Aspirin and clopidogrel: efficacy, safety, and the issue of drug resistance

Efficacy and safety of using cilostazol versus aspirin in secondary stroke prevention: systematic review and meta-analysis of randomised controlled clinical trials

BACKGROUND

Secondary stroke prevention is crucial for reducing recurrent events and associated morbidity. Cilostazol, a phosphodiesterase III inhibitor, is considered an alternative to aspirin for patients with ischaemic stroke due to its potentially lower risk of haemorrhagic complications. This meta-analysis evaluates the efficacy and safety of cilostazol versus aspirin for secondary stroke prevention. It provides a basis for drug selection and observation of secondary stroke prevention strategies.

METHODS

A comprehensive search was conducted in PubMed, Cochrane Library, EMBASE and Web of Science databases for randomised controlled trials comparing cilostazol with aspirin in secondary stroke prevention. Key outcomes included recurrence of ischaemic stroke, intracranial haemorrhage (ICH), death, effective rate and incidence of adverse events. Meta-analysis was performed using a random-effects model, and heterogeneity was assessed using I2 statistics and Cochran's Q test. Publication bias was evaluated using Doi plots and Luis Furuya-Kanamori index.

RESULTS

Thirteen studies involving 8993 participants were included. Cilostazol significantly reduced the recurrence of ischaemic stroke (risk ratio (RR): 0.766, 95% confidence interval (CI): 0.624-0.941) and ICH (RR: 0.392, 95% CI: 0.250-0.616) compared to aspirin. No significant differences were observed in overall mortality or adverse events. Cilostazol increased risks of headache, dizziness, diarrhoea and tachycardia but reduced constipation. Heterogeneity was generally low to moderate.

CONCLUSION

Cilostazol is an effective alternative to aspirin for secondary stroke prevention, reducing the risk of recurrent ischaemic stroke and ICH. However, its use is associated with certain adverse effects. Clinicians should consider individual patient profiles and preferences when selecting anti-platelet therapy for stroke prevention. Further research is warranted to optimise cilostazol use in clinical practice.

Changes in platelet maturity and reactivity following acute ST-segment elevation myocardial infarction

Background

Reduced effect of antiplatelet therapy has been reported in patients with ST-segment elevation myocardial infarction (STEMI). This could partly be explained by an increase of highly reactive immature platelets.

Objectives

To investigate changes in platelet maturity and reactivity after acute STEMI.

Methods

Patients diagnosed with STEMI, admitted for primary percutaneous coronary intervention, and treated according to international guidelines, were included. Blood samples were obtained within 24 hours after admission and at 2- to 3-months follow-up. Platelet maturity and reactivity using multicolor flow cytometry with SYTO-13 to categorize platelet maturity, whole blood platelet aggregation, serum thromboxane B2 levels, and standard immature platelet markers (eg, immature platelet count and fraction, and mean platelet volume) were measured.

Results

A total of 44 STEMI patients were included. The reactivity of immature platelets was consistently higher at baseline and at follow-up when compared to the entire platelet population and the mature platelet population (all P values < .05). The expression of CD63 (a dense granule marker) in immature platelets was consistently high compared to the entire platelet population and the mature platelet population and did not change from baseline to follow-up (P values > .24). Additionally, a positive significant correlation was found between standard immature platelet markers and the expression of CD63 on platelets both at baseline and follow-up (rho ranging from 0.32 to 0.62, all P values < .05).

Conclusion

Immature platelets represent a highly reactive platelet subpopulation crucial for the overall platelet reactivity, partly due to a high expression of dense granules. Despite treatment with loading and maintenance doses of antiplatelet therapy, the reactivity of immature platelets remained high in STEMI patients.

Efficacy and safety of aspirin plus clopidogrel versus aspirin alone in ischemic stroke or high-risk transient ischemic attack: A meta-analysis of randomized controlled trials

Background: Antiplatelet therapy plays an important role in reducing the risk of stroke recurrence in patients with mild ischemic stroke or high-risk transient ischemic attack (TIA). However, data regarding the effectiveness and safety of using aspirin plus clopidogrel in dual antiplatelet therapy (DAPT) compared to aspirin alone in mild ischemic stroke is limited. Methods: PubMed/MEDLINE, Embase, Cochrane Library, and ClinicalTrials.gov were searched for randomized controlled trials (RCTs) that compared DAPT to aspirin alone started within 72 hours in mild ischemic stroke or high-risk TIA. We used a random effects model to pool risk ratios (RRs) along with 95% CIs for clinical outcomes. Results: Four RCTs with 16,547 patients were included in this study. DAPT significantly reduced the risk of recurrent stroke by 26% (RR: 0.74; 95% CI: 0.67-0.83; p < 0.00001), ischemic stroke by 28% (RR: 0.72; 95% CI: 0.65-0.80; p < 0.00001), and major adverse cardiovascular events (MACE) by 24% (RR: 0.76; 95% CI: 0.68-0.84; p < 0.00001) compared to aspirin monotherapy. However, DAPT was associated with a significantly increased risk of moderate or severe bleeding (RR: 1.88; 95% CI: 1.10-3.23; p = 0.02) compared to aspirin alone. No significant differences were observed for hemorrhagic stroke (RR: 1.77; 95% CI: 0.96-3.29; p = 0.07), all-cause mortality (RR: 1.25; 95% CI: 0.87-1.80; p = 0.23), cardiovascular mortality (RR: 1.38; 95% CI: 0.81-2.33; p = 0.23), and myocardial infarction (RR: 1.63; 95% CI: 0.77-3.46; p = 0.20). Conclusion: DAPT involving aspirin plus clopidogrel reduces stroke recurrence and MACE but can lead to an increased risk of moderate or severe bleeding compared to aspirin monotherapy. (PROSPERO ID: CRD42024499310).

Aspirin in Patients with Viral Hepatitis: Systematic Review and Meta-Analysis of Observational Studies

BACKGROUND

Hepatocellular carcinoma (HCC) is a disease demonstrating increasing morbidity and mortality, especially in patients with chronic viral hepatitis. Studies have shown that aspirin can reduce the incidence of liver cancer; however, the degree of benefit in patients with viral hepatitis is unclear. This study focused on the association between aspirin use and HCC risk in patients with chronic viral hepatitis.

METHODS

A systematic search of the PubMed, Embase, Web of Science, and Cochrane Library databases was performed from the earliest available date to December 16, 2023. The primary outcome was HCC incidence, and the secondary outcome was gastrointestinal bleeding. The results were expressed as hazard ratios (HRs) and 95% confidence intervals (CIs). Meta-analyses were performed by using random or fixed-effects models based on the heterogeneity assessed via the I2 statistic.

RESULTS

A total of 13 articles (303,414 participants and 14,423 HCC patients) were included in the analysis. The incidence of HCC in aspirin users was lower than that in non-aspirin users (HR 0.75; 95% CI, 0.68-0.83; P < 0.001; I2 = 90.0%). Subgroup analysis further showed that this effect may be more obvious in HCV patients, non-cirrhotic patients, patients with statins, and long-term aspirin users, but it may have the risk of gastrointestinal bleeding (HR 1.13; 95% CI, 1.07-1.20; P = 0.906; I2 = 0.0%).

CONCLUSIONS

Our meta-analysis shows that in patients with chronic viral hepatitis, aspirin use is associated with a significantly reduced risk of liver cancer, but attention should be paid to the possible risk of gastrointestinal bleeding, and this conclusion needs further validation in the future.

Immature platelets and platelet reactivity in patients with acute ST-segment Elevation Myocardial Infarction using whole blood flow cytometry with SYTO-13 staining

BACKGROUND

Reduced effect of antiplatelet therapy has been reported in patients with ST-segment elevation myocardial infarction (STEMI). Multiple factors may concur to explain this, including increased amount of highly reactive immature platelets.

OBJECTIVES

To investigate the association between immature platelets and reactivity determined with multicolour flow cytometry using the SYTO-13 dye in STEMI patients.

