Association between carotid atherosclerosis plaque with high signal intensity on T1-weighted imaging and subsequent ipsilateral ischemic events

High-resolution magnetic resonance vessel wall imaging in ischemic stroke and carotid artery atherosclerotic stenosis: A review

Ischemic stroke is a significant burden on human health worldwide. Carotid Atherosclerosis stenosis plays an important role in the comprehensive assessment and prevention of ischemic stroke patients. High-resolution vessel wall magnetic resonance imaging has emerged as a successful technique for assessing carotid atherosclerosis stenosis. This advanced imaging modality has shown promise in effectively displaying a wide range of characteristics associated with the condition, leading to a comprehensive evaluation. High-resolution vessel wall magnetic resonance imaging not only enables a comprehensive evaluation of the instability of carotid atherosclerosis stenosis plaques but also provides valuable information for understanding the pathogenesis and predicting the prognosis of ischemic stroke patients. The purpose of this article is to review the application of high-resolution magnetic resonance imaging in ischemic stroke and carotid atherosclerotic stenosis.

Association between Carotid Bifurcation Angle and Vulnerable Plaque Volume Using Black Blood Magnetic Resonance Imaging

The morphology of the internal carotid artery (ICA) bifurcation is increasingly being recognized as the cause of atherosclerosis and vulnerable plaque leading to cerebral infarction. In this study, we investigated the relationship between carotid bifurcation angle and carotid plaque volume evaluated using black blood magnetic resonance imaging (BB-MRI). Among the 90 patients who underwent revascularization for atherosclerotic symptomatic carotid stenosis between April 2016 and October 2022 using BB-MRI, carotid plaque was evaluated in 57 patients. Relative overall signal intensity (roSI) was defined as the signal intensity of the plaque on T1-weighted images relative to the signal intensity of the sternocleidomastoid muscle in the same slice as the common carotid bifurcation. Regions showing roSI ≥ 1.0 were defined as plaque, and the plaque volume and relative plaque volume were measured from roSI ≥1.0 to ≥2.0 in 0.1 increments. We calculated the angles between the common carotid artery (CCA) and the ICA and between the CCA and the external carotid artery (ECA) on magnetic resonance angiography. We classified two groups according to carotid bifurcation angles based on the ICA angle: Group A = <35° and Group B = ≥35°. Compared with Group A (n = 42), Group B (n = 15) showed a greater relative plaque volume between roSI ≥ 1.3 and roSI ≥ 1.5. A significant correlation was identified between relative plaque volume with roSI ≥ 1.4 and ICA angle (p = 0.049). Vulnerable plaque was significantly more frequent in the group with an ICA angle of ≥35. Moreover, the ICA angle was significantly greater in patients with a roSI of ≥1.4.

Sex Differences in Carotid Atherosclerosis: A Systematic Review and Meta-Analysis

BACKGROUND

Over the last decades, several individual studies on sex differences in carotid atherosclerosis have been performed covering a wide range of plaque characteristics and including different populations. This systematic review and meta-analysis aims to summarize previously reported results on sex differences in carotid atherosclerosis and present a roadmap explaining next steps needed for implementing this knowledge in clinical practice.

METHODS

We systematically searched PubMed, Embase, Web of Science, Cochrane Central, and Google Scholar for eligible studies including both male and female participants reporting prevalence of imaging characteristics of carotid atherosclerosis and meta-analyzed these studies. Studies had to report at least the following: (1) calcifications; (2) lipid-rich necrotic core; (3) intraplaque hemorrhage; (4) thin-or-ruptured fibrous cap; (5) plaque ulceration; (6) degree of stenosis; (7) plaque size; or (8) plaque inflammation. We prespecified which imaging modalities had to be used per plaque characteristic and excluded ultrasonography.

RESULTS

We included 42 articles in our meta-analyses (ranging from 2 through 23 articles per plaque characteristic). Men had more frequently a larger plaque compared to women and, moreover, had more often plaques with calcifications (odds ratio=1.57 [95% CI, 1.23-2.02]), lipid-rich necrotic core (odds ratio=1.87 [95% CI, 1.36-2.57]), and intraplaque hemorrhage (odds ratio=2.52 [95% CI, 1.74-3.66]), or an ulcerated plaque (1.81 [95% CI, 1.30-2.51]). Furthermore, we found more pronounced sex differences for lipid-rich necrotic core in symptomatic opposed to asymptomatic participants.

CONCLUSIONS

In this systematic review and meta-analysis, we demonstrate convincing evidence for sex differences in carotid atherosclerosis. All kinds of plaque features-plaque size, composition, and morphology-were more common or larger in men compared to women. Our results highlight that sex is an important variable to include in both study design and clinical-decision making. Further investigation of sex-specific stroke risks with regard to plaque composition is warranted.

Clinical features and long-term outcomes of symptomatic low-grade carotid stenosis

OBJECTIVE

In symptomatic low-grade stenosis, most of the reports did not clarify the long-term outcome. This study aims to clarify the clinical features and long-term outcomes of symptomatic low-grade stenosis cases.

MATERIALS AND METHODS

We included 123 symptomatic patients with low-grade (<50%) carotid stenosis. The relative plaque signal intensity (rSI) and expansive remodeling rate (ERR) were measured using carotid magnetic resonance imaging (MRI). Antiplatelet therapy and treatment for atherosclerosis risk factors were administered in all cases. Carotid endarterectomy (CEA) was performed when ischemic symptoms appeared, or the percent stenosis progressed despite medical treatment.

RESULTS

The mean percent stenosis, rSI, and ERR on admission were 22.3, 1.70, and 2.01, respectively. The mean volume of the hyperintense plaque on carotid MRI was 641.4± 540 mm3. Sixty percent of cases involved intraplaque hemorrhage and expansive remodeling. During a mean follow-up of 52 months, recurrence of ischemic events was confirmed in 45 cases (36.6%). Of the 67 cases performed follow-up MRI, 34 cases (50%) had an increased volume of T1-hyperintense plaque. CEA or carotid artery stenting was performed in 49 cases. During a mean follow-up of 57.8 months after CEA, two cases of death (fatal intracerebral hemorrhage and asphyxia) and one case of brain stem lacunar infarction were observed, but ipsilateral ischemic events were not.

CONCLUSION

Most of the symptomatic patients with low-grade stenosis had both intraplaque hemorrhage and expansive remodeling and presented a high risk of recurrence and stenosis progression. CEA may have preventive effects against ischemic events in low-grade stenosis.

Predictors of Progression in Intraplaque Hemorrhage Volume in Patients With Carotid Atherosclerosis: A Serial Magnetic Resonance Imaging Study

Background and Purpose

This study aimed to investigate the arterial disease risk factors for the progression of intraplaque hemorrhage (IPH) in patients with carotid atherosclerosis using serial high-resolution magnetic resonance (MR) imaging.

Methods

Consecutive symptomatic patients who had MRI evidence of intraplaque hemorrhage present in the ipsilateral carotid artery with respect to the side of the brain affected by stroke or TIA were recruited in the study. All the patients underwent follow-up MR imaging at least 6 months after baseline. The annual change in IPH and other carotid plaque morphology was calculated, and a tertile method was used to classify the plaques as progressed or not with respect to IPH volume using the software CASCADE. Logistic regression and receiver operating characteristic (ROC) curve were conducted to evaluate the risk factors for the progression of IPH.

Results

A total of thirty-four symptomatic patients (mean age: 67.1 years, standard deviation [SD]: 9.8 years, 27 men) were eligible for the final analysis, and contralateral plaques containing IPH were seen in 11 of these patients (making 45 plaques with IPH in total). During mean 16.6-month (SD: 11.0 months) follow-up, the overall annual change in IPH volume in 45 plaques with IPH was mean −10.9 mm3 (SD: 49.1 mm3). Carotid plaques were significantly more likely to be classified in progressed IPH group if the patient was taking antiplatelet agent at baseline (OR: 9.76; 95%CI: 1.05 to 90.56; p = 0.045), had a baseline history of current or past smoking (OR: 9.28; 95%CI: 1.26 to 68.31; p = 0.029), or had a larger baseline carotid plaque-containing vessel wall volume (OR: 1.36 per 10 mm3; 95%CI: 1.02 to 1.81; p = 0.032) after adjustments for confounding factors. ROC analysis indicated that the combination of these three risk factors in the final model produced good discriminatory value for the progressed IPH group (area under the curve: 0.887).

