Coronary plaque erosion without rupture into a lipid core. A frequent cause of coronary thrombosis in sudden coronary death

Limitation of angiography to identify the culprit plaque in acute myocardial infarction with coronary total occlusion utility of coronary plaque temperature measurement to identify the culprit plaque

OBJECTIVES

The purpose of this study was to test the hypothesis that the maximal temperature (Tmax) site, as measured by thermal wire, coincides with the culprit plaque by intravascular ultrasound (IVUS) in patients with acute myocardial infarction (AMI).

BACKGROUND

Subsequent thrombosis developing to the proximal region from the site of plaque rupture or erosion can potentially complicate the ability of coronary angiography to identify the accurate culprit plaque in patients with coronary total occlusion.

METHODS

In 45 consecutive patients with a first anterior AMI, the Tmax site by thermal wire and the culprit plaque by IVUS were evaluated in the left anterior descending coronary artery (LAD).

RESULTS

Twenty-five patients had LAD total occlusion, and the remaining 20 had LAD reperfusion. In both groups of patients, the Tmax site was significantly more distal to the angiographically most stenotic site or occlusive site (reperfusion: mean distance [MD] = 1.1 mm distal, 95% confidence interval [CI] 0.3 to 1.9 mm, p = 0.01; total occlusion: MD = 8.8 mm distal, 95% CI 8.0 to 9.6 mm, p < 0.0001). The culprit plaques by IVUS approximately coincided with those by angiography or thermal wire in patients with reperfusion. However, the angiographic occlusive site was significantly more proximal to the culprit plaque by IVUS (MD = 9.2 mm, 95% CI 7.9 to 10.6 mm, p < 0.0001), but the Tmax site coincided with the culprit plaque by IVUS (MD = 0.3 mm distal, 95% CI 0.3 mm proximal to 1.0 mm distal, p = 0.293) in patients with total occlusion.

CONCLUSIONS

Temperature measurement of coronary plaque enables accurate localization of the culprit plaque in AMI with coronary total occlusion.

Neopterin is associated with plaque inflammation and destabilisation in human coronary atherosclerotic lesions

BACKGROUND

Previous studies have shown that recent activation of the inflammatory response in coronary atherosclerotic lesions contributes to rapid progressive plaque destabilisation. Neopterin, a by-product of the guanosine triphosphate pathway, is produced by activated macrophages and serves as an activation marker for monocytes/macrophages.

OBJECTIVE

To elucidate the role of neopterin in coronary plaque destabilisation by immunohistochemical study of the presence of neopterin in coronary atherectomy specimens obtained from patients with stable angina pectoris (SAP) and unstable angina pectoris (UAP).

PATIENTS AND METHODS

All patients underwent atherectomy of the primary atherosclerotic lesions responsible for SAP (n = 25) and UAP (n = 25). Frozen samples were studied with antibodies against smooth muscle cells, macrophages, T cells, neutrophils and neopterin.

RESULTS

In 22/25 patients with UAP, abundant neopterin-positive macrophages were found at the sites of coronary culprit lesions. However, in 25 lesions from patients with SAP, only 11 lesions showed neopterin positivity. Quantitatively, the neopterin-positive macrophage score was significantly higher (p<0.001) in patients with UAP than in patients with SAP. Moreover, the neopterin-positive macrophage score showed a significant positive correlation with the number of neutrophils or T cells, respectively (neutrophils, r = 0.55, p<0.001; T cells, r = 0.70, p<0.001).

CONCLUSIONS

Neopterin can be considered as one of the significant factors in the process of plaque inflammation and destabilisation in human coronary atherosclerotic lesions. Its exact role in the process needs to be investigated further.

Pathophysiology of plaque disruption and thrombosis in acute ischemic syndromes

Atherosclerosis is a systemic disease responsible for strokes, myocardial infarction, renal hypertension, and intermittent claudication. Acute coronary syndromes (unstable angina, acute myocardial infarction, and sudden cardiac death) are the major causes of morbidity and mortality in developed countries. These acute manifestations of heart disease share a common pathophysiologic phenomenon: coronary thrombosis. Two principal mechanisms are responsible for coronary thrombosis: plaque disruption (75%) and plaque erosion (25%). Disrupted plaques exhibit a large lipid content, increased macrophages, and a thin fibrous cap. Hypercholesterolemia and diabetes are associated with plaque disruption. Eroded plaques are smooth muscle-cell rich with an intact fibrous cap. Cigarette smoking is associated with plaque erosion, most frequently in women with sudden death when they are younger than 50 years of age. Systemic inflammation is a novel, robust marker for future cardiovascular events, not only in patients with established atherosclerotic disease but also in apparently healthy individuals. Local inflammation at the plaque disruption site is documented by increased macrophage infiltration. Macrophages are responsible for plaque disruption, neovascularization, smooth muscle cell apoptosis, and plaque thrombogenicity. Experimental studies have identified the lipid core as the most thrombogenic substrate of the atherosclerotic plaque. Tissue factor, a cell membrane-bound protein, is crucial in thrombus formation. Tissue factor is expressed in apoptotic macrophages, suggesting that macrophages are not only responsible for plaque disruption but also pivotal in thrombus generation, the most important mechanism of acute coronary syndromes.

From vulnerable plaque to vulnerable patient: the search for biomarkers of plaque destabilization

There is a strong need for biomarkers to identify patients at risk for future cardiovascular events related with progressive atherosclerotic disease. Ideally, increasing knowledge of the mechanisms of atherosclerotic plaque destabilization should be translated in clinical practice. Currently, the following commonly followed strategies can be identified with the objective to detect either the local vulnerable plaque that is prone to rupture and gives rise to a thrombotic occlusion, or the systemic vulnerable patient, who has a high probability to suffer from an adverse clinical event. On the one hand, studies are ongoing to determine local atherosclerotic plaque characteristics to predict future local plaque rupture and subsequent vascular thrombosis. Newly developed imaging modalities are being developed and validated to detect these plaques in vivo. On the other hand, systemic approaches are pursued to discover serum biomarkers that are applicable to define patients at risk for future cardiovascular events. We propose a third original approach that is optional but yet unexplored, that is, to use local plaque characteristics as a biomarker not just for local plaque destabilization but for future cardiovascular events due to plaque progression in any vascular system. This review aims to provide an overview of the current standings of the identification of the vulnerable plaque and the vulnerable patient.

Carotid artery plaque thickness is associated with increased serum calcium levels: the Northern Manhattan study

BACKGROUND

Elevated serum calcium concentrations are associated with vascular calcification and cardiovascular disease. It is unknown whether there is a relationship between high-normal serum calcium levels and sub-clinical vascular effects. We investigated the association between serum calcium and carotid plaque thickness, a powerful early predictor of clinical coronary and cerebrovascular events.

METHODS

Epidemiological study of 1194 subjects from the Northern Manhattan Study cohort, a prospective community-based study designed to investigate risk factors for vascular disease in different race-ethnic groups.

