Angiogenesis and the atherosclerotic carotid plaque: an association between symptomatology and plaque morphology

Impact of distribution of carotid intraplaque neovessels on plaque vulnerability

BACKGROUND AND PURPOSE

Intraplaque neovessels (INVs) are considered important contributors to carotid plaque vulnerability. The purpose of this study was to examine whether differences in INV distribution affect plaque vulnerability.

METHODS

The study cohort comprised 110 patients with significant stenosis of the carotid artery who had undergone carotid endarterectomy. The distribution of INVs within carotid plaques was assessed by immunohistochemical studies using anti-CD-34 antibody as a marker for endothelial cells. First, we divided the patients into M group and S group depending on the numbers of INVs in middle and shoulder region. Next, we categorized carotid plaques into four categories according to the distributions of INVs: Shoulder, Middle, Mixed, and Scarce. We then compared total area of intraplaque hemorrhage, cholesterol, and calcification, width of thinnest fibrous cap, and number of INVs between the four categories of plaque.

RESULTS

The area of intraplaque hemorrhage was significantly larger in the M group than in the S group (P = 0.011). Meanwhile, symptomatic carotid stenosis was significantly more frequently associated with the Middle and Mixed than the Shoulder and Scarce categories (P < 0.01). The area of intraplaque hemorrhage was significantly different between the four groups (P = 0.022). Rupture of the fibrous cap was more frequently detected in the Middle and Mixed than the other categories (P = 0.002).

CONCLUSIONS

INVs in the middle region of carotid plaques are strongly associated with symptomatic carotid stenosis, intraplaque hemorrhage, and rupture of the fibrous cap. Our findings indicate that the distribution of INVs may affect plaque vulnerability.

Assessment of Plaque Characteristics by Contrast-Enhanced Ultrasound and Stent Restenosis following Carotid Artery Stenting: A Retrospective Study

Background and objective: carotid artery stenosis contributes significantly to ischemic strokes, with management options including carotid endarterectomy (CEA) and carotid artery stenting (CAS) ischemic stroke risk can be reduced. Controversies persist regarding their efficacy and factors influencing complications, and understanding the relationship between atherosclerotic plaque characteristics and stent restenosis after CAS is crucial. Methods: we conducted a retrospective study involving 221 patients who underwent CAS for symptomatic or asymptomatic carotid artery stenosis. Comprehensive assessments of plaque morphology were performed using contrast-enhanced ultrasound (CEUS) before CAS. Patient demographics, including smoking status and diabetes, were also recorded. Stent restenosis was diagnosed using various imaging modalities, including ultrasound, angiography, and digital subtraction angiography (DSA). Results: plaque analysis using CEUS revealed a significant association between plaque grade and restenosis incidence (p < 0.001), particularly with grade 0 (11.1%) and grade 2 plaques (66.7%). Smoking was notably associated with plaque vascularization and restenosis (p < 0.001), while diabetes did not significantly impact plaque characteristics or restenosis risk (p > 0.05). The mean duration of restenosis was 17.67 months. Stenting was the most frequent treatment modality for restenosis (70.6%). However, no significant relationship was found between restenosis type and plaque morphology (p = 0.268). Furthermore, while no clear relationship was observed between plaque morphology and the type of restenosis, our findings underscored the importance of plaque characterization in predicting post-CAS outcomes. Conclusions: this study highlights the utility of CEUS in predicting stent restenosis following CAS. There was a significant association between stent restenosis within 12-24 months after the carotid stenting procedure and an elevated grade of plaque vascularization. Moreover, one of the main factors possibly determining the grade of plaque vascularization was smoking. Further research is warranted to elucidate the underlying mechanisms and refine risk stratification in this patient population.

Molecular Pathways of Vulnerable Carotid Plaques at Risk of Ischemic Stroke: A Narrative Review

The concept of vulnerable carotid plaques is pivotal in understanding the pathophysiology of ischemic stroke secondary to large-artery atherosclerosis. In macroscopic evaluation, vulnerable plaques are characterized by one or more of the following features: microcalcification; neovascularization; lipid-rich necrotic cores (LRNCs); intraplaque hemorrhage (IPH); thin fibrous caps; plaque surface ulceration; huge dimensions, suggesting stenosis; and plaque rupture. Recognizing these macroscopic characteristics is crucial for estimating the risk of cerebrovascular events, also in the case of non-significant (less than 50%) stenosis. Inflammatory biomarkers, such as cytokines and adhesion molecules, lipid-related markers like oxidized low-density lipoprotein (LDL), and proteolytic enzymes capable of degrading extracellular matrix components are among the key molecules that are scrutinized for their associative roles in plaque instability. Through their quantification and evaluation, these biomarkers reveal intricate molecular cross-talk governing plaque inflammation, rupture potential, and thrombogenicity. The current evidence demonstrates that plaque vulnerability phenotypes are multiple and heterogeneous and are associated with many highly complex molecular pathways that determine the activation of an immune-mediated cascade that culminates in thromboinflammation. This narrative review provides a comprehensive analysis of the current knowledge on molecular biomarkers expressed by symptomatic carotid plaques. It explores the association of these biomarkers with the structural and compositional attributes that characterize vulnerable plaques.

MR Angiography of Extracranial Carotid Disease

Magnetic resonance angiography sequences, such as time-of-flight and contrast-enhanced angiography, provide clear depiction of vessel lumen, traditionally used to evaluate carotid pathologic conditions such as stenosis, dissection, and occlusion; however, atherosclerotic plaques with a similar degree of stenosis may vary tremendously from a histopathological standpoint. MR vessel wall imaging is a promising noninvasive method to evaluate the content of the vessel wall at high spatial resolution. This is particularly interesting in the case of atherosclerosis as vessel wall imaging can identify higher risk, vulnerable plaques as well as has potential applications in the evaluation of other carotid pathologic conditions.

Novel theranostic approaches to neovascularized atherosclerotic plaques

As the global burden of atherosclerotic cardiovascular disease continues to rise, there is an increased demand for improved imaging techniques for earlier detection of atherosclerotic plaques and new therapeutic targets. Plaque lesions, vulnerable to rupture and thrombosis, are thought to be responsible for the majority of cardiovascular events, and are characterized by a large lipid core, a thin fibrous cap, and neovascularization. In addition to supplying the plaque core with increased inflammatory factors, these pathological neovessels are tortuous and leaky, further increasing the risk of intraplaque hemorrhage. Clinically, plaque neovascularization has been shown to be a significant and independent predictor of adverse cardiovascular outcomes. Microvessels can be detected through contrast-enhanced ultrasound (CEUS) imaging, however, clinical assessment in vivo is generally limited to qualitative measures of plaque neovascularization. There is no validated standard for quantitative assessment of the microvessel networks found in plaques. Advances in our understanding of the pathological mechanisms underlying plaque neovascularization and its significant role in the morbidity and mortality associated with atherosclerosis have made it an attractive area of research in translational medicine. Current areas of research include the development of novel therapeutic and diagnostic agents to target plaque neovascularization stabilization. With recent progress in nanotechnology, nanoparticles have been investigated for their ability to specifically target neovascularization. Contrast microbubbles have been similarly engineered to carry loads of therapeutic agents and can be visualized using CEUS. This review summarizes the pathogenesis, diagnosis, clinical significance of neovascularization, and importantly the emerging areas of theranostic tool development.

The Unstable Carotid Plaque

Carotid revascularization is performed to prevent cerebrovascular events in patients with symptomatic (>50%) and asymptomatic high degree (>70%) carotid stenosis. As this operation carries significant risks for perioperative stroke, careful selection of patients who will benefit from the procedure is essential. Certain plaque characteristics, including texture, are associated with increased tendency for rupture and can be used to identify high-risk patients. Medical therapy, carotid endarterectomy, and carotid stenting are the mainstays for patient management. With careful selection of patients, all anesthesia techniques (general anesthesia, monitored anesthesia care, and regional anesthesia) can be used safely for these revascularization procedures.

The utility of ultrasound and computed tomography in the assessment of carotid artery plaque vulnerability-A mini review

As the burden of cardiovascular and cerebrovascular events continues to increase, emerging evidence supports the concept of plaque vulnerability as a strong marker of plaque rupture, and embolization. Qualitative assessment of the plaque can identify the degree of plaque instability. Ultrasound and computed tomography (CT) have emerged as safe and accurate techniques for the assessment of plaque vulnerability. Plaque features including but not limited to surface ulceration, large lipid core, thin fibrous cap (FC), intraplaque neovascularization and hemorrhage can be assessed and are linked to plaque instability.

