Diagnostic imaging of aortic atherosclerosis and its complications

Thoracic aortic atherosclerosis has been shown to be an important cause of severe morbidity and mortality. At the present time, the case of performance, detailed information obtainable, and availability make TEE the procedure of choice for the imaging of thoracic aortic atherosclerosis; however, further technical advances in MR and CT, particularly in MR plaque characterization and the use of plaque specific contrast agents, may allow for a less invasive and more complete evaluation of thoracic aortic atherosclerosis in the near future. Gadolinium-enhanced 3DMRA is the procedure of choice for the noninvasive detection of plaque in the proximal aortic arch vessels. Furthermore, both CT and MRI are better suited to evaluate penetrating atherosclerotic ulcers and their complications such as intramural hematoma, pseudoaneurysm formation, and aortic rupture.     

主动脉弓粥样硬化-脑栓塞的重要潜在栓塞源

目的　探讨脑栓塞患者的主动脉弓粥样硬化 (AAA)严重程度、临床意义、栓塞的潜在性及其有关的危险因素 ,进一步了解AAA与颈动脉及心脏疾病的相关性。方法　对 49例脑栓塞患者进行了TCD ,经食道超声心动图 (TEE) ,颈动脉实时超声 ,CT及MRI等检查。AAA分为三级 :轻度、中度、重度或活动性动脉粥样硬化斑块。结果　 31例 (6 3 % )在主动脉弓发现有动脉粥样硬化性病变。其中 7例 (14 1% )呈轻度病理改变 ,9例 (18 4% )呈中度病理改变 ,15例 (30 6 % )呈重度病理改变 ,31例患者中 11例患者无明显的颈内动脉及心脏疾患 ,其主动脉斑块可能是其脑栓塞的主要原因 ;33例患者伴有颈内动脉粥样硬化 (ICAA)改变 ;9例患者伴有心脏疾病 ;高龄及ICAA组AAA发生率明显增高。结论　主动脉弓粥样硬化是脑栓塞的重要潜在性栓塞源     

Transesophageal echocardiography: Diagnostic and clinical applications in the evaluation of the stroke patient.

Objectives. Transesophageal echocardiography (TEE) is superior to transthoracic echocardiography (TTE) in diagnosing cardiac abnormalities that may result in cerebral embolism. The clinical importance of these abnormalities is unclear. Methods. We classified 96 consecutive stroke patients into high- or low-risk groups for cardioembolism based on historical criteria. The presence of left atrial thrombus, atrial smoke, patent foramen ovale, atrial septal aneurysm, and plaque in the ascending aorta was assessed with TEE. Stroke type and other possible stroke mechanisms were evaluated. Results. Left atrial thrombus occurred only in the high-risk group. Patent foramen ovale, atrial septal aneurysm, and most cases of left atrial smoke occurred in the presence of another embolic source or were associated with a stroke related to hypertensive small vessel disease. Protruding atherosclerotic plaque in the ascending aorta and aortic arch was the most significant cause of stroke diagnosed by TEE because it frequently occurred in those without other risk factors for stroke. TEE identified aortic plaque in one and left atrial smoke in two patients with lacunar infarction without risk factors for small vessel disease. Conclusions. TEE should be considered in both lacunar and nonlacunar stroke that occur in the absence of stroke risk factors, although optimal management of most TEE findings is yet to be determined.     

Aortic Arch Atherosclerosis——An Important Potential Source Of Cerebral Embolic Stroke

Background and purpose: Recent years with use of transesophageal echography renew awareness of aortic atherosclerosis. The purpose of this study was to determine the prevalence, clinical significance, and embolic potential of thoracic aortic plaque in patients with cerebral emblism; and further study the correlation aortic plaque with carotid or heart disease. Method: 49 consecutive patients with cerebral embolism was included in this sutdy. We uscd TEE to evaluated potential source of emboli in aortic arch and heart, and duplex in carotid artery. A atherosclerotic lesion of thoracic aorta was defined as normal(O); mild plaque (1); moderate plaque (2); protruding plaque or mobile plaque (3). Result: 31(63%) patients showed evidence of AAA; 7 (14.3%) patients had mild AAA, 9 (18.4%) patients had moderate AAA and 15 (32.7%) patients had severe AAA, In these 15 patients 11 patients neither severe ICAA or embolic heart disease, the AAA may be responsible to the cerebral embolism; 33 patients had internal carotid arterial atherosclerosis(ICAA), 9 patients had embolic heart disease; Age, ICAA had significant correlated with aortic plaque. Conclusion: Aortic atherosclerosis is common in cerebral embolism. Aortic plaque might be not only responsible for some unexplained embolic event, but also for some of the embolic stroke in the group of patient do have carotid artery or heart disease. Age might be important risk factor for the development of atherosclerotic lesion in the thoracic aorta.     