Conclusions

Taking an antiplatelet agent at baseline, a baseline history of current or past smoking and larger baseline carotid plaque-containing vessel wall volume were independently predictive of plaques being in the progressed IPH group. Our findings indicate that awareness and management of such risk factors may reduce the risk of intraplaque hemorrhage progression.

Gradual Expansion of a Stent to Prevent Periprocedural Complications after Carotid Artery Stenting for Vulnerable Severe Stenotic Lesions with Intraplaque Hemorrhages: A Retrospective Observational Study

Vulnerable lesions with intraplaque hemorrhages are associated with a high incidence of complications following carotid artery stenting (CAS). CAS for vulnerable lesions has not been established; therefore, we gradually expand stents in such patients. This study aimed to compare the incidences of complications between gradual-expansion CAS for vulnerable lesions and standard CAS for non-vulnerable lesions. For gradual-expansion CAS, we used 3.0 or 4.0 mm balloons for minimal luminal diameters (MLDs) <2.0 or ≥2.0 mm, respectively, for pre-stenting angioplasty (SA) and did not overinflate them. By contrast, for standard CAS, we used a 4.0 mm balloon and overinflated it to 4.23 mm. A closed-cell stent was deployed, and post-SA was not performed in both groups. We evaluated the MLD before and minimal stent diameter (MSD) immediately after CAS, as well as periprocedural complications of combined stroke, death, and myocardial infarction within 30 days after CAS. In the vulnerable and non-vulnerable groups, 30 and 38 patients were analyzed, the MLDs were 0.76 and 0.96 mm before CAS, the MSDs were 2.97 mm and 3.58 mm after CAS, and the numbers of complications were 0 and 1, respectively. Gradual-expansion CAS for vulnerable lesions was as safe as standard CAS for non-vulnerable lesions.

Blocked Filter of Anti-Embolic Device During Carotid Artery Stenting: A Rare Occurrence Posing Challenging Diagnostic Dilemma

The use of anti-embolic devices (AED’s) is a common practice in carotid artery stenting (CAS). It prevents the passage of blood clots and thrombi generated during the procedure from embolizing into the intracranial circulation. Disadvantages include the passage of small particles and complications related to advancement, deployment, and recovery of the filters. The filter of the AED can get clogged due to the high load of the emboli generated during CAS causing a slowing of the intracranial blood flow which normalizes once the filter is removed.

Here, we are presenting a case of the filter of AED getting blocked due to entrapped thrombi or blood clots and mimicking dissection and, sharing our experiences associated with the event.

Carotid plaque vulnerability on magnetic resonance imaging and risk of future ischemic events: a systematic review and meta-analysis

INTRODUCTION

Magnetic resonance imaging (MRI) can characterize carotid plaque features, including intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and thin/ruptured fibrous cap (TRFC), that have increased tendency to cause future cerebrovascular ischemic events. We performed a systematic review and meta-analysis of studies evaluating association of MRI-identified high-risk plaque features, including IPH, LRNC, and TRFC, with risks of subsequent ischemic events of stroke, transient ischemic attack (TIA), or amaurosis fugax (AF) over follow-up duration of ≥3 months.

EVIDENCE ACQUISITION

Multiple databases were searched for relevant publications between January 2000 and March 2020. Studies reporting outcomes of future ischemic events of stroke, TIA, or AF for individual MRI-identified high-risk carotid plaque features over follow-up duration of ≥3 months were included. Random effects meta-analysis was performed to estimate odds ratios (OR) and 95% confidence intervals (CI) comparing outcomes between MRI-positive and MRI-negative groups.

EVIDENCE SYNTHESIS

Fifteen studies including 2350 patients were included. The annual rate of future ischemic events was 11.9% for MRI-positive IPH, 5.4% for LRNC, and 5.7% for TRFC. IPH, LRNC, and TRFC were associated with increased risk of future ischemic events (OR 6.37; 95% CI, 3.96 to 10.24), (OR 4.34; 95% CI, 1.65 to 11.42), and (OR 10.60, 95% CI 3.56 to 31.58), respectively.

CONCLUSIONS

The current study findings strengthen the assertion that MRI-positive "high-risk" or "vulnerable" plaque features, including IPH, LRNC, and/or TRFC can predict risks of future ischemic events of stroke, TIA, or AF.

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.

Prediction of Stroke Risk by Detection of Hemorrhage in Carotid Plaques: Meta-Analysis of Individual Patient Data

OBJECTIVES

The goal of this study was to compare the risk of stroke between patients with carotid artery disease with and without the presence of intraplaque hemorrhage (IPH) on magnetic resonance imaging.

BACKGROUND

IPH in carotid stenosis increases the risk of cerebrovascular events. Uncertainty remains whether risk of stroke alone is increased and whether stroke is predicted independently of known risk factors.

METHODS

Data were pooled from 7 cohort studies including 560 patients with symptomatic carotid stenosis and 136 patients with asymptomatic carotid stenosis. Hazards of ipsilateral ischemic stroke (primary outcome) were compared between patients with and without IPH, adjusted for clinical risk factors.

RESULTS

IPH was present in 51.6% of patients with symptomatic carotid stenosis and 29.4% of patients with asymptomatic carotid stenosis. During 1,121 observed person-years, 66 ipsilateral strokes occurred. Presence of IPH at baseline increased the risk of ipsilateral stroke both in symptomatic (hazard ratio [HR]: 10.2; 95% confidence interval [CI]: 4.6 to 22.5) and asymptomatic (HR: 7.9; 95% CI: 1.3 to 47.6) patients. Among patients with symptomatic carotid stenosis, annualized event rates of ipsilateral stroke in those with IPH versus those without IPH were 9.0% versus 0.7% (<50% stenosis), 18.1% versus 2.1% (50% to 69% stenosis), and 29.3% versus 1.5% (70% to 99% stenosis). Annualized event rates among patients with asymptomatic carotid stenosis were 5.4% in those with IPH versus 0.8% in those without IPH. Multivariate analysis identified IPH (HR: 11.0; 95% CI: 4.8 to 25.1) and severe degree of stenosis (HR: 3.3; 95% CI: 1.4 to 7.8) as independent predictors of ipsilateral stroke.

CONCLUSIONS

IPH is common in patients with symptomatic and asymptomatic carotid stenosis and is a stronger predictor of stroke than any known clinical risk factors. Magnetic resonance imaging might help identify patients with carotid disease who would benefit from revascularization.

Molecular and Nonmolecular Magnetic Resonance Coronary and Carotid Imaging

Atherosclerosis is the leading cause of cardiovascular morbidity and mortality. Over the past 2 decades, increasing research attention is converging on the early detection and monitoring of atherosclerotic plaque. Among several invasive and noninvasive imaging modalities, magnetic resonance imaging (MRI) is emerging as a promising option. Advantages include its versatility, excellent soft tissue contrast for plaque characterization and lack of ionizing radiation. In this review, we will explore the recent advances in multicontrast and multiparametric imaging sequences that are bringing the aspiration of simultaneous arterial lumen, vessel wall, and plaque characterization closer to clinical feasibility. We also discuss the latest advances in molecular magnetic resonance and multimodal atherosclerosis imaging.

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.

