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Introduction. Patients undergoing elective myocardial revascularization require 6 months of dual antiplatelet therapy (DAPT), including aspirin and clopidogrel. In patients with multifocal atherosclerotic lesion (MFA), it may be reasonable to extend the DAPT. Additional consideration of laboratory parameters, which reflect sensitivity to clopidogrel, may be useful in assessing the effectiveness and safety of prolongation DAPT.Aim. To determine the significance of laboratory parameters reflecting sensitivity to clopidogrel in assessing the prognosis of patients with MFA receiving long-term DAPT after myocardial revascularization.Materials and methods. 128 patients with coronary artery disease (CAD) and MFA were included from the prospective register of antithrombotic therapy (REGATTA-1), ClinicalTrials NCT04347200. Inclusion criteria were elective myocardial revascularization, the use of DAPT planned for at least one year and additional determination sensitivity to clopidogrel – residual platelet reactivity and polymorphisms of the CYP2C19* gene. Thrombotic events (TO) in any vascular beds and hemorrhagic complications(GO) (BARC 2–5).Results. The median of DAPT was 380 days, IQR (346. 447). The total incidence of thrombotic events and hemorrhagic complications (the majority – BARC 2) were 9.9 and 4.4 cases per 100 patient-years. The frequency of bleeding events was 4.4 cases per 100 patient-years. There was no association of TO with the PRU and pharmacogenetic parameters. CYP2C19*17 allele carriers tended to have a higher frequency of GO rates compared compared to wild genotype carriers (63% versus 29%, p = 0.05). The frequency of GO in patients with PRU 147 (two lower quintiles) was higher compared with the frequency of GO in the three upper quintiles of the distribution: 12% vs. 3%, p = 0.041. PRU lost significance in multivariate analysis and an independent laboratory predictor of GO was the carriage of CYP2C19*17 alleles (HR 4.8).Conclusion. In patients with MFA who are candidates for long-term DATT after myocardial revascularization, an additional pharmacogenetic assessment of the effect of clopidogrel (allelic variants of CYP2C19*17) can be discussed in order to predict bleeding

This review aims to examine the complex interaction between dyslipidemia, platelet function, and related drug treatments. In particular, the manuscript provides an overview of the effects of major hypolipidemic drugs on platelet function. Indeed, growing evidence supports the view that statins, ezetimibe, PCSK9 inhibitors, inclisiran, and icosapent ethyl also act as antithrombotics. It is known that platelets play a key role not only in the acute phase of coronary syndromes but also in the early phase of atherosclerotic plaque formation. The goal of cholesterol-lowering therapy is to reduce cardiovascular events. The direct effects of cholesterol-lowering drugs are widely described in the literature. Lowering LDL-c (low-density lipoprotein cholesterol) by 1 mmol/L results in a 22–23% reduction in cardiovascular risk. Numerous studies have examined the direct antithrombotic effects of these drugs on platelets, endothelium, monocytes, and smooth muscle cells, and thus, potentially independent of blood LDL-cholesterol reduction. We reviewed in vitro and in vivo studies evaluating the complex interaction between hypercholesterolemia, hypertriglyceridemia, platelet function, and related drug treatments. First, we discussed the role of statins in modulating platelet activation. Discontinuation of statin therapy was associated with increased cardiovascular events with increased ox-LDL, P-selectin, and platelet aggregation. The effect of PCSK9-I (inhibitors of proprotein convertase subtilisin/kexin type 9, PCSK9 involved in the degradation of LDL receptors in the liver) was associated with a statistically significant reduction in platelet reactivity, calculated in P2Y12 reaction units (PRU), in the first 14 days and no difference at 30 days compared to placebo. Finally, in patients with hypertriglyceridemia, the REDUCE-IT study showed that icosapent ethyl (an ethyl ester of eicosapentaenoic acid that reduces triglyceride synthesis and improves triglyceride clearance) resulted in a 25% reduction in ischemic events and cardiovascular death. However, to date, there is not yet clear clinical evidence that the direct antithrombotic effects of the drugs may have a beneficial impact on outcomes independently from the reduction in LDL-C or triglycerides. [ABSTRACT FROM AUTHOR]

According to recommendations of ESC 2020-year, de-escalation of therapy with a P2Y12 receptor inhibitor (transition from prasugrel or ticagrelor to clopidogrel) It can be considered as an alternative strategy of dual antiplatelet therapy (DAPT) for patients with acute coronary syndrome (ACS) who are unsuitable for the use of a strong platelet inhibitor.De-escalation can be performed based on an individual clinical evaluation under the supervision of platelet function testing or CYP2C19 genotyping, depending on the patient’s risk profile and the availability of appropriate diagnostic methods. The optimal dosage of strong P2Y12 receptor inhibitors, such as ticagrelor or prasugrel is not entirely clear and is especially difficult to define for patients of Asian nationality.The article describes a clinical case of antiplatelet therapy de-escalation, particularly a dose reduction of the potent P2Y12 receptor inhibitor ticagrelor in a patient after percutaneous coronary intervention (PCI) with a high risk of bleeding based on platelet function determination and genetic testing. A 47-year-old patient of Kazakh nationality was hospitalized with gastrointestinal bleeding.Given bleeding type 3 by BARC (Bleeding Academic Research Consortium) associated with DAPT, it was decided to apply a strategy to de-escalate antiplatelet therapy under the control of platelet function testing (PFT) and genetic testing.In this case, replacement of ticagrelor with the weak P2Y12 receptor inhibitor clopidogrel was not possible as the patient appeared to be a carrier of the CYP2C19*2 polymorphism contributing to loss of function of the cytochrome P-450(CYP) enzyme.

