The vulnerable plaque and acute coronary syndromes

Proteomics in Cardiovascular disease

This study focuses on recent advances in proteomics and provides an up-to-date use of this technology in identifying cardiovascular disease (CVD) biomarkers. A total of eight electronic databases (PubMed, EMBASE, Web of Science, Cochrane Library, Wanfang, Vip, Sinomed, and CNKI) were searched and five were used for integrative analysis of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic ratio (DOR) and 1 secondary indicator area under the curve (AUC). This systematic review and integrative analysis summarized potential biomarkers previously identified by proteomics. The integrative analysis suggested that proteomics technology had high clinical value in CVD diagnosis. The findings provided new possible directions for the prevention or diagnosis of CVD.

Potential of an Approach Based on the Identification and Treatment of Vulnerable Coronary Plaques

In this viewpoint paper, the authors are tackling criticism to the limits of invasive imaging modalities for identification and treatment of vulnerable plaques. They believe in the clinical usefulness of invasive imaging modalities for identification of vulnerable plaques, and are suggesting an explanation for the suboptimal results of past studies, that failed to demonstrate a correlation between interventional treatment of vulnerable plaques, and reduction of hard clinical endpoints. Vulnerability studies have been based, so far, on the detection and measurement of plaques lipid content, because of its ease. However, the search for lipid "lakes" as a single common causal feature of acute coronary syndromes does not seem sufficient to identify patients at risk of adverse events. New imaging studies provided the rationale for improving clinical outcomes, adopting a more comprehensive assessment of target plaque morphology. There is little rationale in pursuing a functional assessment of coronary lesions to predict myocardial infarction. Recent studies are further confirming this hypothesis, suggesting that the clinical benefit of the fractional flow reserve-guided strategy is simply due to a significant reduction in the rate of repeated revascularizations, with no significant differences in the incidence of hard endpoints. There is a need to develop new randomized studies, requiring a feasible number of patients, to test the superiority of an approach based on vulnerable plaque sealing and treatment.

Supplementation of Lipoic Acid, Zinc and Clopidogrel Reduces Mortality Rate and Incidence of Ventricular Arrhythmia in Experimental Myocardial Infarction

Despite the significant advances in management of coronary heart diseases, myocardial infarction (MI) is still associated with a high mortality rate. The present study was planned to investigate the possible protective effects of the anti-oxidants lipoic acid and zinc sulfate as well as the anti-platelet clopidogrel on cardiac dysfunction in experimental isoproterenol (ISO)-induced MI, aiming at achieving useful means for protection and therapy against MI. Wistar rats of both sexes were allocated into five groups: control, untreated MI and MI pre-treated with lipoic acid, zinc, or clopidogrel. All rats were subjected to ECG recording and measurement of plasma levels of troponin I, creatine kinase-MB (CK-MB) unit, triglycerides and total cholesterol. The hearts were isolated and studied on Langendorff preparation for assessment of intrinsic cardiac activities. The results revealed that the percent mortality was markedly reduced upon pre-treatment and the total arrhythmia was also decreased except for the zinc pre-treated rats. The ST-segment elevation was significantly reduced and the plasma levels of CK-MB were only decreased in lipoic acid and clopidogrel pre-treated rats with variable hypolipidemic effect. Hearts of clopidogrel pre-treated rats showed augmented inotropic activity both basal and in response to β-adrenergic stimulation. While zinc pre-treated hearts revealed improved rate of contraction and increased myocardial flow rate. Overall, these results indicate that lipoic acid, zinc and clopidogrel were variably effective in modifying the ISO-induced MI insults and offered partial protection against experimental myocardial damage.

Plasma calprotectin was associated with platelet activation and no-reflow phenomenon in acute coronary syndrome

Background

No-reflow occurs in 3–4% of all percutaneous coronary interventions (PCIs) and has a strong negative impact on clinical outcomes of acute coronary syndrome (ACS). Therefore, the discovery of a biomarker that can early predict the occurrence of no-reflow has great clinical significance. Multiple factors including platelet activation are relevant to no-reflow. Calprotectin is found to be a biomarker of plaque instability and is identified to be a novel diagnostic and prognostic biomarker of cardiovascular diseases. The association of plasma calprotectin with platelet activation and no-reflow phenomenon in ACS is not clear.

Methods

In this prospective study performed at Yantai Yuhuangding Hospital from 2017 to 2018, a total of 176 Chinese patients with ACS who had undergone PCIs were recruited consecutively, aged from 30 to 88 years. Angiographic no-reflow was defined as thrombolysis in myocardial infarction grade less than 3. Blood samples were collected immediately at admission for the detection of plasma calprotectin and platelet–monocyte aggregates formation. Statistical analysis was performed for the variable’s comparisons between groups and the prediction value of plasma calprotectin for no-reflow.

Results

The mean age of the 176 included ACS patients were 64(±11) years and acute ST-segment elevation myocardial infarction (STEMI) was present in 41.5% of patients. Twenty-two patients had no-reflow during the PCI procedures and the prevalence was 12.5%. Patients with higher plasma calprotectin had a higher level of platelet–monocyte aggregates (PMA) and a higher prevalence of no-reflow (p < 0.001). The multivariate regression showed that plasma calprotectin and admission hs-cTnI were independently associated with PMA, while plasma calprotectin and serum LDL-c were independent predictors of no-reflow (p < 0.001 and p = 0.017). AUC of calprotectin for predicting no-reflow were 0.898. The cut-off value of plasma calprotectin for no-reflow was 4748.77 ng/mL with a sensitivity of 0.95 and a specificity of 0.77.

Conclusion

Plasma calprotectin was associated with platelet activation and may act as an early predictive biomarker of no-reflow in patients with acute coronary syndrome.

COVID's Razor: RAS Imbalance, the Common Denominator Across Disparate, Unexpected Aspects of COVID-19

A modern iteration of Occam's Razor posits that "the simplest explanation is usually correct." Coronavirus Disease 2019 involves widespread organ damage and uneven mortality demographics, deemed unexpected from what was originally thought to be "a straightforward respiratory virus." The simplest explanation is that both the expected and unexpected aspects of COVID-19 share a common mechanism. Silent hypoxia, atypical acute respiratory distress syndrome (ARDS), stroke, olfactory loss, myocarditis, and increased mortality rates in the elderly, in men, in African-Americans, and in patients with obesity, diabetes, and cancer-all bear the fingerprints of the renin-angiotensin system (RAS) imbalance, suggesting that RAS is the common culprit. This article examines what RAS is and how it works, then from that baseline, the article presents the evidence suggesting RAS involvement in the disparate manifestations of COVID-19. Understanding the deeper workings of RAS helps one make sense of severe COVID-19. In addition, recognizing the role of RAS imbalance suggests potential routes to mitigate COVID-19 severity.

Relationship between serum homocysteine levels and long-term outcomes in patients with ST-segment elevation myocardial infarction

BACKGROUND

The mortality of cardiovascular disease is constantly rising, and novel biomarkers help us predict residual risk. This study aimed to evaluate the predictive value of serum homocysteine (HCY) levels on prognosis in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

The 419 consecutive patients with STEMI, treated at one medical center, from March 2010 to December 2015 were retrospectively investigated. Peripheral blood samples were obtained within 24 h of admission and HCY concentrations were measured using an enzymatic cycling assay. The patients were divided into high HCY level (H-HCY) and low HCY level (L-HCY) groups. Short- and long-term outcomes were compared, as were age-based subgroups (patients aged 60 years and younger vs. those older than 60 years). Statistical analyses were mainly conducted by Student t-test, Chi-squared test, logistic regression, and Cox proportional-hazards regression.