B-mode ultrasound and spiral CT for the assessment of carotid atherosclerosis

More studies on the natural history of carotid artery plaques are needed to predict more reliably which plaque types or features are the most dangerous (see Table 2). Studies on carotid and coronary endarterectomy specimens indicate a dynamic process of rupture, thrombus formation, healing, and remodeling of the plaque. A plaque from a symptomatic patient may not show any signs of plaque rupture if the plaque has healed or evolved since the debut of symptoms. Selection of high-risk symptomatic patients with carotid atherosclerosis for medical or surgical treatment requires reliable, noninvasive, and cost-effective imaging methods. B-mode ultrasonography can be used for detection of early (IMT) as well as late (plaque morphology) atherosclerotic disease. Plaque morphology evaluation on spiral CT imaging is only for research and not yet for clinical use. Asymptomatic patients with carotid atherosclerosis hardly benefit from surgical treatment, as the minimal decrease in ischemic stroke risk is almost equal to the risk of perioperative stroke or death. A high degree of carotid stenosis measured using conventional angiography is an accepted risk factor for stroke but does not identify all vulnerable plaques. Echolucency on ultrasound B-mode imaging can be included as an important parameter in this risk stratification, as it appears to predict rupture-prone, lipid-rich plaques in the mild to severely stenotic carotid artery of a symptomatic patient. The subjective evaluation of plaque morphology on B-mode ultrasound should be complemented or substituted with objective evaluation such as videodensitometric analysis. This method is commercially available and is a relatively cheap and investigator-independent solution, but more studies are required to determine the exact contribution of echolucency to stroke risk. Furthermore, the evaluation of plaque morphology using ultrasound B-mode is still subject to large variations and observer-dependence, limiting its clinical use. In contrast, carotid IMT measurements are reliable to monitor progression and regression of early carotid disease as well as the impact of interventions. This method, however, suffers when used in severely diseased vessels where the boundaries of the IMT complex are hard to distinguish in all segments of the artery. Spiral CT imaging is a preliminary test for plaque characterization, as it primarily identifies calcification but not the more relevant lipid component. Moreover, it is time and resource demanding and involves use of both contrast and radiation, increasing the risk of allergic events and cancer. Standardization and continuous quality control are important, as are consensus agreements on how to quantify lesions (especially IMT), calibrate and standardize B-mode images and outline the plaque, and analyze data. The development of imaging methods for atherosclerotic research is currently fast and promising. This progress is most necessary, considering the very high demands for surrogate endpoints and risk markers in clinical intervention studies. Whether ultrasonic plaque characterization can be implemented in broad general clinical practice, for example, in screening of individuals at high risk of developing atherosclerosis and ischemic events, has to be based upon data from large prospective studies with long-term follow-up. IMT is already used in population screening, as in the ARIC study [9,101].     

卒中相关的粥样硬化易损斑块的病理与分布特点研究进展

发生于颅内、外动脉包括主动脉弓等处的动脉粥样硬化易损斑块,是引起缺血性卒中的主要原因之一。与卒中相关的易损斑块在不同血管床的分布具有一定的规律和种族差异性。本综述将从尸检结果和影像学检查两方面,总结文献中发生于颅内、外动脉包括主动脉弓的易损斑块的病理学特征、分布规律和种族差异性,旨在为缺血性卒中的预防、诊断及治疗提供重要依据。     

Significance of aortic atheroma in elderly patients with ischemic stroke. A hospital-based study and literature review