METHODS

We conducted an observational study of 59 patients with acute STEMI. Blood samples were obtained within 24 h after admission and after loading doses of dual antiplatelet therapy. For comparison, samples were obtained from 50 healthy individuals. Immature platelets and platelet reactivity were investigated using multicolour flow cytometry including the SYTO-13 dye that binds to platelet RNA and thus provides a method for subdividing platelets into immature and mature platelets. Additionally, we assessed platelet aggregation, serum-thromboxane B2 levels and standard immature platelet markers.

RESULTS

Immature platelets were more reactive than mature platelets in both STEMI patients and healthy individuals (p-values < 0.05). STEMI patients had lower platelet aggregation and thromboxane B2 levels than healthy individuals. We found a positive association between automatically determined immature platelet markers and CD63 expression on activated platelets (Spearman's rho: 0.27 to 0.58, p-values < 0.05).

CONCLUSIONS

Our study shows that immature platelets identified with a multicolour flow cytometric method using the SYTO-13 dye are more reactive than mature platelets in patients with acute STEMI and in healthy individuals. The presence of immature platelets may be important for the overall platelet reactivity, which may have implications for the effect of antiplatelet therapy.

Convolutional neuronal network for identifying single-cell-platelet-platelet-aggregates in human whole blood using imaging flow cytometry

Imaging flow cytometry is an attractive method to investigate individual cells by optical properties. However, imaging flow cytometry applications with clinical relevance are scarce so far. Platelet aggregation naturally occurs during blood coagulation to form a clot. However, aberrant platelet aggregation is associated with cardiovascular disease under steady-state conditions in the blood. Several types of so-called antiplatelet drugs are frequently described to reduce the risk of stroke or cardiovascular diseases. However, an efficient monitoring method is missing to identify the presence and frequency of platelet-platelet aggregates in whole blood on a single cell level. In this work, we employed imaging flow cytometry to identify fluorescently labeled platelets in whole blood with a conditional gating strategy. Images were post-processed and aligned. A convolutional neural network was designed to identify platelet-platelet aggregates of two, three, and more than three platelets, and results were validated against various data set properties. In addition, the neural network excluded erythrocyte-platelet aggregates from the results. Based on the results, a parameter for detecting platelet-platelet aggregates, the weighted platelet aggregation, was developed. If employed on a broad scale with proband and patient samples, our method could aid in building a future diagnostic marker for cardiovascular disease and monitoring parameters to optimize drug prescriptions in such patient groups.

Aspirin and clopidogrel resistance; a neglected gap in stroke and cardiovascular practice in Iran: a systematic review and meta-analysis

OBJECTIVE

Antiplatelet drugs, such as Aspirin and Clopidogrel (Plavix) are effective in the primary prevention of thromboembolic events. They are commonly used to reduce the risk of recurrence of thromboembolism. The body's hemostatic system responds differently to these drugs in different people. Resistance testing for aspirin and Clopidogrel is now recommended before starting antiplatelet therapy.

METHODS

A systematic literature search was performed on May 12, 2021, using the medical search engines PubMed, Scopus, and Web of Science, and the local databases SID and Magiran. After data extraction, a meta-analysis was performed using Comprehensive Meta-Analysis (CMA2) software. The I2 statistic was used to measure heterogeneity between estimates.

RESULTS

Among the 949 papers, Clopidogrel resistance was assessed in 136 patients and Aspirin resistance in 400 patients. The prevalence of Aspirin resistance was found to be 52.1% and the prevalence of Clopidogrel resistance was found to be 20.5%.

CONCLUSION

It seems that in Iran, the issue of Aspirin and Clopidogrel resistance is suboptimally addressed. This pattern could also occur in other developing countries in the Middle East region.

Pharmacological Efficacy and Gastrointestinal Safety of Different Aspirin Formulations for Cardiovascular Prevention: A Narrative Review

Aspirin inhibits platelet function by irreversibly inhibiting the synthesis of thromboxane A2 (TxA2). Aspirin, at low doses, is widely used for cardiovascular prevention. Gastrointestinal discomfort, mucosal erosions/ulcerations and bleeding are frequent complications of chronic treatment. To reduce these adverse effects, different formulations of aspirin have been developed, including enteric-coated (EC) aspirin, the most widely used aspirin formulation. However, EC aspirin is less effective than plain aspirin in inhibiting TxA2 production, especially in subjects with high body weight. The inadequate pharmacological efficacy of EC aspirin is mirrored by lower protection from cardiovascular events in subjects weighing >70 kg. Endoscopic studies showed that EC aspirin causes fewer erosions of the gastric mucosa compared to plain aspirin (which is absorbed in the stomach) but causes mucosal erosions in the small intestine, where it is absorbed. Several studies demonstrated that EC aspirin does not reduce the incidence of clinically relevant gastrointestinal ulceration and bleeding. Similar results were found for buffered aspirin. Although interesting, the results of experiments on the phospholipid-aspirin complex PL2200 are still preliminary. Considering its favorable pharmacological profile, plain aspirin should be the preferred formulation to be used for cardiovascular prevention.

Monitoring of Antiplatelet Therapy

In the late 1990s, the antithrombotic antiplatelet agent, clopidogrel, a P2Y12 inhibitor, was introduced. Around the same time, there was an increase in a number of new methods to measure platelet function (e.g., PFA-100 in 1995), and this has continued. It became evident that not all patients responded to clopidogrel in the same way and that some patients had a relative "resistance" to therapy, termed "high on-treatment platelet reactivity." This then led to some publications to advocate platelet function testing being used for patients on antiplatelet therapy. Platelet function testing was also suggested for use in patients awaiting cardiac surgery after stopping their antiplatelet therapy as a way of balancing thrombotic risk pre-surgery and bleeding risk perioperatively. This chapter will discuss some of the commonly used platelet function tests used in these settings, particularly those that are sometimes referred to as point-of-care tests or that require minimal laboratory sample manipulation. The latest guidance and recommendations for platelet function testing will be discussed following several clinical trials looking at the usefulness of platelet function testing in these clinical settings.

Aspirin Use and the Risk of Hepatocellular Carcinoma: A Meta-analysis

INTRODUCTION AND AIM

The use of aspirin is a potential protective factor against the development of hepatocellular carcinoma (HCC). Therefore, we conducted a meta-analysis to evaluate the contribution of aspirin to the risk of HCC.

METHODS

We searched for PubMed and EMBASE through September 2021.

RESULTS

Eighteen studies (16 cohort, 2 case-control) were included. Aspirin users were less likely to develop HCC than nonusers [adjusted odds ratio (OR), 0.54; 95% confidence interval (CI): 0.44-0.66]. Stratified analysis showed that aspirin reduced the risk of HCC in Asian and Western populations (OR, 0.59 vs. 0.67). Besides, aspirin has protective effects against HCC after hepatitis B virus (OR, 0.70; 95% CI: 0.52-0.93) and hepatitis C virus infections (OR, 0.41; 95% CI: 0.23-0.73). Aspirin has protective effects on people with chronic liver disease (OR, 0.46; 95% CI: 0.31-0.67) and on the general population (OR, 0.65; 95% CI: 0.54-0.79). In addition, confounding factors have an important impact on the results of aspirin prevention of liver cancer before (OR, 0.28; 95% CI: 0.06-1.27) and after (OR, 0.58; 95% CI: 0.47-0.71) adjustment. Further studies have shown that those in the long duration group do not experience better effects in preventing HCC (OR, 0.62 vs. 0.63). A further meta-analysis of 3 articles showed that the use of aspirin did not increase the risk of bleeding in patients with HCC (OR, 1.19; 95% CI: 0.87-1.64).

CONCLUSION

Our meta-analysis shows that the use of aspirin is associated with a lower risk of liver cancer.

