Comparison of four tests to assess inhibition of platelet function by clopidogrel in stable coronary artery disease patients

Factors that modulate platelet reactivity as measured by 5 assay platforms in 3429 individuals

Background

Assessment of platelet function is key in diagnosing bleeding disorders and evaluating antiplatelet drug efficacy. However, there is a prevailing "one-size-fits-all" approach in the interpretation of measures of platelet reactivity, with arbitrary cutoffs often derived from healthy volunteer responses.

Objectives

Our aim was to compare well-used platelet reactivity assays.

Methods

Blood and platelet-rich plasma obtained from the Framingham Heart Study (N = 3429) were assayed using a range of agonists in 5 platelet assays: light transmission aggregometry, Optimul aggregometry, Multiplate impedance aggregometry (Roche Diagnostics), Total Thrombus-Formation Analysis System, and flow cytometry. Using linear mixed-effect models, we determined the contribution of preanalytical and technical factors that modulated platelet reactivity traits.

Results

A strong intra-assay correlation of platelet traits was seen in all assays, particularly Multiplate velocity (r = 0.740; ristocetin vs arachidonic acid). In contrast, only moderate interassay correlations were observed (r = 0.375; adenosine diphosphate Optimul Emax vs light transmission aggregometry large area under the curve). As expected, antiplatelet drugs strongly reduced platelet responses, with aspirin use primarily targeting arachidonic acid-induced aggregation, and explained substantial variance (β = -1.735; P = 4.59 × 10-780; variance proportion = 46.2%) and P2Y12 antagonists blocking adenosine diphosphate responses (β = -1.612; P = 6.75 × 10-27; variance proportion = 2.1%). Notably, female sex and older age were associated with enhanced platelet reactivity. Fasting status and deviations from standard venipuncture practices did not alter platelet reactivity significantly. Finally, the agonist batch, phlebotomist, and assay technician (more so for assays that require additional sample manipulation) had a moderate to large effect on measured platelet reactivity.

Conclusion

Caution must be exercised when extrapolating findings between assays, and the use of standard ranges must be medication-specific and sex-specific at a minimum. Researchers should also consider preanalytical and technical variables when designing experiments and interpreting platelet reactivity measures.

High-on-treatment platelet reactivity predicts adverse outcome after carotid artery stenting: A prospective study

BACKGROUND AND PURPOSE

High-on-treatment platelet reactivity (HTPR) has been established as a predictor of major adverse cardiovascular events (MACE) in patients undergoing percutaneous coronary interventions on dual antiplatelet therapy (DAPT), but no data are available on its predictive value in patients on DAPT after carotid artery stenting (CAS). We aimed to evaluate the possible association between HTPR in patients on aspirin plus clopidogrel therapy after CAS and subsequent MACE.

METHODS

All consecutive patients treated with CAS in a single institution were enrolled in a prospective clinical study. HTPR was evaluated with 5 different laboratory assays carried out just before CAS. MACE incidence (cerebral ischemia, myocardial infarction, stent thrombosis, acute limb ischemia and vascular death) was evaluated at 30 days and thereafter at yearly visits.

RESULTS

A total of 300 patients were enrolled in the study, and eight were then excluded because blood samples resulted unsuitable for the laboratory testing or CAS aborted for technical problems. Median follow-up was 5.8 years and during this period 47 MACE occurred. HTPR detected by multiplate electronic aggregometry (MEA) and the VASP phosphorylation assay (VASP) were associated with a significantly enhanced risk of MACE (p = 0.048 and p = 0.038, respectively). However, HTPR to three tests (HTPR3) was more strongly predictive of increased risk of a vascular event at follow up (p = 0.005) at bivariate analysis and also at Cox regression multivariate analysis (p = 0.002).

CONCLUSIONS

HTPR to three different assays (mainly to VASP + PFA P2Y+ VerifyNow) in patients on DAPT after CAS has predictive value for subsequent MACE. Prospective studies to assess whether platelet function testing-guided antiplatelet therapy is superior to standard DAPT in patient undergoing CAS should be considered.

