Platelet aggregation and aspirin non-responsiveness increase when an acute coronary syndrome is complicated by an infection

Urine 11-Dehydro-Thromboxane B2 in Aspirin-Naive Males with Metabolic Syndrome

Urine 11-dehydro-thromboxane B2 (11-dehydro-TXB2), an indirect measure of platelet activity, is elevated in cardiovascular diseases and diabetes. The purpose of our study was to determine whether urine 11-dehydro-TXB2 is elevated in aspirin-naive males with metabolic syndrome (MS) and to determine predictors of 11-dehydro-TXB2 levels. The secondary aim was to evaluate whether these MS patients could be potential candidates for the aspirin-mediated prevention of atherosclerotic cardiovascular diseases (ASCVDs). In 82 males with MS (76 hypertensive), anthropometric measures, urine 11-dehydro-TXB2, platelet count, creatinine, glucose, insulin, estimated insulin resistance, lipid parameters, high-sensitivity C-reactive protein (hs-CRP), adiponectin, homocysteine, and ten-year risk of fatal cardiovascular disease (SCORE) were assessed. Urine 11-dehydro-TXB2 levels were elevated (≥2500 pg/mg creatinine) in two-thirds of patients, including 11 high-risk patients (SCORE ≥ 5%). Homocysteine, adiponectin, hs-CRP, waist-to-hip ratio, and total cholesterol were found to be predictors of urine 11-dehydro-TXB2. In conclusion, there is a high incidence of elevated urine 11-dehydro-TXB2 in males with MS, including in some patients who are at a high or very high risk of ASCVDs. 11-dehydro-TXB2 levels are associated with hyperhomocysteinemia, inflammation, fat distribution, hypercholesterolemia, and adiponectin concentrations. Elevated 11-dehydro-TXB2 levels may support the use of personalised aspirin ASCVD prevention in high-risk males with MS. Giuseppe Patti.

Can N-3 polyunsaturated fatty acids be considered a potential adjuvant therapy for COVID-19-associated cardiovascular complications?

Coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has currently led to a global pandemic with millions of confirmed and increasing cases around the world. The novel SARS-CoV-2 not only affects the lungs causing severe acute respiratory dysfunction but also leads to significant dysfunction in multiple organs and physiological systems including the cardiovascular system. A plethora of studies have shown the viral infection triggers an exaggerated immune response, hypercoagulation and oxidative stress, which contribute significantly to poor cardiovascular outcomes observed in COVID-19 patients. To date, there are no approved vaccines or therapies for COVID-19. Accordingly, cardiovascular protective and supportive therapies are urgent and necessary to the overall prognosis of COVID-19 patients. Accumulating literature has demonstrated the beneficial effects of n-3 polyunsaturated fatty acids (n-3 PUFA) toward the cardiovascular system, which include ameliorating uncontrolled inflammatory reactions, reduced oxidative stress and mitigating coagulopathy. Moreover, it has been demonstrated the n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors to a group of potent bioactive lipid mediators, generated endogenously, which mediate many of the beneficial effects attributed to their parent compounds. Considering the favorable safety profile for n-3 PUFAs and their metabolites, it is reasonable to consider n-3 PUFAs as potential adjuvant therapies for the clinical management of COVID-19 patients. In this article, we provide an overview of the pathogenesis of cardiovascular complications secondary to COVID-19 and focus on the mechanisms that may contribute to the likely benefits of n-3 PUFAs and their metabolites.

Perioperative changes of response to antiplatelet medication in vascular surgery patients

Introduction

Reduced antiplatelet activity of aspirin (ALR) or clopidogrel (CLR) is associated with an increased risk of thromboembolic events. The reported prevalence data for low-responders vary widely and there have been few investigations in vascular surgery patients even though they are at high risk for thromb-embolic complications. The aim of this prospective observational monocentric study was to elucidate possible changes in ALR or CLR after common vascular procedures.

Methods

Activity of aspirin and clopidogrel was measured by impedance aggregometry using a multiple electrode aggregometer (Multiplate®). Possible risk factors for ALR or CLR were identified by demographical, clinical data and laboratory parameters. In addition, a follow-up aggregometry was performed after completion of the vascular procedure to identify changes in antiplatelet response.

Results

A total of 176 patients taking antiplatelet medications aspirin and/or clopidogrel with peripheral artery disease (PAD) and/or carotid stenosis (CS) were included in the study. The prevalence of ALR was 13.1% and the prevalence of CLR was 32% in the aggregometry before vascular treatment. Potential risk factors identified in the aspirin group were concomitant insulin medication (p = 0.0006) and elevated C-reactive protein (CRP) (p = 0.0021). The overall ALR increased significantly postoperatively to 27.5% (p = 0.0006); however, there was no significant change in CLR that was detected. In a subgroup analysis elevation of the platelet count was associated with a post-procedure increase of ALR incidence.

Conclusion

The incidence of ALR in vascular surgery patients increases after vascular procedures. An elevated platelet count was detected as a risk factor. Further studies are necessary to analyse this potential influence on patency rates of vascular reconstructions.

Impact of infection in patients with non-ST elevation acute coronary syndrome undergoing percutaneous coronary intervention: insight from a multicentre observational cohort from China

OBJECTIVE

We aimed to describe the association between in-hospital infection and prognosis among patients with non-ST elevation acute coronary syndrome (NSTE-ACS) who received percutaneous coronary intervention (PCI).

DESIGN

This observational cohort originated from a database of patients with NSTE-ACS who underwent PCI from 1 January 2010 to 31 December 2014.

