Biological efficacy of twice daily aspirin in type 2 diabetic patients with coronary artery disease

Personalized allocation of acetylsalicylic acid therapy for secondary prevention of coronary artery disease

Background

A single-daily dose of 75 mg of acetylsalicylic acid inhibits 100% of thromboxane-B2 synthesis within 30–60 min. Thromboxane-B2 synthesis then recovers slowly as new platelets are released from the bone marrow. Normally, only 10% of the platelets are replaced daily by new platelets entering circulation. Hence, 24 h after a dose of acetylsalicylic acid, thromboxane-B2 synthesis is still suppressed by more than 90%. Hence, there is an adequate anti-platelet effect even after 24 h of acetylsalicylic acid intake. However, some patients treated with once-daily acetylsalicylic acid may have an incomplete 24-h suppression of thromboxane-B2 synthesis due to increased platelet turnover. The response could be improved in such patients by twice-daily acetylsalicylic acid administration. This study aimed to identify such a group of patients who would benefit from a twice-daily dose of acetylsalicylic acid.

Materials and methods

Serum thromboxane-B2 levels were measured in 79 patients with coronary artery disease receiving 75 mg of acetylsalicylic acid for secondary prophylaxis. Serum levels of thromboxane-B2 were measured after 4 and 24 h of acetylsalicylic acid intake. Patients were then classified into three groups: steady suppression group (serum thromboxane B2 is adequately suppressed at 4 and 24 h), i.e., adequate response to acetylsalicylic acid; fast recovery group (more than 10% rise in serum thromboxane-B2 levels at 24-h when compared to at 4-h) and non-responders (serum thromboxane-B2 levels of >3,100 pg/ml after 4 h of acetylsalicylic acid intake). Patients in the fast recovery group were given twice-daily acetylsalicylic acid and thromboxane-B2 levels were re-measured.

Results

A total of 20 patients (24.3%) had steady suppression of thromboxane-B2 and 11 patients (13.9%) belonged to the fast recovery group, i.e., thromboxane-B2 levels were adequately suppressed at 4 h but had recovered by more than 10% at 24 h; which was adequately suppressed by twice-daily acetylsalicylic acid (p 0.004). A total of 48 patients (60.8%) were non-responders.

Conclusion

Twice-daily acetylsalicylic acid may be beneficial if serum thromboxane-B2 levels at 4 h are <3,100 and >3,100 pg/ml at 24 h. If thromboxane-B2 levels at 4 and 24 h is <3100 pg/ml but if there is a >10% rise in serum thromboxane B2 at 24 h as compared to that at 4 h, then twice-daily acetylsalicylic acid should be considered. However, if thromboxane-B2 at 4 and 24 h is >3,100 pg/ml consider switching over to a P2Y12 inhibitor.

Current and Novel Antiplatelet Therapies for the Treatment of Cardiovascular Diseases

Over the last decades, antiplatelet agents, mainly aspirin and P2Y₁₂ receptor antagonists, have significantly reduced morbidity and mortality associated with arterial thrombosis. Their pharmacological characteristics, including pharmacokinetic/pharmacodynamics profiles, have been extensively studied, and a significant number of clinical trials assessing their efficacy and safety in various clinical settings have established antithrombotic efficacy. Notwithstanding, antiplatelet agents carry an inherent risk of bleeding. Given that bleeding is associated with adverse cardiovascular outcomes and mortality, there is an unmet clinical need to develop novel antiplatelet therapies that inhibit thrombosis while maintaining hemostasis. In this review, we present the currently available antiplatelet agents, with a particular focus on their targets, pharmacological characteristics, and patterns of use. We will further discuss the novel antiplatelet therapies in the pipeline, with the goal of improved clinical outcomes among patients with atherothrombotic diseases.

Aspirin for the prevention of pre-eclampsia in women with pre-existing diabetes: Systematic review

BACKGROUND

There is a lack of evidence for pre-eclampsia prophylaxis with aspirin in women with pre-existing diabetes mellitus (DM).

AIMS

To examine the evidence for aspirin in pre-eclampsia prophylaxis in women with pre-existing DM.

MATERIAL AND METHODS

An electronic search using Ovid MEDLINE, Embase, CinicalTrials.gov and the Cochrane CENTRAL register of controlled trials through to February 2021 was performed. Reference lists of identified studies, previous review articles, clinical practice guidelines and government reports were manually searched. Randomised controlled trials (RCTs) of aspirin vs placebo for pre-eclampsia prophylaxis were included. Articles were manually reviewed to determine if cohorts included women with DM. The systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Data from included trials were extracted independently by two authors who also independently assessed risk of bias as per the Cochrane Handbook criteria version 5.1.0. Data were analysed using Rev-Man 5.4.

RESULTS

Forty RCTs were identified, of which 11 included a confirmed subset of women with DM; however, data were insufficient for meta-analysis. Meta-analysis of 930 women with DM, from individual patient data included in a systematic review and unpublished data from one of the 11 RCTs, showed a non-significant difference in the outcome of pre-eclampsia in participants treated with aspirin compared to placebo (odds ratio 0.58; 95% CI 0.20-1.71; P = 0.33).

CONCLUSIONS

Pre-eclampsia risk reduction with aspirin prophylaxis in women with pre-existing DM may be similar to women without pre-existing DM. However, randomised data within this meta-analysis were insufficient, warranting the need for further studies within this high-risk group of women.

[Résistance à l'aspirine : l'ennemi de mon ami est mon ennemi]

Low dose aspirin is an efficient antiplatelet agent to decrease the risk of occlusive arterial events, however it is not infallible. Aspirin resistance describe its inability to block the formation of thromboxane A2 in platelets and/or to produce an inhibitory effect on platelet aggregation. Detection of aspirin resistance relies on the results of various platelet function tests or on blood and urinary thromboxane metabolites concentrations, but these methods show very low correlation and reproducibility. Moreover, light-transmission aggregometry using arachidonic acid, known as the reference functional assay, requires technical expertise. The incidence rate of aspirin resistance amoung populations suffering from cardiovascular diseases is about 25%, however there is a wide variability depending on the specificity of the used test and the clinical features of the considered population. Aspirin resistance is associated with the recurrence of arterial occlusive events: the odds ratio is about 4 all tests combined, therefore it could be considered as a risk marker. Evidence is lacking regarding the relevance of these tests to resort an intensification of the antithrombotic treatment, and experts recommend to reserve their use for high-risk situations. Nevertheless several studies have explored the effect of dose increases or intake frequency increases, and revealed encouraging results regarding pharmacodynamic endpoints. The reasons for aspirin resistance are numerous, often remain debate, and can accumulate to result in poor response to aspirin.