This review aims to examine the complex interaction between dyslipidemia, platelet function, and related drug treatments. In particular, the manuscript provides an overview of the effects of major hypolipidemic drugs on platelet function. Indeed, growing evidence supports the view that statins, ezetimibe, PCSK9 inhibitors, inclisiran, and icosapent ethyl also act as antithrombotics. It is known that platelets play a key role not only in the acute phase of coronary syndromes but also in the early phase of atherosclerotic plaque formation. The goal of cholesterol-lowering therapy is to reduce cardiovascular events. The direct effects of cholesterol-lowering drugs are widely described in the literature. Lowering LDL-c (low-density lipoprotein cholesterol) by 1 mmol/L results in a 22–23% reduction in cardiovascular risk. Numerous studies have examined the direct antithrombotic effects of these drugs on platelets, endothelium, monocytes, and smooth muscle cells, and thus, potentially independent of blood LDL-cholesterol reduction. We reviewed in vitro and in vivo studies evaluating the complex interaction between hypercholesterolemia, hypertriglyceridemia, platelet function, and related drug treatments. First, we discussed the role of statins in modulating platelet activation. Discontinuation of statin therapy was associated with increased cardiovascular events with increased ox-LDL, P-selectin, and platelet aggregation. The effect of PCSK9-I (inhibitors of proprotein convertase subtilisin/kexin type 9, PCSK9 involved in the degradation of LDL receptors in the liver) was associated with a statistically significant reduction in platelet reactivity, calculated in P2Y12 reaction units (PRU), in the first 14 days and no difference at 30 days compared to placebo. Finally, in patients with hypertriglyceridemia, the REDUCE-IT study showed that icosapent ethyl (an ethyl ester of eicosapentaenoic acid that reduces triglyceride synthesis and improves triglyceride clearance) resulted in a 25% reduction in ischemic events and cardiovascular death. However, to date, there is not yet clear clinical evidence that the direct antithrombotic effects of the drugs may have a beneficial impact on outcomes independently from the reduction in LDL-C or triglycerides.

In the article, a review is given of the facts that determined contemporary views of the role of clopidogrel in the treatment of acute coronary syndrome. The author described a history of the clinical studies of clopidogrel in acute coronary syndrome (ACS), analysed its role in the current approaches to the treatment of the disease during the widespread use of other platelet P2Y12 receptor antagonists (ticagrelor and prasugrel).The article discusses circumstances, when clopidogrel may have additional advantages, particularly the role of adherence to prolonged double antiplatelet therapy, as well as situations, when sever suppression of platelet function can be decreased (treatment de-escalation). According to a prospective randomized open-label PoPular Age study, clopidogrel combined with acetylsalicylic acid in patients with ACS without persistent ST segment elevations at the age of ≥70 years showed better adherence to treatment over the coming year as compared with clopidogrel combined with ticagrelor or prasugrel. As a result, these two approaches had comparable efficacy. Today, treatment de-escalation is a necessary measure to extend the double antiplatelet therapy in cases, when continued administration of prasugrel or ticagrelor appears unacceptable. There is insufficient evidence for the routine implementation of de-escalation in stented patients with ACS, although a small prospective, one-centre randomized open-label ToPIC study shows that this approach is safe.The author provides a review of the results of recently presented prospective studies on the choice of a platelet P2Y12 receptor antagonist for long-term treatment of acute coronary syndrome, taking into account the residual platelet reactivity and cytochrome p450 2c19 genetic polymorphisms. Among them are multicenter open randomized clinical TRoPICAL-ACS study, multicenter randomized open-label PoPular Genetics and TAILoR PCI studies. According to the study results, the long-term outcomes in stented patients with ACS with a good response to clopidogrel assessed by the residual functional activity of platelets or by studying cytochrome p450 2c19 genetic polymorphisms may not be worse than those during use of prasugrel or ticagrelor.

Cigarette smoking is an important cardiovascular risk factor, causing morbidity and mortality. There are many original studies on the impact of smoking, but its influence on platelet ADP-P2Y12 receptor inhibitors lack consistency. Thus, we conducted a systematic review and meta-analysis of already existing data/studies to further explore this issue. PubMed, Web of science, EMBASE, Clinical Trials, and the Cochrane Library were searched from inception to March 2018. Studies investigating the residual platelet reactivity categorized by smoking status and patients treated with platelet ADP-P2Y12 receptor inhibitors qualified the inclusion criteria. The primary outcome was P2Y12 reaction unit (PRU) value measured by VerifyNow P2Y12 assay, compared with different smoking status in ADP-P2Y12 receptor inhibitors treatment groups. Secondary outcome was post-treatment with 5 μmol/L ADP-inhibition of platelet aggregation (ADP-IPA) measured by light transmittance aggregometry (LTA). Of the 4954 citations retrieved, 12 studies involving 16 296 patients with acute coronary syndrome and/or stent deployment using platelet ADP-P2Y12 receptor inhibitors were included for meta-analysis. Pooled analysis revealed that PRU values of current smokers were 25.70 lower than nonsmokers (95% CI −38.81 to −12.60, p = 0.0001), getting better effects of antiplatelet treatment. In the smoking extent subgroup analysis, patients smoking >10 cigarettes/day shown about 46.49 lower of PRU values than patients smoking