SETTING

Five centres in South China.

PARTICIPANTS

This multicentre observational cohort study consecutively included 8197 patients with NSTE-ACS who received PCI. Only patients with adequate information to diagnose or rule out infection were included. Patients were excluded if they were diagnosed with a malignant tumour, were pregnant or presented with cardiogenic shock at the index date. Patients were grouped by whether they had in-hospital infection or not.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was all-cause death and major bleeding during hospitalisation. The secondary outcomes included all-cause death and major bleeding during follow-up and in-hospital myocardial infarction.

RESULTS

Of the 5215 patients, 206 (3.95%) acquired infection. Patients with infection had a higher rate of in-hospital all-cause death and major bleeding (4.4% vs 0.2% and 16.5% vs 1.2%, respectively; p<0.001). After adjusting for confounders, infection remained independently associated with in-hospital and long-term all-cause death (OR, 13.19, 95% CI 4.59 to 37.87; HR, 2.03, 95% CI 1.52 to 2.71; p<0.001) and major bleeding (OR, 10.24, 95% CI 6.17 to 16.98; HR, 5.31, 95% CI 3.49 to 8.08; p<0.001). A subgroup analysis confirmed these results.

CONCLUSIONS

The incidence of infection is low during hospitalisation, but is associated with worse in-hospital and long-term outcomes.

Post-Infectious Myocardial Infarction: Does Percutaneous Coronary Intervention Improve Outcomes? A Propensity Score-Matched Analysis

Acute infection is a frequent trigger of myocardial infarction (MI). However, whether percutaneous coronary intervention (PCI) improves post-infectious MI prognosis is a major but unsolved issue. In this prospective multicenter study from coronary care units, we performed propensity score-matched analysis to compare outcomes in patients with and without PCI for post-infectious MI with angiography-proven significant coronary stenosis (>50%). Among 4573 consecutive MI patients, 476 patients (10%) had a concurrent diagnosis of acute infection at admission, of whom 375 underwent coronary angiography and 321 patients had significant stenosis. Among the 321 patients, 195 underwent PCI. Before the matching procedure, patients without PCI had a similar age and sex ratio but a higher rate of risk factors (hypertension, diabetes, chronic renal failure, and prior coronary artery disease), pneumonia, and SYNTAX score than patients without PCI. After propensity score matching, neither in-hospital mortality (13% with PCI vs. 8% without PCI; p = 0.4) nor one-year mortality (24% with PCI vs. 19% without PCI, p = 0.5) significantly differed between the two groups. In this first prospective cohort of post-infectious MI in coronary care units, PCI might not improve short- and long-term prognosis in patients with angiography-proven significant coronary stenosis. If confirmed, these results do not argue for systematic invasive procedures after post-infectious MI.

Coronavirus Disease-2019 (COVID-19) and Cardiovascular Complications

The coronavirus disease-2019 (COVID-19) has become a global pandemic. It has spread to more than 100 countries, and more than 1 million cases have been confirmed. Although coronavirus causes severe respiratory infections in humans, accumulating data have demonstrated cardiac complications and poor outcome in patients with COVID-19. A large percent of patients have underlying cardiovascular disease, and they are at a high risk of developing cardiac complications. The basics of the virus, the clinical manifestations, and the possible mechanisms of cardiac complications in patients with COVID-19 are reviewed. Before an effective vaccine or medicine is available, supportive therapy and identifying patients who are at high risk of cardiac complications are important.

The Relationship Between Aspirin Resistance and Carotid Imaging in Young Patients With ST-Segment Elevated Myocardial Infarction: A Cross-Sectional Study

The presence of carotid atherosclerosis accompanied by coronary artery disease is associated with poor prognosis. A subset of patients who take aspirin continue to have recurrent cardiovascular events, which may be due to aspirin resistance (AR). Also, carotid plaques may cause turbulent flow which in turn may lead to platelet activation and poor antiplatelet response. In our study, we aimed to show the prevalence of AR and its relationship between high-risk carotid images in young patients with ST-segment elevated myocardial infarction (STEMI). In our study, we included 112 patients younger than 45 years with STEMI. Aspirin response test was evaluated 1 hour after aspirin intake using multiplate platelet function analyzer, and carotid ultrasonography has been performed to determine carotid intima–media thickness (CIMT) and the presence of carotid plaque. We identified 30.3% AR in young patients with STEMI. Carotid intima–media thickness (P = .002), carotid plaque (P = .012), and high-risk carotid image (P = .015) values are significantly high in patients who have AR. Independent of other risk factors, the presence of carotid plaque and being in the high-risk carotid group were associated with 3.7 times and 3.2 times increased odds for AR, respectively. In young patients with STEMI, physicians should be careful about AR, especially in patients who have carotid plaque and thicker CIMT.

The impact of infection on mortality in octogenarians who were admitted due to acute coronary syndrome

BACKGROUND

The prevalence of coronary artery disease is on the rise as the life expectancy of the population increases. However, treatment of acute coronary syndrome in the elderly patients has its own problems that have not been thoroughly addressed in the clinical trials. Since these patients are generally fragile and have multiple co-morbidities, the course of acute coronary syndrome can frequently be complicated. Infection, which co-exists either at the initial presentation or is acquired during the hospital stay, is a condition about which there is little published data. Therefore, in our study, we wanted to assess the impact of infection on mortality in octogenarians who have acute coronary syndrome METHODS: We retrospectively analyzed the data of 174 octogenarians who had been admitted to the coronary care unit with acute coronary syndrome. All-cause mortality was defined as the primary endpoint of the study.

