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

Sex differences in mortality following acute coronary syndromes

CONTEXT

Conflicting information exists about whether sex differences modulate short-term mortality following acute coronary syndromes (ACS).

OBJECTIVES

To investigate the relationship between sex and 30-day mortality in ACS, and to determine whether this relationship was modified by clinical syndrome or coronary anatomy using a large database across the spectrum of ACS and adjusting for potentially confounding clinical covariates.

DESIGN, SETTING, AND PARTICIPANTS

A convenience sample of patients pooled from 11 independent, international, randomized ACS clinical trials between 1993 and 2006 whose databases are maintained at the Duke Clinical Research Institute, Durham, North Carolina. Of 136 247 patients, 38 048 (28%) were women; 102 004 (26% women) with ST-segment elevation myocardial infarction (STEMI), 14 466 (29% women) with non-STEMI (NSTEMI), and 19 777 (40% women) with unstable angina.

MAIN OUTCOME MEASURE

Thirty-day mortality following ACS.

RESULTS

Thirty-day mortality was 9.6% in women and 5.3% in men (odds ratio [OR], 1.91; 95% confidence interval [CI], 1.83-2.00). After multivariable adjustment, mortality was not significantly different between women and men (adjusted OR, 1.06; 95% CI, 0.99-1.15). A significant sex by type of ACS interaction was demonstrated (P < .001). In STEMI, 30-day mortality was higher among women (adjusted OR, 1.15; 95% CI, 1.06-1.24), whereas in NSTEMI (adjusted OR, 0.77; 95% CI, 0.63-0.95) and unstable angina, mortality was lower among women (adjusted OR, 0.55; 95% CI, 0.43-0.70). In a cohort of 35 128 patients with angiographic data, women more often had nonobstructive (15% vs 8%) and less often had 2-vessel (25% vs 28%) and 3-vessel (23% vs 26%) coronary disease, regardless of ACS type. After additional adjustment for angiographic disease severity, 30-day mortality among women was not significantly different than men, regardless of ACS type. The relationship between sex and 30-day mortality was similar across the levels of angiographic disease severity (P for interaction = .70).

CONCLUSIONS

Sex-based differences existed in 30-day mortality among patients with ACS and vary depending on clinical presentation. However, these differences appear to be largely explained by clinical differences at presentation and severity of angiographically documented disease.

Enhanced expression of haemoglobin scavenger receptor in accumulated macrophages of culprit lesions in acute coronary syndromes

AIMS

Effective clearance of extracellular haemoglobin (Hb) is thought to limit systemic oxidative heme toxicity, which is presumed to contribute to the pathogenesis of plaque instability. We immunohistochemically examined the relationship between intraplaque haemorrhage, 4-HNE (4-hydroxy-2-nonenal), an index of lipid peroxidation, and the Hb scavenger receptor (CD163), using coronary atherectomy specimens from 74 patients with stable angina pectoris (SAP, n = 39) or unstable angina pectoris (UAP, n = 35).

METHODS AND RESULTS

Atherectomy samples were stained with antibodies against glycophorin A (a protein specific to erythrocyte membranes), CD31, 4-HNE, and CD163. Quantitative analysis demonstrated that glycophorin A-positive areas, 4-HNE-positive macrophage score, and CD163-positive macrophage score in UAP patients were significantly higher (glycophorin A, P < 0.0001; 4-HNE-positive macrophage score, P < 0.0001; CD163-positive macrophage score, P < 0.0005) than in SAP patients. The percentage of the glycophorin A-positive area showed a significant positive correlation with the number of CD31-positive microvessels and the 4-HNE-positive macrophage score (microvessels, R = 0.59, P < 0.0001; 4-HNE, R = 0.59, P < 0.0001). Moreover, the CD163-positive macrophage score was positively correlated with glycophorin A-positive area and the 4-HNE-positive macrophage score (glycophorin A, R = 0.58, P < 0.0001; 4-HNE, R = 0.53, P < 0.0001).

CONCLUSION

These findings suggest a positive association among intraplaque haemorrhage, enhanced expression of Hb scavenger receptor, and lipid peroxidation in human unstable plaques.

Progression in atherosclerosis: histological features and pathophysiology of atherosclerotic lesions

In this article, we present an illustrated and brief review of the literature concerning the histological and pathophysiological features of human atherosclerosis. Although the basic descriptive terms remain unchanged, the classification systems have evolved, and a uniform terminology is essential in clinical and laboratory researches. We discuss the major difficulties in classifying atherosclerotic lesions and give an overview of the most important histological classification systems as provided by the American Heart Association and Virmani et al (Arterioscler Thromb Vasc Biol. 2000;20:1262). Furthermore, we present the most recent literature concerning plaque progression, including enlargement of the lipid core and neovascularization.

Decreased frequency of the 3'UTR T>G single nucleotide polymorphism of thrombospondin-2 gene in sudden death due to plaque erosion

OBJECTIVE

Clinical studies have suggested a potentially "protective" variant of the thrombospondin gene 2 (THBS2, MIM*188061). Autopsy studies investigating the frequency of THBS2 polymorphisms in different coronary substrates have not been done.

METHODS

We evaluated the frequency of the T>G THBS2 (SNP ID G5755e5) polymorphism in 439 cases of sudden unexpected death, including acute thrombosis occurring on plaque erosion (n=60), acute thrombosis occurring on plaque rupture (n=54), severe coronary artery disease without acute thrombus (n=76), and 249 sudden unexpected deaths without significant coronary disease. Allele types were determined by polymerase chain reaction of DNA extracted from autopsy frozen tissues.

