Elucidation of the role of plaque instability and rupture in acute coronary events

Detection of Vulnerable Coronary Plaques Using Invasive and Non-Invasive Imaging Modalities

Acute coronary syndrome (ACS) mostly arises from so-called vulnerable coronary plaques, particularly prone for rupture. Vulnerable plaques comprise a specific type of plaque, called the thin-cap fibroatheroma (TFCA). A TCFA is characterized by a large lipid-rich necrotic core, a thin fibrous cap, inflammation, neovascularization, intraplaque hemorrhage, microcalcifications or spotty calcifications, and positive remodeling. Vulnerable plaques are often not visible during coronary angiography. However, different plaque features can be visualized with the use of intracoronary imaging techniques, such as intravascular ultrasound (IVUS), potentially with the addition of near-infrared spectroscopy (NIRS), or optical coherence tomography (OCT). Non-invasive imaging techniques, such as computed tomography coronary angiography (CTCA), cardiovascular magnetic resonance (CMR) imaging, and nuclear imaging, can be used as an alternative for these invasive imaging techniques. These invasive and non-invasive imaging modalities can be implemented for screening to guide primary or secondary prevention therapies, leading to a more patient-tailored diagnostic and treatment strategy. Systemic pharmaceutical treatment with lipid-lowering or anti-inflammatory medication leads to plaque stabilization and reduction of cardiovascular events. Additionally, ongoing studies are investigating whether modification of vulnerable plaque features with local invasive treatment options leads to plaque stabilization and subsequent cardiovascular risk reduction.

Clinical significance of healed plaque detected by optical coherence tomography: a 2-year follow-up study

Recent studies have shown that healed plaque at the culprit lesion detected by optical coherence tomography (OCT) is a sign of pan-vascular vulnerability and advanced atherosclerosis. However, the clinical significance of healed plaque is unknown. A total of 265 patients who had OCT imaging of a culprit vessel and 2-year clinical follow-up data were included. Patients were stratified based on the presence or absence of a layered plaque phenotype, defined as layers of different optical density by OCT at either culprit or non-culprit lesions. The association between layered plaque and major adverse cardiac events (MACE), defined as cardiac death, acute coronary syndromes (ACS), or revascularization, was studied. Among 265 patients, 96 (36.2%) had the layered plaque phenotype. Layered plaque was more frequently observed in stable angina pectoris patients than in ACS patients (57.8%vs. 25.1%, p < 0.001). The average clinical follow-up period was 672 ± 172 days. Cumulative MACE was significantly higher in patients with layered plaque (p = 0.041), which was primarily driven by the high revascularization rate at 2 years (p = 0.002). Multivariate regression analysis showed that presence of layered plaque and low-density lipoprotein cholesterol levels were independently associated with an increased risk of revascularization (p = 0.026, p = 0.008, respectively). Patients with healed plaque in the culprit vessel had a higher incidence of revascularization, as compared to those without healed plaque, at 2 years.

Vulnerable atherosclerotic plaque features: findings from coronary imaging

Pathological studies have suggested that features of vulnerable atherosclerotic plaques likely to progress and lead to acute cardiovascular events have specific characteristics. Given the progress of intravascular coronary imaging technology, some large prospective studies have detected features of vulnerable atherosclerotic plaques using these imaging modalities. However, the rate of cardiovascular events, such as acute coronary syndrome, has been found to be considerably reduced in the limited follow-up period available in the statin era. Additionally, not all disrupted plaques lead to thrombus formation with clinical presentation. If sub-occlusive or occlusive thrombus formation does not occur, a thrombus on a disrupted plaque will organize without any symptoms, forming a “healed plaque”. Although vulnerable plaque detection using intracoronary imaging is focused on “thin-cap fibroatheroma” leading to plaque rupture, superficial plaque erosion is increasingly recognized; however, the underlying mechanism of thrombus formation on eroded plaques is not well understood. One of intravascular imaging, optical coherence tomography (OCT) has the highest image resolution and has enabled detailed characterization of the plaque in vivo. Here, we reviewed the status and limitations of intravascular imaging in terms of detecting vulnerable plaque through mainly OCT studies. We suggested that vulnerable plaque should be reconsidered in terms of eroded plaque and healed plaque and that both plaque and circulating blood should be assessed in greater detail accordingly.

Inverse J-shaped relation between coronary arterial calcium density and mortality in advanced chronic kidney disease

BACKGROUND

The coronary artery calcium (CAC) score from cardiac computed tomography (CT) is a composite of CAC volume and CAC density. In the general population, CAC volume is positively and CAC density inversely associated with cardiovascular disease (CVD) events, implying that decreased CAC density reflects atherosclerotic plaque instability. We analysed associations of CAC indices with mortality risk in patients with end-stage renal disease [chronic kidney disease Stage 5 (CKD5)].

METHODS

In 296 CKD5 patients undergoing cardiac CT (median age 55 years, 67% male, 19% diabetes, 133 dialysed), the Framingham risk score (FRS), presence of CVD and protein-energy wasting (PEW; subjective global assessment) and high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) were determined at baseline. During follow-up for a median of 35 months, 51 patients died and 75 patients underwent renal transplantation. All-cause mortality risk was analysed with competing-risk regression models. Vascular calcification was analysed in biopsies of the arteria epigastrica inferior in 111 patients.

RESULTS

Patients in the middle tertile of CAC density had the highest CAC score, CAC volume, age, CVD, PEW, FRS, hsCRP and IL-6. In competing risk analysis, the middle {subhazard ratio [sHR] 10.7 [95% confidence interval (CI) 2.0-57.3]} and high [sHR 8.9 (95% CI 1.5-51.8)] tertiles of CAC density associated with increased mortality, independent of CAC volume. The high tertile of CAC volume, independent of CAC density, associated with increased mortality [sHR 8.9 (95% CI 1.5-51.8)]. Arterial media calcification was prominent and associated with CAC volume and CAC density.

CONCLUSIONS

In CKD5, mortality increased linearly with higher CAC score and CAC volume whereas for CAC density an inverse J-shaped pattern was observed, with the crude mortality rate being highest for the middle tertile of CAC density. CAC volume and CAC density were associated with the extent of arterial media calcification.