Quantification of Carotid Intraplaque Hemorrhage: Comparison between Manual Segmentation and Semi-Automatic Segmentation on Magnetization-Prepared Rapid Acquisition with Gradient-Echo Sequences

Purpose: Carotid intraplaque hemorrhage (IPH) increases risk of territorial cerebral ischemic events, but different sequences or criteria have been used to diagnose or quantify carotid IPH. The purpose of this study was to compare manual segmentation and semi-automatic segmentation for quantification of carotid IPH on magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequences. Methods: Forty patients with 16–79% carotid stenosis and IPH on MPRAGE sequences were reviewed by two trained radiologists with more than five years of specialized experience in carotid plaque characterization with carotid plaque MRI. Initially, the radiologists manually viewed the IPH based on the MPRAGE sequence. IPH volume was then measured by three different semi-automatic methods, with high signal intensity 150%, 175%, and 200%, respectively, above that of adjacent muscle on the MPRAGE sequence. Agreement on measurements between manual segmentation and semi-automatic segmentation was assessed using the intraclass correlation coefficient (ICC). Results: There was near-perfect agreement between manual segmentation and the 150% and 175% criteria for semi-automatic segmentation in quantification of IPH volume. The ICC of each semi-automatic segmentation were as follows: 150% criteria: 0.861, 175% criteria: 0.809, 200% criteria: 0.491. The ICC value of manual vs. 150% criteria and manual vs. 175% criteria were significantly better than the manual vs. 200% criteria (p < 0.001). Conclusions: The ICC of 150% and 175% criteria for semi-automatic segmentation are more reliable for quantification of IPH volume. Semi-automatic classification tools may be beneficial in large-scale multicenter studies by reducing image analysis time and avoiding bias between human reviewers.

Correlation Between Cerebral Microbleeds and Vulnerable Plaque in Patients with Severe Carotid Artery Stenosis; Comparative Magnetic Resonance Imaging Study

GOAL

There are an increasing idea that the inflammation contributes to vascular diseases in various organs. The pathogenesis of both cerebral small vessel disease such as cerebral microbleeds and carotid plaque may be associated with chronic inflammation. This study was aimed to evaluate the correlation between microbleeds and carotid plaque characteristics.

MATERIALS AND METHODS

This study enrolled 85 patients who underwent surgical/endovascular treatments for carotid artery stenosis between January 2009 and July 2016. Their clinical data were precisely analyzed. T2*-weighted magnetic resonance (MR) imaging was performed to detect the cerebral microbleeds. The carotid plaque with high signal intensity on T1-weighted MR imaging was categorized into vulnerable plaque.

FINDINGS

The microbleeds was detected in 17 of 85 (20%). The prevalence of vulnerable carotid plaque and previous symptomatic lacunar infarction was significantly greater in the patients with microbleeds than in those without (P = .001 and P = .03, respectively). Multiple logistic regression analysis showed that the vulnerable plaque was significantly associated with the presence of microbleeds when adjusted for age, alcohol intake, antiplatelet drug use, the presence of previous symptomatic lacunar infarction, and coronary artery disease (P = .009, OR = 5.38, 95% CI = 1.51-21.0).

CONCLUSIONS

These findings suggest the correlation between microbleeds and vulnerable plaque in patients with severe (>70%) carotid artery stenosis. Systemic, chronic inflammation may play a key role in both small and large arteries' disease of the brain. The knowledge may be valuable to fully understand the entity of cerebrovascular diseases as one of systemic, chronic inflammation.

Asymptomatic moderate carotid artery stenosis with intraplaque hemorrhage: Progression of degree of stenosis and new ischemic stroke

Carotid intraplaque hemorrhage (IPH) plays a critical role in the progression of carotid atherosclerotic disease. IPH was associated with high intensity signal (HIS) in the plaque on Maximum intensity projection (MIP) images from routine three dimensional magnetic resonance imaging (3D-TOF MRA). The aim of this study was to evaluate the relationships among HIS, new ipsilateral ischemic stroke and a progression rate in carotid plaques with moderate stenosis. We included 45 carotid plaques with moderate stenosis (50%-69%) in 45 patients who could be followed more than 12 months. Carotid IPH was defined as the presence of HIS on 3DTOF MRA using the criteria previously we published. We analyzed the relation between the presence of HIS and new ischemic strokes and annual progression rate of carotid stenosis. HIS was present in 21 (47%) carotid arteries. Over a follow-up period of 24 ± 9 months, six ischemic strokes occurred in ipsilateral side. New ipsilateral ischemic stroke occurred more frequently in HIS positive group (P group: 6 of 21, 29%) than negative group (N group: 0 of 24, 0%) (p = 0.017). Annual progression rate of carotid stenosis is significantly higher in P group (+3.35%/year) than N group (-0.02%/year) (p = 0.0026). In multivariate regression analysis, HIS positive was an independent predictor for annual progression rate of carotid stenosis (p = 0.003). Evaluation of HIS in asymptomatic moderate carotid stenosis can potentially provide risk stratification of new ipsilateral ischemic strokes.

Shape and Location of Carotid Atherosclerotic Plaque and Intraplaque Hemorrhage: A High-resolution Magnetic Resonance Imaging Study

Aim: The present study aimed to investigate the association between shape and location of atherosclerotic plaques and intraplaque hemorrhage (IPH) in carotid arteries using magnetic resonance (MR) imaging.

Methods: Overall, 114 symptomatic patients (mean age: 64.9±10.9 years; 81 males) who underwent MR imaging and had advanced carotid plaques were included in analysis. IPH presence and carotid plaque shape and location (below and above bifurcation) were evaluated. The plaque shape was defined as follows: type-I: the arc-length of plaque is greater in the upstream; type-II: the arc-length of plaque in downstream and upstream is equal; and type-III: the arc-length of plaque is greater in downstream. The plaque shape and location were compared between plaques with and without IPH and their associations with IPH were determined.

Results: Of 181detectedplaques, 57 (31.5%) had IPH. Compared with plaques without IPH, those with IPH had higher incidence of the plaque shape of type-I (66.7% vs. 32.2%, P<0.001), lower incidence of plaque shape of type-III (24.6% vs. 50.0%, P=0.001), and were more likely located above carotid bifurcation (71.9% vs. 48.4%, P=0.003). The plaque shape of type-I (OR, 4.01; 95%CI, 1.36–11.83; P=0.012) and location above bifurcation (OR, 3.21; 95%CI, 1.07–9.61; P=0.037) of carotid plaques were significantly associated with IPH after adjusting for confounder factors.

Conclusions: Carotid plaque shape and location are significantly associated with the occurrence of IPH. Our findings could provide new insights for the pathogenesis of IPH and vulnerably plaques.

Risk prediction of cerebrovascular events with carotid plaque magneitc resonance analysis: A meta-analysis

BACKGROUND AND PURPOSE

It is not conclusive that magnetic resonance (MR)-based carotid atherosclerotic plaque assessment identifies high-risk features associated with cerebrovascular events. We aimed to systematically summarize the association of MR imaging (MRI)-determined intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and thinning/rupture of the fibrous cap (TRFC) with subsequent ischemic events.

MATERIALS AND METHODS

We performed a comprehensive literature search evaluating the association of MRI-based carotid plaque composition with ischemic outcomes. We included cohort studies examining IPH, LRNC, or TRFC with mean follow-up of≥6 months and an outcome measure of ipsilateral ischemic events. A meta-analysis was done according to the Cochrane guideline.

RESULTS

We identified 13 studies including 1.150 patients and 1.208 analyzed carotid arteries, with mean follow-up of 21.1 months. The hazard ratios (HR) for IPH, LRNC, and TRFC as predictors of subsequent ischemic events were 4.41 (95% CI: 2.87, 6.79), 3.00 (95% CI: 1.51, 5.95), and 5.94 (95% CI: 2.66, 13.28), respectively. The predictive value of carotid plaque MRI for ischemic events was acceptable, with sensitivity of 0.80 (95% CI: 0.66, 0.90) and specificity of 0.63 (95% CI: 0.57, 0.68). However, it was limited to confirm or exclude future ischemic events in clinical context, with positive likelihood ratio (LR) of 2.2 (95% CI: 1.9, 2.5) and negative LR of 0.31 (95% CI: 0.18, 0.55). No statistically significant heterogeneity or publication bias was observed.

