Plaque hemorrhage in carotid artery disease: pathogenesis, clinical and biomechanical considerations

Robustness and classification capabilities of MRI radiomic features in identifying carotid plaque vulnerability

OBJECTIVES

To assess how radiomic features may be combined with plaque morphological and compositional features identified by multi-contrast MRI to improve upon conventional risk assessment models in determining culprit carotid artery lesions.

METHODS

Fifty-five patients (mean age: 62.6; 35 males) with bilateral carotid stenosis who experienced transient ischaemic attack (TIA) or stroke were included from the CARE-II multi-centre carotid imaging trial (ClinicalTrials.gov Identifier: NCT02017756). They underwent MRI within 2 weeks of the event. Classification capability in distinguishing culprit lesions was assessed by machine learning. Repeatability and reproducibility of the results were investigated by assessing the robustness of the radiomic features.

RESULTS

Radiomics combined with a relatively conventional plaque morphological and compositional metric-based model provided incremental value over a conventional model alone (area under curve [AUC], 0.819 ± 0.002 vs 0.689 ± 0.019, respectively, P = .014). The radiomic model alone also provided value over the conventional model (AUC, 0.805 ± 0.003 vs 0.689 ± 0.019, respectively, P = .031). T2-weighted imaging-based radiomic features had consistently higher robustness and classification capabilities compared with T1-weighted images. Higher-dimensional radiomic features outperformed first-order features. Grey Level Co-occurrence Matrix, Grey Level Dependence Matrix, and Grey Level Size Zone Matrix sub-types were particularly useful in identifying textures which could detect vulnerable lesions.

CONCLUSIONS

The combination of MRI-based radiomic features and lesion morphological and compositional parameters provided added value to the reference-standard risk assessment for carotid atherosclerosis. This may improve future risk stratification for individuals at risk of major adverse ischaemic cerebrovascular events.

ADVANCES IN KNOWLEDGE

The clinical relevance of this work is that it addresses the need for a more comprehensive method of risk assessment for patients at risk of ischaemic stroke, beyond conventional stenosis measurement. This paper shows that in the case of carotid stroke, high-dimensional radiomics features can improve classification capabilities compared with stenosis measurement alone.

3D patient-specific modeling and structural finite element analysis of atherosclerotic carotid artery based on computed tomography angiography

The assessment of carotid plaque vulnerability is a relevant clinical information that can help prevent adverse cerebrovascular events. To this aim, in this study, we propose a patient-specific computational workflow to quantify the stress distribution in an atherosclerotic carotid artery, by means of geometric modeling and structural simulation of the plaque and vessel wall. Ten patients were involved in our study. Starting with segmentation of the lumen, calcific and lipid plaque components from computed tomography angiography images, the fibrous component and the vessel wall were semi-automatically reconstructed with an ad-hoc procedure. Finite element analyses were performed using local pressure values derived from ultrasound imaging. Simulation outputs were analyzed to assess how mechanical factors influence the stresses within the atherosclerotic wall. The developed reconstruction method was first evaluated by comparing the results obtained using the automatically generated fibrous component model and the one derived from image segmentation. The high-stress regions in the carotid artery wall around plaques suggest areas of possible rupture. In mostly lipidic and heterogeneous plaques, the highest stresses are localized at the interface between the lipidic components and the lumen, in the fibrous cap.

Systematic Review on Magnetic Resonance Angiography with Vessel Wall Imaging for the Characterization of Symptomatic Carotid Artery Plaque

BACKGROUND

To perform a systematic literature review to assess the usefulness of performing magnetic resonance angiography (MRA) with vessel wall imaging (VWI) sequences for the assessment of symptomatic carotid artery plaques and the identification of risky plaque features predisposing for stroke.

METHODS

We performed a systematic review of the literature pertaining to MRA with VWI techniques in patients with carotid artery disease, focusing on symptomatic patients' plaque features and morphology. Independent reviewers screened and analyzed data extracted from eligible studies, and a modified Newcastle-Ottawa Scale was used to appraise the quality of the design and content of the selected manuscripts to achieve an accurate interpretation.

RESULTS

This review included nineteen peer-reviewed manuscripts, all of them including MRA and VWI assessments of the symptomatic carotid artery plaque. We focused on patients' comorbidities and reviewed plaque features, including intraplaque hemorrhage, a lipid-rich necrotic core, a ruptured fibrous cap, and plaque ulceration.

CONCLUSIONS

MRA with VWI is a useful tool in the evaluation of carotid artery plaques. This imaging technique allows clinicians to identify plaques at risk of causing a neurovascular event. The presence of intraplaque hemorrhage, plaque ulceration, a ruptured fibrous cap, and a lipid-rich necrotic core are associated with neurovascular symptoms. The timely identification of these features could have a positive impact on neurovascular event prevention.

Carotid Artery Stenosis: A Look Into the Diagnostic and Management Strategies, and Related Complications

Carotid stenosis (CS) is a buildup of atherosclerotic plaque within the artery leading to a wide range of symptoms, from mild symptoms, including blurred vision and confusion, to much more life-threatening presentations, including paralysis due to stroke. The presentation is insidious, with symptoms exhibiting predominantly at severe stenosis; hence the emphasis is placed on the importance of early diagnosis, treatment, and lifestyle modifications. CS is seen undergoing almost the same pathogenesis of any atherosclerotic plaque formation, from endothelial damage of the artery lumen to the formation of a fibrous cap with a foam cell, lipid-filled core. The findings of our review article were consistent with the recent literature, depicting that comorbid hypertension, diabetes, and chronic kidney disease (CKD), and lifestyle aspects, including smoking and diet, played the most salient role in plaque development. Among several imaging modalities, duplex ultrasound (DUS) imaging is the widely preferred method in clinical practice. Carotid endarterectomy (CEA) and carotid stenting are the primarily advocated procedures for symptomatic severe stenosis, with similar long-term outcomes. Although, earlier clinical trials showed promising results in mitigating the risk of stroke among asymptomatic severe CS with surgical intervention. However, recent advancements have shifted the focus to medical management alone due to comparable results among the asymptomatic population. Both surgical and medical regimens are beneficial in treating patients, but it is still an ongoing debate as to which is predominantly superior. The currently advancing trials and research will help elucidate definitive guidelines. However, the massive impact of lifestyle modifications advocates some degree of individualized multidisciplinary management strategies.

Mechanical and histological characteristics of aortic dissection tissues

AIMS

This study investigated the association between the macroscopic mechanical response of aortic dissection (AoD) flap, its fibre features, and patient physiological features and clinical presentations.

METHODS

Uniaxial test was performed with tissue strips in both circumferential and longitudinal directions from 35 patients with (AoD:CC) and without (AoD:w/oCC) cerebral/coronary complications, and 19 patients with rheumatic or valve-related heart diseases (RH). A Bayesian inference framework was used to estimate the expectation of material constants (C₁, D₁, and D₂) of the modified Mooney-Rivlin strain energy density function. Histological examination was used to visualise the elastin and collagen in the tissue strips and image processing was performed to quantify their area percentages, fibre misalignment and waviness.

RESULTS

The elastin area percentage was negatively associated with age (p = 0.008), while collagen increased about 6% from age 40 to 70 (p = 0.03). Elastin fibre was less dispersed and wavier in old patients and no significant association was found between patient age and collagen fibre dispersion or waviness. Features of fibrous microstructures, either elastin or collagen, were comparable between AoD:CC and AoD:w/oCC group. Elastin and collagen area percentages were positively correlated with C₁ and D₂, respectively, while the elastin and collagen waviness were negatively correlated with C₁ and D₂, respectively. Elastin dispersion was negatively correlated to D₂. Multivariate analysis showed that D₂ was an effective parameter which could differentiate patient groups with different age and clinical presentations, as well as the direction of tissue strip.

CONCLUSION

Fibre dispersion and waviness in the aortic dissection flap changed with patient age and clinical presentations, and these can be captured by the material constants in the strain energy density function.

STATEMENT OF SIGNIFICANCE

Aortic dissection (AoD) is a severe cardiovascular disease. Understanding the mechanical property of intimal flap is essential for its risk evaluation. In this study, mechanical testing and histology examination were combined to quantify the relationship between mechanical presentations and microstructure features. A Bayesian inference framework was employed to estimate the expectation of the material constants in the modified Mooney-Rivlin constitutive equation. It was found that fibre dispersion and waviness in the AoD flap changed with patient age and clinical presentations, and these could be captured by the material constants. This study firstly demonstrated that the expectation of material constants can be used to characterise tissue microstructures and differentiate patients with different clinical presentations.

The MRI enhancement ratio and plaque steepness may be more accurate for predicting recurrent ischemic cerebrovascular events in patients with intracranial atherosclerosis

OBJECTIVES

To assess the complementary value of high-resolution multi-contrast MRI (hrMRI) in identifying symptomatic patients with intracranial atherosclerosis (ICAS) who are likely to experience recurrent ischemic cerebrovascular events.

METHODS

In this retrospective cohort study, eighty patients with acute ischemic events attributed to ICAS who underwent hrMRI examination between January 2015 and January 2019 were included. Median follow-up for all patients was 30 months (range: 1 to 52 months) and recurrent ischemic cerebrovascular events were recorded. Cox regression analysis and time-dependent ROC were performed to quantify the association between the plaque characteristics and recurrent events.