Exploring the relationship between biomechanical stresses and coronary atherosclerosis

The pathophysiology of coronary atherosclerosis is multifaceted. Plaque initiation and progression are governed by a complex interplay between genetic and environmental factors acting through processes such as lipid accumulation, altered haemodynamics and inflammation. There is increasing recognition that biomechanical stresses play an important role in atherogenesis, and integration of these metrics with clinical imaging has potential to significantly improve cardiovascular risk prediction. In this review, we present the calculation of coronary biomechanical stresses from first principles and computational methods, including endothelial shear stress (ESS), plaque structural stress (PSS) and axial plaque stress (APS). We discuss the current experimental and human data linking these stresses to the natural history of coronary artery disease and explore the future potential for refining treatment options and predicting future ischaemic events.

Microfluidic assay of circulating endothelial cells in coronary artery disease patients with angina pectoris

Background

Circulating endothelial cells (CECs) are widely reported as a promising biomarker of endothelial damage/dysfunction in coronary artery disease (CAD). The two popular methods of CEC quantification include the use of immunomagnetic beads separation (IB) and flow cytometry analysis (FC); however, they suffer from two main shortcomings that affect their diagnostic and prognostic responses: non-specific bindings of magnetic beads to non-target cells and a high degree of variability in rare cell identification, respectively. We designed a microfluidic chip with spatially staggered micropillars for the efficient harvesting of CECs with intact cellular morphology in an attempt to revisit the diagnostic goal of CEC counts in CAD patients with angina pectoris.

Methods

A label-free microfluidic assay that involved an in-situ enumeration and immunofluorescent identification (DAPI⁺/CD146⁺/VEGFR1⁺/CD45^-) of CECs was carried out to assess the CEC count in human peripheral blood samples. A total of 55 CAD patients with angina pectoris [16 with chronic stable angina (CSA) and 39 with unstable angina (UA)], together with 15 heathy controls (HCs) were enrolled in the study.

Results

CEC counts are significantly higher in both CSA and UA groups compared to the HC group [respective medians of 6.9, 10.0 and 1.5 cells/ml (p < 0.01)]. Further, a significant elevation of CEC count was observed in the three UA subgroups [low risk (5.3) vs. intermediate risk (10.8) vs. high risk (18.0) cells/ml, p < 0.001) classified in accordance to the TIMI NSTEMI/UA risk score system. From the receiver-operating characteristic curve analysis, the AUCs for distinguishing CSA and UA from HC were 0.867 and 0.938, respectively. The corresponding sensitivities were 87.5% and 84.6% and the specificities were 66.7% and 86.7%, respectively.

Conclusions

Our microfluidic assay system is efficient and stable for CEC capture and enumeration. The results showed that the CEC count has the potential to be a promising clinical biomarker for the assessment of endothelial damage/dysfunction in CAD patients with angina pectoris.

pNaKtide Attenuates Steatohepatitis and Atherosclerosis by Blocking Na/K-ATPase/ROS Amplification in C57Bl6 and ApoE Knockout Mice Fed a Western Diet

We have previously reported that the α1 subunit of sodium potassium adenosine triphosphatase (Na/K-ATPase), acts as a receptor and an amplifier for reactive oxygen species, in addition to its distinct pumping function. On this background, we speculated that blockade of Na/K-ATPase-induced ROS amplification with a specific peptide, pNaKtide, might attenuate the development of steatohepatitis. To test this hypothesis, pNaKtide was administered to a murine model of NASH: the C57Bl6 mouse fed a “western” diet containing high amounts of fat and fructose. The administration of pNaKtide reduced obesity as well as hepatic steatosis, inflammation and fibrosis. Of interest, we also noted marked improvement in mitochondrial fatty acid oxidation, insulin sensitivity, dyslipidemia and aortic streaking in this mouse model. To further elucidate the effects of pNaKtide on atherosclerosis, similar studies were performed in ApoE knockout mice also exposed to the western diet. In these mice, pNaKtide not only improved steatohepatitis, dyslipidemia, and insulin sensitivity, but also ameliorated significant aortic atherosclerosis. Collectively, this study demonstrates that the Na/K-ATPase/ROS amplification loop contributes significantly to the development and progression of steatohepatitis and atherosclerosis. And furthermore, this study presents a potential treatment, the pNaKtide, for the metabolic syndrome phenotype.

The vulnerable plaque: current concepts and future perspectives on coronary morphology, composition and wall stress imaging

Cardiovascular imaging plays an important role in the identification and characterization of the vulnerable plaque. A major goal is the ability to identify individuals at risk of plaque rupture and developing an acute coronary syndrome. Early recognition of rupture-prone atherosclerotic plaques may lead to the development of pharmacologic and interventional strategies to reduce acute coronary events. We review state-of-the-art cardiovascular imaging for identification of the vulnerable plaque. There is ample evidence of a close relationship between plaque morphology and patient outcome, but molecular imaging can add significant information on tissue characterization, inflammation and subclinical thrombosis. Additionally, identifying arterial wall exposed to high shear stress may further identify rupture-prone arterial segments. These new modalities may help reduce the individual, social and economic burden of cardiovascular disease.

Presentation, management, and outcomes of ischaemic heart disease in women

Scientific interest in ischaemic heart disease (IHD) in women has grown considerably over the past 2 decades. A substantial amount of the literature on this subject is centred on sex differences in clinical aspects of IHD. Many reports have documented sex-related differences in presentation, risk profiles, and outcomes among patients with IHD, particularly acute myocardial infarction. Such differences have often been attributed to inequalities between men and women in the referral and treatment of IHD, but data are insufficient to support this assessment. The determinants of sex differences in presentation are unclear, and few clues are available as to why young, premenopausal women paradoxically have a greater incidence of adverse outcomes after acute myocardial infarction than men, despite having less-severe coronary artery disease. Although differential treatment on the basis of patient sex continues to be described, the extent to which such inequalities persist and whether they reflect true disparity is unclear. Additionally, much uncertainty surrounds possible sex-related differences in response to cardiovascular therapies, partly because of a persistent lack of female-specific data from cardiovascular clinical trials. In this Review, we assess the evidence for sex-related differences in the clinical presentation, treatment, and outcome of IHD, and identify gaps in the literature that need to be addressed in future research efforts.