RESULTS

Subjects with carotid plaque had higher corrected serum calcium levels within the normal range than those without carotid plaque (2.21+/-0.09 mmol/L versus 2.19+/-0.09 mmol/L, p<0.002). The relationship between carotid plaque and serum calcium persisted after adjustment for traditional cardiovascular risk factors. Subjects in the top quintile of maximal carotid plaque thickness (>or=1.7 mm) were more likely to be in the highest quintile of serum calcium level (OR=1.64, 95% CI=1.17-2.29, p<0.004). The interaction of age and corrected serum calcium was the most significant predictor of carotid plaque thickness when traditional vascular risk factors were considered (p<0.001).

CONCLUSIONS

Serum calcium levels in a multi-ethnic population of older men and women were positively associated with carotid plaque thickness, a powerful early predictor of clinical coronary and cerebrovascular events.

Molecular mechanisms of plaque instability

PURPOSE OF REVIEW

Coronary artery thrombosis superimposed on a disrupted atherosclerotic plaque initiates abrupt arterial occlusion and is the proximate event responsible for 60-80% cases of acute coronary syndromes. This article provides a concise update on the evolving concepts in the pathophysiology of plaque rupture and thrombosis.

RECENT FINDINGS

Over the past several years, the critical role of plaque composition rather than plaque size or stenosis severity, in plaque rupture and thrombosis have been recognized. The necrotic lipid core and plaque inflammation appear to be key factors. Extracellular matrix loss in the fibrous cap, a prelude to rupture, is attributed to matrix degrading enzymes as well as to death of matrix synthesizing smooth muscle cells; inflammation appears to play a critical role in both these processes. Inflammatory cell derived tissue factor is a key contributor to plaque thrombogenicity. Inflammation has also been implicated in plaque neovascularity, intraplaque hemorrhage and plaque expansion. Recent observations have also highlighted the important modulatory role of immune system in atherosclerosis and plaque composition.

SUMMARY

Improved understanding of mechanisms causing plaque instability should provide novel insights into prevention of athero-thrombotic cardiovascular events.

Impact of plaque rupture on infarct size in ST-segment elevation anterior acute myocardial infarction

OBJECTIVES

We sought to assess whether coronary plaque rupture at culprit lesions is associated with infarct size in patients with anterior acute myocardial infarction (AMI).

BACKGROUND

Some patients with AMI have large infarcts despite early reperfusion. Whether culprit plaque morphology impacts infarct size or not remains unknown.

METHODS

Patients who had a first anterior AMI with reperfusion within 6 hours after onset were enrolled and divided into 2 groups according to the presence or absence of plaque rupture at the culprit lesion as defined by preintervention intravascular ultrasound (IVUS): patients with rupture (n = 54) and without rupture (n = 37).

RESULTS

Patients with plaque rupture had a higher incidence of no-reflow phenomenon (15% vs. 3%; p = 0.08) and a lower myocardial blush grade (1.5 vs. 2.3; p < 0.05) after percutaneous coronary intervention. The IVUS analysis showed that patients with plaque rupture had a higher incidence of soft plaque and positive remodeling. Peak creatine kinase levels were higher (4,707 vs. 2,309 IU/l; p < 0.0001) and left ventricular ejection fraction in the chronic phase was lower (54% vs. 63%; p < 0.01) in patients with plaque rupture. A multivariate logistic regression analysis revealed that plaque rupture and the proximal lesion site correlated with a left ventricular ejection fraction of <50% in the chronic phase (odds ratios 6.5 and 17.5, respectively; p < 0.05).

CONCLUSIONS

Plaque rupture is associated with morphologic characteristics of vulnerable lesions, as well as with larger infarcts and a higher incidence of no-reflow phenomenon, suggesting that plaque embolism contributes to the progression of myocardial damage in patients with anterior AMI.

Improved identification of endothelial erosion by simultaneous detection of endothelial cells (CD31/CD34) and platelets (CD42b)

Loss of endothelial cells (ECs) with ensuing exposure of thrombogenic subendothelial surface is a common cause of thromboembolic complications in atherosclerotic arteries. Thus, endothelial denudation has emerged as a major contributor to the pathogenesis of atherosclerosis and its complications. Despite ongoing efforts in elucidating the pathogenesis of endothelial erosions in human atherosclerotic arteries, the mechanisms of erosion have remained enigmatic, partly due to lack of well-established methods for its identification. Here the authors point out plausible pitfalls in the current methodology and provide an improved immunohistochemical method for identifying endothelial erosion; i.e., immunofluorescence double staining with antibodies against CD42b and CD31/CD34. This method enables reliable detection of ECs and platelets in the same staining by allowing detection of "pseudoendothelium" caused by CD31 staining of a thin platelet layer covering sites of endothelial erosion. As erosion with a luminal platelet thrombus is likely to represent an in vivo erosion, and erosion without platelets an ex vivo artefact, the method makes it possible to exclude artefactual erosions resulting from sample processing. The novel immunostaining protocol presented here allows more reliable detection of endothelial erosions and so may facilitate studies on the mechanisms involved in the pathogenesis of plaque erosion and acute coronary syndromes.

Pathology of atherosclerosis and stenting

Atherosclerotic plaque at the carotid bifurcation is the primary cause of ischemic strokes and the degree of carotid stenosis is strongly associated with stroke risk in symptomatic patients. Stroke is the third-leading cause of death in the United States, constituting approximately 700,000 cases each year. In this article, the authors discuss the natural history of carotid and intracranial atherosclerosis, based on their broader knowledge of coronary atherosclerosis. Early to more advanced progressive lesions of the carotid are categorized, based on descriptive morphologic events originally cited for the coronary circulation. The histologic features associated with symptomatic and asymptomatic carotid disease are also addressed, along with the issues surrounding current stent-based therapies for the prevention of major recurrent vascular events.

Plaque vulnerability and related coronary event prediction by intravascular ultrasound with virtual histology: "it's a long way to tipperary"?

Identification of so-called "vulnerable plaque" or "high-risk" plaques have spawned manifold attempts to develop diagnostic tools capable to afford this task. This task is particularly challenging but the reward is high: local intervention on identified "vulnerable plaque" could preclude plaque thrombosis and possibly prevent acute coronary syndromes. Various imaging techniques are currently under investigation by extensive clinical testing to identify which could become the most sensible and specific modality for vulnerable plaque detection. Noninvasive techniques are fascinating for their easily applicability to a broad population but nowadays are not sufficiently powered for this task. The emerging technologies with the greatest resolution are indeed catheter-based and many intravascular modalities have been developed for identification of "vulnerable plaque". Among these, IVUS-Virtual Histology (IVUS-VH) is the most promising technique in the field. IVUS-VH offers an in vivo opportunity to assess plaque morphology and histology. IVUS-VH uses underlying frequency information along with echoes intensity, while grey-scale IVUS data are obtained from echoes of different intensity or amplitude. The major advantage of IVUS-VH is that it is based on a device that is practical for use in the clinical setting and that it generates a real-time assessment of plaque morphology. Unfortunately, numerous challenging issues still need to be overcome until the numerous "vulnerable plaques" could be identified and successfully treated. Future efforts may identify plaques that are on a trajectory of evolution toward a vulnerable state, and help us target interventions to those plaques most likely to develop plaque disruption and related complications.