NOX4 mRNA correlates with plaque stability in patients with carotid artery stenosis

Carotid artery stenosis (CAS) develops from atherosclerotic lesions and plaques. Plaque rupture or stenosis may result in occlusion of the carotid artery. Accordingly, the asymptomatic disease becomes symptomatic, characterized by ischemic stroke or transient ischemic attacks, indicating an urgent need for better understanding of the underlying molecular mechanisms and eventually prevent symptomatic CAS. NOX4, a member of the NADPH oxidase family, has anti-atherosclerotic and anti-inflammatory properties in animal models of early atherosclerosis. We hypothesized that NOX4 mRNA expression is linked to protective mechanisms in CAS patients with advanced atherosclerotic lesions as well. Indeed, NOX4 mRNA expression is lower in patients with symptomatic CAS. A low NOX4 mRNA expression is associated with an increased risk of the development of clinical symptoms. In fact, NOX4 appears to be linked to plaque stability, apoptosis and plaque hemorrhage. This is supported by cleaved caspase-3 and glycophorin C and correlates inversely with plaque NOX4 mRNA expression. Even healing of a ruptured plaque appears to be connected to NOX4, as NOX4 mRNA expression correlates to fibrous cap collagen and is reciprocally related to MMP9 activity. In conclusion, low intra-plaque NOX4 mRNA expression is associated with an increased risk for symptomatic outcome and with reduced plaque stabilizing mechanisms suggesting protective effects of NOX4 in human advanced atherosclerosis.

Assessment of plaque vulnerability in carotid atherosclerotic plaques using contrast-enhanced ultrasound

Background

Atherosclerotic carotid plaques are one of the most important causes of stroke. Apart from the severity of stenosis, there are certain plaque characteristics such as neovascularization and, surface ulceration which makes a plaque vulnerable. This study was performed to study the plaque characteristics using contrast-enhanced ultrasound (CEUS) and evaluate their association with presence of ischemic cerebrovascular symptoms in these patients.

Methods

This study included patients presenting at a tertiary care center, having carotid plaques causing >60% stenosis. CEUS was performed for assessment of intraplaque neovascularity and plaque surface characteristics. These plaque features were then evaluated for their association with presence of ischemic cerebrovascular symptoms in patients.

Results

Sixty plaques were studied in 50 patients. Thirty-two plaques were associated with ischemic cerebrovascular symptoms. On CEUS, intraplaque neovascularization was seen in 38 of the 60 plaques studied (63.3%). There was statistically significant association of intraplaque neovascularity and plaque surface characteristics with presence of ischemic cerebrovascular symptoms.

Conclusion

CEUS allows better characterization of plaque surface characteristics and also depicts plaque neovascularization, which helps in determining the plaque vulnerability. It should be used as an adjunct to ultrasound and doppler assessment of carotid plaques.

CT Marker in Emergency Imaging of Acute Basilar Artery Occlusion: Thrombosis vs. Embolism

Purpose: Acute basilar artery occlusion, a neurovascular emergency leading to high rates of morbidity and mortality, is usually diagnosed by CT imaging. The outcome is partly dependent on etiology, with a worse outcome in occlusions with underlying basilar artery stenosis. As this occlusion type requires a more complex angiographic therapy, this study aimed to develop new CT markers in emergency admission imaging to rapidly identify underlying stenosis. Methods: A total of 213 consecutive patients (female n = 91, age in years (mean/SD/range): 72/13/28−97), who received endovascular treatment at a single comprehensive stroke center for acute basilar artery occlusion, were included in this study. After applying strict inclusion criteria for imaging analyses, novel CT imaging markers, such as ‘absolute density loss’ (ADL) and relative thrombus attenuation (CTA-index), that measure perviousness, were assessed for n = 109 patients by use of CT-angiography and correlated to different occlusion patterns (thrombotic vs. embolic). Inter-observer agreement was assessed using an intraclass correlation coefficient for independent measures of a radiologist and a neuroradiologist. Associations between the imaging markers and clinical and interventional parameters were tested. Results: CT markers differ between the subgroups of basilar artery occlusions with and without underlying stenosis (for ADL: 169 vs. 227 HU (p = 0.03), for CTA-index: 0.55 vs. 0.70 (p < 0.001)), indicating a higher perviousness in the case of stenosis. A good inter-rater agreement was observed for ADL and CTA-index measures (ICC 0.92/0.88). For the case of embolic occlusions, a more pervious thrombus correlates to shorter time intervals, longer procedure times, and worse reperfusion success (p-values < 0.05, respectively). Conclusions: ADL and CTA-index are easy to assess in the emergency setting of acute basilar artery occlusion with the use of routinely acquired CT-angiography. They show a high potential to differentiate thrombotic from embolic occlusions, with an impact on therapeutic decisions and angiographic procedures. Measurements can be quickly performed with good reliability, facilitating implementation in clinical practice.

Molecular Imaging of Vulnerable Coronary Plaque with Radiolabeled Somatostatin Receptors (SSTR)

Atherosclerosis is responsible for the majority of heart attacks and is characterized by several modifications of the arterial wall including an inflammatory reaction. The silent course of atherosclerosis has made it necessary to develop predictors of disease complications before symptomatic lesions occur. Vulnerable to rupture atherosclerotic plaques are the target for molecular imaging. To this aim, different radiopharmaceuticals for PET/CT have emerged for the identification of high-risk plaques, with high specificity for the identification of the cellular components and pathophysiological status of plaques. By targeting specific receptors on activated macrophages in high-risk plaques, radiolabelled somatostatin analogues such as ⁶⁸Ga-DOTA-TOC, TATE,0 or NOC have shown high relevance to detect vulnerable, atherosclerotic plaques. This PET radiopharmaceutical has been tested in several pre-clinical and clinical studies, as reviewed here, showing an important correlation with other risk factors.

Vascular Imaging Techniques to Diagnose and Monitor Patients with Takayasu Arteritis: A Review of the Literature

Takayasu arteritis (TA) is a large vessel vasculitis that causes stenosis, occlusion, and sometimes the aneurysm of the aorta and its major branches. TA often occurs in young women, and because the symptoms are not obvious in the early stages of the disease, diagnosis is difficult and often delayed. In approximately 10% to 20% of patients, TA is reportedly complicated by ischemic stroke or transient ischemic attack. It is important to diagnose TA early and provide appropriate treatment to prevent complications from stroke. Diagnostic imaging techniques to visualize arterial stenosis are widely used in clinical practice. Even if no signs of cerebrovascular events are present at the time of the most recent evaluation of patients with TA, follow-up vascular imaging is important to monitor disease progression and changes in the cerebrovascular risk. However, the optimal imaging technique for monitoring of TA has not been established. Therefore, the purpose of this review is to describe newly available evidence on the usefulness of conventional imaging modalities (digital subtraction angiography, computed tomography angiography, magnetic resonance imaging/angiography, duplex ultrasound, and positron emission tomography) and novel imaging modalities (optical coherence tomography, infrared thermography, contrast-enhanced ultrasonography, and superb microvascular imaging) in the diagnosis and monitoring of TA.

The Course of Carotid Plaque Vulnerability Assessed by Advanced Neurosonology

Background: Carotid artery atherosclerosis is a major risk factor for ischemic stroke. This risk is related to plaque vulnerability and is characterized by plaque morphology, intraplaque neovascularization, and cerebral microembolization. Advanced neurosonology can identify vulnerable plaques and aid in preventing subsequent stroke. We aimed to assess the time course of cerebral microembolization and intraplaque neovascularization during 6 months of follow-up and to explore the utility of advanced neurosonology in patients with acute cerebral ischemia.

Methods: Fifteen patients with acute cerebral ischemia and carotid artery plaques underwent comprehensive extra- and intracranial ultrasound examinations, including microemboli detection and contrast-enhanced ultrasound. The examinations were repeated after 3 and 6 months.

Results: We examined 28 plaques in 15 patients. The ultrasonographic features of plaque vulnerability were frequent in symptomatic and asymptomatic plaques. There were no significant differences in stenosis degree, plaque composition, plaque surface, neovascularization, or cerebral microembolization between symptomatic and asymptomatic plaques, but symptomatic plaques had a higher number of vulnerable features. None of the patients had recurrent clinical stroke or transient ischemic attack during the follow-up period. We observed a decrease in cerebral microembolization at 6 months, but no significant change in intraplaque neovascularization.

Conclusions: In patients with acute cerebral ischemia and carotid artery plaques, cerebral microembolization decreased during 6 months of follow-up, indicating plaque stabilization.

Clinical Trial Registration:ClinicalTrial.gov, identifier NCT02759653.