RESULTS

The H-HCY group had more males (84.6% vs. 75.4%, P = 0.018), and a lower prevalence of diabetes (20.2% vs. 35.5%, P < 0.001), compared with the L-HCY group. During hospitalization, there were seven mortalities in the L-HCY group and 10 in the H-HCY group (3.3% vs. 4.8%, P = 0.440). During the median follow-up period of 35.8 (26.9-46.1) months, 33 (16.2%) patients in the L-HCY group and 48 (24.2%) in the H-HCY group experienced major adverse cardiovascular and cerebrovascular events (MACCE) (P = 0.120). History of hypertension (hazard ratio [HR]: 1.881, 95% confidence interval [CI]: 1.178-3.005, P = 0.008) and higher Killip class (HR: 1.923, 95% CI: 1.419-2.607, P < 0.001), but not HCY levels (HR: 1.007, 95% CI: 0.987-1.027, P = 0.507), were significantly associated with long-term outcomes. However, the subgroup analysis indicated that in older patients, HCY levels were significantly associated with long-term outcomes (HR: 1.036, 95% CI: 1.011-1.062, P = 0.005).

CONCLUSION

Serum HCY levels did not independently predict in-hospital or long-term outcomes in patients with STEMI; however, among elderly patients with STEMI, this study revealed a risk profile for late outcomes that incorporated HCY level.

Qualitative evaluation of coronary atherosclerosis in a large cohort of young and middle-aged Dutch tissue donors implies that coronary thrombo-embolic manifestations are stochastic

Background and aims

With the intention to gain support for the hypothesis that incident ischemic complications of atherosclerotic disease involve a stochastic aspect, we performed a histological, qualitative evaluation of the epidemiology of coronary atherosclerotic disease in a cohort of aortic valve donors.

Patients and methods

Donors (n = 695, median age 54, range 11–65 years) were dichotomized into a non-cardiovascular (non-CVD) and a cardiovascular disease death (CVD) group. Consecutive 5 mm proximal left coronary artery segments were Movat stained, and the atherosclerotic burden for each segment was graded (revised AHA-classification).

Results

Non-CVD and CVD groups showed steep increase of atherosclerosis severity beyond the age of 40, resulting in an endemic presence of advanced atherosclerosis in men over 40 and women over 50 years. In fact, only 19% of the non-CVD and 6% of the CVD donors over 40 years were classified with a normal LCA or a so called non-progressive lesion type. Fibrous calcified plaques (FCP), the consolidated remnants of earlier ruptured lesions, dominated in both non-CVD and CVD donors. Estimates of the atherosclerosis burden (i.e. average lesion grade, proportion of FCPs, and average number of FCPs per cross-section) were all higher in the CVD group (p<1.10⁻¹⁶, p<0.0001, and p<0.05, respectively).

Conclusions

Dominance of consolidated FCP lesions in males over 40 and females over 50 years, show that plaque ruptures in the left coronary artery are common. However, the majority of these ruptures remain asymptomatic. This implies that the atherosclerotic process is repetitive. A relative difference in disease burden between CVD and non-CVD donors supports the concept that complications of atherosclerotic disease involve a stochastic element.

Markers of Thrombin Generation Are Associated With Long-Term Clinical Outcome in Patients With ST-Segment Elevation Myocardial Infarction

Hypercoagulability in ST-segment elevation myocardial infarction (STEMI) as related to long-term clinical outcome is not clarified. We aimed to investigate whether prothrombin fragment 1+2 (F1+2), d-dimer, and endogenous thrombin potential (ETP) measured in the acute phase of STEMI were associated with outcome. Blood samples were drawn median 24 hours after symptom onset in 987 patients with STEMI. Median follow-up time was 4.6 years. Primary outcome was a composite of all-cause mortality, reinfarction, stroke, unscheduled revascularization, or rehospitalization for heart failure; secondary outcome was total mortality. The number of combined end points/total mortality was 195/79. Higher levels of d-dimer and F1+2 were observed with both end points (all P < .005), whereas ETP was significantly lower (P < .01). Dichotomized at medians, increased risk was observed for levels above median for F1+2 and d-dimer (combined end point P = .020 and P = .010 and total mortality P < .001, both), while an inverse pattern was observed for ETP (P < .02, both). Adjusting for covariates, d-dimer was still associated with reduced risk of total mortality (P = .034) and receiver operating characteristic curve analyses showed area under the curve of 0.700 (95% confidence interval, 0.640-0.758). The hypercoagulable state in acute STEMI seems to be of importance for clinical outcome.

Development of an intravascular ultrasound elastography based on a dual-element transducer

The ability to measure the elastic properties of plaques and vessels would be useful in clinical diagnoses, particularly for detecting a vulnerable plaque. This study demonstrates the feasibility of the combination of intravascular ultrasound (IVUS) and acoustic radiation force elasticity imaging for detecting the distribution of stiffness within atherosclerotic arteries ex vivo. A dual-frequency IVUS transducer with two elements was used to induce the propagation of the shear wave (by the 8.5 MHz pushing element) which could be simultaneously monitored by the 31 MHz imaging element. The wave-amplitude image and the wave-velocity image were reconstructed by measuring the peak displacement and wave velocity of shear wave propagation, respectively. System performance was verified using gelatin phantoms. The phantom results demonstrate that the stiffness differences of shear modulus of 1.6 kPa can be distinguished through the wave-amplitude and wave-velocity images. The stiffness distributions of the atherosclerotic aorta from a rabbit were obtained, for which the values of peak displacement and the shear wave velocity were 3.7 ± 1.2 µm and 0.38 ± 0.19 m s^-1 for the lipid-rich plaques, and 1.0 ± 0.2 µm and 3.45 ± 0.45 m s^-1 for the arterial walls, respectively. These results indicate that IVUS elasticity imaging can be used to distinguish the elastic properties of plaques and vessels.

MRI, the technology for imaging of thrombi and inflammation

Atherosclerosis and its sequelae have a major impact on morbidity and mortality. The rupture of an inflamed atherosclerotic plaque is a crucial event, since it can result in acute thrombotic closure of an arterial vessel, resulting e. g. in myocardial infarction or stroke. Not only detection of early plaque rupture with imminent closure is therefore of clinical interest, but also timely detection of vascular inflammation and atherosclerotic plaque progression. However, plaque inflammation or even plaque rupture without vessel occlusion is not reliably detectable by current imaging techniques. Coronary angiography is the gold standard for evaluation of the coronary vessels, but only allows visualization of the vessel lumen without characterizing the important pathophysiology of the vessel wall. Therefore, highly inflamed and rupture prone plaques can be missed, or appear as a minor vessel narrowing. Although currently available techniques such as intravascular ultrasound or optical coherence tomography allow a further characterization of atherosclerotic plaques, it would be desirable to detect plaque inflammation, early plaque rupture or vascular thrombosis by non-invasive techniques such as magnetic resonance imaging (MRI), since they could allow early identification of patients at risk or triage of symptomatic patients.

In this manuscript, different strategies for detection of vascular inflammation, plaque-rupture and thrombosis by MRI will be discussed, with a special focus on molecular imaging contrast agents.

Prevention of Positive Coronary Artery Remodeling with Statin Therapy in Patients with Coronary Artery Diseases

Since positive coronary artery remodeling with large plaque burden is associated with subsequent coronary events, the authors tested their hypothesis that secondary prevention of coronary events by a statin may be associated with inhibition of the process of positive coronary artery remodeling in underlying coronary atherosclerotic lesions in patients with coronary artery diseases. They evaluated the intravascular ultrasound imaging in angiographically normal coronary lesions at baseline and after 6 months of therapy in 64 patients with coronary artery diseases. External elastic membrane area was defined as the vessel area, and the difference between the vessel and lumen area was calculated as plaque area. The relative echogenicity of coronary plaque to adventitia was evaluated as acoustic characteristics of coronary plaque. Twenty-five patients were treated with a statin and 39 patients did not receive a statin. In patients treated with a statin, plaque area decreased by 12% (p=0.013) compared to an increase in plaque area of 13% (p=0.023) in those who did not receive a statin. The vessel area was not enlarged in patients treated with a statin but did show positive remodeling in patients who had plaque progression without a statin. The relative echogenicity of plaque was unchanged in patients treated with a statin but significantly decreased in patients not receiving a statin. A statin may prevent positive coronary artery remodeling via inhibition of plaque progression in underlying coronary atherosclerotic lesions in patients with coronary artery diseases.

Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results

The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI-IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm(2), as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm(2) was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI-IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the experimental results reported herein can be applied in ARFI-IVUS imaging applications.