RESULTS

In controls, there were 60.2% wild-type, 35.3 % TG, and 4.4% GG phenotypes. The frequency of G allele carriers (TG or GG) was 23.3% in erosions vs. 39.8% in controls (P=.02). There was no difference in controls vs. plaque ruptures (40.7%) or severe CAD without thrombus (38.2%). By multivariate analysis, lack of G allele (wild-type TT genotype) was associated with plaque erosion [odds ratio (OR) 2.2, P=.02], independent of age, gender, and cigarette smoking. When combined with a history of cigarette smoking, the association between TT genotype and plaque erosion was greater (OR 3.5, P < or = .0001).

CONCLUSION

The T>G THBS2 is decreased only in plaque erosion, with no difference in frequency between other coronary disease and controls.

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

Review of cardiovascular risk factors in women

BACKGROUND

Although cardiovascular disease (CVD) is the leading cause of death in women in the United States, a knowledge gap persists regarding the mechanisms and management of CVD in women. Before treatment can be optimized, the role of cardiovascular risk factors must be elucidated.

OBJECTIVE

This review provides an updated assessment of cardiovascular risk factors in women, with a focus on cardiometabolic risk.

METHODS

MEDLINE and Cochrane Library databases, and statistics from the National Health and Nutrition Examination Survey and the American Heart Association, were searched from 1990 to September 2008 using the following terms: cardiovascular risk factors, women, gender, cardiometabolic risk, abdominal obesity, and metabolic syndrome. Publications were classified as English-only original data, reviews, and clinical guidelines. Nonpublished data were excluded. Data were extracted by 2 reviewers independently.

RESULTS

Investigators performing multivariable predictive models have estimated that traditional risk factors account for approximately 70% of the variance in estimating cardiovascular events. However, substantial sex differences exist in the prevalence of traditional risk factors as well as in cardiovascular outcomes. Hypertension is more prevalent in men until the age of 59 years, but then contributes to greater morbidity in older women. Low levels of high-density lipoprotein and elevated triglyceride levels pose more of a threat to women, yet high levels of low-density lipoprotein pose equal risk for women and men. The CVD mortality rate is -3 times greater in people with diabetes than in those without diabetes. Among diabetic individuals, CVD mortality is slightly higher in women compared with men.

CONCLUSIONS

Increased knowledge of gender-specific risks for CVD has led to national campaigns to educate women. In addition to traditional risk factors, cardiometabolic risk is an important consideration in women. Controversy exists regarding the exact definitions and usefulness of the term metabolic syndrome, but it is clear that the presence of certain factors contributes to increased morbidity and mortality in affected individuals. Abdominal obesity links insulin resistance, dyslipidemia, and hypertension through complex endocrine pathways. Current research is identifying gene x gender interactions, and continued research is necessary to explore the relationship of sex steroids and cardiovascular risk in both men and women.

Inflammatory markers: linking unstable plaques to coronary event, an interventional perspective

Abundant data links inflammatory mechanisms to atheromatous plaque destabilization leading to plaque rupture and coronary events. The discovery of inflammatory cells and inflammatory mediators within atherosclerotic plaques prone to rupture led to a series of studies demonstrating an association between various markers of inflammation and future coronary events. Inflammatory markers have also been used in patients undergoing coronary angioplasty in an attempt to predict restenosis and risk for post-procedural coronary events. This review article provides an overview on the potential use of inflammatory markers in the context of coronary interventions.

Plaque characteristics in culprit lesions and inflammatory status in diabetic acute coronary syndrome patients

OBJECTIVES

The aim of this study was to assess the plaque characteristics in culprit lesions in diabetic patients with acute coronary syndrome (ACS).

BACKGROUND

Data of the relationship between diabetes mellitus and plaque characteristics in patients with ACS are lacking.

METHODS

We performed grayscale intravascular ultrasound (IVUS) analysis in 422 ACS patients and virtual histology (VH)-IVUS in 310 ACS patients. By subgroup analysis, 112 patients with acute myocardial infarction (AMI) with plaque ruptures also were evaluated.

RESULTS

In the diabetic subgroup, high-sensitivity C-reactive protein (hs-CRP) was significantly increased (p = 0.008), multivessel disease was more common (65% vs. 29%, p < 0.001), and plaque burden was greater (79.7 +/- 9.8 mm2 vs. 74.2 +/- 8.9 mm2, p < 0.001). In the subgroup analysis of 112 AMI patients with plaque ruptures, the presence of multiple plaque ruptures (60% vs. 29%, p = 0.001) and thrombus (72% vs. 52%, p = 0.032) were more common in diabetic group. Diabetes mellitus was the independent predictor of hs-CRP elevation (odds ratio [OR]: 3.030, 95% confidence interval [CI]: 1.204 to 7.623, p = 0.019), and multiple plaque ruptures (OR: 2.984, 95% CI: 1.311 to 6.792, p = 0.009) by multivariable analysis. In 310 VH-IVUS subsets, the absolute and percent necrotic core volumes were significantly greater (16.9 +/- 15.1 mm3 vs. 11.5 +/- 11.4 mm3, p < 0.001, and 17.3 +/- 9.4% vs. 13.7 +/- 7.5%, p < 0.001, respectively), and the presence of at least one thin-cap fibroatheroma (TCFA) (60% vs. 42%, p = 0.003) and multiple TCFAs (28% vs. 11%, p < 0.001) were more common in the diabetic group. Diabetes mellitus was the only independent predictor of TCFA by multivariable analysis (OR: 2.139, 95% CI: 1.266 to 3.613, p = 0.004).

CONCLUSIONS

Diabetic patients with ACS have more plaques with characteristics of plaque vulnerability, different composition of plaques, and have increased inflammatory status compared with nondiabetic patients with ACS.