OBJECTIVES: Cardioembolism accounts for 15-30% of ischemic strokes. Transesophageal echocardiography (TEE) is useful in detecting potential sources of cardiac embolism. Aortic atheromas have recently been recognized as important causes of stroke. The aim of this study was to evaluate TEE findings in elderly patients with ischemic stroke. A review of literature was done to highlight the significance of aortic atherosclerotic disease in patients with ischemic stroke. METHODS: One hundred consecutive patients with ischemic stroke aged > or =55 years underwent TEE for evaluation of cardiac sources of embolism. Patients with significant carotid artery stenosis (stenosis of >50% in common or internal carotid arteries) were excluded. RESULTS: The most noteworthy finding was the high prevalence of complex atheromatous plaques in the ascending aorta and/or aortic arch (25%). CONCLUSION: The present study demonstrates that TEE is helpful to detect cardiovascular sources of embolism in elderly patients with ischemic stroke. Aortic atheroma is present in 25% of elderly patients with ischemic stroke and without significant carotid artery stenosis. Aortic atherosclerosis may be an important cause of ischemic stroke in this population.     

主动脉粥样硬化斑块与缺血性卒中关系的研究进展

目前,弓上颅外动脉粥样硬化性斑块和心脏是被公认的脑栓塞的主要来源,但仍有资料显示近1/3的脑栓塞栓子来源不明,提示着可能存在其他潜在的栓塞来源。随着各种影像学手段的不断普及和发展,尤其是经食道超声的广泛应用,许多研究者发现主动脉弓粥样硬化斑块（aorticarch atheroma,AAA）与缺血性卒中关系密切。本文旨在结合文献从流行病学、危险因素、二者相关性及诊治方面对主动脉粥样硬化斑块及其与卒中之间的关系进行综述。     

Do stroke patients with normal carotid arteries require TEE for exclusion of relevant aortic plaques?

OBJECTIVES: This study investigated (a) the hypothesis that stroke patients with aortic atheroma would show comparable atherosclerotic changes in the carotid arteries, which are easily accessible for ultrasound evaluation and (b) the possibility of carotid duplex sonography as a replacement for transoesophageal echocardiography (TEE) for the exclusion or prediction of relevant aortic plaques. METHODS: In 301 consecutive patients (mean age 62 years) with acute cerebral ischaemia, two dimensional ultrasound measurements were taken of common carotid artery intima media thickness (IMT) and maximal plaque area (PA) and the local degree of internal carotid artery (ICA) stenosis were determined. Maximal aortic wall thickness (AWT) was assessed by TEE. RESULTS: An IMT < or =0.9 mm yielded a negative predictive value (NPV) of 95.8% for exclusion of aortic atheromas > or =4 mm and an NPV of 100% for the exclusion of aortic thrombi. However, positive predictive value of IMT >0.9 mm was low (29.6%), increasing only slightly in the presence of carotid plaques (33%). Incidence of aortic thrombi was significantly higher with > or =50% compared with <50% ICA stenosis (11.3% v 3.9%, respectively). IMT and PA correlated moderately with AWT (r = 0.47, r = 0.53, respectively; p<0.001). Systolic blood pressure, coronary heart disease and peripheral artery disease, increased IMT, and ICA stenosis > or =50% were independently related to AWT > or =4 mm. CONCLUSIONS: A high NPV of normal carotid ultrasound does not support routine TEE for the exclusion of complex aortic plaques as a high risk source of cerebral embolism. However, in patients with carotid atherosclerosis, particularly in those with ICA stenosis > or =50%, TEE should be performed to exclude an additional high risk source for stroke.     

Plaque morphology correlates with cerebrovascular symptoms in patients with complex aortic arch plaque

BACKGROUND: Studies of aortic arch plaques with transesophageal echocardiography have demonstrated that complex aortic arch plaques (CAPs) greater than or equal to 4 mm in thickness are associated with ischemic stroke. Recent studies have demonstrated that the morphological features of plaques may aid in the identification of aortic plaques that are more likely to be associated with embolic stroke. OBJECTIVE: To identify aortic plaques that are more likely to be associated with embolic stroke by means of their morphological features. METHODS: Transcutaneous B-mode ultrasonography was used to image aortic arch plaques in 500 consecutive patients. The criteria used to identify the morphological features of carotid artery plaques that are more likely to be associated with ischemic stroke (heterogeneous rather than homogeneous) were applied to aortic arch plaques. Statistical comparisons were made using the Fisher exact test. RESULTS: Ischemic symptoms (eg, stroke, transient ischemic attack, and amaurosis fugax) were present in 38% of 104 patients with CAP and in 34% of 391 patients without CAP. Nineteen (51%) of 37 patients with heterogeneous CAP were symptomatic. Twenty-one (31%) of 67 patients with homogeneous CAP were symptomatic (P = .04). CONCLUSION: Transcutaneous B-mode ultrasonography of the aortic arch can help to identify heterogeneous plaques that are more likely to be associated with ischemic stroke using morphological criteria derived from studies of carotid artery plaque.     

