Ultrasonic carotid artery plaque structure and the risk of cerebral infarction on computed tomography

Serum Urate Levels and Ultrasound Characteristics of Carotid Atherosclerosis across Obesity Phenotypes

BACKGROUND

Existing evidence suggests a close link among high levels of serum urate (SU), obesity and carotid atherosclerosis. The aim of the present study was to evaluate the interrelations between SU levels and carotid atherosclerosis in subjects with different obesity phenotypes.

METHODS

In this study, a total of 2076 subjects (mean age 48.1 ± 13.1 years; 1307 women) were recruited: 59 with general obesity, 616 with central obesity, 715 with mixed (general-central) obesity and 686 non-obese. Anthropometric measurements, vascular risk factors, blood biochemistry analysis (including SU levels), and carotid ultrasound were performed. Ultrasound assessment included evaluation of intima-media thickness (IMT) and plaque characteristics, including number, total area and type (vulnerable vs. stable) of plaques.

RESULTS

After adjustment for potential confounders, the highest levels of SU were observed in subjects with mixed obesity, followed by subjects with central obesity, general obesity and the non-obese (309.4 ± 82.2 vs. 301.2 ± 73.1 vs. 272.9 ± 61.8 vs. 234.2 ± 59.8 μmol/L, respectively; F = 149.2, post hoc p < 0.001). Similarly, subjects with mixed and central obesity presented higher values of IMT compared to subjects with general obesity and the non-obese (0.68 ± 0.16 vs. 0.67 ± 0.16 vs. 0.62 ± 0.14 vs. 0.57 ± 0.13 mm, respectively; F = 54.2, post hoc p < 0.001). No difference in number, total area and type of plaques among obesity groups were attested (all p > 0.05). Significantly higher IMT values were observed in subjects with increased SU levels compared to subjects with normal SU levels (0.70 ± 0.10 vs. 0.62 ± 0.14 mm, p = 0.02) only within the central obesity group. Increasing levels of SU were associated with a higher frequency of increased IMT only in subjects with central obesity (OR 1.033, 95% CI 1.025-1.041). Similarly, SU levels yielded a satisfactory performance in detecting subjects with increased IMT (AUC 0.65, 95% CI 0.50-0.73, subjects with carotid plaques (0.62, 95% CI 0.55-0.68) and subjects with vulnerable plaque types (0.68, 0.59-0.76) only within the central obesity group.

CONCLUSIONS

Among the studied obesity types, the association between SU levels and markers of carotid atherosclerosis was of particular significance in subjects with central obesity.

Brain imaging biomarkers of carotid artery disease

Extracranial carotid artery atherosclerotic disease is a major contributor to ischemic stroke. Carotid atherosclerotic disease can present with a spectrum of findings ranging from mild carotid intima-media thickness to high-risk vulnerable carotid plaque features and carotid stenosis. Before leading to clinically overt stroke or transient ischemic attack, there may be other markers of downstream ischemia secondary to carotid atherosclerotic disease. In this review article, we will review some of the imaging findings that may be seen downstream to carotid artery disease on various imaging modalities, including hemodynamic and perfusional abnormalities which may be seen on CT, MR, or using other advanced imaging techniques, white matter hyperintensities on brain imaging, silent or covert brain infarctions, cerebral microbleeds, and regional and generalized cerebral volume loss. Many of these imaging findings are seen routinely on brain magnetic resonance imaging in patients without overt clinical symptoms. Despite frequently being asymptomatic, many of these imaging findings are also strongly associated with increased risk of future stroke, cognitive impairment, and even mortality. We will review the existing evidence underpinning the associations between these frequently encountered imaging findings and carotid artery atherosclerotic disease. Future validation of these imaging findings could lead to them being powerful biomarkers of cerebrovascular health.

[Contribution of contrast enhanced ultrasonography in the characterization of carotid lesions]

Harmonic mode ultrasound with injection of a contrast enhancement agent allows visualization of mobile microbubbles in the carotid plaque corresponding to neovessels secondary to an inflammation or hypoxia. These neovessels could be considered "precursor" markers of the vulnerable plaque. The aim of this work was to give an update on ultrasound contrast imaging acquisition in the exploration of carotid artery both for atheromatous lesions and for large vessel vasculitis. A precise description of the material to be used, the image acquisition methodology and the environmental conditions is discussed, emphasizing the pitfalls to be avoided as well as proper image interpretation. Microbubbles in a plaque are significantly associated with an increase in cardiovascular events (infarction and acute coronary syndrome) and ipsilateral cerebral ischemic events. Wall irregularities, microfissures and ulcer plaque detection are facilitated by the use of contrast compared to the CT scan. No studies have yet validated contrast enhanced ultrasound in the exploration of asymptomatic carotid stenosis. Contrast enhanced ultrasound also allows to detect vasculitis of the large vessels active phases by the presence of microbubbles in the carotid wall thickening and to monitor the regression under appropriate medical treatment. Future validation studies or even registries are needed to allow better use of this tool in everyday clinical practice.

Plasma levels of vasostatin-1, a chromogranin A fragment, are associated with carotid artery maximum stenosis: A pilot study

BACKGROUND

Chromogranin A (CgA), a circulating protein released by the neuroendocrine system, can regulate vascular physiology and angiogenesis. Full-length CgA (CgA_1-439) and its fragment CgA_1-76 (called vasostatin-1, VS-1) preserve the physiological integrity of the endothelial barrier function and are antiangiogenic, whereas CgA_1-373 is proangiogenic. We investigated whether these polypeptides are altered in patients with various degrees of carotid artery atherosclerosis.

METHODS

We studied 81 patients with carotid artery atherosclerosis, asymptomatic for cerebrovascular diseases. Carotid arteries were examined by Doppler ultrasound and plaque characteristics were recorded. Plasma levels of CgA_1-439, VS-1, CgA_1-373, and total-CgA (CgA_1-439 plus truncated fragments lacking part or the entire C-terminal region) were assessed by specific ELISAs.

RESULTS

Plasma levels of VS-1 and total-CgA correlated with carotid artery maximum stenosis (r=0.349, p=0.001 and r=0.256, p=0.021, respectively). Stepwise multiple regression analysis indicated that VS-1 was a significant predictor of maximum stenosis after adjustment for age, gender, and conventional risk factors for atherosclerosis (regression coefficient=12.42, SE=4.84, p=0.012). In addition, logistic regression analysis indicated that relatively high levels of full-length CgA, but not total-CgA, predict the presence of hypoechoic, lipid-rich plaques (OR=1.47; 95% CI: 1.19-1.81, p=0.0003).

CONCLUSION

VS-1 is independently associated with carotid artery maximum stenosis. Furthermore, full-length CgA is an independent indicator of hypoechoic plaques, likely reflecting initial stages of atherosclerosis. Given the known capability of CgA and VS-1 to regulate vascular function and angiogenesis these polypeptides might play a role in the regulation of atherosclerosis pathophysiology.

Contrast-enhanced ultrasound imaging of intraplaque neovascularization and its correlation to plaque echogenicity in human carotid arteries atherosclerosis

BACKGROUND

Currently the most widely accepted predictor of stroke risk in patients with carotid atherosclerosis is the degree of stenoses. Plaque echogenicity on ultrasound imaging (US) and intraplaque neovascularization (IPNV) are becoming recognized as factors of plaque vulnerability. Aim of the study was to investigate the correlation between the echogenicity of the carotid atherosclerosis by standard US and the degree of IPNV by contrast enhanced US (CEUS).

