From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: Part I

Molecular imaging by MRI

The goal of molecular imaging is to detect pathologic biomarkers, which can lead to early recognition of diseases, better therapeutic management, and improved monitoring for recurrence. MRI is a particularly attractive method for molecular imaging applications, due to its noninvasive nature, outstanding signal to noise ratio, high spatial resolution, exceptional tissue contrast, and short imaging times. Site-specific MRI contrast agents have been developed to target biologic processes that occur early in the development of atherosclerotic plaques, including angiogenesis and lipid accumulation, or biosignatures that appear later, such as fibrin and tissue factor resulting from plaque rupture. Moreover, targeted contrast agents can also serve as drug delivery vehicles, combining diagnosis and therapy. If ultimately successful, these emerging molecular imaging agents and techniques will allow early disease recognition and quantification prompting therapeutic intervention before serious sequelae ensue.

Integrating Soluble Biomarkers and Imaging Technologies in the Identification of Vulnerable Atherosclerotic Patients

The clinical utility of a biomarker depends on its ability to identify high-risk individuals to optimally manage the patient. A new biomarker would be of clinical value if it is accurate and reliable, provides good sensitivity and specificity, and is available for widespread application. Data are accumulating on the potential clinical utility of integrating imaging technologies and circulating biomarkers for the identification of vulnerable (high-risk) cardiovascular patients. A multi-biomarker strategy consisting of markers of inflammation, hemostasis and thrombosis, proteolysis and oxidative stress, combined with new imaging modalities (optical coherence tomography, virtual histology plus IVUS, PET) can increase our ability to identify such thombosis-prone patients. In an ideal scenario, cardiovascular biomarkers and imaging combined will provide a better diagnostic tool to identify high-risk individuals and also more efficient methods for effective therapies to reduce such cardiovascular risk. However, additional studies are required in order to show that this approach can contribute to improved diagnostic and therapeutic of atherosclerotic disease.

Development and validation of novel imaging technologies to assist translational studies in atherosclerosis

In the past decade, significant progress has been made to visualize atherosclerotic disease. Until recently, imaging technologies mainly focused on lumen and vessel wall visualization. Current advances and knowledge on the molecular mechanisms of initiation and progression of atherosclerosis has emphasized the need for imaging technologies and probes that can image function and biology rather than anatomy. This field of molecular imaging is now in rapid development with new imaging agents that aim at visualizing processes involved in atherosclerosis such as inflammation, macrophage activation, protease activity, angiogenesis, apoptosis, lipid accumulation and thrombus formation.:

The renin-angiotensin system and atherosclerosis

Atherosclerosis is an insidious and complex disease of large- and medium-sized arteries. The primum movens of the disease is characterized by co-localization of lipids, inflammatory cells, and fibrous elements within the intima of vessels. Starting as a "fatty streak," the disease evolves over decades into complex lesions that can progress toward a stable or a vulnerable plaque. During the past decade, we have become familiar with the features of the vulnerable plaque; however, the mechanisms that cause a stable plaque to change into a vulnerable lesion with its dramatic clinical outcome still remain largely unknown. There is good evidence from epidemiologic, experimental, and clinical studies that the renin-angiotensin system, via its active peptide angiotensin II, may contribute to atherosclerosis development and progression, not only by increasing blood pressure but also through multiple direct effects. Moreover, recent studies have shown a potential role for angiotensin II as a mediator of plaque vulnerability.

Genomic medicine and thrombotic risk: Who, when, how and why?

Major advances in Human Genome research could significantly change the clinical medical practice, providing new possibilities for both diagnosing and treating common pathologies. Many genetic tests are now commercially available for predicting future risk of common disorders. However, genetic testing has potential benefits but also limitations for the patients, and it should not be used to 'screen' the general population. Diagnostic assays for a predisposition of both venous and arterial thrombosis are among the most requested genetic tests in molecular diagnostics laboratories. However, there is considerable uncertainty as to how this information should be utilized in patient management. Both the medical community and the patients need to obtain accurate information concerning the appropriate use of genetic testing. The purpose of this article is to discuss the usefulness and the practical applications of thrombotic genetic testing in order to define which patients should be tested for both venous and arterial thrombotic risk as well as to have an acceptable cost/benefit ratio and to prevent patients' anxiety.

Resolution and SNR effects on carotid plaque classification

Multicontrast-weighted MRI, which is increasingly being used in combination with automatic classification algorithms, has the potential to become a powerful tool for assessing plaque composition. The current literature, however, does not address the relationship between imaging conditions and segmentation viability well. In this study 13 carotid endarterectomy samples were imaged with a 156-microm in-plane resolution and high signal-to-noise ratio (SNR) using proton density (PD), T1, T2, and diffusion weightings. The maximum likelihood (ML) algorithm was used to classify plaque components, with sets of three contrast weighting intensities used as features. The resolution and SNR of the images were then degraded. Classification accuracy was found to be independent of in-plane resolution between 156 microm and 1250 microm, but dependent on SNR. Accuracy decreased less than 10% for degradation in SNR down to 25% of original values, and decreased sharply thereafter. The robustness of automatic classifiers makes them applicable to a wide range of imaging conditions, including standard in vivo carotid imaging scenarios.

Characterization and molecular detection of atherothrombosis by magnetic resonance--potential tools for individual risk assessment and diagnostics

This review focuses on recent non-invasive or minimally invasive magnetic resonance (MR) approaches to study atherothrombosis. The potential benefits of combining diverse metabolic information obtained by the variety of MR techniques from tissues in vivo and ex vivo and from body fluids in vitro are also briefly discussed. A well established methodology is available for lipoprotein subclass quantification from plasma by 1H MR spectroscopy providing information for assessing the long-term risk of atherosclerosis. Multi-contrast MR imaging in vivo relying on endogenous contrast allows partial characterization of components in atherothrombotic plaques. The use of exogenous contrast agents in MR angiography enhances blood-tissue contrast and provides functional information on plaque metabolism, improving plaque characterization and assessment of plaque vulnerability by MR imaging. Recent applications of molecular targeted MR imaging have revealed novel opportunities for specific early detection of atherothrombotic processes, such as angiogenesis and accumulation of macrophages. Currently, MR imaging and spectroscopy can produce such metabolic in vivo and in vitro information that in combination could facilitate the screening, identification and follow-up of cardiovascularly vulnerable patients in research settings. The recent developments imply that in the near future MR techniques will be part of clinical protocols for individual diagnostics in atherothrombosis.

Acute occlusive large vessel disease leading to fatal stroke in a patient with systemic lupus erythematosus: Arteritis or atherosclerosis?

A woman with a history of systemic lupus erythematosus presented with extensive bilateral strokes due to acute inflammatory, occlusive large vessel disease affecting several aortic branches including the carotid, subclavian, renal, and iliac arteries. We quantitatively characterized the arterial inflammation in this patient and compared it with the inflammatory infiltrates from 22 patients with conventional atherosclerosis. Profound histomorphologic differences from conventional atherosclerosis (predominance of CD8-positive lymphocytes, relative absence of macrophages, no ectopic neovascularization, no signs of plaque hemorrhage, concentric instead of eccentrical stenosis) suggest that this patient's accelerated arteriopathy was precipitated by pathogenic events other than conventional atherosclerosis.