Pathophysiology of acute myocardial infarction

More than 80% of acute myocardial infarcts are the result of coronary atherosclerosis with superimposed luminal thrombus. Uncommon causes of myocardial infarction include coronary spasm, coronary embolism, and thrombosis in nonatherosclerotic normal vessels. Additionally, concentric subendocardial necrosis may result from global ischemia and reperfusion in cases of prolonged cardiac arrest with resuscitation. Myocardial ischemia shares features with other types of myocyte necrosis, such as that caused by inflammation, but specific changes result from myocyte hypoxia that vary based on length of occlusion of the vessel, duration between occlusion and reperfusion, and presence of collateral circulation.

Atherogenesis: the role of inflammation and infection

Atherosclerosis is no longer considered a disorder of lipid accumulation, but a disease process characterized by the dynamic interaction between endothelial dysfunction, subendothelial inflammation and the 'wound healing response' of the vascular smooth muscle cells. Prospective epidemiological studies have unequivocally demonstrated increased vascular risk in individuals with elevated levels of (i) cytokines such as interleukin-6 and tumour necrosis factor-alpha, (ii) cell adhesion molecules such as intercellular adhesion molecule-1 and P-selectin, and (iii) acute-phase proteins such as C-reactive protein, fibrinogen and serum amyloid A. Furthermore, evidence from clinical trials have demonstrated that risk reduction achieved with anti-inflammatory agents such as statins is significantly greater in patients with evidence of inflammation. A number of risk factors for atherogenesis, including infectious agents, have been shown to exert their influence via inflammatory mechanisms. However, despite compelling experimental evidence, clinical studies looking at the role of infection in atherogenesis have lacked consistency. The clinical product of this dynamic process is variable and unpredictable between individuals, even those with apparently similar risk profiles.

Serial intravascular ultrasonic study of outcomes of coronary culprit lesions with plaque rupture following bare metal stent implantation in patients with angina pectoris

Coronary culprit lesions with plaque rupture (PR) have been treated with different coronary interventions. However, it is unknown whether the presence of PR affects the restenotic process after coronary intervention. One hundred forty-two patients undergoing coronary bare metal stent implantation were enrolled in the present retrospective analysis. Case selection was based on availability of intravascular ultrasound (IVUS) and quantitative coronary angiographic examinations at baseline (before and after intervention) and at follow-up. Serial comparative analyses included qualitative and quantitative features of the culprit lesion and reference segments. PR was defined as an intraplaque cavity in communication with the lumen in the presence of a residual, disrupted cap. Patients were categorized according to the presence/absence of PR. Pre-interventional IVUS detected PR in 54 patients (38%). Baseline patient demographics were similar between the +PR and -PR groups. Quantitative IVUS analysis showed higher rates of positive remodeling and larger vessel and plaque areas in the +PR compared with -PR lesions (p <0.001 for all). At follow-up (7.2 +/- 2.6 months), no statistically significant difference was observed between the 2 groups in quantitative coronary angiographic or IVUS measurements. In conclusion, culprit lesions with PR exhibited larger plaque mass and higher rates of positive remodeling at preintervention IVUS examination. However, when treated with bare metal stents, the absence/presence of preintervention PR was not found to affect the rate or severity of in-stent restenosis in these culprit lesions.

Hemodynamic factors and atheromatic plaque rupture in the coronary arteries: from vulnerable plaque to vulnerable coronary segment

Coronary plaque disruption with superimposed thrombosis is the underlying pathology in the acute coronary syndromes and sudden death. Coronary plaques are constantly stressed by a variety of mechanical and hemodynamic forces that may precipitate or 'trigger' disruption of vulnerable or, at extreme conditions, even stable plaques. This paper reviews the exciting new evidence on the hemodynamic factors that may play a role in this process and provides the rationale for the introduction of the concept of the vulnerable coronary segment in the study of acute coronary syndromes.

Shear stress-induced changes in atherosclerotic plaque composition are modulated by chemokines

We previously found that low shear stress (LSS) induces atherosclerotic plaques in mice with increased lipid and matrix metalloproteinase content and decreased vascular smooth muscle and collagen content. Here, we evaluated the role of chemokines in this process, using an extravascular device inducing regions of LSS, high shear stress, and oscillatory shear stress (OSS) in the carotid artery. One week of shear stress alterations induced expression of IFN-gamma-inducible protein-10 (IP-10) exclusively in the LSS region, whereas monocyte chemoattractant protein-1 (MCP-1) and the mouse homolog of growth-regulated oncogene alpha (GRO-alpha) were equally upregulated in both LSS and OSS regions. After 3 weeks, GRO-alpha and IP-10 were specifically upregulated in LSS regions. After 9 weeks, lesions with thinner fibrous caps and larger necrotic cores were found in the LSS region compared with the OSS region. Equal levels of MCP-1 expression were observed in both regions, while expression of fractalkine was found in the LSS region only. Blockage of fractalkine inhibited plaque growth and resulted in striking differences in plaque composition in the LSS region. We conclude that LSS or OSS triggers expression of chemokines involved in atherogenesis. Fractalkine upregulation is critically important for the composition of LSS-induced atherosclerotic lesions.

Vascular wall-produced prostaglandin E2 exacerbates arterial thrombosis and atherothrombosis through platelet EP3 receptors

Prostanoids, bioactive lipids derived from arachidonic acid (AA), are important for vascular homeostasis. Among them, prostaglandin E2 (PGE2) enhances aggregation of platelets submaximally stimulated in vitro. This results from activation of EP3, one of the four PGE2 receptors, which decreases the threshold at which agonists activate platelets to aggregate. Although PGE2 altered venous thrombosis induced by administration of AA, its role in pathophysiopathological conditions has remained speculative. We report that arterial walls subjected to inflammatory stimuli produce PGE2. In several models, we show that PGE2 produced by the arterial wall facilitates arterial thrombosis. Next, we detected PGE2 in mouse atherosclerotic plaques. We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3. In addition, we present evidence that PGE2 can leave the plaque and activate EP3 on blood platelets. Consistent with these findings, we observed that atherothrombosis induced in vivo by mechanical rupture of the plaque was drastically decreased when platelets lacked EP3. In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis. Inhibition of the platelet EP3 receptor should improve prevention of atherothrombosis.

Magnetic resonance imaging of ruptured plaques in the rabbit with ultrasmall superparamagnetic particles of iron oxide

BACKGROUND

Magnetic resonance imaging (MRI) enhanced with ultrasmall superparamagnetic particles of iron oxide (USPIO) has previously been evaluated in hyperlipidemic rabbits. The aim of this study was therefore to compare USPIO in ruptured and non-ruptured arteries in an atherosclerotic rabbit model.

METHODS

Atherosclerotic-like lesions were induced by the combination of endothelial abrasion and high-cholesterol diet in iliac rabbit arteries (n = 16). Rupture of atherosclerotic lesions was realized by oversized balloon angioplasty in one iliac artery, whereas the contralateral artery was used as control. USPIO (ferumoxtran-10: 1 mmol Fe/kg) was administered immediately (n = 10) or 28 days (n = 6) after injury. MRI and histological analysis were performed 7 and 35 days after injury and in control arteries.

