed no relation to CIMT.

DISCUSSION

In non-patient populations, hyperhomocysteinemia is weakly associated with CIMT. The association of the 677 C--> T MTHFR polymorphism with CIMT further supports this finding. Lastly, folate levels may need to reach a critically low status before an association can be found between folate and CIMT. Larger trials in various population types are needed to determine whether folate alone or in combination with Vitamins B6 and B12 will slow down or even reverse atherosclerotic progression.

Hypertension and subclinical carotid atherosclerosis in a suburban general population in China

OBJECTIVE

To explore the association of hypertension and carotid atherosclerosis in a general population in China.

METHODS

A population-based cardiovascular epidemiology survey was performed in a total of 1198 residents in suburban Beijing, 426 men and 776 women aged 43-73 years. Carotid plaque and the intima-media thickness were measured using duplex ultrasound.

RESULTS

The intima-media thickness, the prevalence of plaque and the number of plaques were found significantly positively related to hypertension categories (optimal, normal, high-normal, stage 1, 2 and 3 hypertension, according to The Chinese Hypertension Guidelines) as well as to the duration of hypertension, with a dose-response pattern in both genders (trend test, P < 0.01). After adjustment for age, total cholesterol, high-density lipoprotein-cholesterol, fasting glucose, smoking, antihypertensive treatment, stroke, myocardial infarction and angina, the relationship still existed, particularly in women. The associations of carotid atherosclerosis with duration of hypertension were weakened by further adjustment for systolic blood pressure, diastolic blood pressure or hypertension categories.

CONCLUSION

Hypertension was associated with subclinical carotid atherosclerosis. A prolonged course of the disease may aggravate the carotid atherosclerosis, independently of the level of blood pressure.

Quantitative measurement of carotid intima-media roughness--effect of age and manifest coronary artery disease

Atherosclerotic changes of the common carotid artery (CCA) may appear like irregularities of the intima-media thickness (abbreviated as IM roughness) in B-mode ultrasound. The purposes of the present study were to investigate whether the CCA IM roughness changes with age and differs between individuals presumed to be healthy and patients with coronary artery disease (CAD).

METHODS AND RESULTS

Based on a new automatic identification (AI) program, the segmental intima-media thickness (IMT) and IM roughness of the CCA far wall were measured in B-mode images of 15 younger and 22 older volunteers presumed to be healthy, and 46 patients with known CAD. The mean and maximum CCA IMT were lowest in the young group (0.55+/-0.05; 0.65+/-0.06 mm), higher in the older group (0.77+/-0.16; 0.87+/-0.18 mm) and highest in CAD patients (0.88+/-0.18; 1.01+/-0.27 mm) (P<0.01 among all groups). The CCA IM roughness was greatest by far in the CAD patients (0.075+/-0.02 mm; P<0.01 vs. both groups) and increased only slightly with age (younger: 0.035+/-0.008 mm; older: 0.040+/-0.014 mm; P<0.05). Areas under the curve (AUC) of receiver-operating characteristic curves (ROC) predicting patients with CAD were higher for the CCA IM roughness (0.80) than for the mean (0.66) and maximum IMT (0.71).

CONCLUSIONS

It is suggested that the CCA IM roughness increases with age, and helps to discriminate between individuals presumed to be healthy and patients with manifest CAD better than the CCA mean and maximum IMT.

Quantification of extracranial carotid artery stenosis by ultrafast three-dimensional ultrasound