Systematic Review and Meta-analysis: Association of Aspirin With Incidence of Hepatocellular Carcinoma

Aim: To explore the relationship between the use of aspirin and the incidence of hepatocellular carcinoma (HCC). Methods: MEDLINE, EMBASE, Web of Science and Cochrane CENTRAL databases were searched systematically from the earliest available date to 13 March 2020. The primary outcome was incidence of HCC, and the secondary outcomes were recurrence and mortality of HCC. The results were expressed as the Hazard Ratio (HR) and 95% confidence interval (CI). Based on the heterogeneity evaluated with the I 2 statistic, a meta-analysis was performed using either a random- or fixed-effects model. Results: A total of sixteen articles (2781100 participants) were included. There was lower incidence of HCC in aspirin users than those in non-aspirin users (HR, 0.56; 95% CI, 0.46-0.69; p < 0.001). Subgroup analysis further showed that the incidence of liver cancer in patients with alcoholic cirrhosis (HR, 0.14; 95% CI, 0.09-0.22; p < 0.001) and virus hepatitis (HR, 0.68; 95% CI, 0.62-0.74; p < 0.001) who use aspirin was lower than that of patients who do not use aspirin. In addition, aspirin was found to associate with decreased risk of HCC mortality (HR, 0.71; 95% CI, 0.65-0.78; p < 0.001), not HCC recurrence (HR, 0.52; 95% CI, 0.15-1.76; p = 0.291). Conclusions: Aspirin use is significantly associated with the low incidence rate of liver cancer.

Ultra-high-throughput Ca2+ assay in platelets to distinguish ITAM-linked and G-protein-coupled receptor activation

Antiplatelet drugs targeting G-protein-coupled receptors (GPCRs), used for the secondary prevention of arterial thrombosis, coincide with an increased bleeding risk. Targeting ITAM-linked receptors, such as the collagen receptor glycoprotein VI (GPVI), is expected to provide a better antithrombotic-hemostatic profile. Here, we developed and characterized an ultra-high-throughput (UHT) method based on intracellular [Ca2+]i increases to differentiate GPVI and GPCR effects on platelets. In 96-, 384-, or 1,536-well formats, Calcium-6-loaded human platelets displayed a slow-prolonged or fast-transient [Ca2+]i increase when stimulated with the GPVI agonist collagen-related peptide or with thrombin and other GPCR agonists, respectively. Semi-automated curve fitting revealed five parameters describing the Ca2+ responses. Verification of the UHT assay was done with a robustness compound library and clinically relevant platelet inhibitors. Taken together, these results present proof of principle of distinct receptor-type-dependent Ca2+ signaling curves in platelets, which allow identification of new inhibitors in a UHT way.

P2Y12 inhibition in acute coronary syndromes treated with percutaneous intervention - Understanding the debate on Prasugrel or Ticagrelor

After more than 10 years of routine clinical use, a debate about the preference of prasugrel over ticagrelor has been unveiled following publication of the ISAR-REACT 5 trial, an investigator-initiated trial directly comparing both substances as part of dual anti-platelet therapy following interventional treatment in patients with acute coronary syndromes (ACS). Both substances had been tested in trials, approved by authorities and subsequently recommended by guidelines according to the strategy applied in the respective approval trial. This resulted in prasugrel tested in TRITON only be given after diagnostic coronary angiography in the absence of ST-segment elevations (NSTE-ACS) and ticagrelor tested in PLATO being administered even before diagnostic coronary angiography in all forms of acute coronary syndromes. Whichever way was safest and most efficient, had never been clarified before. ISAR-REACT 5 showed superior efficacy of prasugrel over ticagrelor in general, and of deferred administration of prasugrel over pre-treatment with ticagrelor in NSTE-ACS patients undergoing percutaneous coronary interventions. Subsequently, in 2020 the European guidelines for NSTE-ACS adopted both positions in recommending the respective preference. Afterwards, a confrontational debate erupted between those favouring the ISAR-REACT 5 results and their implementation in guidelines and others still preferring the generalized interpretation of the overall study results from PLATO. In this review, we reflect the history leading to trial design of TRITON and PLATO and the way this subsequently impacted on clinical practice and guideline recommendations.

Electrical impedance vs. light transmission aggregometry: Testing platelet reactivity to antiplatelet drugs using the MICELI POC impedance aggregometer as compared to a commercial predecessor

BACKGROUND

Patients' responses to antiplatelet therapy significantly vary, with individuals showing high residual platelet reactivity associated with thrombosis. To personalize thrombosis management, platelet function testing has been suggested as a promising tool able to monitor the antithrombotic effect of antiplatelet agents in real-time. We have prototyped the MICELI, a miniature and easy-to-use electrical impedance aggregometer (EIA), measuring platelet aggregation in whole blood. Here, we tested the capability of the MICELI aggregometer to quantify platelet reactivity on antiplatelet agents, as compared with conventional light-transmission aggregometry (LTA).

METHODS

Platelet aggregation in ACD-anticoagulated whole blood and platelet-rich plasma of healthy donors (n = 30) was evaluated. The effect of clopidogrel, ticagrelor, cangrelor, cilostazol, and tirofiban on ADP-induced aggregation was tested, while aspirin was evaluated with arachidonic acid and collagen. Platelet aggregation was recorded using the MICELI or BioData PAP-8E (Bio/Data Corp.) aggregometers.

RESULTS

The MICELI aggregometer detected an adequate and comparable dose-dependent decrease of platelet aggregation in response to increments of drugs' concentrations, as compared to LTA (the inter-device R2 = 0.79-0.93). Platelet aggregation in platelet-rich plasma recorded by LTA showed higher sensitivity to antiplatelet agents, but it couldn't distinguish between different drug doses as indicated by saturation of the aggregatory response.

CONCLUSION

Platelet aggregation in whole blood as recorded by EIA represents a better model system for evaluation of platelet reactivity as compared with platelet aggregation in platelet-rich plasma as recorded by LTA, since EIA takes into consideration the modulatory effect of other blood cells on platelet hemostatic function and pharmacodynamics of antiplatelet drugs in vivo. As such, the MICELI impedance aggregometer could be potentially employed for the point-of-care monitoring of platelet function in patients on-treatment for personalized tailoring of their antiplatelet regimen.

Clinical characteristics and outcomes of chronic subdural hematoma in patients with a history of antiplatelet therapy

OBJECTIVE

Chronic subdural hematoma (CSDH) is a common neurosurgical disease. Many patients with CSDH take antiplatelet (AP) drugs. Several studies have focused merely on the relationship between AP drug use and recurrence without deeply analyzing the specific clinical features of these patients. The primary objective of this study was to investigate the detailed clinical characteristics and outcomes of CSDH patients with a history of AP therapy.

METHODS

A total of 1181 CSDH patients over 40 years of age who received burr-hole craniostomy were enrolled. Clinical information, computed tomographic findings, and data on long-term outcomes and recurrence among these patients were gathered. We divided these patients into two groups according to whether they had a history of AP therapy. Percentages and χ2 tests were applied for categorical variables. Standard deviations and 2-sided unpaired t-tests were applied for continuous variables. Univariate and multivariate logistic regression analyses were performed to identify independent factors of the outcomes (6 months after discharge).

RESULTS

AP therapy was not related to the outcomes of patients with CSDH (P = 0.48), and there were no differences in recurrence between the AP and non-AP group. Only Bender grade (P < 0.01, B = -3.14, Exp (B) = 0.04, 95% CI 0.01-0.29) was associated with the outcomes of patients in the AP group. The incidence of complications in the AP group was higher than that in the non-AP group (P < 0.01). Postoperative thrombotic events may be more likely to occur in the AP group than in the non-AP group (P = 0.02). Patients in the AP group were older (P < 0.01) and had more comorbidities (P < 0.01).

CONCLUSIONS

Patients treated with AP therapy had more complications. The outcomes of patients treated with AP therapy were associated with their status of admission. Patients treated with AP therapy were at greater risk for postoperative thrombotic events. The recurrence rate of CSDH did not appear to be affected by AP therapy.