Abstract Background Platelet inhibition is important for patients with coronary artery disease. When dual antiplatelet therapy (DAPT) is required, a P2Y12-antagonist is usually recommended in addition to standard aspirin therapy. The most used P2Y12-antagonists are clopidogrel, prasugrel and ticagrelor. Despite DAPT, some patients experience adverse cardiovascular events, and insufficient platelet inhibition has been suggested as a possible cause. In the present review we have performed a literature search on prevalence, mechanisms and clinical implications of resistance to P2Y12 inhibitors. Methods The PubMed database was searched for relevant papers and 11 meta-analyses were included. P2Y12 resistance is measured by stimulating platelets with ADP ex vivo and the most used assays are vasodilator stimulated phosphoprotein (VASP), Multiplate, VerifyNow (VN) and light transmission aggregometry (LTA). Discussion/conclusion The frequency of high platelet reactivity (HPR) during clopidogrel therapy is predicted to be 30%. Genetic polymorphisms and drug-drug interactions are discussed to explain a significant part of this inter-individual variation. HPR during prasugrel and ticagrelor treatment is estimated to be 3–15% and 0–3%, respectively. This lower frequency is explained by less complicated and more efficient generation of the active metabolite compared to clopidogrel. Meta-analyses do show a positive effect of adjusting standard clopidogrel treatment based on platelet function testing. Despite this, personalized therapy is not recommended because no large-scale RCT have shown any clinical benefit. For patients on prasugrel and ticagrelor, platelet function testing is not recommended due to low occurrence of HPR.

Cigarette smoking is an important cardiovascular risk factor, causing morbidity and mortality. There are many original studies on the impact of smoking, but its influence on platelet ADP-P2Y12 receptor inhibitors lack consistency. Thus, we conducted a systematic review and meta-analysis of already existing data/studies to further explore this issue. PubMed, Web of science, EMBASE, Clinical Trials, and the Cochrane Library were searched from inception to March 2018. Studies investigating the residual platelet reactivity categorized by smoking status and patients treated with platelet ADP-P2Y12 receptor inhibitors qualified the inclusion criteria. The primary outcome was P2Y12 reaction unit (PRU) value measured by VerifyNow P2Y12 assay, compared with different smoking status in ADP-P2Y12 receptor inhibitors treatment groups. Secondary outcome was post-treatment with 5 μmol/L ADP-inhibition of platelet aggregation (ADP-IPA) measured by light transmittance aggregometry (LTA). Of the 4954 citations retrieved, 12 studies involving 16 296 patients with acute coronary syndrome and/or stent deployment using platelet ADP-P2Y12 receptor inhibitors were included for meta-analysis. Pooled analysis revealed that PRU values of current smokers were 25.70 lower than nonsmokers (95% CI −38.81 to −12.60, p = 0.0001), getting better effects of antiplatelet treatment. In the smoking extent subgroup analysis, patients smoking >10 cigarettes/day shown about 46.49 lower of PRU values than patients smoking <10 cigarettes/day (p < 0.00001). Racial subgroup analyses found that smokers had increased platelet inhibition in the Caucasian population. Further, pooled analysis of ADP-IPA values for 1658 patients from five studies showed a significantly lower residual platelet reactivity in current smokers compared to that in nonsmokers (MD = −4.19; 95% CI −6.55 to −1.83; p = 0.0005). This systematic review and meta-analysis suggested that smokers have increased platelet inhibition and lower aggregation in response to clopidogrel than nonsmokers. These residual platelet reactivity observations may help to explain differential clinical outcomes in smokers vs. nonsmokers in large scale clinical trials. [ABSTRACT FROM AUTHOR]

Abstract Background The mechanisms behind residual platelet reactivity (RPR) despite aspirin treatment are not established. It has been shown that coronary artery disease (CAD) patients with high on-aspirin RPR have elevated levels of von Willebrand factor (vWF). ADAMTS13 is a metalloprotease cleaving ultra large vWF multimers into less active fragments. Our aim was to investigate whether ADAMTS13 and vWF/ADAMTS13 ratio were associated with high RPR, and further with clinical endpoints after 2 years. Methods Stable aspirin-treated CAD patients (n = 999) from the ASCET trial. RPR was assessed by PFA-100. ADAMTS13 antigen and activity were analysed using chromogenic assays. Endpoints were a composite of acute myocardial infarction, stroke and death. Results The number of patients with high RPR was 258 (25.8%). Their serum thromboxane B2 (TxB2) levels were low, indicating inhibition of COX-1. They had significantly lower levels of ADAMTS13 antigen compared to patients with low RPR (517 vs 544 ng/mL, p = 0.001) and significantly lower ADAMTS13 activity (0.99 vs 1.04 IU/mL, p = 0.020). The differences were more pronounced when relating RPR to ratios of vWF/ADAMTS13 antigen and vWF/ADAMTS13 activity (p

Evaluation of platelet function with subsequent modification of antiplatelet therapy regimen is one of the areas of personalized medicine. Analysis of the causes of inadequate antiplatelet action of clopidogrel, the association of residual platelet reactivity with clinical outcomes and a review of the research on the change of antiplatelet therapy in patients with ischemic heart disease after percutaneous interventions based on the results of platelet function testing, were the aim of this review.