Relationship Between Cyclooxygenase-2 Inhibition and Thrombogenesis

Recently there has been considerable interest in the role of cyclooxygenase-2 (COX-2) in thrombosis and myocardial infarction. A large number of clinical and basic studies have focused on whether COX-2 inhibitors can induce a prothrombotic disorder and increase the risk of cardiovascular thrombosis. This article reviews (1) the roles of COX-2 in the metabolism of prostaglandins; (2) the influence of COX-2 inhibition in the platelet aggregation and the antithrombotic function of vascular endothelium; (3) the roles of COX-2 inhibition in atherothrombosis; and (4) clinical trials that examine COX-2 inhibition in relationship to the risk of myocardial infarction. Based on the published data, this review suggests that COX-2 plays varying and sometimes conflicting roles in thrombogenesis, in prostaglandins' metabolism of endothelium in healthy or dysfunctional conditions, and in atherothrombosis. Future investigations under different pathologic conditions are needed to fully understand the net effect of COX-2 inhibition on thrombogenesis. The roles of COX-2 in the pathophysiologic process of cardiovascular thrombosis are diverse and controversial, and need to be further studied to guide clinical practice.

Risks and benefits of triple oral anti-thrombotic therapies after acute coronary syndromes and percutaneous coronary intervention

The key pathophysiological process underlying symptomatic coronary artery disease, including acute coronary syndromes (ACS), is usually a rupture or an erosion of an atherosclerotic plaque, followed by platelet activation and subsequent thrombus formation. Early clinical trials showed benefit with long-term aspirin treatment, and later-based on large clinical trials-dual anti-platelet therapy (DAPT), initially with clopidogrel, and more recently with prasugrel or ticagrelor, has become the established treatment in the post-ACS setting and after percutaneous coronary intervention (PCI). Treatment with DAPT is recommended for both ST-elevation myocardial infarction and non-ST-elevation ACS, as well as after PCI with stenting, in American and European clinical guidelines. Notwithstanding the benefits observed with DAPT, including third-generation P2Y12 receptor inhibitors plus aspirin, ACS patients remain at high risk for a recurrent cardiovascular event, suggesting that other treatment strategies, including the addition of a third oral anti-platelet agent or a novel oral anticoagulant (NOAC) to standard DAPT regimens, may provide additional benefit for post-ACS patients and for patients undergoing PCI. Adding a third anti-thrombotic agent to DAPT after an ACS event or a PCI procedure has been shown to have modest benefit in terms of ischemic event reduction, but has consistently been associated with increased bleeding complications. Therefore, the quest to optimize anti-thrombotic therapies post-ACS and post-PCI continues unabated but is tempered by the historical experiences to date that indicate that careful patient and dose selection will be critical features of future randomized trials.

Markers of thrombin generation are associated with myocardial necrosis and left ventricular impairment in patients with ST-elevation myocardial infarction

Introduction

Platelet activation, thrombin generation and fibrin formation play important roles in intracoronary thrombus formation, which may lead to acute myocardial infarction.

We investigated whether the prothrombotic markers D-dimer, pro-thrombin fragment 1 + 2 (F1 + 2) and endogenous thrombin potential (ETP) are associated with myocardial necrosis assessed by Troponin T (TnT), and left ventricular impairment assessed by left ventricular ejection fraction (LVEF) and N-terminal pro b-type natriuretic peptide (NT-proBNP).

Materials/Methods

Patients (n = 987) with ST-elevation mycardial infarction (STEMI) were included. Blood samples were drawn at a median time of 24 h after onset of symptoms.

Results

Statistically significant correlations were found between both peak TnT and D-dimer (p < 0.001) and F1 + 2 (p < 0.001), and between NT-proBNP and D-dimer (p = 0.001) and F1 + 2 (p < 0.001). When dividing TnT and NT-proBNP levels into quartiles there were significant trends for increased levels of both markers across quartiles (all p < 0.001) D-dimer remained significantly associated with NT-proBNP after adjustments for covariates (p = 0.001) whereas the association between NTproBNP and F1 + 2 was no longer statistically significant (p = 0.324).

A significant inverse correlation was found between LVEF and D-dimer (p < 0.001) and F1 + 2 (p = 0.013). When dichotomizing LVEF levels at 40 %, we observed significantly higher levels of both D-dimer (p < 0.001) and F1 + 2 (p = 0.016) in the group with low EF (n = 147).

Summary/conclusion

In our cohort of STEMI patients we demonstrated that levels of D-dimer and F1 + 2 were significantly associated with myocardial necrosis as assessed by peak TnT. High levels of these coagulation markers in patients with low LVEF and high NTproBNP may indicate a hypercoagulable state in patients with impaired myocardial function.

Menopausal hormone treatment cardiovascular disease: another look at an unresolved conundrum

Cardiovascular disease (CVD) is the most common cause of death in women. Before the Women's Health Initiative (WHI) hormone trials, evidence favored the concept that menopausal hormone treatment (MHT) protects against CVD. WHI studies failed to demonstrate CVD benefit, with worse net outcomes for MHT versus placebo in the population studied. We review evidence regarding the relationship between MHT and CVD with consideration of mechanisms and risk factors for atherogenesis and cardiac events, results of observational case-control and cohort studies, and outcomes of randomized trials. Estrogen effects on CVD risk factors favor delay or amelioration of atherosclerotic plaque development but may increase risk of acute events when at-risk plaque is present. Long-term observational studies have shown ∼40% reductions in risk of myocardial infarction and all-cause mortality. Analyses of data from randomized control trials other than the WHI show a ∼30% cardioprotective effect in recently menopausal women. Review of the literature as well as WHI data suggests that younger and/or more recently menopausal women may have a better risk-benefit ratio than older or remotely menopausal women and that CVD protection may only occur after >5 years; WHI women averaged 63 years of age (12 years postmenopausal) and few were studied for >6 years. Thus, a beneficial effect of long-term MHT on CVD and mortality is still an open question and is likely to remain controversial for the foreseeable future.

Proteomic analysis of secretory proteins and vesicles in vascular research

The release of proteins and membrane vesicles in the bloodstream regulates diverse vascular processes, both physiological, such as angiogenesis and haemostasis, and pathological, such as atherosclerosis and atherothrombosis. Proteomics, beside its canonical application for the expression profiling in cells and organs, can be applied to the study of secreted proteins and microvesicles, which play a significant role in the homeostasis of the vasculature, and the development of the atherosclerotic disease.

In vivo detection of activated platelets allows characterizing rupture of atherosclerotic plaques with molecular magnetic resonance imaging in mice

BACKGROUND

Early and non-invasive detection of platelets on micro atherothrombosis provides a means to identify unstable plaque and thereby allowing prophylactic treatment towards prevention of stroke or myocardial infarction. Molecular magnetic resonance imaging (mMRI) of activated platelets as early markers of plaque rupture using targeted contrast agents is a promising strategy. In this study, we aim to specifically image activated platelets in murine atherothrombosis by in vivo mMRI, using a dedicated animal model of plaque rupture.

METHODS

An antibody targeting ligand-induced binding sites (LIBS) on the glycoprotein IIb/IIIa-receptor of activated platelets was conjugated to microparticles of iron oxide (MPIO) to form the LIBS-MPIO contrast agent causing a signal-extinction in T2*-weighted MRI. ApoE(-/-) mice (60 weeks-old) were fed a high fat diet for 5 weeks. Using a small needle, the surface of their carotid plaques was scratched under blood flow to induce atherothrombosis. In vivo 9.4 Tesla MRI was performed before and repetitively after intravenous injection of either LIBS-MPIO versus non-targeted-MPIO.

RESULTS

LIBS-MPIO injected animals showed a significant signal extinction (p<0.05) in MRI, corresponding to the site of plaque rupture and atherothrombosis in histology. The signal attenuation was effective for atherothrombosis occupying ≥ 2% of the vascular lumen. Histology further confirmed significant binding of LIBS-MPIO compared to control-MPIO on the thrombus developing on the surface of ruptured plaques (p<0.01).

CONCLUSION

in vivo mMRI detected activated platelets on mechanically ruptured atherosclerotic plaques in ApoE(-/-) mice with a high sensititvity. This imaging technology represents a unique opportunity for noninvasive detection of atherothrombosis and the identification of unstable atherosclerotic plaques with the ultimate promise to prevent strokes and myocardial infarctions.