RESULTS

In vivo MRI analysis showed extended susceptibility artifact with transluminal signal loss in all ruptured arteries 7 days after injury. In contrast, hyposignal was reduced 35 days following injury (i.e. after healing), and absent in non-ruptured arteries. Similarly, histological analysis of iron uptake was significantly increased 7 days after injury compared to healed-ruptured and control arteries.

CONCLUSIONS

Accumulation ofUSPIO is significantly increased in ruptured as compared to non-ruptured arteries in the atherosclerotic rabbit model.

Clinical applications of optical coherence tomography

Rupture of vulnerable plaque (VP) is responsible for most coronary events. Optical coherence tomography (OCT) is a high-resolution imaging method that allows excellent characterization of atherosclerotic plaque. While this technique is limited by the need to interrupt blood flow and a shallow depth of penetration, its resolution is an order of magnitude greater than possible with intravascular ultrasound (IVUS), and it has demonstrated better sensitivity and specificity for accurately determining plaque composition. Early in vitro and in vivo experiences have affirmed the excellent quality of these images making it an attractive technology for the analysis of VP. Its high resolution likely renders it the best imaging modality currently available for the evaluation of proper stent deployment and of intracoronary pathology in the setting of percutaneous coronary interventions (PCI). Our institution is currently involved in a multicenter trial to evaluate the effectiveness of OCT when compared to IVUS in this setting. Ongoing technological improvements aim to permit rapid scanning which should alleviate its current major limitation of needing to scan in a blood-free space. OCT is a promising new technology in the evaluation of atherosclerotic plaque and coronary microstructure.

Computed tomography calcium quantification as a measure of atherosclerotic plaque morphology and stability

OBJECTIVES

We examined the relationship between computed tomography (CT)-quantified calcium and histopathologic atherosclerotic plaque morphology and rupture.

MATERIALS AND METHODS

Seven aortae were harvested from autopsy cases. All were scanned, ex vivo, on a 16-slice CT scanner and CT calcium scores (CTCS) were calculated using a Siemens Calcium Scoring package. The aorta segments were physically cross sectioned at 3-mm intervals corresponding to CT reconstructions. Two pathologists evaluated the cross sections for histology calcium score (HCS), plaque fibrous cap disruption, overlying thrombus, internal hemorrhage, size, lipid content, and inflammation. CT and histology data were subsequently paired using predetermined quadrant and slice conventions.

RESULTS

Three hundred forty-nine aorta cross sections yielded 41 atherosclerotic plaques. Eleven plaques demonstrated plaque disruption and thrombosis and all contained calcium. CTCS was not significantly different between atherosclerotic plaques with and without evidence of disruption/thrombosis (F[1,30] = 1.525, P = 0.227). CT was 100% sensitive for nodular calcification, but only 56% (5 of 9 plaques) sensitive for non-nodular calcification. There was no significant relationship between CTCS and intraplaque hemorrhage, lipid content, inflammation, and plaque size (P = 0.179, P = 0.230, P = 0.314, and P = 0.054). There was significant correlation between CTCS and HCS (Pearson coefficient = 0.535; P < 0.01).

CONCLUSIONS

Calcium quantity does not appear to predict plaque morphology or likelihood of rupture. CT has lower sensitivity for non-nodular compared with nodular calcification.

Impact of histological plaque characteristics on intravascular ultrasound parameters at culprit lesions in coronary artery disease

Prior intravascular ultrasound (IVUS) studies have demonstrated that a positive remodeling pattern of a culprit lesion is observed more frequently in acute coronary syndrome (ACS) than stable angina (SA). However, the relationship between the plaque morphology detected by IVUS and the histological type of atherosclerotic plaque has not been well defined. This is a prospective study on 37 consecutive patients who underwent directional coronary atherectomy. The 37 patients were divided into 2 groups; 21 patients with SA and 16 with ACS. Vessel and plaque cross sectional area were measured at the culprit lesion and the remodeling index (RI) was calculated by IVUS. The plaque tissue was assessed for the presence of inflammatory cells and lipids, and the presence of each was scored as 0 (absent), 1 (sparse), 2 (dense), or 3 (predominant). The RI of the patients with ACS was higher than that of SA. Inflammatory cells were present to a greater extent in patients with ACS. Inflammatory cells and lipids were significantly correlated with the RI (Inflammatory cell score grade > or = 2 patients; 1.14 +/- 0.13 versus grade 0 patients; 0.87 +/- 0.24, and grade 1 patients; 0.93 +/- 0.17, P < 0.01 and lipid score grade > or = 2 patients; 1.13 +/- 0.17 versus grade 0 patients; 0.85 +/- 0.18, P < 0.001 and grade 1 patients; 0.95 +/- 0.19, P < 0.05). The results clearly indicate that the evaluation of vessel morphology by vascular imaging is an important indicator of plaque instability.

In vivo 18F-fluorodeoxyglucose positron emission tomography imaging provides a noninvasive measure of carotid plaque inflammation in patients

OBJECTIVES

Given the importance of inflammation in atherosclerosis, we sought to determine if atherosclerotic plaque inflammation could be measured noninvasively in humans using positron emission tomography (PET).

BACKGROUND

Earlier PET studies using fluorodeoxyglucose (FDG) demonstrated increased FDG uptake in atherosclerotic plaques. Here we tested the ability of FDG-PET to measure carotid plaque inflammation in patients who subsequently underwent carotid endarterectomy (CEA).

METHODS

Seventeen patients with severe carotid stenoses underwent FDG-PET imaging 3 h after FDG administration (13 to 25 mCi), after which carotid plaque FDG uptake was determined as the ratio of plaque to blood activity (target to background ratio, TBR). Less than 1 month after imaging, subjects underwent CEA, after which carotid specimens were processed to identify macrophages (staining with anti-CD68 antibodies).

RESULTS

There was a significant correlation between the PET signal from the carotid plaques and the macrophage staining from the corresponding histologic sections (r = 0.70; p < 0.0001). When mean FDG uptake (mean TBR) was compared with mean inflammation (mean percentage CD68 staining) for each of the 17 patients, the correlation was even stronger (r = 0.85; p < 0.0001). Fluorodeoxyglucose uptake did not correlate with plaque area, plaque thickness, or area of smooth muscle cell staining.

CONCLUSIONS

We established that FDG-PET imaging can be used to assess the severity of inflammation in carotid plaques in patients. If subsequent natural history studies link increased FDG-PET activity in carotid arteries with clinical events, this noninvasive measure could be used to identify a subset of patients with carotid atherosclerosis in need of intensified medical therapy or carotid artery intervention to prevent stroke.