CONCLUSION

The presence of IPH, LRNC, and TRFC determined by MRI is associated with increased risk of future ischemic events, but its predictive value is moderate and should not be used for confirmation or exclusion of future ischemic events in clinical context.

Plaque Characteristics of Patients with Symptomatic Mild Carotid Artery Stenosis

BACKGROUND

Carotid revascularization may be considered for severe stenosis, but its use for symptomatic mild stenosis (<50%) with vulnerable plaque or ulcer remains uncertain. The characteristics of patients with symptomatic mild stenosis who underwent revascularization are reviewed.

METHODS

The subjects of this study were 18 patients with symptomatic mild stenosis (<50%) on angiography from among 175 patients who underwent revascularization in our department. The plaques were evaluated by black-blood magnetic resonance imaging (BB-MRI) and ultrasonography (US) and classified into 2 types: type 1 (n = 15), a lesion with an ulcer or mobile plaque or thrombosis on angiography or US; and type 2 (n = 3), a lesion without any of the above. Fourteen patients underwent carotid endarterectomy (CEA), and 4 patients underwent carotid artery stenting.

RESULTS

The stenosis on angiography was 27.2% ± 10.7 (5%-41%), and the area carotid artery stenosis rate on US was 69.8 ± 14.5% (44.5%-97%). The stenosis rate of these 2 methods was not at all correlated. In type 1 plaque that underwent CEA, 10 of 11 patients had vulnerable plaque by histopathology, and 1 patient had thrombus on the plaque by operative findings. In type 2 plaque that underwent CEA, all patients had vulnerable plaque by histopathology. During the follow-up period, none of the patients had restenosis or stroke.

CONCLUSIONS

The findings of US and BB-MRI in patients with symptomatic mild stenosis (<50%) on angiography are important for determining treatment. If BB-MRI or US shows the findings of vulnerable plaque in mild stenosis, surgical treatment may be considered for these patients.

CT Attenuation Analysis of Carotid Intraplaque Hemorrhage

BACKGROUND AND PURPOSE

Intraplaque hemorrhage is considered a leading parameter of carotid plaque vulnerability. Our purpose was to assess the CT characteristics of intraplaque hemorrhage with histopathologic correlation to identify features that allow for confirming or ruling out the intraplaque hemorrhage.

MATERIALS AND METHODS

This retrospective study included 91 patients (67 men; median age, 65 ± 7 years; age range, 41-83 years) who underwent CT angiography and carotid endarterectomy from March 2010 to May 2013. Histopathologic analysis was performed for the tissue characterization and identification of intraplaque hemorrhage. Two observers assessed the plaque's attenuation values by using an ROI (≥ 1 and ≤2 mm²). Receiver operating characteristic curve, Mann-Whitney, and Wilcoxon analyses were performed.

RESULTS

A total of 169 slices were assessed (59 intraplaque hemorrhage, 63 lipid-rich necrotic core, and 47 fibrous); the average values of the intraplaque hemorrhage, lipid-rich necrotic core, and fibrous tissue were 17.475 Hounsfield units (HU) and 18.407 HU, 39.476 HU and 48.048 HU, and 91.66 HU and 93.128 HU, respectively, before and after the administration of contrast medium. The Mann-Whitney test showed a statistically significant difference of HU values both in basal and after the administration of contrast material phase. Receiver operating characteristic analysis showed a statistical association between intraplaque hemorrhage and low HU values, and a threshold of 25 HU demonstrated the presence of intraplaque hemorrhage with a sensitivity and specificity of 93.22% and 92.73%, respectively. The Wilcoxon test showed that the attenuation of the plaque before and after administration of contrast material is different (intraplaque hemorrhage, lipid-rich necrotic core, and fibrous tissue had P values of .006, .0001, and .018, respectively).

CONCLUSIONS

The results of this preliminary study suggest that CT can be used to identify the presence of intraplaque hemorrhage according to the attenuation. A threshold of 25 HU in the volume acquired after the administration of contrast medium is associated with an optimal sensitivity and specificity. Special care should be given to the correct identification of the ROI.

Magnetic Resonance Imaging Plaque Hemorrhage for Risk Stratification in Carotid Artery Disease With Moderate Risk Under Current Medical Therapy

BACKGROUND AND PURPOSE

Magnetic resonance imaging (MRI)-defined carotid plaque hemorrhage (MRIPH) can predict recurrent cerebrovascular ischemic events in severe symptomatic carotid stenosis. It is less clear whether MRIPH can improve risk stratification despite optimized medical secondary prevention in those with moderate risk.

METHODS

One-hundred fifty-one symptomatic patients with 30% to 99% carotid artery stenosis (median age: 77, 60.5% men) clinically deemed to not benefit from endarterectomy were prospectively recruited to undergo MRI and clinical follow-up (mean, 22 months). The clinical carotid artery risk score could be evaluated in 88 patients. MRIPH+ve was defined as plaque intensity >150% that of adjacent muscle. Survival analyses were performed with recurrent infarction (stroke or diffusion-positive cerebral ischemia) as the main end point.

RESULTS

Fifty-five participants showed MRIPH+ve; 47 had low, 36 intermediate, and 5 high carotid artery risk scores. Cox regression showed MRIPH as a strong predictor of future infarction (hazard ratio, 5.2; 95% confidence interval, 1.64-16.34; P=0.005, corrected for degree of stenosis), also in the subgroup with 50% to 69% stenosis (hazard ratio, 4.1; 95% confidence interval, 1-16.8; P=0.049). The absolute risk of future infarction was 31.7% at 3 years in MRIPH+ve versus 1.8% in patients without (P<0.002). MRIPH increased cumulative risk difference of future infarction by 47.1% at 3 years in those with intermediate carotid artery risk score (P=0.004).

CONCLUSIONS

The study confirms MRIPH to be a powerful risk marker in symptomatic carotid stenosis with added value over current risk scores. For patients undergoing current secondary prevention medication with clinically uncertain benefit from recanalization, that is, those with moderate degree stenosis and intermediate carotid artery risk scores, MRIPH offers additional risk stratification.

Carotid artery plaque assessment using quantitative expansive remodeling evaluation and MRI plaque signal intensity

OBJECT

Plaque characteristics and morphology are important indicators of plaque vulnerability. MRI-detected intraplaque hemorrhage has a great effect on plaque vulnerability. Expansive remodeling, which has been considered compensatory enlargement of the arterial wall in the progression of atherosclerosis, is one of the criteria of vulnerable plaque in the coronary circulation. The purpose of this study was risk stratification of carotid artery plaque through the evaluation of quantitative expansive remodeling and MRI plaque signal intensity.

METHODS

Both preoperative carotid artery T1-weighted axial and long-axis MR images of 70 patients who underwent carotid endarterectomy (CEA) or carotid artery stenting (CAS) were studied. The expansive remodeling ratio (ERR) was calculated from the ratio of the linear diameter of the artery at the thickest segment of the plaque to the diameter of the artery on the long-axis image. Relative plaque signal intensity (rSI) was also calculated from the axial image, and the patients were grouped as follows: Group A = rSI ≥ 1.40 and ERR ≥ 1.66; Group B = rSI< 1.40 and ERR ≥ 1.66; Group C = rSI ≥ 1.40 and ERR < 1.66; and Group D = rSI < 1.40 and ERR < 1.66. Ischemic events within 6 months were retrospectively evaluated in each group.

RESULTS

Of the 70 patients, 17 (74%) in Group A, 6 (43%) in Group B, 7 (44%) in Group C, and 6 (35%) in Group D had ischemic events. Ischemic events were significantly more common in Group A than in Group D (p = 0.01).