RESULTS

During the follow-up, 14 patients experienced recurrent ischemic cerebrovascular events. Young males and those with diabetes and poor medication persistence were more likely to experience recurrent events. ICAS in patients with recurrence had significantly higher enhancement ratio and steepness which is defined as the ratio between the plaque height and length than those without (p < 0.001 and p = 0.015, respectively). After adjustment of clinical factors, enhancement ratio (HR, 13.13 [95% CI, 3.58-48.20], p < 0.001) and plaque steepness (HR, 110.27 [95% CI, 4.75-2560.91], p = 0.003) were independent imaging biomarkers associated with recurrent events. Time-dependent ROC indicated that integrated high enhancement ratio and steepness into clinical risk factors improved discrimination power with the ROC increased from 0.79 to 0.94 (p = 0.008).

CONCLUSIONS

The enhancement ratio and plaque steepness improved the accuracy over traditional clinical risk factors in predicting recurrent ischemic cerebrovascular events for patients with ICAS.

KEY POINTS

• High-resolution magnetic resonance imaging helps clinicians to evaluate high-risk Intracranial plaque. • The higher enhancement ratio and plaque steepness (= height/length) were the primary biomarkers associated with future ischemic cerebrovascular events. • High-resolution magnetic resonance imaging combined with clinical characteristics showed a higher accuracy for the prediction of recurrent events in patients with intracranial atherosclerosis.

Normalized intraplaque hemorrhage signal on MP-RAGE as a marker for acute ischemic neurological events

PURPOSE

This study sought to validate whether the signal intensity ratio (SIR) of carotid intraplaque hemorrhage (IPH) was associated with acute ischemic neurologic events.

METHODS

A retrospective review was completed of consecutive patients that underwent neck magnetic resonance angiography using magnetization prepared-rapid gradient echo (MP-RAGE) and T1-CUBE sequences between 2017 and 2020. Patients with magnetic resonance evidence of IPH were included. SIRs were measured by comparing the maximum IPH signal with the mean intramuscular signal from the adjacent sternocleidomastoid. Patients were stratified into ischemic or non-ischemic groups based on the presence of acute ipsilateral ischemic events (stroke, retinal artery occlusion). Logistic regression analysis was performed to determine if increasing IPH SIR was associated with an increased risk of ipsilateral ischemic events.

RESULTS

Of 85 included patients (85 arteries), 66 were male (77.6%). Mean age was 71.0 (SD ± 11.1). There were 70 arteries with IPH that were ipsilateral to an ischemic event, and 15 that belonged to patients without an ischemic event. No association was found between increasing IPH SIR seen on MP-RAGE (odds ratio (OR): 0.82; 95% confidence interval (CI): 0.58-1.4; P = 0.43) or T1-CUBE sequences (OR: 0.85; 95% CI: 0.53-1.5; P = 0.56).

CONCLUSIONS

There was no association between the SIR of IPH and acute ischemia on either MP-RAGE or T1-CUBE sequences. Further investigation is required prior to widespread acceptance of SIR as a predictive imaging marker of symptomatic carotid plaque.

Extracranial Carotid Plaque Hemorrhage Is Independently Associated With Poor 3-month Functional Outcome After Acute Ischemic Stroke-A Prospective Cohort Study

Background and Purpose: Carotid plaque hemorrhage (IPH) is a critical plaque vulnerable feature. We aim to elucidate the association between symptomatic extracranial carotid atherosclerotic IPH and poor 3-month functional outcome after acute ischemic stroke by high-resolution vessel wall MRI (HRVMRI).

Methods: We prospectively studied consecutive patients with a recent stroke or transient ischemic attack (TIA) of carotid atherosclerotic origin. All patients underwent a High-Resolution (HR) VWMRI scan of ipsilateral extracranial carotid within 1 week after admission. The patients recruited were interviewed by telephone after 3 months after stroke onset. The primary outcome was a 3-month functional prognosis of stroke, expressed as a modified Rankin Scale (mRS) score. A poor prognosis was defined as a 3-month modified Rankin Scale (mRS) score ≥ of 3. Univariate analysis was used to analyze the correlation between risk factors and IPH. The relation between IPH and 3-month functional outcome was analyzed by Logistic regression analysis.

Results: A total of 156 patients (mean age, 61.18 ± 10.12 years; 108 males) were included in the final analysis. There were significant differences in the age, gender, smoking history, national institutes of health stroke scale (NIHSS) on admission, and diastolic blood pressure (DBP) on admission between the IPH group and the non-IPH group (all p < 0.05). During the follow-up, 32 patients (20.5%) had a poor functional outcome. According to the prognosis analysis of poor functional recovery, there was a significant difference between the two groups [36.7 vs. 16.7%; unadjusted odds ratio (OR), 2.32, 95% confidence interval (CI), 1.12–4.81, p = 0.024). Even after adjusting for confounding factors [such as age, gender, smoking history, National Institutes of Health Stroke Scale (NIHSS) on admission, DBP on admission, stenosis rate of carotid artery (CA), calcification, loose matrix, lipo-rich necrotic core (LRNC), and statins accepted at 3 months], IPH was still a strong predictor of poor 3-month outcome, and the adjusted OR was 3.66 (95% CI 1.68–7.94, p = 0.001).

Conclusions: Extracranial carotid IPH is significantly associated with poor 3-month outcome after acute ischemic stroke and can predict the poor 3-month functional prognosis.

Carotid atherosclerotic disease: A systematic review of pathogenesis and management

Carotid stenosis is an important contributor to ischemic stroke risk with resultant significant impact on neurological disability and death in adults and with worldwide implications. Management of carotid stenosis is impacted by whether there are associated symptoms along with the degree of stenosis. Understanding of the pathogenesis of carotid atherosclerosis or stenosis is important in management of carotid stenosis. Atherosclerotic plaque formation is a chronic insidious process with a number of potential contributors to the formation of such a plaque. The definition of atherosclerosis is not simply limited to abnormal deposition of lipid but also includes a chronic, complex, inflammatory process. Molecularly, in atherosclerosis, there is decreasing nitric oxide (NO) bioavailability, activity and/or expression of endothelial NO synthase, or increasing degradation of NO secondary to enhanced superoxide production. These above changes cause endothelial dysfunction leading to formation of foam cell followed by formation on lipid plaque. After lipid plaque formation, stable or unstable atherosclerotic plaque is formed depending on the calcium deposition over the lipid plaque. It continues to be clearly established that carotid intervention for symptomatic high-grade carotid stenosis is best managed with intervention either by carotid endarterectomy or carotid stenting. However, asymptomatic carotid stenosis is the subject of considerable controversy in terms of optimal management. This review of carotid atherosclerosis is an attempt to incorporate the information provided by more recent studies on pathogenesis and management which may help in the decision-making process for optimal management for protection against stroke.

Estimation of the zero-pressure computational start shape of atherosclerotic plaques: Improving the backward displacement method with deformation gradient tensor

Advances in medical imaging have enabled patient-specific biomechanical modelling of arterial lesions such as atherosclerosis and aneurysm. Geometry acquired from in-vivo imaging is already pressurized and a zero-pressure computational start shape needs to be identified. The backward displacement algorithm was proposed to solve this inverse problem, utilizing fixed-point iterations to gradually approach the start shape. However, classical fixed-point implementations were reported with suboptimal convergence properties under large deformations. In this paper, a dynamic learning rate guided by the deformation gradient tensor was introduced to control the geometry update. The effectiveness of this new algorithm was demonstrated for both idealized and patient-specific models. The proposed algorithm led to faster convergence by accelerating the initial steps and helped to avoid the non-convergence in large-deformation problems.

Multicomponent material property characterization of atherosclerotic human carotid arteries through a Bayesian Optimization based inverse finite element approach

OBJECTIVE

Plaque rupture in atherosclerotic carotid arteries is a main cause of ischemic stroke and it is correlated with high plaque stresses. Hence, analyzing stress patterns is essential for plaque specific rupture risk assessment. However, the critical information of the multicomponent material properties of atherosclerotic carotid arteries is still lacking greatly. This work aims to characterize component-wise material properties of atherosclerotic human carotid arteries under (almost) physiological loading conditions.

METHODS

An inverse finite element modeling (iFEM) framework was developed to characterize fibrous intima and vessel wall material properties of 13 cross sections from five carotids. The novel pipeline comprised ex-vivo inflation testing, pre-clinical high frequency ultrasound for deriving plaque deformations, pre-clinical high-magnetic field magnetic resonance imaging, finite element modeling, and a sample efficient machine learning based Bayesian Optimization.

RESULTS

The nonlinear Yeoh constants for the fibrous intima and wall layers were successfully obtained. The optimization scheme of the iFEM reached the global minimum with a mean error of 3.8% in 133 iterations on average. The uniqueness of the results were confirmed with the inverted Gaussian Process (GP) model trained during the iFEM protocol.

CONCLUSION

The developed iFEM approach combined with the inverted GP model successfully predicted component-wise material properties of intact atherosclerotic human carotids ex-vivo under physiological-like loading conditions.

SIGNIFICANCE

We developed a novel iFEM framework for the nonlinear, component-wise material characterization of atherosclerotic arteries and utilized it to obtain human atherosclerotic carotid material properties. The developed iFEM framework has great potential to be advanced for patient-specific in-vivo application.

