Immature platelets and cardiovascular events in patients with stable coronary artery disease.

Many patients with coronary artery disease (CAD) have reduced the effect of aspirin, which may partly be explained by immature platelets. We aimed to investigate whether immature platelet markers can predict cardiovascular events in a large cohort of stable CAD patients. A total of 900 stable CAD patients were included and followed for a median of 3 years. We measured markers of immature platelets (platelet count, immature platelet count, immature platelet fraction, mean platelet volume, platelet distribution width, platelet mass, and thrombopoietin) using automated flow cytometry and studied their relation to cardiovascular events. Our primary endpoint was a composite of acute myocardial infarction (MI), ischemic stroke, and cardiovascular death. A composite of MI, ischemic stroke, stent thrombosis and all-cause mortality was analyzed as a secondary endpoint. We found no difference in immature platelet markers between CAD patients with or without cardiovascular events. Regression analysis using hazards rates showed that markers of immature platelets did not have any predictive value for endpoints (p-values >.05). Markers of immature platelets did not predict future cardiovascular events during a 3-year follow-up period in CAD patients. This suggests that immature platelets measured in a stable phase does not have a major role in predicting future cardiovascular events.

What is the context? Many patients with coronary artery disease (CAD) have reduced antiplatelet effect of aspirinThe reduced antiplatelet effect of aspirin is most likely multifactorial and may partly be explained by immature plateletsWhat is new? In a cohort of 900 stable CAD patients, we measured markers of immature platelets and studied their relation to cardiovascular events during a 3-year follow-upOur study demonstrated that markers of immature platelets did not predict cardiovascular events in our cohortWhat is the impact? The findings from the present study suggest that immature platelets, measured in a stable phase, do not have a major role in predicting future cardiovascular events in CAD patients.

Neutrophil gelatinase-associated lipocalin as a risk marker in cardiovascular disease.

Neutrophil gelatinase-associated lipocalin (NGAL) is a promising diagnostic biomarker of early acute kidney injury. Increasing evidence suggests that NGAL may also be involved in inflammatory processes in cardiovascular disease. NGAL modulates the enzymatic activity of matrix metalloproteinase-9 (MMP-9), which is an important mediator of plaque instability in atherosclerosis. The complex formation between NGAL and MMP-9 therefore suggests that NGAL might play a role in progression of atherothrombotic disease. This review summarises current data on NGAL in atherosclerosis, acute myocardial infarction, and heart failure.

Thrombopoietin and platelet aggregation in patients with stable coronary artery disease.

Thrombopoietin (TPO) may facilitate platelet activation and aggregation. However, data on the impact of TPO on platelet aggregation in patients with stable coronary artery disease (CAD) are scarce. We aimed to investigate associations between TPO and platelet aggregation and activation in patients with stable coronary artery disease (CAD). We studied 900 stable CAD patients. Serum TPO was assessed by ELISA. Platelet aggregation was evaluated using the Multiplate Analyzer (agonists: arachidonic acid [AA] and collagen) and the VerifyNow Aspirin Assay. Platelet activation was evaluated by soluble (s)P-selectin. Cyclooxygenase-1 inhibition was evaluated by serum thromboxane B2 (TXB2). We found that TPO correlated weakly with platelet aggregation evaluated by Multiplate using AA (r = -0.09, p = 0.01) and collagen as agonists (r = -0.03, p = 0.43) and by VerifyNow (r = 0.07, p = 0.03). We found no correlation between TPO and sP-selectin (r = -0.01, p = 0.70). Independent predictors of AA-induced platelet aggregation by Multiplate included high levels of sP-selectin and serum TXB2, high platelet count, increasing age and body mass index, female sex, and active smoking. Independent predictors of TPO included low AA-induced platelet aggregation by Multiplate, high levels of hs-CRP, active smoking, and high platelet aggregation evaluated by VerifyNow. In conclusion, TPO levels did not correlate with platelet activation and only weak associations were found between TPO and platelet aggregation, suggesting that TPO did not substantially facilitate platelet aggregation in stable CAD patients.

Syncope and Total Atrioventricular Block Associated With Alcohol Consumption in a Healthy Young Man.