Extracellular Vesicles in Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of death and disability worldwide. Despite recent progress in the diagnosis and treatment of CAD, evidence gaps remain, including pathogenesis, the most efficient diagnostic strategy, prognosis of individual patients, monitoring of therapy, and novel therapeutic strategies. These gaps could all be filled by developing novel, minimally invasive, blood-based biomarkers. Potentially, extracellular vesicles (EVs) could fill such gaps. EVs are lipid membrane particles released from cells into blood and other body fluids. Because the concentration, composition, and functions of EVs change during disease, and because all cell types involved in the development and progression of CAD release EVs, currently available guidelines potentially enable reliable and reproducible measurements of EVs in clinical trials, offering a wide range of opportunities. In this chapter, we provide an overview of the associations reported between EVs and CAD, including (1) the role of EVs in CAD pathogenesis, (2) EVs as biomarkers to diagnose CAD, predict prognosis, and monitor therapy in individual patients, and (3) EVs as new therapeutic targets and/or drug delivery vehicles. In addition, we summarize the challenges encountered in EV isolation and detection, and the lack of standardization, which has hampered real clinical applications of EVs. Since most conclusions are based on animal models and single-center studies, the knowledge and insights into the roles and opportunities of EVs as biomarkers in CAD are still changing, and therefore, the content of this chapter should be seen as a snapshot in time rather than a final and complete compendium of knowledge on EVs in CAD.

A Sticky Situation: Variable Agreement Between Platelet Function Tests Used to Assess Anti-platelet Therapy Response

Background

Platelet function testing to monitor antiplatelet therapy is important for reducing thromboembolic complications, yet variability across testing methods remains challenging. Here we evaluated the agreement of four different testing platforms used to monitor antiplatelet effects of aspirin (ASA) or P2Y₁₂ inhibitors (P2Y12-I).

Methods

Blood and urine specimens from 20 patients receiving dual antiplatelet therapy were analyzed by light transmission aggregometry (LTA), whole blood aggregometry (WBA), VerifyNow PRUTest and AspirinWorks. Result interpretation based on pre-defined cutoff values was used to calculate raw agreement indices, and Pearson's correlation coefficient determined using individual units of measure.

Results

Agreement between LTA and WBA for P2Y12-I-response was 60% (r = 0.65, high-dose ADP; r = 0.75, low-dose ADP). VerifyNow agreed with LTA in 75% (r = 0.86, high-dose ADP; r = 0.75, low-dose ADP) and WBA in 55% (r = 0.57) of cases. Agreement between LTA and WBA for ASA-response was 45% (r = 0.09, high-dose collagen WBA; r = 0.19, low-dose collagen WBA). AspirinWorks agreed with LTA in 60% (r = 0.32) and WBA in 35% (r = 0.02, high-dose collagen WBA; r = 0.08, low-dose collagen WBA) of cases.

Conclusions

Overall agreement varied from 35 to 75%. LTA and VerifyNow demonstrated the highest agreement for P2Y12-I-response, followed by moderate agreement between LTA and WBA. LTA and AspirinWorks showed moderate agreement for aspirin response, while WBA showed the weakest agreement with both LTA and AspirinWorks. The results from this study support the continued use of LTA for monitoring dual antiplatelet therapy, with VerifyNow as an appropriate alternative for P2Y12-I-response. Integration of results obtained from these varied testing platforms with patient outcomes remains paramount for future studies.

P2Y12 Antagonists in Cardiovascular Disease—Finding the Best Balance Between Preventing Ischemic Events and Causing Bleeding

Dual antiplatelet therapy comprising of aspirin and oral P2Y₁₂ receptor antagonists are an established cornerstone of therapy in acute coronary syndromes and percutaneous coronary intervention. As a result, the platelet P2Y₁₂ receptor remains a key therapeutic target in cardiovascular medicine since pharmacological antagonists were first developed in the 1990’s. With a greater understanding of platelet biology and the role played by the P2Y₁₂ receptor in the amplification of platelet activation and thrombus formation, there has been progressive refinement in the development of P2Y₁₂ receptor antagonists with greater potency and consistency of antiplatelet effect. However, challenges remain in the utilization of these agents particularly in balancing the need for greater protection from ischemic events whilst minimizing the bleeding risk and present a real opportunity for the institution of individualized medicine. Future drug developments will provide clinicians with greater avenues to achieve this.