The utilization of carotid artery imaging beyond metabolic scores and high-sensitivity CRP in screening intermediate-to-high Framingham risk of asymptomatic Taiwanese population

To compare the diagnostic accuracy of various cardiovascular screening tools in asymptomatic subjects with intermediate-to-high risk Framingham risk score (FRS). In addition, we also investigated whether carotid artery study could further add incremental value beyond metabolic abnormality and inflammatory marker in this issue. 1,200 asymptomatic subjects who underwent health evaluation were recruited in our study. FRS was calculated in all participants based on clinical variables, body surface electrocardiography, medical histories, and life styles. Metabolic scores, serum high-sensitivity C reactive protein (hs-CRP) level and carotid artery study in assessing intima-media-thickness (CIMT) and plaque were all obtained and compared to FRS. Comparison of diagnostic accuracy was then conducted among these different tools aiming at a more efficient screen in identifying intermediate-to-high FRS. Of all, 1,101 participants (mean age 50.6 ± 10.4, 38.6 % women) were finally entered in our study after exclusion of known cardiovascular diseases. By utilizing common carotid IMT (CCIMT) equal or larger than 1 mm, best specificity (98.27, 95 % CI 97.24-98.99) was achieved in identifying intermediate-to-high FRS subject. The most optimal cut-off in identifying intermediate-to-high FRS for metabolic scores, hs-CRP and CCIMT was 2, 0.101 mg/dL and 0.65 mm, respectively. Both receiver operating characteristic curve and likelihood ratio tests showed that information provided by carotid artery study further showed significant incremental value when superimposed on metabolic scores and hs-CRP (all p < 0.05) in screening intermediate-to-high FRS subjects. Though diagnostic accuracy may differ to some degree by using different cut-off values, a low metabolic score seemed to have the best sensitivity with abnormal CCIMT yielded highest specificity in screening a subject with future cardiovascular risks. Carotid artery study added significant clinical incremental value in discriminating projected risk beyond metabolic scores and hs-CRP.

In vivo critical fibrous cap thickness for rupture-prone coronary plaques assessed by optical coherence tomography

AIMS

The widely accepted threshold of <65 μm for coronary plaque fibrous cap thickness was derived from postmortem studies of ruptured plaques and may not be appropriate for in vivo rupture-prone plaques. We investigated the relationship between fibrous cap thickness and plaque rupture using optical coherence tomography (OCT).

METHODS AND RESULTS

We studied 266 lesions (103 from patients with acute coronary syndrome and 163 from patients with stable angina) before percutaneous coronary intervention using OCT. Ruptured and non-ruptured lipid-rich plaques were identified and the thinnest and most representative fibrous cap thickness were determined. Cap thickness was reliably measured in 71 ruptured and 111 non-ruptured plaques. From the ruptured plaques, the median thinnest cap thickness was 54 μm (50-60). The median most representative cap thickness was 116 μm (103-136). For non-ruptured plaques, the median thinnest cap thickness was 80 μm (67-104) and 182 μm (156-216) for most representative cap thickness. In 95% of ruptured plaques, the thinnest cap thickness and most representative cap thickness were <80 and <188 μm, respectively. The best cut-offs for predicting rupture were <67 μm (OR: 16.1, CI: 7.5-34.4, P < 0.001) for the thinnest cap thickness and <151 μm (OR: 35.6, CI: 15.0-84.3, P < 0.001) for most representative cap thickness. These two measures were modestly correlated (r(2) = 0.39) and both independently associated with rupture.

CONCLUSION

In vivo critical cap thicknesses were <80 μm for the thinnest and <188 μm for most representative fibrous cap thickness. Prospective imaging studies are required to establish the significance of these values.

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.

Statins and cardiovascular diseases: from cholesterol lowering to pleiotropy

Statins are 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors, which are prescribed extensively for cholesterol lowering in the primary and secondary prevention of cardiovascular disease. Recent compelling evidence suggests that the beneficial effects of statins may not only be due to their cholesterol lowering effects, but also, to their cholesterol-independent or pleiotropic effects. Through these so-called pleiotropic effects, statins are directly involved in restoring or improving endothelial function, attenuating vascular remodeling, inhibiting vascular inflammatory response, and perhaps, stabilizing atherosclerotic plaques. These cholesterol-independent effects of statins are predominantly due to their ability to inhibit isoprenoid synthesis, the products of which are important lipid attachments for intracellular signaling molecules, such as Rho, Rac and Cdc42. In particular, inhibition of Rho and its downstream target, Rho-associated coiled-coil containing protein kinase (ROCK), has emerged as the principle mechanisms underlying the pleiotropic effects of statins. This review provides an update of statin-mediated vascular effects beyond cholesterol lowering and highlights recent findings from bench to bedside to support the concept of statin pleiotropy.

Attenuated severity of new acute ischemic events in patients with previous coronary heart disease receiving long-acting nitrates

BACKGROUND

Platelet aggregation and secondary vasoconstriction are key events in the genesis of acute coronary syndromes.

HYPOTHESIS

Since nitrates have vasodilatory and antiaggregant effects, treatment with long-acting nitrates at the time of onset of acute coronary syndromes could be associated with attenuation of their severity.

METHODS

A consecutive series of 533 patients with acute coronary syndrome and past history of coronary artery disease admitted to the Cardiology Service of a general hospital was studied. A specific questionnaire assessed the use of nitrates and other relevant drugs, as well as other clinical variables. The diagnosis of unstable angina or acute myocardial infarction (MI) was established according to clinical, electrocardiographic, and enzymatic criteria.

RESULTS

In the whole cohort, 169 patients had MI and 364 had unstable angina. Previous use of long-acting nitrates was significantly more common in patients with unstable angina (56%) than in those with MI (37%) (p < 0.0001). Multivariate analysis identified being a nonsmoker [odds ratio: 95%, confidence limits (CL) 0.37, 0.23-0.59], previous unstable angina (CL 0.62, 0.41-0.92), use of aspirin (CL 0.58, 0.41-0.92), and use of long-acting nitrates (CL 0.61, 0.40-0.93) as the independent predictors of the development of unstable angina rather than MI; of these the combination of nitrates and aspirin was the strongest predictor.

CONCLUSIONS

Long-acting nitrates as well as aspirin are suggested to have a protective or modifying effect on the development of acute coronary syndromes, favoring unstable angina rather than acute MI.

Future directions in thrombolysis

An extensive body of research conducted in the past 25 years has helped foster understanding of the mechanisms and pathogenesis of the acute coronary syndromes and occlusive disease. Thus, it is well established that thrombosis is caused by vascular injury and that immediate lysis of the arterial thrombus and subsequent prevention of thrombotic reocclusion are critical to the treatment of these disorders. Remarkable progress in the understanding of the biological and molecular mechanisms involved in vascular-wall-platelet interactions, platelet-platelet interactions, and coagulation has led to the identification of multiple targets for drug discovery and the development of numerous antithrombotic drugs. The purpose of this article is to review emerging antithrombotic therapies, introduce potential future molecular targets for drug discovery efforts, and discuss novel strategies for managing patients with coronary disease.