Association between alcohol intake and atrioventricular block is rare. This case describes a previously healthy 27-year-old man experiencing syncopes preceded by moderate alcohol intake. An implantable loop recorder demonstrated episodes of total atrioventricular block coinciding with an additional syncope after alcohol intake, resulting in pacemaker implantation. (Level of Difficulty: Intermediate.).

Heart transplantation after acute myocardial infarction due to focal coronary Takayasu arteritis: a case report.

Background: Takayasu arteritis is a chronic vasculitis of unknown aetiology primarily affecting medium to large arteries, particularly the aorta and arch vessels, and is predominantly seen in younger patients. Coronary artery involvement has been reported in 10-45% of autopsy cases, but isolated coronary Takayasu arteritis is extremely rare. Case summary: This case report describes the course of a previously healthy 22-year-old woman who suffered an acute myocardial infarction complicated by cardiogenic shock requiring temporary mechanical support subsequently urgent heart transplantation. The patient was bridged to transplant by the use of veno-arterial extracorporeal membrane oxygenation (VA-ECMO). The explanted heart showed evidence of Takayasu arteritis in the left coronary artery. Discussion: The case illustrates the importance of VA-ECMO treatment for cardiogenic shock, the importance of the Scandiatransplant collaboration for urgent organ allocation and the diagnostic difficulties associated with Takayasu arteritis.

Expression of microRNA Predicts Cardiovascular Events in Patients with Stable Coronary Artery Disease.

BACKGROUND: New biomarkers are warranted to identify patients with coronary artery disease (CAD) at high risk of recurrent cardiovascular events. It has been reported that the expression of microRNAs (miRs) may influence the development of CAD. OBJECTIVES: We aimed to investigate whether the expression of selected candidate miRs is a predictor of cardiovascular events in a cohort of stable CAD patients. METHODS: We performed a single-center prospective study of 749 stable CAD patients with a median follow-up of 2.8 years. We investigated the expression of nine candidate miRs and their relation to cardiovascular events in this cohort. The primary endpoint was the composite of nonfatal myocardial infarction (MI), stent thrombosis (ST), ischemic stroke, and cardiovascular death. The composite of nonfatal MI and ST was analyzed as a secondary endpoint. Furthermore, nonfatal MI, ST, ischemic stroke, and all-cause mortality were analyzed as individual endpoints. RESULTS: Employing receiver operating characteristic curves, it was shown that compared with traditional cardiovascular risk factors alone, combining the expression of miR-223-3p with existing traditional cardiovascular risk factors increased the predictive value of ST (area under the curve: 0.88 vs. 0.77, p = 0.04), the primary composite endpoint (0.65 vs. 0.61, p = 0.049), and the secondary endpoint of the composite of nonfatal MI and ST (0.68 vs. 0.62, p = 0.04). CONCLUSION: Among patients with CAD, adding miR-223-3p expression to traditional cardiovascular risk factors may improve prediction of cardiovascular events, particularly ST. Clinical trials confirming these findings are warranted.

Real-World Experience with Cangrelor as Adjuvant to Percutaneous Coronary Intervention: A Single-Centre Observational Study.

Background: Reversible P2Y12 inhibition can be obtained with cangrelor administered intravenously. More experience with cangrelor use in acute PCI with unknown bleeding risk is needed. Objectives: To describe real-world use of cangrelor including patient and procedure characteristics and patient outcomes. Methods: We performed a single-centre, retrospective, and observational study including all patients treated with cangrelor in relation to percutaneous coronary intervention at Aarhus University Hospital during the years 2016, 2017, and 2018. We recorded procedure indication and priority, the indications for cangrelor use, and patient outcomes within the first 48 hours after initiation of cangrelor treatment. Results: We treated 991 patients with cangrelor in the study period. Of these, 869 (87.7%) had an acute procedure priority. Among acute procedures, patients were mainly treated for STEMI (n = 723) and the remaining were treated for cardiac arrest and acute heart failure. Use of oral P2Y12 inhibitors prior to percutaneous coronary intervention was rare. Fatal bleeding events (n = 6) were only observed among patients undergoing acute procedures. Stent thrombosis was observed in two patients receiving acute treatment for STEMI. Thus, cangrelor can be used in relation to PCI under acute circumstances with advantages in terms of clinical management. The benefits and risks, in terms of patient outcomes, should ideally be assessed in randomized trials.