METHODS

We recruited 45 consecutive subjects with an asymptomatic ≥50% carotid artery stenoses. Carotid plaque echogenicity at standard US was visually graded according to Gray-Weale classification (GW) and measured by the grayscale median (GSM), a semi-automated measurement performed by Adobe Photoshop©. On CEUS imaging IPNV was graded by different point scales according to the visual appearance of contrast within the plaque as follows: CEUS_A (1=absent; 2=present); CEUS_B (increasing IPNV from 1 to 3); and CEUS_C (increasing IPNV from 0 to 3).

RESULTS

The correlation between echogenicity by GW and IPNV grading was as follows: CEUS_B (-0.130 p .423), CEUS_C (-0.108, p .509), CEUS_A (0.021, p .897). The correlation between echogenicity by GSM measurement and IPNV was as follows: using a CEUS_A (-0.125, p .444), CEUS_C (-0.021, p .897) (0.005, p .977). No correlation was found statistically significant.

CONCLUSION

Our results display that there is no significant correlation between plaque echogenicity and IPNV. The small sample number and the multifaceted pathophysiology of the atherosclerotic plaque may explain the absence of statistically significantly correlation. Curtailing vulnerability explanation to either IPNV or echolucency may be misleading.

Orosomucoid, Carotid Plaque, and Incidence of Stroke

Background and Purpose—

Orosomucoid (α-1-acid glycoprotein) is an acute-phase protein that has been implicated in anti-inflammatory, immunomodulating, and angiogenic pathways. Orosomucoid has also been associated with coronary disease and stroke. The relationship between orosomucoid, carotid plaque, and stroke incidence were explored in this study.

Methods—

Plasma levels of orosomucoid were assessed in 4285 subjects (39.8% men; mean age 57.5±5.9 years) without cardiovascular disease, who participated in the Malmö Diet and Cancer Study, between 1991 and 1994. The right carotid artery was examined for plaque using B-mode ultrasound examination. Incidence of stroke was followed up during a median follow-up time of 17.7 years.

Results—

Carotid plaque was present in 43.5% at baseline. Orosomucoid was significantly higher in subjects with carotid plaque (mean±SD: 0.72±0.22 versus 0.69±0.20 g/L; P <0.001). A total of 234 subjects were diagnosed with ischemic stroke during follow-up. Orosomucoid was associated with ischemic stroke after adjustment for risk factors, with hazard ratio 1.48 (95% confidence interval, 1.02–2.16) comparing the third versus first tertile. In subjects with plaque and belonging to the top tertile of orosomucoid, the hazard ratio was 2.07 (95% confidence interval, 1.38–3.11) compared with those without plaque and with orosomucoid in the first and second tertiles, after adjustment for C-reactive protein and other risk factors.

Conclusions—

Elevated levels of orosomucoid are associated with increased occurrence of carotid plaque and increased incidence of ischemic stroke. The combination of high orosomucoid and carotid plaque substantially increase the risk of stroke.

Vascular imaging: ultrasound

The complexity of current stroke treatments requires detailed vascular imaging information. Vascular imaging using ultrasound is a safe, inexpensive, and portable technique that provides continuous real-time hemodynamic information, which allows flow changes to be monitored over prolonged time. Ultrasound imaging is in continuous development, which has led to a growing number of situations where ultrasound can be helpful, foremost in dynamic and rapidly changing clinical scenarios like acute stroke. The aim of this chapter is to review the main indications of vascular ultrasound in acute stroke, including extracranial steno-occlusive lesions diagnosis and its consequences on distal vasculature, intracranial stenosis diagnosis, acute intracranial occlusion, recanalization, and reocclusion diagnosis and monitoring, therapeutic sonothrombolysis, and vasospasm after subarachnoid hemorrhage.

Echolucency of carotid plaques and cerebrovascular events

OBJECTIVES

To assess the relationship between carotid plaque echogenicity and degree of stenosis with acute and chronic stroke.

METHODS

A retrospective study of cerebral MRI and carotid B-mode and Doppler ultrasonography in 60 patients with stroke. Plaque echogenicity was graded as echolucent (1), predominantly echolucent (2), predominantly echogenic (3), or echogenic (4). Sonographic findings were compared between patients with acute (group 1) and chronic (group 2) stroke.

RESULTS

In group 1 (n = 39 patients), the carotid plaques were grade 1 in 21, grade 2 in 22, grade 3 in 9, and grade 4 in 4 carotid arteries. In group 2 (n = 21), the carotid plaques were grade 1 in 2, grade 2 in 8, grade 3 in 4, and grade 4 in 11 carotid arteries. Plaque echogenicity was lower in group 1 than in group 2 (p < 0.05). Plaque echolucency was associated independently with acute stroke from the degree of stenosis.

CONCLUSIONS

Patients with acute infarcts have predominantly echolucent plaques, regardless of the degree of stenosis.

Plaque features associated with increased cerebral infarction after minor stroke and TIA: a prospective, case-control, 3-T carotid artery MR imaging study

OBJECTIVES

The goal of this study was to determine whether a 3-T magnetic resonance imaging (MRI) protocol combining carotid atherosclerotic plaque and brain imaging can identify features of high-risk acutely symptomatic plaque that correlate with brain injury.

BACKGROUND

It has previously been demonstrated that, in asymptomatic patients, MRI can identify features of carotid plaque that are associated with stroke, such as the presence of a large lipid core. We hypothesized that the early phase (<7 days) after a cerebrovascular event, when risk of recurrence is highest, may be associated with particular plaque characteristics that associate with cerebral injury.

METHODS

Eighty-one patients (41 presenting acutely with transient ischemic attack [TIA] or minor stroke and 40 asymptomatic controls) underwent multicontrast carotid artery MRI on 2 separate occasions, each accompanied by diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) imaging of the brain.

RESULTS

Complex (American Heart Association [AHA] type VI) plaques were seen in 22 of 41 patients (54%) in the symptomatic group versus 8 of 40 (20%) in the asymptomatic group (p < 0.05). They were caused by intraplaque hemorrhage (34% vs. 18%; p = 0.08), surface rupture (24% vs. 5%; p = 0.03), or luminal thrombus (7% vs. 0%; p = 0.24). Noticeably, 17 of 30 (57%) cases of AHA type VI plaque were in vessels with <70% stenosis. At follow-up scanning (>6 weeks later), only 2 cases of symptomatic AHA type VI plaque showed evidence of full healing. The presence of fibrous cap rupture was associated with higher DWI brain injury at presentation and higher total cerebral FLAIR signal at follow-up (p < 0.05).

CONCLUSIONS

Early carotid wall MRI in patients experiencing minor stroke or TIA showed a higher proportion of "complex" plaques compared with asymptomatic controls; a majority were in arteries of <70% stenosis. Fibrous cap rupture was associated with increases in DWI and FLAIR lesions in the brain. Combined carotid plaque and brain MRI may aid risk stratification and treatment selection in acute stroke and TIA.

EVALUATION OF THE RISK OF STROKE WITH CONFIDENCE PREDICTIONS BASED ON ULTRASOUND CAROTID IMAGE ANALYSIS

Conformal Predictors (CPs) are Machine Learning algorithms that can provide reliable confidence measures to their predictions. In this work, we make use of the Conformal Prediction framework for the assessment of stroke risk based on ultrasound images of atherosclerotic carotid plaques. For this application, images were recorded from 137 asymptomatic and 137 symptomatic plaques (symptoms are Stroke, Transient Ischaemic Attack (TIA), and Amaurosis Fugax (AF)). Two feature sets were extracted from the plaques; the first based on morphological image analysis and the second based on image texture analysis. Both sets were used in order to evaluate the performance of CPs on this problem. Four CPs were constructed using four popular classification methods, namely Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Naive Bayes Classification (NBC), and k -Nearest Neighbours. The results given by all CPs demonstrate the reliability and importance of the obtained confidence measures on the problem of stroke risk assessment.