Background: The mechanisms behind residual platelet reactivity (RPR) despite aspirin treatment are not established. It has been shown that coronary artery disease (CAD) patients with high on-aspirin RPR have elevated levels of von Willebrand factor (vWF). ADAMTS13 is a metalloprotease cleaving ultra large vWF multimers into less active fragments. Our aim was to investigate whether ADAMTS13 and vWF/ADAMTS13 ratio were associated with high RPR, and further with clinical endpoints after 2 years. Methods: Stable aspirin-treated CAD patients (n = 999) from the ASCET trial. RPR was assessed by PFA-100. ADAMTS13 antigen and activity were analysed using chromogenic assays. Endpoints were a composite of acute myocardial infarction, stroke and death. Results: The number of patients with high RPR was 258 (25.8%). Their serum thromboxane B2 (TxB2) levels were low, indicating inhibition of COX-1. They had significantly lower levels of ADAMTS13 antigen compared to patients with low RPR (517 vs 544 ng/mL, p = 0.001) and significantly lower ADAMTS13 activity (0.99 vs 1.04 IU/mL, p = 0.020). The differences were more pronounced when relating RPR to ratios of vWF/ADAMTS13 antigen and vWF/ADAMTS13 activity (p <0.001, both). We found an inverse correlation between vWF and ADAMTS13 antigen (r = -0.14, p < 0.001) and ADAMTS13 activity (r = -0.11, p < 0.001). No correlations between TxB2 and ADAMTS13 antigen or activity, were observed, implying that ADAMTS13 is not involved in TxB2 production. Patients who experienced endpoints (n = 73) had higher vWF level (113 vs 105%, p = 0.032) and vWF/ADAMTS13 antigen ratio (0.23 vs 0.20, p = 0.012) compared to patients without. When dichotomizing vWF/ADAMTS13 antigen at median level we observed that patients above median had higher risk for suffering endpoints, with an adjusted OR of 1.86 (95% CI 1.45, 2.82). Conclusion: These results indicate that ADAMTS13 is of importance for RPR, and that it in combination with vWF also is associated with clinical endpoints in stable CAD patients on aspirin. Trial registration: Clinicaltrials.gov NCT00222261. Registered 13.09.2005. Retrospectively registered. [ABSTRACT FROM AUTHOR]

Background High on treatment platelet reactivity (HTPR) is common in patients receiving clopidogrel following an acute coronary syndrome (ACS); it's also associated with increased morbidity and mortality. More potent and predictable antiplatelet drugs have addressed this issue at the expense of increased bleeding. Identification of HTPR and the targeted use of more potent antiplatelet drugs has, so far, broadly failed. We investigate this approach in terms of the timing of platelet function testing and how this can impact on the ability of these bedside tests to predict HTPR around the time of coronary intervention. Methods High risk ACS patients treated with 5 days of clopidogrel had platelet function assessed using the multiple electrode aggregometry system (MEA) pre, post and 24 h following percutaneous coronary intervention (PCI). Simultaneous detailed analysis of platelet status was undertaken with quantification of platelet bound and soluble p-selectin and mass spectrometry quantification of the eicosanoid 12-HETE. Results As assessed by MEA 40.5% of patients had HTPR pre-PCI; mean aggregation units (AU) in response to ADP were 499.1 ± 46.3 pre-PCI, 407.6 ± 37.7 post-PCI and 269.1 ± 24.6 AU 24 h post-PCI (pre to post PCI p > 0.05, pre to 24 h post-PCI p = 0.0002). This highly significant drop in platelet reactivity was contrasted with on-going expression of platelet bound p-selectin, increased soluble p-selectin and rising 12-HETE concentrations. Conclusions This study outlines significant changes in ex-vivo platelet aggregation that occur within 24 h of PCI in high risk NSTEMI patients using bedside PFT. Whilst there were no changes in antiplatelet therapy during the study period its clear that timing is crucial when assessing high on treatment residual platelet activity. [ABSTRACT FROM AUTHOR]

Background Immature platelets are less responsive to the effects of antiplatelet drugs and contain messenger ribonucleic acid that is translationally active. They can be measured easily using an automated hematoanalyzer and reported as part of the complete blood count. Objectives The purpose of this study was to determine the prognostic significance of elevated immature platelet count (IPC) in patients with coronary artery disease (CAD). Methods In this prospective cohort study in patients with CAD, patients underwent IPC measurement and were then followed up for the composite endpoint of major adverse cardiovascular events (MACE), defined as a composite of all-cause mortality, myocardial infarction, unplanned revascularization, or hospitalization for angina. For the purposes of analysis, patients were stratified into tertiles of IPC. Results Eighty-nine patients were followed up for a median of 31 months. Stratification to the high IPC tertile was associated with higher rates of MACE compared with the intermediate and low tertiles (60% vs. 24% vs. 16%, respectively; p < 0.001). Time-dependent receiver-operating characteristic analysis revealed that an IPC level ≥7,632 platelets/μl was 70.7% sensitive and 82.1% specific for MACE. After adjustment for age, admission diagnosis, index revascularization, heart failure, smoking, hematocrit, and baseline platelet count, patients with an IPC level ≥7,632 platelets/μl were more likely to experience a MACE (hazard ratio: 4.65; 95% confidence interval: 1.78 to 12.16; p < 0.002). Conclusions IPC is a novel biomarker for MACE risk stratification in patients with CAD. Future studies should focus on the utilization of this marker for individualized antiplatelet therapy. [ABSTRACT FROM AUTHOR]