New insight into biology, molecular diagnostics and treatment options of unstable carotid atherosclerotic plaque: a narrative review

Indications for intervention in hemodynamically relevant carotid artery stenosis (carotid endarterectomy or stenting) are primarily based on a degree of stenosis and symptomatology. To date the plaque vulnerability is rarely taken into account in clinical decision making although development of molecular imaging allows a better understanding of plaque biology and provides new techniques detecting potentially vulnerable plaque at risk. A significant number of reports describing the mechanisms of unstable plaque formation suggest that it is a multifactorial process. Inflammation, lipid accumulation, apoptosis, proteolysis, the thrombotic process and angiogenesis are among the main factors of carotid plaque destabilization. Although inflammation is a key process in development of plaque vulnerability, the hemostasis and neoangiogenesis should be regarded as equally important. Only a small group of asymptomatic patients may benefit from the invasive treatment and it remains a challenge to determine whether initially asymptomatic carotid plaque become unstable or vulnerable. Currently, the main task of research on atherosclerotic lesion imaging is focused on functional state of the plaque. The presence of one or more features such as stenosis progression, large plaque area, large juxta-luminal black area, plaque echolucency, intra-plaque hemorrhage, impaired cerebral vascular reserve and spontaneous embolization may indicate patients at higher risk for stroke suitable for revascularization. Treatment of carotid stenosis as one of the manifestations of generalized atherosclerosis requires a broad approach. Nowadays pharmacological treatment options for the atherosclerotic process are largely aimed at stimulating the plaque stabilization, but in symptomatic patients and selected asymptomatic patients, carotid plaque should be removed as a potential source of embolism.

Cardiovascular Risk Factors Affect Specific Segments of the Intracranial Vasculature in High-Resolution (HR) Vessel Wall Imaging (VWI)

OBJECTIVES

Luminal-based imaging have identified different risk factors for extracranial and intracranial atherosclerosis (ICAS), but these techniques are known to underestimate the true extent of the disease. High-resolution (HR) vessel wall imaging (VWI) has recently gained recognition as a valuable tool in the assessment of ICAS. The aim of this study is to determine the association between cardiovascular risk factors and specific intracranial vessel segment involvement using HR-VWI.

MATERIALS AND METHODS

From January 2017 to January 2020, consecutive patients ≥ 18 years-old undergoing HR-VWI of the brain were identified. Patients with history of primary or secondary vasculitis, reversible cerebral vasoconstriction syndrome, or moya-moya were excluded. The presence of vessel wall thickening and enhancement were assessed in the perpendicular plane for each vessel segment by two neuroradiologists. Univariate and multivariate analyses were performed to assess associations between imaging findings and cardiovascular risk factors. Interrater reliability was calculated.

RESULTS

Seventy-one patients (39 men; mean age: 55.9 years) were included. Vessel wall enhancement was seen in 39/71 (55%). A total number of 105 vessel segments demonstrated abnormal enhancement and 79/105 (75%) had an eccentric pattern. Eccentric vessel wall enhancement was independently associated with age >65 years-old in the ICA (OR 9.0, CI 2.1 - 38.2, p < 0.01) and proximal MCA (OR 4.0, CI 1.2 - 13.2, p = 0.02), and with hyperlipidemia in the posterior circulation (OR 44.0, CI2.9-661.0, p<0.01).

CONCLUSION

There is a significant association between eccentric vessel wall enhancement of the ICA and proximal MCA in patients with age > 65; and of the proximal posterior circulation (basilar - PCA1) with hyperlipidemia.

An advanced ultrasound application used to assess peripheral vascular diseases: superb microvascular imaging

Over the past several years, a novel ultrasound imaging modality termed superb microvascular imaging (SMI) has enabled visualization of microvessels. SMI ultrasound studies of peripheral artery diseases have significantly extended our knowledge of tissue microcirculation and the arterial microenvironments of atherosclerotic lesions. We here present an overview of current knowledge on the utility of SMI assessment of vascular diseases and highlight certain peripheral microcirculation disorders for which SMI is particularly valuable. The evidence indicates that SMI can detect intraplaque neovascularization and usefully assess carotid plaque vulnerability; vascularization of the carotid arterial wall detected by SMI is a potential marker of disease activity in patients with Takayasu arteritis; SMI reveals the foot microcirculation and yields a quantitative vascular index (in line with the angiosome concept); and, SMI may serve as an auxiliary diagnostic modality for hereditary hemorrhagic telangiectasia and Raynaud syndrome. In general, microcirculatory evaluation by SMI is an attractive field for future research on therapeutic strategies for peripheral vascular diseases.

Cervical Carotid Plaque MRI : Review of Atherosclerosis Imaging Features and their Histologic Underpinnings

Magnetic resonance (MR) imaging is considered the gold standard for non-invasive evaluation of carotid artery plaque morphology and composition. A number of studies have demonstrated the clinical utility of MR plaque imaging in the risk stratification of carotid atherosclerotic disease, determination of stroke etiology, and identification of surgical and endovascular candidates for carotid revascularization procedures. The MR plaque imaging also provides researchers and clinicians with valuable insights into the pathogenesis, natural history and composition of carotid atherosclerotic disease. Nevertheless, the field of MR plaque imaging is complex, and requires a thorough knowledge of the histologic basis for how various plaque features appear on imaging. This article details the pathogenesis and histology of atherosclerosis, reviews the expected appearance of different plaque components, and describes how MR imaging features may be related to symptomatology or predict future ischemic events.

Correlation between calcium, water contents and ultrasonographic appearance of atherosclerotic lesions of carotid artery lesions

Background

We tested the hypothesis whether there is a correlation between the echogenicity and calcium and water contents of carotid plaques.

Patients and methods

Ninety carotid befurcations from 45 deceased patients were removed during autopsy. Thirty-four plaques were categorized as homogenous echolucent (HEL), homogenous echogenic (HEG) and heterogenous (HE) plaques based on premortem B-mode image. Water content was expressed in % of wet weight. Ca was determined by proton-induced X-ray emission and expressed in ppm. Relative optical density of the B-mode images was analyzed offline using a computer program.

Results

HEL plaques had lower Ca content (medians and IQRs: 6,145 [4,465–6,536 ppm]) compared to HEG (74,100 [15,300–1,44,500−ppm]), P ≤ 0.001). HE plaques showed an intermediate calcium content (7,310 [4,840–9,920 ppm]) that was statistically not different from echolucent plaques. Water content of HEG plaques was statistically not different from HEL and HE (HEG:53.5 [35.5–64%], HEL: 73.5 [69.7–78.5%], HE: 70.6 [67.4–73.9%]). HEG plaques had the highest relative optical densities (196 [188–217%]). HEL and HE had similar relative optical densities (HEL: 176 [164–187%], HE: 164 [144–188%], respectively). A significant positive correlation was found between the Ca content and relative optical density of plaques.

Conclusions

Echogenicity of carotid plaques increases along with their calcium content. Water content may be an important factor in differentiation of different plaques.

Studying the Factors of Human Carotid Atherosclerotic Plaque Rupture, by Calculating Stress/Strain in the Plaque, Based on CEUS Images: A Numerical Study

Carotid plaque neovascularization is one of the major factors for the classification of vulnerable plaque, but the axial force effects of the pulsatile blood flow on the plaque with neovessel and intraplaque hemorrhage was unclear. Together with the severity of stenosis, the fibrous cap thickness, large lipid core, and the neovascularization followed by intraplaque hemorrhage (IPH) have been regarded as high-risk features of plaque rupture. In this work, the effects of these factors were evaluated on the progression and rupture of the carotid atherosclerotic plaques. Five geometries of carotid artery plaque were developed based on contrast-enhanced ultrasound (CEUS) images, which contain two types of neovessel and IPH, and geometry without neovessel and IPH. A one-way fluid-structure interaction model was applied to compute the maximum principal stress and strain in the plaque. For that hyper-elastic and non-linear material, Yeoh 3rd Order strain energy density function was used for components of the plaque. The simulation results indicated that the maximum principal stress of plaque in the carotid artery was higher when the degree of the luminal stenosis increased and the thickness of the fibrous cap decreased. The neovessels within the plaque could introduce a 2.5% increments of deformation in the plaque under the pulsatile blood flow pressure. The IPH also contributed to the increased risk of plaque rupture that a gain of stress was 8.983, 14.526, and 34.47 kPa for the plaque with 50, 65, and 75%, respectively, when comparing stress in the plaque with IPH distributed at the middle to the shoulder of the plaque. In conclusion, neovascularization in the plaque could reduce the stability of the plaque by increasing the stress within the plaque. Also, the risk of plaque rupture increased when large luminal stenosis, thin fibrous cap, and IPH were observed.