Natural history of aortic arch atherosclerotic plaque

To define the natural history of aortic arch plaque, we used B-mode ultrasonography to perform sequential study of the aortic arch. Eighty-nine patients were studied for up to 18 months. There was no change in 67% of total plaques; 77% of simple plaque (<4 mm) and 48% of complex plaque (> or =4 mm) did not progress. Atherosclerosis of the aortic arch can be sequentially studied with B-mode ultrasonography, and most of these lesions remain unchanged after up to 18 months of observation.     

缺血性卒中患者颈动脉粥样硬化斑块高分辨磁共振成像研究进展简

脑卒中是严重危害人类生命健康的主要疾病之一,而以动脉粥样硬化性病变为病理基础的缺血性卒中为其最常见的临床发病类型。因此,及时识别粥样硬化斑块易损性即显得愈发重要。颈动脉MRI作为一项无创性检查手段,对动脉粥样硬化斑块性质的检测具有独特优势,对显示斑块形态和成分具有较高的敏感性和特异性,可以对粥样硬化斑块破裂的潜在危险进行评价和分层,进而为临床制定有效治疗方案提供影像学诊断依据。     

Characteristics and Predictors of Aortic Plaques in Patients with Transient Ischemic Attacks and Strokes

OBJECTIVE: To identify the prevalence and characteristics of aortic atherosclerotic plaque disease and its association with cerebrovascular risk factors in patients with cerebral ischemic events. BACKGROUND: Aortic atheroma is associated with ischemic stroke. Its characteristics, including morphology and distribution among different stroke subtypes, are not well described. METHOD: From July 2000 to August 2001, all patients evaluated by transesophageal echocardiography (TEE) with diagnoses of transient ischemic attacks (TIAs) and strokes were prospectively studied. Demographics, including age, gender, ethnicity, cerebrovascular risk factors, and stroke subtypes, were collected. RESULTS: Thoracic aortic atheromas (TAAs) were present in 141 of 237 patients (59%) (mean age = 59 +/- 14, 119 [50%] male). Mild plaque (< 2 mm) was present in 13 of 237 (5%), moderate plaque (2-4 mm) in 49 (21%), severe plaque (> or = 4 mm) in 79 (33%), and complex plaque in 64 (27%). Patients' ages (odds ratio [OR] = 1.05, confidence interval [CI] 1.03-1.08, P < .001), coronary artery disease (OR = 2.2, CI 1.02-4.8, P < .042), and patent foramen ovale (PFO) (OR = 0.39, CI 0.22-0.70, P < .002) were associated with the severity and complexity of aortic plaque. In multivariate analysis, age (OR = 1.06, CI 1.03-1.08, P < .001) and the presence of PFO (OR = 0.35, CI 0.18-0.65, P < .001) continued to be significant to the severity and complexity of aortic atheroma. Gender, history of stroke, hypertension, diabetes mellitus, hyperlipidemia, and history of smoking were not associated with TAA. CONCLUSION: One third of TAA plaques are severe and complex in nature and more frequently present in the descending aorta and the arch of the aorta than in the ascending aorta. TEE should be considered for the early detection and treatment of TAA in patients without identified causes of stroke.     

Molecular imaging of matrix metalloproteinases in atherosclerotic plaques

Ischaemic stroke and myocardial infarction often result from the sudden rupture of an atherosclerotic plaque. The subsequent arterial thrombosis occluding the vessel lumen has been widely indicated as the crucial acute event causing peripheral tissue ischaemia. A complex cross-talk between systemic and intraplaque inflammatory mediators has been shown to regulate maturation, remodeling and final rupture of an atherosclerotic plaque. Matrix metalloproteinases (MMPs) are proteolytic enzymes (released by several cell subsets within atherosclerotic plaques), which favour atherogenesis and increase plaque vulnerability. Thus, the assessment of intraplaque levels and activity of MMP might be of pivotal relevance in the evaluation of the risk of rupture. New imaging approaches, focused on the visualisation of inflammation in the vessel wall and plaque, may emerge as tools for individualised risk assessment and prevention of events. In this review, we summarize experimental findings of the currently available invasive and noninvasive imaging techniques, used to detect the presence and activity of MMPs in atherosclerotic plaques.     