Is platelet function testing at the acute phase under P2Y12 inhibitors helpful in predicting bleeding in real-life patients with acute coronary syndrome? The AVALANCHE study

BACKGROUND

In patients with acute coronary syndrome (ACS), current international guidelines recommend newer potent and predictable P2Y₁₂ inhibitors as first-line treatment despite a greater bleeding risk compared with clopidogrel.

AIM

To determine if platelet function testing can predict bleeding in real-life patients with ACS treated with newer P2Y₁₂ inhibitors.

METHODS

In this retrospective study, all consecutive adults admitted to the Lariboisière University Hospital for ACS, whatever the P2Y₁₂ inhibitor prescribed, who had platelet function testing (vasodilator-stimulated phosphoprotein phosphorylation [VASP] index and aggregation tests) during the initial hospital stay were included. Follow-up was performed to record bleeding events according to the Bleeding Academic Research Consortium (BARC) classification.

RESULTS

A total of 364 patients were included, treated with ticagrelor (n=123), prasugrel (n=105) or clopidogrel (n=136); 42.3% after an ST-segment elevation myocardial infarction, 27.1% after a non-ST-segment elevation myocardial infarction and 30.6% with unstable angina. Mean age was 64±11 years. Median VASP index was significantly lower with the newer P2Y₁₂ inhibitors (14% under ticagrelor, 14% under prasugrel) than with clopidogrel (42%). Despite these differences in the degree of platelet inhibition, the occurrence of bleeding (BARC 2-5) during follow-up was 7.7% overall, and was similar for all P2Y₁₂ inhibitors (ticagrelor 8.9%; prasugrel 6.6%; clopidogrel 7.4%). For each P2Y₁₂ inhibitor, it was impossible to determine a VASP index threshold under which bleeding was significantly greater during follow-up. Similarly, ADP-induced aggregation was more profoundly inhibited by ticagrelor and prasugrel than by clopidogrel, but this did not allow a threshold to be set for increased haemorrhagic risk.

CONCLUSIONS

Despite the substantial occurrence of bleeding in patients with ACS during follow-up, neither the VASP index nor platelet aggregation test results measured at the acute phase were helpful in predicting bleeding risk. Whether platelet function testing could be helpful later in the course of treatment remains to be evaluated.

Contemporary Clinical Use of Aspirin: Mechanisms of Action, Current Concepts, Unresolved Questions, and Future Perspectives

The ability of aspirin to inhibit platelet aggregation has positioned this agent within the most frequently used drugs worldwide. The aim of this article is to review the contemporary clinical use of aspirin and also to discuss unresolved issues not yet translated into clinical practice. Results from several clinical trials have led to strong guideline recommendations for aspirin use in the acute management and secondary prevention of cardiovascular disease. On the contrary, guidelines regarding aspirin use as primary prevention of cardiovascular disease are almost conservative, supported by recent trials reporting that the bleeding risk outweighs the potential benefits in most patients. In pregnancy, aspirin has proved efficient in preventing preeclampsia and small-for-gestational-age births in women at high risk, and is hence widely recommended in clinical guidelines. Despite the vast amount of clinical data on aspirin, several unresolved questions remain. Randomized trials have reported that aspirin reduces the risk of recurrent venous thromboembolism, but the clinical relevance remains limited, because direct oral anticoagulants are more effective. Laboratory studies suggest that a twice-daily dosing regimen or evening intake may lead to more efficient platelet inhibition, and the potential clinical benefit of such strategies is currently being explored in ongoing clinical trials. Enteric-coated formulations of aspirin are frequently used, but it remains unclear if they are safer and as efficient as plain aspirin. In the future, aspirin use after percutaneous coronary interventions might not be mandatory in patients who also need anticoagulant therapy, as several trials support shorter aspirin duration strategies. On the other hand, new treatment indications for aspirin will likely arise, as there is growing evidence that aspirin may reduce the risk of colorectal cancer and other types of cancer.

Once- versus Twice-Daily Aspirin in Patients at High Risk of Thrombotic Events: Systematic Review and Meta-Analysis

BACKGROUND

Acetylsalicylic acid (ASA) is a frequently used antiplatelet agent, although some individuals have reduced antiplatelet responses on ASA, with recurrent ischemic events. It has been proposed that shortening the ASA dosing interval may overcome the time-dependent renewal of the drug target, leading to a greater antiplatelet effect. We conducted a systematic review of randomized controlled trials (RCTs) to determine the efficacy of once- versus twice-daily ASA in conditions with increased platelet turnover.

METHODS

We conducted a systematic review and meta-analysis by searching the CENTRAL, MEDLINE, and Embase databases for RCTs assessing once- versus twice-daily ASA. Data were screened, extracted, and appraised by two independent reviewers, and were pooled using a random-effects model. The primary outcomes were major adverse cardiovascular events (MACEs) and serum thromboxane B2 (TxB2). Other pharmacodynamic measures were retrieved as secondary outcomes. Results were reported as mean differences with corresponding 95% confidence intervals (CIs). We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Seven RCTs were included, enrolling 379 participants overall. None of the studies reported clinical outcomes. Pooled results showed that compared with once-daily ASA, twice-daily ASA was associated with a decrease in mean TxB2 of 1.42 ng/mL (95% CI - 2.71 to - 0.13; I² = 66%). We found no differences in subgroup analyses based on disease subtype, trial blinding, or trial design. A greater antiplatelet activity of the twice-daily regimen was also found when using PFA-100-ADP methods, although not when using the VerifyNow, LTA-AA, and multiplate methods.

CONCLUSIONS

Twice-daily ASA was associated with a greater antiplatelet effect compared with standard once-daily ASA.