Olive oil and walnut breakfasts reduce the postprandial inflammatory response in mononuclear cells compared with a butter breakfast in healthy men

BACKGROUND

Inflammation is crucial in all stages of atherosclerosis, and few studies have investigated the effect of dietary fat on markers of inflammation related to this disease during the postprandial period.

OBJECTIVE

To evaluate the chronic effects of dietary fat on the postprandial expression of proinflammatory genes in peripheral blood mononuclear cells (PBMCs) in healthy subjects.

DESIGN

20 healthy men followed three different diets for 4 weeks each, according to a randomized crossover design: Western diet: 15% protein, 47% carbohydrates (CHO), 38% fat (22% saturated fatty acid (SFA)); Mediterranean diet: 15% protein, 47% CHO, 38% fat (24% monounsaturated fatty acid (MUFA)); CHO-rich and n-3 diet: 15% protein, 55% CHO, <30% fat (8% polyunsaturated fatty acid (PUFA)). After 12-h fast, volunteers were given a breakfast with a fat composition similar to that consumed in each of the diets-butter breakfast: 35% SFA; olive oil breakfast: 36% MUFA; walnut breakfast: 16% PUFA, 4% alpha-linolenic acid (LNA).

RESULTS

The butter breakfast induced a higher increase in tumor necrosis factor (TNF)-alpha messenger RNA (mRNA) expression than the olive oil or walnut breakfasts (P=0.014) in PBMCs. Moreover, we found a higher postprandial response in the mRNA of interleukin (IL)-6 with the intake of butter and olive oil breakfasts than with the walnut breakfast (P=0.025) in these cells. However, the effects of the three fatty breakfasts on the plasma concentrations of these proinflammatory parameters showed no significant differences (P=N.S.).

CONCLUSION

Consumption of a butter-enriched meal elicits greater postprandial expression of proinflammatory cytokine mRNA in PBMCs, compared to the olive oil and walnut breakfasts.

Coronary revascularization treatment based on dual-source computed tomography

Therapy advice based on dual-source computed tomography (DSCT) in comparison with coronary angiography (CAG) was investigated and the results evaluated after 1-year follow-up. Thirty-three consecutive patients (mean age 61.9 years) underwent DSCT and CAG and were evaluated independently. In an expert reading (the “gold standard”), CAG and DSCT examinations were evaluated simultaneously by an experienced radiologist and cardiologist. Based on the presence of significant stenosis and current guidelines, therapy advice was given by all readers blinded from the results of other readings and clinical information. Patients were treated based on a multidisciplinary team evaluation including all clinical information. In comparison with the gold standard, CAG had a higher specificity (91%) and positive predictive value (PPV) (95%) compared with DSCT (82% and 91%, respectively). DSCT had a higher sensitivity (96%) and negative predictive value (NPV) (89%) compared with CAG (91% and 83%, respectively). The DSCT-based therapy advice did not lead to any patient being denied the revascularization they needed according to the multidisciplinary team evaluation. During follow-up, two patients needed additional revascularization. The high NPV for DSCT for revascularization assessment indicates that DSCT could be safely used to select patients benefiting from medical therapy only.

Heparin versus placebo for acute coronary syndromes

BACKGROUND

Acute coronary syndromes (ACS) represent a spectrum of disease including unstable angina (UA) and non-ST segment myocardial infarction (NSTEMI). Despite treatment with aspirin, beta-blockers and nitroglycerin, UA/NSTEMI is still associated with significant morbidity and mortality. Although emerging evidence suggests that low molecular weight heparin (LMWH) is more efficacious compared to unfractionated heparin (UFH), there is limited data to support the role of heparins as a drug class in the treatment of ACS.

OBJECTIVES

To determine the effect of heparins (UFH and LMWH) compared with placebo for the treatment of patients with ACS.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (issue 4, 2002), MEDLINE (1966 to May 2002), EMBASE (1980 to May 2002) and CINAHL (1982 to May 2002). Authors of included studies and pharmaceutical industry representatives were contacted to determine if unpublished studies which met the inclusion criteria were available.

SELECTION CRITERIA

Randomized controlled trials of parenteral UFH or LMWH versus placebo in people with ACS (UA or NSTEMI).

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed quality of studies. Data were extracted independently by two reviewers. Study authors were contacted to verify and clarify missing data.

MAIN RESULTS

Eight studies (3118 participants) were included in this review. We found no evidence for difference in overall mortality between the groups treated with heparin and placebo (RR = 0.84, 95% CI 0.36 to 1.98). Heparins reduced the occurrence of MI (RR = 0.40, 95% CI 0.25 to 0.63, NNT = 33). An increase in the incidence of minor bleeds (RR = 6.80, 95% CI 1.23 to 37.49, NNH = 17).

AUTHORS' CONCLUSIONS

Compared to placebo, patients treated with heparins had similar risk of mortality, revascularization, recurrent angina, major bleeding and thrombocytopenia. However, those treated with heparins had decreased risk of MI and a higher incidence of minor bleeding.

Interleukin-18 promoter polymorphism associates with the occurrence of sudden cardiac death among Caucasian males: the Helsinki Sudden Death Study

OBJECTIVE

The increased plasma concentrations of pro-atherogenic and cardiomyocyte hypertrophic cytokine interleukin 18 (IL-18) predict mortality in patients with coronary heart disease (CHD) in addition to predicting the outcome of heart failure. The IL-18 gene has a functional -137G/C polymorphism (rs187238) in the promoter region. The C allele carriage is associated with attenuated IL-18 production. The effect of IL-18 genotype on SCD is unknown. We studied the association of the IL-18 gene -137G/C polymorphism with the occurrence of sudden cardiac death (SCD).

METHODS

Using the TaqMan 5' nuclease assay, we genotyped two independent consecutive and prospective autopsy series which were included in the Helsinki Sudden Death Study.

RESULTS

Of the 663 men, 359 (54.1%) had the wild-type GG-genotype, 261 (39.4%) were heterozygotes (CG) and 43 (6.5%) were CC homozygotes. Compared to the GG homozygotes, the C allele carriers (i.e. subjects having CC or CG genotypes) had a lower adjusted risk for SCD from any cause (odds ratio [OR] 0.49; 95% confidence interval [CI], 0.31-0.77, p=0.002), for SCD due to CHD (OR 0.51; 95% CI, 0.32-0.82, p=0.005), and for SCD caused by non-coronary heart diseases (OR 0.34; 95% CI 0.13-0.90, p=0.030).

