Imaging of vulnerable coronary artery plaques.

Advances in the identification of vulnerable plaque can be an important step in preventing myocardial infarction and sudden cardiac death. The recognition that non-flow-limiting plaques often produce cardiac events has led to the development of invasive and non-invasive methods to identify such plaques prospectively. This review will present the use of noninvasive imaging modalities for identifying vulnerable plaque such as computed tomography and magnetic resonance imaging. We will also review the different invasive modalities such as intravascular magnetic resonance imaging, intravascular ultrasound, coronary angioscopy, coronary thermography, optical coherence tomography, near-infrared spectroscopy, and palpography.     

Current status of vulnerable plaque detection

Critical coronary stenoses have been shown to contribute to only a minority of acute coronary syndromes (ACS) and sudden cardiac death. Autopsy studies have identified a subgroup of high‐risk patients with disrupted vulnerable plaque and modest stenosis. Consequently, a clinical need exists to develop methods to identify these plaques prospectively before disruption and clinical expression of disease. Recent advances in invasive and noninvasive imaging techniques have shown the potential to identify these high‐risk plaques. The anatomical characteristics of the vulnerable plaque such as thin cap fibroatheroma and lipid pool can be identified with angioscopy, high frequency intravascular ultrasound, intravascular MRI, and optical coherence tomography. Efforts have also been made to recognize active inflammation in high‐risk plaques using intravascular thermography. Plaque chemical composition by measuring electromagnetic radiation using spectroscopy is also an emerging technology to detect vulnerable plaques. Noninvasive imaging with MRI, CT, and PET also holds the potential to differentiate between low and high‐risk plaques. However, at present none of these imaging modalities are able to detect vulnerable plaque neither has been shown to definitively predict outcome. Nevertheless in contrast, there has been a parallel development in the physiological assessment of advanced atherosclerotic coronary artery disease. Thus recent trials using fractional flow reserve in patients with modest non flow‐limiting stenoses have shown that deferral of PCI with optimal medical therapy in these patients is superior to coronary intervention. Further trials are needed to provide more information regarding the natural history of high‐risk but non flow‐limiting plaque to establish patient‐specific targeted therapy and to refine plaque stabilizing strategies in the future. © 2009 Wiley‐Liss, Inc.     

Molecular imaging of plaques in coronary arteries with PET and SPECT

Coronary artery disease remains a major cause of mortality. Presence of atherosclerotic plaques in the coronary artery is responsible for lu-men stenosis which is often used as an indicator for determining the severity of coronary artery disease. However, the degree of coronary lumen stenosis is not often related to compromising myocardial blood flow, as most of the cardiac events that are caused by atherosclerotic plaques are the result of vulnerable plaques which are prone to rupture. Thus, identification of vulnerable plaques in coronary arteries has become increas-ingly important to assist identify patients with high cardiovascular risks. Molecular imaging with use of positron emission tomography （PET） and single photon emission computed tomography （SPECT） has fulfilled this goal by providing functional information about plaque activity which enables accurate assessment of plaque stability. This review article provides an overview of diagnostic applications of molecular imaging tech-niques in the detection of plaques in coronary arteries with PET and SPECT. New radiopharmaceuticals used in the molecular imaging of coro-nary plaques and diagnostic applications of integrated PET/CT and PET/MRI in coronary plaques are also discussed.     

Noninvasive diagnosis of vulnerable coronary plaque

Myocardial infarction and sudden cardiac death are frequently the first manifestation of coronary artery disease.For this reason,screening of asymptomatic coronary atherosclerosis has become an attractive field of research in cardiovascular medicine.Necropsy studies have described histopathological changes associated with the development of acute coronary events.In this regard,thin-cap fibroatheroma has been identified as the main vulnerable coronary plaque feature.Hence,many imaging techniques,such as coronary computed tomography,cardiac magnetic resonance or positron emission tomography,have tried to detect noninvasively these histomorphological characteristics with different approaches.In this article,we review the role of these diagnostic tools in the detection of vulnerable coronary plaque with particular interest in their advantages and limitations as well as the clinical implications of the derived findings.     