RESULTS

Overall 53 octogenarian patients (30.5%) had an infection along with acute coronary syndrome. The mean duration of follow-up was 10 months (1-25 months). Both in-hospital and long-term mortality were higher in these patients (18.9% vs 6.6%, p = 0.01; 52.8% vs 27.5%, p < 0.01; respectively). Kaplan-Meier analysis also showed lower cumulative survival. (p [log-rank] = 0.002). In multivariate Cox regression analysis; undergoing coronary angiography, infection (HR 1.96, 95% CI 1.15-3.34, p = 0.01), left ventricular ejection fraction and maximum C reactive protein levels were found as independent predictors of long-term survival.

CONCLUSION

Infection in octogenarians who were admitted due to acute coronary syndrome was frequent and increased their mortality substantially.

High-sensitive C-reactive protein and dual antiplatelet in intracranial arterial stenosis

Objective

To determine the relationship of high-sensitive C-reactive protein (hsCRP) and the efficacy and safety of dual antiplatelet therapy in patients with and without intracranial arterial stenosis (ICAS) in the Clopidogrel in High-Risk Patients with Acute Non-disabling Cerebrovascular Events (CHANCE) trial.

Methods

A subgroup of 807 patients with both magnetic resonance angiography images and hsCRP measurement was analyzed. Cox proportional hazards models were used to assess the interaction of hsCRP levels with the effects of dual and single antiplatelet therapy.

Results

A total of 358 (44.4%) patients had ICAS and 449 (55.6%) did not. The proportion of patients with elevated hsCRP levels was higher in the ICAS group than in the non-ICAS group (40.2% vs 30.1%, p = 0.003). There was significant interaction between hsCRP and the 2 antiplatelet therapy groups in their effects on recurrent stroke after adjustment for confounding factors in the patients with ICAS (p = 0.012), but not in those without (p = 0.256). Compared with aspirin alone, clopidogrel plus aspirin significantly reduced the risk of recurrent stroke only in the patients with ICAS and nonelevated hsCRP levels (adjusted hazard ratio 0.27; 95% confidence interval 0.11 to 0.69; p = 0.006). Similar results were observed for composite vascular events. No significant difference in bleeding was found.

Conclusions

Presence of both ICAS and nonelevated hsCRP levels may predict better response to dual antiplatelet therapy in reducing new stroke and composite vascular events in minor stroke or high-risk TIA patients. Further large-scale randomized and controlled clinical trials are needed to confirm this finding.

Platelet function variability and non-genetic causes

Dual antiplatelet therapy (DAPT) has been established for the treatment of coronary artery disease, especially in and after acute coronary syndromes, and after coronary interventions. Data suggest that a significant percentage of individuals treated with clopidogrel do not receive the expected therapeutic benefit because of a decreased responsiveness of their platelets, which is caused by several extrinsic and intrinsic mechanisms. The clinical consequence of clopidogrel non-responsiveness is severe cardiovascular complications. Besides genetic variability in response to antiplatelet therapy, non-genetic causes such as drug interactions (proton-pump inhibitors, statins, calcium-channel blockers, coumarine derivates, antibiotics, antimycotics) and co-morbidities (diabetes mellitus, renal failure, obesity) are responsible for this phenomenon. Large clinical trials with standardised laboratory methods and hard clinical endpoints are needed to identify these interactions with clopidogrel and predictors for its non-responsiveness.

Urinary 11-Dehydro-Thromboxane B2 and Mortality in Patients With Stable Coronary Artery Disease

Antiplatelet therapy with aspirin has been shown to reduce adverse outcomes in patients with coronary artery disease (CAD). Aspirin irreversibly inhibits platelet cyclooxygenase-1 and attenuates thromboxane A₂ (TXA₂)-mediated platelet aggregation, but there is variable suppression of cyclooxygenase-1. From a cohort of patients with stable CAD, we performed blinded, detailed chart abstraction, and measured urinary 11-dehydro-thromboxane B₂ (11dhTxB₂), an inactive metabolite of TxA₂ from frozen samples. There were 327 men (73%) and 122 women (27%) with a mean age (±SD) of 67 ± 10 and 65 ± 10 years, respectively. A positive linear trend for age was observed among tertiles of 11dhTxB₂ (p trend = 0.01). Higher proportions of women (p = 0.001), chronic obstructive pulmonary disease (p trend = 0.0003), and heart failure (p trend = 0.003) were observed in the upper tertile of 11dhTxB₂. Sixty-seven patients (14.9%) died over a median follow-up of 1,149 days and 87.5% of the deaths were due to cardiovascular causes. Twenty-six nonsurvivors (38.8%) were treated with P2Y12 receptor antagonists versus 161 survivors (42.2%; p = 0.61). By stepwise Cox proportional hazards analysis, we identified that patients in the middle (hazard ratio 7.14; 95% CI 2.46 to 20.68) and upper tertiles (hazard ratio 9.91; 95% CI 3.45 to 28.50) had higher risks for mortality after adjusting for age and co-morbidities. In conclusion, urinary concentration of 11dhTxB₂ was a strong independent risk factor for all-cause mortality among patients with stable CAD on aspirin therapy and may be a marker for patients with CAD who require more intensive secondary prevention measures.

Serious infections among unselected patients with ST-elevation myocardial infarction treated with contemporary primary percutaneous coronary intervention

BACKGROUND

Contemporary studies assessing the frequency, characteristics, and outcomes of serious infections (SIs) in patients presenting a ST-elevation myocardial infarction are scarce.