Snoring and severity of symptomatic and asymptomatic carotid stenosis: a population-based study

BACKGROUND

Obstructive sleep apnea has increasingly been linked to cardiovascular damage. More recently, the snoring component itself has been independently linked to the presence of carotid atheroma, via local arterial trauma. We aimed to identify whether a snoring history is a risk factor for carotid stenosis in individuals presenting with a TIA or ischemic stroke.

METHODS

Participants in the Oxford Vascular Study (OXVASC) were asked about their snoring history as part of an entry questionnaire. In 561 individuals with a recent TIA or stroke, who had both a complete snoring questionnaire and carotid imaging, the relationship between presence and severity of snoring and the degree of carotid artery stenosis in both the symptomatic (culprit) and asymptomatic (non-culprit) sides.

RESULTS

Of 561 participants (287 male, mean/SD age = 73.3/11.0 years), 90 (16.0%) had ≥ 50% carotid stenosis, and 154 (27.5%) snored frequently (≥ 1-2 times/week). No significant associations were identified between frequency of self-reported snoring, and the degree of culprit and non-culprit carotid vessel stenosis, or plaque morphology.

CONCLUSIONS

No significant association could be identified between a history of frequent snoring and the presence of carotid atheroma, degree of stenosis, or plaque type.

Urgent Carotid Surgery: Is It Still out of Debate?

Patients with symptomatic tight carotid stenosis have an increased short-time risk of stroke and an increased long-term risk of ischaemic vascular events compared with the general population. The aim of this study is to assess the safety, efficacy, and limitations of urgent CEA or CAS, in patients with carotid stenosis greater than 70% and clinically characterized by recurrent TIA or brain damage following a stroke (<2.5 cm). This study involved 28 patients divided into two groups. Group A consisted of sixteen patients who had undergone CEA, and group B consisted of twelve patients who had undergone CAS. Primary endpoints were mortality, neurological morbidity (by NIHSS) and postoperative hemorrhagic cerebral conversion, at 30 days. Ten patients (62.5%) of group A experienced an improvement in their initial neurological deficit while in 4 cases (26%) the deficit remained stable. Two cases of neurologic mortality are presented. At 1 month, 9 patients (75%) of group B experienced an improvement in their initial neurological deficit while 3 patients (25%) had a neurological impairment. Urgent or deferred surgical or endovascular treatment have a satisfactory outcome considering the profile in very high-risk patient population. Otherwise in selected patients CEA seems to be preferred to CAS.

[Filter content after carotid angioplasty and stenting: relation to ischemic lesions in diffusion-weighted imaging]

OBJECTIVES

To evaluate the relation between the material retrieved from distal filters after carotid angioplasty and stenting and the development of ischemic brain lesions in diffusion-weighted imaging (DWI). To determine the influence of demographic, clinical, and procedural variables in the pathogenesis of emboli and in ischemia after carotid angioplasty and stenting.

MATERIAL AND METHODS

We submitted the contents of the filters of 76 patients (60 men; mean age, 68.39 years; range, 46-82) who had undergone angioplasty and stenting for severe stenosis of the internal carotid artery for histologic analysis evaluating volume (< 1 λ = 0.001 ml = 1 μl; 1-10 λ; and > 10 λ) and the composition of the particles. All patients underwent DWI before and 24 hours after the procedure; we recorded whether lesions appeared and their number, size, and distribution. We correlated the findings with demographic, clinical, and procedural variables.

RESULTS

Symptoms were present before the procedure in 58 (76.3%) patients. Particles were present in 49 (64.5%) of the filters; most particles (77.5%) were 1 λ with a predominance of fibrin-platelet aggregates, cell remnants, and cholesterol crystals. DWI after the procedure detected lesions in 12 (15.8%) patients. We found no statistically significant correlation between filter contents and lesion detection after the procedure or between filter contents and other variables.

CONCLUSIONS

Ischemia after carotid angioplasty and stenting does not depend solely on the embolic load and its nature. We consider that the lower prevalence of postprocedural lesions in our series compared to others suggests that appropriate patient selection and experience minimize the negative influence of some variables like age in their development.

A review of noninvasive ultrasound image processing methods in the analysis of carotid plaque morphology for the assessment of stroke risk

Noninvasive ultrasound imaging of carotid plaques allows for the development of plaque-image analysis methods associated with the risk of stroke. This paper presents several plaque-image analysis methods that have been developed over the past years. The paper begins with a review of clinical methods for visual classification that have led to standardized methods for image acquisition, describes methods for image segmentation and denoising, and provides an overview of the several texture-feature extraction and classification methods that have been applied. We provide a summary of emerging trends in 3-D imaging methods and plaque-motion analysis. Finally, we provide a discussion of the emerging trends and future directions in our concluding remarks.

Is high-resolution magnetic resonance imaging or ultrasonography better for prediction of clinical events induced by carotid vulnerable lesions?

OBJECTIVE

To find a better way to predict the clinical events caused by carotid vulnerable lesions via comparison study on high-resolution magnetic resonance imaging (MRI) and ultrasonography (US).

METHODS

Twenty-seven symptomatic stroke patients were recruited, all of which were given both high-resolution MRI and US at bilateral carotids. Respective correlations of high-resolution MRI and US outcomes with clinical events were performed and the lesion numbers identified by high-resolution MRI and US were statistically analysed.

RESULTS

Six carotid arteries in six patients were excluded because of uninterpretable high-resolution MRI findings or patients' intolerance. In the remaining 48 carotids analysed, the number of carotid with vulnerable/stable lesion was 17/31 by high-resolution MRI and 25/23 by US, respectively. Contingency coefficient was 0.40 between vulnerable lesion by high-resolution MRI and clinical event (p=0.004), and 0.19 (p=0.221) by US and clinical event, respectively. The difference of detected lesion numbers between high-resolution MRI and US was statistically significant p=0.039) through matched chi-square test.

CONCLUSION

High-resolution MRI may be a better way than US in predicting the clinical events caused by carotid vulnerable lesions.

The use of Speckle Reduction Imaging (SRI) Ultrasound in the characterization of carotid artery plaques

BACKGROUND AND PURPOSE

Speckle Reduction Imaging is a new algorithm that improves the image quality of B-mode scanning by reducing the reverberation artifacts. In the present study the value of this method for the characterization of atherosclerotic plaques in the internal carotid artery was investigated.

METHODS

Two hundred and twenty two patients (161 men, 61 women; mean age 73 years) referred for carotid ultrasound evaluation were included in the study. Patients with plaques of the internal carotid artery as identified by conventional B-mode scanning were investigated also with the addition of Speckle Reduction Imaging (SRI) with the use of a 4-11-MHz wide band linear transducer. Plaque morphology was rated according to a standardized protocol by two independent observers.

RESULTS

For the determination of plaque echogenicity, the reproducibility of SRI (kappa=0.83) was higher than that of conventional B-mode ultrasound (kappa=0.68). The interobserver agreement for plaque surface characterization was also higher for SRI (kappa=0.8) than for conventional B-mode (kappa=0.61). At the evaluation of the image quality through a semiquantitative analysis, SRI was rated superior in the plaque texture resolution, plaque borders determination, vessel wall demarcation and fibrous cap depiction. In addition, the level of "speckle" was reduced with the use of SRI.

CONCLUSIONS

SRI is a technique that shows good general agreement with high-resolution B-mode and can be used for the characterization of atherosclerotic plaques in the carotid artery. Furthermore, because this advanced technique allows reduction of ultrasound artifacts, it improves the image quality allowing more precise visualization of plaque morphological details.