Ferumoxtran-10–Enhanced MRI of the Hypercholesterolemic Rabbit Aorta

OBJECTIVE

Ferumoxtran-10 is an MRI contrast agent, which accumulates in macrophages and induces magnetic susceptibility artifacts (MSAs). We evaluated the ability of ferumoxtran-10-enhanced MRI to quantify focal macrophage infiltration in the aortic wall of hypercholesterolemic rabbits.

METHODS AND RESULTS

Six weeks after a double-balloon injury of the infrarenal aorta, 12 hypercholesterolemic rabbits underwent MRI of the aorta before (first MRI) and after (second MRI) intravenous injection of ferumoxtran-10 (n=10) or saline (n=2). A third MRI was performed 5 days later to detect ferumoxtran-10-induced MSA in the aortic wall. Aortas were subsequently processed for histology, immunohistochemistry, and gelatin zymography studies. Injured aortas displayed a macrophage-rich neointima with high-matrix metalloproteinase 2 and 9 activities. Iron stain of injured aortas showed massive accumulation of ferumoxtran-10 in neointimal macrophages. Five days after the injection of ferumoxtran-10, MSAs were detected only in the injured aortas by in vivo MRI and were quantified indirectly using the percentage reduction of luminal area attributable to the extension of these MSAs in the aortic lumen. This parameter correlated with macrophage infiltration on corresponding aortic cross-sections (r=0.82; P<0.05).

CONCLUSIONS

Ferumoxtran-10-enhanced MRI allows quantitative assessment of macrophage infiltration induced by balloon angioplasty in the aorta of hypercholesterolemic rabbits.

Patients With Low High-Density Lipoprotein-Cholesterol or Smoking are More Likely to Develop Myocardial Infarction Among Subjects With a Visible Lesion or Stenosis in Coronary Artery

BACKGROUND

Traditional contrast coronary arteriography affords only an indirect view of aspects of atheromata related to their propensity to trigger thromboses, so it is urgent to recognize the vulnerable person who is more likely to develop myocardial infarction (MI) among patients with visible lesion or stenosis in coronary artery.

METHODS AND RESULTS

Two hundred and eighty-eight patients (144 MI patients, 144 controls) who had either a visible lesion or differing extent of stenosis in 1 or more major coronary arteries were consecutively enrolled. Lipid profile, C-reactive protein (CRP), smoking, hypertension, dyslipidemia and diabetes were analyzed for their association with MI. No differences in the prevalence of dyslipidemia, hypertension or diabetes was found between the patients with MI and those without, and CRP, triglycerides, total cholesterol and low-density lipoprotein-cholesterol levels did not differ between the 2 groups (all p>0.05). However, high-density lipoprotein-cholesterol (HDL-C) was significantly lower in the patients with MI than in those without (1.06+/-0.30 vs 1.14+/-0.32 mmol/L, p=0.024). On multivariate analysis after adjustment for age and gender, adjusted odds ratio (95% confidence interval) of MI was 0.44 (0.20-0.96) for HDL-C, p=0.038; 2.6 (1.48-4.56, p=0.001) for smoking, which indicated that high HDL-C was protective for MI, and smoking was associated with an increased risk of MI.

CONCLUSIONS

The present findings indicate that among subjects with a visible lesion or stenosis in coronary arteries, those with low HDL-C or smokers are more likely to develop MI.

Cardiovascular events in patients with coronary plaque rupture and nonsignificant stenosis

The long-term outcome of patients who present with an identified plaque rupture in a nonflow-limiting lesion is not well known. We retrospectively studied 17 consecutive patients in whom intravascular ultrasound identified plaque rupture in nonflow-limiting lesions (minimum lumen area >4.0 mm2) that were not treated with coronary intervention. After a mean follow-up of 43 +/- 25 months, events related to those lesions were 1 death (6%) of undetermined cause (6%) that occurred after 69 months, no myocardial infarction, and 2 revascularizations (12%) that occurred at 3 and 67 months. Overall, the cumulative rate of cardiac events was 18%.

Identification of cholesteryl esters in human carotid atherosclerosis by ex vivo image-guided proton MRS

Vulnerable atherosclerotic plaques may be identified by their large lipid component, particularly liquid cholesteryl ester (CE), covered by a fibrous cap. We hypothesized that image-guided 1H proton magnetic resonance spectroscopy (MRS) would identify mobile CE in discrete, preselected regions of atherosclerotic plaque. Human carotid endarterectomy specimens (n = 10) were imaged ex vivo by magnetic resonance imaging (MRI) at high field (11.7 T) utilizing standard T1- and T2-weighted spin echo protocols. MRS spectra were acquired from 1 mm3 voxels, localized to plaque regions that we judged by MRI to be lipid rich or lipid poor. The spectra revealed methyl and methylene resonances of fatty acyl chains with relative intensities and linewidths characteristic of pure CE, by comparison with lipid standards. Regions judged to be lipid rich by MRI showed much more intense CE resonances than did lipid-poor regions. The integrated intensities of lipid peaks were 5.5 +/- 2.0% (lipid-rich regions) versus 0.9 +/- 0.6% (lipid-poor regions) of the unsuppressed water peak (P < 0.0001). Lipid distribution by histology, MRS, and MRI showed strong correlation. Image-guided proton MRS accurately identified CE in selected regions of atherosclerotic plaque as small as 1 mm3 in an ex vivo setting. This procedure may permit the noninvasive detection and quantification of CE in atherosclerotic plaque in vivo.

Haplotype Effect of the Matrix Metalloproteinase-1 Gene on Risk of Myocardial Infarction

Myocardial infarction (MI) is commonly caused by atherosclerotic plaque rupture following excessive degradation of collagen fibers in the atherosclerotic lesion. We investigated whether interindividual variability in risk of MI was related to polymorphisms in the gene encoding matrix metalloproteinase (MMP)-1, a key fibrillar collagen–degrading enzyme. Several single nucleotide polymorphisms in the MMP1 gene promoter were identified following sequencing DNA samples from 30 individuals. An analysis of the polymorphisms in a cohort of British whites with coronary atherosclerosis, including 639 patients with MI and 538 non-MI subjects, revealed a haplotype effect of the −519A>G and −340T>C polymorphisms on risk of MI, with the A −519 -C −340 and G −519 -T −340 haplotypes being protective (odds ratio=0.70 [0.57 to 0.86]; P =0.0007), whereas the G −519 -C −340 haplotype increased MI risk (odds ratio=1.94 [1.15 to 3.28]; P =0.013). This finding was replicated in a subsequent analysis of 387 Swedish MI patients and 387 healthy controls (odds ratio=0.70 [0.55 to 0.89], P =0.003, for A −519 -C −340 and G −519 -T −340 ; odds ratio=1.54 [0.97 to 2.46], P =0.07, for G −519 -C −340 ). In vitro assays showed that compared with the A −519 -T −340 haplotype, the A −519 -C −340 and G −519 -T −340 haplotypes had lower promoter activity, whereas the G −519 -C −340 haplotype had greater promoter strength, in driving gene expression in human macrophages. Haplotype-specific differences in MMP1 mRNA level in atherosclerotic tissues were also detected. The data indicate that MMP1 gene variation is a genetic factor contributing to interindividual differences in MI risk.