Carotid intraplaque haemorrhage: pathogenesis, histological classification, imaging methods and clinical value

Vulnerable carotid atherosclerotic plaques are characterised by several risk factors, such as inflammation, neovascularization and intraplaque haemorrhage (IPH). Vulnerable plaques can lead to ischemic events such as stroke. Many studies reported a relationship between IPH, plaque rupture, and ischemic stroke. Histology is the gold standard to evaluate IPH, but it required carotid endarterectomy (CEA) surgery to collect the tissue sample. In this context, several imaging methods can be used as a non-invasive way to evaluate plaque vulnerability and detect IPH. Most imaging studies showed that IPH is associated with plaque vulnerability and stroke, with magnetic resonance imaging (MRI) being the most sensitive and specific to detect IPH as a predictor of ischemic events. These conclusions are however still debated because of the limited number of patients included in these studies; further studies are required to better assess risks associated with different IPH stages. Moreover, IPH is implicated in plaque vulnerability with other risk factors which need to be considered to predict ischemic risk. In addition, MRI sequences standardization is required to compare results from different studies and agree on biomarkers that need to be considered to predict plaque rupture. In these circumstances, IPH detection by MRI could be an efficient clinical method to predict stroke. The goal of this review article is to first describe the pathophysiological process responsible for IPH, its histological detection in carotid plaques and its correlation with plaque rupture. The second part will discuss the benefits and limitations of imaging the carotid plaque, and finally the clinical interest of imaging IPH to predict plaque rupture, focusing on MRI-IPH.

Contrast-Enhanced Ultrasound: Identification of Neovascularization Permits Characterization of Vulnerable Carotid Plaques

Objective:

Carotid atherosclerotic vascular disease (ASVD) represents an ongoing health problem and is responsible for a significant proportion of all cerebral ischemic events (CIEs).

Method:

A review of the literature was performed on the application of contrast-enhanced ultrasound (CEUS) to enhance the diagnosis of ASVD and further avoid CIEs.

Results:

Cerebral ischemic events are those resulting from reduction or cessation of perfusion to localized regions of the brain made manifest by neurological, typically stroke-like, symptoms. Traditional triplex ultrasound evaluation is a reliable and widely established method of identifying carotid ASVD lesions and grading the accompanying degree of focal stenoses and their hemodynamic impact. While this information plays an integral role in determining management of patients with significant carotid ASVD, it is less useful in classifying individual lesions as “vulnerable” or not. Vulnerable lesions are those that, based on their histological and morphological features, predispose a patient to an increased risk of a CIE due to plaque or thrombus embolization.

Conclusions:

The addition of CEUS to carotid artery diagnostic studies offers new potential in identifying vulnerable plaques and predicting which patients will progress to sequelae associated with a cerebral ischemic event.

Insight from imaging on plaque vulnerability: similarities and differences between coronary and carotid arteries-implications for systemic therapies

Nowadays it is widely accepted that the rupture of the atherosclerotic plaque in coronary and carotid arteries plays a fundamental role in the development of acute myocardial infarctions or cerebrovascular events. In recent years, imaging techniques have explored, with a new level of detail, the atherosclerotic disease generating new evidences that some plaque characteristics are significantly associated to the risk of rupture and subsequent thrombosis or embolization. Moreover, the recent evidence of the anti-atherosclerotic effects determined by lipid-lowering and anti-inflammatory therapies poses a challenge for the choice of therapeutic approaches (best/optimal medical therapy vs. revascularization), maximized by the evidence that coronary and carotid atherosclerosis share common patterns but also differ regarding some important features. In this Review, we discuss the similarities and differences between coronary and carotid artery vulnerable plaque from the imaging point of view and the potential implications for systemic therapies according to the emerging evidence.

Contrast imaging ultrasound for the detection and characterization of carotid vulnerable plaque

Not only the degree of luminal narrowing but also the plaque morphology and composition play an important role in risk stratification of carotid atherosclerotic lesions. During the last few years, carotid contrast-enhanced ultrasound (CEUS) has emerged as a valuable imaging tool to assess such vulnerable carotid plaques. This review article discussed the use of CEUS for the detection of carotid plaque irregularities and ulcerations as well as the quantification of intraplaque neovascularization and its correlation with histology and inflammatory biomarkers. Apart from evaluating for markers of vulnerable carotid plaques, CEUS enhancement is directly associated with past cerebrovascular events. More importantly, preliminary evidence has shown that CEUS could be used to predict future cerebrovascular and cardiovascular events. Despite the progress in CEUS imaging for carotid atherosclerotic disease, past studies still suffer from the retrospective nature, small sample size, and a lack of matched, well controlled prospective studies. In the future, large multi-center prospective studies addressing the relationship between CEUS findings and patient clinical outcomes in carotid atherosclerotic disease are warranted.

Imaging of intracranial atherosclerotic plaques using 3.0 T and 7.0 T magnetic resonance imaging-current trends and future perspectives

Intracranial atherosclerotic disease (ICAD) is one of the most common causes of ischemic stroke and carries a relatively high risk of stroke recurrence. Advances in high-resolution magnetic resonance imaging (HRMRI) techniques of intracranial arteries now have made it possible to directly visualize atherosclerotic plaque itself, allowing detailed assessments of plaque morphology and components. Currently available intracranial HRMRI could be performed with 2-dimensional (2D) and 3D acquisitions, and multicontrast weightings in clinically reasonable scan times. Until now, HRMRI research of ICAD has focused on the identification of plaque vulnerability, and the relationship between plaque characteristics and ischemic stroke. HRMRI at ultra-high-field strength (7.0 T) holds promise in better visualizing intracranial vessel walls, as well as identifying early lesions and total burden of ICAD. As a result, intracranial HRMRI provides great insights into pathology of intracranial atherosclerotic plaques, stroke mechanisms, and future stroke risk. In this article, we will review the technical implementation, preclinical research, clinical applications, and future directions of HRMRI for the evaluation of ICAD at 3.0 T and 7.0 T.

Evaluation of Carotid Plaque Rupture and Neovascularization by Contrast-Enhanced Ultrasound Imaging: an Exploratory Study Based on Histopathology

A significant portion of ischemic stroke is on account of emboli caused by fibrous cap rupture of vulnerable plaque with intraplaque neovascularization as a significant triggering factor to plaque vulnerability. Contrast-enhanced ultrasound (CEUS) could offer detailed information on plaque surface and intraplaque microvascular. This study aims to comprehensively assess the value of CEUS for the detection of plaque rupture and neovascularization in histologically verified plaques that had been removed from the patients who had undergone carotid endarterectomy (CEA). Fifty-one consecutive subjects (mean age, 67.0 ± 6.5 years; 43 [84.3%] men) scheduled for CEA were recruited. Standard ultrasound and CEUS were performed prior to surgery. Based on the direction of the contrast agents that diffuse within the plaques, plaques were divided as "inside-out" direction (contrast agents diffuse from the artery lumen towards the inside of the plaque) and non-inside-out direction. Plaque enhancement was assessed by using a semi-quantitative grading scale (grade 1: no enhancement; grade 2: moderate enhancement; grade 3: extensive enhancement). Plaques were evaluated for histopathologic characteristics according to Oxford Plaque Study (OPS) standard postoperative. Intraplaque neovascularization as manifested by the appearance of CD34-positive microvessels was characterized in terms of microvessel density (MVD), microvessel area (MVA), and microvessel shape (MVS). In 51 plaques, the sensitivity, specificity, positive, and negative predictive values of contrast agent inside-out direction diffusion for the detection of plaque fibrous cap rupture were 87.5%, 92.6%, 91.3%, and 89.3%, respectively. The incidence of cap rupture was significantly higher in contrast agent inside-out direction diffusion than non-inside-out direction diffusion (73.9% vs 25.0%, p < 0.001), and inside-out direction diffusion did exhibit higher frequency of vulnerable plaques (OPS grades 3-4) (95.7% vs 53.6%, p = 0.001). Multivariate logistic regression analysis revealed the contrast agent inside-out direction diffusion as an independent correlate to plaque rupture (OR 8.5, 95% CI 2.4-30.1, p = 0.001). With increasing plaque enhancement, plaque MVD (p < 0.001), plaque MVA (p = 0.012), and percentage of highly irregular-shaped microvessels increased (p < 0.001). Contrast agent inside-out direction diffusion could indicate plaque rupture. The increase in plaque enhancement paralleled increased, larger, and more irregular-shaped microvessels, which may suggest an increased risk of plaque vulnerability.