Arterial calcification in mice after freeze-thaw injury

Vascular calcification is highly correlated with atherosclerosis and cardiovascular disease and is a significant predictor of cardiovascular morbidity and mortality. Studies in mice indicate a genetic contribution to this dystrophic extra osseous calcification. We sought to elaborate a method to induce dystrophic arterial calcification in mice and further examine the pathogenetical mechanisms involved in the phenotype. We established a method of freeze-thaw injury of the infrarenal aorta producing a limited tissue necrosis and histologically investigated the occurrence of dystrophic calcification within the aortic wall 1, 3 and 7 days after injury in C57BL/6 (a mouse strain shown to be resistant to dystrophic cardiac calcification after injury) and C3H/He (susceptible to dystrophic cardiac calcification). C57BL/6 mice exhibited no dystrophic calcification at all within the vessel wall upon injury of the infrarenal aorta (0/5 mice 1 day after injury and 0/10 animals 7 days after injury). By contrast C3H/He mice displayed a remarkable extent of calcification mainly present within the media of the infrarenal aorta which was evident as early as 24 h (three out of five animals 1 day after injury) and reached its maximum extent 7 days after injury (10 out of 10 animals at the seventh postoperative day, p<0.001 compared to C57BL/6 mice). Upon immuno-histological analysis calcification was accompanied by the occurrence of certain bone-matrix associated proteins. Osteopontin and Bone Morphogenetic Protein 2/4 expression was detected co-localized with the calcified lesions. Our results demonstrate that freeze-thaw injury of the infrarenal aorta is a sufficient method to induce dystrophic arterial calcification in mice. We present evidence that the occurrence of arterial calcification in C3H/He mice seems to be actively regulated by certain bone-matrix associated proteins.

Comparison of clinical and angiographic features and longterm follow-up events between patients with variant angina and patients with ST elevation myocardial infarction

We investigated to what extent patients with variant angina and significant coronary stenosis (>or=70%) present a clinical and angiographic profile similar to patients with ST elevation myocardial infarction. Thus, the clinical and angiographic features as well as follow-up events of 200 patients were prospectively analyzed and were compared with those of 422 patients with a first ST elevation myocardial infarction survivors of the early phase (3 days) and those of 70 patients with variant angina and non significant stenosis. Age and incidence of smoking, systemic hypertension, diabetes and maximum ST elevation were similar in the 2 groups. Furthermore, among patients with significant coronary stenosis, stenosis severity and the proportion of eccentric lesions were also comparable. Incidence of recent-within 30 days prior to admission-angina at rest was higher in variant angina patients with significant stenosis (67% vs. 27%, p<0.001) than in those with myocardial infarction but long standing angina at rest (>30 days) was low and comparable in these 2 groups (15% vs. 11%, ns). Also, in a 5-year follow-up most patients from these 2 groups were free from angina at rest (86% vs. 84%) which in variant angina patients was largely attributable to a high revascularization rate (72%). Moreover, the rate of myocardial infarction/cardiac death (20% vs. 19%) was also similar. Patients with variant angina and non-significant stenosis, however, had longer antecedent angina, more frequent follow-up angina and a lower incidence of cardiac events than the other 2 groups. Thus, these findings suggest that patients with variant angina and significant coronary stenosis generally behave as an acute coronary syndrome-likely associated with an acutely complicated plaque-rather than as recurrent vasospastic angina, and should be managed accordingly.

Thematic review series: Patient-Oriented Research. Imaging atherosclerosis: state of the art

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.

Activation of estrogen receptor-alpha reduces aortic smooth muscle differentiation

Women are at high risk of dying from unrecognized cardiovascular disease. Many differences in cardiovascular disease between men and women appear to be mediated by vascular smooth muscle cells (SMC). Because estrogen reduces the proliferation of SMC, we hypothesized that activation of estrogen receptor-alpha (ERalpha) by agonists or by growth factors altered SMC function. To determine the effect of growth factors, estrogen, and ERalpha expression on SMC differentiation, human aortic SMC were cultured in serum-free conditions for 10 days. SMC from men had lower spontaneous expression of ERalpha and higher levels of the differentiation markers calponin and smooth muscle alpha-actin than SMC from women. When SMC containing low expression of ERalpha were transduced with a lentivirus containing ERalpha, activation of the receptor by ligands or growth factors reduced differentiation markers. Conversely, inhibiting ERalpha expression by small interfering RNA (siRNA) in cells expressing high levels of ERalpha enhanced the expression of differentiation markers. ERalpha expression and activation reduced the phosphorylation of Smad2, a signaling molecule important in differentiation of SMC and initiated cell death through cleavage of caspase-3. We conclude that ERalpha activation switched SMC to a dedifferentiated phenotype and may contribute to plaque instability.

Global characterization of coronary plaque rupture phenotype using three-vessel intravascular ultrasound radiofrequency data analysis

AIMS

To compare the global characteristics of patients with and without evidence of plaque rupture (PR) in their coronary tree and to evaluate the phenotype of ruptured plaques using intravascular ultrasound (IVUS) radiofrequency data analysis (IVUS-VH).

METHODS AND RESULTS

Forty patients underwent three-vessel IVUS-VH interrogation. Twenty-eight PRs were diagnosed in 26 vessels (25.7% of the vessels studied) of 20 patients (50% of the population). Ruptures located in the left anterior descending were clustered in the proximal part of the vessel, whereas ruptures located in the right coronary artery were more distally located (P=0.02). Patients with at least one PR presented larger body mass index (BMI) (28.4+/-3.7 vs. 25.8+/-2.6 kg/m(2), P=0.01) and plaque burden (40.7+/-7.6 vs. 33.7+/-8.4%, P=0.01) than patients without rupture, despite showing similar lumen cross-sectional area (9.6+/-3.3 vs. 9.2+/-2.3 mm(2), P=0.60). Among current smokers, 66.7% presented a PR in their coronary tree. Finally, PR sites showed a higher content of necrotic core compared with minimum lumen area sites (17.48+/-10.8 vs. 13.10+/-6.5%, P=0.03) and a trend towards higher calcified component.

CONCLUSION

Patients with at least one PR in their coronary tree presented larger BMI and worse IVUS-derived characteristics compared with patients without PR.

The effect of atorvastatin on serum myeloperoxidase and CRP levels in patients with acute coronary syndrome

BACKGROUND

Inflammation is involved in the atherogenesis and pathogenesis of acute coronary syndrome (ACS). As the acute-phase reaction proteins in ACS, myeloperoxidase (MPO) and C-reactive protein (CRP) may play critical roles. Anti-inflammation may be one of benefits of statin drugs in ACS. Studies have showed that statins can suppress serum CRP concentrations. However, whether statins also reduce serum MPO concentrations in patients with ACS is unknown.

METHODS

Seventy-eight patients with ACS were randomly separated into Group A and Group B, the patients in Group A receiving conventional therapy, which include no cholesterol-lowering drugs, +atorvastatin (10 mg/day, n=40), the patients in Group B receiving conventional therapy (n=38). The serum concentrations of MPO were measured by enzyme-linked immunosorbent assay (ELISA) and CRP were measured by turbidimetric immunoassay.

RESULTS

Serum concentrations of MPO were significantly lower after 1-week therapy in both groups of patients [Group A from 590+/-168 to 496+/-154 microg/l, Group B from 570+/-165 to 521+/-153 microg/l; P<0.01, respectively]. Serum concentrations of CRP also were markedly lower than pretreatment [Group A from 6.56+/-1.87 to 5.14+/-2.07 mg/l; Group B from 6.36+/-1.94 to 5.45+/-1.90 mg/l, P<0.05, respectively]. Compared with conventional therapy alone, atorvastatin significantly further reduced serum MPO [P=0.014] and CRP concentrations [P=0.032]. There were no correlations detected between the reduction of MPO and CRP (r=0.124, P=0.068).