The vulnerable carotid artery plaque: current imaging methods and new perspectives

BACKGROUND AND PURPOSE

Atherosclerosis is a diffuse, chronic inflammatory disorder that involves the vascular, metabolic, and immune systems and leads to plaque vulnerability. The traditional risk assessment relies on clinical, biological, and conventional imaging tools. However, these tools fall short in predicting near-future events in patients with vulnerable carotid artery plaque.

METHODS

In current clinical practice, anatomic imaging modalities, such as B-mode ultrasound, spiral computed tomography angiography, and high-resolution MRI, can identify several morphological features characteristic of the vulnerable plaque but give little or no information regarding molecular and cellular mechanisms.

RESULTS

This review is dedicated to factors involved in carotid artery plaque vulnerability and to new imaging methods that target this condition. Our aim is to describe the following: (1) conventional pathologic and imaging markers predictive of plaque vulnerability; (2) the role of relevant biological, genetic, and mechanical factors; (3) the potential of new imaging methods; and (4) current and emerging treatments.

CONCLUSIONS

A multimodal assessment of plaque vulnerability involving the combination of systemic markers, new imaging methods that target inflammatory and thrombotic components, and the potential of emerging therapies may lead to a new stratification system for atherothrombotic risk and to a better prevention of atherothrombotic stroke.

Low-grade carotid stenosis: looking beyond the lumen with MRI

BACKGROUND AND PURPOSE

The management of carotid atherosclerosis is well-established for symptomatic stenosis above 69%, but the optimal approach for managing lower degrees of narrowing remains uncertain. Because the risk of stroke increases with higher grades of stenosis, we are inclined to consider low-grade disease to be low risk. This approach, however, does not take into account other factors such as plaque size or composition. Plaque may progress to a substantial size before it demonstrates significant stenosis by angiography. We know that low-grade disease can result in cerebrovascular ischemic events, but predicting vulnerable lesions has not been possible by relying on stenosis alone.

SUMMARY OF REVIEW

An understanding of the clinical behavior of plaque causing little to no narrowing is now possible with the advent of high-resolution black blood MRI, a modality that does not rely on luminal narrowing for detection.

CONCLUSIONS

We present the current understanding of the clinical implications of low-grade carotid stenosis with an example of the MRI assessment of high-risk carotid plaque causing minimal narrowing that highlights the importance of looking beyond the lumen.

99mTc-interleukin-2 scintigraphy for the in vivo imaging of vulnerable atherosclerotic plaques

PURPOSE

Several histopathological studies have demonstrated that vulnerable plaques are enriched in inflammatory cells. The aims of this study were: (1a) to test the ability of 99mTc-labelled interleukin-2 (99mTc-IL2) to bind to IL2R-positive (IL2R+) cells in carotid plaques and (1b) to correlate the plaque uptake of 99mTc-IL2, measured in vivo, with the number of IL2R+ cells within the plaque, measured ex vivo by histology (transversal study, TS), and (2) to evaluate changes in 99mTc-IL2 uptake in plaques, before and after treatment with a statin or a hypocholesterolaemic diet (longitudinal study, LS).

METHODS

Ultrasound scan was performed for plaque characterisation and localisation. Fourteen patients (16 plaques) eligible for endoarterectomy were recruited for the TS and underwent 99mTc-IL2 scintigraphy before surgery. Nine patients (13 plaques) were recruited for the LS; these patients received atorvastatin or a standard hypocholesterolaemic diet and 99mTc-IL2 scintigraphy was performed before and after 3 months of treatment.

RESULTS

The degree of 99mTc-IL2 uptake was expressed as the plaque/background (T/B) ratio. In patients from TS, T/B ratios correlated with the percentage of IL2R+ cells at histology (r = 0.707; p = 0.002) and the number of IL2R+ cells at flow cytometry (r = 0.711; p = 0.006). No correlations were observed between ultrasound scores and either scintigraphic or histological findings. In patients from the LS, the mean 99mTc-IL2 uptake decreased in statin-treated patients (1.75+/-0.50 vs 2.16+/-0.44; p = 0.012), while it was unchanged in the patients on the hypocholesterolaemic diet (2.33+/-0.45 vs 2.34+/-0.5).

CONCLUSION

99mTc-IL2 accumulates in vulnerable carotid plaques; this accumulation is correlated with the amount of IL2R+ cells and is influenced by lipid-lowering treatment with a statin.

Carotid plaque composition in stable and unstable coronary artery disease

BACKGROUND

Several pieces of evidence suggest that formation of complex atheromatous plaques may be influenced not only by local but also by systemic factors.

METHODS

Twenty-five patients (16 men/9 women, age 63 +/- 10 years) with stable coronary artery disease (sCAD) and 61 (41 men/20 women, age 66 +/- 16 years) with acute coronary syndromes (ACSs) underwent carotid ultrasonography within 2 days of cardiac catheterization. Complex coronary plaques were associated with intraluminal filling defect consistent with thrombus, ulceration, or irregularity. Complex carotid plaques had one or more of the following features: (a) ulceration, (b) irregular surface, (c) mobile thrombi on plaque surface, (d) predominant echolucency, and (e) heterogeneity with intraplaque echolucent areas.

RESULTS

Carotid intimamedia thickness and luminal diameter were not significantly different between patients with sCAD and those with ACS (0.95 +/- 0.22 vs 1.0 +/- 0.15 mm [P = .23] and 6.1 +/- 0.89 vs 6.20 +/- 0.77 mm [P = .60], respectively), whereas the interadventitial diameter was slightly greater in the latter (7.93 +/- 1.05 vs 8.40 +/- 0.97 mm, P = .0496). Both complex coronary plaques and complex carotid plaques were more common in patients with ACS than in those with sCAD (n = 52 [85.2%] vs n = 6 [24%] [P < .0001] and n = 38 [62.3%] vs n = 5 [20%] [P = .0009], respectively). The odds of having complex carotid plaques were increased > 6-fold in patients with ACS compared with those with sCAD (OR 6.61, 95% CI 2.24-19.32).

CONCLUSIONS

Complex coronary plaques are associated with complex carotid plaques and the high prevalence of both plaque types in patients with ACS is indicative of a systemic process contributing to complex plaque formation and instability.

Identification of four gene variants associated with myocardial infarction

Family history is a major risk factor for myocardial infarction (MI). However, known gene variants associated with MI cannot fully explain the genetic component of MI risk. We hypothesized that a gene-centric association study that was not limited to candidate genes could identify novel genetic associations with MI. We studied 11,053 single-nucleotide polymorphisms (SNPs) in 6,891 genes, focusing on SNPs that could influence gene function to increase the likelihood of identifying disease-causing gene variants. To minimize false-positive associations generated by multiple testing, two studies were used to identify a limited number of nominally associated SNPs; a third study tested the hypotheses that these SNPs are associated with MI. In the initial study (of 340 cases and 346 controls), 637 SNPs were associated with MI (P<.05); these were evaluated in a second study (of 445 cases and 606 controls), and 31 of the 637 SNPs were associated with MI (P<.05) and had the same risk allele as in the first study. For each of these 31 SNPs, we tested the hypothesis that it is associated with MI, using a third study (of 560 cases and 891 controls). We found that four of these gene variants were associated with MI (P<.05; false-discovery rate <10%) and had the same risk allele as in the first two studies. These gene variants encode the cytoskeletal protein palladin (KIAA0992 [odds ratio (OR) 1.40]), a tyrosine kinase (ROS1 [OR 1.75]), and two G protein-coupled receptors (TAS2R50 [OR 1.58] and OR13G1 [OR 1.40]); all ORs are for carriers of two versus zero risk alleles. These findings could lead to a better understanding of MI pathophysiology and improved patient risk assessment.