Vulnerable atherosclerotic plaque elasticity reconstruction based on a segmentation-driven optimization procedure using strain measurements: theoretical framework

It is now recognized that prediction of the vulnerable coronary plaque rupture requires not only an accurate quantification of fibrous cap thickness and necrotic core morphology but also a precise knowledge of the mechanical properties of plaque components. Indeed, such knowledge would allow a precise evaluation of the peak cap-stress amplitude, which is known to be a good biomechanical predictor of plaque rupture. Several studies have been performed to reconstruct a Young's modulus map from strain elastograms. It seems that the main issue for improving such methods does not rely on the optimization algorithm itself, but rather on preconditioning requiring the best estimation of the plaque components' contours. The present theoretical study was therefore designed to develop: 1) a preconditioning model to extract the plaque morphology in order to initiate the optimization process, and 2) an approach combining a dynamic segmentation method with an optimization procedure to highlight the modulogram of the atherosclerotic plaque. This methodology, based on the continuum mechanics theory prescribing the strain field, was successfully applied to seven intravascular ultrasound coronary lesion morphologies. The reconstructed cap thickness, necrotic core area, calcium area, and the Young's moduli of the calcium, necrotic core, and fibrosis were obtained with mean relative errors of 12%, 4% and 1%, 43%, 32%, and 2%, respectively.

Monocytes and neutrophils expressing myeloperoxidase occur in fibrous caps and thrombi in unstable coronary plaques

Background

Myeloperoxidase (MPO) -containing macrophages and neutrophils have been described at sites of plaque rupture. The presence of these cells in precursor lesions to acute rupture (thin cap atheroma, or vulnerable plaque) and within thrombi adjacent to ruptures has not been described, nor an association with iron-containing macrophages within unstable plaques.

Methods

We studied 61 acute ruptures, 15 organizing ruptures, 31 thin cap fibroatheromas, and 28 fibroatheromas from 72 sudden coronary death victims by immunohistochemical and histochemical techniques. Inflammatory cells were typed with anti-CD68 (macrophages), anti-BP-30 (neutrophil bactericidal glycoprotein), and anti-MPO. Iron was localized by Mallory's Prussian blue stain. In selected plaques alpha smooth muscle actin (DAKO, Carpinteria, CA, clone M0851) was performed.

Results

MPO positive cells were present in 79% of ruptured caps, 28% of thin cap fibroatheroma, and no fibroatheromas; neutrophils were present in 72% of ruptures, 8% of thin cap fibroatheromas, and no fibroatheromas. Iron containing foam cells were present in the caps of 93% of acute ruptures, of 85% of organizing ruptures, 20% of thin cap atheromas, and 10% of fibroatheromas. MPO positive cells were more frequent in occlusive than non-occlusive thrombi adjacent to ruptures (p = .006) and were more numerous in diabetics compared to non-diabetics (p = .002)

Conclusion

Unstable fibrous caps are more likely to contain MPO-positive cells, neutrophils, and iron-containing macrophages than fibrous caps of stable fibroatheromas. MPO-positive cells in thrombi adjacent to disrupted plaques are associated with occlusive thrombi and are more numerous in diabetic patients.

Atherogenesis and atherothrombosis--focus on diabetes mellitus

Diabetes mellitus represents a major cause of cardiovascular morbidity and mortality in developed countries, and atherothrombosis accounts for most deaths among patients with diabetes mellitus. Atherothrombosis is defined as atherosclerotic lesion disruption with superimposed thrombus formation. As a long-term, progressive disease process, atherosclerosis often results in an acute atherothrombotic event through plaque rupture and formation of a platelet-rich thrombus. The principal clinical manifestations of atherothrombosis are sudden cardiac death, myocardial infarction, ischaemic stroke, and peripheral arterial ischaemia comprising both intermittent claudication and critical limb ischaemia. Atherosclerosis is the leading cause of morbidity and mortality in the industrialized world, and diabetes mellitus magnifies the risk of cardiovascular events. In addition to the well-known microvascular complications of diabetes mellitus - such as nephropathy, retinopathy and neuropathy - the risk of macrovascular complications affecting the large conduit arteries markedly increases in patients with diabetes mellitus.

Endothelial cell apoptosis is responsible for the formation of coronary thrombotic atherosclerotic plaques

Ischemic manifestations of atherosclerosis are mainly due to thrombus formation upon superficially eroded (denudation of luminal endothelium) plaques or deeply ruptured (fibrous cap rupture) plaques. Eroded plaques, atherosclerotic plaques without rupture, are found common in young patients of sudden death with coronary thrombosis. Our study aimed to investigate the role of endothelial cell (EC) apoptosis in eroded plaque with thrombosis using an atherosclerotic rabbit model. Atherosclerotic plaques were established by post-balloon-injury high-cholesterol feeding in 33 rabbits. After three-month feeding, a 2-cm segment of plaque-rich abdominal aorta for each animal was clamped in vivo and filled with staurosporine, which induces endothelial apoptosis, or saline for 20 minutes. Three days later, serum lipids and high sensitive C-reactive protein (hs-CRP), a valuable inflammatory parameter, were quantified, and abdominal aorta angiography was conducted. In addition, immunohistochemistry staining was performed for all processed aortae. In the staurosporine-treated aorta, endothelium integrity of plaques was disrupted partially or in large areas, but fibrous cap rupture was not observed, the findings of which were similar to eroded plaques detected in human subjects. As compared to saline controls, staurosporine-treated rabbits showed higher apoptosis scores and thrombotic scores, and more angiographic overt thrombosis and histological thrombosis (P < 0.01, respectively), despite the similar serum levels of lipids and hs-CRP. We further confirmed that apoptosis score was linearly associated with thrombotic score. These results suggest that endothelial apoptosis may be an independent risk factor for thrombosis. In conclusion, the increase in endothelial apoptosis is involved in the formation of thrombotic eroded plaques.