Texture Analysis of Ultrasonic Images of Symptomatic Carotid Plaques can Identify Those Plaques Associated with Ipsilateral Embolic Brain Infarction

OBJECTIVES

The aim of our study was to determine the association between objective, computerised texture analysis of carotid plaque ultrasonic images and embolic CT-brain infarction in patients presenting with hemispheric neurological symptoms.

DESIGN

Cross-sectional study in patients with 50%-99% (ECST) carotid stenosis.

PATIENTS AND METHODS

Carotid plaque ultrasonic images (n=54, 26 with TIAs and 28 with stroke) obtained during carotid ultrasound were normalised and standardised for resolution and subsequently assessed visually for the presence of discrete echogenic or juxtaluminal echolucent components and overall echogenicity (plaque type). Using computer software, 51 histogram/textural features of the plaque outlines were calculated. Factor analysis was subsequently applied to eliminate redundant variables. Small cortical, large cortical and discrete subcortical infarcts on CT-brain scan were considered as being embolic.

RESULTS

Twenty-five cases (46%) had embolic infarcts. On logistic regression, grey-scale median (GSM), a measure of echolucency, spatial grey level dependence matrices (SGLDM) correlation and SGLDM information measure of correlation-1, measures of homogeneity were significant (p<0.05), but not grey level runlength statistics (RUNL) Run Percentage (RP), stenosis severity, type of symptoms or echolucent juxtaluminal components. Using ROC curves methodology, SGLDM information measure of correlation-1 improved the value of GSM in distinguishing embolic from non-embolic CT-brain infarction.

CONCLUSION

Computerised texture analysis of ultrasonic images of symptomatic carotid plaques can identify those that are associated with brain infarction, improving the results achieved by GSM alone. This methodology could be applied to prospective natural history studies of symptomatic patients not operated on or randomised trials of patients undergoing carotid angioplasty and stenting in order to identify high-risk subgroups for cerebral infarction.

Asymptomatic Carotid Artery Stenosis: Past, Present and Future

BACKGROUND

The role of carotid endarterectomy (CEA) for asymptomatic carotid artery stenosis (aCAS) remains a matter of debate. It seems that not only the degree of stenosis, but also other factors have to be taken in account to improve patient selection and increase the benefit of CEA for aCAS.

METHODS AND RESULTS

The literature pertaining aCAS was reviewed in order to describe the natural history, risk of stroke and benefit of CEA for patients with aCAS in regard to several factors.

CONCLUSION

The benefit of CEA for aCAS is low. Current factors influencing the indication for CEA are severity of stenosis, age, contralateral disease, stenosis progression to >80%, gender, concomitant operations and life expectancy. To improve patient selection investigations will concentrate on plaque characteristics and instability and cerebral hemodynamics and metabolism.

Repeated visual and computer-assisted carotid plaque characterization in a longitudinal population-based ultrasound study: the Tromsø study

In a longitudinal population-based ultrasound survey, we evaluated the reproducibility of carotid plaque detection, off-line vs. online visual classification of plaque echogenicity and computer-assisted plaque echogenicity (grey-scale median, GSM) classification and plaque area measurements. The number of paired observations in the reproducibility analyses was 107 in the baseline study and 83 in the follow-up study. In addition, 198 and 222 images were selected from the baseline and the follow-up study for GSM- and plaque-area analyses. The total number of plaque images (11,160) was used to obtain comparative reference values. Despite good agreement in the reproducibility study (kappa values ranging from 0.52 to 0.57), there was a substantial drift in online visual classification of plaque echogenicity during the survey period. Inter- and intraobserver agreement on computer-assisted GSM classification was substantial, with kappa values (95% CI) of 0.77 (0.73 to 0.80) and 0.79 (0.75 to 0.84), respectively. A systematic bias in plaque area measurements was observed. Visual online classification may introduce systematic measurement errors that are not intercepted in a reproducibility study of restricted duration. Computer-assisted off-line classification had better reproducibility. However, the method is influenced by measurement errors, both in the outlining of the plaque and in the standardization procedure.

B-mode ultrasonographic characterization of carotid atherosclerotic plaques in symptomatic and asymptomatic patients

OBJECTIVE

To identify features on B-mode ultrasonography (US) prevalent in symptomatic plaques and correlate these findings with histopathologic markers of plaque instability.

METHODS

Carotid endarterectomy (CEA) plaques from symptomatic and asymptomatic patients with critical stenoses (>70%) were qualitatively assessed using preoperative B-mode US for echolucency and calcific acoustic shadowing. US echolucency was quantitated ex vivo using computerized techniques for gray-scale median (GSM) analysis. Histopathologic correlates for US plaque echolucency (percentage of necrotic core area) and acoustic shadowing (percentage of calcification area) were determined.

RESULTS

Fifty CEA plaques were collected from 48 patients (46 unilateral and two bilateral); 26 of these plaques were from symptomatic patients. Age, degree of stenosis, and atherosclerotic risk factors were similar for the symptomatic and asymptomatic patients. Using preoperative B-mode US, 58%, 35%, and 7% of symptomatic plaques and 18%, 41%, and 41% of asymptomatic plaques were found to be echolucent, echogenic, and calcific, respectively (P < .05). Using ex-vivo B-mode US and GSM analysis, symptomatic plaques were more echolucent (41 +/- 19) than asymptomatic plaques (60 +/- 13), P < .03. A strong inverse correlation was found between the percent plaque necrotic area core and GSM (R = -0.9, P < .001). Percentage of calcification area in plaques with acoustic shadowing was 66% and only 27% in those without acoustic shadowing (P < .05).

CONCLUSIONS

Using B-mode US, symptomatic plaques are more echolucent and less calcified than asymptomatic plaques and are associated with a greater degree of histopathologic plaque necrosis. Such features are indicative of plaque instability and should be considered in the decision-making algorithm when selecting patients with high-grade asymptomatic carotid stenosis for intervention.

Incidence of stroke is related to carotid IMT even in the absence of plaque

BACKGROUND

The carotid intima-media thickness (IMT) has been associated with incidence of stroke. Whether this association is independent of carotid plaque is controversial.

METHODS AND RESULTS

The associations among B-mode ultrasound determined common carotid IMT, carotid plaque (focal IMT>1.2mm) and incident stroke, were investigated in 5163 Swedish middle-aged men and women over a median follow-up of 7 years. Age and sex-adjusted carotid IMT, and carotid plaque were significantly (p<0.05) related to future stroke. Adjustment for cardiovascular risk factors generally reduced the hazard rate ratios, however more prominently so with regard to the carotid measure of plaque than with IMT. The associations between carotid IMT and stroke remained after adjustment for presence of carotid plaque, and graded associations between carotid IMT and stroke was found both among those with and without carotid plaque.

CONCLUSIONS

In this population-based study, common carotid IMT was associated with incidence of stroke. This relation was independent of presence of carotid plaque.

Development and validation of an in vivo analysis tool to identify changes in carotid plaque tissue types in serial 3-D ultrasound scans

We have developed a three-dimensional (3-D) B-mode acquisition system suitable for imaging carotid plaques in vivo. A texture classification system using 157 statistical and textural algorithms, previously developed in our laboratory and shown to predict the contents of in vitro carotid plaques, was applied to in vivo 3-D image sets obtained from patients with both symptomatic and asymptomatic carotid artery plaques. Delineation of plaque boundaries is more difficult using in vivo images than in vitro images of excised plaques embedded in agar. This study has examined inter- and intraobserver variability studies to assess the degree of selectivity of the plaque region-of-interest (ROI) and assess the degree of repeatability for potential use in comparing serial scans. An interobserver limit of agreement of +/-12.9% and an intraobserver limit of repeatability of <2% were obtained. These results show that the plaque ROI selection is subjective, but is repeatable within acceptable limits.