CONCLUSIONS

In the present series of patients with carotid artery stenosis scheduled for CEA or CAS, patients with plaque with a high degree of expansion of the vessel and T1 high signal intensity were at higher risk of ischemic events. The combined assessment of plaque characterization with MRI and morphological evaluation using ERR might be useful in risk stratification for carotid lesions, which should be validated by a prospective, randomized study of asymptomatic patients.

The association between expansive arterial remodeling detected by high-resolution MRI in carotid artery stenosis and clinical presentation

OBJECT

The purpose of the present study was to investigate the association between carotid artery (CA) expansive remodeling (ER) and symptoms of cerebral ischemia.

METHODS

One hundred twenty-two consecutive CAs scheduled for CA endarterectomy (CEA) or CA stent placement (CAS) were retrospectively studied. After excluding 22 CAs (2 were contraindicated for MRI, 8 had near-occlusion, 6 had poor image quality, and 6 had restenosis after CEA or CAS), there were 100 CAs (100 patients) included in the final analysis. The study included 50 symptomatic patients (mean age 73.6 ± 8.9 years, 6 women, mean stenosis 68.5% ± 21.3%) and 50 asymptomatic patients (mean age 72.0 ± 5.9 years, 5 women, mean stenosis 79.4% ± 8.85%). Expansive remodeling was defined as enlargement of the internal carotid artery (ICA) with outward plaque growth. The ER ratio was calculated by dividing the maximum distance between the lumen and the outer borders of the plaque perpendicular to the axis of the ICA by the maximal luminal diameter of the distal ICA at a region unaffected by atherosclerosis using long-axis, high-resolution MRI.

RESULTS

The ER ratio of the atherosclerotic CA was significantly greater than that of normal physiological expansion (carotid bulb; p < 0.01). The ER ratio of symptomatic CA stenosis (median 1.94, interquartile range [IQR] 1.58–2.23) was significantly greater than that of asymptomatic CA stenosis (median 1.52, IQR 1.34–1.81; p = 0.0001). When the cutoff value of the ER ratio was set to 1.88, the sensitivity and specificity to detect symptoms were 0.6 and 0.78, respectively. The ER ratio of symptomatic patients was consistently high regardless of the degree of stenosis.

CONCLUSIONS

There was a significant correlation between ER ratio and ischemic symptoms. The ER ratio might be a potential indicator of vulnerable plaque, which requires further validation by prospective observational study of asymptomatic patients.

Catheter-based intramural delivery of red blood cells in an animal model of atherosclerosis

This report demonstrates intramural red blood cell (RBC) delivery in an atherosclerotic rabbit aorta model and validates the ability of fluoroscopy and computed tomography to verify RBC deposition. A microinfusion catheter with a 35-gauge needle delivered RBCs mixed with iodinated contrast agent to the aorta wall. Six rabbits were sacrificed after injection to confirm RBC delivery. Iron deposition was examined in four additional rabbits 3-7 weeks after injection. Imaging demonstrated 86% sensitivity and 100% specificity for the detection of RBC deposition (n = 25 injection attempts). Iron deposits were found in all intraplaque injection sites 3-7 weeks after injection.

Detection of Symptomatic Carotid Plaque Using Source Data from MR and CT Angiography: A Correlative Study

BACKGROUND

Carotid plaque MRI has been a useful method to characterize vulnerable atherosclerotic plaque elements. Recent investigations have suggested that source images from CT angiography (CTA) and MR angiography (MRA) can identify the simple high-risk features of symptom-producing carotid artery plaque. We studied the correlation and relative diagnostic accuracies of CTA and MRA source images in detecting symptomatic carotid artery plaque.

METHODS

Subjects were eligible if they had carotid stenosis between 50 and 99% and had MRA and CTA exams performed within 10 days of one another. We measured the soft (non-calcified) plaque and hard (calcified) plaque thickness on CTA axial source images and intraplaque high-intensity signal (IHIS) on 3D-time-of-flight MRA source images in subjects. We assessed whether a correlation existed between increasing CTA soft plaque thicknesses and the presence of MRA IHIS using the Student's t-test. We calculated the differences in sensitivity and specificity measures of CTA and MRA source-imaging data with the occurrence of recent ipsilateral stroke or transient ischemic attack (TIA) as the reference standard. We also performed logistic regression analyses to evaluate the predictive strength of plaque showing both IHIS and increased CTA soft plaque thickness in predicting symptomatic disease status.

RESULTS

Of 1994 screened patients, 48 arteries met the final inclusion criteria with MRA and CTA performed within 10 days of one another. The mean and median time between CTA and MRA exams were 2.0 days and 1 day, respectively. A total of 34 of 48 stenotic vessels (70.8%) were responsible for giving rise to ipsilateral stroke or TIA. CTA mean soft plaque thickness was significantly greater (4.47 vs. 2.30 mm, p < 0.0001) in patients with MRA-defined IHIS, while CTA hard plaque thickness was significantly greater (2.09 vs. 1.16 mm, p = 0.0134) in patients without MRA evidence of IHIS. CTA soft plaque thickness measurements were more sensitive than MRA IHIS (91.2 vs. 67.6%, p = 0.011) in detecting symptomatic plaque, while differences in specificity were not significantly different (p = 0.1573). In the subset of patients with both IHIS on MRA and plaque thickness >2.4 mm on CTA, the odds ratio of detecting symptomatic plaque, corrected for stenosis severity, was 45.3 (p < 0.0005).

CONCLUSIONS

Unprocessed source images from CTA and MRA, which are routinely evaluated for clinical studies demonstrate the highly correlated presence of IHIS and increasing soft plaque thickness. In particular, plaque that shows high-risk features on both MRA and CTA are very strongly associated with symptom-producing carotid plaque. With further validation, such techniques are promising practical methods of extracting risk information from routine neck angiographic imaging.

Pathophysiology of Acute Cerebrovascular Syndrome in Patients With Carotid Artery Stenosis

BACKGROUND:

The mechanisms underlying acute cerebrovascular syndrome in patients with carotid artery stenosis remain unclear.

OBJECTIVE:

To assess the relationships among infarct localization, hemodynamics, and plaque components.

METHODS:

This prospective study included 38 patients with acute cerebrovascular syndrome resulting from ipsilateral carotid artery stenosis. Cerebral infarct localization was categorized into 3 patterns (cortical, border zone, and mixed pattern). Carotid plaque components were evaluated with T1-weighted magnetic resonance imaging and time-of-flight imaging. Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were also quantified.

RESULTS:

Infarcts were identified in 38 patients with the use of diffusion-weighted magnetic resonance imaging. On the basis of the assessment of hemodynamics, the cortical pattern was seen in 18 of 21 patients with type 1 ischemia (normal CBF, normal CVR), whereas the mixed pattern was seen in 2 patients with type 2 ischemia (normal CBF, impaired CVR) and 12 of 15 patients with type 3 ischemia (impaired CBF, impaired CVR). The plaque components were categorized into fibrous (4 patients), lipid-rich (14 patients), and intraplaque hemorrhage (IPH; 20 patients). Of the patients with fibrous plaque, 2 had border-zone and 2 had mixed-pattern infarcts. Of the patients with lipid-rich plaque, 7 had cortical and 6 had mixed-pattern infarcts. Of patients with intraplaque hemorrhage, 11 had cortical and 9 had mixed-pattern infarcts.

CONCLUSION:

Cortical infarction occurs as a result of vulnerable plaque. Reduced cerebral perfusion induces border-zone infarction. Both factors are implicated in mixed-pattern infarction. Developments in noninvasive diagnostic modalities allow us to explore the mechanisms behind acute cerebrovascular syndrome in carotid artery stenosis and to determine the ideal therapies.

Correlating hemodynamic magnetic resonance imaging with high-field intracranial vessel wall imaging in stroke

Vessel wall magnetic resonance imaging at ultra-high field (7 Tesla) can be used to visualize vascular lesions noninvasively and holds potential for improving stroke-risk assessment in patients with ischemic cerebrovascular disease. We present the first multi-modal comparison of such high-field vessel wall imaging with more conventional (i) 3 Tesla hemodynamic magnetic resonance imaging and (ii) digital subtraction angiography in a 69-year-old male with a left temporal ischemic infarct.