Antiplatelet Therapy for Atherothrombotic Disease in 2022—From Population to Patient-Centered Approaches

Antiplatelet agents, with aspirin and P2Y₁₂ receptor antagonists as major key molecules, are currently the cornerstone of pharmacological treatment of atherothrombotic events including a variety of cardio- and cerebro-vascular as well as peripheral artery diseases. Over the last decades, significant changes have been made to antiplatelet therapeutic and prophylactic strategies. The shift from a population-based approach to patient-centered precision medicine requires greater awareness of individual risks and benefits associated with the different antiplatelet strategies, so that the right patient gets the right therapy at the right time. In this review, we present the currently available antiplatelet agents, outline different management strategies, particularly in case of bleeding or in perioperative setting, and develop the concept of high on-treatment platelet reactivity and the steps toward person-centered precision medicine aiming to optimize patient care.

Assessment of Platelet Reactivity and Inflammatory Markers in Coronary Artery Bypass Graft Patients Treated with Acetylsalicylic Acid with Flavonoid Supplementation

The recommended pharmacological therapy for patients with coronary artery disease (CAD) treated by coronary artery bypass grafting (CABG) is acetylsalicylic acid (ASA). To improve the antiplatelet effect, supplementation with flavonoids is also recommended. The aim of this study was to estimate anti-aggregation properties of diosmin, in combination with ASA, pre- and postoperatively and assess the relationship of this therapy with inflammatory processes in CAD patients undergoing CABG. The study patients (n = 26) took diosmin (1000 mg/day); the control patients (n = 27) took a placebo. The therapeutic period for taking diosmin was from at least 30 days before to 30 days after CABG. All patients also took 75 mg/day ASA. Platelet aggregation and IL-6, CRP, and fibrinogen concentrations were determined before and 30 days after surgery. Results showed that diosmin did not enhance the anti-aggregation effect of ASA at any assessment time. However, there was a stronger anti-aggregation effect 30 days after surgery that was diosmin independent and was associated with acute-phase markers in the postoperative period. Increased levels of inflammatory markers in the late phase of the postoperative period may provide an unfavorable prognostic factor in long-term follow-up, which should prompt the use of stronger antiplatelet therapy in patients after CABG.

Effects of lignocaine vs. opioids on antiplatelet activity of ticagrelor: the LOCAL trial

AIMS

We assessed the impact of intravenous fentanyl and lignocaine on the pharmacokinetics and pharmacodynamics of ticagrelor in patients with unstable angina and non-ST-elevation myocardial infarction and their procedural analgesic efficacy and safety.

METHODS AND RESULTS

Seventy patients undergoing coronary angiography with ticagrelor loading were included in the pharmacokinetic and pharmacodynamic analyses of this randomized trial. Plasma ticagrelor levels 2 h post-loading dose were significantly lower in the fentanyl arm than in the lignocaine treatment arm (598 vs. 1008 ng/mL, P = 0.014). The area under the plasma-time curves for ticagrelor (1228 vs. 2753 ng h/mL, P < 0.001) and its active metabolite (201 vs. 447 ng h/mL, P = 0.001) were both significantly lower in the fentanyl arm. Expression of activated platelet glycoprotein IIb/IIIa receptor (2829 vs. 1426 mean fluorescence intensity, P = 0.006) and P-selectin (439 vs. 211 mean fluorescence intensity, P = 0.001) was significantly higher at 60 min in the fentanyl arm. A higher proportion of patients had high on-treatment platelet reactivity in the fentanyl arm at 60 min using the Multiplate Analyzer (41% vs. 9%, P = 0.002) and 120 min using the VerifyNow (30% vs. 3%, P = 0.003) and VASP (37% vs. 6%, P = 0.002) assays. Both drugs were well tolerated with a high level of patient satisfaction.