Inflammatory and thrombotic markers in patients with ST-elevation myocardial infarction treated with thrombolysis and early PCI: a NORDISTEMI substudy

INTRODUCTION

Both pharmacological and invasive treatment might influence the inflammatory and pro-thrombotic responses observed in acute ST-elevation myocardial infarction (STEMI). We aimed to study whether circulating levels of inflammatory and pro-thrombotic markers differ in STEMI patients treated with early angioplasty compared to standard therapy following thrombolysis. Furthermore, we wanted to study if levels of markers were related to infarct size.

MATERIALS AND METHODS

This was a substudy of the NORwegian study on DIstrict treatment of ST-Elevation Myocardial Infarction (NORDISTEMI), in which STEMI patients treated with thrombolysis were randomized to early invasive or standard therapy. Fasting blood samples were collected in the morning 3 days and 3 months after onset of STEMI. Commercially available ELISA methods were used for determination of inflammatory and pro-thrombotic markers. Infarct size was assessed by SPECT after 3 months.

RESULTS

246 patients were included in this substudy. At 3 days, levels of prothrombin fragment 1+2 and D-dimer were higher in the early invasive compared to the standard treatment group, whereas levels of soluble CD40 ligand were lower (p<0.01 for all). No other differences between groups were found in any of the measured markers. Significant, although weak correlations were found between Day 3 levels of C-reactive protein, interleukin-6, prothrombin fragment 1+2 and D-dimer, and infarct size assessed by SPECT after 3 months.

CONCLUSIONS

An early invasive strategy following thrombolysis for STEMI was associated with higher subacute levels of D-dimer and prothrombin fragment 1+2, and lower levels of soluble CD40 ligand than standard treatment. Further studies are needed to establish the relation between these changes and clinical outcome. The NORDISTEMI was registered at www.clinicaltrials.gov, NCT00161005.

Update: Estrogen and Estrogen plus Progestin Therapy in the Care of Women at and after the Menopause

Much new information on menopausal hormone therapy (MHT) has become available since the publication of the first report of the Women's Health Initiative in 2002 and a consensus is now emerging. The risk of breast cancer depends on type of MHT, duration of use, body mass, breast density and interval between menopause and starting MHT. The risk of breast cancer is generally increased by MHT, particularly in lean women with no previous MHT who start estrogen–progestin therapy near the menopause and continue for several years, but there is no increased risk 5 years after stopping MHT. The risks of venous thrombo-embolic disease (VTE), stroke and coronary heart disease (CHD) depend on age on starting MHT, dose, nature and route of administration of MHT. The risk of VTE is increased in women over 60 years of age and in women who are obese or have had a VTE but may not be increased by transdermal estrogens. The risk of stroke is very small in women under 60 years of age and may not be increased by low dose oral and low dose transdermal estrogen, MHT is of benefit in preventing atherosclerosis and CHD in healthy younger postmenopausal women (under the age of 60) but is not of benefit, and may be harmful, in older women with clinical or subclinical atherosclerosis. MHT prevents bone loss and osteoporosis but is not generally recommended in women over 60 because of the risks of VTE, stroke and CHD, and if stopped at 60 years does not prevent fractures in later life. MHT reduces the overall mortality in women under 60. MHT is by far the most effective treatment, and greatly improves the quality of life in women with menopausal symptoms. A simplified approach to MHT is suggested as a framework for the care of women at and after the menopause.

Current concepts of platelet activation: possibilities for therapeutic modulation of heterotypic vs. homotypic aggregation

Thrombogenic and inflammatory activity are two distinct aspects of platelet biology, which are sustained by the ability of activated platelets to interact with each other (homotypic aggregation) and to adhere to circulating leucocytes (heterotypic aggregation). These two events are regulated by distinct biomolecular mechanisms that are selectively activated in different pathophysiological settings. They can occur simultaneously, for example, as part of a pro-thrombotic/pro-inflammatory response induced by vascular damage, or independently, as in certain clinical conditions in which abnormal heterotypic aggregation has been observed in the absence of intravascular thrombosis. Current antiplatelet drugs have been developed to target specific molecular signalling pathways mainly implicated in thrombus formation, and their ever increasing clinical use has resulted in clear benefits in the treatment and prevention of arterial thrombotic events. However, the efficacy of currently available antiplatelet drugs remains suboptimal, most likely because their therapeutic action is limited to only few of the signalling pathways involved in platelet homotypic aggregation. In this context, modulation of heterotypic aggregation, which is believed to contribute importantly to acute thrombotic events, as well to the pathophysiology of atherosclerosis itself, may offer benefits over and above the classical antiplatelet approach. This review will focus on the distinct biomolecular pathways that, following platelet activation, underlie homotypic and heterotypic aggregation, aiming potentially to identify novel therapeutic targets.

Expression of proinflammatory, proatherogenic genes is reduced by the Mediterranean diet in elderly people

Ageing is an important determinant of atherosclerosis development rate, mainly by the creation of a chronic low-grade inflammation. Diet, and particularly its fat content, modulates the inflammatory response in the fasting and postprandial states. Our aim was to study the effects of dietary fat on the expression of genes related to inflammation (NF-κB, monocyte chemoattractant protein 1 (MCP-1), TNF-α and IL-6) and plaque stability (matrix metalloproteinase 9, MMP-9) during the postprandial state of twenty healthy, elderly people who followed three diets for 3 weeks each: (1) Mediterranean diet (Med Diet) enriched in MUFA with virgin olive oil; (2) SFA-rich diet; and (3) low-fat, high-carbohydrate diet enriched in n-3 PUFA (CHO-PUFA diet) by a randomised crossover design. At the end of each period, after a 12-h fast, the subjects received a breakfast with a composition similar to the one when the dietary period ended. In the fasting state, the Med Diet consumption induced a lower gene expression of the p65 subunit of NF-κB compared with the SFA-rich diet (P = 0·019). The ingestion of the Med Diet induced a lower gene postprandial expression of p65 (P = 0·033), MCP-1 (P = 0·0229) and MMP-9 (P = 0·041) compared with the SFA-rich diet, and a lower gene postprandial expression of p65 (P = 0·027) and TNF-α (P = 0·047) compared with the CHO-PUFA diet. Direct plasma quantification mostly reproduced the findings. Our data suggest that consumption of a Med Diet reduces the postprandial inflammatory response in mononuclear cells compared with the SFA-rich and CHO-PUFA diets in elderly people. These findings may be partly responsible for the lower CVD risk found in populations with a high adherence to the Med Diet.

Targeted probes for cardiovascular MRI

Molecular MRI plays an important role in studying molecular and cellular processes associated with heart disease. Targeted probes that recognize important biomarkers of atherosclerosis, apoptosis, necrosis, angiogenesis, thrombosis and inflammation have been developed. This review discusses the properties of chemically different contrast agents including iron oxide nanoparticles, gadolinium-based nanoparticles or micelles, discrete peptide conjugates and activatable probes. Numerous examples of contrast agents based on these approaches have been used in preclinical MRI of cardiovascular diseases. Clinical applications are still under investigation for some selected agents with highly promising initial results. Molecular MRI shows great potential for the detection and characterization of a wide range of cardiovascular diseases, as well as for monitoring response to therapy.

Location of coronary culprit lesions at autopsy in 41 nondiabetic patients with acute myocardial infarction

BACKGROUND

Coronary artery disease and myocardial infarction (MI) are major causes of patient morbidity, hospital mortality, and out-of-hospital sudden death. The precise location of culprit lesions in acute MI at autopsy has not been reported.

OBJECTIVE

The purpose of this retrospective histopathologic autopsy study was to determine the distribution of coronary culprit lesions in acute fatal MI.

METHODS

Cross-sections of epicardial coronary arteries were evaluated microscopically. For each culprit lesion, its distance from the coronary ostium and its grade of luminal stenosis were recorded.

RESULTS

The study group included 41 nondiabetic patients (mean age of 65 years, 66% males) who underwent autopsy at Mayo Clinic Rochester (1994-2005). Culprit lesions occurred within the proximal 3.0 cm of the left anterior descending artery in 86% and the left circumflex artery in 100%. In contrast, culprit plaques within the right coronary artery (RCA) were distributed evenly throughout its length.