Objective. Several platelet function test systems exist for the evaluation of the platelet inhibitory effect in patients on P2Y12 inhibitors and/or acetylsalicylic acid (ASA, aspirin) therapy. Studies comparing different available assays found only a poor correlation. The objective of the present study was to evaluate the correlation and agreement between single electrode (SEA) and multiple electrode (MEA) aggregometry. Methods and results. In whole blood arachidonic acid (AA) and adenosine diphosphate (ADP)-induced platelet aggregation was measured simultaneously using SEA (Chrono-Log) and MEA (Multiplate). We analyzed a total of 226 measurements taken from 58 patients on single ASA therapy or dual antiplatelet therapy with ASA and a thienopyridine. A cut-off value for clopidogrel/prasugrel high on-treatment platelet reactivity (HPR) of > 47 units (U) was chosen for MEA testing using hirudin and > 5 Ohm for SEA with citrate anticoagulated blood samples. The respective cut-off values for ASA HPR were > 30 U for the MEA assay and > 1 Ohm for SEA testing. There was a good correlation of the prevalence of thienopyridine-HPR in both whole blood assays (Spearman rank correlation coefficient r = 0.698) and a good inter-rate accordance (Cohen's Kappa statistic κ = 0.648). For AA-induced aggregation, the correlation of the results obtained was significant ( r = 0.536; p < 0.001) and detecting ASA-HPR revealed a moderate (κ = 0.482) correlation between both impedance aggregometry assays. Conclusion. Platelet function testing using SEA and MEA provided both good accordance and correlation and therefore study results obtained by these two assays similarly enabled the detection of HPR of thienopyridine (and ASA) therapy. [ABSTRACT FROM AUTHOR]

Objectives. High on-aspirin residual platelet reactivity (RPR) after coronary artery bypass grafting (CABG) is a transient phenomenon with important implications for graft patency. This study was designed to determine the role of polymorphisms [TBXA2R (T924C), GPIIIa (PlA1/A2), P2Y1 (A1622G), and GP1Bα (C1018T)] on RPR in Chinese patients undergoing off-pump CABG (OPCAB). Methods. Of 420 patients recruited to this study, 210 patients underwent primary OPCAB and 210 controls with ischemic heart disease received optimal medical therapy. Arachidonic acid-induced platelet aggregation and urinary 11-dehydro thromboxane B2 were measured at baseline and following aspirin administration on days 1, 4, 10, and on 6th month. Four polymorphisms were identified [TBXA2R (T924C), P2Y1 (A1622G), PlA1/A2 and GP1Bα (C1018T)]. Results. On the first post-operative day, 62 patients (29.5%) were with high RPR and 148 (70.5%) were with low RPR. Of the former, 33 (15.7%), 10 (4.6%), and 0 (0%) patients remained with high RPR on days 4, 10, and on 6 month, respectively. No individuals with high RPR was found in controls. Logistic regression identified TBXA2R-924TT (OR = 4.5; 95% CI, 1.8-11.1) and body mass index > 27 kg/m2 (OR = 2.73; 95% CI, 1.1-7.0) as independent risk factors for high on-aspirin RPR. Conclusions. High on-aspirin RPR after OPCAB is associated with genetic polymorphism TBXA2R-924TT and obesity. [ABSTRACT FROM AUTHOR]

Adenosine 5′-diphosphate (ADP) inducible aggregation is used to assess platelet response to thienopyridines. Thrombin receptor-activating peptide-6 (TRAP-6) inducible aggregation may serve as a positive control because it acts via the thrombin receptor protease-activating receptor-1, which is not blocked by thienopyridines. We therefore investigated if TRAP-6 is suitable as a positive control when assessing residual platelet reactivity to ADP. Platelet response to clopidogrel was assessed in 200 patients on dual antiplatelet therapy using ADP inducible platelet aggregation by light transmission aggregometry (LTA), multiple electrode aggregometry (MEA), and the shear-dependent Impact-R. Test specificities were monitored by TRAP-6 inducible platelet aggregation. The aggregation-independent vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay served for comparisons. ADP inducible aggregation was correlated to that by TRAP-6 ( r = 0.33 to 0.72; p < 0.001 for all assays). A linear correlation was seen within MEA ( r = 0.72). LTA TRAP-6 correlated weakly with the VASP assay ( r = 0.19; p = 0.01), while there were no correlations of TRAP-6 responses by MEA or the Impact-R with the VASP assay ( r = 0.03 and −0.09; p > 0.05). In all three assays, differences between ADP and TRAP-6 inducible aggregation varied considerably. Within MEA, TRAP-6 inducible aggregation was almost always stronger than ADP inducible aggregation, while within LTA and the Impact-R, weak responses to ADP were associated with both, weak and strong responses to TRAP-6. In conclusion, the application of TRAP-6 as a positive control for platelet reactivity has major limitations and results need to be cautiously interpreted on an individual basis. [ABSTRACT FROM AUTHOR]