Early time to benefit with intensive statin treatment: could it be the pleiotropic effects?

Acute coronary syndrome (ACS) is associated with a number of abnormalities in inflammation, endothelial function, and coagulation, all of which appear to be modulated by statins. We examined the time to benefit of different statin regimens in the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis in Myocardial Infarction 22 (PROVE IT-TIMI 22) trial and other ACS trials that compared statin therapies in patients with ACS. In PROVE IT-TIMI 22, apparent clinical benefit was observed as early as 30 days, with significant reduction in all-cause mortality, myocardial infarction, unstable angina requiring rehospitalization, revascularization performed 30 days postrandomization, or stroke observed as early as 4 months. In PROVE IT-TIMI 22, atorvastatin 80 mg lowered both low-density lipoprotein (LDL) cholesterol and C-reactive protein (CRP) at 30 days and 4 months to a greater extent than pravastatin 40 mg. Those who achieved the lowest LDL and the lowest CRP levels at 30 days after ACS had the lowest risk of acute cardiac events. The very early benefits of statin therapy appeared to be correlated with CRP reductions, which may relate to the intensity of the pleiotropic effects of statins.

Contribution of an imbalance between oxidant—antioxidant systems to plaque vulnerability in patients with carotid artery stenosis

OBJECT

Reactive species of oxygen and nitrogen mediate the oxidative modification of low-density lipoprotein (LDL). Oxidation of LDL is inhibited by endogenous radical scavenging enzymes such as manganese superoxide dismutase (SOD) and Cu-ZnSOD that catalyze dismutation of oxygen to H2O2. Low-molecular antioxidants such as uric acid regulate the inactivation that appears to be linked to an increase in peroxynitrite resulting in oxidized LDL (OxLDL) elevation. The authors evaluated whether a focal imbalance between pro- and antioxidant systems induces plaque vulnerability in patients with carotid artery (CA) stenosis.

METHODS

Carotid artery plaques obtained in 35 patients who had undergone carotid endarterectomy were classified as vulnerable or stable based on histopathological findings. In vulnerable plaques, OxLDL, measured using enzyme-linked immunosorbent assay, was significantly higher (p < 0.01) and SOD activity significantly lower than in stable plaques (p < 0.05). The plaque and plasma OxLDL levels were inversely correlated with plaque SOD activity (p < 0.01). The physiological uric acid level in all plaques was one fourth to one eighth of that in plasma and appeared to be unable to protect Cu-ZnSOD from degradation by H2O2. Immunohistochemical analysis showed increased peroxynitrite and OxLDL in vulnerable plaques. There was a significant correlation between plaque and plasma OxLDL levels (p < 0.01).

CONCLUSIONS

Analysis of the results suggests that a focal imbalance between pro- and antioxidant defense systems in patients with CA plaques induces an increase in plaque OxLDL levels and consequent plaque instability, contributing to high levels of plasma OxLDL.

Non-invasive coronary angiography with multi-detector computed tomography: comparison to conventional X-ray angiography

Selective coronary angiography introduced clinical coronary imaging in the late 1950s. The angiographic identification of high-grade coronary lesions in patients with acute and chronic symptomatic coronary artery disease (CAD) led to the development of surgical and percutaneous coronary revascularization. However, the fact that CAD remains the major cause of death in North America and Europe demonstrates the need for novel, complementary diagnostic strategies. These are driven by the need to characterize both increasingly advanced disease stages but also early, asymptomatic disease development. Complex revascularization techniques for patients with advanced disease stages will initiate a growing demand for 3-dimensional coronary imaging and integration of imaging modalities with new mechanical therapeutic devices. An emerging focus is atherosclerosis imaging with the goal to identify subclinical disease stages as the basis for pharmacological intervention aimed at disease stabilization or reversal. Non-invasive coronary imaging with coronary multidetector computed tomographic angiography (MDCTA) allows both assessment of luminal stenosis and subclinical disease of the arterial wall. Its complementary role in the assessment of early and advanced stages of CAD is increasingly recognized.

The site of plaque rupture in native coronary arteries: a three-vessel intravascular ultrasound analysis

OBJECTIVES

We evaluated the axial location of plaque ruptures in native coronary arteries.

BACKGROUND

It is clinically important to understand the potential sites of plaque rupture.

METHODS

We performed three-vessel intravascular ultrasound (IVUS) examination in 392 patients; 231 had acute coronary syndrome (ACS) and 161 had stable angina pectoris (SAP). The IVUS detected plaque ruptures in 206 patients: 158 ACS patients and 48 SAP patients. The distance between each coronary plaque rupture segment and the respective coronary ostium was measured with motorized IVUS transducer pullback in all three coronary arteries.

RESULTS

There were a total of 273 plaque ruptures in these 206 patients; 143 in the left anterior descending artery (LAD), 40 in the left circumflex artery (LCX), and 90 in the right coronary artery (RCA). There were 67 plaque ruptures in SAP patients and 206 in ACS patients; there were 197 culprit/target lesion plaque ruptures and 76 non-culprit/non-target lesion plaque ruptures. The LAD plaque ruptures were predominantly located between 10 and 40 mm from the LAD ostium (83%, 119 of 143). The LCX plaque ruptures were evenly distributed in the entire LCX tree. Most RCA plaque ruptures were located in segments between 10 and 40 mm (48%, 43 of 90) and in segments >70 mm from the ostium (32%, 29 of 90).

CONCLUSIONS

Three-vessel IVUS imaging showed that plaque ruptures occurred mainly in proximal segments of the LAD (83% of LAD plaque rupture), the proximal and distal segments of the RCA (48% and 32% of RCA plaque ruptures, respectively), and the entire LCX.

Lipoprotein Retention—and Clues for Atheroma Regression

Subendothelial retention of apoB-lipoproteins is the key initiating event in atherosclerosis, provoking a cascade of pathogenic responses. Dissection of the molecular participants provides fresh insight into how this major killer might be reversed. Efflux of harmful lipids derived from retained lipoproteins may be crucial in promoting beneficial remodeling of lesions.

In vivo detection of macrophages in a rabbit atherosclerotic model by time-resolved laser-induced fluorescence spectroscopy

Accumulation of numerous macrophages in the fibrous cap is a key identifying feature of plaque inflammation and vulnerability. This study investigates the use of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as a potential tool for detection of macrophage foam cells in the intima of atherosclerotic plaques. Experiments were conducted in vivo on 14 New Zealand rabbits (6 control, 8 hypercholesterolemic) following aortotomy to expose the intimal luminal surface of the aorta. Tissue autofluorescence was induced with a nitrogen pulse laser (337 nm, 1 ns). Lesions were histologically classified by the percent of collagen or macrophage foam cells as well as thickness of the intima. Using parameters derived from the time-resolved fluorescence emission of plaques, we determined that intima rich in macrophage foam cells can be distinguished from intima rich in collagen with high sensitivity (>85%) and specificity (>95%). This study demonstrates, for the first time, that a time-resolved fluorescence-based technique can differentiate and demark macrophage content versus collagen content in vivo. Our results suggest that TR-LIFS technique can be used in clinical applications for identification of inflammatory cells important in plaque formation and rupture.

