The Role of Platelet Reactivity and Genotype Testing in the Prevention of Atherothrombotic Cardiovascular Events Remains Unproven

Pharmacogenetic information in Swiss drug labels - a systematic analysis

Implementation of pharmacogenetics (PGx) and individualization of drug therapy is supposed to obviate adverse drug reactions or therapy failure. Health care professionals (HCPs) use drug labels (DLs) as reliable information about drugs. We analyzed the Swiss DLs to give an overview on the currently available PGx instructions. We screened 4306 DLs applying natural language processing focusing on drug metabolism (pharmacokinetics) and we assigned PGx levels following the classification system of PharmGKB. From 5979 hits, 2564 were classified as PGx-relevant affecting 167 substances. 55% (n = 93) were classified as "actionable PGx". Frequently, PGx information appeared in the pharmacokinetics section and in DLs of the anatomic group "nervous system". Unstandardized wording, appearance of PGx information in different sections and unclear instructions challenge HCPs to identify and interpret PGx information and translate it into practice. HCPs need harmonization and standardization of PGx information in DLs to personalize drug therapies and tailor pharmaceutical care.

Tailored antiplatelet agent medication in clopidogrel hyporesponsive patients before stent-assisted coiling: single-center experience

PURPOSE

In patients requiring stent procedures, resistance or hyperresponsiveness to antiplatelet medications is often observed. This study aims to evaluate the efficacy and safety of tailoring medications in these patients.

METHODS

This retrospective study included 223 patients who underwent endovascular treatment for intracranial aneurysm between October 2018 and October 2019. Patients were categorized as hyporesponsive, hyperresponsive, and normoresponsive groups according to the initial PRU response. For the hypo- or hyperresponders, we tailored medication by modifying the dose or changing the drug. PRUs before and after tailoring were compared in each group. PRU reponses in patients who underwent Cytochrome P450 2C19 (CYP2C19) genotyping were also determined.

RESULTS

Of the 73 clopidogrel-resistant patients, the mean PRU values after tailoring showed a greater decrease in the group that switched to prasugrel (n = 56), from 223 to 131, than in the clopidogrel reloading group (n = 17), from 238 to 209. In 31 hyperresponders, PRU increased from 49 to 94 after the dose adjustment. CYP2C19 genotyping showed that PRU tended to increase as the number of mutated alleles increased. There were five (2.3%) ischemic events (three transient ischemic attacks and two minor strokes) in a mean follow-up of 8 months, but no hemorrhage.

CONCLUSIONS

The stent-assisted coiling was successfully performed with acceptable range of ischemic events and without hemorrhage in all patients, including those who applied tailored medication. Low-dose prasugrel was effective for obtaining appropriate PRU values for initial medication as well as for clopidogrel-resistant patients. The genetic test did not provide reliable results in determining clopidogrel resistance.

Screening on platelet LncRNA expression profile discloses novel residual platelet reactivity biomarker

INTRODUCTION

Double antiplatelet therapy (DAPT) has wide inter-individual variabilities in coronary heart disease (CHD) patients' responses, which undermines the prognosis effect in clinical practice. Long noncoding RNAs (lncRNAs) have been reported to be widely existed in platelets, albeit their potential roles in platelet responses to DAPT largely remains in the realm of the unknown. This study aims to screen differentially expressed lncRNAs responsible for high residual platelet reactivities under DAPT.

METHODS

We enrolled 144 CHD patients that received DAPT and assigned them to high platelet reactivity (HPR) group and baseline group according to their residual platelet reactivities. Statistical analysis and a series of experiments including microarray analysis, platelet reactivity screening, RNA isolation and lncRNA microarray analysis were explored to the research.

RESULTS

We detected a total of 22,424 kinds of co-expressed lncRNAs in three pairs of patients between the HPR and baseline groups. We identified twenty differentially expressed lncRNAs and successfully validated three of them in the 144 patients. Ultimately, the expression of ensemble transcript ENST00000433442 was demonstrated as significantly correlated with high platelet reactivity (OR = 0.487, P = .035) by logistic regression analysis.

CONCLUSION

There is a considerable amount of lncRNAs in platelets, and the downregulated expression of ENST00000433442 is an independent risk factor for high residual platelet reactivity in CHD patients under DAPT.

Age-dependent association of CYP2C19 polymorphisms with clinical outcome of clopidogrel therapy in minor stroke patients with large-artery atherosclerosis

PURPOSE

Previous studies on the association between CYP2C19 polymorphisms and therapeutic outcome of clopidogrel in stroke patients are inconclusive. We aimed to investigate the impact of CYP2C19 polymorphisms on therapeutic efficacy of clopidogrel in both young and old minor stroke patients associated with large-artery atherosclerosis (LAA).

METHODS

A total of 510 eligible patients were enrolled between April 2015 and April 2018. During 1 year of follow-up, the modified Rankin Scale (mRS) was recorded. Statistical comparisons were performed using Pearson's chi squared test, Mann Whitney U test, and the Breslow-Day test to determine the effects of CYP2C19 polymorphisms on clinical outcome in different age strata. Multivariate binary logistic analysis was used to examine the potential prognostic predictors for clinical outcome. Model fitness was detected with Hosmer-Lemeshow test.

RESULTS

Sixty years old was identified as the optimal cutoff age for CYP2C19 polymorphisms to affect the clinical outcome of clopidogrel therapy in LAA-associated minor stroke patients (OR = 1.67; 95% CI 1.08-2.58). Comparisons of baseline characteristics between patients with favorable and poor outcome indicated the correlation between CYP2C19 loss-of-function (LOF) allele and poorer clinical outcome in ≤ 60-year-old patients (OR = 4.29; 95% CI 1.68-10.93). The heterogeneity test showed a presence of interaction between age and CYP2C19 LOF (OR = 3.75; 95% CI 1.30-10.81). The logistic analyses further suggested that CYP2C19 LOF predicted poor clinical outcome in ≤ 60-year-old but not in > 60-year-old LAA-associated minor stroke patients receiving clopidogrel for the second prevention.