Degree of carotid plaque calcification in relation to symptomatic outcome and plaque inflammation

OBJECTIVE

We undertook this study to quantitate differences in the degree of calcification between symptomatic and asymptomatic plaques removed at carotid endarterectomy (CEA) and to determine associated extent of plaque macrophage infiltration, a histopathologic feature of plaque instability.

METHODS

CEA plaques (n = 48) were imaged at 1.25-mm intervals with spiral computed tomography (CT; 10-15 images per plaque). Indications for CEA were transient ischemic attack (n = 16), stroke (n = 5), amaurosis (n = 4), and critical asymptomatic stenosis (n = 23). The percent area calcification for each plaque was determined in spiral CT serial sections and averaged for each plaque. In 31 of 48 plaques macrophage infiltration was quantitated in corresponding histologic sections with immunohistochemical techniques.

RESULTS

The mean (+/- SD) age of patients with symptomatic and asymptomatic plaques was 66 +/- 7 years vs 71 +/- 7 years, respectively, and degree of stenosis was 76% versus 82%, respectively (P =.05). Atherosclerosis risk factors were similar between groups. Percent plaque area calcification was twofold greater in asymptomatic versus symptomatic plaques (48% +/- 19% vs 24% +/- 20%, respectively; P <.05). At receiver operating characteristic curve analysis, 80% of symptomatic plaques were below and 87% of asymptomatic plaques were above a cutoff point of 30% plaque area calcification. Macrophage burden was greater in the symptomatic plaques than in the asymptomatic plaques (52% vs 23%; P <.03). A strong inverse relationship between the degree of plaque calcification and macrophage infiltration was found in critical carotid stenoses (r = -0.87; P <.001).

CONCLUSIONS

Symptomatic plaques are less calcified and more inflamed than asymptomatic plaques. Regardless of clinical outcome, a strong inverse correlation was found between the extent of carotid plaque calcification and the intensity of plaque fibrous cap inflammation as determined by the degree of macrophage infiltration. Carotid plaque calcification is associated with plaque stability, and is a potential spiral CT in vivo quantitative marker for cerebrovascular ischemic event risk.

The Evidence Thing

The methodology of evidence-based medicine (EBM) has become dominant in the clinical field to the detriment of historically validated paradigms. The philosophical background of EBM is considered and the strengths and flaws of its main tools (randomized trials and meta-analysis) are reviewed. The structural format of EBM speaks the language of regulators and health planners, satisfies the needs of the academic-industrial complex, and is favored by editors of medical journals. Specific problems of trials of medical versus surgical therapy are noted. The deductive-numerical approach of EBM is a methodology geared to ascertain the most effective management of a condition when the differences observed between the two entities being considered is small. EBM methodology is unlikely to lead to discovery of new diseases or treatments; the latter derive from alert observation and inductive inference. While its contribution to the rigorous analysis of effectiveness of some therapies is acknowledged, EBM is not the nostrum of clinical research. Observational and inductive clinical intelligence should be stimulated and published because a therapy needs to be invented before it is proven effective. Biomathematicians need to improve nonrandomized methodology as they did for randomized studies.

Texture-based classification of atherosclerotic carotid plaques

There are indications that the morphology of atherosclerotic carotid plaques, obtained by high-resolution ultrasound imaging, has prognostic implications. The objective of this study was to develop a computer-aided system that will facilitate the characterization of carotid plaques for the identification of individuals with asymptomatic carotid stenosis at risk of stroke. A total of 230 plaque images were collected which were classified into two types: symptomatic because of ipsilateral hemispheric symptoms, or asymptomatic because they were not connected with ipsilateral hemispheric events. Ten different texture feature sets were extracted from the manually segmented plaque images using the following algorithms: first-order statistics, spatial gray level dependence matrices, gray level difference statistics, neighborhood gray tone difference matrix, statistical feature matrix, Laws texture energy measures, fractal dimension texture analysis, Fourier power spectrum and shape parameters. For the classification task a modular neural network composed of self-organizing map (SOM) classifiers, and combining techniques based on a confidence measure were used. Combining the classification results of the ten SOM classifiers inputted with the ten feature sets improved the classification rate of the individual classifiers, reaching an average diagnostic yield (DY) of 73.1%. The same modular system was implemented using the statistical k-nearest neighbor (KNN) classifier. The combined DY for the KNN system was 68.8%. The results of this paper show that it is possible to identify a group of patients at risk of stroke based on texture features extracted from ultrasound images of carotid plaques. This group of patients may benefit from a carotid endarterectomy whereas other patients may be spared from an unnecessary operation.

Evaluation of B-mode ultrasonographic images of carotid lesions by computer analysis as compared with visual assessment

To establish an objective method for evaluating the characteristics of carotid artery lesions by B-mode ultrasonography, we compared the reproducibility of computer analysis with that of visual evaluation. Using two different models of ultrasonograph, we evaluated B-mode ultrasonographic images of 100 carotid artery lesions in a blinded fashion by computer analysis and visual evaluation, two times at a 1-month interval. Another 35 lesions were simultaneously imaged by the two models of ultrasonograph and were evaluated visually and by computer analysis to examine the correlation between results. For visual evaluation, carotid artery lesions were divided into the following 3 types based on texture and relative echogenicity as compared with that of adjacent muscle tissue: heterogeneous, hypoechoic, and hyperechoic. For computer analysis, images were computerized by means of a scanner (using Adobe Photoshop software). The echogenicity of all pixels included in the lesion and adjacent areas of muscular tissue was measured, and the lesion was classified into the following 3 types based on the shape of histograms of echogenicity: mixed-echoic (M), hyperechoic (H), and lucent (L). The reproducibility of the results derived by computer analysis had a significantly higher coincidence coefficient (kappa = 0.89) than those derived by visual evaluation (kappa =0.68). The coincidence coefficient (kappa) of the same lesions depicted by two different models of equipment was 0.77 for computer analysis as compared with only 0.32 for visual evaluation. These findings indicate that computer analysis of histogram shape and lesion echogenicity can improve intra-sonographer and inter-equipment reproducibility in the evaluation of lesion echogenicity and texture.

Carotid plaque ultrasonic heterogeneity and severity of stenosis

BACKGROUND AND PURPOSE

Several studies have reported on the correlation of ultrasonic carotid plaque morphology, cerebrovascular symptoms, and intraplaque hemorrhage. This study correlates ultrasonic carotid plaque morphology with the degree of carotid stenosis.

METHODS

Carotid arteries (n=2460) were examined by using color duplex ultrasound during a 1-year period. Carotid stenoses were classified into <50%, 50% to <60%, 60% to <70%, and >70% to 99%. Ultrasonic plaque morphology was characterized as either heterogeneous (mixed hyperechoic, hypoechoic, and isoechoic) or homogeneous.