Vulnerable Plaque Imaging

The concept of vulnerable plaque is well established with increasing evidence from clinical and basic research. The paradigm has shifted from focusing exclusively on the hemodynamic effects of plaque (ie, resulting lumenal stenosis alone as a predictor of stroke risk) to assessment of the structure and composition of plaque (eg, denuded endothelium with inflammatory elements as a nidus for platelet-fibrin clumping). It is increasingly evident that methods to detect and characterize vulnerable plaque must be developed and optimized. Although MR imaging, CT, and ultrasound provide data regarding single lesions, future investigations relying heavily on nuclear medicine techniques may offer functional assessment of the entire cardiovascular system.

Rationale and methods of the integrated biomarker and imaging study (IBIS): combining invasive and non-invasive imaging with biomarkers to detect subclinical atherosclerosis and assess coronary lesion biology

Death or myocardial infarction, the most serious clinical consequences of atherosclerosis, often result from plaque rupture at non-flow limiting lesions. Current diagnostic imaging with coronary angiography only detects large plaques that already impinge on the lumen and cannot accurately identify those that have a propensity to cause unheralded events. Accurate evaluation of the composition or of the biomechanical characteristics of plaques with invasive or non-invasive methods, alone or in conjunction with assessment of circulating biomarkers, could help identify high-risk patients, thus providing the rationale for aggressive treatments in order to reduce future clinical events. The IBIS (Integrated Biomarker and Imaging Study) study is a prospective, single-center, non-randomized, observational study conducted in Rotterdam. The aim of the IBIS study is to evaluate both invasive (quantitative coronary angiography, intravascular ultrasound (IVUS) and palpography) and non-invasive (multislice spiral computed tomography) imaging techniques to characterize non-flow limiting coronary lesions. In addition, multiple classical and novel biomarkers will be measured and their levels correlated with the results of the different imaging techniques. A minimum of 85 patients up to a maximum of 120 patients will be included. This paper describes the study protocol and methodological solutions that have been devised for the purpose of comparisons among several imaging modalities. It outlines the analyses that will be performed to compare invasive and non-invasive imaging techniques in conjunction with multiple biomarkers to characterize non-flow limiting subclinical coronary lesions.

Plasma levels of oxidized-low-density lipoproteins are higher in patients with unstable angina and correlated with angiographic coronary complex plaques

OBJECTIVES

To measure circulating levels of oxidized-low-density lipoproteins (ox-LDL) in patients with stable and unstable angina and controls, and to investigate their correlation with the extent of coronary artery disease (CAD) and the presence of complex plaques at coronary angiography.

METHODS AND RESULTS

Circulating ox-LDL were assessed, using ELISA, in patients with unstable angina (UA, n=26), stable angina (SA, n=29) and in controls (C, n=27). All patients underwent coronary angiography. The extent of CAD was evaluated using a quantitative score, while the presence of complex, vulnerable plaques was angiographically assessed. Ox-LDL were higher in UA patients than in SA patients and in C subjects, and in SA patients than in C subjects (C, 45.6+/-12.8 U/L; SA, 58.8+/-11.0 U/L; UA, 73.7+/-13.6 U/L; p<0.001). No correlation was found with the extent of atherosclerotic disease in the coronary tree. Patients with angiographic complex lesions showed significantly higher levels of ox-LDL (68.4+/-13.9 U/L versus 55.2+/-16.4 U/L, p<0.001). Multiple regression analysis showed that ox-LDL were independent predictors of the presence of complex plaques (p<0.023).

CONCLUSIONS

Ox-LDL levels are higher in unstable patients and correlate with the presence of angiographically documented complex plaques. Ox-LDL might be markers of destabilization of CAD.

Cumulative incidence of coronary lesions with vulnerable characteristics in patients with stable angina pectoris: an intravascular ultrasound and angiographic study

BACKGROUND

Development of vulnerable lesion may take place simultaneously at many sites of coronary vasculature, therefore causing multisite instability. The prevalence of the phenomenon in stable angina (SA) patients remains unknown. The aim of our study was to assess, in patients with stable angina, the prevalence of coronary plaques with vulnerable characteristics and to ascertain whether the number of such lesions may accumulate.

METHODS

Vulnerable plaques are characterised by positive remodelling on intravascular ultrasound (IVUS) and with complex appearance on angiography. We performed preprocedural IVUS in target lesion of 67 patients with SA (46 males, age 55.9). Remodelling index (RI) defined as vessel area at the target lesion divided by that of average reference segments > or = 1.05 was assumed as positive remodelling. Plaques of > or = 30% stenosis on angiography were classified into complex or smooth groups.

RESULTS

Positive remodelling was found in 30 (44.8%) and complex plaque in 16 (23.9%) of 67 target lesions. Multiple complex plaques were present in 21 (31.3%) patients. Plaques with positive remodelling more often were complex on angiography (12/30 vs. 4/37, respectively; p=0.005) and were more often associated by complex plaques at other sites (35/30 vs. 23/37; p=0.04) than the remaining lesions. Moreover, the presence of positive remodelling predicted multiple complex lesions at other sites (OR 5.6; 95% CI 1.7-18.3).

CONCLUSION

Multiple coronary plaques with vulnerable characteristics are present in nearly one third of patients with stable angina. Incidence of vulnerable lesions may have cumulative character, i.e. the presence of one vulnerable lesion predicts occurrence of further vulnerable plaques.

Perioperative myocardial infarction—aetiology and prevention

Perioperative myocardial infarction (PMI) is one of the most important predictors of short- and long-term morbidity and mortality associated with non-cardiac surgery. Prevention of a PMI is thus a prerequisite for an improvement in overall postoperative outcome. The aetiology of PMI is multifactorial. The perioperative period induces large, unpredictable and unphysiological alterations in coronary plaque morphology, function and progression, and may trigger a mismatch of myocardial oxygen supply and demand. With many diverse factors involved, it is unlikely that one single intervention will successfully improve cardiac outcome following non-cardiac surgery. A multifactorial, step-wise approach is indicated. Based on increasing knowledge of the nature of atherosclerotic coronary artery disease, and in view of the poor positive predictive value of non-invasive cardiac stress tests, and the considerable risk of coronary angiography and coronary revascularization in high-risk patients, the paradigm is shifting from an emphasis on extensive non-invasive preoperative risk stratification to a combination of selective non-invasive testing and aggressive pharmacological perioperative therapy. Perioperative plaque stabilization by pharmacological means may be as important in the prevention of PMI as an increase in myocardial oxygen supply or a reduction in myocardial oxygen demand.

Inflammation and coronary artery disease

Inflammation is now recognized as being pivotal in the pathogenesis of atherosclerosis. This review highlights key concepts in our current understanding of the role of inflammation in the initiation, progression, and complication of atherosclerosis. The role of various triggers and amplifiers and the innate and adaptive immunity in the cascade of inflammatory events are also presented. Progress in our understanding of the inflammatory pathways in atherosclerosis has provided further mechanistic insight into the clinical benefits of current medical therapy and may alter our future treatment and preventive strategies.