CONCLUSIONS

Carriage of the CYP2C19 LOF allele may prevent expected clinical outcome during clopidogrel therapy in young LAA-associated minor stroke patients, whereas not in older patients.

Clopidogrel Pharmacogenetics

Common genetic variation in CYP2C19 (cytochrome P450, family 2, subfamily C, polypeptide 19) *2 and *3 alleles leads to a loss of functional protein, and carriers of these loss-of-function alleles when treated with clopidogrel have significantly reduced clopidogrel active metabolite levels and high on-treatment platelet reactivity resulting in increased risk of major adverse cardiovascular events, especially after percutaneous coronary intervention. The Food and Drug Administration has issued a black box warning advising practitioners to consider alternative treatment in CYP2C19 poor metabolizers who might receive clopidogrel and to identify such patients by genotyping. However, routine clinical use of genotyping for CYP2C19 loss-of-function alleles in patients undergoing percutaneous coronary intervention is not recommended by clinical guidelines because of lack of prospective evidence. To address this critical gap, TAILOR-PCI (Tailored Antiplatelet Initiation to Lessen Outcomes due to Decreased Clopidogrel Response After Percutaneous Coronary Intervention) is a large, pragmatic, randomized trial comparing point-of-care genotype-guided antiplatelet therapy with routine care to determine whether identifying CYP2C19 loss-of-function allele patients prospectively and prescribing alternative antiplatelet therapy is beneficial.

Clopidogrel Pharmacokinetics in Malaysian Population Groups: The Impact of Inter-Ethnic Variability

Malaysia is a multi-ethnic society whereby the impact of pharmacogenetic differences between ethnic groups may contribute significantly to variability in clinical therapy. One of the leading causes of mortality in Malaysia is cardiovascular disease (CVD), which accounts for up to 26% of all hospital deaths annually. Clopidogrel is used as an adjunct treatment in the secondary prevention of cardiovascular events. CYP2C19 plays an integral part in the metabolism of clopidogrel to the active metabolite clopi-H4. However, CYP2C19 genetic polymorphism, prominent in Malaysians, could influence target clopi-H4 plasma concentrations for clinical efficacy. This study addresses how inter-ethnicity variability within the Malaysian population impacts the attainment of clopi-H4 target plasma concentration under different CYP2C19 polymorphisms through pharmacokinetic (PK) modelling. We illustrated a statistically significant difference (P < 0.001) in the clopi-H4 C_max between the extensive metabolisers (EM) and poor metabolisers (PM) phenotypes with either Malay or Malaysian Chinese population groups. Furthermore, the number of PM individuals with peak clopi-H4 concentrations below the minimum therapeutic level was partially recovered using a high-dose strategy (600 mg loading dose followed by a 150 mg maintenance dose), which resulted in an approximate 50% increase in subjects attaining the minimum clopi-H4 plasma concentration for a therapeutic effect.

Pharmacogenetic association study on clopidogrel response in Puerto Rican Hispanics with cardiovascular disease: a novel characterization of a Caribbean population

Introduction

High on-treatment platelet reactivity (HTPR) to clopidogrel imparts an increased risk for ischemic events in adults with coronary artery disease. Platelet reactivity varies with ethnicity and is influenced by both clinical and genetic variables; however, no clopidogrel pharmacogenetic studies with Puerto Rican patients have been reported. Therefore, we sought to identify clinical and genetic determinants of on-treatment platelet reactivity in a cohort of Puerto Rican patients with cardiovascular disease.

Methods

We performed a retrospective study of 111 patients on 75 mg/day maintenance dose of clopidogrel. Patients were allocated into 2 groups: Group I, without HTPR; and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay and HTPR was defined as P2Y12 reaction units (PRU) ≥230. Genotyping testing was performed using Taqman^® Genotyping Assays.

Results

The mean PRU across the cohort was 203±61 PRU (range 8–324), and 42 (38%) patients had HTPR. Multiple logistic regression showed that 27% of the total variation in PRU was explained by a history of diabetes mellitus, hematocrit, CYP2C19*2, and PON1 p.Q192R. Body mass index (odds ratio [OR]=1.15; 95% CI: 1.03–1.27), diabetes mellitus (OR=3.46; 95% CI: 1.05–11.43), hematocrit (OR=0.75; 95% CI: 0.65–0.87), and CYP2C19*2 (OR=4.44; 95% CI: 1.21–16.20) were the only independent predictors of HTPR.

Conclusion

Moreover, we propose a predictive model to determine PRU values as measured by VerifyNow P2Y12 assay for the Puerto Rican Hispanic population. This model has the potential to identify Hispanic patients at higher risk for adverse events on clopidogrel.

Clinical Relevant Polymorphisms Affecting Clopidogrel Pharmacokinetics and Pharmacodynamics: Insights from the Puerto Rico Newborn Screening Program

Background: Variations in several clopidogrel-pharmacogenes have been linked to clopidogrel response variability and clinical outcomes. We aimed to determine the frequency distribution of major polymorphisms on CYP2C19, PON1, ABCB1 and P2RY12 pharmacogenes in Puerto Ricans. Methods: This was a cross-sectional, population-based study of 200 unrelated "Guthrie" cards specimens from newborns registered in the Puerto Rican newborn screening program (PRNSP) between 2004 and 2014. Taqman® SNP assay techniques were used for genotyping. Results: Minor allele frequencies (MAF) were 46% for PON1 (rs662), 41% for ABCB1 (rs1045642), 14% for CYP2C19*17, 13% for CYP2C19*2, 12% for P2RY12-H2 and 0.3% for CYP2C19*4. No carriers of the CYP2C19*3 variants were detected. All alleles and genotype proportions were found to be in Hardy⁻Weinberg equilibrium (HWE). Overall, there were no significant differences between MAFs of these variants in Puerto Ricans and the general population (n = 453) of the 1000 Genome project, except when comparisons to each individual parental group were performed (i.e., Africans, Europeans and East-Asians; p < 0.05). As expected, the prevalence of these markers in Puerto Ricans most resembled those in the 181 subjects from reference populations of the Americas. Conclusions: These prevalence data provide a necessary groundwork for future clinical studies of clopidogrel pharmacogenetics in Caribbean Hispanics.