Detection of Carotid Artery Stenosis with Intraplaque Hemorrhage and Neovascularization Using a Scanning Interferometer

Carotid artery stenosis (CAS) is a major cause of stroke or transient ischemic attack (TIA, mini-stroke) in the United States. Carotid endarterectomy (CEA), a surgical procedure, is used to treat CAS. According to the American Heart Association, 1 out of 5 patients underwent CEA inappropriately, which was most commonly due to apparent overestimation of stenosis severity, and half had uncertain indicators. The current imaging modalities are limited in providing critical information on carotid arterial plaque content, extent, and biology. To circumvent these limitations, we developed a sensing interferometer (SI) imaging system to assess vulnerable carotid plaques noninvasively to detect stenosis, neovascularization, and intraplaque hemorrhage (IPH). We have custom-built a SI prototype and its peripheral systems with back-mode-projection capability. We detected stenosis, neo-vessels, and IPH through SI imaging system in in vivo mice carotid atherosclerotic plaques and further verified the same plaques ex vivo through a histology scope, CRi Maestro, and histological analysis.

Assessment of carotid atherosclerotic plaque using 3D motion-sensitized driven-equilibrium prepared rapid gradient echo: a comparative study

Background

3D motion-sensitized driven-equilibrium prepared rapid gradient echo (MERGE) can characterize carotid atherosclerotic plaque morphology and composition. The present study aimed to evaluate its performance by comparing it with reference images and assessing the inter-reader agreement.

Methods

Eighty-four patients were prospectively recruited and scanned with 3D MERGE. Two trained magnetic resonance imaging (MRI) readers measured and calculated the maximum wall thickness (WT), maximum vessel diameter, total vessel area, lumen area, wall area, normalized wall index, plaque volume, intraplaque hemorrhage (IPH) volume, and calcification volume independently. IPH, calcification, mixed calcification, and ulceration were identified. The intraclass correlation coefficient (ICC) with 95% confidence interval (CI) was used to assess the inter-reader agreement. MERGE performance was assessed in terms of sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, kappa value (κ), and the results of the Bland-Altman analysis and compared with reference images.

Results

MERGE showed excellent inter-reader agreement (All ICCs >0.90). MERGE and simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP) showed excellent agreement in detecting IPH (κ=0.938) and measuring IPH volume (ICC =0.995; 95% CI: 0.991-0.997). MERGE and computed tomography angiography (CTA) showed strong consistency in detecting calcification (κ=0.814) and mixed calcification (κ=0.972), and in measuring calcification volume (ICC =0.996; 95% CI: 0.993-0.997). MERGE and digital subtraction angiography (DSA) showed relatively strong consistency in identifying ulceration (κ=0.737).

Conclusions

MERGE showed excellent performance in identifying and measuring IPH and calcification in carotid atherosclerotic plaques. Therefore, MERGE can be a promising imaging approach in atherosclerotic-vulnerable plaque.

Carotid artery stenosis – Current evidence and treatment recommendations

Background:

Carotid artery stenosis is an important cause for stroke. Carotid endarterectomy (CEA) reduces the risk of stroke in patients with symptomatic carotid stenosis and to some extent in patients with asymptomatic carotid stenosis. More than 20 years ago, carotid artery stenting (CAS) emerged as an endovascular treatment alternative to CEA.

Objective and Methods:

This review summarises the available evidence from randomised clinical trials in patients with symptomatic as well as in patients with asymptomatic carotid stenosis.

Results:

CAS is associated with a higher risk of death or any stroke between randomisation and 30 days after treatment than CEA (odds ratio (OR) = 1.74, 95% CI 1.3 to 2.33, p < 0.0001). In a pre-defined subgroup analysis, the OR for stroke or death within 30 days after treatment was 1.11 (95% CI 0.74 to 1.64) in patients <70 years old and 2.23 (95% CI 1.61 to 3.08) in patients ≥70 years old, resulting in a significant interaction between patient age and treatment modality (interaction p = 0.007). The combination of death or any stroke up to 30 days after treatment or ipsilateral stroke during follow-up also favoured CEA (OR = 1.51, 95% CI 1.24 to 1.85, p < 0.0001). In asymptomatic patients, there is a non-significant increase in death or stroke occurring within 30 days of treatment with CAS compared to CEA (OR = 1.72, 95% CI 1.00 to 2.97, p = 0.05). The risk of peri-procedural death or stroke or ipsilateral stroke during follow-up did not differ significantly between treatments (OR = 1.27, 95% CI 0.87 to 1.84, p = 0.22).

Discussion and Conclusion:

In symptomatic patients, randomised evidence has consistently shown CAS to be associated with a higher risk of stroke or death within 30 days of treatment than CEA. This extra risk is mostly attributed to an increase in strokes occurring on the day of the procedure in patients ≥70 years. In asymptomatic patients, there may be a small increase in the risk of stroke or death within 30 days of treatment with CAS compared to CEA, but the currently available evidence is insufficient and further data from ongoing randomised trials are needed.

Intracranial Atherosclerotic Plaque as a Potential Cause of Embolic Stroke of Undetermined Source

BACKGROUND

Previous studies investigated the potential mechanism of embolic stroke of undetermined source (ESUS) from extracranial artery plaque, but there has been no study other than a case report on high-risk intracranial plaque in ESUS.

OBJECTIVES

The aim of this study was to investigate the issue by evaluating the morphology and composition of intracranial plaque in patients with ESUS and small-vessel disease (SVD) using 3.0-T high-resolution magnetic resonance imaging.

METHODS

Two hundred forty-three consecutive patients with ESUS and 160 patients with SVD-associated stroke between January 2015 and December 2019 were retrospectively enrolled. Multidimensional parameters involving the presence of plaque on both sides, including remodeling index (RI), plaque burden, presence of discontinuity of plaque surface, thick fibrous cap, intraplaque hemorrhage, and complicated American Heart Association type VI plaque at the maximal luminal narrowing site, were evaluated using intracranial high-resolution magnetic resonance imaging.

RESULTS

Among 243 patients with ESUS, the prevalence of intracranial plaque was much higher in the ipsilateral than the contralateral side (63.8% vs. 42.8%; odds ratio [OR]: 5.25; 95% confidence interval [CI]: 2.83 to 9.73), a finding that was not evident in patients with SVD (35.6% vs. 30.6%; OR: 2.14; 95% CI: 0.87 to 5.26; p = 0.134). Logistic analysis showed that RI was independently associated with ESUS in model 1 (OR: 2.329; 95% CI: 1.686 to 3.217; p < 0.001) and model 2 (OR: 2.295; 95% CI: 1.661 to 3.172; p < 0.001). RI alone with an optimal cutoff of 1.162, corresponding to an area under the curve of 0.740, had good diagnostic efficiency for ESUS.

CONCLUSIONS

The present study supports an etiologic role of high-risk nonstenotic intracranial plaque in ESUS.

CT texture-based radiomics analysis of carotid arteries identifies vulnerable patients: a preliminary outcome study

PURPOSE

To assess the potential role of computed tomography (CT) texture analysis (CTTA) in identifying vulnerable patients with carotid artery atherosclerosis.

METHODS

In this case-control pilot study, 12 patients with carotid atherosclerosis and a subsequent history of transient ischemic attack or stroke were age and sex matched with 12 control cases with asymptomatic carotid atherosclerosis (follow-up time 103.58 ± 9.2 months). CTTA was performed using a commercially available research software package (TexRAD) by an operator blinded to clinical data. CTTA comprised a filtration-histogram technique to extract features at different scales corresponding to spatial scale filter (fine = 2 mm, medium = 3 mm, coarse = 4 mm), followed by quantification using histogram-based statistical parameters: mean, kurtosis, skewness, entropy, standard deviation, and mean value of positive pixels. A single axial slice was selected to best represent the largest cross-section of the carotid bifurcation or the greatest degree of stenosis, in presence of an atherosclerotic plaque, on each side.

RESULTS

CTTA revealed a statistically significant difference in skewness between symptomatic and asymptomatic patients at the medium (0.22 ± 0.35 vs - 0.18 ± 0.39, p < 0.001) and coarse (0.23 ± 0.22 vs 0.03 ± 0.29, p = 0.003) texture scales. At the fine-texture scale, skewness (0.20 ± 0.59 vs - 0.18 ± 0.58, p = 0.009) and standard deviation (366.11 ± 117.19 vs 300.37 ± 82.51, p = 0.03) were significant before correction.

CONCLUSION

Our pilot study highlights the potential of CTTA to identify vulnerable patients in stroke and TIA. CT texture may have the potential to act as a novel risk stratification tool in patients with carotid atherosclerosis.

Can carotid artery calcifications on dental radiographs predict adverse vascular events? A systematic review

OBJECTIVES

To investigate the predictive value of carotid artery calcifications (CACs) seen on dental imaging for future adverse events related to cerebrovascular and cardiovascular diseases.

METHODS

Electronic databases (PubMed, Embase, SCOPUS and Cochrane) and selected grey literature were searched. Outcomes included stroke, transient ischaemic attack (TIA), myocardial infarction (MI), angina, heart failure, future interventional revascularization procedures and death. Risk of bias was assessed using the Newcastle-Ottawa Scale.