Prognostic Impact of Fibrinogen in Carotid Atherosclerosis

Background— Fibrinogen is a key factor in the coagulation cascade, it exhibits proinflammatory properties, and it is suggested to play a pivotal role in atherogenesis. We investigated whether fibrinogen predicts future progression of carotid atherosclerosis, analyzing whether fibrinogen levels add to the prognostic information of other inflammatory parameters.

Methods— We prospectively studied 1268 consecutive patients without recent (12 months) symptoms from cerebrovascular disease. Patients underwent serial ultrasound investigations in 6- to 9-month intervals, categorizing carotid arteries as 0% to 29%, 30% to 49%, 50% to 69%, 70% to 89%, or 90% to 99% stenosed, or occluded. Fibrinogen levels were determined at baseline and follow-up. The risk for progressive carotid atherosclerosis according to fibrinogen levels was calculated, adjusting for traditional risk factors and other inflammatory parameters (C-reactive protein and serum amyloid A).

Results— Progression of carotid atherosclerosis was found in 117 of 1268 patients (9.2%) after a median of 8 months (range 6 to 18). Adjusted hazard ratios for atherosclerosis progression with increasing quartiles of baseline fibrinogen were 1.83 ( P =0.037), 2.09 ( P =0.008), and 2.45 ( P =0.002), respectively, compared with the lowest quartile. Fibrinogen at follow-up also was associated with progressive disease ( P =0.004). However, additionally adjusting for other inflammatory parameters diminished these associations to a nonsignificant level.

Conclusion— Elevated fibrinogen, reflecting the level of inflammatory activity, is associated with progression of carotid atherosclerosis, as it was demonstrated previously for other inflammatory parameters. However, this association seems to be nonspecifically related to the extent of the inflammatory process in atherosclerotic disease rather than to specific properties of fibrinogen.

Association between plasma lipids, and apolipoproteins and coronary artery disease: a cross-sectional study in a low-risk Korean population

BACKGROUND

Due to the lower level of the traditional lipid profiles in Koreans than in the series of patients from the western countries, the need to investigate other lipid parameters to help identify the individuals at high risk of CAD has been emphasized.

AIM AND METHODS

To investigate whether apolipoprotein B (apo B), apolipoprotein A-I (apo A-I) and their ratio give additional information to the traditional lipid risk factors for discriminating the individuals at high-risk for coronary artery disease (CAD), 544 subjects, who met the lipid criteria of total cholesterol (TC) <230 mg/dl, low-density lipoprotein cholesterol (LDL-C) <120 mg/dl and high-density lipoprotein cholesterol (HDL-C) >40 mg/dl were recruited. Patients were considered to be CAD(+) if they had > or =50% stenosis in at least one coronary artery.

RESULTS

In men, TC and apo B/apo A-I ratio were significantly different between groups with and without CAD after adjusting for age and diabetes (P = 0.037 and 0.035), and in women, triglyceride (TG), HDL-C and apo B/apo A-I ratio were significantly different after adjusting for age, diabetes and smoking status (P = 0.006, 0.007 and 0.030, respectively). In the lowest quartile of TC, TG and LDL-C, and the highest quartile of HDL-C, only apo B/apo A-I ratio was associated with CAD in both men and women. The only variable showing a significant difference between patients with and without CAD was apo B/apo A-I ratio. In models assessing whether apolipoproteins give additional information to traditional lipid risk factors, HDL-C, LDL-C, apo B/apo A-I ratio and in women but not in men, TG and apo B were all independent markers for the presence of CAD. Among the nontraditional lipid factors, only apo B/apo A-I ratio showed its additional value for identifying the presence of CAD.

CONCLUSION

Apo B/apo A-I ratio is the only variable that differentiates the patients with CAD from those without and, furthermore, gives additional information to that supplied by traditional lipid risk factors in a low-risk Korean population.

Atheroma stabilizing effects of simvastatin due to depression of macrophages or lipid accumulation in the atheromatous plaques of coronary plaque-prone WHHL rabbits

Clinical studies showed that both hydrophilic and lipophilic statins reduce coronary events although in vitro studies demonstrated that lipophilic statins inhibited proliferation of arterial smooth muscle cells. Therefore, we examined whether lipophilic simvastatin reduces smooth muscle cells in atheromatous plaque and how simvastatin affects stability of atheroma in vivo. Coronary atherosclerosis-prone WHHLCA rabbits aged 10 months were given simvastatin (15 mg/kg) orally for 52 weeks and examined the serum lipid levels, plasma drug concentration, and aortic and coronary atherosclerosis. Compared to the placebo group, the plasma cholesterol levels decreased by about 20%. In the simvastatin group, the lipid component (macrophages+extracellular lipids) was decreased in the coronary and aortic atheroma, despite no decrease in the fibromuscular components. Consequently, the frequency of vulnerable plaque decreased. In the coronary plaque of the simvastatin group, PCNA-positive cells (which appeared to be macrophages) of the plaques decreased but the TUNEL-positive cells did not show significant change. Finally, fully differentiated smooth muscle cells increased in the aortic lesions of the simvastatin group. In conclusion, our results suggest that simvastatin did not depress the fibromuscular components in atheromatous plaques and the plaque-stabilizing effects were due to the reduction of macrophages/lipid deposits.

Ultrasound measurement of the fibrous cap in symptomatic and asymptomatic atheromatous carotid plaques

BACKGROUND

Fibrous cap thickness (FCT) is an important determinant of atheroma stability. We evaluated the feasibility and potential clinical implications of measuring the FCT of internal carotid artery plaques with a new ultrasound system based on boundary detection by dynamic programming.

METHODS AND RESULTS

We assessed agreement between ultrasound-obtained FCT values and those measured histologically in 20 patients (symptomatic [S]=9, asymptomatic [AS]=11) who underwent carotid endarterectomy for stenosing (>70%) carotid atheromas. We subsequently measured in vivo the FCT of 58 stenosing internal carotid artery plaques (S=22, AS=36) in 54 patients. The accuracy in discriminating symptomatic from asymptomatic plaques was assessed by receiver operating characteristic curves for the minimal, mean, and maximal FCT. Decision FCT thresholds that provided the best correct classification rates were identified. Agreement between ultrasound and histology was excellent, and interobserver variability was small. Ultrasound showed that symptomatic atheromas had thinner fibrous caps (S versus AS, median [95% CI]: minimal FCT=0.42 [0.34 to 0.48] versus 0.50 [0.44 to 0.53] mm, P=0.024; mean FCT=0.58 [0.52 to 0.63] versus 0.79 [0.69 to 0.85] mm, P<0.0001; maximal FCT=0.73 [0.66 to 0.92] versus 1.04 [0.94 to 1.20] mm, P<0.0001). Mean FCT measurement demonstrated the best discriminatory accuracy (area under the curve [95% CI]: minimal 0.74 [0.61 to 0.87]; mean 0.88 [0.79 to 0.97]; maximal 0.82 [0.71 to 0.93]). The decision threshold of 0.65 mm (mean FTC) demonstrated the best correct classification rate (82.8%; positive predictive value 75%, negative predictive value 88.2%).