RESULTS

Heterogeneous plaques were noted in 138 of 794 arteries with <50% stenosis, in 191 of 564 arteries with 50% to <60% stenosis, in 301 of 487 arteries with 60% to <70% stenosis, and in 496 of 615 arteries with 70% to 99% stenosis. The higher the degree of stenosis, the more likely it is to be associated with heterogeneous plaques. Heterogeneous plaques were present in 59% of the arteries with > or =50% stenoses versus 17% of the arteries with <50% stenoses, in 72% of the arteries with > or =60% stenoses versus 24% of the arteries with <60% stenosis, and in 80% of the arteries with > or =70% stenoses versus 34% of the arteries with <70% stenoses (P<0.0001 and odds ratios of 6.9, 8.1, and 8.0, respectively). Heterogeneous plaques were associated with an incidence of symptoms that was higher than that for homogeneous plaques for all grades of stenoses; percentages were, respectively, as follows: 68% versus 16% for <50% stenosis; 76% versus 21% for 50% to <60% stenosis; 79% versus 23% for 60% to <70% stenosis, and 86% versus 31% for > or =70% to 99% stenosis (P<0.0001 and odds ratios of 8.9, 11.9, 12.6, and 13.7, respectively). Heterogeneity of plaques was more positively correlated with symptoms than with any degree of stenosis (regardless of plaque structure). Eighty percent of all heterogeneous plaques were symptomatic versus 58% for all stenoses > or =50%, 68% for all stenoses > or =60%, and 75% for all stenoses > or =70% (P<0.0001, P<0.0001, and P=0.02, respectively).

CONCLUSIONS

The higher the degree of carotid stenosis, the more likely it is to be associated with ultrasonic heterogeneous plaque and cerebrovascular symptoms. Heterogeneity of the plaque was more positively correlated with symptoms than with any degree of stenosis. These findings suggest that plaque heterogeneity should be considered in selecting patients for carotid endarterectomy.

Are antiphospholipid antibodies an independent risk factor for atherosclerosis?

The purpose of this study was to check whether antiphospholipid antibodies (aPL) could be an independent risk factor for atherosclerosis. Eighty-five subjects were studied: 45 with primitive antiphospholipid antibody syndrome and 40 controls affected by deep vein thrombosis secondary to known causes. The two groups were homogeneous for age, sex, and risk factors for atherosclerosis. All the subjects submitted to echo-color doppler of the carotid arteries, femoral arteries, and abdominal aorta. The cases were then subdivided into three subgroups on the basis of the positivity to the three subpopulations of aPL. Results demonstrate that there is no correlation between aPL and atherosclerosis. The different positivity to aPL does not modify this conclusion.

Carotid atherosclerotic plaque: noninvasive MR characterization and identification of vulnerable lesions

Measurement of vessel stenosis by using ultrasonography or angiography remains the principal method for determining the severity of carotid atherosclerosis and the need for endarterectomy. The ipsilateral stroke rate, however--even in patients with severely stenotic vessels--is relatively low, which suggests that the amount of luminal narrowing may not represent the optimal means of assessing clinical risk. As a result, some patients may undergo unnecessary surgery. Improved imaging techniques are, therefore, needed to enable reliable identification of high-risk plaques that lead to cerebrovascular events. High-spatial-resolution magnetic resonance (MR) imaging has been described as one promising modality for this purpose, because the technique allows direct visualization of diseased vessel wall and can be used to characterize the morphology of individual atherosclerotic carotid plaques. The purpose of this report is to review the current state of carotid plaque MR imaging and the use of carotid MR to evaluate plaque morphology and composition.

Real-time spatial compound imaging improves reproducibility in the evaluation of atherosclerotic carotid plaques

Compound imaging has the ability of reducing speckle and clutter artifacts demonstrated in in vitro studies compared to conventional, single-angle imaging. We investigated intra- and interobserver agreement of 38 outlines of carotid artery plaque images acquired by these techniques, by measuring the overlapping area after repeated outlines. In general, both techniques showed good agreement. When considering the images with poorest overlap, compound imaging had a significant advantage over conventional imaging regarding both intra- and interobserver agreement. The interobserver variation for the overlapping area after two outlines was 20% for conventional technique and 10% for compound. The interobserver variation of the gray scale median value (GSM) for conventional technique ranged from -32 to +20 and from -6 to +6 for compound. Likewise, the coefficient of repeatability for the GSM value was 13 for conventional imaging and three for compound imaging, and interobserver variation for the GSM value for the overlapping area was 34% and 9% for conventional and compound technique. In conclusion, compound imaging improves intra- and interobserver agreement and reduces interobserver variation in the GSM value in a clinical setting.

The significance of Chlamydia pneumoniae in symptomatic carotid stenosis

An association between symptomatic carotid stenosis and recent infection with Chlamydia pneumoniae is reported. Thirty-five patients (20 symptomatic and 15 asymptomatic) with carotid stenosis of 70% to 90% underwent carotid endarterectomy. Endarterectomy was performed without patch and shunt; the average occlusion time of the internal carotid artery was 14 +/- 3 min. The atheromatic plaque and a portion of the thyroid artery were examined with polymerase chain reaction and peripheral vein blood was obtained for serologic detection of systematic infection, and IgG and IgM antibodies to C. pneumoniae by enzyme-linked immunosorbent assay. Twenty of 35 patients (57.1%) had increased titers of IgG antibodies to C. pneumoniae. Eight patients revealed IgG plus IgM antibodies; two of the eight had IgG, IgM, and positive findings on polymerase chain reaction. No C. pneumoniae was detected on the thyroid arteries. Sixty-five percent (13/20) of the patients with increased IgG antibodies to C. pneumoniae, 87.5% (7/8) with IgG + IgM, and 100% with IgG + IgM + positive polymerase chain reaction were symptomatic. Plaque morphology in association with symptoms did not reveal a significant correlation between soft plaques and symptoms, whereas the majority of the symptomatic patients had plaques of type III-V. Patients having recent contamination and positive polymerase chain reaction had a significant relationship between C. pneumoniae infection and symptomatic carotid disease. This supports the hypothesis that C. pneumoniae infection can produce a kind of instability of the carotid plaque. The results of this study demonstrate that patients with advanced atherosclerotic carotid disease have an increased incidence of C. pneumoniae infection. Recent infection could be responsible for instability of the carotid plaque, causing cerebral ischemic episodes.

Increased Acute Phase Reactants are Associated with Levels of Lipoproteins and Increased Carotid Plaque Volume

OBJECTIVES

to test the hypotheses that increased acute phase reactants predict elevated levels of lipoproteins and increased plaque volume as well as echolucency of carotid plaques.

MATERIALS AND METHODS

the study included 258 patients with >or =50% carotid artery stenosis. Acute phase reactants (orosomucoid, C-reactive protein (CRP)) were measured in the fasting state, and ultracentrifugated lipoproteins before and after a standardised fat load test. Echogenicity of carotid plaques was detected using high-resolution B-mode ultrasound and computer-assisted image processing. A subgroup of 81 patients underwent carotid endarterectomy.

RESULTS

on linear regression analysis orosomucoid levels were positively associated with fasting and postprandial levels of all triglyceride-rich lipoproteins, and negatively associated with HDL cholesterol (p -values <0.0001); results for CRP were less pronounced. Orosomucoid and CRP both predicted the presence of an increased carotid plaque volume on univariate analysis (p =0.01 and p =0.02). Finally, orosomucoid was negatively associated with echolucency of carotid plaques ( p =0.05).

CONCLUSIONS

elevated levels of acute phase reactants are strongly associated with elevated levels of triglyceride-rich lipoproteins, increased plaque volume, and borderline significantly associated with echolucency of carotid plaques. Elevated acute phase reactants possibly predict severity of atherosclerosis, and presence of lipid-rich, rupture-prone plaques.

Patterns of brain computed tomography infarction and carotid plaque echogenicity

PURPOSE

It was suggested that in the absence of cardioembolism the discrete subcortical and cortical infarctions on brain computed tomography (CT) are most likely associated with carotid atheroma, whereas the hemodynamic infarctions, diffuse widespread white matter lesions, lacunae and basal ganglia infarctions are most likely associated with other pathologic conditions. The aim of this study was to determine the ultrasonic characteristics of carotid plaques and the degree of stenosis that were associated with the different brain CT infarction patterns and normal CT (pattern A, discrete subcortical and cortical infarctions; pattern B, hemodynamic infarctions, diffuse widespread white matter lesions, lacunae and basal ganglia infarctions).