RESULTS

5 studies were selected from 1011 records. All were of moderate to low risk of bias. Results were heterogeneous but showed that patients with CACs on panoramic radiographs (PANs) were more likely to experience strokes, TIA, MI and future revascularization procedures compared to control groups. The differences between groups were not all found to be statistically significant. Bilateral vessel-outlining CACs were an independent risk marker for future vascular events. Patients who are not currently being managed for cardiovascular risk factors should be referred for further evaluation. Those already being treated for atherosclerosis may not benefit from additional investigations.

CONCLUSION

The evidence for the predictive value of CACs on PANs for adverse future vascular events is equivocal but can help to identify at-risk patients who require further evaluation.

CLINICAL RELEVANCE

Dentists must be able to recognize CACs on PANs and make appropriate referrals for patients to be evaluated for cardiovascular risk factors, especially those who have not previously been assessed.

Normalized wall index, intraplaque hemorrhage and ulceration of carotid plaques correlate with the severity of ischemic stroke

BACKGROUND AND AIMS

Carotid atherosclerosis is considered an important cause of ischemic stroke. Tthis study aimed to explore the relationship between plaque features and the severity of stroke, and to identify plaque risk factors for the assessment of the severity of ischemic stroke.

METHODS

Symptomatic patients with carotid atherosclerotic plaques were prospectively recruited and underwent high-resolution vessel wall magnetic resonance imaging (VW-MRI). Two trained MRI readers independently identified intraplaque hemorrhage (IPH), calcification (CA), surface CA, deep CA, and ulceration. They measured and calculated the maximum vessel diameter (Max VD), maximum wall thickness (Max WT), total vessel area, lumen area, normalized wall index (NWI), plaque volume, IPH volume, IPH proportion, CA volume, and CA proportion. Patients were divided into two groups according to their National Institutes of Health Stroke Scale (NIHSS) scores (NIHSS ≤1 vs. NIHSS >1). Clinical characteristics and carotid plaque features were compared using the Mann-Whitney U test or Chi-square test as appropriate. Odds ratio (OR) and corresponding 95% confidence interval (CI) of plaque features to distinguish patients with NIHSS >1 were calculated. Spearman's rank correlations or Pearson correlations were determined for plaque features and NIHSS scores.

RESULTS

Of the 97 included patients, 34 (35.05%) with NIHSS >1 had significantly greater NWI (p < 0.05), larger IPH volume (p < 0.01), and greater IPH proportion (p < 0.01), and higher prevalence of IPH (OR, 5.654; 95%CI, 2.272-14.070; p < 0.01) and ulceration (OR, 2.891; 95%CI, 1.090-7.667; p = 0.033) than patients with NIHSS ≤1. Max WT (r = 0.24, p = 0.018), NWI (r = 0.22, p = 0.032), IPH (r = 0.27, p = 0.007), IPH volume (r = 0.35, p < 0.01), IPH proportion (r = 0.28, p = 0.005), and ulceration (r = 0.35, p < 0.01) had positive correlations with NIHSS scores.

CONCLUSIONS

NWI, IPH, and ulceration of carotid atherosclerotic plaque based on high-resolution VW-MRI may be useful indicators for assessing the severity of ischemic stroke in patients with atherosclerosis. NIHSS score is related to max WT, NWI, IPH, IPH volume, IPH proportion, and ulceration.

Carotid plaque imaging profiling in subjects with risk factors (diabetes and hypertension)

Carotid artery stenosis (CAS) due to the presence of atherosclerotic plaque (AP) is a frequent medical condition and a known risk factor for stroke, and it is also known from literature that several risk factors promote the AP development, in particular aging, smoke, male sex, hypertension, hyperlipidemia, smoke, diabetes type 1 and 2, and genetic factors. The study of carotid atherosclerosis is continuously evolving: even if the strategies of treatment still depends mainly on the degree of stenosis (DoS) determined by the plaque, in the last years the attention has moved to the study of the plaque components in order to identify the so called "vulnerable" plaque: features like the fibrous cap status and thickness, the volume of the lipid-rich necrotic core and the presence of intraplaque hemorrhage (IPH) are risk factors for plaque rupture, that can be studied with modern imaging techniques. The aim of this review is to give a general overview of the principle histological and imaging features of the subcomponent of carotid AP (CAP), focalizing in particular on the features of CAP of patients affected by hypertension and diabetes (in particular type 2 diabetes mellitus).

Comparison of carotid atherosclerotic plaques between subjects in Northern and Southern China: a Chinese atherosclerosis risk evaluation study

Background and purpose

To investigate differences in the characteristics of carotid atherosclerotic plaques of symptomatic subjects in northern and southern China using MRI.

Methods

Sixty-three subjects in northern China (mean age: 59.1±8.6 years, 45 men) and 56 subjects in southern China (mean age: 60.4±8.6 years, 38 men) were included. All subjects underwent carotid artery multicontrast vessel wall MRI. Plaque morphology, calcification, lipid-rich necrotic core, intraplaque haemorrhage, luminal surface disruption and high-risk plaque were measured and identified. All plaque characteristics were compared between subjects in northern and southern China using Mann-Whitney U test or χ² test.

Results

Compared with subjects in southern China, those in northern China had significantly greater areas for lumen (57.7±14.9 mm² vs 50.4±18.3 mm², p=0.009), wall (38.4±13.1 mm² vs 31.9±11.7 mm², p<0.001) and total vessel (96.1±20.2 mm² vs 82.4±22.7 mm², p=0.001) and mean wall thickness (1.25±0.43 mm vs 1.13±0.40 mm, p=0.019). χ² analysis showed that subjects in northern China tended to have a higher prevalence of intraplaque haemorrhage (14.3% vs 5.4%, p=0.106) and high-risk plaque (20.6% vs 10.7%, p=0.140) than those in southern China, although these differences were not statistically significant (all p>0.05).

Conclusion

Subjects in northern China have significantly larger vessel size and may have a higher prevalence of vulnerable plaques than those in southern China. Our findings provide additional perspective to optimise the management of cerebrovascular disease in individuals in different regions in China.

Trial registration number

NCT02017756

Correlation of MRI-detected vulnerable carotid plaques with clinical presentation: a systematic review and meta-analysis

INTRODUCTION

To determine the association between magnetic resonance imaging (MRI)-detected vulnerable Carotid Plaques and clinical presentation related to ipsilateral carotid artery territory.

EVIDENCE ACQUISITION

We searched three databases including Ovid MEDLINE, Ovid EMBASE, and Scopus from 2000 to 2018 for studies that evaluated vulnerable carotid plaques by MRI defined as intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), or thinning/rupture of the fibrous cap (TRFC). Data on study characteristics, clinical presentation, and MRI findings were extracted. Publication bias, methodologic quality, and study heterogeneity were assessed. Random-effects meta-analysis model was used to estimate incidence rate ratio (IRR) and 95% confidence intervals (CI) of MRI-detected vulnerable carotid plaque between symptomatic and asymptomatic arteries.

EVIDENCE SYNTHESIS

Of 2855 studies, 33 studies containing 6210 participants with 8401 assessed arteries were included. Overall, the risk of bias was moderate in 13, and low in 20 studies. The prevalence of MRI-positive IPH, TRFC, and LRNC were higher in symptomatic groups compared with the asymptomatic groups. In 11 studies that compared vulnerable carotid plaques between symptomatic and asymptomatic groups, symptomatic presentation was correlated with increased risk of IPH (IRR=1.57; 95% CI: 1.24-1.99), TRFC (IRR=2.26; 95% CI: 1.83 to 3.76), and LRNC (IRR=1.95; 95% CI: 1.28 to 2.97), respectively.

CONCLUSIONS

The presence of MRI-positive vulnerable carotid plaques including IPH, LRNC, and TRFC is positively associated with symptomatic clinical presentation. Therefore, carotid plaque MRI might be a useful risk stratification tool in determining the risk of ischemic stroke.

Relation between carotid vulnerable plaques and peripheral leukocyte: a case-control study of comparison utilizing multi-parametric contrast-enhanced ultrasound

Background

This study evaluates carotid vulnerable plaques using contrast-enhanced ultrasound (CEUS) and explores the relationship between vulnerable plaques and leukocytes.

Methods

Sixty-two symptomatic and 54 asymptomatic patients underwent CEUS. The images were analyzed using time-intensity and fitting curves, and peak (P_TIC), mean (M_TIC), peak (P_FC), sharpness (S_FC), and area under the curve (AUC_FC) were obtained. The relations between CEUS parameters and leukocytes were analyzed.

Results

In the symptomatic group, total leukocytes and neutrophils were higher, while lymphocyte was decreased; P_TIC, M_TIC, P_FC, S_FC, and AUC_FC were significantly higher; M_TIC and AUC_FC were negatively correlated with lymphocytes, and M_TIC was positively correlated with neutrophils. Classification and regression tree analysis showed that M_TIC at a cutoff of 20.8 and AUC_FC at a cutoff of 8.8 resulted in a predictive of acute cerebral infarction, accuracy of 84.3%, sensitivity of 87.1%, and specificity of 81.5%.

Conclusions

The variation in the perivascular leucocyte is significantly related to intraplaque inflammatory activities, CEUS is a feasible monitor of intraplaque neovascularization, so CEUS combined with perivascular leucocyte could be helpful as a warning for vulnerable plaques.