CONCLUSIONS

FCT measurement of carotid atheroma with ultrasound is feasible. Discrimination of symptomatic from asymptomatic plaques with mean FCT values is good. Prospective studies should determine whether this ultrasound marker is reliable.

Cardiovascular effects of fine and ultrafine particles

Epidemiological studies of the past decades have provided a strong body of evidence that elevated levels of ambient particulate air pollution (PM) are associated with increased cardiovascular and respiratory morbidity and mortality. Exacerbations of ischemic and/or arrhythmic cardiac diseases have been linked to PM exposure. At a workshop held at the GSF- National Center for Environment and Health in November 2003, relevant epidemiological and toxicological data of the past 5 years were compiled and potential biological pathways discussed. Available clinical and experimental evidence lends support to the following mechanisms mediating cardiovascular effects of inhaled ambient particles: (i) pulmonary and/or systemic inflammatory responses inducing endothelial dysfunction, a pro-coagulatory state and promotion of atherosclerotic lesions, (ii) dysfunction of the autonomic nervous system in response to direct reflexes from receptors in the lungs and/or to local or systemic inflammatory stimuli, and (iii) cardiac malfunction due to ischemic responses in the myocardium and/or altered ion-channel functions in myocardial cells. While an increasing number of studies addressing these questions support the notion that PM exposure is associated with cardiovascular effects, these studies at present provide only a fragmentary and at times inconclusive picture of the complex biological pathways involved. The available data are consistent with the occurrence of a systemic inflammatory response and an alteration of autonomic cardiac control, but evidence on endothelial dysfunction, pro-coagulatory states, and PM-related myocardial malfunction is as yet scarce. Further studies are therefore needed to substantiate our current understanding of the pathophysiological links between PM exposure and adverse cardiovascular outcomes.

Inflammation and Carotid Artery—Risk for Atherosclerosis Study (ICARAS)

Background— Compelling evidence suggests that inflammation is fundamentally involved in the pathogenesis of atherosclerosis; however, temporal correlation between inflammation and morphological features of atherosclerosis progression has not been demonstrated unequivocally.

Methods and Results— We prospectively studied 1268 consecutive patients who were initially asymptomatic with respect to carotid artery disease. Patients underwent serial carotid ultrasound investigations at baseline and after a follow-up interval of a median of 7.5 months (range 6 to 9 months), with measurement of carotid flow velocities and categorization of carotid arteries as 0% to 29%, 30% to 49%, 50% to 69%, 70% to 89%, or 90% to 99% stenosed or occluded. High-sensitivity C-reactive protein (hs-CRP) and serum amyloid A (SAA) were measured at baseline and follow-up. Progression of carotid atherosclerosis was found in 103 (8.1%) of 1268 patients. Hs-CRP and SAA, respectively, at baseline ( P =0.004 and P =0.014) and follow-up ( P <0.001 and P <0.001) and the change from baseline to follow-up ( P <0.001 and P <0.001) were significantly associated with progressive atherosclerosis. Adjusted ORs (95% CI) for atherosclerosis progression with increasing quintiles of baseline hs-CRP were 1.65 (0.71 to 3.84), 1.87 (0.8 to 4.37), 3.32 (1.49 to 7.39), and 3.65 (1.65 to 8.08), and with increasing quintiles of baseline SAA, they were 0.86 (0.38 to 1.92), 0.99 (0.49 to 1.99), 1.72 (0.91 to 3.28), and 2.28 (1.24 to 4.20), respectively, compared with the lowest quintiles.

Conclusions— These findings supply evidence for a close temporal correlation between inflammation and morphological features of rapidly progressive carotid atherosclerosis, which suggests that elevation or increase of the inflammatory biomarkers hs-CRP and SAA identifies the presence of active atherosclerotic disease.

The role of immune system parameters in the relationship between depression and coronary artery disease

The relationship between depressive symptoms and coronary artery disease (CAD) is mediated in part by immune system parameters. This review describes research on the psychoneuroimmunological pathways accounting for the association between depression and CAD, and addresses conceptual and methodological issues. Relationships between central nervous system correlates of depression and immune system parameters are bidirectional and are mediated via neurohormonal and parasympathetic pathways. Evidence suggests that these associations can be affected by a) the clinical characteristics of depression (e.g., typical depression versus atypical depression and exhaustion), b) the duration and severity of depressive symptoms, and c) the stage of underlying CAD. Depressive symptoms are hypothesized to affect primarily the transition from stable CAD to acute coronary syndromes via plaque activation and prothrombotic processes, and may play an additional role in the response to injury at early stages of coronary atherosclerosis.

Preoperative Cardiac Evaluation: Mechanisms, Assessment, and Reduction of Risk

The changing paradigm in cardiovascular disease in which atherosclerotic lesions exist in a spectrum of stable to unstable, the lack of a perfect prediction tool, and the paucity of randomized controlled data on appropriate intervention make protection of cardiac patients undergoing thoracic surgery challenging. Nociception-related sympathetic drive combines with inflammatory stimuli and the cardiodepressant effects of anesthesia to create a window of maximum risk in the early postoperative period (8-24 hours), and although multivariate models have shown that a combination of surgery-specific risk, patient-specific cardiovascular history, and estimated functional capacity best determine the need for further investigation, the optimal choice of investigation is unclear. Exercise or dobutamine stress echocardiography provide the best validated investigations, and in the case of poor images, dobutamine MR imaging is increasingly used. When disease is found, medical and interventional options are available. PCI is often used, but the risk of converting a stable flow-limiting lesion into a less stable non-flow-limiting lesion must be considered, along with a delay for anti-platelet therapy and endothelialization of the stent. Alternatively, medical protection with acute beta-blockade or alpha2-agonists reduces risk (although beta-blockade often is avoided in chronic lung disease, even nonselective agents are safe in patients with non-airways reactive COPD). In addition, it is likely that statin use reduces risk, probably by stabilizing plaques, but patients with cardiac risk are increasingly likely to be taking this medication already. The assessment and management of cardiac risk in the perioperative thoracic surgery patient is challenging. With focused, rational, and individually tailored management; tight monitoring of postoperative pain; and a close working relationship between the surgeon, anesthesiologist, and cardiologist, patient care can be optimized, and risk can be effectively controlled.

Identification of vulnerable atherosclerotic plaque using IVUS-based thermal strain imaging

Pathology and autopsy studies have demonstrated that sudden disruption of vulnerable atherosclerotic plaque is responsible for most acute coronary syndromes. These plaques are characterized by a lipid-rich core with abundant inflammatory cells and a thin fibrous cap. Thermal strain imaging (TSI) using intravascular ultrasound (IVUS) has been proposed for high-risk arterial plaque detection, in which image contrast results from the temperature dependence of sound speed. It has the potential to distinguish a lipid-laden lesion from the arterial vascular wall due to its strong contrast between water-bearing and lipid-bearing tissue. Initial simulations indicate plaque identification is possible for a 1 degrees C temperature rise. A phantom experiment using an IVUS imaging array further supports the concept, and results agree reasonably well with prediction.

Diffuse and Active Inflammation Occurs in Both Vulnerable and Stable Plaques of the Entire Coronary Tree

OBJECTIVES

This study was undertaken to define and compare geographic coronary artery inflammation in patients who were dying of acute myocardial infarction (AMI), chronic stable angina (SA), and noncardiac causes (CTRL).