Technology Insight: optical coherence tomography--current status and future development

The understanding of concepts in coronary artery disease, such as the vulnerable or high-risk plaque, which accounts for many acute coronary events arising from non-flow-limiting coronary lesions, has advanced remarkably. Although coronary angiography is an established imaging technique for visualizing atherosclerotic disease, it is limited by its two-dimensional imaging aspect and a low sensitivity for identifying lesions in the presence of positive remodeling and diffuse disease. Moreover, coronary atherosclerotic plaques cannot be characterized. Although intravascular ultrasound is currently the most commonly employed adjunctive method to better define lesions, it is limited by low resolution. The development of new technologies for improved coronary plaque characterization has, thus, been desired. Optical coherence tomography is a developing technique that uses near-infrared light for the cross-sectional visualization of the vessel wall at the microscopic level. It enables excellent resolution of coronary architecture and precise characterization of plaque architecture. Quantification of macrophages within the plaque is also possible. These capabilities allow precise identification of the most common type of vulnerable plaque, the thin-cap fibroatheroma. Here, we discuss results from clinical studies which indicate that optical coherence tomography is a promising imaging technique for improved characterization of the coronary atherosclerotic plaque.     

Intracoronary Imaging in the Detection of Vulnerable Plaques

Coronary artery disease is the result of atherosclerotic changes to the coronary arterial wall, comprising endothelial dysfunction, vascular inflammation and deposition of lipid-rich macrophage foam cells. Certain high-risk atherosclerotic plaques are vulnerable to disruption, leading to rupture, thrombosis and the clinical sequelae of acute coronary syndrome. Though recognised as the gold standard for evaluating the presence, distribution and severity of atherosclerotic lesions, invasive coronary angiography is incapable of identifying non-stenotic, vulnerable plaques that are responsible for adverse cardiovascular events. The recognition of such limitations has impelled the development of intracoronary imaging technologies, including intravascular ultrasound, optical coherence tomography and near-infrared spectroscopy, which enable the detailed evaluation of the coronary wall and atherosclerotic plaques in clinical practice. This review discusses the present status of invasive imaging technologies; summarises up-to-date, evidence-based clinical guidelines; and addresses questions that remain unanswered with regard to the future of intracoronary plaque imaging.     

易损斑块的诊断进展

急性冠状动脉综合征患者具有较高的发病率,预后较差,而冠状动脉内易损斑块破裂伴随血栓形成是其主要原因.因此早期正确诊断易损斑块,对于急性冠脉综合征的防治具有重大意义.现就易损斑块的诊断进展作一综述.     

Italian Chapter of the International Society of Cardiovascular Ultrasound expert consensus document on coronary computed tomography angiography: overview and new insights

Coronary computed tomography angiography is a noninvasive heart imaging test currently undergoing rapid development and advancement. The high resolution of the three‐dimensional pictures of the moving heart and great vessels is performed during a coronary computed tomography to identify coronary artery disease and classify patient risk for atherosclerotic cardiovascular disease. The technique provides useful information about the coronary tree and atherosclerotic plaques beyond simple luminal narrowing and plaque type defined by calcium content. This application will improve image‐guided prevention, medical therapy, and coronary interventions. The ability to interpret coronary computed tomography images is of utmost importance as we develop personalized medical care to enable therapeutic interventions stratified on the bases of plaque characteristics. This overview provides available data and expert's recommendations in the utilization of coronary computed tomography findings. We focus on the use of coronary computed tomography to detect coronary artery disease and stratify patients at risk, illustrating the implications of this test on patient management. We describe its diagnostic power in identifying patients at higher risk to develop acute coronary syndrome and its prognostic significance. Finally, we highlight the features of the vulnerable plaques imaged by coronary computed tomography angiography.     

Regression of an atherosclerotic coronary artery plaque demonstrated by multislice spiral computed tomography in a patient with stable angina pectoris

Multislice spiral computed tomography (MSCT) permits direct visualization of not only coronary artery stenosis but also atherosclerotic plaques in patients with coronary artery disease. In this report, we describe a patient with stable angina in whom the regression of the plaque was documented by serial MSCT examinations. In the patient, a 46-year-old man with stable angina, MSCT revealed a stenotic lesion at the proximal portion of the left anterior descending artery. Axial, curved multiplanar reconstruction and cross-sectional images consistently depicted a protruding computed tomography low-signal mass suggesting an atherosclerotic plaque. Intracoronary ultrasound (ICUS) also documented an eccentric soft plaque with an echo-lucent mass suggesting a lipid core. Lipid-lowering therapy with pravastatin was started. Follow-up MSCT performed 7 months later documented an increase in the luminal area while the external vessel area remained unchanged. The regression of the plaque was also confirmed by a follow-up ICUS study. MSCT was thought to be feasible for serial evaluation of the plaque size and texture.     