Association of whole blood microRNA expression with platelet function and turnover in patients with coronary artery disease.

INTRODUCTION: The risk of recurrent cardiovascular events in patients with coronary artery disease (CAD) is determined by multiple factors including platelet function and turnover. MicroRNAs (miRs) may regulate both platelet function and turnover. We aimed to identify candidate miRs associating with platelet function and turnover in a cohort of stable CAD patients. Furthermore, we retrieved information on binding targets of the candidate miRs to obtain a more comprehensive biological insight into miR regulation of platelet function and turnover. METHODS: Based on existing literature and a pilot study, we identified nine candidate miRs. Subsequently, we investigated the expression of the candidate miRs in whole blood and their relation to platelet function and turnover in 749 CAD patients. Platelet function was analysed using impedance aggregometry, optical aggregometry and serum thromboxane B2 measurements. Platelet turnover markers (immature platelet count, immature platelet fraction and mean platelet volume) were measured using monochromatic automated flow cytometry. RESULTS: Expression of miR-93-5p, miR-126-3p, miR-150-5p, miR-423-3p and miR-1180-3p showed negative correlations with platelet function (p-values from <0.0001 to 0.0006, rho from -0.13 to -0.36). In addition, expression of miR-423-3p showed negative correlation with platelet turnover markers (p-values from 0.001 to 0.004, rho from -0.11 to -0.12). CONCLUSIONS: We identified several novel miRs that may regulate platelet function and turnover, thereby contributing to the increased risk of recurrent cardiovascular events in CAD patients.

The ABO Locus is Associated with Increased Fibrin Network Formation in Patients with Stable Coronary Artery Disease.

BACKGROUND: The ABO locus has been associated with increased risk of myocardial infarction (MI) in patients with coronary artery disease (CAD), but the underlying mechanisms are unknown. As altered fibrin clot structure has been demonstrated to predict MI in CAD patients, we examined the association between the ABO risk variant and fibrin clot properties, and investigated the effects of other CAD-associated risk variants. METHODS: We included 773 stable CAD patients. Patients were genotyped for 45 genome-wide CAD risk variants, including rs495828 at the ABO locus. We used a genetic risk score (GRS) for CAD calculated as the weighted sum of the number of risk alleles based on all 45 variants. Fibrin clot properties were evaluated using a turbidimetric assay. We studied clot maximum absorbance, a measure of clot density and fiber thickness, together with clot lysis time, an indicator of fibrinolysis potential. RESULTS: The rs495828 risk allele was present in 13.2% of patients and associated with higher clot maximum absorbance (adjusted effect size per risk allele: 1.05 [1.01 - 1.09], p = 0.01) but not with clot lysis time (p = 0.97). The rs12936587 (p = 0.04), rs4773144 (p = 0.02), and rs501120 (p = 0.04) were associated with clot lysis time; however, after Bonferroni correction, no significant associations were found between any of the remaining 44 CAD-associated variants and fibrin clot properties. The GRS was not associated with fibrin clot properties (p-values > 0.05). CONCLUSION: The ABO risk allele was associated with a more compact fibrin network in stable CAD patients, which may represent a mechanism for increased MI risk in ABO risk variant carriers.

[Risk of recurrence and duration of anticoagulant treatment after deep venous thromboembolism and pulmonary embolism].

If anticoagulant therapy is stopped, the risk of recurrence after unprovoked venous thromboembolism is high. After anticoagulant treatment for at least three months, the indication for prolonging therapy should be decided after thorough evaluation of individual risk factors for recurrence and bleeding. Clinical parameters, imaging modalities and D-dimer levels can guide this decision. The lower risk of bleeding on non-vitamin K-antagonist oral anticoagulants compared to warfarin is expected to increase the number of patients on extended treatment, but costs and patients' preferences should be considered.

The ABO locus is associated with increased platelet aggregation in patients with stable coronary artery disease.