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

Stroke remains the most prevalent disabling illness today, with internal carotid artery luminal stenosis due to atheroma formation responsible for the majority of ischemic cerebrovascular events. Severity of luminal stenosis continues to dictate both patient risk stratification and the likelihood of surgical intervention. But there is growing evidence to suggest that plaque morphology may help improve pre-existing risk stratification criteria. Plaque components such a fibrous tissue, lipid rich necrotic core and calcium have been well investigated but plaque hemorrhage (PH) has been somewhat overlooked. In this review we discuss the pathogenesis of PH, its role in dictating plaque vulnerability, PH imaging techniques, marterial properties of atherosclerotic tissues, in particular, those obtained based on in vivo measurements and effect of PH in modulating local biomechanics.

Coronary and carotid atherosclerosis: how useful is the imaging?

The recent advancement of imaging modalities has made possible visualization of atherosclerosis disease in all phases of its development. Markers of subclinical atherosclerosis or even the most advanced plaque features are acquired by invasive (IVUS, OCT) and non-invasive imaging modalities (US, MRI, CTA). Determining plaques prone to rupture (vulnerable plaques) might help to identify patients at risk for myocardial infarction or stroke. The most accepted features of plaque vulnerability include: thin cap fibroatheroma, large lipid core, intimal spotty calcification, positive remodeling and intraplaque neovascularizations. Today, research is focusing on finding imaging techniques that are less invasive, less radiation and can detect most of the vulnerable plaque features. While, carotid atherosclerosis can be visualized using noninvasive imaging, such as US, MRI and CT, imaging plaque feature in coronary arteries needs invasive imaging modalities. However, atherosclerosis is a systemic disease with plaque development simultaneously in different arteries and data acquisition in carotid arteries can add useful information for prediction of coronary events.

Characterization of carotid artery plaque components on magnetic resonance imaging using signal intensity of the phantom as a reference

RATIONALE AND OBJECTIVES

To evaluate the properties of plaque by the use of magnetic resonance imaging (MRI), it is necessary to use a material with stable signal intensity (eg, muscle or submandibular gland) as a reference. However, there may be differences between individuals. Therefore, we used a small phantom set on the circumference of the neck as a reference. The signal intensity ratio (SIR) methods using the phantom as a reference were reviewed for discrimination of the properties of plaque in the carotid artery.

MATERIALS AND METHODS

Three phantoms (phantom 1: water; phantom 2: 5 μmol gadopentetate dimeglumine; and phantom 3: 2.5 μmol gadopentetate dimeglumine) were set around the neck. SIR was calculated for each region of interest and compared according to pathological grade.

RESULTS

The method using a phantom as a reference reduced the standard deviations of tissue ratios to 0.16 from 0.27 in comparison with the method using muscle and showed a close correlation with pathological grade. In addition, the agreement rates with pathological grade and grades from each SIR using signal intensity of the phantom as a reference were higher than using signal intensity of the muscle as a reference to 0.86 from 0.63 for two-dimensional images and to 0.86 from 0.71 for three-dimensional images.

CONCLUSIONS

The method described here reduced error compared to the method using muscle as a reference, and the results were closely correlated with pathological grade.

Carotid Plaque MRI and Stroke Risk

Background and Purpose—

MRI characterization of carotid plaque has been studied recently as a potential tool to predict stroke caused by carotid atherosclerosis. We performed a systematic review and meta-analysis to summarize the association of MRI-determined intraplaque hemorrhage, lipid-rich necrotic core, and thinning/rupture of the fibrous cap with subsequent ischemic events.

Methods—

We performed a comprehensive literature search evaluating the association of carotid plaque composition on MRI with ischemic outcomes. We included cohort studies examining intraplaque hemorrhage, lipid-rich necrotic core, or thinning/rupture of the fibrous cap with mean follow-up of ≥1 month and an outcome measure of ipsilateral stroke or transient ischemic attack. A meta-analysis using a random-effects model with assessment of study heterogeneity and publication bias was performed.

Results—

Of the 3436 articles screened, 9 studies with a total of 779 subjects met eligibility for systematic review. The hazard ratios for intraplaque hemorrhage, lipid-rich necrotic core, and thinning/rupture of the fibrous cap as predictors of subsequent stroke/transient ischemic attack were 4.59 (95% confidence interval, 2.91–7.24), 3.00 (95% confidence interval, 1.51–5.95), and 5.93 (95% confidence interval, 2.65–13.20), respectively. No statistically significant heterogeneity or publication bias was present in the 3 main meta-analyses performed.

Conclusions—

The presence of intraplaque hemorrhage, lipid-rich necrotic core, and thinning/rupture of the fibrous cap on MRI of carotid plaque is associated with increased risk of future stroke or transient ischemic attack in patients with carotid atherosclerotic disease. Dedicated MRI of plaque composition offers stroke risk information beyond measurement of luminal stenosis in carotid atherosclerotic disease.

Endoglin (CD105) is a more appropriate marker than CD31 for detecting microvessels in carotid artery plaques

Background:

Microvascular proliferation is a major risk factor for plaque vulnerability in patients with carotid stenosis. There are several vascular endothelial markers such as CD31 and CD105, but it is unclear which marker is most sensitive for microvessels. This study sought to examine the correlations between CD31 and CD105 expression in microvessels on carotid plaques and clinical manifestations.

Methods:

We studied 13 lesions in 12 patients. The patients underwent carotid endarterectomy and samples were stained for CD31 and CD105. The numbers of microvessels positive for these markers within a field of view were counted.

Results:

The average numbers of microvessels were 5.8 ± 5.4 for CD31 and 9.2 ± 9.3 for CD105 (P = 0.04). More microvessels were positive for CD105 than there were for CD31 in patients with diabetes mellitus (P = 0.04).

Conclusion:

In patients with carotid artery stenosis, CD105 is more appropriate than CD31 for detecting microvessels in carotid plaques. In patients with diabetes mellitus, CD105 is significantly more highly expressed in microvessels than CD31.

Intraplaque high-intensity signal on 3D time-of-flight MR angiography is strongly associated with symptomatic carotid artery stenosis

BACKGROUND AND PURPOSE

Intraplaque hemorrhage in carotid artery atherosclerotic plaque has been shown to be a marker of risk, associated with prior and future ischemic events, and has been associated with regions of intraplaque high-intensity signal on 3D-TOF MRA. We assessed the association of intraplaque high-intensity signal determined on 3D-TOF MRA with the incidence of prior ipsilateral stroke or TIA.

MATERIALS AND METHODS

We assessed intraplaque hemorrhage by evaluating for intraplaque high-intensity signal adapting a recently validated technique on 3D-TOF source images in participants with high-grade (≥ 70%) extracranial carotid stenosis. Logistic regression analyses were used to assess the strength of association between the presence of intraplaque high-intensity signal on routine MRA sequences and prior stroke or TIA.

RESULTS

Intraplaque high-intensity signal was present in 22 (41.5%) of 53 carotid arteries studied in 51 patients. Ipsilateral ischemic events occurred in 15 (68.1%) of 22 in the intraplaque high-intensity signal-positive group (10 strokes, 5 TIAs) and in 4 (12.9%) of 31 in the intraplaque high-intensity signal-negative group (3 strokes, 1 TIA). Ischemic events occurred within the 6-month period preceding imaging in 18 (94.7%) of 19 cases. The univariate odds ratio of the association of intraplaque high-intensity signal with any prior ischemic event was 14.5 (95% CI, 3.6-57.6), and the multivariate age- and sex-adjusted odds ratio was 14.2 (95% CI, 3.3-60.5). The association remained present across 1.5 T and 3T magnet field strengths.