Biomarkers for Antiplatelet Therapies in Acute Ischemic Stroke: A Clinical Review

Stroke is one of the world's leading causes of disability and death. Antiplatelet agents are administered to acute ischemic stroke patients as secondary prevention. Clopidogrel involves biotransformation by cytochrome P450 (CYP) enzymes into an active metabolite, and single nucleotide polymorphisms (SNPs) can influence the efficacy of this biotransformation. Despite the therapeutic advantages of aspirin, there is significant inter-individual heterogeneity in response to this antiplatelet drug. In this clinical review, the recent advances in the biomarkers of antiplatelet agents in acute ischemic stroke are discussed. The studies reviewed herein highlight the clinical relevance of antiplatelet resistance, pharmacotherapy of antiplatelet agents predicting drug response, strategies for identifying aspirin resistance, pharmacogenetic variants of antiplatelet agents, miRNAs, and extracellular vesicles (EVs) as biomarkers toward the personalized approach in the management of acute ischemic stroke. The precise pathways contributing to antiplatelet resistance are not very well known but are presumably multi-factorial. It is essential to understand the clinical relevance of clopidogrel and aspirin-related single nucleotide polymorphism (SNPs) as potential predictive and prognostic biomarkers. Prasugrel is a next-generation antiplatelet agent that prevents ADP-platelet activation by binding irreversibly to P2Y12 receptor. There are sporadic reports of prasugrel resistance and polymorphisms in the Platelet endothelial aggregation receptor-1 (PEAR1) that may contribute to a change in the pharmacodynamics response. Ticagrelor, a direct-acting P2Y12-receptor antagonist, is easily absorbed and partly metabolized to major AR-C124910XX metabolite (ARC). Ticagrelor's primary active metabolite, ARC124910XX (ARC), is formed via the most abundant hepatic cytochrome P450 (CYP) enzyme, CYP3A4, and CYP3A5. The integration of specific biomarkers, genotype as well as phenotype-related data in antiplatelet therapy stratification in patients with acute ischemic stroke will be of great clinical significance and could be used as a guiding tool for more effective, personalized therapy.

In-vitro and in-vivo metabolism of different aspirin formulations studied by a validated liquid chromatography tandem mass spectrometry method

Low-dose aspirin (ASA) is used to prevent cardiovascular events. The most commonly used formulation is enteric-coated ASA (EC-ASA) that may be absorbed more slowly and less efficiently in some patients. To uncover these "non-responders" patients, the availability of proper analytical methods is pivotal in order to study the pharmacodynamics, the pharmacokinetics and the metabolic fate of ASA. We validated a high-throughput, isocratic reversed-phase, negative MRM, LC-MS/MS method useful for measuring circulating ASA and salicylic acid (SA) in blood and plasma. ASA-d4 and SA-d4 were used as internal standards. The method was applied to evaluate: (a) the "in vitro" ASA degradation by esterases in whole blood and plasma, as a function of time and concentration; (b) the "in vivo" kinetics of ASA and SA after 7 days of oral administration of EC-ASA or plain-ASA (100 mg) in healthy volunteers (three men and three women, 37-63 years). Parameters of esterases activity were Vmax 6.5 ± 1.9 and Km 147.5 ± 64.4 in plasma, and Vmax 108.1 ± 20.8 and Km 803.2 ± 170.7 in whole blood. After oral administration of the two formulations, tmax varied between 3 and 6 h for EC-ASA and between 0.5 and 1.0 h for plain-ASA. Higher between-subjects variability was seen after EC-ASA, and one subject had a delayed absorption over eight hours. Plasma AUC was 725.5 (89.8-1222) for EC-ASA, and 823.1(624-1196) ng h/mL (median, 25-75% CI) for plain ASA. After the weekly treatment, serum levels of TxB2 were very low (< 10 ng/mL at 24 h from the drug intake) in all the studied subjects, regardless of the formulation or the tmax. This method proved to be suitable for studies on aspirin responsiveness.

Multiparameter microfluidics assay of thrombus formation reveals increased sensitivity to contraction and antiplatelet agents at physiological temperature

INTRODUCTION

Current developments to assess qualitative and quantitative platelet traits in flowed whole-blood are based on microfluidic devices that mostly operate at room temperature. However, operation at physiological temperature (37 °C) may increase the assay's sensitivity, and facilitates the comparison to other platelet function tests of the diagnostic laboratory.

MATERIALS AND METHODS

We adapted the conventional microspot-based microfluidic device with a simple thermo-coupled pre-heating module. Automated analysis of microscopic images assisted in obtaining five time-dependent parameters of thrombus formation over collagen microspots (shear rate 1000 s^-1). These modifications allowed rapid testing of control and patient blood samples at physiological temperature.

RESULTS AND CONCLUSION

The higher temperature enhanced platelet adhesion and aggregation as well as late thrombus characteristics such as size and contraction, when compared to room temperature. Moreover, assessment at 37 °C indicated a time-dependent impairment of the thrombus parameters in blood from patients taking common antiplatelet medication, i.e. aspirin and/or clopidogrel. This pointed to increased contribution of the autocrine platelet agonists thromboxane A₂ and ADP in the buildup of contracted thrombi under flow. Overall, this study underlined the advantage of multiparameter assessment of microfluidic thrombus formation in detecting an acquired platelet dysfunction, when operating at physiological temperature. This work may bring microfluidics tests closer to the diagnostic laboratory.

Antiplatelet Therapy Improves the Prognosis of Patients with Hepatocellular Carcinoma

Simple Summary

Antiplatelet therapy shows antitumor effect in several types of cancers. In liver disease, antiplatelet therapy reduces liver fibrosis and occurrence of HCC. However, the effect after diagnosis of hepatocellular carcinoma is still unknown. Therefore, we aimed to clarify the effects of antiplatelet therapy for HCC patients in this study. We compared patients with and without antiplatelet therapy in overall survival, liver-related death, tumor progression, Child-Pugh deterioration and bleeding. Our results suggested that antiplatelet therapy had antitumor effect, liver protective effect and safety. Therefore, patients with antiplatelet therapy could reduce liver-related death and improve overall survival.

Abstract

Aims: Antiplatelet therapy has been reported to reduce liver fibrosis and hepatocellular carcinoma (HCC), and has exhibited antitumor properties in other cancers. However, the effects of antiplatelet therapy after diagnosis of HCC are unknown. We investigated the effects of antiplatelet therapy on prognosis, tumor progression, liver function and safety in HCC patients. Methods: We retrospectively analyzed 772 HCC patients. Antiplatelet therapy was defined as the regular intake of aspirin or clopidogrel from HCC diagnosis through to an endpoint of either overall survival (OS) or liver-related death. Overall survival, liver-related death, tumor progression, Child–Pugh deterioration and hemorrhage were analyzed for patients who either had or had not undertaken antiplatelet therapy. Results: The numbers of patients who did and did not undertake antiplatelet therapy were 111 and 661, respectively. Patients who undertook antiplatelet therapy were older and had better liver function at diagnosis. Antiplatelet therapy resulted in significant improvements in OS (p < 0.01) and lower risk of liver-related death (p < 0.01). Multivariate Cox regression analysis revealed that antiplatelet therapy had a significant negative association with liver-related death (hazard ratio (HR): 0.64, 95% confidence interval (CI): 0.44–0.93, p = 0.02). In patients who underwent transcatheter arterial chemoembolization (TACE) as the first treatment, antiplatelet therapy prevented tumor progression (p < 0.01) and Child–Pugh deterioration (p < 0.01). Antiplatelet therapy did not increase the risk of hemorrhagic events. Conclusions: Antiplatelet therapy reduced liver-related death and improved OS safely in HCC patients.

Resistance to Antiplatelet Therapy Is Associated With Symptoms of Cerebral Ischemia in Carotid Artery Disease

Background:

Platelet inhibitory therapy is prescribed to prevent arterial thromboembolism in patients with atherosclerotic disease. Although taken by millions of people, around 30% are resistant to the treatment they are being prescribed.

Aims:

To determine whether symptoms of cerebral ischemia, or pre-operative cerebral emboli, in patients admitted for a carotid endarterectomy were associated with resistance to aspirin or clopidogrel.

Methods:

Venous blood from 133 patients immediately before carotid endarterectomy (CEA) was analyzed for resistance to aspirin and clopidogrel by multiplate impedance aggregometry. The number of emboli/hour entering the ipsilateral middle cerebral artery was counted by transcranial Doppler (TCD) on the day before surgery in 33 of these patients.

Results:

Resistance was found in 21 (26.3%) of 100 patients taking aspirin and 14 (42%) of 33 taking clopidogrel. Mean (sd) residual platelet aggregation was significantly higher at 41.9(32) Au in patients who had suffered recent symptoms of cerebral ischemia compared with 30.8(16) Au in asymptomatic patients (p = 0.012). Residual platelet aggregation also correlated significantly with the number of emboli/hour counted by TCD in the ipsilateral middle cerebral artery (r = 0.45, p = 0.009).