CONCLUSIONS

Unlike fentanyl, lignocaine does not impair the bioavailability or delay the antiplatelet effect of ticagrelor. Both drugs were well tolerated and effective with a high level of patient satisfaction for procedural analgesia. Routine procedural analgesia during percutaneous coronary intervention should be reconsidered and if performed, lignocaine is a beneficial alternative to fentanyl.

Differential Impact of Cytochrome 2C19 Allelic Variants on Three Different Platelet Function Tests in Clopidogrel-Treated Patients

On-treatment platelet reactivity in clopidogrel-treated patients can be measured with several platelet function tests (PFTs). However, the agreement between different PFTs is only slight to moderate. Polymorphisms of the CYP2C19 gene have an impact on the metabolization of clopidogrel and, thereby, have an impact on on-treatment platelet reactivity. The aim of the current study is to evaluate the differential effects of the CYP2C19 genotype on three different PFTs. Methods: From a prospective cohort study, we included patients treated with clopidogrel following percutaneous coronary intervention (PCI). One month after PCI, we simultaneously performed three different PFTs; light transmission aggregometry (LTA), VerifyNow P2Y12, and Multiplate. In whole EDTA blood, genotyping of the CYP2C19 polymorphisms was performed. Results: We included 308 patients treated with clopidogrel in combination with aspirin (69.5%) and/or anticoagulants (33.8%) and, based on CYP2C19 genotyping, classified them as either extensive (36.4%), rapid (34.7%), intermediate (26.0%), or poor metabolizers (2.9%). On-treatment platelet reactivity as measured by LTA and VerifyNow is significantly affected by CYP2C19 metabolizer status (p < 0.01); as metabolizer status changes from rapid, via extensive and intermediate, to poor, the mean platelet reactivity increases accordingly (p < 0.01). On the contrary, for Multiplate, no such ordering of metabolizer groups was found (p = 0.10). Conclusions: For VerifyNow and LTA, the on-treatment platelet reactivity in clopidogrel-treated patients correlates well with the underlying CYP2C19 polymorphism. For Multiplate, no major effect of genetic background could be shown, and effects of other (patient-related) variables prevail. Thus, besides differences in test principles and the influence of patient-related factors, the disagreement between PFTs is partly explained by differential effects of the CYP2C19 genotype.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Decreased Platelet Inhibition by Thienopyridines in Hyperuricemia

PURPOSE

Hyperuricemia carries an increased risk of atherothrombotic events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). This may at least in part be due to inadequate P2Y12 inhibition. The aim of this study was to prospectively investigate the potential association between hyperuricemia and decreased platelet inhibition by P2Y12 antagonists.

METHODS

Levels of uric acid as well as on-treatment residual platelet reactivity in response to adenosine diphosphate (ADP) were assessed in 301 clopidogrel-treated patients undergoing elective angioplasty and stenting, and in 206 prasugrel- (n = 118) or ticagrelor-treated (n = 88) ACS patients following acute PCI. Cut-off values for high on-treatment residual ADP-inducible platelet reactivity (HRPR) were based on previous studies showing an association of test results with clinical outcomes.

RESULTS

Hyperuricemia was significantly associated with increased on-treatment residual ADP-inducible platelet reactivity in clopidogrel- and prasugrel-treated patients in univariate analyses and after adjustment for differences in patient characteristics by multivariate regression analyses. In contrast, ticagrelor-treated patients without and with hyperuricemia showed similar levels of on-treatment residual platelet reactivity to ADP. HRPR occurred more frequently in clopidogrel- and prasugrel-treated patients with hyperuricemia than in those with normal uric acid levels. In contrast, hyperuricemic patients receiving ticagrelor did not have a higher risk of HRPR compared with those with normal uric acid levels.