Detection of plaque rupture using 64-slice multidetector row computed tomography

The present case report describes a 37-year-old man who presented to the emergency room with symptoms of a myocardial infarction but no high-grade stenosis on conventional catheter angiography. Consecutive multidetector row computed tomography of the coronary arteries showed an intimal flap along a fibrous plaque formation in the left anterior descending artery. This finding was found to represent a plaque rupture, and the lesion was treated with an 18 mm stent. Multidetector row computed tomography helped to correctly position the stent by identifying the exact location of the rupture along the long plaque formation.     

微钙化与易损斑块相关性的研究进展

不良心血管事件（ACE）的发生,大部分是在动脉管腔轻至中度狭窄的基础上,由易损斑块破裂或侵蚀以及血栓形成所致。现代医学对冠状动脉粥样化性疾病的研究,已从以往仅关注管腔狭窄的程度向关注斑块的易损性转变。因此,探索易损斑块破裂的机制,早期识别易损斑块,预防ACE的发生成为心血管疾病研究领域的热点之一。近年来,大量研究发现动脉粥样硬化（AS）斑块内微钙化（microcalcifications,μCalcs）的出现与斑块的易损性关系密切,由此推测μCalcs可能是引起斑块破裂的一个重要因素。本文对AS斑块内μCalcs与易损斑块的相关性作一综述。     

Clinical Utility of Intravascular Imaging: Past,Present, and Future

Although it is the tool used by most interventional cardiologists to assess the severity of coronary artery disease and guide treatment, coronary angiography has many limitations because it is a shadowgraph, depicting planar projections of the contrast-filled lumen that are often foreshortened rather than imaging the diseased vessel itself. Currently available intravascular imaging technologies include grayscale intravascular ultrasound (IVUS), optical coherence tomography (OCT) (the light analogue of IVUS), and near-infrared spectroscopy that detects lipid within the vessel wall and that has been combined with grayscale IVUS in a single catheter as the first combined imaging device. They provide tomographic or cross-sectional images of the coronary arteries that include the lumen, vessel wall, plaque burden, plaque composition and distribution, and even peri-vascular structures—information promised, but rarely provided angiographically. Extensive literature shows that these tools can be used to answer questions that occur during daily practice as well as improving patient outcomes. Is this stenosis significant? Where is the culprit lesion? What is the anatomy of an unusual or ambiguous angiographic lesion? What is the right stent size and length? What is the likelihood of distal embolization or periprocedural myocardial infarction during stent implantation? Has the intervention been optimized? Why did this stent thrombose or restenose? This review summarizes these uses of intravascular imaging as well as the outcomes data supporting their incorporation into routine clinical practice.     

心外膜脂肪体积与冠状动脉粥样硬化及左心室舒张功能的相关性研究

目的:通过双源64排CT对心外膜脂肪(EAT)进行三维立体重建,并测量其体积,探讨与冠心病发生、病变程度、斑块类型及早期心功能变化的关系。方法:临床疑诊冠心病(CAD)患者131例为研究对象,男性93例,女性38例,平均年龄(56±10)岁,收集所有病例一般临床资料,静脉取血行血脂、血常规及肝肾功能检查。超声心动图明确左心功能情况。所有患者均行冠状动脉64排双源CT血管成像检查,评价冠状动脉内斑块类型及稳定性,应用Vitrea FX(Vital Images)工作站的cardiac fat软件对EAT进行三维重建并测量其体积;根据冠状动脉造影结果确诊冠心病,并评价冠状动脉病变血管支数、病变部位及管腔狭窄程度。结果:冠心病组(n=63)EAT体积明显大于非冠心病组(n=68,P=0.003);冠状动脉3支病变者EAT体积,较1支及2支病变者明显增多(P<0.05);冠状动脉单纯低密度斑块者EAT体积较无斑块和单纯钙化者明显增大(P<0.001)。Pearson相关分析显示:EAT体积与腰围成正相关(r=0.475,P<0.001),与BMI成正相关(r=0.386,P<0.001)。Logistic回归分析显示EAT体积是冠心病的独立危险因素(OR=1.018,95%CI 1.004～1.033,P=0.011)。2组中左心室舒张功能减低者EAT体积均明显增加(P<0.05),EAT体积与左心室舒张末期内径明显正相关(r=0.331,P<0.001),与室间隔厚度正相关(r=0.195,P=0.031)。结论:EAT含量的增多与冠心病的发生、冠状动脉病变支数及易损斑块的形成密切相关,参与了左心室舒张功能的损伤过程,可能是冠心病新的危险因素,将可能是评价心血管疾病风险增加的新的无创指标,及潜在的治疗靶点。     