Conclusion:

Antiplatelet resistance was associated with the frequency of cerebral emboli and recent symptoms of cerebral ischemia in patients with carotid disease. Definitive clinical studies are needed to explore whether testing for antiplatelet resistance should be undertaken routinely in patients starting platelet inhibitory therapy for cardiovascular disease.

Mean Corpuscular Volume Predicts Adverse Outcomes Following Peripheral Angioplasty With Stenting and Is Associated With On-Treatment Platelet Reactivity

Structural aspects of red blood cells have been associated with cardiovascular disease. No data linking mean corpuscular volume (MCV) to clinical outcomes and on-treatment platelet reactivity in patients with peripheral artery disease (PAD) are available. We investigated a composite of atherothrombotic events and target vessel restenosis or reocclusion following infrainguinal stenting for stable PAD. Residual platelet reactivity was measured by light transmission aggregometry (LTA) and the VerifyNow assays. We included 104 patients receiving dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. In receiver-operating characteristic analysis, MCV effectively discriminated between patients with and without adverse outcomes and identified a MCV ≤90.8 fL as optimal cutoff. Adverse outcomes occurred significantly more often in patients with low MCV (log-rank P = .002). In univariable Cox regression analysis, low MCV was associated with an increased risk of future adverse outcomes (hazard ratio [HR]: 2.662 [95%CI: 1.304-5.434]; P = .007) and remained significantly associated after adjustment (HR: 2.591 [95%CI: 1.242-5.403]; P = .011). Mean corpuscular volume was inversely correlated with arachidonic acid (AA)- and adenosine diphosphate (ADP)-inducible platelet reactivity by LTA and with the VerifyNow aspirin assay. Low MCV is associated with adverse outcomes over 2 years following infrainguinal stenting. Mean corpuscular volume correlates inversely with AA- and ADP-inducible platelet reactivity during DAPT.

Evaluation of the use of anti-platelet therapy throughout the peri-operative period in patients with femoral neck fracture surgery. A retrospective cohort study

INTRODUCTION

Fracture neck of femur (hip fracture) is a very common problem among old age group. Such elderly patients usually have some comorbidities for which they may use anti-platelet therapy (such as clopidogrel, aspirin, or others) for long duration (chronic use). These anti-platelet medications might make the blood thin and increase bleeding tendency. So, if these elderly people present with fracture neck of femur requiring surgical intervention, they might be at increased risk of bleeding and other complications if the use of these anti-platelet agents was continued throughout the peri-operative period.

OBJECTIVES

This current study aims to find out whether it is safe or not to continue the use of anti-platelet drugs during the peri-operative period in patients with hip fracture surgery. If it is safe and there are no complications, then there is no harm to continue the use of these drugs peri-operatively without any surgical delay. But if it is unsafe and there is increased risk of bleeding or blood transfusion or other complications, then such medications must be stopped peri-operatively. Thus, the medical practice and care will be improved to achieve patient safety.

METHODS

It was a retrospective study which reviewed files and notes of patients who had hip fracture surgery. These patients were divided into 2 groups. First group was on long-term anti-platelet treatment (APTG), and the use of these medicines continued during the peri-operative phase. The second group was not on anti-platelet treatment at all (NAPTG). Then, a comparison was done between both groups in terms of the following parameters during the peri-operative (pre- and post-operative) period: (i) intra-operative blood loss, (ii) operative time in minutes (length of surgery), (iii) pre-operative haemoglobin level, (iv) the need for blood transfusion, (v) haematoma formation, (vi) re-operation for any reason, (vii) post-operative wound infection, and (viii) duration in days to achieve complete wound healing post-operatively. So these measures are good parameters to assess bleeding tendency and bleeding risk. Data was collected, and statistical analysis was done using Pearson's chi-squared test and independent sample t test as appropriate.

RESULTS

325 participants were enrolled in the study. There were 163 patients in the APTG (Anti-Platelet Treatment Group) and 162 patients in the NAPTG (Non-Anti-Platelet Treatment Group). It has been found that there was no statistically significant difference between the APTG and NAPTG in terms of these peri-operative parameters: (i) intra-operative blood loss, (ii) operative time in minutes (length of surgery), (iii) pre-operative haemoglobin level, (iv) the need for blood transfusion, (v) haematoma formation, (vi) re-operation for any reason, (vii) post-operative wound infection, and (viii) duration in days to achieve complete wound healing post-operatively (P > 0.650).

CONCLUSION

It is safe to continue the use of anti-platelet therapy throughout the peri-operative phase in patients with hip fracture surgery. The continuation of such therapy is not associated with increased risk of bleeding or blood transfusion or other complications in patients who had surgical treatment for femoral neck fracture.

Oxidative pathways of arachidonic acid as targets for regulation of platelet activation

Platelet activation plays an important role in acute and chronic cardiovascular disease states. Multiple pathways contribute to platelet activation including those dependent upon arachidonic acid. Arachidonic acid is released from the platelet membrane by phospholipase A2 action and is then metabolized in the cytosol by specific arachidonic acid oxidation enzymes including prostaglandin H synthase, 12-lipoxygenase, and cytochrome P450 to produce pro- and anti-inflammatory eicosanoids. This review aims to analyze the role of arachidonic acid oxidation on platelet activation, the enzymes that use it as a substrate associated as novel therapeutics target for antiplatelet drugs.

The p48_HPC antithrombogenic flow diverter: initial human experience using single antiplatelet therapy

Objective

The p48 is a low-profile, intermediate-porosity flow diverter. phenox GmbH-trademarked hydrophilic polymer coating (pHPC) is a hydrophilic coating that has been shown in vitro to reduce the thrombogenicity of nitinol device surfaces. We performed the present study to determine whether the p48_HPC can be implanted using prasugrel alone.

Methods

We retrospectively identified all patients who were treated with the p48_HPC from January 2017 to December 2018 (n = 5) and underwent single antiplatelet therapy (SAPT) with prasugrel. P2Y12 inhibition was confirmed by the VerifyNow assay. The occurrence of thromboembolic and haemorrhagic complications was recorded alongside the occlusion rates of the treated aneurysms.

Results

All patients achieved adequate occlusion (Raymond–Roy Occlusion Classification I or II) during the follow-up period. No thromboembolic complications occurred. One patient developed a contained haematoma within the Sylvian fissure from the treated aneurysm 2 weeks postoperatively without clinical sequelae.

Conclusions

In this small series, no thromboembolic complications occurred in patients treated with the surface modified p48_HPC flow diverter and SAPT. Further studies with longer follow-up periods and larger cohorts should be performed.

Comparison of metabolomics and platelet aggregometry between Plavix and generic clopidogrel in cats: a pilot study

OBJECTIVES

This pilot study sought to assess the metabolism of Plavix (Bristol-Myers Squibb/Sanofi) and generic clopidogrel in cats, using a novel assay for the measurement of clopidogrel, clopidogrel carboxylic acid (CCA) and clopidogrel active metabolite (CAM-D).

METHODS

This was a prospective, randomized, double-blind study. Four healthy, skeletally mature cats were enrolled into the study. There were two treatment phases during which cats received either Plavix or generic clopidogrel at a dosage of 18.75 mg PO q24h for 7 days with a 2 week washout between phases. During each phase, plasma concentrations of parent drug and active and inactive metabolites were measured along with impedance platelet aggregometry in response to adenosine diphosphate (ADP).

RESULTS

The ratio of CAM-D between generic clopidogrel and Plavix was 0.83 (equivalence reference 1.00, 90% confidence interval 0.80-1.25). Inhibition of ADP-induced platelet aggregation was variable, with two cats classified as non-responders in both treatment phases. The concentrations of CAM-D were not predictive of aggregometry-based responsiveness to either formulation of clopidogrel.

CONCLUSIONS AND RELEVANCE

This is the first study comparing Plavix and generic clopidogrel in cats. Administration of the generic formulation resulted in comparable plasma concentrations of clopidogrel active metabolite when compared with Plavix.