CONCLUSION

Hyperuricemia is associated with decreased platelet inhibition by thienopyridines but a normal response to ticagrelor. It remains to be established if lowering uric acid increases the antiplatelet effects of clopidogrel and prasugrel in hyperuricemic patients with HRPR.

Pharmacokinetic, pharmacodynamic, and pharmacogenetic assays to monitor clopidogrel therapy

Clopidogrel is the most common and widely used antiplatelet agent for patients with coronary artery disease following confirmation by electrocardiographic studies. The nonresponsiveness of patients to clopidogrel and the possibility of testing for clopidogrel resistance by platelet function assays (PFA) are contentious issues. Light transmission aggregometry (LTA) is considered as the gold standard test among all PFA. In this review, the most commonly used PFA used for monitoring the effect of clopidogrel, LTA, vasodilator-stimulated phosphoprotein assay phosphorylation, rotational thromboelastometry (ROTEM) delta and ROTEM platelet, thromboelastography, PFA-100, VerifyNow P2Y12 assay, Multiplate analyzer, Plateletworks assay and pharmacogenetic studies, are comparatively discussed including their principles of action, advantages, and disadvantages. VerifyNow P2Y12 assay can be accepted as the ideal point of care test out of the discussed assays. However, modified assays are required which could overcome the limitations associated with currently available assays.

Failure of platelet function analyser 200 to demonstrate clinical clopidogrel resistance in a patient undergoing intracranial vascular stenting

A patient undergoes intracranial stent insertion for stent-assisted coiling of a basilar tip aneurysm and left middle cerebral artery aneurysm. A flow diverting stent is also placed across an anterior communicating artery aneurysm. Prior to the procedure, the patient takes dual antiplatelet medications, being aspirin and clopidogrel. Because of the concern regarding in-stent thrombus and thromboembolic complications related to intracranial stenting and the high rate of clopidogrel resistance, preoperative platelet function testing (PFT) was undertaken to ensure platelet inhibition. In this case, PFT was performed on a platelet function analyser which demonstrated platelet inhibition. Ten days following the procedure, the patient represented with thromboembolic stroke. Repeat PFT performed with whole blood impedance aggregometry and despite full medication compliance demonstrated clopidogrel resistance. Clopidogrel was then ceased and prasugrel commenced. This case demonstrates the importance of appropriate platelet inhibition in patients with intracranial stents and the controversy surrounding PFT.

Measuring high on-treatment platelet reactivity in clinical practice; should we use a panel of platelet function tests?

: High on-treatment platelet reactivity (HPR) on P2Y12-inhibitors in patients treated with dual antiplatelet therapy is strongly associated with adverse ischaemic events. Studies have shown conflicting results with regard to the correlation and agreement between the different tests. Several assays are available to establish HPR. A composite advice based on more than one test might be a better way to identify HPR patients. To compare HPR rates and agreement between individual platelet function tests and a panel of three tests In our large percutaneous coronary intervention centre, all patients who suffered a stent thrombosis were invited back to a dedicated clinic. Platelet function testing was performed in all patients and matched control patients. HPR rates were compared between individual tests and with a composite comprised of three tests. A total of 242 patients were included, of whom in 193 patients all tests were available. HPR rates ranged from 14.6% [VerifyNow cut-off >235 platelet reactivity units (PRU)] to 49.7% (Vasodilator-Stimulated Phosphoprotein Assay). HPR according to the composite advice (≥2 out of 3 tests indicating HPR) was present in 29.8% of patients. The best correlation with the composite advice was observed with light transmittance aggregometry (kappa = 0.78) and VerifyNow (lower cut-off >208 PRU; kappa = 0.68). VerifyNow with cut-off more than 235 PRU identified the smallest proportion of patients with HPR, whereas Vasodilator-Stimulated Phosphoprotein Assay seemed to 'over-identify' HPR. In this real life patient cohort, a large variability was observed between four different platelet function tests. The use of a composite advice based on three tests is a promising alternative.