METHODS

Prospective cohort of consecutive patients undergoing primary percutaneous coronary intervention (pPCI). Serious infection was defined as the presence of infection that prolonged hospitalization. Community-acquired infection (CAI) was defined by SI diagnosed in the first 72 hours of hospitalization, whereas hospital-acquired infections (HAI) were those diagnosed after 72 hours of hospital admission.

RESULTS

From December 2009 to November 2012, 1,486 patients were included in the analysis. Serious infection was present in 58 (3.9%) individuals; 30 (2%) patients had CAI and 28 (1.9%) patients had HAI. Respiratory tract infection was responsible for 82% of the SI. Patients with SI were older, had more comorbidities, and had worse angiographic results of the pPCI procedure when compared with those without SIs. After multivariable adjustment, SI was associated with an approximately 10-fold risk of 30-day death. Patients with CAI had more often a history of smoking, Killip III/IV on hospital admission, worse pPCI, and angiographic results than did patients with HAI. However, no differences were seen in 30-day major cardiovascular outcomes between patients with CAI and HAI.

CONCLUSION

In a contemporary cohort of unselected ST-elevation myocardial infarction patients representative of the daily practice, SI was uncommon but associated with worse pPCI results and high risk of mortality. The occurrences of CAI or HAI were similar, but CAI patients presented distinctly worse angiographic outcomes than did patients with HAI.

No significant detectable anti-infection effects of aspirin and statins in chronic obstructive pulmonary disease

BACKGROUND

Past studies have shown that aspirin and statins decrease the rate and severity of exacerbation, the rate of hospitalization, and mortality in chronic obstructive pulmonary disease (COPD). Although these studies are relatively new, there is evidence that new therapeutic strategies could prevent exacerbation of COPD.

TRIAL DESIGN

This article examines retrospectively the possibility of using aspirin and statins to prevent exacerbation and infection in patients with COPD.

METHODS

All patients with COPD were identified from hospital charts in the Department of Internal Medicine, Saarland University Medical Center, Germany, between 2004 and 2014.

RESULTS

The study examined 514 medical reports and secured a study population of 300 with COPD. The mean age was 69 ± 10 years (206 men, 68.7%, 95% CI, 63.4-73.9; 94 women, 31.3%, 95% CI, 26.1-36.6). The study results did not show a causal relationship between aspirin and statins and prevention of exacerbation and infection in patients with COPD.

CONCLUSION

In contrast, in this study, the exacerbation and infection rates increased under medication with aspirin and statins (p = 0.008).

Platelet activation is associated with myocardial infarction in patients with pneumonia

BACKGROUND

Troponins may be elevated in patients with pneumonia, but associations with myocardial infarction (MI) and with platelet activation are still undefined.

OBJECTIVES

The aim of this study was to investigate the relationship between troponin elevation and in vivo markers of platelet activation in the early phase of hospitalization of patients affected by community-acquired pneumonia.

METHODS

A total of 278 consecutive patients hospitalized for community-acquired pneumonia, who were followed up until discharge, were included. At admission, platelet activation markers such as plasma soluble P-selectin, soluble CD40 ligand, and serum thromboxane B2 (TxB2) were measured. Serum high-sensitivity cardiac troponin T levels and electrocardiograms were obtained every 12 and 24 h, respectively.

RESULTS

Among 144 patients with elevated high-sensitivity cardiac troponin T, 31 had signs of MI and 113 did not. Baseline plasma levels of soluble P-selectin and soluble CD40 ligand and serum TxB2 were significantly higher in patients who developed signs of MI. Logistic regression analysis showed plasma soluble CD40 ligand (p < 0.001) and soluble P-selectin (p < 0.001), serum TxB2 (p = 0.030), mean platelet volume (p = 0.037), Pneumonia Severity Index score (p = 0.030), and ejection fraction (p = 0.001) to be independent predictors of MI. There were no significant differences in MI rate between the 123 patients (45%) taking aspirin (100 mg/day) and those who were not aspirin treated (12% vs. 10%; p = 0.649). Aspirin-treated patients with MIs had higher serum TxB2 compared with those without MIs (p = 0.005).

CONCLUSIONS

MI is an early complication of pneumonia and is associated with in vivo platelet activation and serum TxB2 overproduction; aspirin 100 mg/day seems insufficient to inhibit thromboxane biosynthesis. (MACCE in Hospitalized Patients With Community-acquired Pneumonia; NCT01773863).

Pneumonia, thrombosis and vascular disease

SUMMARY

An enhanced risk of cardiovascular mortality has been observed after pneumonia. Epidemiological studies have shown that respiratory tract infections are associated with an increased risk of thrombotic-related vascular disease such as myocardial infarction, ischemic stroke and venous thrombosis. Myocardial infarction and stroke have been detected essentially in the early phase of the disease (i.e. within 48 h from hospital admission), with an incidence ranging from as low as 1% to as high as 11%. Age, previous cardiovascular events and high pneumonia severity index were independent predictors of myocardial infarction; clinical predictors of stroke were not identified. Deep venous thrombosis and pulmonary embolism may also occur after pneumonia but incidence and clinical predictors must be defined. The biological plausibility of such an association may be deduced by experimental and clinical studies, showing that lung infection is complicated by platelet aggregation and clotting system activation, as documented by up-regulation of tissue factor and down-regulation of activated protein C. The effect of antithrombotic drugs has been examined in experimental and clinical studies but results are still inconclusive.