BACKGROUND: Genome-wide association studies of patients with coronary artery disease (CAD) suggest that several risk loci increase the risk of CAD and myocardial infarction (MI) equally. In contrast, the ABO locus is stronger associated with MI than with CAD, but the underlying mechanisms are unknown. PURPOSE: To investigate the association between the ABO risk variant and platelet activation and aggregation. Moreover, to explore the effects of other CAD-associated risk variants. METHODS: We included 879 stable CAD patients receiving low-dose aspirin. All patients were genotyped for 45 genome-wide significant CAD risk variants, including rs495828 at the ABO locus. A genetic risk score (GRS) was calculated to assess the combined risk of all genetic variants. Serum soluble P-selectin (sP-selectin) and thromboxane B2 were used as measures of platelet activation, and platelet aggregation was assessed by multiple electrode aggregometry (MEA) using arachidonic acid and collagen as agonists and VerifyNow. RESULTS: The rs495828 CAD risk allele was associated with higher MEA platelet aggregation; arachidonic acid: 14.9% (6.7-23.7%, p = 0.0002) higher AUC (Area Under aggregation Curve) per risk allele, and collagen: 13.1% (5.8%-20.9%, p = 0.0003). Conversely, sP-selectin levels were 7.5% (3.1%-11.7%, p = 0.001) lower per risk allele. Rs495828 genotypes were not associated with aggregation assessed by VerifyNow (p = 0.30) or S-thromboxane B2 levels (p = 0.98). None of the remaining variants or the GRS were associated with platelet activation or aggregation. CONCLUSIONS: The ABO risk allele was associated with increased platelet aggregation as assessed by MEA. This finding may contribute to explain the increased MI risk in ABO risk variant carriers.

Reduced Antiplatelet Effect of Aspirin Does Not Predict Cardiovascular Events in Patients With Stable Coronary Artery Disease.

BACKGROUND: Increased platelet aggregation during antiplatelet therapy may predict cardiovascular events in patients with coronary artery disease. The majority of these patients receive aspirin monotherapy. We aimed to investigate whether high platelet-aggregation levels predict cardiovascular events in stable coronary artery disease patients treated with aspirin. METHODS AND RESULTS: We included 900 stable coronary artery disease patients with either previous myocardial infarction, type 2 diabetes mellitus, or both. All patients received single antithrombotic therapy with 75 mg aspirin daily. Platelet aggregation was evaluated 1 hour after aspirin intake using the VerifyNow Aspirin Assay (Accriva Diagnostics) and Multiplate Analyzer (Roche; agonists: arachidonic acid and collagen). Adherence to aspirin was confirmed by serum thromboxane B2. The primary end point was the composite of nonfatal myocardial infarction, ischemic stroke, and cardiovascular death. At 3-year follow-up, 78 primary end points were registered. The primary end point did not occur more frequently in patients with high platelet-aggregation levels (first versus fourth quartile) assessed by VerifyNow (hazard ratio: 0.5 [95% CI, 0.3-1.1], P=0.08) or Multiplate using arachidonic acid (hazard ratio: 1.0 [95% CI, 0.5-2.1], P=0.92) or collagen (hazard ratio: 1.4 [95% CI, 0.7-2.8], P=0.38). Similar results were found for the composite secondary end point (nonfatal myocardial infarction, ischemic stroke, stent thrombosis, and all-cause death) and the single end points. Thromboxane B2 levels did not predict any end points. Renal insufficiency was the only clinical risk factor predicting the primary and secondary end points. CONCLUSIONS: This study is the largest to investigate platelet aggregation in stable coronary artery disease patients receiving aspirin as single antithrombotic therapy. We found that high platelet-aggregation levels did not predict cardiovascular events.

A genetic risk score predicts cardiovascular events in patients with stable coronary artery disease.