Abstract: Background: Residual platelet reactivity (RPR) on antiplatelet therapy in ischemic heart disease patients is associated with adverse events. Clinical, cellular and pharmacogenetic factors may account for the variable response to antiplatelet treatment. Objective: We sought to explore the interplay of multiple pro-inflammatory and anti-inflammatory cytokines with platelet function in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) on dual antiplatelet therapy. Methods: In 208 ACS patients undergoing PCI on dual antiplatelet therapy we measured platelet function by platelet aggregation with two agonists [1mM arachidonic acid (AA) and 10μM ADP]. IL-1β, IL-1ra, IL-4, IL-6, IL-8, IL-10, IL-12, IP-10, IFN-γ, MCP-1, MIP-1α, MIP-1β, TNF-α, and VEGF levels were determined by using the Bio-Plex cytokine assay (Bio-Rad Laboratories Inc., Hercules, CA, USA). We defined patients with RPR those with platelet aggregation by AA ≥20% and/or ADP (10μmol) ≥70%. Results: We documented a significant association between IP-10, IFN-γ, IL-4 and RPR by both AA- and ADP-induced platelet aggregation after adjustment for age, sex, cardiovascular risk factors, ejection fraction, BMI, vWF and CRP. Patients with pro-inflammatory cytokines not compensated by anti-inflammatory cytokines had higher risk of RPR by both AA and ADP (AA: OR=3.85, 95% CI 1.52–9.74; ADP: OR=2.49, 95% CI 1.33–4.68) with respect to patients with balanced anti-/pro-inflammatory cytokines. Patients with anti-inflammatory response overwhelming pro-inflammatory response have lower risk of RPR (AA: OR=0.55, 95% CI 0.28–1.06; ADP: OR=0.47, 95% CI 0.26–0.87). Conclusion: Our study provides new insights into the interplay of anti-/pro-inflammatory cytokines with platelet hyper-reactivity in high-risk patients. [Copyright &y& Elsevier]

Abstract: Background: The pathophysiologic mechanisms leading to residual platelet reactivity (RPR) on antiplatelet therapy, a condition high prevalent in patients with acute coronary syndrome, are not yet elucidated. In the acute phase of coronary artery disease large amounts of ultra large VWF multimers (ULVWF) are released and cleaved by the activity of ADAMTS-13. Objective: Aim of this study was to evaluate the relationships between VWF antigen (VWF:Ag) levels, collagen binding activity of VWF (VWF:CB), ADAMTS-13 and interleukin-6 (IL-6) levels in affecting platelet response to dual antiplatelet treatment. Methods: In 159 acute coronary syndrome (ACS) patients undergoing percutaneous coronary interventions we measured platelet function by platelet aggregation with two agonists [1 mM arachidonic acid (AA) and 10 μM ADP]. We defined patients with RPR those with platelet aggregation by AA >20% and/or ADP (10 µmol) >70%. Results: We found significantly lower ADAMTS-13 activity, elevated IL-6, VWF:Ag and VWF:CB levels in patients with RPR. A lower ADAMTS-13 activity was present in patients with VWF:Ag and VWF:CB in the upper tertile. At the multivariate analysis ADAMTS-13 activity and IL-6 were independent risk factors for RPR. Conclusion: Our results indicate that ADAMTS-13 activity and IL-6 levels independently affect RPR and suggest that, by different pathways, both are involved in the variable response to antiplatelet therapy. [Copyright &y& Elsevier]

Abstract: Background: Recently, a growing body of evidence on the possible role of residual platelet reactivity (RPR) in affecting clinical events has accumulated. The aim of this study was to systematically assess the relationship between RPR on acetylic salicylic acid (ASA) therapy and the occurrence of recurrent events in a meta-analysis of prospective studies. Methods: A systematic literature search of MEDLINE, EMBASE, Science Citation Index, the Cochrane Systematic Review Database and bibliographies of retrieved articles through May 2007 was conducted. Studies were included if they analysed RPR in coronary heart disease patients in relation to the occurrence of adverse coronary events during follow-up. Results: Eleven prospective studies, incorporating 1952 patients with coronary heart disease followed for a time ranging from 6 days to 4 years, met the inclusion criteria. The pooled analysis demonstrated a significantly increased relative risk of adverse clinical events during follow-up for patients with RPR on ASA therapy (RR: 3.11, 95%CI 1.88–5.15; p <0.0001). Moreover, the association between RPR and cardiovascular recurrences remained to be statistically significant even when subgroup analyses performed according to the duration of follow-up, ASA dosage, characteristics of the study population, and laboratory method were conducted. Conclusions: The present meta-analysis documents a significant association between RPR on ASA treatment and recurrent cardiovascular events. More prospective studies are needed to determine the independent prognostic importance of RPR during aspirin therapy and possible benefit of individually tailored anti-platelet treatment strategies in these patients. [Copyright &y& Elsevier]