CONCLUSION

IL-18 promoter -137G/C polymorphism, which regulates the expression of IL-18, is an important predictor of SCD from any cause as well as SCD in patients with and without underlying CHD.

The impact of expansive arterial remodeling on clinical presentation in carotid artery disease: a multidetector CT angiography study

BACKGROUND AND PURPOSE

Atherosclerotic arterial remodeling has been described in the coronary circulation but has not been studied extensively for carotid atherosclerosis. The purpose of our study was to examine the association between carotid artery remodeling and clinical presentation in patients with significant stenosis by using multidetector row CT (MDCT).

MATERIALS AND METHODS

One hundred eight patients with >or=50% stenosis (North American Symptomatic Carotid Endarterectomy Trial criteria) by MDCT angiography between January 2004 and June 2006 were identified. The study group included 37 symptomatic (65.9 +/- 13.0 years; 12 women; stenosis, 81.5 +/- 12.2%; 17 with stroke; 15 with transient ischemic attack; 5 with amaurosis fugax) and 71 asymptomatic patients (70.5 +/- 10.5 years; 28 women; stenosis, 78.8 +/- 11.1%). Remodeling ratio (RR) was calculated by dividing the outer vessel circumference at the site of greatest stenosis by a normal reference-segment vessel circumference. Maximum vessel thickness (MxVT) and eccentricity index (EI) of the plaque, defined as maximal thickness/minimal thickness at the site of greatest luminal narrowing, were also determined. Data were analyzed by using an independent t test.

RESULTS

The RR was significantly higher in symptomatic patients (1.64 +/- 0.44) than in asymptomatic patients (1.41 +/- 0.5) (P=.02). There was no significant difference in MxVT in symptomatic (5.9 +/- 2.1 mm) and asymptomatic patients (5.6 +/- 2.4 mm) (P=.45) and no significant difference in EI (symptomatic, 4.7 +/- 2.7; asymptomatic, 4.3 +/- 2.2; P=.38).

CONCLUSION

In this series of subjects with significant internal carotid artery stenosis, expansive carotid remodeling was significantly greater in patients with cerebral ischemic symptoms than in asymptomatic patients. The extent of expansive remodeling may indicate underlying atherosclerotic plaque vulnerability. MDCT has a role in the evaluation of carotid artery disease beyond examining luminal stenosis.

Lesional Overexpression of Matrix Metalloproteinase-9 Promotes Intraplaque Hemorrhage in Advanced Lesions But Not at Earlier Stages of Atherogenesis

Background— Matrix metalloproteinase-9 (MMP-9) is involved in atherosclerosis and elevated MMP-9 activity has been found in unstable plaques, suggesting a crucial role in plaque rupture. This study aims to assess the effect of MMP-9 on plaque stability in apolipoprotein E-deficient mice at different stages of plaque progression.

Methods and Results— Atherosclerotic lesions were elicited in carotid arteries by perivascular collar placement. MMP-9 overexpression in intermediate or advanced plaques was effected by intraluminal incubation with an adenovirus (Ad.MMP-9). A subset was coincubated with Ad.TIMP-1. Mock virus served as a control. Plaques were analyzed histologically. In intermediate lesions, MMP-9 overexpression induced outward remodeling, as shown by a 30% increase in media size ( p =0.03). In both intermediate and advanced lesions, prevalence of vulnerable plaque morphology tended to be increased. Half of MMP-9–treated lesions displayed intraplaque hemorrhage, whereas in controls and the Ad.MMP-9/Ad.TIMP-1 group this was 8% and 16%, respectively ( p =0.007). Colocalization with neovessels may point to neo-angiogenesis as a source for intraplaque hemorrhage.

Conclusion— These data show a differential effect of MMP-9 at various stages of plaque progression and suggest that lesion-targeted MMP-9 inhibition might be a valuable therapeutic modality in stabilizing advanced plaques, but not at earlier stages of lesion progression.

Therapeutic potential of nanoparticulate systems for macrophage targeting

The use of non-viral nanoparticulate systems for the delivery of therapeutic agents is receiving considerable attention for medical and pharmaceutical applications. This increasing interest results from the fact that these systems can be designed to meet specific physicochemical requirements, and they display low toxic and immunogenic effects. Among potential cellular targets by drug-loaded nanoparticles, macrophages are considered because they play a central role in inflammation and they act as reservoirs for microorganisms that are involved with deadly infectious diseases. The most common and potent drugs used in macrophage-mediated diseases treatment often induce unwanted side effects, when applied as a free form, due to the necessity of high doses to induce a satisfactory effect. This could result in their systemic spreading, a lack of bioavailability at the desired sites, and a short half-life. Therefore, the use of drug-loaded nanoparticles represents a good alternative to avoid, or at least decrease, side effects and increase efficacy. In this manuscript, we present an overview of the usefulness of nanoparticles for macrophage-mediated therapies in particular. We discuss, though not exhaustively, the potential of therapeutic agent-loaded nanoparticles for some macrophage-mediated diseases. We also underline the most important parameters that affect the interaction mechanisms of the macrophages and the physicochemical aspects of the particulate systems that may influence their performance in macrophage-targeted therapies.

The pleiotropic effects of statins

PURPOSE OF REVIEW

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the most widely prescribed drugs worldwide for lowering cholesterol levels. In use for more than 15 years, they have demonstrated efficacy, safety, and tolerability across a broad range of patients. This class of drugs has been designed to lower the cholesterol level by competitively inhibiting the enzyme responsible for its biosynthesis and thereby to play a major role in reducing cardiovascular risk. However, both basic evidence and clinical evidence also supports the idea that reductions in cardiovascular risk are dependent on mechanisms beyond cholesterol reduction alone, such as the reduction of endothelial dysfunction, inhibition of inflammatory responses, stabilization of atherosclerotic plaques, and modulation of procoagulant activity and platelet function.

RECENT FINDINGS

In fact, as shown in several clinical trials, the beneficial effects of statin treatment begin earlier than its cholesterol-lowering effect. These other mechanisms could act in concert with the potent low-density lipoprotein cholesterol-lowering effects of this class of drugs to exert early and lasting cardiovascular protective effects. Recently, several studies have shown that an intensive lipid-lowering regimen with a statin provides greater protection against death or major cardiovascular events than does a standard regimen.

SUMMARY

This review summarizes the new findings in these pleiotropic effects and describes their impact on vascular processes.