Comparison of Light Transmission Aggregometry With Impedance Aggregometry in Patients on Potent P2Y12 Inhibitors

Since data on the agreement between light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in patients on the more potent P2Y₁₂ inhibitors are missing so far, we investigated if the evaluation of the responsiveness to therapy by LTA can be replaced by MEA in 160 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel or ticagrelor (n = 80 each). Cut-off values for high on-treatment residual platelet reactivity (HRPR) in response to adenosine diphosphate (ADP) or arachidonic acid (AA) were defined according to previous studies showing an association of HRPR with the occurrence of adverse ischemic outcomes. ADP- inducible platelet aggregation was 33% and 37% (P = 0.07) by LTA and 19 AU and 20 AU (P = 0.38) by MEA in prasugrel- and ticagrelor-treated patients, respectively. AA- inducible platelet aggregation was 2% and 3% by LTA and 15 AU and 16 AU by MEA, (all P ≥ 0.3) in patients on prasugrel and ticagrelor, respectively. By LTA, HRPR ADP and HRPR AA were seen in 5%/5% and in 4%/ 13% of patients receiving prasugrel- and ticagrelor, respectively. By MEA, HRPR ADP and HRPR AA were seen in 3%/ 25% and 0%/24% of prasugrel- and ticagrelor-treated patients, respectively. ADP-inducible platelet reactivity by MEA correlated significantly with LTA ADP in prasugrel-treated patients (r = 0.4, P < 0.001), but not in those receiving ticagrelor (r = 0.09, P = 0.45). AA-inducible platelet aggregation by LTA and MEA did not correlate in prasugrel- and ticagrelor-treated patients. Sensitivity/specificity of HRPR by MEA to detect HRPR by LTA were 25%/99% for MEA ADP and 100%/79% for MEA AA in prasugrel-treated patients, and 0%/100% for MEA ADP and 70%/83% for MEA AA in ticagrelor-treated patients. In conclusion, on-treatment residual ADP-inducible platelet reactivity by LTA and MEA shows a significant correlation in prasugrel- but not ticagrelor-treated patients. However, in both groups LTA and MEA revealed heterogeneous results regarding the classification of patients as responders or non-responders to P2Y₁₂ inhibition.

Evening aspirin intake results in higher levels of platelet inhibition and a reduction in reticulated platelets - a window of opportunity for patients with cardiovascular disease?

Cardiovascular events occur most frequently in the early morning. Similarly, the release of reticulated platelets (RP) by megakaryocytes has a peak in the late night and early morning. Which aspirin regimen most effectively inhibits platelets during these critical hours is unknown. Hence, the primary objective of this trial was to assess platelet function and RP levels at 8.00 AM, in stable cardiovascular (CVD) patients, during three different aspirin regimens. In this open-label randomized cross-over study subjects were allocated to three sequential aspirin regimens: once-daily (OD) 80 mg morning; OD-evening, and twice-daily (BID) 40 mg. Platelet function was measured at 8.00 AM & 8.00 PM by serum Thromboxane B₂ (sTxB₂) levels, the Platelet Function Analyzer (PFA)-200® Closure Time (CT), Aspirin Reaction Units (ARU, VerifyNow®), and RP levels. In total, 22 patients were included. At 8.00 AM, sTxB₂ levels were the lowest after OD-evening in comparison with OD-morning (p = <0.01), but not in comparison with BID. Furthermore, RP levels were similar at 8.00 AM, but statistically significantly reduced at 8.00 PM after OD-evening (p = .01) and BID (p = .02) in comparison with OD-morning. OD-evening aspirin intake results in higher levels of platelet inhibition during early morning hours and results in a reduction of RP levels in the evening. These findings may, if confirmed by larger studies, be relevant to large groups of patients taking aspirin to reduce cardiovascular risk.

ImpaCt of aspirin regimen on THrombin generation in diabEtic patients with acute coronary syndrome: CARTHaGE-ACS trial

BACKGROUND

Diabetes is associated with a high rate of events after acute coronary syndrome. It was recently reported that once-daily aspirin might not provide stable biological efficacy in patients with diabetes.

AIMS

We sought to compare the biological efficacy of aspirin given once a day versus aspirin divided twice per day in a population of diabetic patients with non-ST elevation acute coronary syndrome (NSTE-ACS) as assessed by the thrombin generation test.

METHODS

We performed an open-label single-blind randomized study including 59 consecutive diabetic patients admitted for NSTE-ACS. Patients were randomly treated with aspirin 100 mg once a day (GA100; n = 20), aspirin 160 mg once a day (GA160; n = 19) or aspirin 100 mg twice a day (G2A100; n = 20). The primary endpoint was endogenous thrombin potential (ETP) at discharge and after 6 months.

RESULTS

The mean age of our patients was 61.5 ± 9 years, and 73% were male. The baseline characteristics were comparable between the three groups. In the GA100 group, there was no significant effect on ETP variation at 6 months (1150.46 ± 504.84 vs. 1087.63 ± 454.18; p = 0.794). An increase in aspirin dose with a second daily administration of 100 mg was associated with a significant reduction in ETP at 6 months (1004.87 ± 196.2 vs. 1233.63 ± 333.5; p = 0.003). A nonsignificant decrease in ETP was seen in the GA160 group (from 1173.8 ± 388.07 to 1053.64 ± 269.93 at 6 months, p = 0.117).

CONCLUSION

Only the twice-daily aspirin regimen led to better control of hypercoagulability in NSTE-ACS diabetic patients. However, no thrombin generation normalization was reported.

Antiplatelet therapies in diabetes

Cardiovascular complications remain the main cause of mortality and morbidity in diabetes. This is related to advanced vascular pathology in this population, together with an enhanced thrombotic environment. The increased risk in thrombosis is secondary to platelet hyper-reactivity and increased levels and/or altered activity of coagulation factors. The current review is focused on the role of antiplatelet agents in modulating the thrombotic milieu in diabetes and improving vascular outcome in this high-risk population. We review the latest evidence for the use of aspirin in primary vascular prevention together with long-term treatment with this agent for secondary prevention. We also discuss the effects of the various P2Y₁₂ inhibitors, including clopidogrel, prasugrel and ticagrelor, on both short- and long-term secondary vascular prevention. Moreover, we briefly review antiplatelet therapies in special groups of people including those intolerant to aspirin, individuals with peripheral vascular disease and those with cerebrovascular pathology. The overall aim of this review is to provide the healthcare professional with a pragmatic guide for the management of thrombotic risk using established antiplatelet therapies to improve vascular outcome in persons with diabetes.

Aspirin in the primary prevention of cardiovascular disease in diabetes mellitus: A new perspective

Although the improved control of hyperglycaemia and other cardiovascular risk factors was associated with a parallel decline of atherosclerotic cardiovascular disease (ASCVD) and death in both type 1 (T1) and type 2 (T2) diabetes mellitus (DM), the burden of death and hospitalization for ASCVD remains significantly higher by about 2-fold versus the matched non-DM population. Life style interventions, such as physical activity and healthy diet, and drugs, such as statins and low-dose aspirin, may have beneficial effects by targeting one or multiple pathways responsible for accelerated atherosclerosis and its thrombotic complications. The debate on the benefit-risk balance of primary cardiovascular prevention with aspirin has been especially vivacious over the past two years, following the publication of three large randomized, placebo-controlled, primary prevention trials in different settings, spanning from healthy elderly to DM subjects. The aim of this review is to discuss the pathophysiological, pharmacological and clinical evidence supporting the appropriate use of low-dose aspirin in DM, within the context of the current multifactorial approach to primary cardiovascular prevention.