CONCLUSIONS

Among nondiabetic patients with acute fatal MI, culprit lesions exhibited proximal clustering in the left anterior descending artery and left circumflex artery, in contrast to more uniform distribution in the RCA. Thus, for the autopsy investigation of sudden death, evaluation for culprit lesions in the entire length of the RCA, not just its proximal region, is recommended.

An ultrasound contrast agent targeted to P-selectin detects activated platelets at supra-arterial shear flow conditions

OBJECTIVES

To evaluate targeting of a microbubble contrast agent to platelets under high shear flow using the natural selectin ligand sialyl Lewis.

MATERIALS AND METHODS

Biotinylated polyacrylamide Sialyl Lewis or biotinylated carbohydrate-free polymer (used as a control) were attached to biotinylated microbubbles via a streptavidin linker. Activated human platelets were isolated and attached to fibrinogen-coated culture dishes. Fibrinogen-coated dishes without platelets or platelet dishes blocked by an anti-P-selectin antibody served as negative control substrates. Dishes coated by recombinant P-selectin served as a positive control substrate. Microbubble adhesion was assessed by microscopy in an inverted parallel plate flow chamber, with wall shear stress values of 40, 30, 20, 10, and 5 dynes/cm2. The ratio of binding and passing microbubbles was defined as capture efficiency.

RESULTS

There was no significant difference between the groups regarding the number of microbubbles in the fluid flow at each shear rate. Sialyl Lewis-targeted microbubbles were binding and slowly rolling on the surface of activated platelets and P-selectin-coated dishes at all the flow conditions including 40 dynes/cm2. Capture efficiency of targeted microbubbles to activated platelets and recombinant P-selectin decreased with increasing shear flow: at 5 dynes/cm2, capture efficiency was 16.11% on activated platelets versus 21.83% on P-selectin, and, at 40 dynes/cm2, adhesion efficiency was still 3.4% in both groups. There was neither significant adhesion of Sialyl Lewis-targeted microbubbles to control substrates, nor adhesion of control microbubbles to activated platelets or to recombinant P-selectin.

CONCLUSIONS

Microbubble targeting using sialyl Lewis, a fast-binding ligand to P-selectin, is a promising strategy for the design of ultrasound contrast binding to activated platelets under high shear stress conditions.

Synergistic effect of a factor Xa inhibitor, TAK-442, and antiplatelet agents on whole blood coagulation and arterial thrombosis in rats

INTRODUCTION

Activated platelets facilitate blood coagulation by providing factor V and a procoagulant surface for prothrombinase. Here, we investigated the potential synergy of a potent factor Xa/prothrombinase inhibitor, TAK-442, plus aspirin or clopidogrel in preventing arterial thrombosis and whole blood coagulation.

METHODS

Thrombus formation was initiated by FeCl(3)-induced rat carotid injury. Bleeding time was evaluated with the rat tail transection model. Whole blood coagulation was assessed by thromboelastographic examination (TEG) for which blood obtained from control, aspirin-, or clopidogrel-treated rats was transferred to a TEG analyzer containing, collagen or adenosine diphosphate (ADP), and TAK-442 or vehicle.

RESULTS

TAK-442 (3mg/kg, po), aspirin (100mg/kg, po) or clopidogrel (3mg/kg, po) alone had no significant effect on thrombus formation, whereas the combination of TAK-442 with aspirin and clopidogrel remarkably prolonged the time to thrombus formation without additional significant prolongation of bleeding time. TEG demonstrated that the onset of collagen-induced blood coagulation were slightly longer in aspirin-treated rats than control; however, when the blood from aspirin-treated rats was subsequently treated in vitro with 100 nM TAK-442, the onset of clotting was significantly prolonged. In contrast, only marginal prolongation was observed with TAK-442 treatment of blood from control animals. The onset time of ADP-induced blood coagulation was slightly longer in clopidogrel-treated rats compared with control, and it was further extended by TAK-442 treatment.

CONCLUSION

These results demonstrate that blood coagulation can be markedly delayed by the addition of TAK-442 to antiplatelets treatment which could contribute to synergistic antithrombotic efficacy in these settings.

Inhibitory mechanisms of dihydroginsenoside Rg3 in platelet aggregation: Critical roles of ERK2 and cAMP

Ginsenoside Rg3, a single ginseng saponin, is known to be a major anti-platelet component of protopanaxadiol that is isolated from Korean red ginseng. In this study, we investigated whether dihydroginsenoside Rg3, a stable chemical derivative of ginsenoside Rg3, also demonstrated anti-platelet activity. Dihydroginsenoside Rg3 inhibited thrombin-induced platelet aggregation in a concentration-dependent manner with an IC50 (concentration producing 50% inhibition) of 18.8 ± 0.4 μM. Ginsenoside Rg3 inhibited platelet aggregation which was induced by thrombin (0.1 U mL−1) with an IC50 of 40.2 ± 0.9 μM. We next determined whether dihydroginsenoside Rg3 affected different types of ligand-induced platelet aggregation. We found that dihydroginsenoside Rg3 inhibited collagen-induced platelet aggregation with an IC50 of 20.0 ± 0.9 μM. To elucidate the inhibitory mechanism of dihydroginsenoside Rg3 on aggregation, we analysed its downstream signalling pathway. It was interesting to note that dihydroginsenoside Rg3 elevated cyclic AMP production in resting platelets, but did not affect cyclic GMP production. In addition, we found that dihydroginsenoside Rg3 potently suppressed phosphorylation of extracellular signal-regulated kinase 2 (ERK2), which was stimulated by collagen (2.5 μg mL−1), but not of p38 mitogen-activated protein kinase. Taken together, our results indicate that dihydroginsenoside Rg3 potently inhibited platelet aggregation via the modulation of downstream signalling components such as cAMP and ERK2.

Is Increased Thrombin Activation in Patients With Abdominal Aortic Aneurysms Dependent on Area or Volume of Aneurysm Thrombus Mass?

Objectives: Does thrombin activation seen in patients with abdominal aortic aneurysms (AAA) relate to the thrombus surface area or volume within the aneurysm? Patients and methods: A total of 130 patients with AAA were analyzed regarding levels of the complex between activated protein C—protein C inhibitor (APC-PCI) and AAA morphology. Analysis of APC-PCI complex was made using a sandwich immunofluorometric method. Results: Increased APC-PCI concentrations were seen in patients with AAA (0.44 μg/L; P < .001 compared with controls). The correlations of APC-PCI values were r = .13, P = .13 for aneurysm size, r = .08, P = .35 for thrombus surface area, and r = .13, P = .14 for thrombus volume. APC-PCI values elevated to 0.45 μg/L in 10 patients with AAA having no or very little thrombus mass. Conclusion: Disappointingly, no correlation was found between thrombus surface area or volume and levels of the APC-PCI complex. Mechanisms other than the AAA-sac thrombus must be evaluated as cause of thrombin activation in patients with AAA.

Baseline clinical characteristics and midterm prognosis of STE-ACS and NSTE-ACS patients with normal coronary arteries

OBJECTIVE

We sought to compare clinical profiles and midterm prognosis of patients with normal coronary arteries presenting with ST-elevation ACS (STE-ACS) versus non-ST-elevation ACS (nSTE-ACS).

BACKGROUND

There are limited data regarding ACS in patients with normal coronary arteries, and especially clinical differences between ST-ACS and nSTE-ACS patients have not been evaluated sufficiently.

METHODS

The study group comprised 190 patients (mean age: 53.2 years, 63.1% males, 63.6% STE-ACS) presenting with ACS and normal coronary angiograms. The participants were evaluated in terms of 42 clinical variables. MACE [cardiac death (CD) and hospitalization for angina (HA)] were the study end points.