This study was designed to evaluate the possible contribution of 3-dimensional (3D) ultrasound (US) for noninvasive detection of extracranial carotid artery stenosis. Sixty-nine stenotic lesions of extracranial carotid artery were studied by (1) B-mode (Bm) US, (2) Doppler spectral analysis, and (3) a prototype of 3D vascular system. When indicated (46 stenotic lesions), biplane carotid angiography (CA) was performed. The degree of luminal narrowing measured as percent area reduction in the 3D data set correlated well with the degree of stenosis estimated by CA (r = 0.79, P <.01, mean difference 7.8% +/- 15.5%); however, for stenosis between 40% and 70%, 3D US tended to give higher values. Compared with CA, the sensitivity, specificity, diagnostic accuracy, and positive predictive value of 3D US for significant (> or =70%) stenosis were 96.0%, 77.7%, 88.3%, and 85.7%, respectively. Thus, 3D US showed good sensitivity and diagnostic accuracy for detection of significant stenosis of extracranial carotid artery. For stenosis between 40% and 70%, 3D US indicated a higher degree than CA; this finding suggests that CA may underestimate the severity of stenosis due to known discrepancies between linear measurement and true anatomic situation.

High-normal serum homocysteine concentrations are associated with an increased risk of early atherosclerotic carotid artery wall lesions in healthy subjects

OBJECTIVE

Moderate hyperhomocysteinaemia is common in the general population and has been linked with systemic atherosclerotic vascular disease. We studied the relation of sonographically determined carotid intima-media wall thickness to serum homocysteine concentrations in asymptomatic, healthy subjects.

METHODS AND RESULTS

Seventy-five male and female untreated subjects (mean age 49 years, range 22-75) with normal serum folate concentrations were included. High-resolution duplex sonography was used to determine intima-media thickness of the common carotid artery. Serum homocysteine concentration was measured by high-performance liquid chromotography with fluorescence detection. Mean intima-media thickness (+/- SD) was 0.78 +/- 0.19 mm (range 0.5-1.35) and mean serum homocysteine concentration was 10.5 +/- 2.81 micromol/l (range 5.7-19.6). In stepwise regression models, statistically significant predictors of intima-media thickness included age, body mass index, LDL cholesterol and homocysteine (R2 = 0.51). Homocysteine concentration was independently associated with intima-media thickness after adjustment for the other variables (P < 0.001) and explained an additional 18% of the variation of intima-media thickness.

CONCLUSIONS

In healthy subjects, high-normal serum homocysteine concentrations are associated with an increased prevalence of carotid artery wall thickening. The significance of the contribution of homocysteine to the variation of carotid intima-media thickness, even at concentrations previously believed to be normal, suggests a role for homocysteine as an independent risk factor for early carotid artery atherosclerosis in the asymptomatic subjects.

Efficacy of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors for prevention of stroke

OBJECTIVE

To determine if 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are effective in preventing fatal and nonfatal strokes in patients at increased risk of coronary artery disease.

DESIGN

Meta-analysis of randomized controlled trials. Clinical trials were identified by a computerized search of MEDLINE (1983 to June 1996), by an assessment of the bibliographies of published studies, meta-analyses and reviews, and by contacting pharmaceutical companies that manufacture statins. Trials were included in the analysis if their patients were randomly allocated to a statin or placebo group, and reported data on stroke events. Thirteen of 28 clinical trials were selected for review. Data were extracted for details of study design, patient characteristics, interventions, duration of therapy, cholesterol measurements, and the number of fatal and nonfatal stroke events in each arm of therapy. Missing data on stroke events were obtained by contacting the investigators of the clinical trials.

MAIN RESULTS

Among 19,921 randomized patients, the rate of total stroke in the placebo group was 2.38% (90% nonfatal and 10% fatal). In contrast, patients who received statins had a 1.67% stroke rate. Using an exact stratified analysis, the pooled odds ratio (OR) for total stroke was 0.70 (95% confidence interval [CI] 0.57, 0.86; p =.0005). The pooled OR for nonfatal stroke was 0.64 (95% CI 0.51, 0.79; p =.00001), and the pooled OR for fatal stroke was 1.25 (95% CI 0.71, 2.24; p =.4973). In separate analyses, reductions in total and nonfatal stroke risk were found to be significant only for trials of secondary coronary disease prevention. Regression analysis showed no statistical association between the magnitude of cholesterol reduction and the relative risk for any stroke outcome.