A robust rabbit model of human atherosclerosis and atherothrombosis

Disruption and thrombosis of atherosclerotic plaques cause most acute cardiovascular events, but their systematic study has been hampered by the lack of suitable animal models. To assess the value of a modified rabbit model of atherothrombosis, we performed detailed histology of rabbit aortic plaques. Atherosclerosis was induced with a high cholesterol diet fed 2 weeks prior to and 6 weeks after balloon injury of the aorta, followed by 4 weeks of normal diet. We found six out of eight types of plaques cataloged by the American Heart Association in the rabbit aorta. Vulnerable plaques were defined as those with attached platelet and fibrin-rich thrombi after pharmacological triggering with Russell's viper venom and histamine. Ruptured plaques had, as also described for human plaques: i) marked medial and adventitial changes, including neovascularization and inflammation; ii) cholesterol monohydrate crystals and liquid crystalline cholesterol esters in the intima and the fibrous cap; and iii) inflamed, thin fibrous caps. Increased cholesterol monohydrate area, internal elastic lamina area, positive remodeling, fibrous cap inflammation, adventitia breakdown, and inflammation were independent predictors of plaque disruption. Our findings reveal novel insights into plaque vulnerability and could guide the design of noninvasive imaging approaches for detecting and treating high-risk plaques.

Coronary CT angiography (CCTA) and advances in CT plaque imaging

The goal of this review is to highlight current advances in the non-invasive detection of clinically significant atherosclerotic disease including the so-called vulnerable plaque with computed tomography. Atherosclerotic disease encompasses stages of plaque progression, stabilization, and even regression. Traditionally, the focus of diagnostic imaging has been the detection of lumen-occluding atheroma. However, advances in our understanding of the pathophysiology of atherosclerotic plaque have shown that, in certain stages of plaque progression, plaque is "vulnerable" and able to cause acute coronary syndromes despite "non-significant" vascular occlusion at baseline. This provides a rationale to improve our non-invasive imaging technology. Presented here are improvements in soft-tissue resolution with technical advancements as well as contrast-enhancement and lately even nanotechnology-based technology which are geared to detect the clinically elusive vulnerable plaque and provide an opportunity for preventative therapy.

Impact of plaque characteristics analyzed by intravascular ultrasound on long-term clinical outcomes

Limited data are available on long-term outcomes for vulnerable plaque analyzed by intravascular ultrasound (IVUS). The aim of this study was to investigate long-term clinical outcomes in 183 patients (79 with stable angina pectoris and 104 with acute coronary syndromes) who underwent preintervention 3-vessel IVUS and single-vessel stent implantation. Critical events, defined as any cause of death and acute coronary syndromes during follow-up, were evaluated. Plaque characteristics were analyzed in the target vessel and nontarget vessels. Vulnerable plaques were arbitrarily defined as plaques with rupture, lipid core, dissection, or thrombus. The mean follow-up period was 50 +/- 20 months. Critical events developed in 12 patients (7%; 6 acute coronary syndromes, 6 deaths). The critical event-free rate was not different according to the presence of vulnerable plaques in the target lesion (95% vs 95%, p = 0.86). However, in the nontarget vessels, the long-term critical event-free rate was significantly lower in patients with vulnerable plaques (88% vs 96%, p = 0.04). On multivariate Cox regression analysis, the multiplicity of vulnerable plaques in the nontarget vessels (hazard ratio 2.2, 95% confidence interval 1.4 to 3.4, p = 0.001) was the only independent predictor of long-term critical events. Acute coronary syndromes (odds ratio 5.4, 95% confidence interval 2.1 to 14.3, p = 0.001) and diabetes mellitus (odds ratio 5.2, 95% confidence interval 1.9 to 13.8, p = 0.001) were significantly associated with the multiplicity of vulnerable plaques. In conclusion, the multiplicity of vulnerable plaques in nontarget vessels was the most important predictor of future critical cardiac events in this 3-vessel IVUS study.

The role of optical coherence tomography in vascular medicine

Optical coherence tomography (OCT) is an emerging imaging modality that provides high-resolution, microstructural information on atherosclerotic plaques in biological systems. Intracoronary OCT can identify thin-cap fibroatheroma and other vulnerable plaques that may be responsible for acute coronary events. These characteristics make OCT helpful in guiding coronary management and interventions, including stent apposition and early identification of procedure-related complications. OCT is being assessed for its potential role in carotid plaque characterization and in the diagnosis of peripheral arterial atherosclerosis. Its current use in studying carotid and cerebral vasculature and in the diagnosis of peripheral arterial diseases is limited and ill defined, but it is finding increasing application in these areas. Its performance can be further improved by increasing the signal to noise ratio and by using dynamic focus tracking techniques. It can potentially be used to monitor the progression and regression of atherosclerosis in the coronary, cerebral and peripheral vasculature. New indications for its use in vascular medicine are emerging as its technology continues to improve over time.

Preserved coronary endothelial function by inhibition of delta protein kinase C in a porcine acute myocardial infarction model

BACKGROUND

Previous studies demonstrate impairment of endothelial-dependent vasodilation after ischemia/reperfusion (I/R). Though we have demonstrated that inhibition of delta protein kinase C (delta PKC) at reperfusion reduces myocyte damage and improves cardiac function in a porcine acute myocardial infarction (AMI) model, impact of the selective delta PKC inhibitor on epicardial coronary endothelial function remains unknown.

METHODS

Either delta PKC inhibitor (delta V1-1, n=5) or saline (n=5) was infused into the left anterior descending artery at the last 1 min of the 30-min ischemia by balloon occlusion. In vivo responses to bradykinin (endothelium-dependent vasodilator) or nitroglycerin (endothelium-independent vasodilator) were analyzed at 24 h after I/R using intravascular ultrasound. Vascular responses were calculated as the ratio of vessel area at each time point (30, 60, 90 and 120 s after the infusion), divided by values at baseline (before the infusion).

RESULTS

In control pigs, endothelial-dependent vasodilation following bradykinin infusion in infarct-related epicardial coronary artery was impaired, whereas in delta PKC inhibitor-treated pigs the endothelial-dependent vasodilation was preserved. Nitroglycerin infusion caused similar vasodilatory responses in the both groups.