Temporal Changes in Platelet Response in Acute Coronary Syndrome Patients With Prasugrel and Clopidogrel After Stent Implantation

BACKGROUND

Prasugrel has been shown to provide more potency and less variability than clopidogrel, but its potential temporal variability has not been described.

METHODS AND RESULTS

We conducted a prospective open-label study, evaluating platelet reactivity overtime in acute coronary syndrome (ACS) patients on aspirin and clopidogrel (n=60) or prasugrel (n=61), after a percutaneous coronary intervention (PCI). Blood samples were taken at discharge and at 3 and 6 months. Platelet function tests included VerifyNow (VN-P2Y12), and Multiplate Aggregometry (MEA). By means of VN-P2Y12, prasugrel patients displayed significantly (P<0.001) higher platelet inhibition than clopidogrel patients over time, although there were not significant differences using MEA. Prasugrel patients showed higher platelet inhibition at baseline than at 3 months (59.3±8.1 vs. 105.0±49.2; P<0.001), without significant change at 6 months (107.9±72.0; P=0.919 vs. 3 months). Clopidogrel patients showed a similar trend (160.1±65.1, 184.8±62.7 and 185.0±53.3; baseline vs. 3 months P=0.060; 3 months vs. 6 months P=0.974). High platelet reactivity (HPR) was shown in 16.3% prasugrel patients, with no patient consistently remaining in HPR over time. HPR was detected in 36.6% of the clopidogrel patients, being consistently observed in 15.0% of them. Low platelet reactivity (LPR) was detected in 60.5% prasugrel and 9.8% clopidogrel patients.

CONCLUSIONS

Prasugrel patients showed less temporal variation than patients on clopidogrel in terms of HPR. In contrast, higher variability in LPR was detected in prasugrel patients for up to 6 months' follow-up.

Analysis of CYP2C19 Genetic Polymorphism in a Large Ethnic Hakka Population in Southern China

Background

Cytochrome P450 (CYP) 2C19 is an enzyme involved in the bioactivation of various important therapeutic drugs, from pro-drugs to an active inhibitor of platelet action. Variants in the CYP2C19 gene influence the pharmacokinetics and clinical response to antiplatelet drugs such as clopidogrel; however, there is no available data about the genetic variation of CYP2C19 in the Hakka population in China.

Material/Methods

A total of 6686 unrelated participants (ages 17–98 years) of self-reported Hakka ancestry admitted at an inpatient department in a hospital in southern China were successfully genotyped by the gene chip platform.

Results

The identified allele frequencies were CYP2C19*1 (64.33%), *2 (31.06%) and *3 (4.61%). The major prevalent genotype combinations were CYP2C19 *1/*1 (41.73%) and *1/*2 (39.65%). The distribution of CYP2C19 phenotypes was divided into extensive metabolizers (EM) (41.73%), intermediate metabolizers (IM) (45.21%), and poor metabolizers (PM) (13.06%). In the Hakka population, frequencies of the CYP2C19 *2 and *3 variants were observed to be close to those previously identified in Chinese and several other Asian populations.

Conclusions

Our study is the first to report on CYP2C19 polymorphisms in the Hakka population, and may help to optimize pharmacotherapy effectiveness by providing personalized medicine to this ethnic group in the near future.

Thrombosis in diabetes: a shear flow effect?

Cardiovascular events are the major cause of morbidity and mortality in Type 2 diabetes (T2D). This condition is associated with heightened platelet reactivity, contributing to increased atherothrombotic risk. Indeed, individuals with diabetes respond inadequately to standard antiplatelet therapy. Furthermore, they often experience recurrent events as well as side effects that include excess bleeding. This highlights the need for identification of novel regulators of diabetes-associated thrombosis to target for therapeutic intervention. It is well established that platelet aggregation, a process essential for thrombus formation, is tightly regulated by shear stress; however, the mechanisms underlying shear activation of platelets, particularly in the setting of diabetes, are still poorly understood. This review will address the limitations of current diagnostic systems to assess the importance of shear stress in the regulation of thrombus formation in T2D, and the inability to recapitulate the pro-thrombotic phenotype seen clinically in the setting of T2D. Moreover, we will discuss recent findings utilizing new technologies to define the importance of shear stress in thrombus formation and their potential application to the setting of diabetes. Finally, we will discuss the potential of targeting shear-dependent mechanisms of thrombus formation as a novel therapeutic approach in the setting of T2D.

Clinical determinants of clopidogrel responsiveness in a heterogeneous cohort of Puerto Rican Hispanics

BACKGROUND

Clopidogrel is by far the most prescribed platelet adenosine diphosphate (ADP) antagonist in Puerto Rico despite the advent of newer agents (prasugrel and ticagrelor). Given the paucity of data on clopidogrel responsiveness in Hispanics, we sought to determine the association between clinical characteristics and platelet reactivity in Puerto Rican patients on clopidogrel therapy.

STUDY POPULATION

A total of 100 Puerto Rican patients on clopidogrel therapy were enrolled and allocated into two groups: Group I, without high on-treatment platelet reactivity (HTPR); and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay.

RESULTS

The cohort was comprised of Hispanic patients with coronary artery disease (57%), peripheral artery disease (32%), carotid artery stenosis (7%), cerebral artery aneurysm (2%), and stroke (2%). Mean platelet reactivity was 200 ± 61 P2Y12 reaction units (PRUs) (range: 8-324), and 35% of patients had HTPR (PRUs ⩾ 230). Multivariable logistic regression analysis determined that diabetes mellitus (DM) [odds ratio (OR) = 3.27; 95% confidence interval (CI): 1.20-8.96], use of proton-pump inhibitors (PPIs) (OR = 3.60; 95% CI: 1.09-11.82), and calcium channel blockers (CCBs) (OR = 3.10; 95% CI: 1.09-8.83) were independent predictors of HTPR ( p < 0.05) after adjusting for other clinical variables.