METHODS

Four hundred nineteen carotid plaques (315 patients), producing 50% to 99% stenosis on duplex scanning, were studied. These plaques were imaged on duplex scanning, captured, digitized, and normalized (standardized) in a computer. Subsequently, their gray scale median (GSM) was evaluated to distinguish quantitatively the hypoechoic (low GSM) from the hyperechoic (high GSM) plaques. The brain CT infarction patterns of A, B, or normal CT on the ipsilateral hemisphere were noted.

RESULTS

The pattern A brain CT infarction was associated with carotid plaques having median GSM of 11 and median degree of stenosis of 80%, as contrasted with pattern B (median GSM, 28.5; median degree of stenosis, 75%) or normal CT (median GSM, 22; median degree of stenosis, 75%) (Kruskal-Wallis test, P <.001 for the GSM and P =.002 for the degree of stenosis). In the logistic regression analysis only the GSM and not the degree of stenosis distinguished the plaques associated with the three CT patterns.

CONCLUSIONS

The pattern A brain CT infarction was associated with hypoechoic plaques suggesting an involvement of extracranial carotid artery embolization, whereas the pattern B was associated with hyperechoic plaques suggesting an involvement of other mechanisms (hemodynamic, intracranial small and large vessel disease).

Relationship between ultrasound texture classification images and histology of atherosclerotic plaque

Structure and content of atherosclerotic plaque varies between patients and may be indicative of their risk for embolisation. This study aimed to construct parametric images of B-scan texture and assess their potential for predicting plaque morphology. Sequential transverse in vitro scans of 10 carotid plaques, excised during endarterectomy, were compared with macrohistology maps of plaque content. Multidiscriminant analysis combined the output of 157 statistical and textural algorithms into five separate texture classes, displayed as ultrasound (US) texture classification images (UTCI). Visual comparison between corresponding UTCI and histology maps found the five texture classes matched with the location of fibrin, elastin, calcium, haemorrhage or lipid. However, histology preparation removes calcium and lipid and, so, can affect the structural integrity of atherosclerotic plaques. Soft tissue regions smaller than the UTCI kernel, (0.87 mm x 0.85 mm x 3.9 mm), such as blood clots, are also difficult to detect by UTCI. These factors demonstrate limitations in the use of histology as a "gold standard" for US tissue characterisation.

Computer-assisted ultrasonographic analysis of carotid plaques in relation to cerebrovascular symptoms, cerebral infarction, and histology

The objective of this study was to determine the relationship between plaque echogenicity as measured by computer and the incidence of cerebrovascular symptoms and cerebral infarction. The correlation between carotid plaque echogenicity and plaque histology was also evaluated. In this prospective nonrandomized study, 38 consecutive patients with 54 atherosclerotic carotid plaques producing 50-99% stenosis were reviewed. The ultrasonic images of the plaques were digitized and transferred to a computer. A histogram for each plaque representing its composition was obtained. The median of the gray scale (GSM) of each histogram was used as measure of plaque echogenicity. All patients had a computed tomography (CT) brain scan performed to determine the presence of cerebral infarction. Twenty-eight plaques were examined histologically to determine the deposition of calcium, hemorrhage, cholesterol, and amorphous granular material. It is possible to identify carotid plaques at high risk for development of cerebrovascular symptoms and cerebral infarction by the computerized measurement of plaque echogenicity. This method may be used to improve the criteria of patients selection for carotid endarterectomy.

Hemispheric symptoms and carotid plaque echomorphology

PURPOSE

In patients with carotid bifurcation disease, the risk of stroke mainly depends on the severity of the stenosis, the presenting hemispheric symptom, and, as recently suggested, on plaque echodensity. We tested the hypothesis that asymptomatic carotid plaques and plaques of patients who present with different hemispheric symptoms are related to different plaque structure in terms of echodensity and the degree of stenosis.

METHODS

Two hundred sixty-four patients with 295 carotid bifurcation plaques (146 symptomatic, 149 asymptomatic) causing more than 50% stenosis were examined with duplex scanning. Thirty-six plaques were associated with amaurosis fugax (AF), 68 plaques were associated with transient ischemic attacks (TIAs), and 42 plaques were associated with stroke. B-mode images were digitized and normalized using linear scaling and two reference points, blood and adventitia. The gray scale median (GSM) of blood was set to 0, and the GSM of the adventitia was set to 190 (gray scale range, black = 0; white = 255). The GSM of the plaque in the normalized image was used as the objective measurement of echodensity.

RESULTS

The mean GSM and the mean degree of stenosis, with 95% confidence intervals, for plaques associated with hemispheric symptoms were 13.3 (10.6 to 16) and 80.5 (78.3 to 82.7), respectively; and for asymptomatic plaques, the mean GSM and the mean degree of stenosis were 30.5 (26.2 to 34.7) and 72. 2 (69.8 to 74.5), respectively. Furthermore, in plaques related to AF, the mean GSM and the mean degree of stenosis were 7.4 (1.9 to 12. 9) and 85.6 (82 to 89.2), respectively; in those related to TIA, the mean GSM and the mean degree of stenosis were 14.9 (11.2 to 18.6) and 79.3 (76.1 to 82.4), respectively; and in those related to stroke, the mean GSM and the mean degree of stenosis were 15.8 (10.2 to 21.3) and 78.1 (73.4 to 82.8), respectively.

CONCLUSION

Plaques associated with hemispheric symptoms are more hypoechoic and more stenotic than those associated with no symptoms. Plaques associated with AF are more hypoechoic and more stenotic than those associated with TIA or stroke or those without symptoms. Plaques causing TIA and stroke have the same echodensity and the same degree of stenosis. These findings confirm previous suggestions that hypoechoic plaques are more likely to be symptomatic than hyperechoic ones. They support the hypothesis that the pathophysiologic mechanism for AF is different from that for TIA and stroke.

Comparative results of staged and simultaneous bilateral carotid endarterectomy: a clinical study and surgical treatment

OBJECTIVE

Bilateral carotid stenoses are actually managed by staged endarterectomy. The present study compares the results of the above surgical procedure with simultaneous bilateral carotid endarterectomy.

METHODS

Sixty-four carotid endarterectomies were carried out on two groups of thirty-two patients with bilateral carotid stenoses. Fifteen patients (group A) were subjected to staged and 17 patients (group B) who were subjected to simultaneous bilateral carotid endarterectomies.

RESULTS

The mortality rate was zero in both groups; no statistically significant difference was found concerning complications related to the heart, neurological deficit and postoperative hypertension.

CONCLUSIONS

Simultaneous carotid endarterectomy is a challenging and technically demanding operation but with limited indications in strictly selected patients. The development of methods of more effective monitoring and protection of the cerebral cells might broaden the indications of such a surgical tactic in the future. Staged carotid endarterectomy, however, remains the method of choice for the management of bilateral carotid occlusive disease.

Noninvasive 3-D ultrasound of atherosclerotic plaques in the Watanabe rabbit

We have investigated the ability to quantitate atherosclerosis in the aortic arch of the Watanabe rabbit using noninvasive 3-D ultrasound. Our methodology utilizes postprocessing of videotaped freehand 2-D interrogations to form a compound 3-D data block. Structures may then be segmented on the attributed grey-scale level and volumes measured. Analysis of 3-D reconstructions revealed a low echo structure in the aortic arch of atherosclerotic rabbits, absent in nonatherosclerotic rabbits, at recognized sites of plaque predilection. This structure volume correlated closely with fatty streak volume determined from histology (r = 0.890). During a 30-week study, this structure volume increased in untreated animals, but was blocked by treatment with the antiatherosclerotic agent probucol. Thus, a new 3-D ultrasound methodology has been used noninvasively to detect and quantitate a low echo structure corresponding to fatty streaks in the Watanabe rabbit aortic arch. This new methodology could potentially aid plaque burden quantification in human peripheral arteries.