Size of carotid artery intraplaque hemorrhage and acute ischemic stroke: a cardiovascular magnetic resonance Chinese atherosclerosis risk evaluation study

BACKGROUND

To determine the usefulness of the size of carotid artery intraplaque hemorrhage (IPH) in discriminating the risk of acute ischemic stroke using cardiovascular magnetic resonance (CMR) vessel wall imaging.

METHODS

Symptomatic patients with carotid atherosclerotic plaque who participated in a cross-sectional, multicenter study of CARE-II (NCT02017756) were included. All patients underwent carotid and brain CMR imaging. Carotid plaque burden and the size of plaque compositions including calcification, lipid-rich necrotic core (LRNC), and IPH were measured. Presence of acute cerebral infarct (ACI) in ipsilateral hemisphere of carotid plaque was determined. The relationship between carotid plaque features and presence of ipsilateral ACI was then analyzed.

RESULTS

Of 687 recruited patients (62.7 ± 10.1 years; 69.4% males) with carotid plaque, 28.5% had ACI in ipsilateral hemispheres. Logistic regression revealed that carotid plaque burden was significantly associated with the presence of ACI before and after adjusted for clinical confounding factors. The volume of LRNC, %LRNC volume, volume of IPH, and %IPH volume were significantly associated with ACI before (volume of LRNC: OR = 1.297, p = 0.005; %LRNC volume: OR = 1.119, p = 0.018; volume of IPH: OR = 2.514, p = 0.003; %IPH volume: OR = 2.202, p = 0.003) and after (volume of LRNC: OR = 1.312, p = 0.006; %LRNC volume: OR = 1.90, p = 0.034; volume of IPH: OR = 2.907, p = 0.007; % IPH volume: OR = 2.374, p = 0.004) adjusted for clinical confounding factors. The association between volume of IPH and ACI remained statistically significant after further adjusted for plaque volume (OR = 2.813, p = 0.016) or both plaque volume and volume of LRNC (OR = 4.044, p = 0.024).

CONCLUSIONS

In symptomatic patients with carotid atherosclerotic plaques, the size of IPH is independently associated with ipsilateral ACI, suggesting the size of IPH might be a useful indicator for the risk of ACI.

TRIAL REGISTRATION

Clinical Trial Registration-URL: http://www.clinicaltrials.gov . Unique Identifier: NCT02017756.

Use of oral anticoagulant drugs is associated with carotid intraplaque hemorrhage in atherosclerosis patients: a meta-analysis

Patients with carotid atherosclerosis, especially the elderly population, take antithrombotic medicine regularly. However, no previous meta-analysis has focused on one of the possible side effects of such drugs, namely intraplaque hemorrhage (IPH). To determine whether antiplatelet drugs or anticoagulants are associated with an increased risk of carotid IPH. We searched Pubmed, Embase, Ovid MEDLINE, Cochrane Library for relevant studies that were published in English, from January 1st, 1989 to January 1st, 2019. We pooled the odds ratio (OR) with 95% confidence interval (CI) from individual studies and conducted quality assessment, heterogeneity, publication bias analysis and sensitivity analysis. A total of four cross-sectional studies, involving 2714 participants with carotid atherosclerotic plaques was included into this meta-analysis. We found a significant association between the use of anticoagulants and higher risk of carotid IPH (OR 1.95; 95% CI 1.16-3.30, P = 0.92; I² = 0). No significant association was found between the use of antiplatelet drugs and increased risk of carotid IPH (OR 1.34; 95% CI 0.68-2.61, P = 0.03; I² = 65%). Our meta-analysis reveals that it is the use of oral anticoagulants rather than antiplatelet drugs that may be associated with an increased risk of carotid IPH in atherosclerosis patients.

Carotid artery imaging: The study of intra-plaque vascularization and hemorrhage in the era of the "vulnerable" plaque

Intraplaque hemorrhage (IPH) is one of the main factors involved in atherosclerotic plaque (AP) instability. Its recognition is crucial for the correct staging and management of patients with carotid artery plaques to limit ischemic stroke. Imaging plays a crucial role in identifying IPH, even if the great variability of intraplaque vascularization and the limitations of our current imaging technologies make it difficult. The intent of this review is to give a general overview of the main features of intraplaque vascularization and IPH on Ultrasound (US), Computed Tomography (CT), Magnetic Resonance (MR) and Nuclear Medicine, and a brief description on the future prospectives.

Coupled Modeling of Lipid Deposition, Inflammatory Response and Intraplaque Angiogenesis in Atherosclerotic Plaque

We propose a multiphysical mathematical model by fully coupling lipid deposition, monocytes/macrophages recruitment and angiogenesis to investigate the pathophysiological responses of an atherosclerotic plaque to the dynamic changes in the microenvironment. The time evolutions of cellular (endothelial cells, macrophages, smooth muscle cells, etc.) and acellular components (low density lipoprotein, proinflammatory cytokines, extravascular plasma concentration, etc.) within the plaque microenvironment are assessed quantitatively. The thickening of the intima, the distributions of the lipid and inflammatory factors, and the intraplaque hemorrhage show a qualitative consistency with the MRI and histology data. Models with and without angiogenesis are compared to demonstrate the important role of neovasculature in the accumulation of blood-borne components in the atherosclerotic lesion by extravasation from the leaky vessel wall, leading to the formation of a lipid core and an inflammatory microenvironment, which eventually promotes plaque destabilization. This model can serve as a theoretical platform for the investigation of the pathological mechanisms of plaque progression and may contribute to the optimal design of atherosclerosis treatment strategies, such as lipid-lowering or anti-angiogenetic therapies.

Superficial and multiple calcifications and ulceration associate with intraplaque hemorrhage in the carotid atherosclerotic plaque

Objective

Intraplaque hemorrhage (IPH) and ulceration of carotid atherosclerotic plaques have been associated with vulnerability while calcification has been conventionally thought protective. However, studies suggested calcification size and location may increase plaque vulnerability. This study explored the association between calcium configurations and ulceration with IPH.

Methods

One hundred thirty-seven consecutive symptomatic patients scheduled for carotid endarterectomy were recruited. CTA and CTP were performed prior to surgery. Plaque samples were collected for histology. According to the location, calcifications were categorized into superficial, deep and mixed types; according to the size and number, calcifications were classified as thick and thin, multiple and single.

Results

Seventy-one plaques had IPH (51.8%) and 83 had ulceration (60.6%). The appearance of IPH and ulceration was correlated (r = 0.49; p < 0.001). The incidence of multiple, superficial and thin calcifications was significantly higher in lesions with IPH and ulceration compared with those without. After adjusting factors including age, stenosis and ulceration, the presence of calcification [OR (95% CI), 3.0 (1.1-8.2), p = 0.035], multiple calcification [3.9 (1.4-10.9), p = 0.009] and superficial calcification [3.4 (1.1-10.8), p = 0.001] were all associated with IPH. ROC analysis showed that the AUC of superficial and multiple calcifications in detecting IPH was 0.63 and 0.66, respectively (p < 0.05). When the ulceration was combined, AUC increased significantly to 0.82 and 0.83, respectively. Results also showed that patients with lesions of both ulceration and IPH have significantly reduced brain perfusion in the area ipsilateral to the infarction.

Conclusions

Superficial and multiple calcifications and ulceration were associated with carotid IPH, and they may be a surrogate for higher risk lesions.

Key Points

• CTA-defined superficial and multiple calcifications in carotid atherosclerotic plaques are independently associated with the presence of intraplaque hemorrhage.

• The combination of superficial and multiple calcifications and ulceration is highly predictive of carotid intraplaque hemorrhage.

• Patients with lesions of both ulceration and intraplaque hemorrhage have significantly reduced brain perfusion in the area ipsilateral to the infarction.

Functional Assessment of Intermediate Vascular Disease

Interventional treatment in various vascular beds has advanced tremendously. However, there are several problems to be considered. We searched the literature and tried to analyze major parts of it. One is safety and applicability of coronary proven methods in other vascular beds. An unresolved problem is the functional assessment of intermediate lesions, as far as various target organs have quite different circulation from the coronary one and the functional tests should be modified in order to be applicable and meaningful. In the majority of the acute vascular syndromes, the culprit lesion is of intermediate size on visual assessment. On the other hand, a procedurally successfully managed high-degree stenosis is not always followed by clinical and prognostic benefit. In vascular beds, where collateral network naturally exists, the readings from the functional assessment are complicated and thus the decision for interventional treatment is even more difficult. Here come into help the functional assessment and imaging with IVUS, OCT, high-resolution MRI, and contrast enhanced CT or SPECT. The focus of the current review is on the functional assessment of intermediate stenosis in other vascular beds, unlike the coronary arteries.

The Growing Field of Imaging of Atherosclerosis in Peripheral Arteries

In the past decades, peripheral arteries have represented a model for the comprehension of atherosclerosis as well as for the development of new diagnostic imaging modalities and therapeutic strategies. Peripheral arteries may represent a window to study atherosclerosis. Pathology has prominently contributed to move the clinical and research attention from the arterial lumen stenosis and angiography to morphological and functional imaging techniques. Evidence from large and prospective cohort or randomized controlled studies is still modest. Nevertheless, several emerging imaging investigations represent a potential tool for a comprehensive "in vivo" evaluation of the entire natural history of peripheral atherosclerosis. This constitutes a demanding assignment, as it would be desirable to obtain both single-lesion focused and extensive arterial system views to achieve the most accurate prognostic information. Our narrative review rests upon the fundamental pathological evidence, summarizing the rapidly growing field of imaging of atherosclerosis in peripheral arteries and presenting a selection of both currently available and emerging imaging techniques.