Acute pneumonia and the cardiovascular system

Although traditionally regarded as a disease confined to the lungs, acute pneumonia has important effects on the cardiovascular system at all severities of infection. Pneumonia tends to affect individuals who are also at high cardiovascular risk. Results of recent studies show that about a quarter of adults admitted to hospital with pneumonia develop a major acute cardiac complication during their hospital stay, which is associated with a 60% increase in short-term mortality. These findings suggest that outcomes of patients with pneumonia can be improved by prevention of the development and progression of associated cardiac complications. Before this hypothesis can be tested, however, an adequate mechanistic understanding of the cardiovascular changes that occur during pneumonia, and their role in the trigger of various cardiac complications, is needed. In this Review, we summarise knowledge about the burden of cardiac complications in adults with acute pneumonia, the cardiovascular response to this infection, the potential effects of commonly used cardiovascular and anti-infective drugs on these associations, and possible directions for future research.

Spontaneous platelet aggregation evaluated by laser light scatter in patients with type 2 diabetes: effects of short-term improved glycemic control and adiponectin

Spontaneous platelet aggregation (SPA) is enhanced in patients with type 2 diabetes. Adiponectin may inhibit platelet aggregation. The aims of the current study were to identify factors associated with in vitro SPA measured by a laser light scattering method and to investigate the effects of short-term glycemic control and adiponectin on SPA. In study 1, we investigated platelet aggregation in 20 healthy control subjects and 82 patients with type 2 diabetes. In study 2, we evaluated the changes of SPA and serum high-molecular-weight (HMW) adiponectin after 2 weeks of improved glycemic control in 20 hospitalized diabetic patients. In study 3, using washed platelets from 10 healthy subjects, in vitro SPA was measured over 15 min in the absence or presence of recombinant adiponectin (20 μg/mL). Platelet aggregation was assessed with a laser light scatter aggregometer that measured the size of platelet aggregates. SPA was defined as formation of small aggregates under constant stirring in the absence of any agonists. The area under the curve was calculated for SPA and also for agonist-induced small, medium, and large aggregates. SPA was increased in diabetic patients compared with control subjects. In diabetic patients, SPA was correlated positively with plasma fibrinogen, fasting plasma glucose, glycated albumin, and high-sensitivity C-reactive protein. A stepwise multivariate analysis showed that plasma fibrinogen was the strongest independent determinant of SPA in diabetic patients. In 20 diabetic patients, SPA decreased significantly after 2 weeks of glycemic control. A significant negative correlation was found between changes of SPA and those of HMW adiponectin during treatment. The in vitro study showed that adiponectin inhibited the spontaneous aggregation of washed platelets. In conclusion, hyperfibrinogenemia and hyperglycemia are associated independently with SPA in patients with type 2 diabetes. SPA is reduced after even short-term improvement of glycemic control and adiponectin also inhibits SPA directly.

Platelet activation in obesity and metabolic syndrome

Obesity is associated with increased cardiovascular disease. Metabolic syndrome (MS) identifies substantial additional cardiovascular risk beyond the individual risk factors, and is a powerful predictor of cardiovascular events even regardless of body mass index, thus suggesting a common downstream pathway conferring increased cardiovascular risk. Platelet hyper-reactivity/activation plays a central role to accelerate atherothrombosis and is the result of the interaction among the features clustering in obesity and MS: insulin resistance, inflammation, oxidative stress, endothelial dysfunction. Interestingly, the same pathogenic events largely account for the less-than-expected response to antiplatelet agents, namely low-dose aspirin. The proposed explanations for this phenomenon, besides underdosing of drug and/or reduced bioavailability, subsequent to excess of adipose tissue, include enhanced platelet turnover, leading to unacetylated COX-1 and COX-2 in newly formed platelets as a source of aspirin-escaping thromboxane formation; extraplatelet sources of thromboxane, driven by inflammatory triggers; and enhanced lipid peroxidation, activating platelets with a mechanism bypassing COX-1 acetylation or limiting COX-isozyme acetylation by aspirin. This review will address the complex interactions between platelets and the pathogenic events occurring in obesity and MS, trying to translate this body of mechanistic information into a clinically relevant read-out, in order to establish novel strategies in the prevention/treatment of atherothrombosis.

Inflammation as a marker for the prediction of internal carotid artery restenosis following eversion endarterectomy--evidence from clinical studies

The role of inflammation is well established in the pathogenesis of atherosclerosis and an increased level of circulating inflammatory markers may predict the future risk of atherosclerosis progression and plaque rupture. C-reactive protein (CRP) identification by hypersensitive methods (high-sensitivity CRP [hsCRP]) has become a clinical and laboratory inflammation marker. Carotid endarterectomy (CEA) is a well-established procedure for carotid stenosis treatment which can reduce stroke rate. Internal carotid artery (ICA) restenosis reduction may be prevented by the anti-inflammatory effect of statins. This review considers the recent findings on the presence of hsCRP and C3 complement concentration and inflammatory plaque composition as well as their effects on ICA restenosis rate, following eversion CEA with emphasis on human studies.