Novel approaches to P2Y12 inhibition and aspirin dosing

Aspirin and P2Y₁₂ inhibitors remain commonly prescribed antiplatelet drugs in the treatment of atherothrombotic conditions. Despite established benefits of dual antiplatelet therapy (DAPT) in the setting of acute coronary syndromes, there remains residual ischemic risk in this group and the problem of bleeding complications is an ongoing issue. DAPT with aspirin and ticagrelor has now been studied in other patient groups such as those with concurrent diabetes and stable coronary artery disease, and those undergoing elective percutaneous coronary intervention (PCI). Recent trials of ticagrelor monotherapy have suggested this may have benefits over standard-of-care in some settings, such as PCI, but not in others such as peripheral arterial disease or stroke. A novel subcutaneously administered P2Y₁₂ inhibitor, selatogrel, has shown powerful, rapid and consistent effect in a phase 2 study. Aspirin dosing remains an area of investigation, particularly in the setting of DAPT. A novel regimen of very-low-dose twice-daily aspirin has hypothetical advantages in pharmacodynamic and pharmacokinetic effects, maintaining antiplatelet effect whilst reducing potentially harmful peak-trough variation.

Prevention of atherothrombotic events in patients with diabetes mellitus: from antithrombotic therapies to new-generation glucose-lowering drugs

Diabetes mellitus is an important risk factor for a first cardiovascular event and for worse outcomes after a cardiovascular event has occurred. This situation might be caused, at least in part, by the prothrombotic status observed in patients with diabetes. Therefore, contemporary antithrombotic strategies, including more potent agents or drug combinations, might provide greater clinical benefit in patients with diabetes than in those without diabetes. In this Consensus Statement, our Working Group explores the mechanisms of platelet and coagulation activity, the current debate on antiplatelet therapy in primary cardiovascular disease prevention, and the benefit of various antithrombotic approaches in secondary prevention of cardiovascular disease in patients with diabetes. While acknowledging that current data are often derived from underpowered, observational studies or subgroup analyses of larger trials, we propose antithrombotic strategies for patients with diabetes in various cardiovascular settings (primary prevention, stable coronary artery disease, acute coronary syndromes, ischaemic stroke and transient ischaemic attack, peripheral artery disease, atrial fibrillation, and venous thromboembolism). Finally, we summarize the improvements in cardiovascular outcomes observed with the latest glucose-lowering drugs, and on the basis of the available evidence, we expand and integrate current guideline recommendations on antithrombotic strategies in patients with diabetes for both primary and secondary prevention of cardiovascular disease.

Patients with diabetes mellitus have a prothrombotic status that increases the risk of cardiovascular events and worsens prognosis after these events. In this Consensus Statement, the Working Group on Thrombosis of the Italian Society of Cardiology proposes antithrombotic strategies for patients with diabetes in various cardiovascular settings.

Determinants of aspirin resistance in patients with type 2 diabetes

BACKGROUND

Cardiovascular disease is a leading cause of mortality among patients with type 2 diabetes mellitus (T2DM). Numerous patients with T2DM show resistance to aspirin treatment, which may explain the higher rate of major adverse cardiovascular events observed compared with non-diabetes patients, and it has recently been shown that aspirin resistance is mainly related to accelerated platelet turnover with persistent high platelet reactivity (HPR) 24h after last aspirin intake. The mechanism behind HPR is unknown. The aim of this study was to investigate the precise rate and mechanisms associated with HPR in a population of T2DM patients treated with aspirin.

METHODS

Included were 116 consecutive stable T2DM patients who had attended our hospital for their yearly check-up. HPR was assessed 24h after aspirin intake using light transmission aggregometry (LTA) with arachidonic acid (AA) and serum thromboxane B2 (TXB2) measurement. Its relationship with diabetes status, insulin resistance, inflammatory markers and coronary artery disease (CAD) severity, using calcium scores, were investigated.

RESULTS

Using LTA, HPR was found in 27 (23%) patients. There was no significant difference in mean age, gender ratio or cardiovascular risk factors in patients with or without HPR. HPR was significantly related to duration of diabetes and higher fasting glucose levels (but not consistently with HbA_1c), and strongly related to all markers of insulin resistance, especially waist circumference, HOMA-IR, QUICKI and leptin. There was no association between HPR and thrombopoietin or inflammatory markers (IL-6, IL-10, indoleamine 2,3-dioxygenase activity, TNF-α, C-reactive protein), whereas HPR was associated with more severe CAD. Similar results were found with TXB2.

CONCLUSION

Our results reveal that 'aspirin resistance' is frequently found in T2DM, and is strongly related to insulin resistance and severity of CAD, but weakly related to HbA_1c and not at all to inflammatory parameters. This may help to identify those T2DM patients who might benefit from alternative antiplatelet treatments such as twice-daily aspirin and thienopyridines.

Measurement of Thromboxane Biosynthesis in Health and Disease

Thromboxane (TX) A₂ is a chemically unstable lipid mediator involved in several pathophysiologic processes, including primary hemostasis, atherothrombosis, inflammation, and cancer. In human platelets, TXA₂ is the major arachidonic acid derivative via the cyclooxygenase (COX)-1 pathway. Assessment of platelet TXA₂ biosynthesis can be performed ex vivo through measurement of serum TXB₂, an index of platelet COX-1 activity, as well as in vivo through measurement of urinary enzymatic metabolites, a non-invasive index of platelet activation. This article reviews the main findings of four decades of clinical investigation based on these analytical approaches, focusing on the measurement of TXA₂ metabolites to characterize the pathophysiologic role of transiently or persistently enhanced platelet activation and to describe the clinical pharmacology of COX-1 inhibition in health and disease.

High Residual Platelet Reactivity during Aspirin Therapy in Patients with Non-St Segment Elevation Acute Coronary Syndrome: Comparison Between Initial and Late Phases

Background

High platelet reactivity (HPR) during therapy with acetylsalicylic acid (ASA) is a poor prognostic factor in acute coronary syndromes (ACS). The prevalence of HPR during ACS is greater than that reported in stable diseases. However, it is unclear whether this prevalence of HPR is a transient phenomenon or a characteristic of this high-risk population.

Objective

The main objective is to compare the effects of ASA on platelet function in the initial and late phases of ACS in a single population. Secondary objectives are: correlation between the tests between themselves and the relationship between the tests and the variation of the inflammatory markers (C-reactive protein and interleukin-6).