血管内影像技术的新进展

近年来血管内影像技术,特别是血管内超声领域的研究进展,主要包括:(1)对易损斑块认识的不断深入和检测率的逐步提高;(2)更有效地指导冠状动脉介入治疗,特别是指导药物洗脱支架的置入和随访。多种新型血管内影像技术日趋成熟,包括虚拟组织学血管内超声、整合背向散射血管内超声、光学相干断层成像术、近红外光谱仪、血管镜及血管内磁共振与传统的灰阶血管内超声一起,推动着血管内影像技术进入崭新的阶段。     

光学相干断层成像对急性冠状动脉综合征患者易损斑块的新认识

血管斑块的稳定性是影响急性冠状动脉综合征发生发展的主要因素,具有超高空间分辨率的光学相干断层成像(OCT)技术在易损斑块识别方面有着独特的优势。本文就近年来OCT在急性冠状动脉综合征患者易损斑块识别方面的临床新进展进行综述。     

冠状动脉CT成像与易损斑块

冠状动脉内斑块破裂或侵蚀所致的急性腔内血栓是急性冠状动脉综合征的主要原因。防止急性血栓形成成为了降低冠状动脉粥样硬化性心脏病病死率的唯一有效策略。斑块易破裂的冠状动脉病变与稳定斑块相比,存在不同的形态学改变。因此可以利用特殊的成像方法来识别这些易损斑块。亚毫米空间分辨率和图像质量优良的现代计算机断层扫描方法可以对冠状动脉斑块进行检测、分析和量化。斑块体积较大、低CT衰减、餐巾环征、正性重构以及点状钙化等与斑块容易破裂有密切关系。将冠状动脉斑块的形态学与功能特征等相结合,在未来有可能成为检测易损斑块的新方法。现将就多层螺旋CT与冠状动脉易损斑块的检测做一综述。     

Assessment of coronary artery disease using coronary computed tomography angiography and biochemical markers

Chronic inflammatory mechanisms in the arterial wall lead to atherosclerosis,and include endothelial cell damage,inflammation,apoptosis,lipoprotein deposition,calcification and fibrosis.Cardiac computed tomography angiography(CCTA)has been shown to be a promising tool for non-invasive assessment of theses specific compositional and structural changes in coronary arteries.This review focuses on the technical background of CCTA-based quantitative plaque characterization.Furthermore,we discuss the available evidence for CCTA-based plaque characterization and the potential role of CCTA for risk stratification of patients with coronary artery disease.     

妊娠相关蛋白-A对冠心病易损斑块的预测价值

目的:探讨妊娠相关蛋白A(PAPP-A)与冠心病及斑块易损性之间的关系。方法:选择急性冠状动脉综合征(ACS组)患者20例,稳定性心绞痛(SAP组)患者19例,采用ELISA测定患者血清中PAPP-A水平,同时应用光学相干断层成像技术测定患者斑块纤维帽厚度。结果:ACS组PAPP-A高于SAP组[(48.71±18.90)ng/L∶(18.93±11.11)ng/L,P<0.01];ACS组斑块纤维帽厚度低于SAP组[(45.44±18.25)μm∶(90.74±24.54)μm,P<0.01]。ACS组中PAPP-A与斑块纤维帽厚度呈负相关,r=-0.778,P<0.01。逐步(Stepwise)多重线性回归分析认定PAPP-A是预测斑块易损性的一种独立危险因素。结论:PAPP-A是一种独立的、能够有效预测冠心病风险以及斑块易损性的标记物。     

冠状动脉易损斑块的治疗进展

动脉粥样硬化是全身性、慢性炎症性疾病,以局部突出表现为主。冠状动脉粥样硬化是冠状动脉性心脏病最主要病因,冠状动脉性心脏病患者发生急性冠状动脉事件的后果十分严重,常危及生命,而易损斑块是导致急性冠状动脉综合征主要罪犯病变。因此,对易损斑块的早期识别以及积极干预,对于预防急性心血管事件的发生至关重要,具有非常重要的临床意义。现就冠状动脉易损斑块的治疗最新进展做一综述。     

血管内超声在冠状动脉临界病变诊断及治疗中的应用

血管内超声是近年来发展起来的一项新的影像学技术,在冠心病的诊断与治疗中有着重要的应用价值,尤其对临界病变的评估有着很好的指导作用。该项技术的问世,不仅使冠状动脉临界病变的检出越来越多,而且在识别易损斑块方面有着突出的贡献,从而指导冠心病临界病变患者选择合适的治疗方案,进行及早干预,减少心血管事件的发生。因此,在冠状动脉造影中应用血管内超声检查已然成为目前诊断和治疗冠状动脉临界病变的热点问题。