[Relation of Functional Activity of Platelets to Prognosis of Unfavorable Cardiovascular Events in Patients with Acute Coronary Syndrome. Results of a Registry Study]

AIM

to assess relation ofhigh functional activity ofplatelets to prognosis ofunfavorable cardiovascular events in patients with Acute Coronary Syndrome (ACS).

MATERIALS

The study was based on the data of a single center ACS registry conducted in the Central Clinical Hospital of the Presidential Affairs Department of Russian Federation. Of 529 included patients in 425 without contraindications to double antiplatelet therapy we carried out analysis of dependence of 30 days level of unfavorable events on parameters of functional activity of platelets.

RESULTS

High on-treatment platelet reactivity (HTPR) was found to be associated with 3.5 increase of mortality in the group of patients with high cardiovascular risk. Logistic model of prognosis of unfavorable events based on multifactorial analysis of data from patients with measured platelet aggregation included chronic kidney disease, type of myocardial infarction, and degree ofplatelet aggregation &gt;45%. C -statistic was equal to 0.77. We also present in this paper discussion of problems related to studying approaches to individualization of anti-aggregation therapy in real clinical practice and problems of organization ofsimilar studies.

CONCLUSION

The study showed that patients with ACS increased platelet aggregation, as well as chronic kidney disease and type 2 MI are associated with a 30 day prognosis of adverse events.

Optimal strategy of switching from clopidogrel to ticagrelor in Chinese acute coronary syndrome patients with complicated coronary artery disease: the switching from clopidogrel to ticagrelor (SHIFT-CACS) study

BACKGROUND

The dose and time point for switching from clopidogrel to ticagrelor remain controversial, especially for Chinese acute coronary syndrome (ACS) patients with complicated coronary artery disease (CAD). Hence, the purpose of this study was to further explore the optimal dose and time point for the switching strategy to balance the increase in platelet inhibition and the decrease in adverse events in Chinese ACS patients with complicated CAD managed by percutaneous coronary intervention (PCI).

METHODS

From July 2017 to December 2017, the prospective, randomized, open-label study (the SwitcHIng from clopidogrel to ticagrelor study) assigned the eligible Chinese ACS patients with complicated CAD managed by PCI (n = 102) for 90 mg of ticagrelor at 12 h (T-90 mg-12 h), 90 mg of ticagrelor at 24 h (T-90 mg-24h) or 180 mg ticagrelor at 24 h (T-180 mg-24 h) after the last dose of clopidogrel. The primary endpoint was the comparison of maximal platelet aggregation (MPA) values at 2 h after switching strategies among the three groups. In addition, the MPA values at baseline, 8 h and before discharge and the rates of high on-treatment platelet reactivity were evaluated, the incidences of bleeding episodes and dyspnea during hospitalization and at 30-day follow-up in our study were also recorded. The MPA was measured by light transmittance aggregometry in our study. A repeated-measures analysis of variance (ANOVA) model and one-way ANOVA were used to compare data for the primary endpoint.

RESULTS

The MPA values were significantly decreased in the T-180 mg-24 h group compared with the T-90 mg-12 h group (P = 0.017) and decreased numerically compared with the T-90 mg-24 h group (P = 0.072) at 2 h. In particular, the MPA values were markedly reduced in the T-90 mg-24 h group compared with the T-90 mg-12 h group at 8 h after switching treatment (P = 0.002). There was no significant difference among the three groups in all bleedings and dyspnea events.

CONCLUSIONS

The optimal treatment strategy recommended in this study for Chinese ACS patients with complicated CAD managed by PCI is 180 or 90 mg of ticagrelor at 24 h after the last dose of clopidogrel. In addition, a negative interaction was detected in this study between the overlap for clopidogrel and ticagrelor at 12 h after the last dose of clopidogrel.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03577652; http://clinicaltrials.gov/ct2/show/NCT03577652.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Relationship between high platelet reactivity on clopidogrel and long-term clinical outcomes after drug-eluting stents implantation (PAINT-DES): a prospective, propensity score-matched cohort study

Background

The relationship between platelet reactivity and long-term clinical outcomes remains controversial. The present prospective study was designed to explore the association between high platelet reactivity (HPR) on clopidogrel and long-term clinical outcomes following implantation of drug eluting stents (DES).