BACKGROUND: Genetic risk scores (GRSs) may predict cardiovascular risk in community-based populations. However, studies investigating the association with recurrent cardiovascular events in patients with established coronary artery disease (CAD) are conflicting. METHODS: We genotyped 879 patients with high-risk stable CAD and created a GRS based on 45 single nucleotide polymorphisms previously reported to be associated with CAD in genome-wide association studies. Patients were categorised into high or low GRS according to the median GRS and followed for recurrent cardiovascular events using national Danish registries. The primary endpoint was a composite of myocardial infarction, coronary revascularisation, and cardiovascular death. RESULTS: Median (interquartile range) follow-up time was 2.8 (2.4-3.8)years. The cumulative incidence proportions of the primary endpoint at 1 and 3years were 6.4% and 11.5% in high-GRS patients vs. 2.5% and 7.3% in low-GRS patients. The corresponding relative risks were 2.56 (95% confidence interval (CI) 1.29-5.07), and 1.57 (95% CI 1.02-2.44). The adjusted hazard ratio (HR) of the primary endpoint was 1.50 (95% CI 1.00-2.25). The most pronounced effect of a high GRS was observed on coronary revascularisations (adjusted HR 2.10 [95% CI 1.08-4.07]). Risks of cardiovascular death (adjusted HR 1.07 [95% CI 0.46-2.48]) and all-cause death (adjusted HR 1.15 [95% CI 0.65-2.03]) were unaffected. CONCLUSIONS: A GRS predicts recurrent cardiovascular events in high-risk stable CAD patients. The observed effect was mainly driven by coronary revascularisations.

Coronary artery disease-associated genetic variants and biomarkers of inflammation.

INTRODUCTION: Genetic constitution and inflammation both contribute to development of coronary artery disease (CAD). Several CAD-associated single-nucleotide polymorphisms (SNPs) have recently been identified, but their functions are largely unknown. We investigated the associations between CAD-associated SNPs and five CAD-related inflammatory biomarkers. METHODS: We genotyped 45 CAD-associated SNPs in 701 stable CAD patients in whom levels of high-sensitivity C-reactive protein (hsRCP), interleukin-6, calprotectin, fibrinogen and complement component 3 levels had previously been measured. A genetic risk score was calculated to assess the combined risk associated with all the genetic variants. A multiple linear regression model was used to assess associations between the genetic risk score, single SNPs, and the five inflammatory biomarkers. RESULTS: The minor allele (G) (CAD risk allele) of rs2075650 (TOMM40/APOE) was associated with lower levels of high-sensitivity C-reactive protein (effect per risk allele: -0.37 mg/l [95%CI -0.56 to -0.18 mg/l]). The inflammatory markers tested showed no association with the remaining 44 SNPs or with the genetic risk score. CONCLUSIONS: In stable CAD patients, the risk allele of a common CAD-associated marker at the TOMM40/APOE locus was associated with lower hsCRP levels. No other genetic variants or the combined effect of all variants were associated with the five inflammatory biomarkers.

Calprotectin and platelet aggregation in patients with stable coronary artery disease.

BACKGROUND: Recent studies suggest that the inflammation-associated protein calprotectin may be implicated in the pathogenesis of coronary artery disease (CAD). However, the impact of calprotectin levels on platelet aggregation in CAD patients has never been investigated. OBJECTIVES: We investigated the association between calprotectin levels and platelet aggregation in stable, high-risk CAD patients receiving aspirin as mono antiplatelet therapy. Furthermore, we aimed to investigate independent clinical and laboratory determinants of calprotectin levels. METHODS: We performed a cross-sectional study including 581 stable, high-risk CAD patients. All patients received 75 mg aspirin daily as mono antiplatelet therapy. Platelet aggregation was assessed by 1) impedance aggregometry (Multiplate Analyzer) using arachidonic acid (AA) and collagen as agonists and by 2) the VerifyNow Aspirin Assay. Low-grade inflammation was evaluated by calprotectin, high-sensitive C-reactive-protein (hs-CRP) and interleukin-6. Platelet activation was assessed by soluble P-selectin, and cyclooxygenase-1 inhibition was evaluated by serum thromboxane B2, both measured by ELISA. RESULTS: Calprotectin levels correlated positively with platelet aggregation according to Multiplate Analyzer (r=0.12, p=0.01). Additionally, calprotectin was positively associated with leukocytes (r=0.33, p<0.0001), hs-CRP (r=0.31, p<0.0001), interleukin-6 (r=0.28, p<0.0001), soluble P-selectin (r=0.10, p=0.02) and serum thromboxane B2 (r=0.10, p=0.02). Type 2 diabetes mellitus was an independent predictor of increased calprotectin levels (p=0.004), and trends were seen for body mass index (p=0.06) and smoking (p=0.07). Compliance with aspirin was confirmed by low serum thromboxane B2 levels in all patients (median [25%;75%]: 1.07 [0.52;1.87] ng/mL). CONCLUSION: Calprotectin levels correlated positively, though weakly, with platelet aggregation and activation as well as serum thromboxane B2 in high-risk, stable CAD patients treated with aspirin.