CONCLUSIONS

In a sample of 100 Puerto Rican Hispanic patients on clopidogrel, 35% had HTPR. Furthermore, DM, PPIs and CCBs predicted HTPR. Clinical outcome data are needed to identify appropriate PRU thresholds for risk prediction in the Puerto Rican population.

In vitro Research Concerning Effect of Clopidogrel Alone and on Combination with Aspirin and Dypiridamoleon Sedimentation of Erythrocytes

Based on extended theory of Derjaguin, Landau and Overbeeck (xDLVO) concerning aggregation of colloids and biological cells it was hypothesized that platelet antiaggregant agents have to reduce the aggregation of erythrocytes also. Applying Einstein-Stokes theory of sedimentation of spheres in viscous media it was concluded that sedimentation of erythrocytes is in fact sedimentation of aggregates of the approximately same size. Consequently, an expected outcome was that addition of antiaggregants in vitro to blood samples from patients with rheumatic or cardiovascular diseases will be the decrease of erythrocytes sedimentation. Starting from usual practice of dual antiaggregant therapy (aspirin and clopidogrel) effects of clopidogrel were compared with effects of clopidogrel plus small concentrations of aspirine and dipyridamole (smaller that their concentrations in plasma after in vivo administration) in order to put in evidence a possible synergic effect at platelet membrane level. Whole blood (0.8ml) was collected on 0.1ml 1% EDTA and then was added 25 or 50µl normal saline solution of clopidogrel or of the combination acetylosalycilic acid, clopidogrel and dypyridamole. The final concentrations were 1, 2 and µg/ml, of the same order as cumulated concentration of clopidogrel and its metabolites in clinical pharmacokinetics. Experiments were performed on a number of 40 human blood samples obtained from 2 groups of 20 patients. Sedimentation of erythrocytes was recorded using a camera and captured data were stored on a computer. Global analysis evidenced that in presence of antiaggregants the clusters of the sedimentation curves shifted down and into right, indicating a decrease and delay of sedimentation. Initial slopes and extent of sedimentation decreased linearly on clopidogrel concentration within the 1-3µg/ml range. For comparison of mean curves corresponding to different clopidogrel concentrations it was applied a metric from biopharmacy: areas under plasma concentrations curves (AUC) of drugs. The areas under average sedimentation curves decreased linearly at clopidogrel concentration within the 1-3µg/ml range. The same experiments were performed and similar results were obtained with the triple antiaggregant combination (clopidogrel, acetylosalycilic acid and dipyridamole). Apparently, a synergism between the tested antiaggregants appeared at studied concentration but the number of data was not sufficient to prove the statistical significance of the difference between clopidogrel alone and in triple combination.

Platelet aggregation and risk of stent thrombosis or bleeding in interventionally treated diabetic patients with acute coronary syndrome

Background

Platelet aggregation monitoring in diabetic patients treated with coronary interventions (PCI) for an acute coronary syndrome (ACS) is a promising way of optimizing treatment and outcomes in this high risk group. The aim of the study was to verify whether clopidogrel response measured by Multiplate analyzer (ADPtest) in diabetic ACS patients treated with PCI predicts the risk of stent thrombosis or cardiovascular mortality and bleeding.

Methods

Into this prospective, observational study 206 elective PCI patients were enrolled. Two cutoff points of ADPtest were used in analysis to divide patients into groups. One (345 AU x min) was calculated based on ROC curve analysis; this cutoff provided the best ROC curve fit, although it did not reach statistical significance. The other (468 AU x min) was accepted based on the consensus of the Working Group on On-Treatment Platelet Reactivity. The risk of stent thrombosis and mortality was assessed using Cox regression analysis and Kaplan-Meier curves.

Results

The risk of stent thrombosis was higher in the group of patients with impaired clopidogrel response for either cutoff value (for >354 AU x min - HR 12.33; 95% CI 2.49–61.1; P = 0.002). Cardiovascular mortality was also higher in the impaired clopidogrel response group (for >354 AU x min - HR 10.58; 95% CI 2.05–54.58; P = 0.005). We did not find a clear relation of increased clopidogrel response to the risk of bleeding.

Conclusions

The results of this study show that in diabetic ACS patient group treated with PCI an impaired platelet response to clopidogrel measured by the Multiplate analyzer results in increased risk of stent thrombosis and cardiac death.

Assessment of platelet function in patients receiving tirofiban early after primary coronary intervention

Background

Following percutaneous coronary intervention, combined antiplatelet therapy is necessary. Platelet function testing (PFT) has prognostic value and may be applied in the risk assessment of acute coronary syndrome. In case of combined antiplatelet therapy, PFT may require special laboratory methods, as different antiplatelet agents may influence test results.

Materials and methods

Platelet functions were measured in stent thrombosis-segment elevation myocardial infarction patients receiving aspirin, clopidogrel, and tirofiban. The first sampling was obtained immediately after the termination of administration of tirofiban. The second sample was drawn at a randomly assigned time between 1 and 6 h. The third sampling was done after a minimum of 24 h of tirofiban cessation. Adenosine diphosphate (ADP)- and thrombin receptor-activating peptide (TRAP)-induced aggregations were measured.

Results

Thirty-seven patients were included. Both TRAP- and ADP-induced aggregation values were significantly lower immediately after tirofiban termination, than after 24 h [TRAP: 26.41 ± 25.00 units (U) vs. 109.86 ± 23.69 U, p < 0.0001; ADP: 17.43 ± 10.10 U vs. 43.92 ± 23.35 U, p ≤ 0.0001]. Elimination half-life of tirofiban and clopidogrel were 1.34 ± 0.49 and 1.269 ± 0.78, respectively.