Dynamic change of carotid intraplaque hemorrhage volume in subjects with mild carotid stenosis

BACKGROUND AND PURPOSE

Early detection of intraplaque hemorrhage (IPH) in the carotid artery is important as it is correlated with an increased risk of cerebral ischemic events. We examined changes in IPH with magnetic resonance imaging (MRI) over an extended follow-up period in patients with mild carotid stenosis.

MATERIALS AND METHODS

From November 2013 to November 2015, we retrospectively reviewed cerebral MRI of 2036 patients, including magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequences obtained with a 3.0 T (T) MRI unit. An experienced neuroradiologist reviewed all studies and found 38 patients with carotid IPH and carotid stenosis that were categorized as mild (<30%), according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. Twenty-five patients agreed to join this study and signed informed consent for (MPRAGE) sequence imaging. We used semi-automated software to measure IPH volume on both the initial and follow up scans.

RESULTS

The median follow-up time of patients with mild carotid stenosis and IPH was 33.3 months. IPH volume increased in 10 of 27 carotid arteries (37.0%), with a mean volume increase of 42.6 ± 44.0 mm³. IPH volume decreased in 17 of 27 carotid arteries (63%), with a mean volume decrease of 17.2 ± 22.8 mm³. Two patients without IPH at baseline showed IPH development on follow-up imaging. There were no significant differences in patient demographics between the two groups.

CONCLUSIONS

Carotid IPH volume in subjects with mild carotid stenosis can change over time and may not be correlated with any typical patient demographics.

Mathematical modeling of atherosclerotic plaque destabilization: Role of neovascularization and intraplaque hemorrhage

Observational studies have identified angiogenesis from the adventitial vasa vasorum and intraplaque hemorrhage (IPH) as critical factors in atherosclerotic plaque progression and destabilization. Here we propose a mathematical model incorporating intraplaque neovascularization and hemodynamic calculation with plaque destabilization for the quantitative evaluation of the role of neoangiogenesis and IPH in the vulnerable atherosclerotic plaque formation. An angiogenic microvasculature is generated by two-dimensional nine-point discretization of endothelial cell proliferation and migration from the vasa vasorum. Three key cells (endothelial cells, smooth muscle cells and macrophages) and three key chemicals (vascular endothelial growth factors, extracellular matrix and matrix metalloproteinase) are involved in the plaque progression model, and described by the reaction-diffusion partial differential equations. The hemodynamic calculation of the microcirculation on the generated microvessel network is carried out by coupling the intravascular, interstitial and transvascular flow. The plasma concentration in the interstitial domain is defined as the description of IPH area according to the diffusion and convection with the interstitial fluid flow, as well as the extravascular movement across the leaky vessel wall. The simulation results demonstrate a series of pathophysiological phenomena during the vulnerable progression of an atherosclerotic plaque, including the expanding necrotic core, the exacerbated inflammation, the high microvessel density (MVD) region at the shoulder areas, the transvascular flow through the capillary wall and the IPH. The important role of IPH in the plaque destabilization is evidenced by simulations with varied model parameters. It is found that the IPH can significantly speed up the plaque vulnerability by increasing necrotic core and thinning fibrous cap. In addition, the decreased MVD and vessel permeability may slow down the process of plaque destabilization by reducing the IPH dramatically. We envision that the present model and its future advances can serve as a valuable theoretical platform for studying the dynamic changes in the microenvironment during the plaque destabilization.

Association of Age and Size of Carotid Artery Intraplaque Hemorrhage and Minor Fibrous Cap Disruption: A High Resolution Magnetic Resonance Imaging Study

Aim: To investigate the association between the volumes of different aging intraplaque hemorrhage (IPH) and minor fibrous cap disruption (MFCD) in carotid arteries.

Methods: Patients with cerebrovascular symptoms and carotid atherosclerotic plaques determined by ultrasound were recruited and underwent multi-contrast magnetic resonance (MR) vessel wall imaging for carotid arteries. Carotid plaques with IPH on MR imaging were included in the analysis. The age (fresh or recent) and the volume of IPH for each plaque were evaluated.

Results: In total, 41 carotid plaques in 37 patients (mean age 70.2 ± 11.0 years old; 32 males) were eligible for statistical analysis. The absolute volume of fresh IPH in plaques with MFCD was significantly larger than that in plaques without MFCD (109.83 ± 75.49 mm³ vs. 30.54 ± 20.62 mm³, P = 0.002). Logistic regression showed that the absolute volume of fresh IPH was significantly associated with MFCD before (odds ratio [OR], 1.735; 95% confidence interval [CI], 1.127–2.670; P = 0.012) and after adjusting for confounding factors (OR, 1.823; 95% CI, 1.076–3.090; P = 0.026). There was no significant association between recent IPH volume and MFCD (P > 0.05).

Conclusion: The volume of fresh IPH is independently associated with MFCD in carotid plaques, suggesting that integrity of fibrous cap may change with different age and size of IPH.

Animal models for plaque rupture: a biomechanical assessment

Rupture of atherosclerotic plaques is the main cause of acute cardiovascular events. Animal models of plaque rupture are rare but essential for testing new imaging modalities to enable diagnosis of the patient at risk. Moreover, they enable the design of new treatment strategies to prevent plaque rupture. Several animal models for the study of atherosclerosis are available. Plaque rupture in these models only occurs following severe surgical or pharmaceutical intervention. In the process of plaque rupture, composition, biology and mechanics each play a role, but the latter has been disregarded in many animal studies. The biomechanical environment for atherosclerotic plaques is comprised of two parts, the pressure-induced stress distribution, mainly - but not exclusively – influenced by plaque composition, and the strength distribution throughout the plaque, largely determined by the inflammatory state. This environment differs considerably between humans and most animals, resulting in suboptimal conditions for plaque rupture. In this review we describe the role of the biomechanical environment in plaque rupture and assess this environment in animal models that present with plaque rupture.

Gene expression profile analysis of the progression of carotid atherosclerotic plaques

The present study aimed to examine the universal gene expression signature and the underlying molecular mechanisms involved in the progression of carotid atherosclerotic plaques. The gene expression dataset, GSE28829, containing 13 early and 16 advanced carotid atherosclerotic plaques was selected for analysis. The differentially expressed genes (DEGs) were identified and analyzed using bioinformatics analyses, including cluster analysis, Gene Ontology (GO) and pathway enrichment analyses. Finally, a protein‑protein interaction (PPI) was constructed and analyzed. A total of 515 downregulated and 243 downregulated DEGs were identified. The cluster analysis revealed two separate two groups. In addition, the GO terms enriched by the upregulated DEGs were associated with immune response, and the downregulated DEGs were associated with cell adhesion. The upregulated DEGs were enriched in pathways associated with signaling in the immune system, and the downregulated DEGs were enriched in pathways associated with muscle contraction. In the PPI network analysis, ITGAM and ACTN2 had the highest decrees of connectivity in the upregulated and downregulated DEGs, respectively. These findings suggested that deregulation of the immune system and smooth muscle cell cytoskeleton accelerates the progression of carotid atherosclerotic plaques. The DEGs identified may offer potential in the prevention and treatment of atherosclerosis in the carotid artery.

Histological Characteristics of Intracranial Atherosclerosis in a Chinese Population: A Postmortem Study

Background

Anterior and posterior circulation atherosclerosis differ in vascular risk factors and stroke mechanisms. However, few studies have compared the pathological features between these lesions. Using a series of intracranial artery specimens, we characterized the intracranial atherosclerotic lesions and compared pathological features among different arteries of the intracranial vasculature.

Methods

Intracranial large arteries of 32 consecutively recruited autopsy cases of Chinese adults aged 45 years or older were examined pathologically using routine histology and immunostaining, to characterize the pathological features of the atherosclerotic lesions. We analyzed middle cerebral arteries (MCAs) (both left and right), vertebral arteries (VAs) (side more affected), and basilar arteries (BAs).

Results

Progressive atherosclerotic lesions were present in 91(71%) of the 128 arteries examined. Features of complicated plaques were infrequently detected: plaque hemorrhage was encountered in 12%, neovasculature in 12%, lumen thrombi in 13%, macrophage infiltration in 20%, and calcification in 25% of arteries. Luminal narrowing of MCA was the most severe, followed by VA; the BA least stenotic (37 ± 25 vs. 30 ± 24 vs. 20 ± 20%, all p < 0.05). MCA had more eccentric (vs. concentric) plaques than VA (69 vs. 25%, p = 0.003) and BA (69 vs. 38%; p = 0.03). Lumen thrombi were more frequent in BA, and calcification most commonly occurred in VA atherosclerotic lesions.

Conclusion

Intracranial atherosclerotic plaques were commonly present in this sample, but the lesions generally lacked features of complicated plaques. MCA lesions had demonstrable differences compared with VA and BA lesions. Further studies are needed to determine whether these characteristics indicate a distinctive atherosclerotic phenotype for the intracranial vasculature.