CONCLUSIONS

Intraplaque high-intensity signal determined from MRA sequences already in place to measure luminal stenosis is strongly associated with prior ipsilateral ischemic events. Prospective validation of these findings to predict outcome in carotid artery stenosis could provide a valuable and widely accessible stroke risk stratification tool.

MRI plaque imaging detects carotid plaques with a high risk for future cerebrovascular events in asymptomatic patients

PURPOSE

The aim of this study was to investigate prospectively whether MRI plaque imaging can identify patients with asymptomatic carotid artery stenosis who have an increased risk for future cerebral events. MRI plaque imaging allows categorization of carotid stenosis into different lesion types (I-VIII). Within these lesion types, lesion types IV-V and VI are regarded as rupture-prone plaques, whereas the other lesion types represent stable ones.

METHODS

Eighty-three consecutive patients (45 male (54.2%); age 54-88 years (mean 73.2 years)) presenting with an asymptomatic carotid stenosis of 50-99% according to ECST-criteria were recruited. Patients were imaged with a 1.5-T scanner. T1-, T2-, time-of-flight-, and proton-density weighted studies were performed. The carotid plaques were classified as lesion type I-VIII. Clinical endpoints were ischemic stroke, TIA or amaurosis fugax. Survival analysis and log rank test were used to ascertain statistical significance.

RESULTS

Six out of 83 patients (7.2%) were excluded: 4 patients had insufficient MR image quality; 1 patient was lost-to-follow-up; 1 patient died shortly after the baseline MRI plaque imaging. The following results were obtained by analyzing the remaining 77 patients. The mean time of follow-up was 41.1 months. During follow-up, n = 9 (11.7%) ipsilateral ischemic cerebrovascular events occurred. Only patients presenting with the high-risk lesion types IV-V and VI developed an ipsilateral cerebrovascular event versus none of the patients presenting with the stable lesion types III, VII, and VIII (n = 9 (11.7%) vs. n = 0 (0%) during follow-up). Event-free survival was higher among patients with the MRI-defined stable lesion types (III, VII, and VIII) than in patients with the high-risk lesion types (IV-V and VI) (log rank test P<0.0001).

CONCLUSIONS

MRI plaque imaging has the potential to identify patients with asymptomatic carotid stenosis who are particularly at risk of developing future cerebral ischemia. MRI could improve selection criteria for invasive therapy in the future.

Meta-analysis and systematic review of the predictive value of carotid plaque hemorrhage on cerebrovascular events by magnetic resonance imaging

OBJECTIVES

This study sought to conduct a systematic review and meta-analysis to determine precise estimates of the predictive value of carotid intraplaque hemorrhage (IPH) as determined by magnetic resonance imaging (MRI) for cerebrovascular events.

BACKGROUND

There is emerging evidence that MR-based carotid atherosclerotic plaque assessment identifies high-risk features associated with cerebrovascular events. However, available data are based on smaller samples with heterogeneous source populations despite a promising value for noninvasive risk stratification.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library through September 2012 for studies that followed >35 individuals after baseline MRI. Independent observers abstracted information on populations, MR techniques, outcomes, and study quality. Risk estimates of the presence of IPH for cerebrovascular events were derived in random effects regression analysis, and causes of heterogeneity were determined in meta-regression analysis.

RESULTS

We identified 8 eligible studies including 689 participants who underwent carotid MRI. The prevalence of IPH at baseline was high (49.0%). Over a median follow-up of 19.6 months, a total of 108 cerebrovascular events occurred (15.7% event rate). The presence of IPH was associated with an ∼6-fold higher risk for events (hazard ratio [HR]: 5.69; 95% confidence interval [CI]: 2.98 to 10.87). The annualized event rate in subjects with detectable IPH was 17.71% compared with 2.43% in patients without IPH. Meta-regression analysis showed symptomatic subjects had higher risks as compared with asymptomatic subjects (HR: 11.71, 95% CI: 5.17 to 26.48 vs. HR: 3.50, 95% CI: 2.59 to 4.73, p = 0.0065), Also, differences were observed for sex and sample size (all p < 0.01), with moderate visual publication bias due to missing smaller sample-size studies (p = 0.18).

CONCLUSIONS

Presence of IPH on MRI strongly predicts cerebrovascular events. Homogenization of future studies is warranted to allow for sufficient assessment of level of evidence for intervention trials.

Carotid plaque hemorrhage on magnetic resonance imaging strongly predicts recurrent ischemia and stroke

Objective

There is a recognized need to improve selection of patients with carotid artery stenosis for carotid endarterectomy (CEA). We assessed the value of magnetic resonance imaging (MRI)-defined carotid plaque hemorrhage (MRIPH) to predict recurrent ipsilateral cerebral ischemic events, and stroke in symptomatic carotid stenosis.

Methods

One hundred seventy-nine symptomatic patients with ≥50% stenosis were prospectively recruited, underwent carotid MRI, and were clinically followed up until CEA, death, or ischemic event. MRIPH was diagnosed if the plaque signal intensity was >150% that of the adjacent muscle. Event-free survival analysis was done using Kaplan–Meier plots and Cox regression models controlling for known vascular risk factors. We also undertook a meta-analysis of reported data on MRIPH and recurrent events.

Results

One hundred fourteen patients (63.7%) showed MRIPH, suffering 92% (57 of 62) of all recurrent ipsilateral events and all but 1 (25 of 26) future strokes. Patients without MRIPH had an estimated annual absolute stroke risk of only 0.6%. Cox multivariate regression analysis proved MRIPH as a strong predictor of recurrent ischemic events (hazard ratio [HR] = 12.0, 95% confidence interval [CI] = 4.8–30.1, p < 0.001) and stroke alone (HR = 35.0, 95% CI = 4.7–261.6, p = 0.001). Meta-analysis of published data confirmed this association between MRIPH and recurrent cerebral ischemic events in symptomatic carotid artery stenosis (odds ratio = 12.2, 95% CI = 5.5–27.1, p < 0.00001).

Interpretation

MRIPH independently and strongly predicts recurrent ipsilateral ischemic events, and stroke alone, in symptomatic ≥50% carotid artery stenosis. The very low stroke risk in patients without MRIPH puts into question current risk–benefit assessment for CEA in this subgroup. ANN NEUROL 2013;73:774–784

Adventitial perfusion and intraplaque hemorrhage: a dynamic contrast-enhanced MRI study in the carotid artery

BACKGROUND AND PURPOSE

Autopsy studies have suggested a relationship between intraplaque hemorrhage (IPH) and vasa vasorum, which arise primarily from the adventitia. Adventitial vasa vasorum can be characterized in the carotid arteries by estimating perfusion parameters via dynamic contrast-enhanced MRI. The purpose of this investigation was to use dynamic contrast-enhanced MRI to test in vivo in a clinical population whether adventitial perfusion, indicative of vasa vasorum microstructure, is associated with IPH.

METHODS

Symptomatic patients with carotid plaque ipsilateral to the ischemic event underwent bilateral carotid artery MRI examination, which included multicontrast sequences for detecting IPH and a dynamic contrast-enhanced MRI sequence for characterizing adventitial perfusion. Kinetic modeling of the dynamic contrast-enhanced MRI time series was performed to estimate adventitial vp (fractional plasma volume, reflecting local blood supply) and K(trans) (transfer constant, reflecting vessel surface area, and permeability).

RESULTS

From the 27 patients (22 men; 69 ± 10 years of age) recruited, adventitial perfusion parameters were obtained in 50 arteries. The presence of IPH was associated with a significantly higher value in adventitial K(trans) (0.142 ± 0.042 vs 0.112 ± 0.029 min(-1); P<0.001) but not in vp (0.163 ± 0.064 vs 0.149 ± 0.062; P=0.338). This relationship remained after adjusting for symptomatic status, degree of stenosis, and other confounding factors.

CONCLUSIONS

This study demonstrated an independent pathophysiological link between the adventitia and IPH and related it to the microstructure of adventitial vasa vasorum. Adventitial perfusion imaging may be useful in studying plaque pathogenesis, but further examination through prospective studies is needed.