Relation of aspirin failure to clinical outcome and to platelet response to aspirin in patients with acute myocardial infarction

Aspirin failure, defined as occurrence of an acute coronary syndrome despite aspirin use, has been associated with a higher cardiovascular risk profile and worse prognosis. Whether this phenomenon is a manifestation of patient characteristics or failure of adequate platelet inhibition by aspirin has never been studied. We evaluated 174 consecutive patients with acute myocardial infarction. Of them, 118 (68%) were aspirin naive and 56 (32%) were regarded as having aspirin failure. Platelet function was analyzed after ≥72 hours of aspirin therapy in all patients. Platelet reactivity was studied by light-transmitted aggregometry and under flow conditions. Six-month incidence of major adverse coronary events (death, recurrent acute coronary syndrome, and/or stroke) was determined. Those with aspirin failure were older (p = 0.002), more hypertensive (p <0.001), more hyperlipidemic (p <0.001), and more likely to have had a previous cardiovascular event and/or procedure (p <0.001). Cumulative 6-month major adverse coronary events were higher in the aspirin-failure group (14.3% vs 2.5% p <0.01). Patients with aspirin failure had lower arachidonic acid-induced platelet aggregation (32 ± 24 vs 45 ± 30, p = 0.003) after aspirin therapy compared to their aspirin-naive counterparts. However, this was not significant after adjusting for differences in baseline characteristics (p = 0.82). Similarly, there were no significant differences in adenosine diphosphate-induced platelet aggregation and platelet deposition under flow conditions. In conclusion, our results suggest that aspirin failure is merely a marker of higher-risk patient profiles and not a manifestation of inadequate platelet response to aspirin therapy.

Antiplatelet resistance in stroke

Although the exact prevalence of antiplatelet resistance in ischemic stroke is not known, estimates about the two most widely used antiplatelet agents - aspirin and clopidogrel - suggest that the resistance rate is high, irrespective of the definition used and parameters measured. Inadequate antiplatelet responsiveness correlates with an increased risk of recurrent ischemic vascular events in patients with stroke and acute coronary syndrome. It is not currently known whether tailoring antiplatelet therapy based on platelet function test results translates into a more effective strategy to prevent secondary vascular events after stroke. Large-scale clinical trials using a universally accepted definition and standardized measurement techniques for antiplatelet resistance are needed to demonstrate whether a 'platelet-function test-guided antiplatelet treatment' strategy translates into improved stroke care. This article gives an overview of the clinical importance of laboratory antiplatelet resistance, describes the challenges for platelet-function test-guided antiplatelet treatment and discusses practical issues about the management of patients with aspirin and/or clopidogrel resistance.

Inflammation-related effects of adjuvant influenza A vaccination on platelet activation and cardiac autonomic function

BACKGROUND

Inflammation, platelet reactivity and cardiac autonomic dysfunction increase the risk of cardiovascular events, but the relationships between these prognostic markers are poorly defined. In this study, we investigated the effect of an inflammatory stimulus (influenza A vaccine) on platelet activation and cardiac autonomic function.

METHODS

We measured serum C-reactive protein (CRP) and interleukin-6 levels, monocyte-platelet aggregates (MPAs) and monocyte/platelet receptor expression before and after adjuvant influenza A vaccination in 28 patients with type II diabetes (mean age 62.1 ± 8 years, 18 men). Twenty-four-hour Holter electrocardiogram was recorded 24 h before and after vaccination; heart rate variability (HRV) was assessed as a measure of cardiac autonomic function.

RESULTS

Inflammatory cytokines, MPA formation and monocyte/platelet receptor expression increased after vaccination. CRP was 2.6 ± 2.8 and 7.1 ± 5.7 mg L⁻¹ 48 h before and after vaccination, respectively (P < 0.0001). HRV parameters decreased after vaccination compared to baseline, with very low-frequency amplitude showing the most significant change (34.6 ± 11.8 and 31.0 ± 10.2 ms 48 h before and after vaccination, respectively; P = 0.002). A significant correlation was found between percentage changes in CRP levels and in most HRV variables, with the most significant correlations between changes in CRP levels and changes in standard deviation of all normal RR intervals (r = 0.43; P = 0.02).

CONCLUSIONS

Together with an inflammatory reaction, influenza A vaccine induced platelet activation and sympathovagal imbalance towards adrenergic predominance. Significant correlations were found between CRP levels and HRV parameters, suggesting a pathophysiological link between inflammation and cardiac autonomic regulation. The vaccine-related platelet activation and cardiac autonomic dysfunction may transiently increase the risk of cardiovascular events.

Aspirin and antiplatelet agent resistance: implications for prevention of secondary stroke

Oral antiplatelet drugs, including aspirin, clopidogrel and extended-release dipyridamole, are widely prescribed for the secondary prevention of vascular events, including stroke. Despite the benefits of antiplatelet therapy, 10−20% of patients experience a recurrent vascular event while taking antiplatelet medication. This article discusses the concept of antiplatelet resistance in general, focusing on aspirin resistance in particular, as a poorly defined cause of recurrent vascular events. Factors such as the lack of a standardized method to diagnose aspirin resistance and a poor clinical correlation with laboratory assays make the treatment of aspirin nonresponders difficult. In addition, there are confounding conditions such as diabetes mellitus that can affect aspirin resistance and determine a different course of treatment for these patients. Other antiplatelet options may also have resistant subpopulations; thus, alternative strategies for the secondary stroke patient must be explored.

Clinical importance of aspirin and clopidogrel resistance

Aspirin and clopidogrel are important components of medical therapy for patients with acute coronary syndromes, for those who received coronary artery stents and in the secondary prevention of ischaemic stroke. Despite their use, a significant number of patients experience recurrent adverse ischaemic events. Interindividual variability of platelet aggregation in response to these antiplatelet agents may be an explanation for some of these recurrent events, and small trials have linked "aspirin and/or clopidogrel resistance", as measured by platelet function tests, to adverse events. We systematically reviewed all available evidence on the prevalence of aspirin/clopidogrel resistance, their possible risk factors and their association with clinical outcomes. We also identified articles showing possible treatments. After analyzing the data on different laboratory methods, we found that aspirin/clopidogrel resistance seems to be associated with poor clinical outcomes and there is currently no standardized or widely accepted definition of clopidogrel resistance. Therefore, we conclude that specific treatment recommendations are not established for patients who exhibit high platelet reactivity during aspirin/clopidogrel therapy or who have poor platelet inhibition by clopidogrel.