Intracranial Atherosclerosis: From Microscopy to High-Resolution Magnetic Resonance Imaging

Intracranial atherosclerosis is one of the leading causes of ischemic stroke and occurs more commonly in patients of Asian, African or Hispanic origin than in Caucasians. Although the histopathology of intracranial atherosclerotic disease resembles extracranial atherosclerosis, there are some notable differences in the onset and severity of atherosclerosis. Current understanding of intracranial atherosclerotic disease has been advanced by the high-resolution magnetic resonance imaging (HRMRI), a novel emerging imaging technique that can directly visualize the vessel wall pathology. However, the pathological validation of HRMRI signal characteristics remains a key step to depict the plaque components and vulnerability in intracranial atherosclerotic lesions. The purpose of this review is to describe the histological features of intracranial atherosclerosis and to state current evidences regarding the validation of MR vessel wall imaging with histopathology.

Identification of neovascularization by contrast-enhanced ultrasound to detect unstable carotid stenosis

Background

Plaque neovascularization accompanies local inflammation and critically contributes to plaque instability. Correct identification of intraplaque neovascularization by contrast–enhanced ultrasound (CEUS) may provide an additional risk marker in carotid stenosis. This pilot study investigates the correlation between histological evaluation of carotid plaque specimens and pre-surgery CEUS to identify neovascularization.

Methods

17 patients with high-grade internal carotid artery (ICA) stenosis were studied. CEUS was performed in all patients shortly before carotid endarterectomy. Neovascularization, infiltration of T cells and macrophages along with intraplaque hemorrhage were studied in excised plaques by immunohistochemistry. Ultrasound-based four-level and two-level classification systems for neovascularization were used. CEUS findings were compared with histological findings.

Results

Scores on the CEUS-based four-level and two-level classifications were robustly correlated with the density of intraplaque vessels (r = 0.635, p = 0.006 and r = 0.578, p = 0.015, respectively). Histological evaluation of regions with strong and prolonged intraplaque enhancement typically showed strong intraplaque neovascularization in conjunction with acute intraplaque hemorrhage. Moreover, higher grades of intraplaque neovascularization as determined by ultrasound were associated with a higher percentage of macrophage-rich areas.

Conclusion

CEUS is a technique well suited to gauge the degree of neovascularization of carotid plaques. Future research will have to define the reliability and validity of CEUS in everyday clinical practice. Further, our study suggests that CEUS may also be useful to pick up features of vulnerable plaques such as acute intraplaque hemorrhages.

Asymptomatic Carotid T1-High-Intense Plaque as a Risk Factor for a Subsequent Cerebrovascular Ischemic Event

Background: Intraplaque hemorrhage, detected as a high-signal intensity on carotid MRI, is also strongly associated with ischemic events in symptomatic patients. However, in asymptomatic patients, the relationship of the T1-high intense plaque and the subsequent stroke is not clear. The aim of this study is to test the hypothesis that asymptomatic carotid T1-high intense plaque is a risk factor for a subsequent cerebrovascular ischemic event. Methods: Of the 1,353 consecutive patients, who underwent head and carotid MRI as part of their annual medical check-up, the imaging quality of 13 was poor and 150 did not present for follow-up examination, thus leaving 1,190 subjects for evaluation. Of the 1,190 patients, 96 patients had findings of high-signal intensity on carotid MRI and 1,094 patients did not. Cerebrovascular events were retrospectively evaluated. Results: During a mean follow-up period of 53 months, 4 patients with high-signal intensities on carotid MRI (4%) and 3 with no findings (0.3%) had a cerebrovascular ischemic event, with the occurrences significantly higher in the high-signal-intensity group. (p < 0.01) Cox regression analysis indicated that the presence of the high-intense plaque on carotid MRI (hazard ratio [HR] 4.2; 95% CI 1.0-17.1; p = 0.04), age (HR 1.1; 95% CI 1.0-1.2; p = 0.003), and diabetes mellitus (HR 7.2; 95% CI 1.8-27.4; p = 0.004) were associated with the occurrence of subsequent ischemic cerebrovascular events. Conclusions: Asymptomatic carotid T1-high-intense plaque might be a potential high-risk factor for a subsequent cerebrovascular ischemic event.

High wall shear stress and high-risk plaque: an emerging concept

In recent years, there has been a significant effort to identify high-risk plaques in vivo prior to acute events. While number of imaging modalities have been developed to identify morphologic characteristics of high-risk plaques, prospective natural-history observational studies suggest that vulnerability is not solely dependent on plaque morphology and likely involves additional contributing mechanisms. High wall shear stress (WSS) has recently been proposed as one possible causative factor, promoting the development of high-risk plaques. High WSS has been shown to induce specific changes in endothelial cell behavior, exacerbating inflammation and stimulating progression of the atherosclerotic lipid core. In line with experimental and autopsy studies, several human studies have shown associations between high WSS and known morphological features of high-risk plaques. However, despite increasing evidence, there is still no longitudinal data linking high WSS to clinical events. As the interplay between atherosclerotic plaque, artery, and WSS is highly dynamic, large natural history studies of atherosclerosis that include WSS measurements are now warranted. This review will summarize the available clinical evidence on high WSS as a possible etiological mechanism underlying high-risk plaque development.

Observer performance in characterization of carotid plaque texture and surface characteristics with 3D versus 2D ultrasound

OBJECTIVE

To determine the reproducibility of three-dimensional (3D) ultrasound (US) over two-dimensional (2D) US in characterizing atherosclerotic carotid plaques using inter- and intra-observer agreement metrics.

METHODS

A Total of 51 patients with 105 carotid artery plaques were screened using 3D and 2D US probes attached to the same US scanner. Two independent observers characterized the plaques based on the morphological features namely echotexture, echogenicity and surface characteristics. The scores assigned to each morphological feature were used to determine intra- and inter-observer performance. The level of agreement was measured using Kappa coefficient.

RESULTS

The first observer with 2D US showed fair (k=0.4-0.59) and very strong (k>0.8) with 3D US intra-observer agreements using three morphological features. The second observer indicated moderate strong (k=0.6-0.79) with 2D US and very strong with 3D US (k>0.8) intra-observer performances. Moderate strong (k=0.6-0.79) and very strong (k>0.8) inter-observer agreements were reported with 2D US and 3D US respectively. The results with 2D and 3D US were correlated 62% using only echotexture and 56% using surface morphology coupled with echogenicity. 3D US gave a lower score than 2D 71% of the time (p=0.005) in disagreement cases.

CONCLUSION

High reproducibility in carotid plaque characterization was obtained using 3D US rather than 2D US. Hence, it can be a preferred imaging modality in routine or follow up plaque screening of patients with carotid artery disease.

Plaque angiogenesis and its relation to inflammation and atherosclerotic plaque destabilization

PURPOSE OF REVIEW

The review discusses the recent literature on plaque angiogenesis and its relation to inflammation and plaque destabilization. Furthermore, it discusses how plaque angiogenesis can be used to monitor atherosclerosis and serve as a therapeutic target.

RECENT FINDINGS

Histopathologic studies have shown a clear relationship between plaque angiogenesis, intraplaque hemorrhage (IPH), plaque vulnerability, and cardiovascular events. Hypoxia is a main driver of plaque angiogenesis and the mechanism behind angiogenesis is only partly known. IPH, as the result of immature neovessels, is associated with increased influx of inflammatory cells in the plaques. Experimental models displaying certain features of human atherosclerosis such as plaque angiogenesis or IPH are developed and can contribute to unraveling the mechanism behind plaque vulnerability. New imaging techniques are established, with which plaque angiogenesis and vulnerability can be detected. Furthermore, antiangiogenic therapies in atherosclerosis gain much attention.

SUMMARY

Plaque angiogenesis, IPH, and inflammation contribute to plaque vulnerability. Histopathologic and imaging studies together with specific experimental studies have provided insights in plaque angiogenesis and plaque vulnerability. However, more extensive knowledge on the underlying mechanism is required for establishing new therapies for patients at risk.

Delivery of bevacizumab to atheromatous porcine carotid tissue using echogenic liposomes

Ultrasound is both a valuable diagnostic tool and a promoter of beneficial tissue bioeffects for the treatment of cardiovascular disease. Vascular effects can be mediated by mechanical oscillations of circulating microbubbles that may also encapsulate and shield therapeutic agents in the bloodstream. Here, the effect of color-Doppler ultrasound exposure on bevacizumab-loaded liposome delivery into the vascular bed was assessed in atheromatous porcine carotids. Bevacizumab, an anti-angiogenic antibody to vascular endothelial growth factor (VEGF-A), was loaded into echogenic liposomes (BEV-ELIP) and confirmed to be immunoreactive. BEV-ELIP flowing within the lumen were exposed to color-Doppler ultrasound at three acoustic pressures for 3.5 min during treatment at physiologic temperature and fluid pressure. To confirm the presence of bubble activity, cavitation was detected within the lumen by a single-element passive cavitation detector. After treatment, the artery was fixed at physiologic pressure and subjected to immunohistochemical analysis to assess the penetration of bevacizumab within the carotid wall. The results suggest that other factors may more strongly influence the deposition of bevacizumab into carotid tissue than color-Doppler ultrasound and cavitation. In both sets of arteries, preferential accumulation of bevacizumab occurred in locations associated with atheroma progression and neointimal thickening: fibrous tissue, necrotic plaque and areas near macrophage infiltration. The delivery of bevacizumab to carotid vascular tissue correlated with the properties of the tissue bed, such as permeability, or affinity for growth-factor binding. Future investigations using this novel therapeutic strategy may focus on characterizing the spatial extent of delivery and bevacizumab colocalization with biochemical markers of atheroma.