RESULTS

STE-ACS in comparison to nSTE-ACS patients were younger (P < 0.01), were more frequently males (P < 0.01), had more often infection prior to ACS (P < 0.01), higher hsCRP on admission (P < 0.01), and greater infarct size, measured by maximal troponin I (P < 0.01). By multivariate analysis in this subgroup, predictors of outcome were hsCRP (P = 0.03) and raised troponin I (P = 0.02). nSTE-ACS in comparison to STE-ACS patients were more obese (BMI, P < 0.01), had higher LDL cholesterol (P < 0.01), fasting glucose (P = 0.03). LDL cholesterol (P = 0.02) and fasting glucose (P = 0.03) emerged as independent predictors of outcome in these patients. Mean follow-up period was 25.4 months. STE-ACS patients had twice fewer MACE rate than nSTE-ACS patients [(1-CD, 12-HA; 11%) vs (1-CD, 16-HA; 25%), respectively, log rank P < 0.01].

CONCLUSIONS

STE-ACS and nSTE-ACS patients with normal coronary arteriography have different clinical profiles. In nSTE-ACS patients more pronounced metabolic abnormalities were identified, while in STE-ACS patients inflammatory background was more significant.

Evaluation of urine proteome pattern analysis for its potential to reflect coronary artery atherosclerosis in symptomatic patients

Coronary artery disease (CAD) is a major cause of mortality and morbidity. Noninvasive proteome analysis could guide clinical evaluation and early/preventive treatment. Under routine clinical conditions, urine of 67 patients presenting with symptoms suspicious for CAD were analyzed by capillary electrophoresis directly coupled with mass spectrometry (CE-MS). All patients were subjected to coronary angiography and either assigned to a CAD or non-CAD group. A training set of 29 patients was used to establish CAD and non-CAD-associated proteome patterns of plasma as well as urine. Significant discriminatory power was achieved in urine but not in plasma. Therefore, urine proteomic analysis of further 38 patients was performed in a blinded study. A combination of 17 urinary polypeptides allowed separation of both groups in the test set with a sensitivity of 81%, a specificity of 92%, and an accuracy of 84%. Sequencing of urinary marker peptides identified fragments of collagen alpha1 (I and III), which we furthermore demonstrated to be expressed in atherosclerotic plaques of human aorta. In conclusion, specific CE-MS polypeptide patterns in urine were associated with significant CAD in patients with angina-typical symptoms. These promising findings need to be further evaluated in regard to reliability of a urine-based screening method with the potential of improving the diagnostic approaches for CAD.

Magnetic Resonance Imaging Contrast Agent Targeted Toward Activated Platelets Allows In Vivo Detection of Thrombosis and Monitoring of Thrombolysis

Background— Platelets are the key to thrombus formation and play a role in the development of atherosclerosis. Noninvasive imaging of activated platelets would be of great clinical interest. Here, we evaluate the ability of a magnetic resonance imaging (MRI) contrast agent consisting of microparticles of iron oxide (MPIOs) and a single-chain antibody targeting ligand-induced binding sites (LIBS) on activated glycoprotein IIb/IIIa to image carotid artery thrombi and atherosclerotic plaques.

Methods and Results— Anti-LIBS antibody or control antibody was conjugated to 1-μm MPIOs (LIBS MPIO/control MPIO). Nonocclusive mural thrombi were induced in mice with 6% ferric chloride. MRI (at 9.4 T) was performed once before and repeatedly in 12-minute-long sequences after LIBS MPIO/control MPIO injection. After 36 minutes, a significant signal void, corresponding to MPIO accumulation, was observed with LIBS MPIOs but not control MPIOs ( P <0.05). After thrombolysis, in LIBS MPIO-injected mice, the signal void subsided, indicating successful thrombolysis. On histology, the MPIO content of the thrombus, as well as thrombus size, correlated significantly with LIBS MPIO-induced signal void (both P <0.01). After ex vivo incubation of symptomatic human carotid plaques, MRI and histology confirmed binding to areas of platelet adhesion/aggregation for LIBS MPIOs but not for control MPIOs.

Conclusions— LIBS MPIOs allow in vivo MRI of activated platelets with excellent contrast properties and monitoring of thrombolytic therapy. Furthermore, activated platelets were detected on the surface of symptomatic human carotid plaques by ex vivo MRI. This approach represents a novel noninvasive technique allowing the detection and quantification of platelet-containing thrombi.

15,16-dihydrotanshinone I, a major component from Salvia miltiorrhiza Bunge (Dansham), inhibits rabbit platelet aggregation by suppressing intracellular calcium mobilization

Radix Salviae miltiorrhiza (RSM, 'Dansham' in Korea, 'Danshen' in Chinese), the root of Salviae miltiorrhiza Bunge (Labiate) has been used as Chinese fork medicine for the treatment of cardiovascular diseases such as angina pectoris, coronary heart disease, myocardial infarction, and hypertension. In the present study, we evaluated the inhibitory effects of 15,16-Dihydrotanshinone I, one of the major ingredients of Salvia miltiorrhiza Bunge, on platelet aggregation, with elucidation of its mechanisms of action. 15,16-Dihydrotanshinone I concentration-dependently inhibited collagen-induced aggregation of rabbit washed platelets with IC50 of 8.7+/-5.6 microM, the potency being about seven-fold greater than EGCG, an active Green tea catechin component (IC50: 56.6+/-48.7 microM). 15,16-Dihydrotanshinone I significantly inhibited the intracellular calcium ([Ca2+]i) mobilization in a concentration-dependent manner. 15,16-dihdydrotanshinone I also significantly suppressed collagen (50 microg/mL)-induced liberation of [3H]Arachidonic acid from [3H]Arachidonic acid-incorporated rabbit platelet. In addition, 15,16-Dihydrotanshinone I at 50 microM slightly but significantly inhibited collagen-induced production of thromboxane B2. These results indicate that 15,16-Dihydrotanshinone I exert potent anti-platelet activity via suppression of [Ca2+]i mobilization and arachidonic acid liberation.

Resolution of asymptomatic myocardial ischemia in patients with type 2 diabetes in the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study

OBJECTIVE

The purpose of this study was to assess whether the prevalence of inducible myocardial ischemia increases over time in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Participants enrolled in the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study underwent repeat adenosine-stress myocardial perfusion imaging 3 years after initial evaluation. Patients with intervening cardiac events or revascularization and those who were unable or unwilling to repeat stress imaging were excluded.

RESULTS

Of the initial 522 DIAD patients, 358 had repeat stress imaging (DIAD-2), of whom 71 (20%) had ischemia at enrollment (DIAD-1). Of 287 patients with normal DIAD-1 studies, 259 (90%) remained normal in DIAD-2, whereas 28 (10%) developed new ischemia in DIAD-2. Of the 71 patients with abnormal DIAD-1 studies, 56 (79%) demonstrated resolution of ischemia, whereas 15 (21%) remained abnormal. During this 3-year interval, medical treatment was intensified, with more patients using statins, aspirin, and ACE inhibitors than at baseline. Patients with resolution of ischemia had significantly greater increases in these medications than patients who developed new ischemia (P = 0.04).

CONCLUSIONS

Thus, the majority of asymptomatic patients with type 2 diabetes demonstrated resolution of ischemia upon repeat stress imaging after 3 years. This resolution was associated with more intensive treatment of cardiovascular risk factors.

Antiplatelet activity of hesperetin, a bioflavonoid, is mainly mediated by inhibition of PLC-γ2 phosphorylation and cyclooxygenase-1 activity

Diet can be one of the most important factors that influence risks for atherothrombotic diseases. Hesperetin included in grapefruits and oranges is one candidate that may benefit the cardiovascular system. Here, we investigated antiplatelet activity of hesperetin in vitro. In addition, possible antiplatelet mechanism was also investigated. Hesperetin concentration-dependently inhibited washed rabbit platelet aggregation induced by collagen and arachidonic acid, with IC50 of 20.5+/-3.5 and 69.2+/-5.1 microM, respectively, while has little effect on thrombin- or U46619-, a thromboxane (TX) A2 mimic, mediated platelet aggregation, suggesting that hesperetin may selectively inhibit collagen- and arachidonic acid-mediated signal transduction. In accordance with these findings, hesperetin revealed blocking of the collagen-mediated phospholipase (PL) C-gamma2 phosphorylation, and caused concentration-dependent decreases of cytosolic calcium mobilization, arachidonic acid liberation and serotonin secretion. In addition, hesperetin inhibited arachidonic acid-mediated platelet aggregation by interfering with cyclooxygenase-1 activity as established by the measurement of arachidonic acid-mediated TXA2 and prostaglandin D2 formations as well as cyclooxygenase-1 and TXA2 synthase activity assays. Taken together, the present results provide a cellular mechanism for the antiplatelet activity of hesperetin through inhibition of PLC-gamma2 phosphorylation and cyclooxygenase-1 activity, which may contribute to the beneficial effects of grapefruits and oranges on cardiovascular system.