Effects of statins on 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibition beyond low-density lipoprotein cholesterol

Statins are potent inhibitors of cholesterol biosynthesis and exert beneficial effects in the primary and secondary prevention of coronary artery disease. However, the overall benefits observed with statins appear to occur much earlier and to be greater than what might be expected from changes in lipid levels alone, suggesting effects beyond cholesterol lowering. Indeed, recent studies indicate that some of the cholesterol-independent or "pleiotropic" effects of statins involve improving endothelial function, enhancing the stability of atherosclerotic plaques, decreasing oxidative stress and inflammation, and inhibiting the thrombogenic response. Many of these pleiotropic effects are mediated by inhibition of isoprenoids, which serve as lipid attachments for intracellular signaling molecules. In particular, inhibition of the small guanosine triphosphate-binding proteins Rho, Ras, and Rac, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in mediating the pleiotropic effects of statins.

Pleiotropic effects of statins

Statins are potent inhibitors of cholesterol biosynthesis. In clinical trials, statins are beneficial in the primary and secondary prevention of coronary heart disease. However, the overall benefits observed with statins appear to be greater than what might be expected from changes in lipid levels alone, suggesting effects beyond cholesterol lowering. Indeed, recent studies indicate that some of the cholesterol-independent or "pleiotropic" effects of statins involve improving endothelial function, enhancing the stability of atherosclerotic plaques, decreasing oxidative stress and inflammation, and inhibiting the thrombogenic response. Furthermore, statins have beneficial extrahepatic effects on the immune system, CNS, and bone. Many of these pleiotropic effects are mediated by inhibition of isoprenoids, which serve as lipid attachments for intracellular signaling molecules. In particular, inhibition of small GTP-binding proteins, Rho, Ras, and Rac, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in mediating the pleiotropic effects of statins.

Gender differences in blood velocities across carotid stenoses

OBJECTIVES

Carotid duplex scanning is the standard test for documenting carotid disease. Carotid endarterectomy effectively reduces stroke in selected patients with carotid artery disease. Data from large national randomized trials suggest that the benefits of CEA may be gender dependent. Because many diagnoses are made and treatment is based on the results of carotid duplex ultrasound scanning alone, it is important to determine whether different diagnostic thresholds should be used in men and women. The purpose of this study was 2-fold: to examine whether there is an overall gender difference in carotid velocity at similar arteriographic stenoses, and to determine whether there are significant differences at clinically relevant thresholds of disease.

METHODS

A database of 938 carotid arteriogram entries was established prospectively, with accompanying measurements of peak systolic velocity (PSV) and end-diastolic velocity (EDV). The percent of internal carotid artery stenosis seen on arteriograms was calculated according to criteria from the North American Symptomatic Carotid Endarterectomy Trial. Analyses were made in 536 carotid arteries in men and 402 carotid arteries in women. In addition, the single most diseased artery per patient was analyzed by gender. PSV and EDV were averaged for data subsets according to 10% intervals of internal carotid artery stenoses. Velocity for each interval was compared between men and women with the Student t test. Receiver operator characteristic curves were developed to define optimal duplex criteria for 60% and 70% stenosis.

RESULTS

For all intervals, PSV and EDV averaged 9% and 6% higher, respectively, in women than in men. Significant gender differences existed between PSV and EDV for 60% and 70% stenosis (P = .03). When a single vessel per patient was analyzed these observations persisted, but lost significance for PSV at 60% stenosis (P = .18). Receiver operator characteristic curves at 90% sensitivity demonstrated that optimal PSV for 60% stenosis was 160 cm/s and 180 cm/s, and for 70% stenosis was 185 cm/s and 202 cm/s, in male and female patients, respectively.

CONCLUSIONS

Women have higher carotid blood flow velocity than men do. Gender differences exist, and are notably different at clinically relevant thresholds for intervention. These data indicate that different criteria should be used for interpreting carotid velocity profiles in women than in men, and have potentially important implications for patient care.

The expanding scope of the metabolic syndrome and implications for the management of cardiovascular risk in type 2 diabetes with particular focus on the emerging role of the thiazolidinediones

Over the last decade, new factors including endothelial dysfunction, vascular inflammation, and abnormalities of blood coagulation have joined more established components of the metabolic syndrome, such as hyperglycemia, hypertension, dyslipidemia, and visceral obesity. Many of these factors are known to promote atherosclerosis and the clustering of metabolic abnormalities within the syndrome makes a major contribution to the increased risk of cardiovascular disease and death associated with type 2 diabetes. Given that most patients have multiple cardiovascular risk factors, good glycemic control does not, by itself, adequately reduce the burden of cardiovascular disease associated with diabetes and clinical management needs to address the full profile of cardiovascular risk. The thiazolidinediones have potentially beneficial effects on many components of the metabolic syndrome and so may help to improve cardiovascular outcomes in type 2 diabetes.

Acetylsalicylic acid inhibits cell proliferation by involving transforming growth factor-beta

BACKGROUND

Acetylsalicylic acid (ASA) inhibits cell proliferation. This may be mediated by transforming growth factor-beta (TGF-beta). TGF-beta directly stops cell proliferation, restrains cells in G(0), and inhibits the uptake of platelet-derived growth factor and insulin-like growth factor. These effects are identical to those observed with ASA treatment.

METHODS AND RESULTS

We cultured rat thoracic aorta vascular smooth muscle cells and measured cytotoxicity, cell proliferation, cell cycle, transcription of TGF-beta1, and concentration of TGF-beta1 in supernatant medium. ASA dose-dependently restrained cells in G(0) phase with no cytotoxic effect and inhibited cell proliferation by 30.86%. Anti-TGF-beta1 reversed this inhibition by 30.21%. However, ASA treatment decreased TGF-beta1 transcription and had no significant effect on TGF-beta1 concentration.

CONCLUSIONS

TGF-beta seems to play an important role in ASA-mediated inhibition of cell proliferation. Therefore, treatment with ASA prevents coronary disease not only by means of its antiplatelet properties but also by an important inhibition of plaque growth. This relationship between ASA and TGF-beta explains many other effects, such as cancer chemoprevention, immunomodulation, and wound healing. The aim of this study was to demonstrate this link.

Low molecular weight heparins versus unfractionated heparin for acute coronary syndromes

BACKGROUND

Acute coronary syndromes (ACS) are an important source of morbidity and mortality. Despite weak evidence for the use of unfractionated heparin (UFH) for acute coronary syndromes it is considered an accepted treatment for unstable angina and non-ST segment elevation myocardial infarction (MI). However, evidence suggests low molecular weight heparins (LMWH) are safer and more effective than UFH in the treatment and prevention of other thrombotic disorders.