Methods

Seventy patients with non-ST segment elevation (NSTE) ACS in use of 100-200 mg of ASA per day for at least 7 days were prospectively studied. Platelet function was assessed in the first 48 hours and subsequently after 3 months using four methods: VerifyNow™ (VFN), whole blood platelet aggregation (WBPA) with arachidonic acid (AA) and collagen as agonists, and platelet function analyzer (PFA). The level of statistical significance considered was < 0.05.

Results

According to the more specific methods (WBPA with AA and VFN), the incidence of HPR was significantly higher in the early phase than in the late phase: WBPA with AA: 31% versus 13%, p = 0.015; VFN: 32% versus 16%, p = 0.049. The other methods tested, which were less specific for ASA, did not show significant differences between phases. The correlation between the methods was weak or moderate (r ranging from 0.3 to 0.5, p < 0.05), and there were no significant associations between HPR and inflammatory markers.

Conclusion

The prevalence of HPR during AAS therapy, assessed by specific methods for cyclooxygenase 1 (COX-1), is higher during the acute phase than in the late phase of NSTE ACS.

Rationale, design and baseline characteristics of the effect of ticagrelor on health outcomes in diabetes mellitus patients Intervention study

In the setting of prior myocardial infarction, the oral antiplatelet ticagrelor added to aspirin reduced the risk of recurrent ischemic events, especially, in those with diabetes mellitus. Patients with stable coronary disease and diabetes are also at elevated risk and might benefit from dual antiplatelet therapy. The Effect of Ticagrelor on Health Outcomes in diabEtes Mellitus patients Intervention Study (THEMIS, NCT01991795) is a Phase 3b randomized, double‐blinded, placebo‐controlled trial of ticagrelor vs placebo, on top of low dose aspirin. Patients ≥50 years with type 2 diabetes receiving anti‐diabetic medications for at least 6 months with stable coronary artery disease as determined by a history of previous percutaneous coronary intervention, bypass grafting, or angiographic stenosis of ≥50% of at least one coronary artery were enrolled. Patients with known prior myocardial infarction (MI) or stroke were excluded. The primary efficacy endpoint is a composite of cardiovascular death, myocardial infarction, or stroke. The primary safety endpoint is Thrombolysis in Myocardial Infarction major bleeding. A total of 19 220 patients worldwide have been randomized and at least 1385 adjudicated primary efficacy endpoint events are expected to be available for analysis, with an expected average follow‐up of 40 months (maximum 58 months). Most of the exposure is on a 60 mg twice daily dose, as the dose was lowered from 90 mg twice daily partway into the study. The results may revise the boundaries of efficacy for dual antiplatelet therapy and whether it has a role outside acute coronary syndromes, prior myocardial infarction, or percutaneous coronary intervention.

Very-low-dose twice-daily aspirin maintains platelet inhibition and improves haemostasis during dual-antiplatelet therapy for acute coronary syndrome

Higher aspirin doses may be inferior in ticagrelor-treated acute coronary syndrome (ACS) patients and reducing bleeding risk whilst maintaining antithrombotic benefits could improve outcomes. We characterized the pharmacodynamics of a novel dual-antiplatelet-therapy regimen consisting of very-low-dose twice-daily (BD) aspirin with standard-dose ticagrelor. A total of 20 ticagrelor-treated ACS patients entered a randomized crossover to take aspirin 20 mg BD (12-hourly) during one 14-day period and 75 mg once-daily (OD) in the other. After 14 days of treatment, serum thromboxane (TX)B₂ and light-transmittance aggregometry were assessed pre- and 2 h post-morning-dose, bleeding time was measured post-dose, and TXA₂ and prostacyclin stable metabolites were measured in urine collected 2 h post-morning-dose. Data are expressed as mean ± SD. After 14 days treatment, serum TXB₂ levels were significantly greater 2 h post-dosing with aspirin 20 mg BD vs. 75 mg OD (3.0 ± 3.6 ng/mL vs. 0.8 ± 1.9 ng/mL; p = 0.018) whereas pre-dosing levels were not significantly different (3.5 ± 4.1 ng/mL vs. 2.5 ± 3.1 ng/mL, p = 0.23). 1-mmol/L arachidonic acid-induced platelet aggregation was similarly inhibited by both regimens pre-dose (8.5 ± 14.3% vs. 5.1 ± 3.6%, p = 0.24) and post-dose (8.7 ± 14.2% vs. 6.6 ± 5.3%; p = 0.41). Post-dose bleeding time was shorter with 20 mg BD (680 ± 306 s vs. 834 ± 386 s, p = 0.02). Urinary prostacyclin and TX metabolite excretion were not significantly different. In conclusion, compared to aspirin 75 mg OD, aspirin 20 mg BD provided consistent inhibition of platelet TXA₂ release and aggregation, and improved post-dose hemostasis, in ticagrelor-treated ACS patients. Further studies are warranted to assess whether this regimen improves the balance of clinical efficacy and safety.

Why we should not skip aspirin in cardiovascular prevention

Since more than 20 years, aspirin is an approved and established first-line antiplatelet medication in cardiovascular prevention. This is partially due to ist unique mode of action which is not shared with any other antiplatelet agent as well by the reliability of its pharmacological efficacy: inhibition of platelet COX-1 and subsequent thromboxane formation in almost every patient. Aspirin acts synergistic with ADP-antagonists in dual antiplatelet therapy of acute coronary syndroms (ACS) and percutaneous coronary interventions (PCI) and is also approved for long-term secondary prevention. Patients with atrial fibrillation are an exception and benefit more from anticoagulants. After the introduction of the new oral anticoagulants (NOACs), i.e. direct inhibitors of factor Xa or thrombin formation, there is a renewed discussion about the role of antiplatelet agents, specifically if additional dual antiplatelet treatment is still necessary for an optimum clinical effect or whether one component, such as aspirin might be skipped in favor of other classes of oral antiplatelet agents, such as ADP-antagonists. The available data are insufficient to recommend this because of a low number of studies and a still uncertain benefit/ risk (bleeding) ratio. More research on aspirin as a chemopreventive appears also to be necessary and is going on, in particular in individuals at high-risk for vascular thrombotic diseases (diabetics, preeclampsia, venous thrombembolism).