Antiplatelet and antithrombotic activity of indole-3-carbinol in vitro and in vivo

Indole-3-carbinol, a natural compound found in cruciferous vegetables, is known to have anticancer activity. In the present study, the antiplatelet and antithrombotic activities of indole-3-carbinol were investigated in vitro and in vivo. Indole-3-carbinol significantly inhibited collagen-induced platelet aggregation in human platelet rich plasma (PRP) in a concentration-dependent manner. Indole-3-carbinol significantly inhibited fibrinogen binding to the platelet surface glycoprotein IIb/IIIa (GP IIb/IIIa) receptor by flow cytometric analysis. In addition, the levels of thromboxane B2 (TXB2) and prostaglandin E2 (PGE2) in collagen stimulated PRP were significantly inhibited in a concentration-dependent manner by indole-3-carbinol. Furthermore, indole-3-carbinol dose-dependently suppressed the death of mice with pulmonary thrombosis induced by intravenous injection of collagen and epinephrine. These results suggest that indole-3-carbinol can be a potent antithrombotic agent with antiplatelet activity through the inhibition of GP IIb/IIIa receptor and thromboxane B2 formation.

A novel anti-ischemic nitric oxide donor (LA419) reduces thrombogenesis in healthy human subjects

BACKGROUND

Platelet and endothelial production of nitric oxide (NO) is known to be impaired in coronary artery disease patients. Compounds that release NO (e.g. nitrates) have antiplatelet effects, but at supratherapeutic doses with hypotensive side effects.

OBJECTIVES

To investigate the antithrombotic effect on human blood of a novel NO donor (LA419) with known anti-ischemic properties but without hypotensive side effects and to compare with abciximab.

PATIENTS/METHODS

Healthy subjects (n = 8; 32 +/- 3 years) received daily aspirin starting three days prior to the study day. Treatments (LA419 10 and 20 microm, and abciximab 4 microm) were added ex vivo to non-anticoagulated blood, and the antithrombotic properties were assessed by measuring changes in thrombus size from pretreatment baseline in the Badimon perfusion chamber at low and high shear rates. Platelet surface adhesion using a Cone and Platelet Analyzer (CPA) and platelet fibrinogen-receptor activation with flow cytometry were also evaluated.

RESULTS

At low shear rates, LA419 displayed a reduction in thrombus area of 43% +/- 8% (10 microm) and 56% +/- 6% (20 microm), whereas at high shear rates the reductions were 44% +/- 3% (10 microm) and 62% +/- 6% (20 microm). Platelet surface adhesion with the CPA was also reduced. Abciximab exhibited a strong inhibitory effect on thrombus formation, platelet surface adhesion and fibrinogen receptor activation.

CONCLUSIONS

The novel NO donor, LA419, shows a strong antithrombotic effect in human blood, which is comparable to abciximab, especially under high shear rate conditions. Our observations suggest that the availability of an NO donor could prove beneficial in the prevention of thrombotic complications of cardiovascular disease. Further clinical studies are warranted.

Predictors of coronary bypass grafting in a population of middle-aged men

BACKGROUND

Coronary bypass grafting is a procedure which is usually undertaken because of extensive coronary heart disease, whereas acute myocardial infarction may occur with patients with moderate or even minimal disease. Having undergone coronary bypass grafting may thus serve as a marker for extensive coronary atherosclerosis. The aim of this study was to assess risk factors for future coronary bypass grafting as a first coronary event, and to compare them with risk factors for a first acute myocardial infarction.

DESIGN

This was a prospective cohort study.

METHOD

In the Multifactor Primary Prevention Study, 7388 men aged 47-55 years and free of previous acute myocardial infarction or stroke were investigated between 1970 and 1973. During 28 years of follow-up 1664 men (22%) had an acute myocardial infarction or died from coronary disease. One hundred and forty six men (2%) underwent coronary bypass grafting with no prior acute infarction.

RESULTS

Serum cholesterol was a stronger predictor of coronary bypass grafting than of acute myocardial infarction. Compared to men with serum cholesterol of 5.0 or lower, men with serum cholesterol 5.1-6.4, 6.5-7.4 and over 7.4 mmol/l had age-adjusted hazard ratios for acute myocardial infarction of 1.22 (1.00-1.49), 1.66 (1.35-2.03) and 2.04 (1.65-2.51). Corresponding hazard ratios for coronary bypass grafting were 1.57 (0.66-3.70), 3.44 (1.47-8.03) and 5.21 (2.20-12.31) (95% confidence interval). In contrast, smoking was a weaker risk factor for coronary bypass grafting than for acute myocardial infarction with no discernible increase in risk except in very heavy smokers (25 g/day or more; n=193); hazard ratio 2.19 (1.02-4.66). Elevated blood pressure predicted coronary bypass grafting and acute myocardial infarction equally well. In multivariate analysis an increase in serum cholesterol of 1 mmol/l was associated with an odds ratio of 1.56 (1.38-1.76) for coronary bypass grafting but only 1.30 (1.24-1.36) for AMI (P for difference in odds ratio 0.004).

CONCLUSION

Elevated serum cholesterol is a stronger predictor for future coronary bypass grafting than for acute myocardial infarction. Moderate smoking was not associated with coronary bypass grafting. Different manifestations of coronary disease have different risk factor patterns, suggesting that secular changes in risk factor pattern could potentially influence the clinical expression of the disease.

Overexpression of lysosomal acid lipase and other proteins in atherosclerosis

Atherosclerosis is one of the major causes of morbidity and mortality in the western world. The existing data of elevated expression levels of proteins like DNA damage and DNA repair enzymes in human atherosclerotic plaques are reviewed. From the literature, the effect of overexpression of different proteins using adenoviral vectors or the model of transgenic mice on the development of atherosclerosis will be discussed. Special focus is placed on the lysosomal acid lipase (LAL), because LAL connects extra-cellular with intra-cellular lipid metabolism and is the only hydrolase for cleavage of cholesteryl esters delivered to the lysosomes. Patients with a deficiency of LAL show an accumulation of lipids in the cells and develop pre-mature atherosclerosis. To answer the question of the influence of LAL in atherosclerosis if overexpressed, we show for the first time data of transgenic mice overexpressing LAL and the effect on the lipid level.

Is the estrogen controversy over? Deconstructing the Women's Health Initiative study: a critical evaluation of the evidence

The Women's Health Initiative (WHI) hormone trials have been widely interpreted as demonstrating that combined menopausal hormone therapy (HT) fails to protect against-and may increase-cardiovascular disease (CVD), stroke, and dementia in menopausal women, regardless of whether initiated early in the menopause or later. This conclusion does not agree with results of large epidemiological studies showing protection by HT and by estrogen replacement alone (ET) against CVD and dementia. One possible reason for this inconsistency is that the epidemiologic data are confounded by "healthy user bias." Another possible explanation is that most women in the observational studies initiated ET or HT at or near the menopausal transition, at which point there is little or no arterial injury, whereas, in the WHI studies, older women, averaging approximately 12 years postmenopausal, many of whom would have had significant asymptomatic atherosclerosis, were treated. Substantial data demonstrate atheropreventive effects of estrogen before vascular damage occurs, whereas adverse effects of oral estrogen on thrombosis and inflammation may predominate once complex atheromas are present. Similarly, the excess of dementia observed in older WHI women treated with oral conjugated estrogen could be due to cerebral thromboses (multi-infarct dementia). Given the uncertain relevance of the WHI (and other published randomized clinical trials) to initiation of HT in perimenopausal women, and its subsequent continuation for atheroprevention, new trials will be needed to resolve whether early intervention with estrogen may prevent CVD and/or dementia. The Kronos Early Estrogen Prevention Study (KEEPS), which began in mid-2005, is a randomized, controlled multicenter trial of HT in recently menopausal women. It will examine surrogate end points as well as risk factors for atherosclerosis.