Platelet function testing in pigs using the Multiplate® Analyzer

For endovascular research pigs are an established animal model. However, experiences regarding analyses of platelet inhibition in pigs using the Multiplate® Analyzer are limited. The aims of the present study were to investigate if (1) the Multiplate® Analyzer is a suitable method for examination of porcine platelet function using manufacturers’ recommendations for human blood, and (2) platelet inhibition can be induced with acetylsalicylic acid (ASA) and clopidogrel in pigs reliably, and if (3) non-responders to one of the drug can be detected. Additionally we examined differences in (4) the effectiveness of ASA between oral administration and intravenous application, and (5) between domestic pigs (German Landrace; GL) and miniature pigs (MP). We investigated platelet function of 36 unmedicated pigs (GL n = 28; MP n = 8). In addition, 32 blood samples taken from medicated pigs (GL n = 15; MP n = 17) were analysed. Platelet inhibition was induced in four different ways: (1) 500 mg ASA intravenously (n = 11), (2) 500 mg ASA intravenously and 450 mg clopidogrel orally (n = 5), (3) 250 mg ASA orally (n = 11), (4) 250 mg ASA orally and 75 mg clopidogrel orally (n = 5). Results of the ASPI and ADP test of the Multiplate® Analyzer subtests in unmedicated and medicated pigs were in a comparable range to results known from humans. Application of ASA decreased the mean values of the ASPI test significantly regardless of the application method. Joined administration of ASA and clopidogrel also decreased the mean values of the ADP test significantly. Both, oral and intravenous administrations of ASA as well as oral administration of clopidogrel effectively inhibited platelet function in pigs. One pig did not respond to clopidogrel. We found no differences between domestic and miniature pigs regarding reference values in unmedicated pigs and the effectiveness of ASA and clopidogrel.

Role of Platelet Activation and Oxidative Stress in the Evolution of Myocardial Infarction

Myocardial infarction, commonly known as heart attack, evolves from the rupture of unstable atherosclerotic plaques to coronary thrombosis and myocardial ischemia–reperfusion injury. A body of evidence supports a close relationship between the alterations following an ischemia–reperfusion injury-induced oxidative stress and platelet activity. Through their critical role in thrombogenesis and inflammatory responses, platelets are fully (totally) implicated from atherothrombotic plaque formation to myocardial infarction onset and expansion. However, mere platelet aggregation prevention does not offer full protection, suggesting that other antiplatelet therapy mechanisms may also be involved. Thus, the present review discusses the integrative role of platelets, oxidative stress, and antiplatelet therapy in triggering myocardial infarction pathophysiology.

Targeting Early Atherosclerosis: A Focus on Oxidative Stress and Inflammation

Atherosclerosis is a chronic vascular inflammatory disease associated to oxidative stress and endothelial dysfunction. Oxidation of low-density lipoprotein (LDL) cholesterol is one of the key factors for the development of atherosclerosis. Nonoxidized LDL have a low affinity for macrophages, so they are not themselves a risk factor. However, lowering LDL levels is a common clinical practice to reduce oxidation and the risk of major events in patients with cardiovascular diseases (CVD). Atherosclerosis starts with dysfunctional changes in the endothelium induced by disturbed shear stress which can lead to endothelial and platelet activation, adhesion of monocytes on the activated endothelium, and differentiation into proinflammatory macrophages, which increase the uptake of oxidized LDL (oxLDL) and turn into foam cells, exacerbating the inflammatory signalling. The atherosclerotic process is accelerated by a myriad of factors, such as the release of inflammatory chemokines and cytokines, the generation of reactive oxygen species (ROS), growth factors, and the proliferation of vascular smooth muscle cells. Inflammation and immunity are key factors for the development and complications of atherosclerosis, and therefore, the whole atherosclerotic process is a target for diagnosis and treatment. In this review, we focus on early stages of the disease and we address both biomarkers and therapeutic approaches currently available and under research.

Association of Daily Aspirin Therapy With Risk of Hepatocellular Carcinoma in Patients With Chronic Hepatitis B

IMPORTANCE

Antiviral therapy cannot erase hepatocellular carcinoma (HCC) risk in patients with chronic hepatitis B, and it is not indicated for most hepatitis B virus (HBV) carriers. Another effective way of reducing HCC risk needs to be developed. Aspirin may prevent cancer development, but clinical evidence in patients with HBV-related HCC remains limited.

OBJECTIVE

To investigate the association of daily aspirin therapy with HBV-related HCC risk.

DESIGN, SETTING, AND PARTICIPANTS

In this Taiwan nationwide cohort study, we screened 204 507 patients with chronic hepatitis B for the period January 1, 1997, to December 31, 2012. After excluding patients with confounding conditions, 2123 patients who continuously received daily aspirin for 90 or more days (treated group) were randomly matched 1:4 with 8492 patients who had never received antiplatelet therapy (untreated group) by means of propensity scores, consisting of the follow-up index date, baseline characteristics, and potentially chemopreventive drug use during follow-up. Data were analyzed from August 1 to November 30, 2018.

EXPOSURES

Daily aspirin therapy during the study period.

MAIN OUTCOMES AND MEASURES

Both cumulative incidence of and hazard ratios (HRs) for HCC development were analyzed after adjusting patient mortality as a competing risk event.

RESULTS

Of the 10 615 patients included in the analysis, 7690 (72.4%) were men; mean (SD) age was 58.8 (11.8) years. The cumulative incidence of HCC in the treated group was significantly lower than that in the untreated group in 5 years (5.20%; 95% CI, 4.11%-6.29% vs 7.87%; 95% CI, 7.15%-8.60%; P < .001). In the multivariable regression analysis, aspirin therapy was independently associated with a reduced HCC risk (HR, 0.71; 95% CI, 0.58-0.86; P < .001). Sensitivity subgroup analyses also verified this association (all HRs <1.0). In addition, older age (HR, 1.01 per year; 95% CI, 1.00-1.02), male sex (HR, 1.75; 95% CI, 1.43-2.14), and cirrhosis (HR, 2.89; 95% CI, 2.45-3.40) were independently associated with an increased HCC risk, but nucleos(t)ide analogue (HR, 0.54; 95% CI, 0.41-0.71) or statin (HR, 0.62; 95% CI, 0.42-0.90) use was correlated with a decreased HCC risk.

CONCLUSIONS AND RELEVANCE

Daily aspirin therapy may be associated with a reduced risk of HBV-related HCC.

Perioperative antiplatelet in elderly patients aged over 70 years treated with proximal femur fracture: continue or discontinue?

Background

Antiplatelet medication has been frequently performed in elderly patients with hip fracture, because of comorbidities. This observational cohort study was to evaluate the effect of continuous perioperative antiplatelet medication on the outcomes after cephalomedullary nailing (CMN) in elderly patients with a proximal femur fracture.

Methods

One hundred and sixty-two consecutive patients aged ≥70 years undergoing CMN for proximal femur fracture between January 2015 and January 2017 were recruited. Of the 162 patients, 47 (study group) taking antiplatelets preoperatively due to comorbidities were compared with 107 (control group) who were not on antiplatelets. 8 patients taking anticoagulant medication were excluded. Postoperative hemoglobin (Hb) and hematocrit (Hct) levels, transfusion amount and estimated blood loss (EBL), occurrence of venous thromboembolism (VTE) and delirium, intensive care unit (ICU) admission, complications, length of hospital stay, readmission, and in-hospital and 1-year mortalities were measured and compared between the two groups.

Results

A higher number of patients in the study group had concomitant cardiovascular (p = 0.006) and endocrinologic (p = 0.004) diseases, received perioperative transfusion (p = 0.003), and were admitted to ICU postoperatively (p = 0.014). However, there were no significant differences in postoperative Hb and Hct levels, EBL, length of hospital stay, and the incidences of VTE and delirium between the two groups. In addition, in-hospital and 1-year mortalities as well as postoperative complications showed no significant differences between both groups.

Conclusions

CMN can be performed without delay in elderly patients with proximal femoral fracture receiving antiplatelet therapy prior to admission without discontinuing antiplatelets, and is as safe as in patients who are not on antiplatelet medication. However, more caution is required with respect to transfusions and ICU care after surgery in these patients.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2504-5) contains supplementary material, which is available to authorized users.