OBJECTIVES

To assess the effects of LMWH compared to UFH for acute coronary syndromes.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register (the Cochrane Library issue 4, 2000), MEDLINE (January 1966 to December 2000), EMBASE (1980 to December 2000) and CINAHL (1982 to December 2000) and reference lists of articles. Authors of all include studies and pharmaceutical industry representatives were contacted to determine if unpublished studies which met the inclusion criteria were available.

SELECTION CRITERIA

Randomized controlled trials of subcutaneous LMWH versus intravenous UFH in people with acute coronary syndromes (unstable angina or non-ST segment elevation MI).

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed quality of studies. Data were extracted independently by two reviewers. Study authors were contacted to verify and clarify missing data.

MAIN RESULTS

We identified 27 potentially relevant studies, 7 studies (11,092 participants) were included in this review. We found no evidence for difference in overall mortality between the groups treated with LMWH and UFH (RR = 1.0; 95% CI: 0.69, 1.44). Some pooled outcomes showed some evidence of heterogeneity, few of the pooled outcomes were statistically heterogeneous most were homogeneous. LMWH reduced the occurrence of MI (RR = 0.83; 95% CI: 0.70, 0.99) and the need for revascularization procedures (RR = 0.88; 95% CI: 0.82, 0.95). We found no evidence for difference in occurrence of recurrent angina (RR = 0.83; 95% CI: 0.68, 1.02), major bleeds (RR = 1.00; 95% CI: 0.80, 1.24) or minor bleeds (RR = 1.40; 95% CI: 0.66, 2.90). A decrease in the incidence of thrombocytopenia (RR = 0.64; 95% CI: 0.44, 0.94) was observed for patients given LMWH. From these results, 125 patients need to be treated with LMWH to prevent 1 additional MI and 50 patients need to be treated to prevent 1 revascularization procedure. Insufficient data exist to compare different types of LMWH.

REVIEWER'S CONCLUSIONS

LMWH and UFH had similar risk of mortality, recurrent angina, and major or minor bleeding but LMWH had decreased risk of MI, revascularization and thrombocytopenia. New Trials with longer follow up are required.

Dialing 911: a call to action

Cardiovascular disease and stroke are the nation's leading causes of disability and death. Scientific advances have provided newer treatments that, when applied effectively and in time, save a significant number of lives. Multiple factors in our system of delivery impede our ability to apply effective treatments, but with an analysis of the components of care, each of us can take leadership roles in our communities to improve the chain of survival. These elements and the science supporting each are briefly reviewed.

New tools for coronary risk assessment: what are their advantages and limitations?

The concept of risk assessment and reduction, introduced initially by the Framingham Heart Study and refined in other models, forms the cornerstone of preventive cardiology. Risk factor assessment determines the therapeutic strategy, because the intensity of preventive intervention is tailored to the patient's risk of coronary heart disease. The conventional risk factors for coronary heart disease include elevated serum total cholesterol and LDL cholesterol, low HDL cholesterol, elevated blood pressure, cigarette smoking, diabetes, vascular disease, menopausal status (women only), and age. Aggressive risk factor reduction, formerly used exclusively in secondary prevention, may be pivotal to optimal patient management in high-risk primary prevention. A number of noninvasive imaging modalities have the potential to measure and to monitor atherosclerosis in asymptomatic individuals and include exercise ECG testing, electron beam computed tomography, magnetic resonance coronary angiography, positron emission tomography, ankle-brachial index, and B-mode ultrasound. Novel serum markers, including C-reactive protein and homocysteine, have the ability to gauge risk in the individual patient. Systemic therapy for risk reduction in primary prevention may be preferable to local therapy (eg, angioplasty and bypass) and may more effectively prevent acute coronary events than these more invasive approaches.

Pleiotropic effects of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors or statins are potent inhibitors of cholesterol biosynthesis. Several large clinical trials have demonstrated the beneficial effects of statins in the primary and secondary prevention of coronary heart disease. However, the overall clinical benefits observed with statin therapy appear to be greater than what might be expected from changes in lipid profile alone, suggesting that the beneficial effects of statins may extend beyond their effects on serum cholesterol levels. Indeed, recent experimental and clinical evidence indicates that some of the cholesterol-independent or "pleiotropic" effects of statins involve improving or restoring endothelial function, enhancing the stability of atherosclerotic plaques, and decreasing oxidative stress and vascular inflammation. Many of these pleiotropic effects of statins are mediated by their ability to block the synthesis of important isoprenoid intermediates, which serve as lipid attachments for a variety of intracellular signaling molecules. In particular, the inhibition of small GTP-binding proteins, Rho, Ras, and Rac, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in mediating the direct cellular effects of statins on the vascular wall.

Seasonal variation of some metabolic and haemostatic risk factors in subjects with and without coronary artery disease

Acute myocardial infarction (AMI) is more frequent in winter months than in summer months. The aetiologic mechanisms underlying this seasonal pattern are poorly understood. We investigate whether seasonal variation of metabolic and haemostatic coronary risk factors exists, and whether this variation is more pronounced in subjects with coronary artery disease (CAD). In 82 subjects (47 free of clinical signs of CAD and in 35 survivors of AMI), measurements of body mass index (BMI), lipoproteins, glucose, insulin, plasminogen activator inhibitor-1, tissue-type plasminogen activator (t-PA), euglobulin clot lysis time, fibrinogen, and platelet count were performed twice in the cold months (December and March) and twice in the warm months (June and September). Significantly higher BMI (26.8 versus 26.2 kg/m2, P < 0.01), glucose (5.5 versus 5.1 mmol/l, P < 0.01), total cholesterol (5.61 versus 5.32 mmol/l, P < 0.05), low-density lipoprotein cholesterol (3.63 versus 3.34 mmol/l, P < 0.05), triglycerides (1.79 versus 1.61 mmol/l, P < 0.01), Lp(a) (270.7 versus 237.5 mg/l, P < 0.01), fibrinogen level (3.50 versus 2.95 g/l, P < 0.00001), platelet count (212 x 10(9) versus 173 x 10(9)/l, P < 0.01) and significantly lower high-density lipoprotein cholesterol level (1.22 versus 1.28 mmol/l, P < 0.05) were observed in the cold months compared with the warm months. Significant seasonal variation of t-PA activity (1.19 versus 0.87 IU/ml, P = 0.015) and t-PA antigen (8.5 versus 7.3 ng/ml, P = 0.05) was demonstrated only in subjects with CAD. Clustering of peak values of several metabolic and haemostatic coronary risk factors was observed in winter months. This variation might be of aetiopathogenetic importance for the seasonal pattern of acute myocardial infarction.