Aspirin and clopidogrel resistance: methodological challenges and opportunities

Antiplatelet drug resistance is one of the urgent issues in current cardiovascular medicine. Many platelet function tests have been used to define responsiveness of patients with cardiovascular disease to aspirin and clopidogrel. In most studies, cut-off values of platelet function tests for defining responsiveness to antiplatelets were chosen arbitrarily. Different tests provided wide-ranging figures of the prevalence of aspirin and clopidogrel resistance, suggesting poor correlation between currently available platelet function tests. Measurement of platelet size seems to be a promising approach for monitoring antiplatelet drug therapy. This commentary highlights some limitations of studies on aspirin and clopidogrel resistance in patients undergoing coronary interventions.

Relationship between baseline inflammatory markers, antiplatelet therapy, and adverse cardiac events after percutaneous coronary intervention: an analysis from the clopidogrel for the reduction of events during observation trial

BACKGROUND

We evaluated patients undergoing percutaneous coronary intervention to assess the predictive value of high-sensitivity C-reactive protein (hs-CRP) and pregnancy-associated plasma protein-A (PAPP-A) on adverse cardiac outcomes and the effect of antiplatelet therapy on these outcomes.

METHODS AND RESULTS

Baseline blood samples were available on 1468 CREDO (Clopidogrel for the Reduction of Events During Observation) patients for hs-CRP testing and 1096 patients for PAPP-A testing. The 1-year primary end point was the composite incidence of death, myocardial infarction, or stroke. Patients in the highest 2 tertiles of hs-CRP had more events compared with the lowest tertile (11.4% versus 6.4%, P=0.003). Treatment with clopidogrel reduced the 1-year composite end point for patients in the highest 2 tertiles of hs-CRP (9.1% clopidogrel versus 13.5% placebo, P=0.04) but not in the lowest tertile. Elevated PAPP-A levels were associated with a trend toward more events at 1 year that did not reach statistical significance. Patients in the highest 2 tertiles of PAPP-A randomized to clopidogrel had fewer events (7.3% clopidogrel versus 13.1% placebo, P=0.01), but no benefit was seen in the lowest tertile. A 46% risk reduction with randomization to clopidogrel was seen in patients in the highest 2 tertiles of both biomarkers (8.7% versus 16.2%, P=0.02).

CONCLUSIONS

Patients undergoing nonurgent percutaneous coronary intervention who have elevated hs-CRP and PAPP-A have an increased incidence of adverse cardiovascular events. The clinical benefit of adding clopidogrel to aspirin seems greater in those with increased levels of these inflammatory biomarkers.

Association of level of kidney function and platelet aggregation in acute myocardial infarction

BACKGROUND

Decreased kidney function has been established as an important risk factor in patients presenting with acute coronary syndrome. In acute coronary syndrome, increased platelet aggregation is associated with vascular complications. The aim of this study is to examine whether decreased kidney function is associated with altered platelet function in patients presenting with acute myocardial infarction.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

413 patients presenting with acute myocardial infarction admitted to the cardiac intensive care unit at Ostersund Hospital, Ostersund, Sweden.

PREDICTORS

Glomerular filtration rate less than 60 mL/min/1.73 m(2) estimated from serum cystatin C level, comorbidity, medications, and markers of inflammation and hemostasis.

OUTCOMES & MEASUREMENTS

Platelet aggregation was assessed by measuring the formation of small platelet aggregates (SPAs) by using a laser light scattering method. A greater SPA level indicates greater platelet aggregation. Platelet aggregation analysis was performed on days 1, 2, 3, and 5 in-hospital.

RESULTS

We observed a significant increase in platelet aggregation during the first 3 days in the hospital regardless of kidney function (P < 0.001). Platelet aggregation was more pronounced in patients with estimated glomerular filtration rate less than 60 mL/min/1.73 m(2) on day 2 (SPA count, 65,000 versus 47,000; P = 0.01) and day 3 (SPA count, 77,000 versus 52,000; P = 0.02). In a multiple linear regression analysis, decreased kidney function was no longer significantly associated with increased platelet aggregation. Older age, greater plasma fibrinogen level, and diabetes mellitus were associated with increased platelet aggregation in the multivariable model.

LIMITATIONS

During the study period, 78 patients presenting with acute myocardial infarction were not eligible for inclusion. Differences in treatment with antiplatelet medication between the 2 groups might have affected our findings.

CONCLUSIONS

Platelet aggregation increases during the first days after acute myocardial infarction regardless of kidney function. There is no difference in platelet aggregation in patients according to level of kidney function.

Aspirin resistance

The development of adverse cardiovascular events despite aspirin use has established an interest in a possible resistance to the drug. Several definitions have been set and various laboratory testing modalities are available. This has led to a wide range of prevalence reports in different clinical entities. The etiologic mechanism has been related to clinical, genetic, and other miscellaneous factors. The clinical implications of this phenomenon are significant and warrant concern. Management strategies are currently limited to dosing alteration and introduction of other anitplatelet agents. However, these measures have not met the expected efficacy or safety.