CONCLUSIONS

This is the first demonstration that a delta PKC inhibitor preserves vasodilator capacity in epicardial coronary arteries in an in vivo porcine AMI model. Because endothelial dysfunction correlates with worse outcome in patients with AMI, this preserved endothelial function in epicardial coronary arteries might result in a better clinical outcome.

Sex-related differences in the associations between hyperleptinemia, insulin resistance and dysfibrinolysis

The adipocyte-derived hormone leptin is associated with insulin resistance and reduced fibrinolytic status--or dysfibrinolysis--in humans. As leptin associates differentially to the development of cardiovascular disease and diabetes in men and women, we hypothesized that leptin and insulin sensitivity are related to dysfibrinolysis in a sex-dependent manner. Thirty-two men and 40 women were recruited from the Monitoring of trends and determinants in Cardiovascular disease (MONICA) population sample, representing the highest and lowest quartiles of fasting insulin levels. Lipids, fibrinolytic status [plasminogen activator inhibitor 1 (PAI-1) activity, tissue plasminogen activator (tPA) mass and activity, and tPA-PAI complex], leptin, testosterone and sex-hormone-binding globulin were measured. Insulin sensitivity was estimated using the euglycaemic clamp technique. Body composition was determined by bioimpedance. Determinants for circulating levels of fibrinolytic factors were explored in a multivariate linear regression analysis. Levels of fibrinolytic variables and estimated insulin sensitivity did not differ between men and women. Leptin was independently associated with reduced fibrinolytic status (high PAI-1 activity, low tPA activity, high tPA mass, and high tPA-PAI complex) in men (P < 0.001-0.002). In women, fat mass and/or insulin sensitivity were related to these factors (P < 0.001-0.03), and leptin only to reduced tPA activity (P = 0.002). Hyperleptinemia, dysfibrinolysis, insulin sensitivity and androgenicity associate differentially in men and women.

Platelet-endothelial interactions in atherothrombotic disease: therapeutic implications

The role of the platelet and the endothelium in the pathogenesis of atherosclerosis and subsequent ischemic events has been the subject of extensive investigation. Arterial sites where endothelial function is severely impaired are often the sites of atheroma development. Lesion evolution impairs endothelial function, leading to a self-perpetuating cycle of growth. During early lesion development, overt thrombotic events are rare. However, rupture of an advanced, necrotic plaque or intimal ulceration triggers arterial thrombosis, at which point the importance of platelet function may be seen clearly. The Antiplatelet Trialists' Collaboration meta-analysis demonstrated the benefit of antiplatelet therapy to patients with atherosclerotic disease. Aspirin is the most widely studied agent and is considered the standard of antiplatelet therapy. Newer agents that intervene at different stages of the platelet activation pathway have been developed. Clopidogrel, a new adenosine diphosphate receptor antagonist, is more effective than aspirin in reducing vascular events in patients with prior myocardial infarction, stroke, or established peripheral arterial disease. The glycoprotein IIb-IIIa antagonists such as abciximab have proven effective in the setting of active arterial thrombosis and percutaneous revascularization, but their value in secondary prevention remains unknown. All patients with atherosclerosis should be treated with an antiplatelet drug. Current evidence suggests that either aspirin or clopidogrel are appropriate first-line agents. There is urgent need for an analysis of the risk/benefit ratio in various populations and clinical settings to determine the most appropriate type and intensity of therapy for a given patient.

Molecular imaging of matrix metalloproteinase in atherosclerotic lesions: resolution with dietary modification and statin therapy

OBJECTIVES

This study sought to evaluate the feasibility of noninvasive detection of matrix metalloproteinase (MMP) activity in experimental atherosclerosis using technetium-99m-labeled broad matrix metalloproteinase inhibitor (MPI) and to determine the effect of dietary modification and statin treatment on MMP activity.

BACKGROUND

The MMP activity in atherosclerotic lesions contributes to the vulnerability of atherosclerotic plaques to rupture.

METHODS

Atherosclerosis was produced in 34 New Zealand White rabbits by balloon de-endotheliazation of the abdominal aorta and a high-cholesterol diet. In addition, 12 unmanipulated rabbits were used as controls and 3 for blood clearance characteristics. In vivo micro-single-photon emission computed tomography (SPECT) imaging was performed after radiolabeled MPI administration. Subsequently, aortas were explanted to quantitatively measure percent injected dose per gram (%ID/g) MPI uptake. Histological and immunohistochemical characterization was performed and the extent of MMP activity was determined by gel zymography or enzyme-linked immunosorbent assays.

RESULTS

The MPI uptake in atherosclerotic lesions (n = 18) was clearly visualized by micro-SPECT imaging; MPI uptake was markedly reduced by administration of unlabeled MPI before the radiotracer (n = 4). The MPI uptake was also significantly reduced after diet withdrawal (n = 6) and fluvastatin treatment (n = 6); no uptake was observed in normal control rabbits (n = 12). The %ID/g MPI uptake (0.10 +/- 0.03%) in the atherosclerotic lesions was significantly higher than the uptake in control aorta (0.016 +/- 0.004%, p < 0.0001). Uptake in fluvastatin (0.056 +/- 0.011%, p < 0.0005) and diet withdrawal groups (0.043 +/- 0.011%, p < 0.0001) was lower than the untreated group. The MPI uptake correlated with immunohistochemically verified macrophage infiltration (r = 0.643, p < 0.0001), and MMP-2 (r = 0.542, p < 0.0001) or MMP-9 (r = 0.578, p < 0.0001) expression in plaques.

CONCLUSIONS

The present data show the feasibility of noninvasive detection of MMP activity in atherosclerotic plaques, and confirm that dietary modification and statin therapy reduce MMP activity.

Non-invasive assessment of vulnerable plaque

BACKGROUND

Sudden cardiac death or unheralded acute coronary syndromes are common initial manifestations of coronary atherosclerosis and most such events occur at sites of non-flow limiting coronary atherosclerosis.

OBJECTIVE

Non-invasive detection of high-risk plaques might provide a means to improve risk stratification in primary and secondary prevention settings.