Integrated cardiovascular assessment of atherosclerosis using PET/MRI

Atherosclerosis is a systemic inflammatory disease typified by the development of lipid-rich atheroma (plaques), the rupture of which are a major cause of myocardial infarction and stroke. Anatomical evaluation of the plaque considering only the degree of luminal stenosis overlooks features associated with vulnerable plaques, such as high-risk morphological features or pathophysiology, and hence risks missing vulnerable or ruptured non-stenotic plaques. Consequently, there has been interest in identifying these markers of vulnerability using either MRI for morphology, or positron emission tomography (PET) for physiological processes involved in atherogenesis. The advent of hybrid PET/MRI scanners offers the potential to combine the strengths of PET and MRI to allow comprehensive assessment of the atherosclerotic plaque. This review will discuss the principles and technical aspects of hybrid PET/MRI assessment of atherosclerosis, and consider how combining the complementary modalities of PET and MRI has already furthered our understanding of atherogenesis, advanced drug development, and how it may hold potential for clinical application.

Association between Pericytes in Intraplaque Neovessels and Magnetic Resonance Angiography Findings

(1) Background: Pericytes are involved in intraplaque neovascularization of advanced and complicated atherosclerotic lesions. However, the role of pericytes in human carotid plaques is unclear. An unstable carotid plaque that shows high-intensity signals on time-of-flight (TOF) magnetic resonance angiography (MRA) is often a cause of ischemic stroke. The aim of the present study is to examine the relationship between the pericytes in intraplaque neovessels and MRA findings. (2) Methods: A total of 46 patients with 49 carotid artery stenoses who underwent carotid endarterectomy at our hospitals were enrolled. The patients with carotid plaques that were histopathologically evaluated were retrospectively analyzed. Intraplaque hemorrhage was evaluated using glycophorin A staining, and intraplaque neovessels were evaluated using CD34 (Cluster of differentiation) stain as an endothelial cell marker or NG2 (Neuron-glial antigen 2) and CD146 stains as pericyte markers. Additionally, the relationships between the TOF-MRA findings and the carotid plaque pathologies were evaluated. (3) Results: Of the 49 stenoses, 28 had high-intensity signals (TOF-HIS group) and 21 had iso-intensity signals (TOF-IIS group) on TOF-MRA. The density of the CD34-positive neovessels was equivalent in both groups. However, the NG2- and CD146-positive neovessels had significantly higher densities in the TOF-HIS group than in the TOF-IIS group. (4) Conclusion: The presence of a high-intensity signal on TOF-MRA in carotid plaques was associated with intraplaque hemorrhage and few pericytes in intraplaque neovessels. These findings may contribute to the development of new therapeutic strategies focusing on pericytes.

From Perviousness to Plaque Imaging in Acute Basilar Occlusions

Background and Purpose—

Recent studies show that mechanical thrombectomy of acute basilar artery occlusions (BAO) results in high rates of successful recanalization and good outcomes, but predictors are not completely established yet. Varying occlusion types may benefit differently, and especially, an underlying basilar stenosis (BS) seems to have an impact. Aim of this study was to investigate angiographic and clinical differences in BAO subtypes and to test the potential of perviousness measures for a preinterventional identification of clinically relevant different occlusion types.

Methods—

All consecutive patients with acute BAO, endovascular treated at a single comprehensive stroke center, were included. Different occlusion patterns, especially underlying BS, were identified and analyzed in respect of angiographic and clinical (National Institutes of Health Stroke Scale/modified Rankin Scale) outcome parameters (N=115). Thrombus perviousness measures (change in thrombus attenuation Δt and corrected void fraction ε) were assessed in admission computed tomography imaging and correlated to different etiological subgroups.

Results—

Despite comparable rates of successful recanalization (87% for BAO with BS versus 95% without BS), the BS group showed worse clinical outcome with higher National Institutes of Health Stroke Scale/modified Rankin Scale values ( P =0.002/0.003). The group of BS turned out to have lower thrombus density values in unenhanced scans (mean, 42.0 Hounsfield units) and higher perviousness measures Δt (mean, 34.6 Hounsfield units) and ε (mean, 0.23) than thrombi without an underlying BS (mean, 53.6 Hounsfield units/13.1 Hounsfield units/0.08, P =0.01/ 0.004/ 0.001).

Conclusions—

In agreement with previous studies, outcome of mechanical thrombectomy of BAO seems to depend on pathogenesis with less clinical benefit for underlying BS, raising the question of early identification of this subgroup. Perviousness showed a high potential to differentiate acute BAO with and without BS, possibly usable as an admission imaging marker for BS.

Carotid Vessel Wall Imaging on CTA

Vessel wall imaging has been increasingly used to characterize plaque beyond luminal narrowing to identify patients who may be at the highest risk of cerebrovascular ischemia. Although detailed plaque information can be obtained from many imaging modalities, CTA is particularly appealing for carotid plaque imaging due to its relatively low cost, wide availability, operator independence, and ability to discern high-risk features. The present Review Article describes the current understanding of plaque characteristics on CTA by describing commonly encountered plaque features, including calcified and soft plaque, surface irregularities, neovascularization, and inflammation. The goal of this Review Article was to provide a more robust understanding of clinically relevant plaque features detectable on routine CTA of the carotid arteries.

Antithrombotic Therapy in Carotid Artery Disease

The management of asymptomatic atherosclerotic carotid artery disease and the role of antithrombotic therapy is of increasing importance for stroke prevention. Non-invasive imaging of carotid plaques can identify high-risk plaque features that are associated with the risk of plaque rupture. Carotid plaque necrosis, hemorrhage, fibrous cap thinning, and the presence of foam cells have all been correlated with the risk of rupture and onset of neurological symptoms in patients with carotid stenosis. Antiplatelets are currently recommended for patients with a history of ischemic stroke and/or significant carotid artery stenosis, with aspirin and clopidogrel being the most widely used and studied agents. The role of dual antiplatelet therapy remains controversial. Moreover, there is scarce evidence on the role of newer anticoagulant agents in stable patients with carotid artery stenosis. In this review article, we discuss the pathophysiology of carotid atherosclerosis, the use of non-invasive imaging for detecting the vulnerable carotid plaque and summarize the existing clinical evidence on the use of antiplatelet and antithrombotic agents in carotid artery disease.

Angiogenic Abnormalities in Diabetes Mellitus: Mechanistic and Clinical Aspects

CONTEXT

Diabetes causes severe pathological changes to the microvasculature in many organs and tissues and is at the same time associated with an increased risk of coronary and peripheral macrovascular events. We herein review alterations in angiogenesis observed in human and experimental diabetes and how they contribute to diabetes onset and development of vascular complications.

EVIDENCE ACQUISITION

The English language medical literature was searched for articles reporting on angiogenesis/vasculogenesis abnormalities in diabetes and their clinical manifestations, mechanistic aspects, and possible therapeutic implications.

EVIDENCE SYNTHESIS

Angiogenesis is a complex process, driven by a multiplicity of molecular mechanisms and involved in several physiological and pathological conditions. Incompetent angiogenesis is pervasive in diabetic vascular complications, with both excessive and defective angiogenesis observed in various tissues. A striking different angiogenic response typically occurs in the retina vs the myocardium and peripheral circulation, but some commonalities in abnormal angiogenesis can explain the well-known association between microangiopathy and macroangiopathy. Impaired angiogenesis can also affect endocrine islet and adipose tissue function, providing a link to diabetes onset. Exposure to high glucose itself directly affects angiogenic/vasculogenic processes, and the mechanisms include defective responses to hypoxia and proangiogenic factors, impaired nitric oxide bioavailability, shortage of proangiogenic cells, and loss of pericytes.

CONCLUSIONS

Dissecting the molecular drivers of tissue-specific alterations of angiogenesis/vasculogenesis is an important challenge to devise new therapeutic approaches. Angiogenesis-modulating therapies should be carefully evaluated in view of their potential off-target effects. At present, glycemic control remains the most reasonable therapeutic strategy to normalize angiogenesis in diabetes.

Carotid Plaque Neovascularization Detected With Superb Microvascular Imaging Ultrasound Without Using Contrast Media

Background and Purpose- A significant proportion of ischemic strokes are caused by emboli from unstable carotid artery plaques with intraplaque neovascularization (IPN) as a key feature of plaque instability. IPN is not detectable with conventional Doppler ultrasound. Contrast-enhanced ultrasound (CEUS) can visualize IPN, but its use is limited in clinical practice because it requires an intravenous injection of contrast. Superb microvascular imaging (SMI) without contrast uses an algorithm to remove clutter and motion wall artifacts while preserving low-velocity blood flow signals, enabling visualization of IPN. Our aim was to assess the feasibility of SMI for the detection of IPN. Methods- Thirty-one patients with >50% carotid stenosis were included: 22 patients were symptomatic and 9 asymptomatic. All patients underwent conventional carotid ultrasound, CEUS, SMI, and blood tests. CEUS and SMI findings were compared and correlated to histological plaque assessments after endarterectomy. Results- There was significant positive correlation between an IPN visual 5-level classification of SMI and a semiquantitative analysis of CEUS (P<0.001, r=0.911). Plaques with higher SMI grades had higher numbers of neovessels quantified at histology (P=0.041, r=0.460). Hypoechoic plaques had higher grades of IPN on both CEUS and SMI (P<0.001). Higher visual IPN counts on SMI were associated with (1) increased areas of inflammation (P=0.043, r=0.457), (2) combined rank scores of granulation tissue, inflammation and lipids (P=0.02, r=0.494) at histology, and (3) higher peak-intensity values on quantitative CEUS (P=0.042, r=0.514). Conclusions- SMI ultrasound can detect neovascularization with accuracy comparable to CEUS, suggesting SMI to be a promising noninvasive alternative to CEUS for the assessment of carotid plaque stability.