Virtual histology analysis of carotid atherosclerotic plaque: plaque composition at the minimum lumen site and of the entire carotid plaque

BACKGROUND

Virtual Histology intravascular ultrasound (VH IVUS) volumetric analysis (analysis of the entire plaque responsible for stenosis) has been used for carotid plaque diagnosis. Knowing the carotid plaque characteristics by analyzing the plaque composition only at the minimum lumen site will facilitate plaque diagnosis using VH IVUS.

PURPOSE

To detect the relationship between the VH IVUS volumetric analysis of the entire plaque responsible for carotid artery stenosis and the VH IVUS cross-section plaque analysis at the minimum lumen site.

METHODS

Forty-eight atherosclerotic cervical carotid stenoses in 45 consecutive patients were included in the study. VH IVUS was obtained during the carotid artery stenting procedure.

RESULTS

Simple regression analysis revealed that the volumetric proportion of each plaque type correlated significantly with the corresponding plaque-type area at the minimum lumen site. The adjusted coefficients of determination of the simple regression analyses were .782 (P < .001) for fibrous tissue, .741 (P < .001) for fibrofatty tissue, .864 (P < .001) for dense calcium, and .918 (P < .001) for necrotic core.

CONCLUSION

The plaque composition at the minimum lumen site represents the volumetric composition of the entire carotid plaque that causes atherosclerotic cervical carotid artery stenosis.

Carotid artery disease and stroke: assessing risk with vessel wall MRI

Although MRI is widely used to diagnose stenotic carotid arteries, it also detects characteristics of the atherosclerotic plaque itself, including its size, composition, and activity. These features are emerging as additional risk factors for stroke that can be feasibly acquired clinically. This paper summarizes the state of evidence for a clinical role for MRI of carotid atherosclerosis.

Lower prevalence of carotid plaque hemorrhage in women, and its mediator effect on sex differences in recurrent cerebrovascular events

Background and Purpose

Women are at lower risk of stroke, and appear to benefit less from carotid endarterectomy (CEA) than men. We hypothesised that this is due to more benign carotid disease in women mediating a lower risk of recurrent cerebrovascular events. To test this, we investigated sex differences in the prevalence of MRI detectable plaque hemorrhage (MRI PH) as an index of plaque instability, and secondly whether MRI PH mediates sex differences in the rate of cerebrovascular recurrence.

Methods

Prevalence of PH between sexes was analysed in a single centre pooled cohort of 176 patients with recently symptomatic, significant carotid stenosis (106 severe [≥70%], 70 moderate [50–69%]) who underwent prospective carotid MRI scanning for identification of MRI PH. Further, a meta-analysis of published evidence was undertaken. Recurrent events were noted during clinical follow up for survival analysis.

Results

Women with symptomatic carotid stenosis (50%≥) were less likely to have plaque hemorrhage (PH) than men (46% vs. 70%) with an adjusted OR of 0.23 [95% CI 0.10–0.50, P<0.0001] controlling for other known vascular risk factors. This negative association was only significant for the severe stenosis subgroup (adjusted OR 0.18, 95% CI 0.067–0.50) not the moderate degree stenosis. Female sex in this subgroup also predicted a longer time to recurrent cerebral ischemic events (HR 0.38 95% CI 0.15–0.98, P = 0.045). Further addition of MRI PH or smoking abolished the sex effects with only MRI PH exerting a direct effect.

Meta-analysis confirmed a protective effect of female sex on development of PH: unadjusted OR for presence of PH = 0.54 (95% CI 0.45–0.67, p<0.00001).

Conclusions

MRI PH is significantly less prevalent in women. Women with MRI PH and severe stenosis have a similar risk as men for recurrent cerebrovascular events. MRI PH thus allows overcoming the sex bias in selection for CEA.

Comparison of carotid atherosclerotic plaque characteristics by high-resolution black-blood MR imaging between patients with first-time and recurrent acute ischemic stroke

BACKGROUND AND PURPOSE

It has been shown that patients with a first ischemic stroke are at high risk of developing recurrent stroke due to carotid atherosclerotic plaque rupture. However, no one has defined the difference in plaques between initial and recurrent stroke. This study sought to investigate the characteristics of carotid plaque between patients with first-time and recurrent acute ischemic stroke by using MR imaging.

MATERIALS AND METHODS

Eighty-nine patients with recent acute ischemic stroke were recruited. All subjects underwent carotid high-resolution black-blood MR imaging. The index carotid arteries, defined as the arteries responsible for the ipsilateral stroke, were analyzed quantitatively and qualitatively. Carotid plaque burden and compositional features between patients with first-time and recurrent ischemic stroke were compared.

RESULTS

Of 89 recruited patients, 51 had first-time stroke and 38 had recurrent stroke. The mean WA, WT, and PWV were greater in patients with recurrent stroke than in patients with first-time stroke (all, P < .05). Compared with patients with first-time stroke, those with recurrent stroke showed significantly higher prevalence of calcification (44.7% versus 23.5%, P = .035) as well as a larger volume of LRNC (179.14 ± 254.81 mm(2) versus 71.65 ± 111.15 mm(2), P = .027). IPH or fibrous cap rupture or both were observed in 15.8% of patients with recurrent stroke and 3.9% of patients with first-time stroke.

CONCLUSIONS

Carotid plaques in patients with recurrent ischemic stroke are significantly aggravated compared with those in patients with first-time stroke, and monitoring carotid plaques in patients with initial stroke by MR imaging may be helpful for secondary stroke prevention.

Symptomatic and asymptomatic carotid artery plaque

Carotid atherosclerotic plaques represent both stable and unstable atheromatous lesions. Atherosclerotic plaques that are prone to rupture owing to their intrinsic composition such as a large lipid core, thin fibrous cap and intraplaque hemorrhage are associated with subsequent thromboembolic ischemic events. At least 15-20% of all ischemic strokes are attributable to carotid artery atherosclerosis. Characterization of plaques may enhance the understanding of natural history and ultimately the treatment of atherosclerotic disease. MRI of carotid plaque and embolic signals during transcranial Doppler have identified features beyond luminal stenosis that are predictive of future transient ischemic attacks and stroke. The value of specific therapies to prevent stroke in symptomatic and asymptomatic patients with severe carotid artery stenosis are the subject of current research and analysis of recently published clinical trials that are discussed in this article.

Safety of protected carotid artery stenting in patients with severe carotid artery stenosis and carotid intraplaque hemorrhage

BACKGROUND AND PURPOSE

Carotid IPH can be detected with MR imaging. The aim of this study was to determine the safety of CAS using an emboli protection device in patients with severe carotid artery stenosis and MR imaging-depicted carotid IPH.

MATERIALS AND METHODS

We retrospectively reviewed a prospective data base that included 91 consecutive patients with severe carotid stenosis and high-risk features who were treated with CAS by using an emboli protection device. Seventy-eight of the included patients underwent prestenting 3D TOF MRA. IPH was defined as the presence of high signal intensity within the carotid plaque, greater than 150% of the signal intensity of the adjacent neck muscle on TOF source images. The primary outcome measure was the combined incidence of stroke, MI, and death within 30 days of CAS. Associations between IPH and the primary outcome were investigated.

RESULTS

IPH was detected on TOF MRA in 30 patients. Symptomatic patients were more common in the IPH group than in the non-IPH group (66.7% vs 41.7%; P = .032). Overall, 30-day stroke, MI, or death rates were 6.6%. There was no significant difference in the primary outcome between the IPH and non-IPH groups (10% and 6.25%, respectively; hazard ratio for IPH, 1.151; 95% CI, 0.035 to 37.500; P = .937). A logistic regression showed there was no independent variable associated with the primary outcome.

CONCLUSIONS

The results of this study indicate that protected CAS seems to be safe in patients with severe carotid stenosis and IPH.