Thrombosis and Vascular Inflammation in Diabetes: Mechanisms and Potential Therapeutic Targets

Cardiovascular disease remains the main cause of morbidity and mortality in patients with diabetes. The risk of vascular ischemia is increased in this population and outcome following an event is inferior compared to individuals with normal glucose metabolism. The reasons for the adverse vascular profile in diabetes are related to a combination of more extensive atherosclerotic disease coupled with an enhanced thrombotic environment. Long-term measures to halt the accelerated atherosclerotic process in diabetes have only partially addressed vascular pathology, while long-term antithrombotic management remains largely similar to individuals without diabetes. We address in this review the pathophysiological mechanisms responsible for atherosclerosis with special emphasis on diabetes-related pathways. We also cover the enhanced thrombotic milieu, characterized by increased platelet activation, raised activity of procoagulant proteins together with compromised function of the fibrinolytic system. Potential new therapeutic targets to reduce the risk of atherothrombosis in diabetes are explored, including alternative use of existing therapies. Special emphasis is placed on diabetes-specific therapeutic targets that have the potential to reduce vascular risk while keeping an acceptable clinical side effect profile. It is now generally acknowledged that diabetes is not a single clinical entity but a continuum of various stages of the condition with each having a different vascular risk. Therefore, we propose that future therapies aiming to reduce vascular risk in diabetes require a stratified approach with each group having a "stage-specific" vascular management strategy. This "individualized care" in diabetes may prove to be essential to improve vascular outcome in this high risk population.

Antiplatelet effect of aspirin during 24h in patients with type 2 diabetes without cardiovascular disease

INTRODUCTION

The antiplatelet effect of low-dose aspirin in patients with type 2 diabetes (T2DM) without cardiovascular disease (CVD) has not been thoroughly explored. We investigated if platelet aggregation increased during the standard 24-hour aspirin dosing interval in patients with T2DM compared to non-diabetic controls. Furthermore, we evaluated baseline platelet aggregation, the acute effects of aspirin on platelet aggregation and platelet turnover.

MATERIALS AND METHODS

We included 21 patients with T2DM and 21 age and sex-matched controls. Platelet aggregation was measured by impedance aggregometry (Multiplate® Analyzer) and markers of platelet turnover by flow cytometry (Sysmex® XE-5000). Blood samples were obtained at baseline and 1h after administration of 75mg of aspirin. Participants were then treated for 6days with once-daily aspirin, and blood sampling was repeated 1h and 24h after aspirin intake.

RESULTS

After 6days of treatment, platelet aggregation levels increased during the 24-hour aspirin dosing interval in both patients and controls (p<0.001) with no difference between patients and controls. At baseline, patients with diabetes had increased platelet aggregation compared to controls (p=0.03). Platelet aggregation was reduced after the first dose of aspirin and significantly further reduced after six days of treatment (p<0.001). Patients with T2DM had numerically higher immature platelet count compared to controls (p=0.09), indicating an increased platelet turnover.

CONCLUSION

Patients with T2DM without a history of CVD and controls had increased platelet aggregation at the end of the standard 24-hour dosing interval of aspirin. Further, aspirin-naïve T2DM patients had increased platelet aggregation compared to controls.

Effect of aspirin intake at bedtime versus on awakening on circadian rhythm of platelet reactivity

The risk of acute cardiovascular events is highest during morning hours, and platelet activity peaks during morning hours. The effect of timing of aspirin intake on circadian rhythm and morning peak of platelet reactivity is not known. It was our objective to evaluate the effect of timing of aspirin intake on circadian rhythm and morning peak of platelet reactivity. A randomised open-label cross-over trial in healthy subjects (n=14) was conducted. Participants used acetylsalicylic acid (80 mg) on awakening or at bedtime for two periods of two weeks, separated by a four-week wash-out period. At the end of both periods blood was drawn every 3 hours to measure COX-1-dependent (VerifyNow- Aspirin; Serum Thromboxane B2 [STxB2]) and COX-1-independent (flow cytometry surface CD62p expression; microaggregation) platelet activity. VerifyNow platelet reactivity over the whole day was similar with intake on awakening and at bedtime (mean difference: –9 [95 % confidence interval (CI) –21 to 4]). However, the morning increase in COX-1-dependent platelet activity was reduced by intake of aspirin at bedtime compared with on awakening (mean difference VerifyNow: –23 Aspirin Reaction Units [CI –50 to 4]; STxB2: –1.7 ng/ml [CI –2.7 to –0.8]). COX-1-independent assays were not affected by aspirin intake or its timing. Low-dose aspirin taken at bedtime compared with intake on awakening reduces COX-1-dependent platelet reactivity during morning hours in healthy subjects. Future clinical trials are required to investigate whether simply switching to aspirin intake at bedtime reduces the risk of cardiovascular events during the high risk morning hours.

[Diabetes Mellitus, a prothrombotic disease]

In patients with acute atherothrombotic disease, diabetes or glucose intolerance is frequently found. Indeed, the number of people with diabetes in the world continues to increase and is expected to reach more than 500 million people by 2035. Diabetes is a pathology commonly associated with both microvascular and macrovascular complications. Although the mortality of coronary artery disease has decreased significantly over the past 20 years, mortality in patients with type 2 diabetes has changed little and atherothrombotic events remain the leading cause of death in diabetic patients. Although our understanding of vascular pathology has greatly evolved in recent years, the cellular and molecular mechanisms linking thrombogenicity and diabetes remain incompletely understood. Type 1 and type 2 diabetes are prothrombotic pathologies. This prothrombotic state is due to both hyperglycemia and chronic hyperinsulinism. Among the different agonists involved in the increased thrombogenicity of diabetic patients, abnormalities can be found in all phases of coagulation. Increased procoagulant factors and tissue factor associated with impaired fibrinolysis, platelet hyperreactivity, endothelial dysfunction, leukocyte activation, low-grade inflammation, and microparticle involvement, they all play a role in the establishment of this prothrombotic condition. This review sought to provide an update on the prothrombotic nature of diabetes and its consequences in therapeutics.

Platelet indices and glucose control in type 1 and type 2 diabetes mellitus: A case-control study

BACKGROUND AND AIMS

The relationship between platelet indices and glucose control may differ in type 1 (T1DM) and type 2 (T2DM) diabetes. We aimed to investigate differences in mean platelet volume (MPV), platelet count, and platelet mass between patients with T1DM, T2DM, and healthy controls and to explore associations between these platelet indices and glucose control.