METHODS

This review is focused on the potential of multidetector computed tomography coronary angiography (MDCT-CA) to provide the opportunity to identify different aspects of plaque vulnerability throughout the coronary tree in an accurate, fast, safe and non-invasive manner.

CONCLUSION

Coronary artery calcium scoring, on top of established risk stratification, could potentially be a cost-effective strategy for primary prevention. MDCT-CA allows a non-invasive evaluation of several features commonly seen in vulnerable plaques and has demonstrated an independent prognostic value on a patient basis. The value of the technique itself might result, potentially, in a better estimation of the relative risk of an invidual plaque to rupture.

Inflammation and plaque vulnerability

Development of a thrombus at the site of an atherosclerotic plaque initiates abrupt arterial occlusion and is the proximate event responsible for the vast majority of acute ischemic syndromes. In nearly 75% of cases thrombus overlies a disrupted or ruptured plaque whereas the remainder of the thrombi overly an intact plaque with superficial endothelial erosion. Over the past several years, it has been recognized that plaque composition rather than plaque size or stenosis severity is important for plaque rupture and subsequent thrombosis. Ruptured plaques, and by inference, plaques prone to rupture, tend to be large in size with associated expansive arterial remodeling, thin fibrous cap with a thick or large necrotic lipid core with immuno-inflammatory cell infiltration in fibrous cap and adventitia and increased plaque neovascularity and intraplaque hemorrhage. The size of the necrotic lipid core and extent and location of plaque inflammation appear to be key factors in determining plaque instability. Inflammation and immune cell activation appears to play a key role in the loss of collagen in the fibrous cap, a prelude to fibrous cap rupture, through release of collagen degrading enzymes. Furthermore, inflammation may also play a key role in the death of collagen synthesizing smooth muscle cells which further contributes to loss of fibrous cap integrity. Inflammation also is likely a key player in the ensuing thrombosis that follows plaque disruption through the elaboration of the pro-coagulant protein, tissue factor. An improved understanding of the pathophysiology of plaque vulnerability and subsequent athero-thrombosis should provide novel insights into improved prevention of athero-thrombotic cardiovascular events.

Endothelial dysfunction: from molecular mechanisms to measurement, clinical implications, and therapeutic opportunities

Endothelial dysfunction has been implicated as a key factor in the development of a wide range of cardiovascular diseases, but its definition and mechanisms vary greatly between different disease processes. This review combines evidence from cell-culture experiments, in vitro and in vivo animal models, and clinical studies to identify the variety of mechanisms involved in endothelial dysfunction in its broadest sense. Several prominent disease states, including hypertension, heart failure, and atherosclerosis, are used to illustrate the different manifestations of endothelial dysfunction and to establish its clinical implications in the context of the range of mechanisms involved in its development. The size of the literature relating to this subject precludes a comprehensive survey; this review aims to cover the key elements of endothelial dysfunction in cardiovascular disease and to highlight the importance of the process across many different conditions.

Heart and vessel pathology underlying brain infarction in 142 stroke patients

OBJECTIVE

This study was designed to determine the histopathological characteristics of cardiac and vascular lesions responsible for various subtypes of ischemic stroke.

METHODS

Postmortem pathological examination was performed on 142 patients who died within 30 days of the onset of ischemic stroke in the National Cardiovascular Center, Osaka, Japan.

RESULTS

The numbers of cases with autopsy-proven diagnoses of atherothrombotic, cardioembolic, and lacunar strokes, ischemic stroke of other determined causes, and ischemic stroke of undetermined cause were 17, 107, 2, 12, and 4, respectively. Thrombi that developed at the culprit plaques of the cerebral arteries were responsible for atherothrombotic stroke. In 70% of the cases with cardioembolic stroke, the presence of thrombi as potential embolic sources were confirmed in the heart or, in some cases, in the venous circulation of patients with patent foramen ovale and tetralogy of Fallot.

INTERPRETATION

In most atherothrombotic strokes, fibrin- and platelet-rich thrombi of various thicknesses develop at the culprit plaques of the cerebral arteries, which are finally occluded with fibrin- and red-cell-rich thrombi (red thrombi). In most cardioembolic strokes, red thrombi generated in the heart or peripheral veins are dislodged to embolize the cerebral arteries.

Serotonin induces vasoconstriction of smooth muscle cell-rich neointima through 5-hydroxytryptamine2A receptor in rabbit femoral arteries

BACKGROUND

Smooth muscle cell (SMC)-rich intima is a morphological feature of atherosclerotic lesions that is observed in eroded plaque and spastic arteries. Arteries with SMC-rich intima are susceptible to vasoconstriction or vasospasm against some vasoactive agents.

OBJECTIVE

The present study evaluates the contribution of SMC-rich intima to thrombogenic vasoconstriction.

METHODS

We established SMC-rich neointima by damaging rabbit femoral arteries using balloons and then measured the isometric tension of the femoral strips against 5-hydroxytryptamine (5-HT), adenosine diphosphate, adenosine triphosphate and thrombin.

RESULTS

Among these agents, only 5-HT induced a hypercontractile response of the injured arteries with SMC-rich neointima, compared with non-injured arteries. Smooth muscle cells of both the neointima and media expressed 5-HT(2A) receptor, and sarpogrelate, a selective 5-HT(2A) receptor antagonist significantly inhibited the hypercontraction. Furthermore, 5-HT induced contraction of separated neointima and hypercontraction of separated media compared with non-injured media. Sarpogrelate and fasudil, a specific Rho-kinase inhibitor, significantly suppressed such contraction of both the neointima and media of injured arteries.

CONCLUSIONS

These results suggest that 5-HT plays a crucial role in thrombogenic vasoconstriction, and that SMC-rich intima as well as media directly contributes to the hypercontractile response of atherosclerotic vessels through the 5-HT(2A) receptor and the Rho-kinase pathway.