A Review of Antiplatelet Activity of Traditional Medicinal Herbs on Integrative Medicine Studies

Thrombotic events mainly occurred by platelet activation and aggregation. The vascular occlusion causes serious disease states such as unstable angina, ischemic stroke, and heart attack. Due to the pervading of thrombotic diseases, new antiplatelet drugs are necessary for preventing and treating arterial thrombosis without adverse side effects. Traditional medicinal herbs have been used for the treatment of human ailments for a long time. The clinically useful and safe products from traditional medicinal herbs were identified and developed in numerous pharmacological approaches. A complementary system of traditional medicinal herbs is a good candidate for pharmacotherapy. However, it still has a limitation in its function and efficacy. Thus, it is necessary to study the mode of action of traditional medicinal herbs as alternative therapeutic agents. In this review, we focused on our current understanding of the regulatory mechanisms of traditional medicinal herbs in antiplatelet activity and antithrombotic effect of traditional medicinal herbs on platelet function.

Effectiveness of Platelet Function Analyzer-100 for Laboratory Detection of Anti-Platelet Drug-Induced Platelet Dysfunction

BACKGROUND

High on-treatment platelet reactivity (HTPR) is the phenomenon wherein patients exhibit normal platelet activity in laboratory testing despite adequate adherence to anti-platelet treatment. We investigated the detection rates of Platelet Function Analyzer (PFA)-100 (Dade Behring AG, Düdingen, Switzerland) for drug-induced platelet dysfunction and analyzed potential contributors to HTPR with practical PFA-100 data over six years.

METHODS

We used data from 6,957 patients who underwent PFA-100 testing after receiving aspirin, clopidogrel, or non-steroidal anti-inflammatory drugs (NSAIDs). Of these, 6,163 patients were tested with only the collagen/epinephrine cartridge (Col/EPI) of PFA-100; 794 were tested with both Col/EPI and the collagen/ADP cartridge (Col/ADP). We calculated PFA-100 closure time (CT) for each drug and compared the clinical and laboratory characteristics of the patients with prolonged CTs and normal CTs (i.e., HTPR).

RESULTS

In Col/EPI, 73.2% (365/499), 72.6% (390/537), and 55.3% (3,442/6,228) patients showed prolonged CTs for aspirin, clopidogrel, and NSAIDs, respectively. In Col/ADP, prolonged CTs were observed in 37.4% (34/91), 43.2% (35/81), and 29.6% (200/676) of patients receiving aspirin, clopidogrel, and NSAIDs, respectively. Of the patients tested with both cartridges, 88.9% (48/54), 95.3% (41/43), and 89.0% (577/648) of the patients receiving aspirin, clopidogrel, and NSAIDs had prolonged CTs, and 10.0% (79/794) showed normal CTs regardless of drugs. For clopidogrel users (both cartridges), there were more patients with malignancies in the normal CT than prolonged CT group.

CONCLUSIONS

PFA-100 is not sufficiently effective for laboratory screening of drug-induced platelet dysfunction. Malignancy may contribute to clopidogrel-related HTPR in PFA-100.

Early prediction of severity in acute ischemic stroke and transient ischemic attack using platelet parameters and neutrophil-to-lymphocyte ratio

BACKGROUND

It is still not easy to predict severity promptly in patients with acute ischemic stroke (AIS) and transient ischemic attack (TIA). We investigated that platelet parameters or combinations of them could be a useful tool for early prediction of severity of AIS and TIA at admission and after 3 months.

METHODS

We prospectively recruited 104 patients newly diagnosed with AIS and TIA. We investigated their neutrophil-to-lymphocyte ratio (NLR) and platelet parameters. According to the Modified Rankin Scale scores, the patients were divided into two groups.

RESULTS

In receiver operating characteristic (ROC) curve analyses, mean platelet volume (MPV), NLR/platelet count (PLT), MPV/PLT, MPV*NLR, and MPV*NLR/PLT showed statistically significant results in both at admission and after 3 months. Values of area under ROC curves for those tests at admission were 0.646, 0.697, 0.664, 0.708, and 0.722, respectively. Also, values after 3 months were 0.591, 0.661, 0.638, 0.662, and 0.689, respectively.

CONCLUSION

MPV*NLR/PLT could be used as a relatively good tool for predicting severity at the time of admission and after 3 months than other parameters or combinations of them. Further studies have to be carried out to investigate the best parameter for predicting the severity of AIS and TIA.

Routine clinical anti-platelet agents have limited efficacy in modulating hypershear-mediated platelet activation associated with mechanical circulatory support

INTRODUCTION

Continuous flow ventricular assist devices (cfVADs) continue to be limited by thrombotic complications associated with disruptive flow patterns and supraphysiologic shear stresses. Patients are prescribed complex antiplatelet therapies, which do not fully prevent recurrent thromboembolic events. This is partially due to limited data on antiplatelet efficacy under cfVAD-associated shear conditions.

MATERIALS AND METHODS

We investigated the efficacy of antiplatelet drugs directly acting on three pathways: (1) cyclooxygenase (aspirin), (2) phosphodiesterase (dipyridamole, pentoxifylline, cilostazol), and (3) glycoprotein IIb-IIIa (eptifibatide). Gel-filtered platelets treated with these drugs were exposed for 10min to either constant shear stresses (30dyne/cm² and 70dyne/cm²) or dynamic shear stress profiles extracted from simulated platelet trajectories through a cfVAD (Micromed DeBakey). Platelet activation state (PAS) was measured using a modified prothrombinase-based assay, with drug efficacy quantified based on PAS reduction compared to untreated controls.

RESULTS AND CONCLUSIONS

Significant PAS reduction was observed for all drugs after exposure to 30dyne/cm² constant shear stress, and all drugs but dipyridamole after exposure to the 30th percentile shear stress waveform of the cfVAD. However, only cilostazol was significantly effective after 70dyne/cm² constant shear stress exposure, though no significant reduction was observed upon exposure to median shear stress conditions in the cfVAD. These results, coupled with the persistence of reported clinical thrombotic complication, suggest the need for the development of new classes of drugs that are especially designed to mitigate thrombosis in cfVAD patients, while reducing or eliminating the risk of bleeding.

Early determination of clopidogrel responsiveness by platelet reactivity index identifies patients at risk for cardiovascular events after myocardial infarction

While acute myocardial infarction (MI) is associated with impaired clopidogrel responsiveness, systematic evaluation is lacking due to the inability of functional aggregation-based assays to analyse clopidogrel responsiveness in the presence of glycoprotein IIb/IIIa inhibitors. Using the P2Y12-specific, non-aggregation-based platelet-reactivity-index (PRI) we assessed clopidogrel responsiveness in patients with acute MI. Clopidogrel responsiveness was determined 24 hours (h) after loading with 600 mg clopidogrel in 54 patients with acute MI admitted for coronary intervention. A PRI > 50% was considered as suboptimal inhibition. Overall response in MI patients was suboptimal with a median PRI of 58%. Diabetes, low high-density lipoprotein and pre-hospital clopidogrel loading were associated with impaired clopidogrel responsiveness. Patients loaded at first medical contact had a significantly weaker platelet inhibition by clopidogrel after 24 h (PRI 63%) compared to those loaded peri-interventionally (PRI 54%, p=0.014). Clinical outcome was assessed as a combination of cardiac death, non-fatal MI, stent thrombosis, ischaemic stroke, and urgent target vessel revascularisation after 12 months. The pre-selected cut-off of PRI ≤ 50% yielded a sensitivity of 87% at a specificity of 26%, whereas a PRI ≤ 57% determined by receiver-operating characteristics (ROC)-analysis yielded a sensitivity of 80% at a specificity of 56% (event rate: PRI ≤ 57%: 12.0%; PRI > 57%: 41.4%, p=0.0136). In conclusion, PRI detects clopidogrel responsiveness in acute MI patients requiring glycoprotein IIb/IIIa antagonism; and impaired clopidogrel responsiveness predisposes to clinical events. Pre-hospital clopidogrel loading was associated with impaired response and more adverse events challenging the concept of earliest oral clopidogrel loading in MI patients.