CONCLUSIONS

Atorvastatin reduced serum MPO and CRP concentrations in patients with ACS. These effects may explain some clinical benefits of statins in the treatment of these patients.

Accuracy of In Vivo Coronary Plaque Morphology Assessment

OBJECTIVES

The goal of the present study was to compare the accuracy of in vivo tissue characterization obtained by intravascular ultrasound (IVUS) radiofrequency (RF) data analysis, known as Virtual Histology (VH), to the in vitro histopathology of coronary atherosclerotic plaques obtained by directional coronary atherectomy.

BACKGROUND

Vulnerable plaque leading to acute coronary syndrome (ACS) has been associated with specific plaque composition, and its characterization is an important clinical focus.

METHODS

Virtual histology IVUS images were performed before and after a single debulking cut using directional coronary atherectomy. Debulking region of in vivo histology image was predicted by comparing pre- and post-debulking VH images. Analysis of VH images with the corresponding tissue cross section was performed.

RESULTS

Fifteen stable angina pectoris (AP) and 15 ACS patients were enrolled. The results of IVUS RF data analysis correlated well with histopathologic examination (predictive accuracy from all patients data: 87.1% for fibrous, 87.1% for fibro-fatty, 88.3% for necrotic core, and 96.5% for dense calcium regions, respectively). In addition, the frequency of necrotic core was significantly higher in the ACS group than in the stable AP group (in vitro histopathology: 22.6% vs. 12.6%, p = 0.02; in vivo virtual histology: 24.5% vs. 10.4%, p = 0.002).

CONCLUSIONS

Correlation of in vivo IVUS RF data analysis with histopathology shows a high accuracy. In vivo IVUS RF data analysis is a useful modality for the classification of different types of coronary components, and may play an important role in the detection of vulnerable plaque.

Clopidogrel in the treatment of ischaemic heart disease

Clopidogrel is an effective antiplatelet agent that has undergone rigorous assessment in the setting of ischaemic heart disease over the last decade. There is extensive evidence for the use of this drug in patients undergoing percutaneous coronary intervention, in those with stable ischaemic heart disease and also in those with acute coronary syndromes. This article examines the use of clopidogrel in patients with ischaemic heart disease.

Location of focal vasospasm provoked by ergonovine maleate within coronary arteries in patients with vasospastic angina pectoris

This study examined whether coronary focal vasospasm occurs in a nonuniform distribution within the coronary tree and whether a longitudinal plaque distribution pattern is present in patients with vasospastic angina using 3-dimensional intravascular ultrasound analysis. Of 121 patients with clinically suspected angina without fixed stenosis in the coronary arteries, vasospasm was provoked in 82 patients with 92 lesions (42 focal, 50 diffuse) by intravenous ergonovine maleate injection. Most focal vasospasms occurred in the proximal third of the coronary arteries (proximal 28, mid 8, distal 6, p <0.01), corresponding to the historical high-risk zones for acute coronary occlusion. More plaque burden also existed in the proximal third of the coronary arteries in patients with focal vasospasm.

Cytokines in Atherosclerosis: Pathogenic and Regulatory Pathways

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immunoinflammatory mechanisms are involved. Inflammation is central at all stages of atherosclerosis. It is implicated in the formation of early fatty streaks, when the endothelium is activated and expresses chemokines and adhesion molecules leading to monocyte/lymphocyte recruitment and infiltration into the subendothelium. It also acts at the onset of adverse clinical vascular events, when activated cells within the plaque secrete matrix proteases that degrade extracellular matrix proteins and weaken the fibrous cap, leading to rupture and thrombus formation. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis provided evidence that the immunoinflammatory response in atherosclerosis is modulated by regulatory pathways, in which the two anti-inflammatory cytokines interleukin-10 and transforming growth factor-β play a critical role. The purpose of this review is to bring together the current information concerning the role of cytokines in the development, progression, and complications of atherosclerosis. Specific emphasis is placed on the contribution of pro- and anti-inflammatory cytokines to pathogenic (innate and adaptive) and regulatory immunity in the context of atherosclerosis. Based on our current knowledge of the role of cytokines in atherosclerosis, we propose some novel therapeutic strategies to combat this disease. In addition, we discuss the potential of circulating cytokine levels as biomarkers of coronary artery disease.

Pathology of the Vulnerable Plaque

The majority of patients with acute coronary syndromes (ACS) present with unstable angina, acute myocardial infarction, and sudden coronary death. The most common cause of coronary thrombosis is plaque rupture followed by plaque erosion, whereas calcified nodule is infrequent. If advances in coronary disease are to occur, it is important to recognize the precursor lesion of ACS. Of the three types of coronary thrombosis, a precursor lesion for acute rupture has been postulated. The non-thrombosed lesion that most resembles the acute plaque rupture is the thin cap fibroatheroma (TCFA), which is characterized by a necrotic core with an overlying fibrous cap measuring <65 microm, containing rare smooth muscle cells but numerous macrophages. Thin cap fibroatheromas are most frequently observed in patients dying with acute myocardial infarction and least common in plaque erosion. They are most frequently observed in proximal coronary arteries, followed by mid and distal major coronary arteries. Vessels demonstrating TCFA do not usually show severe narrowing but show positive remodeling. In TCFAs the necrotic core length is approximately 2 to 17 mm (mean 8 mm) and the underlying cross-sectional area narrowing in over 75% of cases is <75% (diameter stenosis <50%). The area of the necrotic core in at least 75% of cases is < or =3 mm2. These lesions have lesser degree of calcification than plaque ruptures. Thin cap fibroatheromas are common in patients with high total cholesterol (TC) and high TC/high-density lipoprotein cholesterol ratio, in women >50 years, and in those patients with elevated high levels of high sensitivity C-reactive protein. It has only recently been recognized that their identification in living patients might help reduce the incidence of sudden coronary death.

Pathogenesis and early management of non-ST-segment elevation acute coronary syndromes

NSTE ACS is a clinically significant problem. Endothelial dysfunction triggered by traditional cardiovascular risk factors (and perhaps by other as yet unidentified risks) in the susceptible host leads to the formation and development of atherosclerotic plaque. Inflammatory mediators and mechanical stresses contribute to plaque rupture by disrupting the protective fibrous cap. In about 25% of patients who have ACS, typically those who are younger, female, or smokers, plaque erosion seems to be the main underlying pathologic mechanism. Endothelial alteration, inflammation,or exposure of the lipid core results in the release of TF, vWF, and PAF. The release of these factors leads to platelet activation and aggregation as well as to the formation of a fibrin clot, resulting in arterial thrombosis that occludes the vessel. A variety of factors, including circulating catecholamines, LDL levels, blood glucose levels, and systemic thrombogenic factors, can affect the extent and stability of the thrombus, thereby determining whether the occlusion is complete and fixed, labile and nonocclusive (NSTE ACS),or clinically silent resulting in a mural thrombus and plaque growth. The acute treatment of NSTEACS is directed at interrupting the prothrombotic environment surrounding the ruptured plaque; thus, antiplatelet agents such as aspirin, clopidogrel, and glycoprotein IIb/IIla receptor antagonists,as well as anticoagulants such as heparin, are the mainstays of early therapy.