Abstract: Response variability to antiplatelet treatment has been described and the widespread use of acetylsalicylic acid (ASA) and clopidogrel requires clarification of the residual platelet reactivity (RPR). Various glycoprotein Ia (GpIa) polymorphisms have been investigated, but their influence on platelet reactivity in myocardial infarction (MI) patients undergoing percutaneous coronary intervention (PCI) on dual antiplatelet treatment is not still elucidated. Aim of this study was to evaluate the effect of C807T, G873A and T837C polymorphisms of GpIa on modulating platelet function in MI patients on dual antiplatelet treatment undergoing PCI. We measured platelet function by both a point-of-care assay (PFA100) and platelet-rich-plasma aggregation in 289 MI patients undergoing PCI and receiving dual antiplatelet treatment. Our data show that C807T/G873A polymorphisms, but not T837C, are associated with higher platelet reactivity. Carriers of the 807T/873A allele had significantly higher platelet aggregation values after arachidonic acid (AA) and collagen stimuli and, even if they did not reach the statistical significance, after 2 and 10μM ADP stimuli; 807T/873A allele carriers had also significantly shorter closure times on PFA100/epinephrine membranes. At the multiple analyses, C807T/G873A polymorphisms resulted an independent risk factor for RPR defined by both AA induced platelet aggregation (OR=3.0, 95%CI 1.17–7.89, p =0.022) or by PFA100/epinephrine (OR=4.1, 95%CI 1.53–10.89, p =0.005). In conclusion, this study shows the 807T/873A allele of the GpIa gene is an independent risk factor for the RPR on dual antiplatelet treatment, and extends, in a larger acute coronary syndrome population, the observation that the 807T/873A allele is associated with higher platelet reactivity. [Copyright &y& Elsevier]

The aim of this study was to evaluate the effect of polymorphisms affecting the clopidogrel metabolism (CYP3A4 IVS10+12G/A and CYP2C19∗2) and the P2Y12 receptor (P2Y12 T744C) on modulating platelet function in acute coronary syndrome patients on dual antiplatelet treatment.Residual platelet reactivity (RPR) phenomenon on antiplatelet therapy requires clarification. P2Y12 T744C, CYP3A4 IVS10+12G/A and, in healthy individuals only, CYP2C19∗2 polymorphisms have been investigated; however, the influence on platelet reactivity in a large population of high-risk vascular patients on dual antiplatelet treatment has not yet been elucidated.A total of 1419 acute coronary syndrome patients on dual antiplatelet treatment were studied. Platelet function was evaluated by platelet-rich plasma aggregation. Electronic nanochips and restriction-fragment length polymorphism were used for analysis of polymorphisms.Only CYP2C19∗2, out of the three investigated polymorphisms, is associated with higher platelet reactivity. Carriers of the ∗2 allele had significantly higher platelet aggregation values after arachidonic acid (AA; P=0.043), 2 μmol/l adenosine 5′ diphosphate (ADP; P<0.0001) and 10 μmol/l ADP (P=0.001) stimuli. The genotype distribution of CYP2C19∗2 polymorphism significantly differed between patients with and without RPR, as evaluated by 10-μmol/l ADP-induced platelet aggregation (P=0.002) and by AA-induced platelet aggregation (P=0.045). At the multivariate linear regression analysis, the CYP2C19∗2 polymorphism remained a significant and independent risk factor for dual antiplatelet treatment variability.This study demonstrates, for the first time, that the ∗2 CYP2C19 allele is associated with higher platelet aggregability and RPR in high-risk vascular patients on dual antiplatelet treatment. These findings can have a significant impact on the future design of pharmacogenetic antiaggregant strategies for high-risk vascular patients on dual antiplatelet treatment. [ABSTRACT FROM AUTHOR]

Background: Platelet inhibition is important for patients with coronary artery disease. When dual antiplatelet therapy (DAPT) is required, a P2Y12-antagonist is usually recommended in addition to standard aspirin therapy. The most used P2Y12-antagonists are clopidogrel, prasugrel and ticagrelor. Despite DAPT, some patients experience adverse cardiovascular events, and insufficient platelet inhibition has been suggested as a possible cause. In the present review we have performed a literature search on prevalence, mechanisms and clinical implications of resistance to P2Y12 inhibitors. Methods: The PubMed database was searched for relevant papers and 11 meta-analyses were included. P2Y12 resistance is measured by stimulating platelets with ADP ex vivo and the most used assays are vasodilator stimulated phosphoprotein (VASP), Multiplate, VerifyNow (VN) and light transmission aggregometry (LTA). Discussion/conclusion: The frequency of high platelet reactivity (HPR) during clopidogrel therapy is predicted to be 30%. Genetic polymorphisms and drug-drug interactions are discussed to explain a significant part of this inter-individual variation. HPR during prasugrel and ticagrelor treatment is estimated to be 3–15% and 0–3%, respectively. This lower frequency is explained by less complicated and more efficient generation of the active metabolite compared to clopidogrel. Meta-analyses do show a positive effect of adjusting standard clopidogrel treatment based on platelet function testing. Despite this, personalized therapy is not recommended because no large-scale RCT have shown any clinical benefit. For patients on prasugrel and ticagrelor, platelet function testing is not recommended due to low occurrence of HPR. [ABSTRACT FROM AUTHOR]