[Magnetic resonance imaging characteristics of unilateral versus bilateral intraplaque hemorrhage in patients with carotid atherosclerotic plaques]

OBJECTIVE

To investigate the difference in the vulnerability of carotid atherosclerotic plaques in patients with unilateral and bilateral intraplaque hemorrhage (IPH).

METHODS

A retrospective analysis was conducted among 44 patients with unilateral IPH (30 cases) or bilateral IPH (14 cases) in the carotid plaques detected by magnetic resonance imaging (MRI) in our hospital between December, 2009 and December, 2012. The age, maximum wall thickness and incidence of fibrous cap rupture were compared between the two groups.

RESULTS

Compared with those with unilateral IPH, the patients with bilateral IPHs had a significantly younger age (66.6∓9.4 years vs 73.7∓9.0 years, P=0.027), a significantly greater maximum plaque thickness (6.3∓1.9 mm vs 5.0∓1.3 mm, P=0.035) and a higher incidence of ulcers (50% vs 13.3%, P=0.025). Logistic regression analysis revealed a significant association between bilateral IPHs and the occurrence of ulcer with an odd ratio (OR) of 6.5 (95% confidence interval [CI]: 1.5-28.7, P=0.014). After adjustment for gender in Model 1, bilateral IPHs were still significantly associated with presence of ulcer (OR=5.7, 95%CI: 1.1-29.2, P=0.036). But after adjustment for age (P=0.131) or maximum plaque thickness (P=0.139) in model 2, no significant correlation was found between bilateral IPHs and the presence of ulcer.

CONCLUSION

Compared with patients with unilateral IPH, those with bilateral IPHs are at a younger age and have a greater plaque burden and a higher incidence of fibrous cap rupture, suggesting a greater vulnerability of the carotid plaques in patients with bilateral IPHs.

Quest for the Vulnerable Atheroma: Carotid Stenosis and Diametric Strain--A Feasibility Study

The Bernoulli effect may result in eruption of a vulnerable carotid atheroma, causing a stroke. We measured electrocardiography (ECG)-registered QRS intra-stenotic blood velocity and atheroma strain dynamics in carotid artery walls using ultrasonic tissue Doppler methods, providing displacement and time resolutions of 0.1 μm and 3.7 ms. Of 22 arteries, 1 had a peak systolic velocity (PSV) >280 cm/s, 4 had PSVs between 165 and 280 cm/s and 17 had PSVs <165 cm/s. Eight arteries with PSVs <65 cm/s and 4 of 9 with PSVs between 65 and 165 cm/s had normal systolic diametric expansion (0% and 7%) and corresponding systolic wall thinning. The remaining 10 arteries had abnormal systolic strain dynamics, 2 with diametric reduction (>-0.05 mm), 2 with extreme wall expansion (>0.1 mm), 2 with extreme wall thinning (>-0.1 mm) and 4 with combinations. Decreases in systolic diameter and/or extreme systolic arterial wall thickening may indicate imminent atheroma rupture.

A uni-extension study on the ultimate material strength and extreme extensibility of atherosclerotic tissue in human carotid plaques

Atherosclerotic plaque rupture occurs when mechanical loading exceeds its material strength. Mechanical analysis has been shown to be complementary to the morphology and composition for assessing vulnerability. However, strength and stretch thresholds for mechanics-based assessment are currently lacking. This study aims to quantify the ultimate material strength and extreme extensibility of atherosclerotic components from human carotid plaques. Tissue strips of fibrous cap, media, lipid core and intraplaque hemorrhage/thrombus were obtained from 21 carotid endarterectomy samples of symptomatic patients. Uni-extension test with tissue strips was performed until they broke or slid. The Cauchy stress and stretch ratio at the peak loading of strips broken about 2 mm away from the clamp were used to characterize their ultimate strength and extensibility. Results obtained indicated that ultimate strength of fibrous cap and media were 158.3 [72.1, 259.3] kPa (Median [Inter quartile range]) and 247.6 [169.0, 419.9] kPa, respectively; those of lipid and intraplaque hemorrhage/thrombus were 68.8 [48.5, 86.6] kPa and 83.0 [52.1, 124.9] kPa, respectively. The extensibility of each tissue type were: fibrous cap – 1.18 [1.10, 1.27]; media – 1.21 [1.17, 1.32]; lipid – 1.25 [1.11, 1.30] and intraplaque hemorrhage/thrombus – 1.20 [1.17, 1.44]. Overall, the strength of fibrous cap and media were comparable and so were lipid and intraplaque hemorrhage/thrombus. Both fibrous cap and media were significantly stronger than either lipid or intraplaque hemorrhage/thrombus. All atherosclerotic components had similar extensibility. Moreover, fibrous cap strength in the proximal region (closer to the heart) was lower than that of the distal. These results are helpful in understanding the material behavior of atherosclerotic plaques.

Intraplaque Hemorrhage and the Plaque Surface in Carotid Atherosclerosis: The Plaque At RISK Study (PARISK)

BACKGROUND AND PURPOSE

An important characteristic of vulnerable plaque, intraplaque hemorrhage, may predict plaque rupture. Plaque rupture can be visible on noninvasive imaging as a disruption of the plaque surface. We investigated the association between intraplaque hemorrhage and disruption of the plaque surface.

MATERIALS AND METHODS

We selected the first 100 patients of the Plaque At RISK study, an ongoing prospective noninvasive plaque imaging study in patients with mild-to-moderate atherosclerotic lesions in the carotid artery. In carotid artery plaques, disruption of the plaque surface (defined as ulcerated plaques and/or fissured fibrous cap) and intraplaque hemorrhage were assessed by using MDCTA and 3T MR imaging, respectively. We used a χ(2) test and multivariable logistic regression to assess the association between intraplaque hemorrhage and disrupted plaque surface.

RESULTS

One hundred forty-nine carotid arteries in 78 patients could be used for the current analyses. Intraplaque hemorrhage and plaque ulcerations were more prevalent in symptomatic compared with contralateral vessels (hemorrhage, 38% versus 11%; P < .001; and ulcerations, 27% versus 7%; P = .001). Fissured fibrous cap was more prevalent in symptomatic compared with contralateral vessels (13% versus 4%; P = .06). After adjustment for age, sex, diabetes mellitus, and degree of stenosis, intraplaque hemorrhage was associated with disrupted plaque surface (OR, 3.13; 95% CI, 1.25-7.84) in all vessels.

CONCLUSIONS

Intraplaque hemorrhage is associated with disruption of the plaque surface in patients with a carotid artery stenosis of <70%. Serial studies are needed to investigate whether intraplaque hemorrhage indeed increases the risk of plaque rupture and subsequent ischemic stroke during follow-up.

Influence of material property variability on the mechanical behaviour of carotid atherosclerotic plaques: a 3D fluid-structure interaction analysis

Mechanical analysis has been shown to be complementary to luminal stenosis in assessing atherosclerotic plaque vulnerability. However, patient-specific material properties are not available and the effect of material properties variability has not been fully quantified. Media and fibrous cap (FC) strips from carotid endarterectomy samples were classified into hard, intermediate and soft according to their incremental Young's modulus. Lipid and intraplaque haemorrhage/thrombus strips were classified as hard and soft. Idealised geometry-based 3D fluid-structure interaction analyses were performed to assess the impact of material property variability in predicting maximum principal stress (Stress-P1 ) and stretch (Stretch-P1 ). When FC was thick (1000 or 600 µm), Stress-P1 at the shoulder was insensitive to changes in material stiffness, whereas Stress-P1 at mid FC changed significantly. When FC was thin (200 or 65 µm), high stress concentrations shifted from the shoulder region to mid FC, and Stress-P1 became increasingly sensitive to changes in material properties, in particular at mid FC. Regardless of FC thickness, Stretch-P1 at these locations was sensitive to changes in material properties. Variability in tissue material properties influences both the location and overall stress/stretch value. This variability needs to be accounted for when interpreting the results of mechanical modelling.

Advances in MRI for the evaluation of carotid atherosclerosis

Carotid artery atherosclerosis is an important source of mortality and morbidity in the Western world with significant socioeconomic implications. The quest for the early identification of the vulnerable carotid plaque is already in its third decade and traditional measures, such as the sonographic degree of stenosis, are not selective enough to distinguish those who would really benefit from a carotid endarterectomy. MRI of the carotid plaque enables the visualization of plaque composition and specific plaque components that have been linked to a higher risk of subsequent embolic events. Blood suppressed T1 and T2 weighted and proton density-weighted fast spin echo, gradient echo and time-of-flight sequences are typically used to quantify plaque components such as lipid-rich necrotic core, intraplaque haemorrhage, calcification and surface defects including erosion, disruption and ulceration. The purpose of this article is to review the most important recent advances in MRI technology to enable better diagnostic carotid imaging.