Conclusion

ADP-induced residual platelet reactivity is significantly influenced by the presence of concurrent glycoprotein IIb/IIIa inhibitor. In patients receiving combined antiplatelet treatment, ADP-receptor-specific efficiency measurements are valid only after total elimination of GPIIb/IIIa inhibitors.

Comparison of the influence of ticagrelor and clopidogrel on inflammatory biomarkers and vascular endothelial function for patients with ST-segment elevation myocardial infarction receiving emergency percutaneous coronary intervention: study protocol for a randomized controlled trial

BACKGROUND

The Platelet Inhibition and Patient Outcomes (PLATO, Eur J Prev Cardiol 22(6):734-42, 2015) trial shows that, in patients who have an acute coronary syndrome, treatment with ticagrelor as compared with clopidogrel significantly reduced the rate of death, but the reason is still uncertain. Both inflammation and vascular endothelian cell dysfunction play important roles in the pathophysiology of atherosclerotic plaques, but whether ticagrelor has superior anti-inflammatory effect and can improve vascular endothelial cell function to a great extent is unknown.

METHODS/DESIGN

Patients with STEMI who are scheduled to undergo emergency percutaneous coronary intervention (PCI) will be randomly assigned to receive a loading dose of ticagrelor 180 mg as the treatment group or clopidogrel 600 mg as the control group. After PCI, the treatment group will be treated with ticagrelor 90 mg twice daily while the control group will be treated with clopidogrel 75 mg once daily. The vascular endothelial function will be tested by circulating endothelial cells, and levels of inflammation will be tested by CD40 ligand (CD40L), high sensitivity C-reactive protein (hsCRP) and P-selectin. The estimated enrollment sample size will be 350 patients, including 175 in the treatment group and 175 in the control group.

DISCUSSION

This study will compare the influence of ticagrelor and clopidogrel on inflammatory biomarkers and vascular endothelial function firstly for STEMI patients receiving emergency PCI and will provide evidence to identify whether ticagrelor inhibits inflammation and improves vascular endothelial cell function to a greater extent than clopidogrel or not.

TRIAL REGISTRATION

This trial was registered with Clinicaltrials.gov (identifier: NCT02123004) on 20 April 2014.

Comparing of light transmittance aggregometry and modified thrombelastograph in predicting clinical outcomes in Chinese patients undergoing coronary stenting with clopidogrel

BACKGROUND

Several platelet function tests are currently used to measure responsiveness to antiplatelet therapy. This study was to compare two tests, light transmittance aggregometry (LTA) and modified thrombelastography (mTEG), for predicting clinical outcomes in Chinese patients after percutaneous coronary intervention (PCI).

METHODS

Prospective, observational, single-center study of 789 Chinese patients undergoing PCI was enrolled. This study was investigated the correlations between the two tests and performed receiver operating characteristic curve (ROC) analysis for major adverse cardiovascular events (MACEs) at 1-year follow-up.

RESULTS

MACEs occurred in 32 patients (4.1%). Correlations were well between the two tests in the adenosine diphosphate induced platelet reactivity (Spearman r = 0.733, P < 0.001). ROC-curve analysis demonstrated that LTA (area under the curve [AUC]: 0.677; 95% confidence interval [CI]: 0.643-0.710; P = 0.0009), and mTEG (AUC: 0.684; 95% CI: 0.650-0.716; P = 0.0001) had moderate ability to discriminate between patients with and without MACE. MACE occurred more frequently in patients with high on-treatment platelet reactivity (HPR) when assessed by LTA (7.4% vs. 2.7%; P < 0.001), and by TEG (6.7% vs. 2.6%; P < 0.001). Kaplan-Meier analysis demonstrated that HPR based on the LTA and mTEG was associated with almost 3-fold increased risk of MACE at 1-year follow-up.

CONCLUSIONS

The correlation between LTA and mTEG is relatively high in Chinese patients. HPR measured by LTA and mTEG were significantly associated with MACE in Chinese patients undergoing PCI.

Antiplatelet strategies for secondary prevention of stroke and TIA

Stroke is a major public health issue, and stroke recurrence accounts for a quarter of all events. Antiplatelet therapy has been extensively studied for secondary stroke prevention and is established as effective in this high-risk population. Several agents have been evaluated in this setting, both in isolation and combination. The most widely used antiplatelet medications are aspirin, clopidogrel, and aspirin plus extended-release dipyridamole. However, new agents and combinations continue to be evaluated. A detailed review of the evidence supporting various antiplatelet regimens for secondary stroke prevention is outlined with special focus on recent developments that may impact clinical management of patients with stroke or TIA.

Antiplatelet and anticoagulation agents in acute coronary syndromes: what is the current status and what does the future hold?

Mortality and morbidity in acute coronary syndromes (ACSs), caused principally by plaque erosion or rupture leading to thrombus formation and myocardial ischemia, have been reduced by a combination of antithrombotic agents (antiplatelet drugs and anticoagulants) and early revascularization. Aspirin is the foundation antiplatelet agent. New P2Y12 receptor inhibitors (prasugrel and ticagrelor) have clear benefits compared with clopidogrel for dual antiplatelet therapy, and cangrelor or vorapaxar, a thrombin receptor inhibitor, may be of value in specific settings. Anticoagulation uses 1 of 4 choices: bivalirudin, unfractionated heparin, enoxaparin, and fondaparinux. Moreover, some patients (such as those who have chronic atrial fibrillation) require triple therapy with aspirin, clopidogrel, plus an anticoagulant, frequently a vitamin K antagonist. New oral anticoagulants have been shown to be at least as effective as vitamin K antagonists in atrial fibrillation and led to fewer bleeding complications. Finally, the combination of aspirin, clopidogrel, and low-dose rivaroxaban has recently been approved by the European Medicines Agency (but not the Food and Drug Administration) for secondary prevention after ACS. Several strategies have been developed to balance the potential benefit of antithrombotic therapy against the risk of bleeding complications, for example, radial access in coronary angiography or restricted use of combination therapy, and others are under investigation, such as discontinuation of aspirin. This overview summarizes the current status of antithrombotic therapy in ACS and describes strategies currently explored to optimize its benefit/risk ratio.