Methods

A total of 1769 consecutive patients assessed by Aggrestar (PL-11) were enrolled at our center from February 2011 to December 2017. The primary end point was major adverse cardiovascular and cerebrovascular events (MACCE), defined as definite or probable stent thrombosis, spontaneous myocardial infarction, all cause death, clinically driven target vessel revascularization (TVR), or ischemic stroke. Bleeding served as the safety endpoint. Propensity score matching (PSM) analysis was performed to adjust for baseline differences in the overall cohort.

Results

Finally, 409 patients (23.1%) were identified with HPR on clopidogrel. At a median follow-up of 4.1 years (interquartile range, 1.8 years), the occurrence of MACCE was significantly higher in HPR on clopidogrel group than normal platelet reactivity (NPR) on clopidogrel group (15.6% vs. 5.4%, p < 0.001). After PSM, 395 paired patients were matched, and the difference in MACCE between HPR (15.7%) versus NPR (9.4%) on clopidogrel groups remained significant (P < 0.001), mainly driven by increased all cause death (5.3% vs. 1.8%, p < 0.001), and clinically driven TVR (8.1% vs. 6.3%, p = 0.019) in the HPR group. The risk of bleeding between two groups was similar.

Conclusions

This prospective study confirms the relationship between HPR on clopidogrel and long-term adverse cardiovascular events after coronary stenting.

Electronic supplementary material

The online version of this article (10.1186/s12872-018-0841-1) contains supplementary material, which is available to authorized users.

Blockade of protease-activated receptor-4 (PAR4) provides robust antithrombotic activity with low bleeding

Antiplatelet agents are proven efficacious treatments for cardiovascular and cerebrovascular diseases. However, the existing drugs are compromised by unwanted and sometimes life-threatening bleeding that limits drug usage or dosage. There is a substantial unmet medical need for an antiplatelet drug with strong efficacy and low bleeding risk. Thrombin is a potent platelet agonist that directly induces platelet activation via the G protein (heterotrimeric guanine nucleotide-binding protein)-coupled protease-activated receptors PAR1 and PAR4. A PAR1 antagonist is approved for clinical use, but its use is limited by a substantial bleeding risk. Conversely, the potential of PAR4 as an antiplatelet target has not been well characterized. Using anti-PAR4 antibodies, we demonstrated a low bleeding risk and an effective antithrombotic profile with PAR4 inhibition in guinea pigs. Subsequently, high-throughput screening and an extensive medicinal chemistry effort resulted in the discovery of BMS-986120, an orally active, selective, and reversible PAR4 antagonist. In a cynomolgus monkey arterial thrombosis model, BMS-986120 demonstrated potent and highly efficacious antithrombotic activity. BMS-986120 also exhibited a low bleeding liability and a markedly wider therapeutic window compared to the standard antiplatelet agent clopidogrel tested in the same nonhuman primate model. These preclinical findings define the biological role of PAR4 in mediating platelet aggregation. In addition, they indicate that targeting PAR4 is an attractive antiplatelet strategy with the potential to treat patients at a high risk of atherothrombosis with superior safety compared with the current standard of care.

Decreased platelet inhibition by P2Y12 receptor blockers in anaemia

BACKGROUND

Anaemic patients undergoing angioplasty and stenting are at an increased risk of ischaemic events, which may be caused by an inadequate response to antiplatelet therapy with adenosine diphosphate (ADP) P2Y₁₂ inhibitors. In the current study, we investigated the associations between anaemia and on-treatment platelet reactivity in clopidogrel-treated (group 1, n = 306) and prasugrel-/ticagrelor-treated (group 2, n = 109) patients undergoing elective and acute angioplasty with stent implantation, respectively.