Possible involvement of pericytes in intraplaque hemorrhage of carotid artery stenosis

OBJECTIVE

Intraplaque hemorrhage (IPH) is most often caused by the rupture of neovessels; however, the factors of intraplaque neovessel vulnerability remain unclear. In this study, the authors focused on pericytes and aimed to investigate the relationship between IPH and pericytes.

METHODS

The authors retrospectively analyzed the medical records of all patients with carotid artery stenoses who had undergone carotid endarterectomy at their hospitals between August 2008 and March 2016. Patients with carotid plaques that could be evaluated histopathologically were eligible for study inclusion. Intraplaque hemorrhage was analyzed using glycophorin A staining, and patients were divided into the following 2 groups based on the extent of granular staining: high IPH (positive staining area > 10%) and low IPH (positive staining area ≤ 10%). In addition, intraplaque neovessels were immunohistochemically evaluated using antibodies to CD34 as an endothelial cell marker or antibodies to NG2 and CD146 as pericyte markers. The relationship between IPH and pathology for intraplaque neovessels was investigated.

RESULTS

Seventy of 126 consecutive carotid stenoses were excluded due to the lack of a specimen for histopathological evaluation; therefore, 53 patients with 56 carotid artery stenoses were eligible for study inclusion. Among the 56 stenoses, 37 lesions had high IPH and 19 had low IPH. The number of CD34-positive neovessels was equivalent between the two groups. However, the densities of NG2- and CD146-positive neovessels were significantly lower in the high IPH group than in the low IPH group (5.7 ± 0.5 vs. 17.1 ± 2.4, p < 0.0001; 6.6 ± 0.8 vs. 18.4 ± 2.5, p < 0.0001, respectively).

CONCLUSIONS

Plaques with high IPH are associated with fewer pericytes in the intraplaque neovessels. This finding may help in the development of novel therapeutic strategies targeting pericytes.

Symptomatic Carotid Plaques Demonstrate Less Leaky Plaque Microvasculature Compared With the Contralateral Side: A Dynamic Contrast-Enhanced Magnetic Resonance Imaging Study

Background

Rupture of a vulnerable carotid atherosclerotic plaque is an important underlying cause of ischemic stroke. Increased leaky plaque microvasculature may contribute to plaque vulnerability. These immature microvessels may facilitate entrance of inflammatory cells into the plaque. The objective of the present study is to investigate whether there is a difference in plaque microvasculature (the volume transfer coefficient K^trans) between the ipsilateral symptomatic and contralateral asymptomatic carotid plaque using noninvasive dynamic contrast‐enhanced magnetic resonance imaging.

Methods and Results

Eighty‐eight patients with recent transient ischemic attack or ischemic stroke and ipsilateral >2 mm carotid plaque underwent 3 T magnetic resonance imaging to identify plaque components and to determine characteristics of plaque microvasculature. The volume transfer coefficient K^trans, indicative for microvascular density, flow, and permeability, was calculated for the ipsilateral and asymptomatic plaque, using a pharmacokinetic model (Patlak). Presence of a lipid‐rich necrotic core, intraplaque hemorrhage, and a thin and/or ruptured fibrous cap was assessed on multisequence magnetic resonance imaging. We found significantly lower K^trans in the symptomatic carotid plaque compared with the asymptomatic side (0.057±0.002 min⁻¹ versus 0.062±0.002 min⁻¹; P=0.033). There was an increased number of slices with intraplaque hemorrhage (0.9±1.6 versus 0.3±0.8, P=0.002) and lipid‐rich necrotic core (1.4±1.9 versus 0.8±1.4, P=0.016) and a higher prevalence of plaques with a thin and/or ruptured fibrous cap (32% versus 17%, P=0.023) at the symptomatic side.

Conclusions

K^trans was significantly lower in symptomatic carotid plaques, indicative for a decrease of plaque microvasculature in symptomatic plaques. This could be related to a larger amount of necrotic tissue in symptomatic plaques.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov.uk. Unique identifier: NCT01208025.

Research progress in ultrasound use for the diagnosis and treatment of cerebrovascular diseases

Cerebrovascular diseases pose a serious threat to human survival and quality of life and represent a major cause of human death and disability. Recently, the incidence of cerebrovascular diseases has increased yearly. Rapid and accurate diagnosis and evaluation of cerebrovascular diseases are of great importance to reduce the incidence, morbidity and mortality of cerebrovascular diseases. With the rapid development of medical ultrasound, the clinical relationship between ultrasound imaging technology and the diagnosis and treatment of cerebrovascular diseases has become increasingly close. Ultrasound techniques such as transcranial acoustic angiography, doppler energy imaging, three-dimensional craniocerebral imaging and ultrasound thrombolysis are novel and valuable techniques in the study of cerebrovascular diseases. In this review, we introduce some of the new ultrasound techniques from both published studies and ongoing trials that have been confirmed to be convenient and effective methods. However, additional evidence from future studies will be required before some of these techniques can be widely applied or recommended as alternatives.

Microvasculature and intraplaque hemorrhage in atherosclerotic carotid lesions: a cardiovascular magnetic resonance imaging study

BACKGROUND

The presence of intraplaque haemorrhage (IPH) has been related to plaque rupture, is associated with plaque progression, and predicts cerebrovascular events. However, the mechanisms leading to IPH are not fully understood. The dominant view is that IPH is caused by leakage of erythrocytes from immature microvessels. The aim of the present study was to investigate whether there is an association between atherosclerotic plaque microvasculature and presence of IPH in a relatively large prospective cohort study of patients with symptomatic carotid plaque.

METHODS

One hundred and thirty-two symptomatic patients with ≥2 mm carotid plaque underwent cardiovascular magnetic resonance (CMR) of the symptomatic carotid plaque for detection of IPH and dynamic contrast-enhanced (DCE)-CMR for assessment of plaque microvasculature. Ktrans, an indicator of microvascular flow, density and leakiness, was estimated using pharmacokinetic modelling in the vessel wall and adventitia. Statistical analysis was performed using an independent samples T-test and binary logistic regression, correcting for clinical risk factors.

RESULTS

A decreased vessel wall Ktrans was found for IPH positive patients (0.051 ± 0.011 min- 1 versus 0.058 ± 0.017 min- 1, p = 0.001). No significant difference in adventitial Ktrans was found in patients with and without IPH (0.057 ± 0.012 min- 1 and 0.057 ± 0.018 min- 1, respectively). Histological analysis in a subgroup of patients that underwent carotid endarterectomy demonstrated no significant difference in relative microvessel density between plaques without IPH (n = 8) and plaques with IPH (n = 15) (0.000333 ± 0.0000707 vs. and 0.000289 ± 0.0000439, p = 0.585).

CONCLUSIONS

A reduced vessel wall Ktrans is found in the presence of IPH. Thus, we did not find a positive association between plaque microvasculature and IPH several weeks after a cerebrovascular event. Not only leaky plaque microvessels, but additional factors may contribute to IPH development.

TRIAL REGISTRATION

NCT01208025 . Registration date September 23, 2010. Retrospectively registered (first inclusion September 21, 2010). NCT01709045 , date of registration October 17, 2012. Retrospectively registered (first inclusion August 23, 2011).

Temporal course and implications of intracranial atherosclerotic plaque enhancement on high-resolution vessel wall MRI

PURPOSE

Little is known about the natural history of intracranial atherosclerotic plaque enhancement and its clinical implications. Our objective was to investigate the value of follow-up high-resolution contrast-enhanced vessel wall MRI (VWMRI) for classifying culprit plaques in patients with intracranial atherosclerotic disease (ICAD).