METHODS AND RESULTS

A total of 691 T1DM and 459 T2DM patients and 943 control subjects (blood donors) were included. HbA1c was measured in all subjects with diabetes and 36 T1DM patients further underwent 24 h-continuous glucose monitoring to estimate short-term glucose control (glucose mean and standard deviation). Adjusting for age and sex, platelet count was higher and MPV lower in both T1DM and T2DM patients vs control subjects, while platelet mass (MPV × platelet count) resulted higher only in T2DM. Upon further adjustment for HbA1c, differences in platelet count and mass were respectively 19.5 × 10⁹/L (95%CI: 9.8-29.3; p < 0.001) and 101 fL/nL (12-191; p = 0.027) comparing T2DM vs T1DM patients. MPV and platelet count were significantly and differently related in T2DM patients vs both T1DM and control subjects; this difference was maintained also accounting for HbA1c, age, and sex. Platelet mass and the volume-count relationship were significantly related to HbA1c only in T1DM patients. No associations were found between platelet indices and short-term glucose control.

CONCLUSION

By accounting for confounders and glucose control, our data evidenced higher platelet mass and different volume-count kinetics in subjects with T2DM vs T1DM. Long-term glucose control seemed to influence platelet mass and the volume-count relationship only in T1DM subjects. These findings suggest different mechanisms behind platelet formation in T1DM and T2DM patients with long-term glycaemic control being more relevant in T1DM than T2DM.

How I use laboratory monitoring of antiplatelet therapy

Antiplatelet therapy is of proven benefit in coronary artery disease and a number of other clinical settings. This article reviews platelet function, molecular targets of antiplatelet agents, and clinical indications for antiplatelet therapy before focusing on a frequent question to hematologists about the 2 most commonly used antiplatelet therapies: Could the patient be aspirin “resistant” or clopidogrel “resistant”? If so, should results of a platelet function test be used to guide the dose or type of antiplatelet therapy? Whether such guided therapy is of clinical benefit to patients has been a source of controversy. The present article reviews this subject in the context of 2 prototypical clinical cases. Available evidence does not support the use of laboratory tests to guide the dose of aspirin or clopidogrel in patients with so-called aspirin or clopidogrel “resistance.”

In Silico Modeling of the Antiplatelet Pharmacodynamics of Low-dose Aspirin in Health and Disease

The influence of platelet turnover on cyclooxygenase (COX-1) inhibition by low-dose aspirin remains largely uncharacterized due to limited feasibility of studying aspirin pharmacodynamics in bone marrow precursors. We developed an in silico compartmental model describing the aspirin effects on COX-1 activity in a population of megakaryocytes (MK) and in peripheral platelets. Model parameters were inferred from the literature and calibrated using measurements of serum thromboxane B₂ (sTXB₂ ), as proxy of COX-1 activity in peripheral platelets, in 17 healthy subjects and 24 patients with essential thrombocythemia (ET). The model reproduced well the average time-course of sTXB₂ inhibition in healthy (accuracy = 10.4%), the reduced inhibition of sTXB₂ observed in ET, and the effect of different dosing regimens. In conclusion, the in silico model accurately describes COX-1 inactivation by low-dose aspirin in MK and platelets in different clinical settings, and might help personalize aspirin regimens in conditions of altered megakaryopoiesis.

Hypofibrinolysis in diabetes: a therapeutic target for the reduction of cardiovascular risk

An enhanced thrombotic environment and premature atherosclerosis are key factors for the increased cardiovascular risk in diabetes. The occlusive vascular thrombus, formed secondary to interactions between platelets and coagulation proteins, is composed of a skeleton of fibrin fibres with cellular elements embedded in this network. Diabetes is characterised by quantitative and qualitative changes in coagulation proteins, which collectively increase resistance to fibrinolysis, consequently augmenting thrombosis risk. Current long-term therapies to prevent arterial occlusion in diabetes are focussed on anti-platelet agents, a strategy that fails to address the contribution of coagulation proteins to the enhanced thrombotic milieu. Moreover, antiplatelet treatment is associated with bleeding complications, particularly with newer agents and more aggressive combination therapies, questioning the safety of this approach. Therefore, to safely control thrombosis risk in diabetes, an alternative approach is required with the fibrin network representing a credible therapeutic target. In the current review, we address diabetes-specific mechanistic pathways responsible for hypofibrinolysis including the role of clot structure, defects in the fibrinolytic system and increased incorporation of anti-fibrinolytic proteins into the clot. Future anti-thrombotic therapeutic options are discussed with special emphasis on the potential advantages of modulating incorporation of the anti-fibrinolytic proteins into fibrin networks. This latter approach carries theoretical advantages, including specificity for diabetes, ability to target a particular protein with a possible favourable risk of bleeding. The development of alternative treatment strategies to better control residual thrombosis risk in diabetes will help to reduce vascular events, which remain the main cause of mortality in this condition.

Low-Dose Aspirin Is Effective Chemoprophylaxis Against Clinically Important Venous Thromboembolism Following Total Joint Arthroplasty: A Preliminary Analysis

BACKGROUND

Aspirin is a safe and effective prophylaxis for the prevention of venous thromboembolism following total joint arthroplasty. The optimal dose of aspirin prophylaxis is unknown. Our hypothesis was that lower-dose aspirin is as effective as higher-dose aspirin for the prevention of venous thromboembolism and is associated with fewer gastrointestinal side effects.

METHODS

In a prospective, crossover study, we analyzed 4,651 primary total joint arthroplasty cases performed from July 2013 to June 2015. For 4 weeks, 3,192 patients received enteric-coated 325-mg aspirin twice daily (the 325-mg aspirin group) and 1,459 patients received 81-mg aspirin twice daily (the 81-mg aspirin group). There were no significant differences (p > 0.05) in sex, body mass index, or Charlson Comorbidity Index between the two patient populations. Recorded complications occurring within 90 days postoperatively included symptomatic venous thromboembolism (deep venous thrombosis and pulmonary embolism), gastrointestinal complications, acute periprosthetic joint infection, and death.

RESULTS

The incidence of venous thromboembolism of 0.1% (95% confidence interval [CI], 0% to 0.3%) in the 81-mg aspirin group (1 with deep venous thrombosis and 1 with pulmonary embolism) was not significantly different (p = 0.345) from 0.3% (95% CI, 0.1% to 0.6%) in the 325-mg aspirin group (7 with deep venous thrombosis and 5 with pulmonary embolism). The incidence of gastrointestinal bleeding or ulceration of 0.3% (95% CI, 0% to 0.5%) in the 81-mg aspirin group was slightly, but not significantly (p = 0.66), lower than the 0.4% (95% CI, 0.2% to 0.6%) in the 325-mg aspirin group. The incidence of acute periprosthetic joint infection was 0.2% (95% CI, 0% to 0.4%) in the 81-mg aspirin group compared with 0.5% (95% CI, 0.2% to 0.7%) in the 325-mg aspirin group (p = 0.28). The 90-day mortality rate was similar in both groups at 0.1% (95% CI, 0% to 0.2%) in the 81-mg aspirin group and 0.1% (95% CI, 0% to 0.2%) in the 325-mg aspirin group (p = 0.78).