Antiplatelet activity of [5-(2-methoxy-5-chlorophenyl)furan-2-ylcarbonyl]guanidine (KR-32570), a novel sodium/hydrogen exchanger-1 and its mechanism of action

The antiplatelet effects of a novel guanidine derivative, KR-32570 ([5-(2-methoxy-5-chlorophenyl) furan-2-ylcarbonyl]guanidine), were investigated with an emphasis on the mechanisms underlying its inhibition of collagen-induced platelet aggregation. KR-32570 significantly inhibited the aggregation of washed rabbit platelets induced by collagen (10 microg/mL), thrombin (0.05 U/mL), arachidonic acid (100 microM), a thromboxane (TX) A2 mimetic agent U46619 (9,11-dideoxy-9,11-methanoepoxy-prostaglandin F2, 1 microM) and a Ca2+ ATPase inhibitor thapsigargin (0.5 microM) (IC50 values: 13.8 +/- 1.8, 26.3 +/- 1.2, 8.5 +/- 0.9, 4.3 +/- 1.7 and 49.8 +/- 1.4 microM, respectively). KR-32570 inhibited the collagen-induced liberation of [3H]arachidonic acid from the platelets in a concentration dependent manner with complete inhibition being observed at 50 microM. The TXA2 synthase assay showed that KR-32570 also inhibited the conversion of the substrate PGH2 to TXB2 at all concentrations. Furthermore, KR-32570 significantly inhibited the [Ca2+]i mobilization induced by collagen at 50 microM, which is the concentration that completely inhibits platelet aggregation. KR-32570 also decreased the level of collagen (10 microg/mL)-induced secretion of serotonin from the dense-granule contents of platelets, and inhibited the NHE-1-mediated rabbit platelet swelling induced by intracellular acidification. These results suggest that the antiplatelet activity of KR-32570 against collagen-induced platelet aggregation is mediated mainly by inhibiting the release of arachidonic acid, TXA2 synthase, the mobilization of cytosolic Ca2+ and NHE-1.

Oral streptococci and cardiovascular disease: searching for the platelet aggregation-associated protein gene and mechanisms of Streptococcus sanguis-induced thrombosis

BACKGROUND

Pathogenic mechanisms in infective endocarditis, disseminated intravascular coagulation, and cardiovascular events involve the aggregation of platelets into thrombi. Attendant infection by oral bacteria contributes to these diseases. We have been studying how certain oral streptococci induce platelet aggregation in vitro and in vivo. Streptococcus sanguis expresses a platelet aggregation-associated protein (PAAP), which contributes little to adhesion to platelets. When specific antibodies or peptides block PAAP, S. sanguis fails to induce platelet aggregation in vitro or in vivo.

METHODS

We used subtractive hybridization to identify the gene encoding for PAAP.

RESULTS

After subtraction of strain L50 (platelet aggregation-negative), four strain 133-79 specific sequences were characterized. Sequence agg4 encoded a putative collagen-binding protein (CbpA), which was predicted to contain two PAAP collagen-like octapeptide sequences. S. sanguis CbpA- mutants were constructed and tested for induction of platelet aggregation in vitro. Platelet aggregation was substantially inhibited when compared to the wild-type using platelet-rich plasma from the principal donor, but adhesion was unaffected. Other donor platelets responded normally to the CbpA- strain, suggesting additional mechanisms of response to S. sanguis. In contrast, CshA- and methionine sulfoxide reductase-negative (MsrA-) strains neither adhered nor induced platelet aggregation.

CONCLUSIONS

CbpA was suggested to contribute to site 2 interactions in our two-site model of platelet aggregation in response to S. sanguis. Platelet polymorphisms were suggested to contribute to the thrombogenic potential of S. sanguis.

Long-term treatment with ximelagatran, an oral direct thrombin inhibitor, persistently reduces the coagulation activity after a myocardial infarction

BACKGROUND

In the ESTEEM study, patients with a recent myocardial infarction were treated with aspirin and randomized to one of four doses (24-60 mg b.i.d) of the oral direct thrombin inhibitor ximelagatran or placebo for 6 months. Ximelagatran and aspirin reduced the risk of recurrent ischemic events compared with aspirin alone. In the present substudy we evaluated the different doses of ximelagatran on pharmacokinetics as measured by plasma concentration of the active compound melagatran and activated partial thromboplastin time (APTT) and pharmacodynamics as related by markers for coagulation activity, prothrombin fragment 1 + 2 (F1 + 2) and D-dimer.

METHODS AND RESULTS

Plasma samples from 518 patients were collected before, during and after the treatment period. There was a linear dose-concentration relation at peak and trough and a linear relation between concentration and APTT (P < 0.001). F1 + 2 and D-dimer were decreased by 25% and 52% at 1 week (P < 0.001) in the ximelagatran groups compared with the placebo group and the reductions were maintained during the 6 months treatment. There were no differences detected in F1 + 2 or D-dimer levels between the different ximelagatran dosages. There was no correlation between the melagatran concentration and the change in F1 + 2 and D-dimer levels. After cessation of ximelagatran F1 + 2 and D-dimer levels returned to the initial levels.

CONCLUSION

The dose of ximelagatran and APTT are linearly related to the plasma concentration of melagatran. Ximelagatran induces a sustained and stable reduction of thrombin generation and fibrin turnover without any relation to dose above 24 mg b.i.d. These properties indicate that long-term treatment with a low dose of ximelagatran may provide valuable depression of coagulation activity in aspirin treated post myocardial infarction patients.

Pharmacotherapy of Acute Coronary Syndromes: Medical Economics with an Emphasis on Clopidogrel

Acute coronary syndromes account worldwide for a significant burden of hospital- and societal costs. Pharmacotherapy of acute coronary syndromes consists of a combined antithrombotic therapy. Remarkable therapeutic advances have been made with the introduction of glycoprotein IIb/IIIa receptor inhibitors, low molecular weight heparins and thienopyridines, such as clopidogrel. Based on positive clinical data of large randomized trials numerous cost studies have been undertaken to analyse the cost-effectiveness of these new drugs. Most of them are showing an acceptable level of cost-effectiveness for the new treatments. Taking all available cost-studies into account, we conclude that new antithrombotic treatments are cost-effective as long as their use is limited to selected patient populations.

Carotid Atherosclerotic Plaque Characteristics Are Associated With Microembolization During Carotid Endarterectomy and Procedural Outcome

Background and Purpose— During carotid endarterectomy (CEA), microemboli may occur, resulting in perioperative adverse cerebral events. The objective of the present study was to investigate the relation between atherosclerotic plaque characteristics and the occurrence of microemboli or adverse events during CEA.

Methods— Patients (n=200, 205 procedures) eligible for CEA were monitored by perioperative transcranial Doppler. The following phases were discriminated during CEA: dissection, shunting, release of the clamp, and wound closure. Each carotid plaque was stained for collagen, macrophages, smooth muscle cells, hematoxylin, and elastin. Semiquantitative analyses were performed on all stainings. Plaques were categorized into 3 groups based on overall appearance (fibrous, fibroatheromatous, or atheromatous).

Results— Fibrous plaques were associated with the occurrence of more microemboli during clamp release and wound closure compared with atheromatous plaques ( P =0.04 and P =0.02, respectively). Transient ischemic attacks and minor stroke occurred in 5 of 205 (2.4%) and 6 of 205 (2.9%) patients, respectively. Adverse cerebral outcome was significantly related to the number of microembolic events during dissection ( P =0.003) but not during shunting, clamp release, or wound closure. More cerebrovascular adverse events occurred in patients with atheromatous plaques (7/69) compared with patients with fibrous or fibroatheromatous plaques (4/138) ( P =0.04).

Conclusions— Intraoperatively, a higher number of microemboli were associated with the presence of a fibrous but not an atheromatous plaque. However, atheromatous plaques were more prevalent in patients with subsequent immediate adverse events. In addition, specifically the number of microemboli detected during the dissection phase were related to immediate adverse events.