World heart federation expert consensus statement on antiplatelet therapy in east asian patients with ACS or undergoing PCI

Guideline recommendations on the use of dual antiplatelet therapy (DAPT) in patients with acute coronary syndromes and in those undergoing percutaneous coronary intervention (PCI) have been formulated by both the ACC/AHA and the ESC. These recommendations are based primarily on large, phase III, randomized, controlled trials of the P2Y12 inhibitors clopidogrel, prasugrel, and ticagrelor. However, few East Asian patients have been included in the trials to assess the use of these agents, particularly the newer agents prasugrel and ticagrelor. Additionally, an increasing body of data suggests that East Asian patients have differing risk profiles for both thrombophilia and bleeding compared with white patients, and that a different 'therapeutic window' of on-treatment platelet reactivity might be appropriate in East Asian patients. Furthermore, a phenomenon referred to as the 'East Asian paradox' has been described, in which East Asian patients have a similar or even a lower rate of ischaemic events after PCI compared with white patients, despite a higher level of platelet reactivity during DAPT. Recognizing these concerns, the World Heart Federation has undertaken this evidence-based review and produced this expert consensus statement to determine the antiplatelet treatment strategies that are most appropriate for East Asian patients.

Expert consensus document: World Heart Federation expert consensus statement on antiplatelet therapy in East Asian patients with ACS or undergoing PCI

Guideline recommendations on the use of dual antiplatelet therapy (DAPT) in patients with acute coronary syndromes and in those undergoing percutaneous coronary intervention (PCI) have been formulated by both the ACC/AHA and the ESC. These recommendations are based primarily on large, phase III, randomized, controlled trials of the P2Y12 inhibitors clopidogrel, prasugrel, and ticagrelor. However, few East Asian patients have been included in the trials to assess the use of these agents, particularly the newer agents prasugrel and ticagrelor. Additionally, an increasing body of data suggests that East Asian patients have differing risk profiles for both thrombophilia and bleeding compared with white patients, and that a different 'therapeutic window' of on-treatment platelet reactivity might be appropriate in East Asian patients. Furthermore, a phenomenon referred to as the 'East Asian paradox' has been described, in which East Asian patients have a similar or even a lower rate of ischaemic events after PCI compared with white patients, despite a higher level of platelet reactivity during DAPT. Recognizing these concerns, the World Heart Federation has undertaken this evidence-based review and produced this expert consensus statement to determine the antiplatelet treatment strategies that are most appropriate for East Asian patients.

Role of phenotypic and genetic testing in managing clopidogrel therapy

The P2Y12 inhibitors, clopidogrel, prasugrel, and ticagrelor, are administered in fixed doses without laboratory monitoring. Randomized trials in acute coronary syndrome have shown that prasugrel and ticagrelor are more effective than standard-dose clopidogrel. Nonetheless, standard-dose clopidogrel remains widely used because it causes less bleeding and is less expensive. Patients treated with standard-dose clopidogrel have substantial variability in platelet inhibition, which is partly explained by genetic polymorphisms encoding CYP2C19, the hepatic enzyme involved in biotransformation of clopidogrel to its active metabolite. Some advocate tailoring P2Y12 inhibitor therapy according to the results of routine laboratory testing. Although there is good evidence for analytic, biological, and clinical validity of several phenotypic and genotypic biomarkers, the benefit of a management strategy that incorporates routine biomarker testing over standard of care without such testing remains unproven. Appropriately designed, adequately powered trials are needed but face the challenges of feasibility, cost, and the progressive switch from clopidogrel to prasugrel or ticagrelor.

Significance of antiplatelet therapy in emergency myocardial infarction treatment

Antiplatelet drugs play a crucial role in the treatment of patients with myocardial infarction, particularly in association with percutaneous coronary intervention. Their main advantage is the reduction of adverse ischemic incidents and the major disadvantage is the increase in the frequency of hemorrhages. Thus, the choice of appropriate drug depends on the right risk assessment of the development of these complications in individual patients. The aim of this article is to provide an update of antiplatelet therapy in emergency myocardial infarction treatment. Currently, the most important role in the process of platelet inhibition is played by ADP P2Y12 blockers: clopidogrel, prasugrel and ticagrelor. Clopidogrel and prasugrel belong to thienopyridines, and ticagrelor, a drug of irreversible action, is an analogue of adenosine triphosphate. By 2011 clopidogrel, alongside aspirin, had the highest recommendations of world cardiology associations for acute coronary syndrome treatment. The position on clopidogrel was changed following the publication of European Society of Cardiology guidelines for STEMI in 2012 which advocate the administration of acetylsalicylic acid (ASA) and ADP receptor blocker (in combination with ASA). It needs to be stressed that prasugrel and ticagrelor received class IB recommendation, while clopidogrel received only IC. However, the most recent studies aimed at introducing a new generation of antiplatelet drugs of high efficacy in prevention of ischemic incidents and of reversible action: cangrelor and elinogrel, which raise hopes for better prognosis for myocardial infarction patients.

Testing platelet function

Platelet function tests have been traditionally used to aid in the diagnosis and management of patients with bleeding problems. Given the role of platelets in atherothrombosis, several dedicated platelet function instruments are now available that are simple to use and can be used as point-of-care assays. These can provide rapid assessment of platelet function within whole blood without the requirement of sample processing. Some tests can be used to monitor antiplatelet therapy and assess risk of bleeding and thrombosis, although current guidelines advise against this. This article discusses the potential utility of tests/instruments that are available.

Questions and answers on proper peri-operative management of antiplatelet therapy after coronary stent implantation to prevent stent thrombosis

Stent thrombosis (ST) is a rare but life-threatening complication of coronary artery stenting. Although dual-antiplatelet therapy is an effective management strategy in reducing the risk for ST, some patients may need to interrupt their regimens because of unforeseen circumstances, such as the requirement for surgery. In conclusion, this case presentation highlights some pertinent issues related to ST, including its risk factors, the perioperative management of antiplatelet agents, and treatment for ST.