Radionuclide imaging: a molecular key to the atherosclerotic plaque

Despite primary and secondary prevention, serious cardiovascular events such as unstable angina or myocardial infarction still account for one-third of all deaths worldwide. Therefore, identifying individual patients with vulnerable plaques at high risk for plaque rupture is a central challenge in cardiovascular 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, molecular imaging techniques use radiolabeled molecules to detect functional aspects in atherosclerotic plaques by visualizing their biological activity. Based upon the knowledge about the pathophysiology of atherosclerosis, various studies in vitro and in vivo and the 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. This review gives an update on the relevant noninvasive plaque imaging approaches using nuclear imaging techniques to detect atherosclerotic vascular lesions.

Necrotic core thickness and positive arterial remodeling index: emergent biomechanical factors for evaluating the risk of plaque rupture

Fibrous cap thickness is often considered as diagnostic of the degree of plaque instability. Necrotic core area (Core(area)) and the arterial remodeling index (Remod(index)), on the other hand, are difficult to use as clinical morphological indexes: literature data show a wide dispersion of Core(area) thresholds above which plaque becomes unstable. Although histopathology shows a strong correlation between Core(area) and Remod(index), it remains unclear how these interact and affect peak cap stress (Cap(stress)), a known predictor of rupture. The aim of this study was to investigate the change in plaque vulnerability as a function of necrotic core size and plaque morphology. Cap(stress) value was calculated on 5,500 idealized atherosclerotic vessel models that had the original feature of mimicking the positive arterial remodeling process described by Glagov. Twenty-four nonruptured plaques acquired by intravascular ultrasound on patients were used to test the performance of the associated idealized morphological models. Taking advantage of the extensive simulations, we investigated the effects of anatomical plaque features on Cap(stress). It was found that: 1) at the early stages of positive remodeling, lesions were more prone to rupture, which could explain the progression and growth of clinically silent plaques and 2) in addition to cap thickness, necrotic core thickness, rather than area, was critical in determining plaque stability. This study demonstrates that plaque instability is to be viewed not as a consequence of fibrous cap thickness alone but rather as a combination of cap thickness, necrotic core thickness, and the arterial remodeling index.

Identifying the susceptibility genes for coronary artery disease: from hyperbole through doubt to cautious optimism

The genetic basis of coronary artery disease (CAD) is complex, and the fact that an alarmingly high proportion of reported associations between genetic variants and CAD are not replicated has generated uncertainty as to whether molecular genetics is ever going to deliver on the promises delivered in the late 1990s. However, during 2007, the first generation of large-scale genome-wide association studies using high-density, single nucleotide polymorphism genotyping arrays have revealed genetic variants that are robustly associated with CAD and CAD-related traits such as type 2 diabetes and obesity. In particular, a robust susceptibility locus for CAD has been identified on chromosome 9p21. Also, evidence has been obtained that multiple rare alleles with fairly strong phenotypic effects may contribute to the genetic heritability of CAD, in addition to common variants with a modest impact on risk. Furthermore, new mechanistic connections have been discovered between different common complex diseases including CAD. This review focuses on the challenges and recent advances of molecular genetics in dissecting the molecular pathophysiology of atherothrombosis and defining novel targets for treatment.

Prognostic role of flow-mediated dilation and cardiac risk factors in post-menopausal women

OBJECTIVES

The aim of this study was to examine the association between brachial artery flow-mediated dilation (FMD) and cardiovascular events in a cohort of initially asymptomatic post-menopausal women, with adjustment for the presence of the major cardiovascular risk factors.

BACKGROUND

Conventional major cardiovascular risk factors (cigarette smoking, hypercholesterolemia, hypertension, and diabetes) fail to explain nearly 50% of cardiovascular events. Defining the magnitude of future risk for the development of clinical events is a major focus of effective primary prevention. Evaluation of endothelial function, utilizing the noninvasive measurement of the brachial artery FMD, may serve as a screening tool to individualize high-risk patients.

METHODS

We conducted a prospective study on 2,264 post-menopausal women, age 54 +/- 6 years. The length of the follow-up was 45 +/- 13 months (range 6 to 65 months).

RESULTS

During observation, 90 major events were recorded. Risk-adjusted relative risk values resulted 1.0, 1.33 (95% confidence interval [CI] 1.09 to 4.09), and 4.42 (95% CI 2.97 to 8.01) for women in the higher, intermediate, and lower tertile of FMD, respectively (p < 0.0001 for trend). The event rate for women in the lower tertile (FMD <or=4.5%) was greater than the combined event rate noted in the other 2 tertiles (women in the lower tertile accounted for 51 events [56.6% of total events]). When added to age and other conventional cardiovascular risk factors (smoking habits, presence of hypercholesterolemia, history of diabetes, hypertension), FMD contributed significantly to the model predicting cardiovascular events (likelihood ratio chi-square change: 10.22; p < 0.0001).

CONCLUSIONS

In post-menopausal women, the knowledge of FMD provided incremental prognostic information regarding the risk of developing cardiovascular events.

Treatment of a large left main coronary artery thrombus by aspiration thrombectomy

A left main coronary artery thrombosis is a life-threatening condition demanding immediate therapeutic management. Traditional treatment options include thrombolysis, percutaneous coronary intervention (PCI) with stenting or cardiac bypass surgery. The number of reported cases in which aspiration thrombectomy has been used is limited. Indications for this therapeutic approach are determined by coronary anatomy, clinical stability, and hemodynamic condition of the patient. We present the case of an acute left main coronary artery thrombosis leading to progressive deterioration of left ventricle function that was successfully treated with aspiration thrombectomy.