The Influence of Haemoglobin A1c Levels on Platelet Aggregation and Platelet Turnover in Patients with Coronary Artery Disease Treated with Aspirin.

BACKGROUND: Hyperglycaemia may attenuate the antiplatelet effect of aspirin and thereby increase the risk of cardiovascular events. We investigated the influence of increased haemoglobin A1c (HbA1c) levels on platelet aggregation and turnover in a large cohort of patients with coronary artery disease (CAD) with type 2 diabetes, prediabetes or no diabetes. METHODS: In this observational study, we included 865 stable CAD patients on 75 mg aspirin as mono-therapy of whom 242 patients had type 2 diabetes and were receiving antidiabetic drugs. Among 623 patients without diabetes, we classified 303 patients with prediabetes (HbA1c ≥5.7-6.4% [39-47 mmol/mol]) naive to antidiabetic drugs. Platelet aggregation was evaluated by the Multiplate Analyzer using arachidonic acid and collagen and by the VerifyNow Aspirin. Platelet turnover was evaluated by immature platelets using flow cytometry and platelet activation by soluble P-selectin. RESULTS: CAD patients with type 2 diabetes had higher platelet aggregation (all p-values <0.01), platelet turnover (immature platelet count, p<0.01) and platelet activation (p<0.001) than patients without diabetes. CAD patients with prediabetes had increased platelet aggregation (p = 0.02) and platelet count (p = 0.02) compared with patients without diabetes. Increased levels of HbA1c correlated positively with increased platelet aggregation using arachidonic acid (r = 0.19, p<0.0001), collagen (r = 0.10, p<0.01) and VerifyNow (r = 0.15, p<0.0001), and with platelet count (r = 0.08, p = 0.01), immature platelet count (r = 0.11, p<0.001) and soluble P-selectin (r = 0.15, p<0.0001). These associations were mainly evident in non-diabetic and prediabetic CAD patients. CONCLUSIONS: CAD patients with prediabetes and diabetes may have attenuated antiplatelet effect of aspirin compared with CAD patients without diabetes. This may be related to increased platelet count in patients with prediabetes. Increased levels of HbA1c correlated positively, though weakly, with increased platelet aggregation, platelet turnover and platelet activation.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease.

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

Determinants of reduced antiplatelet effect of aspirin in patients with stable coronary artery disease.

BACKGROUND: Aspirin is a cornerstone in management of coronary artery disease (CAD). However, considerable variability in the antiplatelet effect of aspirin has been reported. AIM: To investigate independent determinants of reduced antiplatelet effect of aspirin in stable CAD patients. METHODS: We performed a cross-sectional study including 900 stable, high-risk CAD patients. Among these, 795 (88%) had prior myocardial infarction, 250 (28%) had type 2 diabetes, and 170 (19%) had both. All patients received 75 mg aspirin daily as mono antiplatelet therapy. The antiplatelet effect of aspirin was assessed by measurement of platelet aggregation employing 1) multiple electrode aggregometry (MEA, Multiplate Analyzer) in whole blood anticoagulated with citrate or hirudin using arachidonic acid (AA) or collagen as agonists, and 2) VerifyNow Aspirin Assay. Compliance was assessed by measurement of serum thromboxane B2. RESULTS: Platelet count, prior myocardial infarction, type 2 diabetes and body mass index were independent determinants of increased AA-induced MEA platelet aggregation in citrate and hirudin anticoagulated blood (p-values ≤ 0.045). Similar results were found with VerifyNow. Prior coronary artery bypass grafting, age, smoking (MEA, AA/citrate) and female gender (MEA, AA/hirudin) were also independent determinants of increased platelet aggregation (p-values ≤ 0.038). Compliance was confirmed by low serum thromboxane B2 levels in all patients (median [25%;75%]: 0.97 [0.52;1.97], range 0.02-26.44 ng/ml). CONCLUSION: Platelet count, prior myocardial infarction, type 2 diabetes and body mass index were independent determinants of increased platelet aggregation, indicating that these characteristics may be key factors in reduced antiplatelet effect of aspirin in stable CAD patients.