BACKGROUND

Biochemical markers and flow cytometry provide indirect evidence of diffuse coronary inflammation in patients dying of acute coronary syndromes. Yet no histopathologic studies have corroborated these findings. A key unanswered question is whether the inflammatory burden involves the entire coronary tree or is limited to a few plaques.

METHODS

We examined 544 coronary artery segments from 16 patients with AMI, 109 segments from 5 patients with SA, and 304 coronary segments from 9 patients with CTRL.

RESULTS

An average of 6.8 +/- 0.5 vulnerable segments per patient were found in the AMI group (in addition to culprit lesions) compared with an average of 0.8 +/- 0.3 and 1.4 +/- 0.3 vulnerable lesions/patient in the SA and CTRL groups, respectively. The AMI group, independent of the type of plaque observed, showed significantly more inflammatory infiltrates compared with the SA and CTRL groups (121.6 +/- 12.4 cell x mm2 vs. 37.3 +/- 11.9 cell x mm2 vs. 26.6 +/- 6.8 cell x mm2, p = 0.0001). In AMI patients, active inflammation was not only evident within the culprit lesion and vulnerable plaques but also involved stable plaques. These showed a three- to four-fold higher inflammation than vulnerable and stable plaques from the SA and CTRL groups, respectively.

CONCLUSIONS

This histopathologic study found that both vulnerable and stable coronary plaques of patients dying of AMI are diffusely infiltrated by inflammatory cells.

Genes contributing to risk for common forms of stroke

The quest for disease genes that confer risk for stroke is now being undertaken using three complementary approaches. Positional cloning using rare Mendelian phenocopies of stroke has found genes that contribute to rare forms of stroke but, so far, not to the common forms of stroke. Candidate-gene case-control association studies using the common forms of stroke have found suggestive associations of modest effect. However, positional cloning using hundreds of Icelandic families affected by the common forms of stroke has recently found two genes conferring substantial risk for ischemic stroke that have apparently been confirmed in the USA and other European populations. Both genes encode enzymes, phosphodiesterase 4D (PDE4D) and arachidonate 5-lipoxygenase-activating protein (FLAP), which suggest novel treatment strategies for stroke prevention.

Stabilization of advanced atherosclerosis in low-density lipoprotein receptor-deficient mice by aspirin

COX-1-dependent eicosanoid formation accelerates atherogenesis, and low-dose aspirin reduces early atherosclerosis. However, the role of aspirin in modulating progression of vascular atherosclerotic lesions once established is less investigated. We wished to determine the effect of low-dose aspirin on vascular inflammation, plaque composition, and progression of established atherosclerosis. Low-density lipoprotein receptor-deficient mice (LDLR(-/-)) were fed a high-fat diet for 3 months. At this time, one group of mice underwent baseline analysis. Two additional groups, while continuing the high-fat diet, were randomized to receive placebo or aspirin for additional 3 months. At the end of the study, LDLR(-/-) mice that had received aspirin had suppressed biosynthesis of thromboxane B2, the major products of COX-1 activity, reduced monocyte chemoattractant protein-1, and soluble intercellular adhesion molecule-1 levels compared with controls. Compared with baseline, the placebo group had significant progression of atherosclerosis. In contrast, aspirin treated mice showed a significant reduction in progression of atherosclerosis, and a significant decrease in foam cell content. These results suggest that in murine atherosclerosis, low-dose aspirin retards progression of established and advanced vascular atherosclerotic lesions by suppressing the formation of bioactive lipids and vascular inflammation.

Detection of coronary plaque by computed tomography with a novel plaque analysis system, 'Plaque Map', and comparison with intravascular ultrasound and angioscopy

BACKGROUND

Previous reports suggest that plaque may be characterized by the computed tomography (CT) number, but there is not a comprehensive method for evaluating the gray-scale CT image of the coronary artery obtained by multi-detector row CT (MDCT).

METHODS AND RESULTS

Forty-five patients with acute coronary syndrome (ACS) underwent MDCT either 3-4 weeks after the onset of acute myocardial infarction (n=24) or within 1 week after percutaneous coronary intervention in patients with unstable angina (UA; n=21). The cross-sections obtained at intervals of 5 mm were converted to numerical data and a 'plaque map' was drawn using the color-based isometric line method and bird's eye view. 'Plaque map' was compared with the findings of intravascular ultrasound (IVUS) and angioscopy. Of 662 slices of 78 vessels, soft, intermediate or calcified plaque was detected in 144, 134, and 84 slices, respectively. Compared with IVUS, the sensitivities were 92%, 87%, and 89%, respectively, and compared with angioscopy, sensitivity was 80% and specificity was 87%.

CONCLUSIONS

MDCT with the 'Plaque Map' system can noninvasively characterize plaque in patients with ACS.

Hyperbaric oxygen therapy for acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS) includes acute myocardial infarction and unstable angina. ACS is common and may prove fatal. Hyperbaric oxygen therapy (HBOT) will improve oxygen supply to the threatened heart and may reduce the volume of heart muscle that will perish. The addition of HBOT to the standard treatment may reduce death rate and other major adverse outcomes.

OBJECTIVES

To assess the benefits and harms of adjunctive HBOT for treating ACS.

SEARCH STRATEGY

We searched the following from inception to November 2004: CENTRAL, MEDLINE, EMBASE, CINAHL, DORCTHIM, and references from selected articles. Relevant journals were handsearched and researchers in the field contacted.

SELECTION CRITERIA

Randomised studies comparing the effect on ACS of regimens that include HBOT with those that exclude HBOT.

DATA COLLECTION AND ANALYSIS

Three reviewers independently evaluated the quality of trials using the guidelines of the Cochrane Handbook and extracted data from included trials.

MAIN RESULTS

Four trials with 462 participants contributed to this review. There was a trend towards, but no significant decrease in, the risk of death with HBOT (relative risk (RR) 0.64, 95% CI 0.38 to 1.06, P=0.08). There was evidence from individual trials of reductions in the risk of major adverse coronary events [MACE] (RR 0.12, 95% CI 0.02 to 0.85, P=0.03; NNT 4, 95% CI 3 to 10) and some dysrhythmias following HBOT (RR 0.59, 95% CI 0.39 to 0.89, P=0.01; NNT 6, 95% CI 3 to 24), particularly complete heart block (RR 0.32, 95%CI 0.12 to 0.84, P=0.02), and that the time to relief of pain was reduced with HBOT (Weighted Mean Difference [WMD] 353 minutes shorter, 95% CI 219 to 488, P<0.0001). One trial suggested a significant incidence of claustrophobia in single occupancy chambers of 15% (RR of claustrophobia with HBOT 31.6, 95%CI 1.92 to 521, P=0.02).

AUTHORS' CONCLUSIONS

For people with ACS, individual small trials suggest the addition of HBOT reduced the risk of Major Adverse Cardiac Events, some dysrrhythmias, and reduced the time to relief from ischaemic pain, but did not reduce mortality. In view of the modest number of patients, methodological shortcomings and poor reporting, this result should be interpreted cautiously, and an appropriately powered trial of high methodological rigour is justified to define those patients (if any) who can be expected to derive most benefit from HBOT. The routine application of HBOT to these patients cannot be justified from this review.