METHODS

Fourteen patients with symptomatic ICAD (50% females; median age 48 years) underwent serial 3T VWMRI. Fifty-five plaques were identified and graded based on the likelihood of having caused the ischemic event (non-culprit, indeterminate, culprit) and degree of enhancement (0, 1, 2) at baseline and follow-up (median follow-up, 140 days). For accuracy analysis, plaque enhancement at baseline and stable or increasing plaque enhancement at follow-up was tested to identify a culprit plaque, and areas under the receiver operating characteristic curves (AUCs) were compared.

RESULTS

In 37/55 (67.3%) plaques, enhancement grade remained unchanged. Lack of enhancement was only seen in non-culprit plaques at baseline, and none developed enhancement over time. Enhancement never changed more than one grade. Thirty-seven percent (10/27) of non-culprit plaques that enhanced decreased in enhancement grade at follow-up, but no culprit plaques decreased in enhancement. AUC of baseline and follow-up plaque enhancement combined was significantly larger than AUC of baseline plaque enhancement alone to identify culprit plaques (0.733 vs. 0.567, p = 0.0001).

CONCLUSION

Contrast enhancement of ICAD can persist months after the ischemic event. Lack of enhancement at baseline or a decrease in enhancement at follow-up suggests that the plaque is not culprit. Persistent enhancement from baseline to follow-up improves accuracy in identifying culprit plaques.

Multiparametric ultrasound evaluation with CEUS and shear wave elastography for carotid plaque risk stratification

PURPOSE

To assess the diagnostic effectiveness of Multiparametric ultrasound (MPUS), which includes color Doppler ultrasound (CDUS), CEUS and Shear wave elastography (SWE), for evaluating carotid plaque as compared with CT-angiography (CTA) and histology.

MATERIALS AND METHODS

Forty-three consecutive patients scheduled to undergo carotid endarterectomy underwent MPUS. Then, after periods ranging from 2 days to 2 weeks, all underwent CTA. Each plaque was classified by means of dedicated scores for CEUS and SWE as compared with CTA features. At surgery, each plaque was removed in a single fragment to facilitate histological analysis, which evaluated 4 features: extension of the lipid core, thickness of the fibrous cap, inflammatory infiltrate (CD68 + and CD3 + markers) and the presence of intraplaque microvessels. For the CEUS, SWE and CTA, the following values for identifying plaque vulnerability were evaluated: sensitivity, specificity, accuracy, negative predictive value (NPV), positive predictive value (PPV) and Area under the curve (AUC). Cohen's kappa was used to evaluate the concordance between measurements in the different imaging methods. A p < 0.05 was considered statistically significant.

RESULTS

At histology, 31 out of 43 plaques were identified as vulnerable because of the presence of at least one of the following criteria: fibrous cap < 200 μm, lipid core, intraplaque hemorrhage, inflammatory infiltrate or intraplaque neovascularization. CTA showed a sensitivity of 87.1%, a specificity of 100%, a PPV of 100%, an NPV of 75% and an AUC of 93.5%. SWE showed a sensitivity of 87.1%, a specificity of 66.7%, a PPV of 87.1%, an NPV of 66.7% and an AUC of 76.9%. CEUS showed a sensitivity of 87.1%, a specificity of 58.3%, a PPV of 84.4%, an NPV of 63.6% and an AUC of 72.7%.

CONCLUSIONS

Multiparametric ultrasound is an effective modality to obtain comprehensive information on carotid plaques. Further studies are needed to determine whether it can be considered a diagnostic standard.

Different ST2 Serum Concentrations in Asymptomatic and Symptomatic Carotid Artery Stenosis

BACKGROUND

ST2 represents an interesting biomarker associated with the progression of atherosclerotic disease.

METHODS

This study aims to detect different ST2 serum concentrations, and intraplaque ST2 expression, in patients with symptomatic and asymptomatic carotid artery stenosis.

RESULTS

The analysis of ST2 expression in the atheromatous plaque did not show any significant difference between symptomatic and asymptomatic patients (39.61 ± 35.97 vs. 38.49 ± 35.26; P = ns). ST2 serum concentrations of asymptomatic and symptomatic patients were statistically different with a concentration of 11.04 ± 8.95 ng/mL and 13.91 ± 8.01 ng/mL, respectively (P = 0.037). We observed statistical difference in serum ST2 levels between asymptomatic and symptomatic patients for cerebrovascular acute disease. No differences have been obtained in intraplaque ST2 expression.

CONCLUSIONS

Soluble serum ST2 levels can be a useful biomarker to identify patients at risk for cerebrovascular events.

[Imaging of neoangiogenesis of internal carotid artery's atherosclerotic plaque by contrast-enhanced sonography and histological examination]

Previously, atherosclerosis was considered a disease accompanied exclusively by lipids accumulation. At present time success of fundamental and experimental science confirmed that atherosclerotic process is also associated with neovascularization and prolonged inflammatory response at all stages of atherogenesis from initial manifestations to thrombotic complications. The cause of atherosclerotic plaque instability is neovascularization, which is accompanied by intra-plaque hemorrhage and damage. Complications of carotid arteries atherosclerosis are strokes and transient ischemic attacks. The use of a wide range of diagnostic and pathohistological techniques is required for assessing this pathology. The most promising diagnostic technique is Contrast Enhanced Ultrasonography (CEUS) which allows to assess neovascularization degree in atherosclerotic plaque through the injection of a contrast agents.

Differential Features of Culprit Intracranial Atherosclerotic Lesions: A Whole-Brain Vessel Wall Imaging Study in Patients With Acute Ischemic Stroke

Background

Intracranial atherosclerotic disease tends to affect multiple arterial segments. Using whole‐brain vessel wall imaging, we sought to study the differences in plaque features among various types of plaques in patients with a recent unilateral anterior circulation ischemic stroke.

Methods and Results

Sixty‐one patients with unilateral anterior circulation ischemic stroke were referred to undergo whole‐brain vessel wall imaging (before and after contrast) within 1 month of symptom onset for intracranial atherosclerotic disease evaluations. Each plaque was classified as a culprit, probably culprit, or nonculprit lesion, according to its likelihood of causing the stroke. The associations between plaque features (thickening pattern, plaque‐wall contrast ratio, high signal on T1‐weighted images, plaque contrast enhancement ratio, enhancement grade, and enhancement pattern) and culprit lesions were estimated using mixed multivariable logistic regression after adjustment for maximum wall thickness. In 52 patients without motion corruption in whole‐brain vessel wall imaging, a total of 178 intracranial plaques in the anterior circulation were identified, including 52 culprit lesions (29.2%), 51 probably culprit lesions (28.7%), and 75 nonculprit lesions (42.1%). High signal on T1‐weighted images (adjusted odds ratio, 9.1; 95% confidence interval, 1.9–44.1; P=0.006), grade 2 (enhancement ratio of plaque ≥ enhancement ratio of pituitary) contrast enhancement (adjusted odds ratio, 17.4; 95% confidence interval, 1.8–164.9; P=0.013), and type 2 (≥50% cross‐sectional wall involvement) enhancement pattern (adjusted odds ratio, 10.1; 95% confidence interval, 1.3–82.2; P=0.030) were independently associated with culprit lesions.

Conclusions

High signal on T1‐weighted images, grade 2 contrast enhancement, and type 2 enhancement pattern are associated with cerebrovascular ischemic events, which may provide valuable insights into risk stratification.

Wenyang Huoxue Jiedu formula inhibits thin-cap fibroatheroma plaque formation via the VEGF/VEGFR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

For many years, Guangzhou University of Chinese Medicine has been successfully using the empirical Wenyang Huoxue Jiedu formula (WHJF) to treat coronary heart disease. Modern theories of acute coronary syndrome mainly focus on rupture of thin-cap fibroatheromas (TCFAs), which is closely related to the release of vascular endothelial growth factor and its receptor (VEGF/VEGFR).

AIM OF STUDY

We investigated the effects of WHJF on the formation of TCFA plaques and the potential mechanism (VEGF/VEGFR signaling pathway).

MATERIALS AND METHODS

For the in vivo experiments, WHJF was administered to ApoE^-/- mice, as a model of TCFA plaque formation. Aortic sections of the mice were obtained, and the vulnerability index and new vessel density of plaques were calculated by the Movat staining assay and immunohistochemistry kit, respectively. Protein and mRNA expression levels of VEGF/VEGFR in aortas were assayed by capillary electrophoresis immunoassay and quantitative real-time polymerase chain reaction analyses. In vitro, WHJF serum was produced in rats on the fourth day 2 h after the first administration of different concentrations of WHJF. Proliferation, migration, and lumen formation ability of human umbilical vein endothelial cells (HUVECs) treated with sera from these rats were assayed by the CKK-8 kit, Transwell plates, and Matrigel assay, respectively. Protein and mRNA expression levels of signaling molecules in the VEGF/VEGFR pathways were also examined.