CONCLUSIONS

Our study demonstrates that low-dose aspirin is not inferior to high-dose aspirin for venous thromboembolism prophylaxis following total joint arthroplasty. This is not unexpected, as the available literature demonstrates that low-dose aspirin is as effective as higher-dose aspirin in the prevention of acute coronary syndrome and cerebrovascular events.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Current controversies in the use of aspirin and ticagrelor for the treatment of thrombotic events

INTRODUCTION

A P2Y₁₂ inhibitor plus aspirin is the most widely used antiplatelet strategy to prevent adverse outcomes in the setting of atherothrombotic vascular disease. Areas covered: A paucity of robust evidence for an optimal dose, gastrointestinal toxicity, ineffectiveness in high-risk patients and interactions with other antiplatelet agents, are major controversies associated with aspirin therapy. Ticagrelor is a reversibly binding oral P2Y₁₂ receptor blocker that mediates potent inhibition of adenosine diphosphate-induced platelet function. It is more effective than clopidogrel in preventing thrombotic events in acute coronary syndrome patients. The absence of a beneficial effect for ticagrelor versus clopidogrel in ACS observed in the North American subgroup of the PLATelet inhibition and patient Outcomes (PLATO) trial has been attributed to a higher concomitant aspirin dose. Expert commentary: Ongoing studies are now investigating the plausibility of removing aspirin therapy in the setting of potent P2Y₁₂ receptor blockade via ticagrelor monotherapy or replacing aspirin with an oral anticoagulant.

Aspirin for Primary Cardiovascular Risk Prevention and Beyond in Diabetes Mellitus

Daily administration of low-dose aspirin has proved to be beneficial in preventing recurrent cardiovascular events. However, the role of aspirin for primary prevention in patients with no overt cardiovascular disease is more controversial. In fact, in lower risk patients, the modest benefit in reducing serious vascular events can be offset by the increased risk of bleeding, including intracranial and gastrointestinal hemorrhage. Diabetes mellitus has been associated with a substantially increased risk of both first and recurrent atherothrombotic events, which makes aspirin therapy of potential value in these subjects. Moving from general aspects of aspirin pharmacology and specific issues in diabetes mellitus, this article reviews the literature on the topic of aspirin for primary prevention in general, and in subjects with diabetes mellitus in particular, to culminate with arguments pro and con and a practical risk-based algorithm for aspirin initiation in daily practice.

Clinical Update: Cardiovascular Disease in Diabetes Mellitus: Atherosclerotic Cardiovascular Disease and Heart Failure in Type 2 Diabetes Mellitus - Mechanisms, Management, and Clinical Considerations

Cardiovascular disease remains the principal cause of death and disability among patients with diabetes mellitus. Diabetes mellitus exacerbates mechanisms underlying atherosclerosis and heart failure. Unfortunately, these mechanisms are not adequately modulated by therapeutic strategies focusing solely on optimal glycemic control with currently available drugs or approaches. In the setting of multifactorial risk reduction with statins and other lipid-lowering agents, antihypertensive therapies, and antihyperglycemic treatment strategies, cardiovascular complication rates are falling, yet remain higher for patients with diabetes mellitus than for those without. This review considers the mechanisms, history, controversies, new pharmacological agents, and recent evidence for current guidelines for cardiovascular management in the patient with diabetes mellitus to support evidence-based care in the patient with diabetes mellitus and heart disease outside of the acute care setting.

Randomized controlled trial comparing impact on platelet reactivity of twice-daily with once-daily aspirin in people with Type 2 diabetes

AIMS

Reduced aspirin efficacy has been demonstrated in people with Type 2 diabetes. Because increased platelet reactivity and/or turnover are postulated mechanisms, we examined whether higher and/or more frequent aspirin dosing might reduce platelet reactivity more effectively.

METHODS

Participants with Type 2 diabetes (n = 24) but without known cardiovascular disease were randomized in a three-way crossover design to 2-week treatment periods with aspirin 100 mg once daily, 200 mg once daily or 100 mg twice daily. The primary outcome was platelet reactivity, assessed using the VerifyNow(™) ASA method. Relationships between platelet reactivity and aspirin dosing were examined using generalized linear mixed models with random subject effects.

RESULTS

Platelet reactivity decreased from baseline with all doses of aspirin. Modelled platelet reactivity was more effectively reduced with aspirin 100 mg twice daily vs. 100 mg once daily, but not vs. 200 mg once daily. Aspirin 200 mg once daily did not differ from 100 mg once daily. Aspirin 100 mg twice daily was also more effective than once daily as measured by collagen/epinephrine-stimulated platelet aggregation and urinary thromboxane levels, with a similar trend measured by serum thromboxane levels. No episodes of bleeding occurred.

CONCLUSIONS

In Type 2 diabetes, aspirin 100 mg twice daily reduced platelet reactivity more effectively than 100 mg once daily, and numerically more than 200 mg once daily. Clinical outcome trials evaluating primary cardiovascular disease prevention with aspirin in Type 2 diabetes may need to consider using a more frequent dosing schedule.

Clopidogrel Use as Single Antiplatelet Therapy in Outpatients with Stable Coronary Artery Disease: Prevalence, Correlates and Association with Prognosis (from the CORONOR Study)

Background: Clopidogrel use as single antiplatelet therapy (SAPT) has never been evaluated in stable coronary artery disease (CAD) outpatients either as compared to placebo or aspirin. Methods: We therefore studied 2,823 outpatients included in a prospective registry. The patients were divided into 2 groups according to their antiplatelet therapy regimen: patients treated with clopidogrel were compared with those treated with aspirin alone. Results: The mean time since CAD diagnosis was 7.9 years. Altogether, 776 (27.5%) patients received clopidogrel as SAPT. Factors independently associated with clopidogrel use were prior aortic or peripheral intervention, drug-eluting stent implantation, stroke, carotid endarterectomy and time since CAD diagnosis. Clopidogrel tended to be used in higher-risk patients: composite of cardiovascular death, myocardial infarction or stroke at 5.8 versus 4.2% (p = 0.056). However, after propensity score matching, similar event rates were observed between the groups: 5.9% when treated with clopidogrel versus 4.4% with aspirin (p = 0.207). The rate of bleeding was also similar between the groups. Conclusions: Our study shows that a significant proportion of stable CAD patients are treated with clopidogrel as SAPT in modern practice. Several correlates of such an attitude were identified. Our results suggest that this strategy is not beneficial as compared to aspirin alone in terms of ischaemic or bleeding events.