CONCLUSIONS

The available evidence clearly shows that HMG-CoA reductase inhibitors reduce the morbidity associated with strokes in patients at increased risk of cardiac events. Data from 13 placebo-controlled trials suggest that on average one stroke is prevented for every 143 patients treated with statins over a 4-year period.

An in vivo evaluation of the reproducibility of intima-media thickness measurements of the carotid artery segments using B-mode ultrasound

B-mode ultrasound may be used to measure the intima-media thickness (IMT) in subjects with a history of atherosclerosis. The variability between measurements depends on the subjective interpretation of ultrasonographers and readers. The two carotid arteries, subdivided in common (CCA), bulbus (BUL) and internal (ICA) of 10 men with proven coronary disease, were scanned twice by two ultrasonographers with a 1-week interval. The IMTs were measured off-line by two readers. The number of IMT measurements was 75 (94%) of 80 in the CCA, 61 (76%) of 80 in the BUL and 43 (54%) of 80 in the ICA segment. In the CCA segment, the agreement between readers (mean = 0.02 mm; limits: -0.26 to +0.3 mm) and between visits for each reader separately (reader 1: mean = 0.01 mm; limits: -0.33 to +0.35 mm and, reader 2: mean = 0.04 mm; limits: -0.36 to +0.44 mm) was better than in the more distal segments. Therefore, it is concluded that IMT measurements are best performed in the CCA segment.

Ultrasound imaging for arterial wall thickness measurement: an in vitro study with stereomicroscopic correlation

Accuracy of B-mode ultrasonography was assessed in determining the arterial intima + media thicknesses at the near and far wall positions. From 10 human cadavers, 20 common carotid and 20 common femoral arteries were removed at autopsy and the intima + media thicknesses were measured with ultrasonography at the near and far wall locations and with stereomicroscopy. The differences between the locations were not statistically significant. The difference (mean +/- SD) between the stereomicroscopic and ultrasound measurements in the carotid artery was 0.12 +/- 0.09 mm at the near wall and 0.13 +/- 0.16 mm at the far wall and, in the femoral artery, 0.08 +/- 0.12 mm and 0.13 +/- 0.14 at the respective locations. At all locations, the stereomicroscope measurement was statistically significantly (p < 0.05) greater than the ultrasound measurement.

An in vitro evaluation of the line pattern of the near and far walls of carotid arteries using B-mode ultrasound

This in vitro study was executed to evaluate the double line pattern generated at both near and far walls of human carotid arteries using B-mode ultrasound. Therefore, extravascular (7.5 MHz) and intravascular (30 MHz) ultrasound imaging were performed at the same locations of the carotid artery. The thickness of the double line pattern of the extravascular image (7.5 MHz) was compared to the thickness of the intima-media complex seen on the corresponding intravascular image (30 MHz) and on the histologic section. At the far wall of the extravascular image, the measurements were executed at the leading edge of the echo. The data showed high correlation and agreement with the intravascular (r = 0.91, p < 0.001; mean(diff) = -0.01 and SDdiff = 0.12) and the histologic measurements (r = 0.87, p < 0.001; mean(diff) = -0.12 and SDdiff = 0.13). In addition, the results of the measurements of the intravascular image showed high correlations and agreement with the histologic data (r(near) = 0.86, p < 0.001; mean(diff) = -0.08 and SDdiff = 0.15, respectively, r(far) = 0.92, p < 0.001; mean(diff) = -0.12 and SDdiff = 0.12). For comparison with other studies, near wall measurements were also included. These had to be performed at the trailing edge of the echoes to be compatible with these studies. The results of the measurements of the extravascular image showed poor correlations and lack of agreement with those of the intravascular (r = 0.49, p = 0.03; mean(diff) = 0.09 and SDdiff = 0.25) and of the histologic (r = 0.37, p = 0.03; mean(diff) = 0.04 and SDdiff = 0.23) measurements. These results can easily be explained from the physical limitations of measuring at the trailing edges. We conclude that the double line pattern seen at the far wall of the extravascular image is representative of the intima-media complex.