Effects of triflusal on arteriosclerosis progression assessed with high-resolution arterial ultrasound

In order to evaluate the effect of triflusal (2-acetyloxy-4-trifluoromethyl benzoic acid), an orally active antiplatelet agent, on arteriosclerosis progression, a pilot, parallel, double-dummy, double-blind clinical trial vs acetylsalicylic acid (ASA) was carried out in patients with subclinical atherosclerotic lesions. The trial consisted of a 2-week run-in placebo phase, followed by a 12-month oral treatment with triflusal (600 mg/day) or ASA (300 mg/day). The primary variable was identified in the ultrasonic biopsy (UB) score; the secondary variables were the UB class changes of each arterial site, the rate of progression (ROP), the intima-media thickness (IMT), and the symptoms of arteriosclerosis. Data were evaluated by use of analysis of variance and Chi-square test. Forty-three patients (31 men, 12 women, mean age 62.8 +/- 8.4 SD) were randomized to triflusal (15 men, 6 women, mean age 64.3 +/- 6.7) or to ASA (16 men, 6 women, mean age 61.3 +/- 9.6). The analysis of variance on the UB score showed no difference between treatments: the patients' UB scores remained unchanged with no progression, thus indicating that no patient worsened during treatment. When all arterial sites under evaluation are considered, 86% of the sites in the triflusal group and 85% in the ASA group remained unchanged. No relevant change was recorded in vital signs and routine laboratory tests. Gastric disturbances were reported by two and three patients treated with triflusal and ASA, respectively. In conclusion, triflusal appears as effective as ASA in slowing arteriosclerosis progression.

Dynamic MR imaging of the carotid wall

The purpose of this study was to clarify temporal changes of carotid wall enhancement using dynamic magnetic resonance (MR) and to correlate its findings with pathological conditions. Cervical carotid arteries of 84 consecutive patients were studied with a 1.5 T MR imager using phased array coils. Axial spoiled gradient-echo (SPGR) images (30-58 second scan time) with fat saturation were repeated 4-8 times after the injection of contrast material. We evaluated the presence and thickness of hypointense inner rims and hyperintense outer rims of the carotid wall, temporal changes of outer rim enhancement, and their changes in relation to pathological conditions. Hypointense inner rims and enhanced outer rims were clearly visualized in 87% (73/84) of our subjects. Enhancement of the outer rim was minimal in early phases and gradually increased. Patient age had a significant correlation with outer rim thickness. In the portions with large atheromatous plaques, inner rims were disrupted or thickened. A marked thickening of the outer rim was observed in one patient with arteritis. The outer rims adjacent to malignant tumors were often obscured. Our study suggests that dynamic MR images of the cervical carotid artery can uniquely demonstrate angiogenesis of the wall itself. The outer rim of the artery shows relatively rapid enhancement, and its thickness correlates with age.

Ultrasound and lipoproteins as predictors of lipid-rich, rupture-prone plaques in the carotid artery

The aim of this review is to summarize present knowledge of the ultrasonic detection and determinants of carotid atherosclerosis with lipid-rich cores and to review the evidence that these measures of plaque type may predict cerebral events. With the use of high-resolution ultrasound B-mode imaging, carotid plaques evaluated as only weakly reflecting the ultrasound beam (echolucent) have been associated with a higher risk of neurological events than are plaques reflecting the ultrasound signal strongly (echorich). Histologically, these echolucent plaques have a higher content of lipid and hemorrhage than do echorich plaques, which contain more calcification and fibrous tissue. Findings in the coronary arteries indicate that a lipid-rich plaque with a thin, fibrous cap is more vulnerable, is more prone to rupture, and cause symptoms compared with fibrous plaques. A search for determinants in the blood for these vulnerable plaques suggests that low density lipoprotein (LDL) cholesterol is the best lipid predictor for the extent of atherosclerosis, whereas triglyceride-rich lipoproteins in particular seem to predict an echolucent plaque. Lowering of LDL cholesterol and triglyceride-rich lipoproteins in plasma is associated with reduced progression of coronary atherosclerosis and coronary events. LDL cholesterol reduction is also associated with a reduced stroke rate. These improvements in the prognosis are thought to be the result of a reduction in the lipid content of the plaques, making them more stable and resistant to rupture rather than an actual reduction in plaque volume and degree of stenosis. In conclusion, it appears that ultrasound B-mode imaging as well as lipoproteins presumably may predict dangerous and rupture-prone, lipid-rich plaques in the carotid arteries, thereby being potential diagnostic tools in the prevention of neurological events.

Quantitative analysis of ultrasound B-mode images of carotid atherosclerotic plaque: correlation with visual classification and histological examination

This paper presents a quantitative comparison of three types of information available for 52 patients scheduled for carotid endarterectomy: subjective classification of the ultrasound images obtained during scanning before operation, first-and second-order statistical features extracted from regions of the plaque in still ultrasound images from three orthogonal scan planes and finally a histological analysis of the surgically removed plaque. The quantitative comparison was made with the linear model and with separation of the available data into training and test sets. The comparison of subjective classification with features from still ultrasound images revealed an overall agreement of 60% for classification of echogenicity and 70% for classification of structure. Comparison of the histologically determined relative volume of soft materials with features from the still images revealed a correlation coefficient of r = -0.42(p = 0.002). for mean echogenicity of the plaque region. The best performing feature was of second order and denoted Contrast (r = -0.5). Though significant, the latter correlation is probably not strong enough to be useful for clinical prediction of relative volume of soft materials for individual patients. Reasons for this is discussed in the paper, together with suggestions for improvements.

Ultrasonographic characterization of carotid plaques

The composition of atherosclerotic plaques in the carotid artery is assumed to be related to the development of neurological symptoms. The echo patterns produced by B-mode ultrasound may be of use in the assessment of the plaques' composition. It is suggested that fibrotic and "stable" plaques are more echogenic than lipid/hemorrhagic and echolucent or "unstable" plaques. B-mode ultrasound procedures were performed 1 day prior to surgery on 46 consecutive endarterectomies. Two observers assessed the plaques according to their echo pattern and echogenicity and sorted them into three categories: 1) predominantly echolucent, 2) heterogeneous, and 3) predominantly echogenic. The intraobserver agreement was moderate (kappa = 0.44) and the interobserver agreement low (kappa = 0.38). Furthermore, subjective categorization of plaque types resulted in type 1 plaques being as fibrotic as type 2 or 3 plaques. We conclude that B-mode ultrasound and subsequent subjective categorization of atherosclerotic plaques cannot adequately determine the volume of fibrosis or lipids within the plaque.

Multi-angle compound imaging

This paper reports on a scanning technique, denoted multi-angle compound imaging (MACI), using spatial compounding. The MACI method also contains elements of frequency compounding, as the transit frequency is lowered for the highest beam angles in order to reduce grating lobes. Compared to conventional B-mode imaging MACI offers better defined tissue boundaries and lower variance of the speckle pattern, resulting in an image with reduced random variations. Design and implementation of a compound imaging system is described, images of rubber tubes and porcine aorta are shown and effects on visualization are discussed. The speckle reduction is analyzed numerically and the results are found to be in excellent agreement with existing theory. An investigation of detectability of low-contrast lesions shows significant improvements compared to conventional imaging. Finally, possibilities for improving diagnosis of atherosclerotic diseases using MACI are discussed.