Prevalence of poor biological response to clopidogrel

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verify -now® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

High on-treatment platelet reactivity – definition and measurement

In the last decade, several studies revealed inter-patient response variability to antiplatelet agents: patients who display negligible or no responses to these drugs are considered poor responders, or “resistant” to treatment. In order to identify poor responders to an antiplatelet drug, laboratory tests of platelet function that specifically explore the platelet activation pathway that is targeted by the drug should be utilised. In addition, they should be performed both at baseline and during treatment: however, most studies explored platelet function during antiplatelet treatment, in order to identify those patients with “high on-treatment platelet reactivity” (HPR), which exposes them to increased risk of major adverse cardiovascular events (MACE). Many tests of platelet function have been used, most of which are able to identify patients at risk of MACE. Unfortunately, universal cut-off values for HPR have not been clearly established yet. In addition, the concordance among different tests in the identification of patients at risk is very poor and the most effective and safe treatment for patients at risk is still unknown.

Comparison of current platelet functional tests for the assessment of aspirin and clopidogrel response

The two most widely used antiplatelet drugs in the world are aspirin and clopidogrel. However, some patients on aspirin and/or clopidogrel therapy do not respond appropriately to either aspirin or clopidogrel. This phenomenon is usually called “aspirin/clopidogrel resistance”. Several platelet function tests have been used in various studies for the assessment of aspirin and clopidogrel resistance in healthy individuals and patients admitted in cardiology departments. An accurate assessment of platelet response to aspirin/clopidogrel could benefit patients by proposing tailored-antiplatelet therapy based on test results. However, there is a clear lack of standardisation of such techniques and their analytical variability may induce misinterpretation. After a quick report of the mechanisms responsible for aspirin/clopidogrel resistance, we describe the pre-analytical aspects and the analytical performances of current platelet function tests (Light-transmission aggregometry, whole-blood aggregometry, VerifyNow®, Platelet Function Analyzer®, thromboelastography, VASP assay) that are used for the assessment of aspirin/clopidogrel resistance in clinical studies. Considering the different variables that have to be taken into account with each of the platelet function tests, a particular attention should be paid when interpreting results.

Comparative Study of Effects of Vonoprazan and Esomeprazole on Antiplatelet Function of Clopidogrel or Prasugrel in Relation to CYP2C19 Genotype

Drug-drug interaction between antiacid and antiplatelet agents has not been fully elucidated. Vonoprazan, a new potassium competitive acid blocker, has been available in Japan. CYP2C19 and CYP3A4 are involved in the metabolism of clopidogrel, prasugrel, esomeprazole, and vonoprazan. Using a P2Y12 assay, we compared the effects of vonoprazan and esomeprazole on the antiplatelet functions of clopidogrel or prasugrel in 31 healthy Japanese volunteers (14 CYP2C19 homo-extensive (homo-EMs), nine hetero-extensive (hetero-EMs), and eight poor metabolizers (PMs)). Vonoprazan decreased the median inhibition of platelet aggregation (IPA) values of clopidogrel and prasugrel more potently than esomeprazole (P < 0.001 for clopidogrel and P = 0.011 for prasugrel). The same tendencies were observed when stratified by CYP2C19 genotype groups (P = 0.004 in homo-EMs, 0.033 in hetero-EMs, and 0.043 in PMs). Vonoprazan attenuated the antiplatelet function of clopidogrel more potently than esomeprazole. Esomeprazole did not affect that of prasugrel irrespective of CYP2C19 genotype.

Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications

Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.

Global Trends in Aspirin Resistance-Related Research from 1990 to 2015: A Bibliometric Analysis

Aspirin resistance can be defined as the inability of the usual dose of aspirin medication to produce its antithrombotic effect. Patients with diabetes or cardiovascular disease are at higher risk of stroke, myocardial infarction or cardiovascular death due to aspirin resistance. The aim of this bibliometric study was to identify and analyse the status and trends of aspirin resistance research production at global level through publications indexed in the Scopus database; this will shed new light on future research trends and help researchers predict dynamic direction of research. Literature search using the Scopus database was conducted to assess publications related to aspirin resistance. The selected publications included the terms related to aspirin resistance in the title, abstract or keywords. The searching was accomplished on 20 March 2016 and can be considered to include all publications up to 31 December 2015. Global cumulative publication output on aspirin resistance consists of 986 papers during 1990-2015. Among the 986 documents, 19 (1.9%) were published before 2000, 567 (57.5%) were published from 2000 to 2009 and 400 (40.6%) were published from 2010 to 2015, with peak of publications on this topic in 2008. The leading country in the field of aspirin resistance was the United States, which had the greatest counts of independent articles (165) and international collaboration articles (44). Turkey was in the second rank with 78 articles, followed by Italy (68), the UK (62) and Poland (60). The total number of citations for all documents was 26,342, and the average citations per document were 26.7. The h-index for all aspirin resistance publications was 82. This study presents the results of the first bibliometric study (including quantitative and qualitative analysis) of scientific publications in the field of aspirin renitence at global level. Aspirin resistance-related researches have notably increased in the last years, especially from 2000 to 2015. The United States is the most prolific country, not only in research quantity but also in quality. Furthermore, Turkey and European countries provided more research related to aspirin resistance than other regions such as the developing countries.

Remote Assessment of Platelet Function in Patients with Acute Stroke or Transient Ischaemic Attack

BACKGROUND

The TARDIS trial assessed the safety and efficacy of intensive versus guideline antiplatelet agents given for one month in patients with acute stroke or TIA. The aim of this substudy was to assess the effect of antiplatelet agents taken at baseline on platelet function reactivity and activation.

METHODS

Platelet function, assessed by remotely measured surface expression of P-selectin, was assessed in patients at their time of randomisation. Data are median fluorescence values.

RESULTS

The aspirin P-selectin test demonstrated that platelet expression was lower in 494 patients taking aspirin than in 162 patients not: mean 210 (SD 188) versus 570 (435), difference 360.3 (95% CI 312.2-408.4) (2p < 0.001). Aspirin did not suppress P-selectin levels below 500 units in 23 (4.7%) patients. The clopidogrel test showed that platelet reactivity was lower in 97 patients taking clopidogrel than in 585 patients not: 655 (296) versus 969 (315), difference 314.5 (95% CI 247.3-381.7) (2p < 0.001). Clopidogrel did not suppress P-selectin level below 860 units in 24 (24.7%) patients.

CONCLUSIONS

Aspirin and clopidogrel suppress stimulated platelet P-selectin, although one-quarter of patients on clopidogrel have high on-treatment platelet reactivity. Platelet function testing may be performed remotely in the context of a large multicentre trial. Trial registration ISRCTN47823388.

Resveratrol suppresses pulmonary tumor metastasis by inhibiting platelet-mediated angiogenic responses

BACKGROUND

To explore the impact of Resveratrol (RSV) on the angiogenic potential of activated platelets and to elucidate the underlying mechanism.

METHODS

Vascular endothelial growth factor concentrations were measured by enzyme-linked immunosorbent assay. Capillary tube formation assay was used to examine the impact of RSV on the angiogenic potential of activated platelets. The levels of cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) in the supernatant were evaluated using corresponding enzyme-linked immunosorbent assay kits. Immunoblotting assays were used to determine the expression of vasodilator-stimulated phosphoprotein and Akt phosphorylation. A pulmonary metastasis experiment with male nude mice model was performed to test the effect of RSV on pulmonary metastasis and angiogenesis in vivo.

RESULTS

RSV inhibited platelets-mediated angiogenic responses induced by adenosine diphosphate (ADP)ADP through increased cGMP generation and cGMP-mediated vasodilator-stimulated phosphoprotein phosphorylation along with reduced intracellular Ca²⁺ mobilization. In addition, RSV attenuated the platelet secretion and angiogenic responses induced by A549 cells in vitro and suppressed A549 lung cancer metastasis and angiogenesis in nude mice.

CONCLUSIONS

RSV is a potential therapeutic drug for the prevention of tumor metastasis by interrupting the platelet-tumor cell amplification loop.