Background: Residual platelet reactivity is a predictor of poor prognosis in patients with acute coronary syndromes (ACSs) undergoing percutaneous coronary intervention. Thrombin is a major platelet activator and upon initiation of the coagulation cascade, it is subsequently produced downstream of factor IXa, which itself is known to be increased in ACS. Pegnivacogin is a novel RNA-aptamer based factor IXa inhibitor featuring a reversal agent, anivamersen. We hypothesized that pegnivacogin could reduce platelet reactivity., Methods: Whole blood samples from healthy volunteers were incubated in vitro in the presence and absence of pegnivacogin and platelet reactivity was analysed. In addition, platelet aggregometry was performed in blood samples from ACS patients in the RADAR trial featuring the intravenous administration of pegnivacogin as well as reversal by anivamersen., Results: In vitro, pegnivacogin significantly reduced adenosine diphosphate-induced CD62P-expression (100% vs . 89.79±4.04%, p =0.027, n =9) and PAC-1 binding (100% vs . 83.02±4.08%, p =0.010, n =11). Platelet aggregation was reduced (97.71±5.30% vs . 66.53±9.92%, p =0.013, n =10) as evaluated by light transmission aggregometry. In the presence of the RNA-aptamer reversal agent anivamersen, neither CD62P-expression nor platelet aggregation was attenuated. In patients with ACS treated with aspirin and clopidogrel, residual platelet aggregation was significantly reduced 20 min after intravenous bolus of 1 mg/kg pegnivacogin (100% versus 43.21±8.23%, p =0.020)., Conclusion: Inhibition of factor IXa by pegnivacogin decreases platelet activation and aggregation in vitro. This effect was negated by anivamersen. In ACS patients, platelet aggregation was significantly reduced after intravenous pegnivacogin. An aptamer-based anticoagulant inhibiting factor IXa therefore might be a promising antithrombotic strategy in ACS patients.

Objectives: Endovascular procedures are one of the important treatment options for steno-occlusive arteries in ischemic stroke patients. However, embolic complications after such procedures are always a concern. The authors investigated the association between serial change of residual platelet reactivity and silent embolic cerebral infarction (SECI) after endovascular treatment., Methods: Ischemic stroke patients undergoing stenting of intra- or extracranial arteries were recruited prospectively. Residual platelet reactivity, represented by aspirin reaction units (ARUs) and P2Y12 reaction units (PRUs), was measured serially (6 hours before, immediately after, and 24 hours after the procedure). A loading dosage of aspirin (500 mg) and/or clopidogrel (300 mg) was given 24 hours before the procedure to patients naïve to antiplatelet agents, whereas the usual dosage (aspirin 100 mg and clopidogrel 75 mg) was continued for patients who had previously been taking these agents for more than a week. Diffusion-weighted MRI was performed before and 24 hours after the procedure to detect new SECIs. Clinical characteristics, baseline ARU and PRU values, and the change in ARU and PRU values after stenting were compared between patients with and without SECIs., Results: Among 69 consecutive patients who underwent neurovascular stent insertion, 41 patients (59.4%) had poststenting SECIs. The lesion was located only at the vascular territory of the stented vessel in 21 patients (51.2%), outside the stented vessel territory in 8 patients (19.5%), and both inside and outside in 12 patients (29.3%). The occurrence of SECIs was not associated with the baseline ARU or PRU value, but was associated with PRU increase after stenting (36 ± 73 vs -12 ± 59, p = 0.007), deployment of a longer stent (31.1 ± 16.5 mm vs 21.8 ± 9.9 mm, p = 0.01), and stent insertion in extracranial arteries (78.1% vs 45.2%, p = 0.008). Stent length (OR 1.066, p = 0.01) and PRU change (OR 1.009, p = 0.04) were independently associated with the occurrence of SECI., Conclusions: Residual platelet reactivity after dual antiplatelet treatment measured before stenting did not predict poststenting SECI. However, the longer stent and the serial increase of PRU values after stenting were related to SECI. Continuous increase of platelet activation after endovascular procedure may be important in poststent cerebral infarction.

Background: Patients with stable coronary artery disease on single-antiplatelet therapy with aspirin are still at risk for atherothrombotic events, and high on-aspirin residual platelet reactivity (RPR) has been suggested as a risk factor., Methods and Results: In this randomized trial, the association between platelet function determined by the PFA100 platelet function analyzer system (Siemens Healthcare Diagnostics, Germany) and clinical outcome in 1001 patients, all on single-antiplatelet therapy with aspirin (160 mg/d) was studied. Patients were randomized to continue with aspirin 160 mg/d or change to clopidogrel 75 mg/d. A composite end point of death, myocardial infarction, ischemic stroke, and unstable angina was used. At 2-year follow-up, 106 primary end points were registered. The prevalence of high RPR was 25.9%. High on-aspirin RPR did not significantly influence the primary end point in the aspirin group (13.3% versus 9.9%, P=0.31). However, in post hoc analysis, patients with von Willebrand factor levels or platelet count below median values and high on-aspirin RPR had a statistically significant higher end point rate than that of patients with low RPR (20% versus 7.5%, P=0.014, and 18.2% versus 10.8%, P=0.039, respectively). The composite end point rate in patients with high on-aspirin RPR treated with clopidogrel was not different from that of patients treated with aspirin (7.6% versus 13.3%, P=0.16)., Conclusions: In stable, aspirin-treated patients with coronary artery disease, high on-aspirin RPR did not relate to clinical outcome and did not identify a group responsive to clopidogrel. Post hoc subgroup analysis raised the possibility that high on-aspirin RPR might be predictive in patients with low von Willebrand factor or platelet count, but these findings will require confirmation in future studies., Clinical Trial Registration: URL: http://www.clinicaltrials.gov Unique identifier: NCT00222261. (J Am Heart Assoc. 2012;1:e000703 doi: 10.1161/JAHA.112.000703.).