Consensus and update on the definition of on-treatment platelet reactivity to adenosine diphosphate associated with ischemia and bleeding

Dual antiplatelet therapy with aspirin and a P2Y12 receptor blocker is a key strategy to reduce platelet reactivity and to prevent thrombotic events in patients treated with percutaneous coronary intervention. In an earlier consensus document, we proposed cutoff values for high on-treatment platelet reactivity to adenosine diphosphate (ADP) associated with post-percutaneous coronary intervention ischemic events for various platelet function tests (PFTs). Updated American and European practice guidelines have issued a Class IIb recommendation for PFT to facilitate the choice of P2Y12 receptor inhibitor in selected high-risk patients treated with percutaneous coronary intervention, although routine testing is not recommended (Class III). Accumulated data from large studies underscore the importance of high on-treatment platelet reactivity to ADP as a prognostic risk factor. Recent prospective randomized trials of PFT did not demonstrate clinical benefit, thus questioning whether treatment modification based on the results of current PFT platforms can actually influence outcomes. However, there are major limitations associated with these randomized trials. In addition, recent data suggest that low on-treatment platelet reactivity to ADP is associated with a higher risk of bleeding. Therefore, a therapeutic window concept has been proposed for P2Y12 inhibitor therapy. In this updated consensus document, we review the available evidence addressing the relation of platelet reactivity to thrombotic and bleeding events. In addition, we propose cutoff values for high and low on-treatment platelet reactivity to ADP that might be used in future investigations of personalized antiplatelet therapy.

Influence of platelet reactivity and inflammation on peri-procedural myonecrosis in East Asian patients undergoing elective percutaneous coronary intervention

BACKGROUND AND OBJECTIVES

The contribution of multiple risk factors to peri-procedural myocardial infarction (PMI) in East Asians remains controversial. To assess the influence of clinical or laboratory covariates on PMI in these patients.

METHODS

Stable patients (n=341) undergoing elective percutaneous coronary intervention (PCI) were enrolled. Platelet reactivity was measured by conventional aggregometry and VerifyNow. Inflammation markers and lipid profile were determined by standard methods. PMI was defined according to Universal definition (troponin I or CK-MB ≥ 3 times the 99th percentile of the upper reference limit).

RESULTS

PMI (defined by troponin I and CK-MB) occurred in 47 (13.8%) and 30 (8.8%) patients, respectively. There was no significant difference in ADP-induced platelet reactivity between patients with vs. without PMI. Patients with PMI (troponin I) had higher levels of 6 μg/mL collagen-induced platelet aggregation (PA) and VerifyNow 'BASE' compared with those without PMI. The combination of '6 μg/mL collagen-induced PA>40%'+'BASE>318' (odds ratio, 14.08; 95% confidence intervals, 1.68 to 111.11; p=0.015) or 'WBC>6550/mm(3)'+'C-reactive protein>2.3mg/L' (odds ratio, 7.75; 95% confidence intervals, 2.49 to 24.39; p<0.001) was associated with an increased risk of PMI (troponin I). The greatest likelihood ratio was observed when cholesterol, inflammation marker and platelet function were combined together.

CONCLUSION

This is the first study to demonstrate that heightened platelet responsiveness to collagen and thrombin may be a risk factor for myonecrosis in patients undergoing elective PCI. The utility of the combining measures of platelet function, inflammation and cholesterol to enhance risk stratification and thus facilitate personalized therapy deserves further study.

[Personalized therapy in cardiology. Biomarkers, pharmacogenetics and therapy of monogenic diseases]

Improved therapy and prophylaxis of cardiovascular diseases have contributed to an increase in life expectancy like no other field of medicine. However, many cardiological diseases remain untreatable and standard therapies often work only in a minority of patients or cause more harm than benefit. Personalized approaches appear to be a promising solution. Monogenic heart diseases are paradigmatic for this approach and can in rare cases be treated mutation specifically. Overall, however, success remains limited. Next generation sequencing will facilitate the identification of mutations causing diseases. Cell culture models based on induced pluripotent stem cells open the perspective of individualized testing of disease severity and pharmacological or genetic therapy. In contrast to monogenic diseases genetic testing plays no practical role yet in the management of multifactorial cardiovascular diseases. Biomarkers can identify individuals with increased cardiovascular risk. Furthermore, biomarker-guided therapy represents an attractive option with troponin-guided therapy of acute coronary syndromes as a successful example. Individual responses to drugs vary and are partly determined by genes. Simple genetic analyses can improve response prediction and minimize side effects in cases such as warfarin and high doses of simvastatin. Taken together personalized approaches will gain importance in the cardiovascular field but this requires the development of better methods and research that quantifies the true value of the new knowledge.

Relation between the vasodilator-stimulated phosphoprotein phosphorylation assay and light transmittance aggregometry in East Asian patients after high-dose clopidogrel loading

OBJECTIVES

We analyzed the relation between platelet aggregation measured by light transmittance aggregometry (LTA) and platelet reactivity index (PRI) measured by vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) assay.

BACKGROUND

It has been suggested that LTA and VASP-P assay correlate differently according to the level of P2Y12 receptor blockade by thienopyridines.

METHODS

We simultaneously measured platelet function by LTA and VASP-P assay in 466 East Asians undergoing elective percutaneous coronary intervention after a 600-mg clopidogrel loading. High on-clopidogrel platelet reactivity (HPR) was defined by published consensus criteria.