Aortic atherosclerosis and stroke.

Methods: Studies using transesophageal echocardiography (TEE) suggest aortic atherosclerosis may be a risk factor for stroke, particularly stroke of undetermined mechanism, but controls in prior studies were not balanced for vascular risk factors. We used TEE to evaluate aortic atherosclerosis in 60 patients with stroke compared with a high-risk control population of 46 subjects. We also examined the possible association of plasma viscosity and fibrinogen levels to aortic atherosclerosis. Results: The mean maximal plaque thickness (MMPT) was similar for the control (2.8 +/- 3.6 mm) and the stroke group (3.3 +/- 3.5 mm), but varied with stroke mechanism. The MMPT was similar in stroke of undetermined and atherosclerotic mechanism [3.5 +/- 4 mm (n = 25) and 4.2 +/- 4.3 mm (n = 16), respectively], significantly greater than in stroke of other mechanisms (1.7 +/- 1.2 mm, P < .05, n = 19). Patients with stroke of undetermined mechanism were four times more likely (95% confidence interval [CI] 1.2-12) to have plaques >/=5 mm compared with controls. Ulcerated plaque was associated with plaque thickness (P < .001) and plasma viscosity (P < .001). Conclusions: Aortic atherosclerosis is associated with stroke of undetermined cause suggesting atherosclerosis is a cause of stroke of undetermined etiology. Plaque ulceration was associated with the thickness of aortic plaque and plasma viscosity.     

Detection of aortic plaques by transesophageal echocardiography in patients with ischemic stroke

Twenty-eight consecutive patients, aged 34–78 years with non-cardiogenic ischemic stroke were evaluated by transesophageal echocardiography (TEE). All patients were in sinus rhythm. Six of 28 patients (21.4%) displayed protruding masses in the aortic lumen. Five of these masses were located in the ascending aorta and one in the thoracic aorta. Our study suggests that cerebral infarction may also be due to aortic atherosclerotic plaques. Although our findings do not necessarily provide a causative link between atherosclerotic lesions in the aortic lumen and cerebral infarction, they may be an alternative potential source of stroke. TEE is the method of choice in detecting such lesions at the present time.     

Influence of Age Ranges on Relationship of Complex Aortic Plaque With Cervicocephalic Atherosclerosis in Ischemic Stroke

Background: Complex aortic plaque is a potential cause of acute ischemic cerebrovascular disease, which needs timely identification. Also as a marker for systemic atherosclerosis, complex aortic plaque may be indicated by significant (≥50%) cervicocephalic atherosclerotic stenosis. We aimed at examining whether age ranges would influence their association to more accurately estimate the risk of having complex aortic plaque in acute ischemic cerebrovascular disease. Methods: Aortic arch and cervicocephalic arteries were simultaneously evaluated using computed tomography angiography. Middle-aged (45-64 years) and old-aged (65-85 years) acute ischemic cerebrovascular disease patients were divided into 2 groups according to whether there was an aortic arch plaque with thickness of greater than or equal to 4 mm or associated ulcerations or mural thrombus. Results: Old-aged patients (n = 107) had a higher prevalence of complex aortic plaque (67.3% versus 30.9%, P < .001) than those middle aged (n = 178). Among middle-aged patients, the presence of extracranial significant atherosclerotic stenosis (adjusted odd ratio = 2.89, 95% confidence interval: 1.42-5.86) rather than intracranial ones independently predicted complex aortic plaque. Regarding the extent of significant cervicocephalic atherosclerotic stenosis, the presence of multi-segment, bilateral, simultaneous extracranial and intracranial, and simultaneous anterior and posterior circulation ones were independent indicators for complex aortic plaque in the middle-aged subgroup (adjusted odd ratio = 2.42, 2.05, 2.26, 2.14, respectively). By contrast, no statistical correlation of complex aortic plaque and significant cervicocephalic atherosclerotic stenosis was found among old-aged patients. Conclusion: Considering the ranges of age was important to more precisely predict complex aortic plaque with significant cervicocephalic atherosclerotic stenosis in acute ischemic cerebrovascular disease.     