Cell death in the cardiovascular system

Cell death is important for both development and tissue homeostasis in the adult. As such, it is tightly controlled and deregulation is associated with diverse pathologies; for example, regulated cell death is involved in vessel remodelling during development or following injury, but deregulated death is implicated in pathologies such as atherosclerosis, aneurysm formation, ischaemic and dilated cardiomyopathies and infarction. We describe the mechanisms of cell death and its role in the normal physiology and various pathologies of the cardiovascular system.

Cardiac hemodynamics, coronary circulation and interventional cardiology

Microcirculation is the functional end of the coronary circulation and it plays a key role in the regulation of coronary blood flow, both on the local and global scales. A good understanding of its function under physiological and pathophysiological conditions is crucial but, because of its micro-scale, access to this part of the coronary circulation is extremely difficult and requires a considerable amount of innovation and new technologies. Dynamics of the coronary circulation provide the true vehicle by which blood supply reaches the myocardium- coronary vasculature is only the conducting component of that vehicle. It is highly unlikely that the pulsatile nature of the flow, the capacitance of the conducting vessels and the constant pounding of coronary vasculature by surrounding tissue are not part of the design, regulation, and function of the coronary circulation. Interventions, whether to assess or to correct coronary stenosis, continue to be the main clinical avenue to dealing with coronary heart disease. Clinical decisions rely heavily on the ability to determine the true morphology of an occlusive lesion, to predict the future course of that lesion and to assess the functional toll on coronary blood supply which it will inflict at each stage.

Optical coherence tomography for imaging the vulnerable plaque

While our understanding of vulnerable coronary plaque is still at an early stage, the concept that certain types of plaques predispose patients to developing an acute myocardial infarction continues to be at the forefront of cardiology research. Intracoronary optical coherence tomography (OCT) has been developed to both identify and study these lesions due to its distinct resolution advantage over other imaging modalities. We review clinical research conducted at the Massachusetts General Hospital over the past five years to develop, validate, and utilize this technology to improve our understanding of vulnerable plaque. Our results show that intracoronary OCT may be safely conducted in patients and that it provides abundant information regarding plaque microscopic morphology, which is essential to the identification and study of high-risk lesions. Even though many basic biological, clinical, and technological challenges must be addressed prior to widespread use of this technology, the unique capabilities of OCT ensure that it will have a prominent role in shaping the future of cardiology.

Comparison of ruptured plaques in native coronary arteries and in saphenous vein grafts: an intravascular ultrasound study

Intravascular ultrasound (IVUS) has been used to describe ruptured plaques in saphenous vein grafts (SVGs) and native coronary arteries. We compared clinical, angiographic, and IVUS features of ruptured atherosclerotic plaques in SVGs and native coronary arteries. We identified 95 plaque ruptures in 76 SVGs in 73 patients. These lesions and patients were matched with 95 lesions and patients from a database of 468 native artery ruptures. The matching criterion was IVUS mean reference lumen area. Patients with ruptured SVG plaques were older (68.4 +/- 10.1 vs 65.0 +/- 10.6 years, p = 0.021), more often had hypercholesterolemia (92% vs 74%, p = 0.015) and hypertension (78% vs 62%, p = 0.059), and more often had a history of a remote myocardial infarction (57% vs 32%, p = 0.002). In contrast, anginal symptoms were similar in the 2 groups (70% to 75% of each group had an acute coronary syndrome). Most (90% to 95%) ruptured plaques in each group were classified as angiographically complex. However, ruptured SVG lesions more often had an angiographically visible intimal flap (71% vs 38%, p <0.001). More than 70% of lesions in the 2 groups had positive arterial remodeling by IVUS, but there was a tendency for a higher remodeling index in ruptured plaque SVG lesions (1.18 +/- 0.30 vs 1.11 +/- 0.20, p = 0.085). The site of the initial tear occurred mainly (in approximately 70%) at the plaque shoulders in the 2 groups. In conclusion, although patients with SVG plaque ruptures are older and have more co-morbidities, the clinical presentation and angiographic and IVUS features are remarkably similar to those of native artery plaque ruptures.

Lessons learnt from the autopsies of 445 cases of sudden cardiac death in adults

AIM

To determine the cause of sudden cardiac death in adults who underwent autopsy.

METHODS

Four hundred and forty-five sudden cardiac deaths occurred within 1 h of the symptoms onset, and all other cardiac and noncardiac causes having been excluded from autopsy and toxicology screening, were retrospectively identified from among 902 autopsies performed in a 2-year period on the island of Crete. The presence of acute coronary thrombi and myocardial infarction was documented macroscopically and by light microscopy and histology.

RESULTS

In all 445 cases, at least one coronary artery had evidence of moderate to advanced atherosclerosis. About two thirds were between 50 and 70 years. Men had a higher incidence than women, but with advancing age (>60 years) this difference was reduced. Myocardial infarction was found in 17 cases (11 acute; 6 acute and healed). Fifty-eight cases (13.0%) had coronary thrombi, mostly involving the left anterior descending and the right coronary arteries (81%); only six of these were associated with acute myocardial infarction.

CONCLUSION

In our population, arrhythmia was the most common cause of sudden cardiac death, while acute coronary thrombi and acute myocardial infarction were detected only in some cases. Because of the heterogeneity in the cause of sudden cardiac deaths in adults, a detailed forensic investigation may provide important information on the cause of death and help in the development of primary and secondary prevention.

Clinical implications and mechanisms of plaque rupture in the acute coronary syndromes

Coronary atherosclerosis complicated by plaque rupture or disruption and thrombosis is primarily responsible for the development of acute coronary syndromes. Plaques with a large extracellular lipid-rich core, a thin fibrous cap due to reduced collagen content and smooth muscle density, and increased numbers of activated macrophages and mast cells appear to be vulnerable to rupture. Plaque disruption tends to occur at points at which the plaque surface is weakest and most vulnerable, which coincide with points at which stresses resulting from biomechanical and hemodynamic forces acting on plaques are concentrated. Reduced matrix synthesis as well as increased matrix degradation predisposes vulnerable plaques to rupture in response to extrinsic mechanical or hemodynamic stresses. Modification of endothelial dysfunction and reduction of vulnerability to plaque rupture and thrombosis may lead to plaque stabilization. These concepts have significant clinical implications that are just beginning to be explored and incorporated into clinical practice. This article reviews the mechanism of coronary atherosclerosis development and the pathophysiology of acute coronary syndromes to provide a framework for understanding how plaque passivation might be accomplished in clinical medicine.