Platelet turnover in stable coronary artery disease - influence of thrombopoietin and low-grade inflammation.

BACKGROUND: Newly formed platelets are associated with increased aggregation and adverse outcomes in patients with coronary artery disease (CAD). The mechanisms involved in the regulation of platelet turnover in patients with CAD are largely unknown. AIM: To investigate associations between platelet turnover parameters, thrombopoietin and markers of low-grade inflammation in patients with stable CAD. Furthermore, to explore the relationship between platelet turnover parameters and type 2 diabetes, prior myocardial infarction, smoking, age, gender and renal insufficiency. METHODS: We studied 581 stable CAD patients. Platelet turnover parameters (immature platelet fraction, immature platelet count, mean platelet volume, platelet distribution width and platelet large cell-ratio) were determined using automated flow cytometry (Sysmex XE-2100). Furthermore, we measured thrombopoietin and evaluated low-grade inflammation by measurement of high-sensitive CRP and interleukin-6. RESULTS: We found strong associations between the immature platelet fraction, immature platelet count, mean platelet volume, platelet distribution width and platelet large cell ratio (r = 0.61-0.99, p<0.0001). Thrombopoietin levels were inversely related to all of the platelet turnover parameters (r = -0.17--0.25, p<0.0001). Moreover, thrombopoietin levels were significantly increased in patients with diabetes (p = 0.03) and in smokers (p = 0.003). Low-grade inflammation evaluated by high-sensitive CRP correlated significantly, yet weakly, with immature platelet count (r = 0.10, p = 0.03) and thrombopoietin (r = 0.16, p<0.001). Also interleukin-6 correlated with thrombopoietin (r = 0.10, p = 0.02). CONCLUSION: In stable CAD patients, thrombopoietin was inversely associated with platelet turnover parameters. Furthermore, thrombopoietin levels were increased in patients with diabetes and in smokers. However, low-grade inflammation did not seem to have a substantial impact on platelet turnover parameters.

Fibrin clot structure and platelet aggregation in patients with aspirin treatment failure.

BACKGROUND: Aspirin is a cornerstone in prevention of cardiovascular events and modulates both platelet aggregation and fibrin clot formation. Some patients experience cardiovascular events whilst on aspirin, often termed aspirin treatment failure (ATF). This study evaluated both platelet aggregation and fibrin clot structure in patients with ATF. METHODS: We included 177 stable coronary artery disease patients on aspirin monotherapy. Among these, 116 (66%) had ATF defined as myocardial infarction (MI) whilst on aspirin. Platelet aggregation was assessed by Multiplate® aggregometry and VerifyNow®, whereas turbidimetric assays and scanning electron microscopy were employed to study fibrin clot characteristics. RESULTS: Enhanced platelet aggregation was observed in patients with ATF compared with non-MI patients following stimulation with arachidonic acid 1.0 mM (median 161 (IQR 95; 222) vs. 97 (60; 1776) AU*min, p = 0.005) and collagen 1.0 µg/mL (293 (198; 427) vs. 220 (165; 370) AU*min, p = 0.03). Similarly, clot maximum absorbance, a measure of fibrin network density, was increased in patients with ATF (0.48 (0.41; 0.52) vs. 0.42 (0.38; 0.50), p = 0.02), and this was associated with thinner fibres (mean ± SD: 119.7±27.5 vs. 127.8±31.1 nm, p = 0.003) and prolonged lysis time (552 (498; 756) vs. 519 (468; 633) seconds; p = 0.02). Patients with ATF also had increased levels of C-reactive protein (CRP) (1.34 (0.48; 2.94) and 0.88 (0.32; 1.77) mg/L, p = 0.01) compared with the non-MI group. Clot maximum absorbance correlated with platelet aggregation (r = 0.31-0.35, p-values<0.001) and CRP levels (r = 0.60, p<0.001). CONCLUSIONS: Patients with aspirin treatment failure showed increased platelet aggregation and altered clot structure with impaired fibrinolysis compared with stable CAD patients without previous MI. These findings suggest that an increased risk of aspirin treatment failure may be identified by measuring both platelet function and fibrin clot structure.