RESULTS

In vivo, the vulnerability index and new vessel density of plaques in the WHJF group were lower than those values in the blank control group (P < 0.05). No differences were found between the groups in the expression levels of VEGF/VEGFR (P > 0.05). In vitro, the proliferation, migration, and tube formation of HUVECs in the high-dose WHJF group were reduced compared to the control group (P < 0.05). This finding was in agreement with the downregulation of VEGFR-2 and pERK (P < 0.05). The mRNA expression of signaling molecules showed no difference between the groups (P > 0.05).

CONCLUSIONS

WHJF inhibits TCFA formation by influencing the VEGF/VEGFR signaling pathway.

Perfluorooctylbromide nanoparticles for ultrasound imaging and drug delivery

Perfluorooctylbromide nanoparticles (PFOB NPs) are a type of multifunctional nanotechnology that has been studied for various medical applications. Commercial ultrasound contrast agents (UCAs) suffer from the following limitations: short half-lives in vivo, high background signal and restricted distribution in the vascular circulation due to their micrometer dimensions. PFOB NPs are new potential UCAs that persist for long periods in the circulatory system, possess a relatively stable echogenic response without increasing the background signal and exhibit lower acoustic attenuation than commercial UCAs. Furthermore, PFOB NPs may also serve as drug delivery vehicles in which drugs are dissolved in the outer lipid or polymer layer for subsequent delivery to target sites in site-targeted therapy. The use of PFOB NPs as carriers has the potential advantage of selectively delivering payloads to the target site while improving visualization of the site using ultrasound (US) imaging. Unfortunately, the application of PFOB NPs to the field of ultrasonography has been limited because of the low intensity of US reflection. Numerous researchers have realized the potential use of PFOB NPs as UCAs and thus have developed alternative approaches to apply PFOB NPs in ultrasonography. In this article, we review the latest approaches for using PFOB NPs to enhance US imaging in vivo. In addition, this article emphasizes the application of PFOB NPs as promising drug delivery carriers for cancer and atherosclerosis treatments, as PFOB NPs can transport different drug payloads for various applications with good efficacy. We also note the challenges and future study directions for the application of PFOB NPs as both a delivery system for therapeutic agents and a diagnostic agent for ultrasonography.

Evaluation of Intraplaque Neovascularization Using Superb Microvascular Imaging and Contrast-Enhanced Ultrasonography

BACKGROUND

Several studies have shown a linkage between intraplaque neovascularization (IPN) and plaque instability. Although contrast-enhanced ultrasonography (CEUS) may help visualize IPN in the carotid artery, its benefits are limited in Japan, where there is no health insurance coverage for contrast agents in medical imaging. Superb microvascular imaging (SMI), however, enables the depiction of low-velocity blood flow. The current study compares the diagnostic accuracy of SMI and CEUS in the evaluation of IPN.

METHODS

The SMI and CEUS video images were transferred to a workstation and then analyzed to determine whether intraplaque blood flow signals were detected with SMI and whether plaques were contrast-enhanced with carotid artery CEUS. The images generated were independently interpreted by 2 radiologic technologists and 1 neurologist.

RESULTS

Intraplaque enhancement was observed in 19 patients using CEUS while intraplaque blood flow signals were observed in 12 patients using SMI. A 100% specificity was recorded for SMI (all 12 patients with SMI-detected intraplaque blood flow showed contrast-enhanced plaques), while its sensitivity was 63% (8 of the 15 patients with no SMI-detected intraplaque blood flow showed contrast-enhanced plaques on CEUS).

CONCLUSIONS

The results of this study show that patients with SMI-detected blood flow will tend to have plaque enhancement using CEUS. This suggests that SMI, as a simpler, safer, and noninvasive technique, can facilitate the visualization of carotid artery IPN without the use of a contrast agent, as well as in the clinical evaluation of plaque instability.

Endogenous Interleukin-1β Is Implicated in Intraplaque Hemorrhage in Apolipoprotein E Gene Null Mice

BACKGROUND

Intraplaque hemorrhage (IPH) has been implicated in plaque instability and rupture in atherosclerotic lesions, although the mechanisms by which IPH progresses remain largely unknown. In this study, apolipoprotein E-deficient mice with carotid artery ligation and cuff placement around the artery were used, and pro-inflammatory cytokines that are implicated in IPH were analyzed.

METHODS AND RESULTS

The expression of interleukin-1β (IL-1β) increased significantly following cuff placement compared with mice with carotid artery ligation alone. IPH occurred in the cuff-placed carotid artery following treatment with the negative control (NC) small interfering RNA (siRNA). However, the occurrence was significantly reduced in the cuff-placed carotid artery following treatment with an IL-1β siRNA. Neovessel formation was significantly reduced in the carotid artery treated with the NC siRNA compared with that treated with IL-1β siRNA. IL-1β significantly inhibited the tube formation and wound healing capacities of vascular endothelial cells in vitro. Furthermore, immunostaining of matrix metalloproteinase-9 (MMP-9) significantly increased in the carotid artery treated with the NC siRNA compared with that treated with IL-1β siRNA.

CONCLUSIONS

These results suggest that endogenous IL-1β is implicated in the progression of IPH via the inhibition of physiological angiogenesis in the atherosclerotic plaque, leading to the formation of leaky neovessels. Furthermore, the stimulation of MMP-9 expression may also contribute to the formation of leaky neovessels.

Improved plaque neovascularization following 2-year atorvastatin therapy based on contrast-enhanced ultrasonography: A pilot study

The present study assessed changes in carotid plaque neovascularization following long-term atorvastatin therapy (20 mg/day) using contrast-enhanced ultrasonography (CEUS). In this prospective case series, seven males (mean age, 68±9 years) and three females (mean age, 67±10 years) with a total of 13 carotid plaques underwent standard ultrasonography and CEUS at baseline, as well as after 1 and 2 years of atorvastatin treatment. The same plaques were then examined using real-time CEUS. The results of the enhanced intensity of plaque neovascularization at baseline were compared with results obtained during follow-up to examine the effects of long-term atorvastatin therapy. Standard ultrasonography revealed that 7 of the 13 carotid plaques were uniformly echolucent, whereas 6 carotid plaques were predominantly echolucent. CEUS revealed an enhanced intensity of 10.5±2.1 decibels (dB) prior to treatment, which decreased significantly to 7.3±2.6 dB following 2 years atorvastatin therapy (P<0.001). The ratio of enhanced intensity in the carotid artery lumen to that in the plaque was 3.10±1.10 at baseline and this value significantly increased to 4.96±2.98 following treatment for 2 years (P<0.001). The current pilot study therefore indicates that two-year atorvastatin therapy (20 mg/day) may reduce plaque neovascularization in the Chinese population.

Noncanonical NF-κB signaling in microvessels of atherosclerotic lesions is associated with inflammation, atheromatous plaque morphology and myocardial infarction

BACKGROUND AND AIMS

Neovascularization is associated with atherosclerotic plaque instability and increased chance of myocardial infarction (MI). Patients with chronic inflammatory diseases (CID) have increased risk of atherosclerosis, and evidence demonstrates that NF-κB inducing kinase (NIK)-mediated noncanonical NF-κB signaling in endothelial cells (EC) is linked to inflammation and angiogenesis. Here, we hypothesized NIK may also be activated in EC of atherosclerotic lesion microvessels.

METHODS

Using cohorts of atherosclerotic lesions from coronary and carotid arteries, we quantified NIK expression in plaque microvessels and compared it to pathological markers, including inflammatory cell content, plaque characteristics and MI. Differences in gene transcripts were evaluated between stable and ruptured lesions.

RESULTS

NIK+EC were present in both coronary and carotid lesions. In CID patients, plaques with stenosis >40% had an increased number of NIK+EC and higher content of immune cells (p < .05) as compared to controls. Immune cells per NIK+EC were also greater in CID patients (p < .05), with pronounced differences as stenosis increased. In unstable lesions, NIK+EC were elevated as were EC expressing CXCL12 (p < .05). NIK+EC were increased in lesions with lipid content >40% (p < .05) and more abundant in coronary artery lesions implicated in MI (p < .05). These vessels also associated with atheromatous rather than fibrous plaque morphology (p < .05). Transcriptomic profiling demonstrated components of noncanonical NF-κB pathway were also upregulated in ruptured plaques (p < .05).

CONCLUSIONS

NIK+EC associate with chronic inflammation in advanced lesions and are linked to markers of local inflammation, lipid content, unstable plaque phenotype and development of MI. Therefore, targeting noncanonical NF-κB signaling may hold therapeutic potential for patients with atherosclerosis and cardiovascular disease.