Cholesterol Crystal in Thrombus Removed by Mechanical Thrombectomy Should be a Strong Marker for Aortogenic Embolic Stroke

Aortogenic embolic stroke (AES) is an important stroke mechanism. However, as many stroke patients have aortic atheromatous lesions, it is unclear whether these lesions are the cause of these strokes. Cholesterol crystals are the solid, crystalline form of cholesterol that is found in atherosclerosis, but not in cardiac diseases such as atrial fibrillation, valvular diseases, and cardiomyopathy. Therefore, if a cholesterol crystal is found in a thrombus removed by mechanical thrombectomy (MT), this makes it possible to diagnose a patient as having an atheromatous lesion. Here, we report an AES case with a cholesterol crystal found in a thrombus removed by MT. A 67-year-old man was admitted due to consciousness disturbance, aphasia, and right hemiplegia. Diffusion-weighted imaging (DWI) showed a hyperintense area in the left frontal lobe, and magnetic resonance angiography demonstrated a branch occlusion of the left middle cerebral artery (MCA). MT was performed 1.5 h after stroke onset, with the thrombus removed and a left occluded MCA completely recanalized. Carotid duplex ultrasonography did not reveal any plaque in the carotid artery. Echocardiography did not show any abnormal function or findings, including thrombus. Transesophageal echocardiography showed a 4.9 mm atheromatous lesion at the aortic arch. Therefore, we suspected this patient as having an AES due to the embolic source of atheromatous lesion at the aortic arch. Pathological examination of the embolus revealed a cholesterol crystal cleft in the thrombus. Therefore, we diagnosed this patient as having AES caused by an atheromatous lesion at the aortic arch.     

血浆同型半胱氨酸与脑梗死TOAST亚型相关性研究

目的:探讨血浆同型半胱氨酸(Hcy)浓度与脑梗死TOAST亚型间的相关性。方法:362例脑梗死患者依据TOAST分型诊断标准确定亚型,酶法测定晨起空腹血浆Hcy浓度,秩和检验Hcy水平与TOAST亚型间相关性;彩色多普勒超声检查根据颈动脉内-中膜厚度、血管内膜形态、血流频谱将粥样硬化斑块分为易损和非易损斑块组,对比分析Hcy水平与斑块性质间关系。结果:①大动脉粥样硬化(LAA)型脑梗死患者血浆Hcy水平、高同型半胱氨酸血症(HHcy)发生率显著高于TOAST其他亚型;将心源性栓塞型、小动脉闭塞型、其他原因型、病因不明型4亚型合并为非LAA组后,LAA型Hcy水平和HHcy发生率仍然最高(P<0.05)。②Logistic回归分析显示HHcy是LAA型脑梗死的独立危险因素(OR=7.73,95% CI:2.99~20.01)。③LAA型脑梗死易损斑块组患者血浆Hcy浓度和HHcy发生率均显著高于非易损斑块组(P<0.05);多因素分析显示HHcy和糖尿病是易损斑块的独立危险因素。结论:血浆Hcy增高与TOAST分型中LAA亚型、颈动脉粥样硬化易损斑块密切相关,提示HHcy可能通过引发大动脉粥样硬化而导致脑梗死。     

颈动脉粥样硬化斑块无创性高分辨力磁共振成像研究进展

颈动脉粥样硬化性狭窄与脑卒中复发密切相关。目前颈动脉狭窄的治疗方法主要包括药物治疗和外科手术(颈动脉支架成形术和颈动脉内膜切除术)。脑卒中预防在于识别颈动脉狭窄危险因素,筛查脑卒中复发高危患者,从而使其从药物治疗或外科手术中获益,然而目前仅根据颈动脉狭窄程度制定治疗方案,缺乏个体化治疗。近年来,新型影像学技术如无创性高分辨力磁共振成像(HRMRI)等,可以检测出颈动脉易损斑块。与传统数字减影血管造影术测量的颈动脉狭窄程度相比,无创性HRMRI可以根据颈动脉斑块特征准确预测同侧脑卒中风险,从而指导个体化治疗。