Diagnosis and treatment of coronary vulnerable plaques

Thin-capped fibroatheroma is the morphology that most resembles plaque rupture. Detection of these vulnerable plaques in vivo is essential to being able to study their natural history and evaluate potential treatment modalities and, therefore, may ultimately have an important impact on the prevention of acute myocardial infarction and death. Currently, conventional grayscale intravascular ultrasound, virtual histology and palpography data are being collected with the same catheter during the same pullback. A combination of this catheter with either thermography capability or additional imaging, such as optical coherence tomography or spectroscopy, would be an exciting development. Intravascular magnetic resonance imaging also holds much promise. To date, none of the techniques described above have been sufficiently validated and, most importantly, their predictive value for adverse cardiac events remains elusive. Very rigorous and well-designed studies are compelling for defining the role of each diagnostic modality. Until we are able to detect in vivo vulnerable plaques accurately, no specific treatment is warranted.

Atherosclerosis and thrombosis: identification of targets for magnetic resonance imaging

Imaging techniques are needed that will allow earlier and more refined diagnosis, guide targeted treatment in individual patients and monitor response to that treatment. Magnetic resonance imaging is well-suited to these tasks as it can provide anatomical, structural, and functional data on the arterial wall. Its capabilities are further enhanced by the use of a range of increasingly sophisticated contrast agents that target specific molecules, cells, and biological processes. This article will consider the pathogenesis of atherosclerosis and systematically identify biologically relevant targets for imaging at different stages of disease process.

In vivo comparison of optical coherence tomography and angioscopy for the evaluation of coronary plaque characteristics

Atherosclerotic yellow plaques identified by coronary angioscopy are considered as vulnerable plaques. However, characteristics of yellow plaques are not well understood. Optical coherence tomography (OCT) provides accurate tissue characterization in vivo and has the capability to measure fibrous cap thickness covering a lipid plaque. Characteristics of yellow plaques identified by angioscopy were evaluated by OCT. We examined 205 plaques of 41 coronary arteries in 26 patients. In OCT analysis, plaques were classified as fibrous or lipid. Minimal lumen area of the plaque, arch of the lipid, and fibrous cap thickness on the lipid plaque were measured. Yellow grade of the plaque was defined as 0 (white), 1 (light yellow), 2 (medium yellow), or 3 (dark yellow) based on the angioscopy. A total of 149 plaques were diagnosed as lipid plaques. Neither the minimal lumen area nor the arch of the lipid was related to the yellow grade. There was an inverse relationship between color grade and the fibrous cap thickness (grade 0 [n = 45] 218 +/- 89 microm, grade 1 [n = 40] 101 +/- 8 microm, grade 2 [n = 46] 72 +/- 10 microm, and grade 3 [n = 18] 40 +/- 14 microm; p <0.05). Sensitivity and specificity of the angioscopy-identified yellow plaque for having a thin fibrous cap (thickness Collapse

Key Words Collapse

MESH Headings

• Acute Coronary Syndrome/pathology
• Angioscopy
• Coronary Artery Disease/pathology
• Coronary Thrombosis/pathology
• Coronary Vessels/pathology
• Female
• Fibrosis
• Humans
• Lipid Metabolism
• Male
• Middle Aged
• Sensitivity and Specificity
• Tomography, Optical Coherence

Collapse

Grants Collapse

Affiliation(s)

Masamichi Takano Department of Internal Medicine, Chiba-Hokusoh Hospital, Nippon Medical School, Chiba, Japan.
Ik-Kyung Jang
Shigenobu Inami
Masanori Yamamoto
Daisuke Murakami
Kentaro Okamatsu
Koji Seimiya
Takayoshi Ohba
Kyoichi Mizuno

Collapse

Collaborators Collapse

Comparison of clinical characteristics and arterial remodeling by intravascular ultrasonic imaging in three age groups (< or =55, 56 to 69 and > or =70 years) of Japanese patients with acute myocardial infarction

Recent epidemiologic, pathologic, and intravascular ultrasound (IVUS) studies have shown that there are differences in coronary risk factors or plaque morphology between younger and older patients with acute myocardial infarctions (AMIs). This study examined clinical background and plaque morphology using IVUS in younger and older adults with AMIs in Japan. The study population consisted of 96 patients with AMIs, for whom preinterventional IVUS images were obtained. Patients were classified into 3 groups: a young group (aged < or =55 years), a middle-aged group (aged 56 to 69 years), and an old group (aged > or =70 years). The remodeling index was defined as the ratio of the external elastic membrane area at the culprit lesion to the external elastic membrane area at the proximal reference site. Expansive remodeling was defined as a remodeling index >1.05 and constrictive remodeling as a remodeling index <0.95. The frequency of hypercholesterolemia was significantly different among the 3 age groups. Total cholesterol (p <0.001), low-density lipoprotein cholesterol (p <0.005), and triglyceride (p <0.05) levels and body mass index (p <0.001) in the young group were significantly higher than in the old group. On IVUS images, constrictive remodeling was most common in the young group, whereas expansive remodeling occurred most commonly in the middle-aged and old groups. In conclusion, this study demonstrated that patients with AMIs in the young group had higher levels of hypercholesterolemia, obesity, and constrictive remodeling compared with those in the old group. The differences in arterial remodeling of the culprit lesions between younger and older patients with AMIs may reflect different biologic mechanisms of plaque activation and destabilization.

Innate immunity, macrophage activation, and atherosclerosis

Inflammation underpins the development of atherosclerosis. Initiation and progression of vascular inflammation involves a complex cellular network, with macrophages as major contributors. Activated macrophages produce proinflammatory mediators, bridge innate and adaptive immunity, regulate lipid retention, and participate directly in vascular repair and remodeling. Recent efforts to elucidate molecular mechanisms involved in the regulation of vascular inflammation in atherosclerosis have implicated several families of innate immune recognition receptors in inflammatory activation during the course of this disease. This article reviews our current understanding of innate immune recognition receptors, signaling pathways, and putative ligands implicated in activation of macrophages in the disease. In its final section, we propose a model for the role of macrophages in bridging inflammation and atherosclerosis from the perspective of innate immune recognition and activation.