Some thoughts on the vasculopathy of women with ischemic heart disease

Considerable experimental and clinical data indicate that sex has an important influence on cardiovascular physiology and pathology. This report integrates selected literature with new data from the Women's Ischemia Syndrome Evaluation (WISE) on vascular findings in women with ischemic heart disease (IHD) and how these findings differ from those in men. A number of common vascular disease-related conditions are either unique to (e.g., hypertensive disorders of pregnancy, gestational diabetes, peripartum dissection, polycystic ovarian syndrome, etc.) or more frequent (e.g., migraine, coronary spasm, lupus, vasculitis, Raynaud's phenomenon, etc.) in women than men. Post-menopausal women more frequently have many traditional vascular disease risk conditions (e.g., hypertension, diabetes, obesity, inactivity, and so on), and these conditions cluster more frequently in them than men. Considerable evidence supports the notion that, with these requisite conditions, women develop a more severe or somewhat different form of vascular disease than men. Structurally, women's coronary vessels are smaller in size and appear to contain more diffuse atherosclerosis, their aortas are stiffer (fibrosis, remodeling, and so on), and their microvessels appear to be more frequently dysfunctional compared with men. Functionally, women's vessels frequently show impaired vasodilator responses. Limitations of existing data and higher risks in women with acute myocardial infarction, need for revascularization, or heart failure create uncertainty about management. A better understanding of these findings should provide direction for new algorithms to improve management of the vasculopathy underlying IHD in women.

Myeloperoxidase and its contributory role in inflammatory vascular disease

Myeloperoxidase (MPO), a heme protein abundantly expressed in polymorphonuclear neutrophils (PMN), has long been viewed to function primarily as a bactericidal enzyme centrally linked to innate host defense. Recent observations now extend this perspective and suggest that MPO is profoundly involved in the regulation of cellular homeostasis and may play a central role in initiation and propagation of acute and chronic vascular inflammatory disease. For example, low levels of MPO-derived hypochlorous acid (HOCl) interfere with intracellular signaling events, MPO-dependent oxidation of lipoproteins modulates their affinity to macrophages and the vessel wall, MPO-mediated depletion of endothelial-derived nitric oxide (NO) impairs endothelium-dependent vasodilatation, and nitrotyrosine (NO(2)Tyr) formation by MPO sequestered into the vessel wall may affect matrix protein structure and function. Future studies are needed to further elucidate the significance of MPO in the development of acute and chronic vascular disease and to evaluate MPO as a potential target for treatment.

Optical coherence tomography for identifying unstable coronary plaque

This manuscript examines intravascular imaging with optical coherence tomography (OCT). OCT is a potentially attractive intravascular imaging technology due to its high resolution, small catheters/guidewires, and ability to be combined with spectroscopic techniques. Its potential disadvantages remain its limited penetration and signal attenuation by blood. The manuscript reviews unstable plaque, OCT principles, historical development, current challenges, and comparison with IVUS.

Acute myocardial infarction: clinical characteristics and plaque morphology between expansive remodeling and constrictive remodeling by intravascular ultrasound

BACKGROUND

According to recent intravascular ultrasound (IVUS) studies, expansive remodeling (ER) at the culprit lesion has been observed in almost 50% of patients with acute coronary syndrome and constrictive remodeling (CR) in 30%. The purpose of this study is to investigate the difference between ER and CR at the culprit lesion in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

Preinterventional IVUS images of 73 patients with AMI were identified. The remodeling index (RI) was defined as the ratio of the external elastic membrane (EEM) areas at the culprit lesion to the EEM areas at the proximal reference site. Expansive remodeling was defined as an RI > 1.05; CR, as an RI < 0.95. In patients with AMI, 40 patients (55%) showed ER on IVUS, whereas CR was observed in 18 patients (25%). Patients with ER were significantly older than those with CR (P < .005). The frequency of the presence of calcifications was higher in patients with ER than in those with CR (P < .0005). In patients with AMI with ER, soft plaque with small calcium was the most frequent (58%). Multivariate analysis revealed that age and the presence of calcifications remained as independent predictors of ER.

CONCLUSIONS

These findings suggest that ER relates to old age and calcification, and CR may contribute to early plaque progression than ER in patients with AMI.

Carotid atherosclerotic plaques in patients with transient ischemic attacks and stroke have unstable characteristics compared with plaques in asymptomatic and amaurosis fugax patients

INTRODUCTION

Atherosclerotic carotid artery disease is responsible for a variety of clinical presentations, ranging from asymptomatic to cerebral ischemic events. Considering the upcoming use of noninvasive imaging modalities, plaque characteristics could serve as a marker in the selection of patients eligible for carotid endarterectomy (CEA). This would be more likely if characteristics corresponded with clinical manifestations and were predictive of future events. In this study, we hypothesized that plaque characteristics correlate with the clinical presentation of carotid artery disease.

METHODS

We included 404 patients undergoing a carotid endarterectomy (CEA). Ipsilateral clinical symptoms and duplex measurements were recorded. Patients could be asymptomatic (23.5%) or symptomatic with stroke (26.5%), transient ischemic attack (TIA) (36.1%), or amaurosis fugax (AFX) (13.9%). Plaques were stained and semi-quantitatively analyzed for the presence of macrophages, smooth muscle cells, collagen, calcifications, and thrombus. Plaques were categorized in three phenotypes by their overall presentation and the amount of fat. In addition, plaque matrix metalloproteinase (MMP) activity and cytokines expressions were measured.

RESULTS

Fibrous, fibro-atheromatous, and atheromatous plaques were observed in 30.2%, 35.6%, and 34.2%, respectively. Atheromatous plaques were more prevalent in patients with stroke and TIA compared with asymptomatic patients or patients with AFX (P = .001). Collagen staining was less evident in patients with TIA and stroke compared with asymptomatic patients or patients with AFX (P < .001). Plaques of patients with TIA and stroke showed significantly higher activity levels of MMP-8 and MMP-9 and higher levels of interleukin-8 compared with asymptomatic and AFX patients.

CONCLUSION

Plaque phenotype of patients with TIA is comparable to that of patients with stroke; whereas, the plaque phenotype of patients with AFX resembles the plaque phenotype of asymptomatic patients. Follow-up studies should be encouraged to determine whether plaque characteristics visualized by imaging techniques might help to identify patients most likely to benefit from CEA.

Clinical imaging of the vulnerable plaque in the coronary arteries: new intracoronary diagnostic methods

Rupture of a vulnerable plaque is the main cause of acute coronary syndromes and myocardial infarction. The features of rupture-prone atherosclerotic plaques have been previously described by pathologists. However, identification of vulnerable plaques in vivo is essential to study their natural history and to evaluate potential treatment modalities. Coronary angiography is the gold standard for the diagnosis of coronary artery disease, but it is unable to distinguish between stable and unstable plaques and to accurately predict future cardiac events. This current perspective describes the recently developed invasive imaging techniques to detect atherosclerotic vulnerable plaques in the coronary tree.

Molecular imaging of vulnerable atherosclerotic plaques

Despite primary and secondary prevention, serious cardiovascular events such as unstable angina or myocardial infarction still account for a third of all deaths worldwide. Therefore, identifying individual patients with vulnerable plaques at high risk for plaque rupture is a central challenge in clinical medicine. Several noninvasive techniques, such as magnetic resonance imaging, multislice computed tomography and electron beam tomography are currently being tested for their ability to identify such patients by morphological criteria. In contrast, noninvasive scintigraphic techniques use radiolabeled molecules to detect functional aspects in atherosclerotic plaques by visualizing its biologic activity. Based upon knowledge regarding the pathophysiology of atherosclerosis, various studies - in vitro, in vivo and first clinical trials - have used different tracers for plaque imaging studies, including radioactive labeled lipoproteins, components of the coagulation system, cytokines, mediators of the metalloproteinase system, cell adhesion receptors and even whole cells.