Definition, classification, and pathophysiology of acute coronary ischemic syndromes

The acute coronary syndrome (ACS) is now used to describe a spectrum of clinical presentations that share an underlying pathophysiology, replacing the previous nomenclature of ischemic chest pain. The accurate diagnosis and proper management of patients with these entities require the emergency medicine physician to consider the entire spectrum of ACS, with emphasis placed on early diagnosis and rapid treatment. Each of these syndromes has its own prognosis, pathophysiology, and specific management strategy.

Healed plaque ruptures and sudden coronary death: evidence that subclinical rupture has a role in plaque progression

BACKGROUND

Subclinical episodes of plaque disruption followed by healing are considered a mechanism of increased plaque burden. Detailed pathological studies of healed ruptures, however, are lacking.

METHODS AND RESULTS

We identified acute and healed ruptures from 142 men who died of sudden coronary death and performed morphometric measurements of plaque burden, luminal stenosis, and smooth muscle cell phenotype. Healed ruptures were found in 61% of hearts and were associated with healed myocardial infarction, increased heart weight, dyslipidemia, and diabetes. Multiple healed rupture sites with layering were frequently found in segments with acute and healed rupture; the percent area luminal narrowing increased with increased numbers of healed sites of previous rupture. The underlying percent luminal narrowing for acute ruptures (mean 79+/-15%) exceeded that for healed ruptures (mean 66+/-14%, P:=0.0001), and the area within the internal elastic lamina was significantly less in healed ruptures than in acute ruptures, when segments were grouped by distance from the ostium. Healed ruptures favored the accumulation of immature smooth muscle cells at repair sites, with a cellular proliferation index of 0.40+/-0.09%, significantly higher than the index at the sites of rupture (P:=0.008).

CONCLUSIONS

These data provide evidence that silent plaque rupture is a form of wound healing that results in increased percent stenosis. Healed ruptures occur in arteries with less cross-sectional area luminal narrowing than acute ruptures and are a frequent finding in men who die suddenly with severe coronary atherosclerosis.

[Cellular and molecular biology of atherosclerotic lesions]

The association of atherosclerosis with the most common risk factors including elevation of low density lipoprotein (LDL) levels, diabetes, hypertension and cigarette smoking, led to the hypothesis of "response to injury" to explain how the lesions develop. According to this hypothesis, one of the earliest events in atherogenesis is the accumulation of LDL in the arterial wall where they undergo oxidation. These LDL impair endothelial function, and thus, all the antiatherogenic properties of the endothelium. In addition, macrophages and smooth muscle cells take up these LDL, through different receptors, and become foam cells. The accumulation of foam cells in the arterial wall contributes to lesion development. Therefore, lesion development involves the activation of endothelial cells, as well as smooth muscle cells and monocytes/macrophages. In this activation different growth factors (PDGF, EGF, etc.), cytokines (IL-1b, TNFa, etc.) and the modified LDL themselves, play an important role. Through several signal transduction pathways these molecules activate transcription factors, such as the nuclear factor kappa B (NF-kB) or protooncogenes such as c-fos, c-myc, that regulate the expression of genes involved in the inflammatory/proliferative response of the lesions.

The vulnerable coronary plaque

Vulnerable coronary plaques are asymptomatic atherosclerotic lesions with the tendency to rupture. Plaque rupture is the initiating event in most acute coronary syndromes including sudden cardiac death, acute myocardial infarction, and unstable angina. Vulnerable plaques are commonly found in coronary arteries at autopsy but are virtually undetectable by standard diagnostic techniques such as stress testing and coronary angiography. Using new imaging techniques, in particular intravascular ultrasound and magnetic resonance imaging (MRI), scientists are now able to identify these plaques in vivo. A better understanding of the pathophysiology of plaque vulnerability and rupture will eventually lead to the therapeutic goal of plaque stabilization in the prevention of acute coronary syndromes. This article reviews the role of plaque vulnerability in coronary artery disease. The anatomy and pathophysiology of vulnerable plaques as well as diagnostic and therapeutic implication will be described.

Long-term experience with an accelerated protocol for diagnosis of chest pain

CONTEXT

More than 6 million patients present annually with chest pain suggestive of acute coronary syndrome. Rapid and accurate diagnosis is essential for best clinical outcomes, for optimal management of hospital resources, and for minimizing medicolegal exposure.

OBJECTIVE

To evaluate the clinical and cost outcomes of an accelerated protocol for chest pain triage in a community-based hospital of moderate size.

METHODS

One hundred successive patients with chest pain were diagnosed according to the Traditional Chest Pain Protocol, which included testing of serial blood samples for creatine kinase (CK)-MB and total CK. These patients were also subjected to the Accelerated Chest Pain Protocol under evaluation, which included testing at shortened intervals for myoglobin and cardiac troponin I in addition to CK and CK-MB. Diagnostic sensitivity and specificity were compared versus the final assigned diagnosis. The Accelerated Chest Pain Protocol was implemented for routine use. Follow-up evaluations were conducted at 1 month (test group A, N = 180) and 22 months (test group B, N = 180). Costs for diagnosis and treatment of the 2 test groups were compared with those for the control group.

RESULTS

The 2 protocols had equivalent specificity values (99%). The sensitivity of the Accelerated Chest Pain Protocol was higher than that of the Traditional Chest Pain Protocol (95% vs 58%). Cost savings of 29% and a reduction in length of stay of 33% were achieved in test group B versus the control group.

CONCLUSIONS

The Accelerated Chest Pain Protocol improved the accuracy and timeliness of diagnosis of acute coronary syndrome while reducing costs.

The good smooth muscle cells in atherosclerosis

The formation of a fibrous cap made up of intimal smooth muscle cells and connective tissue is part of an attempt by the vessel wall to encapsulate the toxic products accumulating in the necrotic core of atherosclerotic lesions, and should be viewed as a beneficial healing response. In this review, we discuss the development of the intima and the potential origins of the intimal smooth muscle cell with a focus on the unique properties of these cells. We further discuss the role of intimal smooth muscle cells in plaque rupture and in wound healing, and the relationship of wound healing to the loss of lumen that occurs with development of advanced atherosclerotic lesions.