Leukocyte count is associated with increased platelet reactivity and diminished response to aspirin in healthy individuals with a family history of coronary artery disease

BACKGROUND

Markers of systemic inflammation, including blood leukocyte count, are associated with increased cardiovascular risk, but the mechanisms underlying this association are unclear. Leukocytes may promote platelet reactivity and thrombus formation, providing a basis for increased risk, but a relation between leukocyte count and platelet function has not been studied.

METHODS

We evaluated the relation of blood leukocyte count, C-reactive protein (CRP), and interleukin-6 (IL-6) to platelet aggregation to collagen, ADP and arachidonic acid, and to urinary excretion of 11-dehydro thromboxane B2. Studies were conducted in 1600 individuals (45.0+/-12.9 years, 42.7% male) at risk for coronary artery disease (CAD) before and after low dose aspirin.

RESULTS

At baseline, platelet reactivity increased with increasing quartile of leukocyte count (median counts for each quartile were normal) for all measures of platelet function (P<0.0001). These relations were unchanged by aspirin. The relation between leukocyte count and each measure of platelet reactivity remained significant (P<0.05) after multivariable adjustment for CRP, IL-6, cardiac risk factors, hematologic variables, and platelet thromboxane production. CRP and IL-6 were independently associated with few measures of platelet reactivity.

CONCLUSIONS

Increasing quartile of leukocyte count, even within the normal range, is associated with increasing platelet reactivity in individuals at risk for CAD. This relationship is not altered by aspirin and is independent of inflammatory markers and platelet thromboxane production. Additional studies are needed to determine the mechanism(s) for this association and therapies to reduce cardiovascular risk in patients with elevated leukocyte counts.

Platelet reactivity and response to aspirin in subjects with the metabolic syndrome

BACKGROUND

Metabolic syndrome (MS) is associated with a prothrombotic state and predicts the subsequent development of type 2 diabetes mellitus. We hypothesized that similar to diabetes, subjects with MS may have increased platelet reactivity, and reduced response to aspirin. We, therefore, compared platelet reactivity and response to aspirin among subjects with MS and healthy volunteers.

METHODS

Fifty subjects with MS, defined by Adult Treatment Panel III criteria (age 44+/-9 years, 80% women, body mass index 35+/-8 kg/m2) were compared to 50 healthy controls who met none of the MS criteria (age 40+/-7 years, 80% women, body mass index: 24+/-3 kg/m2). Blood samples were taken before and 24 hours after 325 mg aspirin (single dose). Platelet function was evaluated by aggregation in response to 1.5 mmol/L arachidonic acid, 1 microg/mL collagen, and 5 and 20 micromol/L adenosine diphosphate; the VerifyNow Aspirin assay (Accumetrics Inc, San Diego, CA); Impact-R Cone and Plate(let) Analyzer (shear-dependent test) (DiaMed, Cresier, Switzerland) and flow cytometric determination of P-selectin expression and activated glycoprotein IIb/IIIa expression; and reticulated platelets (reflecting platelet turnover).

RESULTS

Subjects with MS had higher baseline P-selectin levels (14.5+/-5 vs 11.3+/-4 mean fluorescence intensity, P=.002), reticulated platelets (2.8%+/-3% vs 1.2%+/-1%, P=.04) and platelet deposition under flow (Impact-R 7.5%+/-2% vs 5.9%+/-2%, P=.003). Subjects with MS also had lower response to aspirin, as evaluated by the change in all platelet aggregation assays and the VerifyNow score.

CONCLUSIONS

Subjects with MS appear to have increased baseline platelet reactivity and turnover and a lower antiplatelet response to aspirin. Further research is required to elucidate platelet properties in subjects with MS and find ways to modify them.

The role of aspirin in cardiovascular prevention: implications of aspirin resistance

Aspirin is well recognized as an effective antiplatelet drug for secondary prevention in subjects at high risk of cardiovascular events. However, most patients receiving long-term aspirin therapy still remain at substantial risk of thrombotic events due to insufficient inhibition of platelets, specifically via the thromboxane A2 pathway. Although the exact prevalence is unknown, estimates suggest that between 5.5% and 60% of patients using this drug may exhibit a degree of "aspirin resistance," depending upon the definition used and parameters measured. To date, only a limited number of clinical studies have convincingly investigated the importance of aspirin resistance. Of these, few are of a sufficient scale, well designed, and prospective, with aspirin used at standard doses. Also, most studies do not sufficiently address the issue of noncompliance to aspirin as a frequent, yet easily preventable cause of resistance to this antiplatelet drug. This review article provides a comprehensive overview of aspirin resistance, discussing its definition, prevalence, diagnosis, and therapeutic approaches. Moreover, the clinical implications of aspirin resistance are explored in various cardiovascular disease states, including diabetes mellitus, hypertension, heart failure, and other similar disorders where platelet reactivity is enhanced.

Aspirin resistance in atherosclerosis

Clinically, aspirin resistance is defined as the failure of aspirin therapy to prevent an acute vascular thrombotic event despite regular intake of appropriate doses. In the laboratory, aspirin resistance encompasses the drug's failure to attain a particular level of platelet inhibition. From a clinical standpoint, the inability of aspirin to prevent a thrombotic event, despite appropriate cyclooxygenase-1 inhibition, implies the involvement of other factors. Evidence is emerging that aspirin resistance, as defined by residual platelet activity, merely reflects an individual's enhanced basal platelet function and suggests a hereditary component. Due to the multifactorial nature of cardiovascular disease, it is likely that a single therapy like aspirin cannot fully treat and prevent all thrombotic complications in the setting of atherosclerosis.