RESULTS

The degree of correlation between LTA and the VASP-P assay was different according to PRI levels. The correlation was lower in patients with poor responsiveness (PRI >60%) (n = 216) (0.035 ≤ r(2) ≤ 0.047), which was greater in responsive patients (PRI ≤60%) (n = 250) (0.315 ≤ r(2) ≤ 0.526). Despite a 600-mg loading, East Asians had a high prevalence of HPR (40.1%-63.5%), and the prevalence of HPR also differed between LTA and VASP-P assay. A PRI cutoff of >58% (area under curve, 0.829; 95% confidence intervals, 0.792-0.862; P < .001) corresponded to the published HPR cutoff by 5-μM adenosine diphosphate-induced maximal platelet aggregation >46%.

CONCLUSIONS

This is the largest study correlating platelet reactivity measured by LTA and VASP-P assay in a percutaneous coronary intervention-treated cohort. The correlation is dependent on the level of responsiveness. Future investigations are needed to better define the optimal cutoffs of HPR measured by LTA and VASP-P assay for personalized antiplatelet therapy.

CYP2C19 genotypes and their impact on clopidogrel responsiveness in percutaneous coronary intervention

BACKGROUND

Cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms are more common in Asian populations and have been associated with diminished antiplatelet response to clopidogrel. In this era of 'personalised medicine', combining genotyping and phenotyping as a strategy to personalise antiplatelet therapy warrants further exploration.

OBJECTIVE

This study aimed to investigate the prevalence and impact of CYP2C19*2, *3 and *17 genotypes on clopidogrel responsiveness in a multiethnic Malaysian population planned for percutaneous coronary intervention.

SETTING

Between October 2010 and March 2011, a total of 118 consecutive patients planned for percutaneous coronary intervention were enrolled in Sarawak General Hospital, Borneo. All patients received at least 75 mg aspirin daily for at least 2 days and 75 mg clopidogrel daily for at least 4 days prior to angiography.

METHOD

Genotyping for CYP2C19*2 (rs4244285, 681G > A), *3 (rs4986893, 636G > A) and *17 (rs11188072, -3402C > T) alleles were performed by polymerase chain reaction-restriction fragment linked polymorphism method. Whole blood ADP-induced platelet aggregation was assessed with multiple electrode platelet aggregometry (MEA) using the Multiplate Analyzer.

MAIN OUTCOME MEASURES

The distribution of CYP2C19*2, *3 and *17 among different ethnic groups and the association between genotype, clopidogrel responsiveness and clinical outcome were the main outcome measures.

RESULTS

The highest prevalence of poor metabolisers (carriers of at least one copy of the *2 or *3 allele) was among the Chinese (53.7 %), followed by the Malays (26.9 %), Ibans (16.4 %) and other races (3.0 %). Poor metabolisers (PMs) had the highest mean MEA (303.6 AU*min), followed by normal metabolisers (NMs) with 270.5 AU*min and extensive metabolisers (EMs) with 264.1 AU*min (p = 0.518). Among poor responders to clopidogrel, 65.2 % were PMs and NMs, respectively, whereas none were EMs (p = 0.350). Two cardiac-related deaths were reported.

CONCLUSION

There was a diverse inter-ethnic difference in the distribution of CYP2C19 polymorphism. The findings of this study echo that of other studies where genotype appears to have a limited impact on clopidogrel responsiveness and clinical outcome in low-risk patients.

Triple, simultaneous, very late coronary stent thrombosis

Coronary artery stent thrombosis is an uncommon but potentially catastrophic complication. The risk of very late stent thrombosis (VLST) raises important safety issues regarding the first generation of drug-eluting stents (DES). Although several complex mechanisms for VLST have been suggested and various predictors have been described, its pathophysiology is not completely understood and it is not known whether longer-term dual antiplatelet therapy reduces the risk. We present a rare case of simultaneous very late DES thrombosis in the three vascular territories, following discontinuation of antiplatelet therapy seven years after stent placement, presenting as cardiogenic shock.

Platelet activation and inhibition in polycythemia vera and essential thrombocythemia

Persistently enhanced platelet activation has been characterized in polycythemia vera (PV) and essential thrombocythemia (ET) and shown to contribute to a higher risk of both arterial and venous thrombotic complications. The incidence of major bleeding complications is also somewhat higher in PV and ET than in the general population. Although its efficacy and safety was assessed in just 1 relatively small trial in PV, low-dose aspirin is currently recommended in practically all PV and ET patients. Although for most patients with a thrombosis history the benefit/risk profile of antiplatelet therapy is likely to be favorable, in those with no such history this balance will depend critically on the level of thrombotic and hemorrhagic risks of the individual patient. Recent evidence for a chemopreventive effect of low-dose aspirin may tilt the balance of benefits and harm in favor of using aspirin more broadly, but the potential for additional benefits needs regulatory scrutiny and novel treatment guidelines. A clear pharmacodynamic rationale and analytical tools are available for a personalized approach to antiplatelet therapy in ET, and an improved regimen of low-dose aspirin therapy should be tested in a properly sized randomized trial.

Evaluating the clinical usefulness of platelet function testing: considerations for the proper application and interpretation of performance measures

Various diagnostic and prognostic performance measures have been used to describe the clinical usefulness of platelet function testing in the evaluation and management of patients taking P2Y12 inhibitors, which reduce the risk for thrombosis due to their action on the platelet P2Y12 receptor. Platelet function tests are used to confirm the presence of an antiplatelet effect of a P2Y12 inhibitor, and confirmation that the pharmacodynamic effect is associated with a reduction in the rate of thrombosis. Despite this clear association, enthusiasm for the clinical usefulness of platelet function testing has been tempered based on observed sensitivity, specificity, and positive predictive value for the detection of future thrombotic events. However, evaluating the prognostic utility of a test based on diagnostic performance indicators is not appropriate because prognostic tests are not used to diagnose which patients will have events; instead, they are used to assist in risk stratification. Therefore, when evaluating the usefulness of platelet function testing, diagnostic performance measures such as sensitivity, specificity, and predictive values should focus on diagnostic performance in identifying a pharmacodynamic effect, and prognostic performance should be evaluated using prognostic performance measures such as hazard ratios and net reclassification improvement, which are comparable to other well-established risk factors for cardiovascular events.