MATERIALS AND METHODS

Monocyte-platelet aggregate (MPA) formation was determined by flow cytometry in both groups. On-treatment residual platelet reactivity in response to ADP was assessed by light transmission aggregometry (LTA) in both groups, and by the VerifyNow P2Y₁₂ assay and the Impact-R in group 1. P-selectin expression was measured by flow cytometry in group 2.

RESULTS

In both groups, anaemia was associated with significantly higher MPA formation in response to ADP (both P ≤ .02). Moreover, by LTA maximal aggregation in response to ADP was significantly higher in patients with anaemia in both groups (both P < .05), and anaemic patients in group 1 had a significantly higher on-treatment platelet reactivity by the VerifyNow P2Y₁₂ assay and the Impact-R than those without anaemia (both P < .001). In group 2, significantly higher platelet surface expression of P-selectin was seen in anaemia after stimulation with ADP (P = .02).

CONCLUSION

Anaemia is associated with decreased platelet inhibition by ADP P2Y₁₂ receptor antagonists after elective and acute percutaneous interventions with stent implantation. However, due to inconsistencies between different platelet function tests additional data are needed to clarify the role of anaemia for platelet inhibition.

Platelet function testing in acute cardiac care – is there a role for prediction or prevention of stent thrombosis and bleeding?

The role of platelet function testing in acute coronary syndrome patients undergoing percutaneous coronary intervention remains controversial despite the fact that high platelet reactivity is an independent predictor of stent thrombosis and emerging evidence suggests also a link between low platelet reactivity and bleeding. In this expert opinion paper, the Study Group on Biomarkers in Cardiology of the Acute Cardiovascular Care Association and the Working Group on Thrombosis of the European Society of Cardiology aim to provide an overview of current evidence in this area and recommendations for practicing clinicians.

Analysing responses to aspirin and clopidogrel by measuring platelet thrombus formation under arterial flow conditions

High residual platelet aggregability and circulating platelet-monocyte aggregates in patients administered aspirin and clopidogrel are associated with ischaemic vascular events. To determine the relevance of these factors with residual thrombogenicity, we measured platelet thrombus formation using a microchip-based flow-chamber system in cardiac patients receiving aspirin and/or clopidogrel, and evaluated its correlation with agonist-inducible platelet aggregation and platelet-monocyte aggregates. Platelet thrombus formation was analysed by measuring flow pressure changes due to the occlusion of micro-capillaries and was quantified by calculating AUC10 (area under the flow pressure curve). The growth and stability of platelet thrombi that formed inside microchips at shear rates of 1000, 1500, and 2000 s-1 were markedly reduced in patients receiving aspirin and/or thienopyridine compared to healthy controls (n=33). AUC10 values of aspirin therapy patients (n=20) were significantly lower and higher than those of healthy controls and dual antiplatelet therapy patients (n=19), respectively, and showed relatively good correlations with collagen-induced platelet aggregation and platelet-monocyte aggregates at 1000 and 1500 s-1 (r s >0.59, p<0.01). In contrast, AUC10 in dual antiplatelet therapy patients was significantly correlated with ADP-induced platelet aggregation at all examined shear rates (r s >0.59, p<0.01), but did not correlate with collagen-induced aggregation. Aspirin monotherapy patients with high residual platelet thrombogenicity also exhibited significant elevations in both collagen-induced platelet aggregation and platelet-monocyte aggregates. Our results, although preliminary, suggest that residual platelet thrombogenicity in aspirin-treated patients is associated with either collagen-induced platelet aggregation or circulating platelet-monocyte aggregates, but it is predominantly dependent on ADP-induced platelet aggregation in patients receiving dual antiplatelet therapy.

Platelet activation is less enhanced in the new balloon expandable Edwards Sapien 3 valve compared to its predecessor model (Edwards Sapien XT)

Stroke and thromboembolic events after transfemoral aortic valve replacement (TAVR) continue to be a problem. The aim of our study was to compare platelet aggregation (Agg) and platelet activation (PA) observed with two different catheter valves, the ESV-XT and the newer ESV-3 valve in patients (pts) undergoing TAVR on dual antiplatelet therapy (DAPT). A total of 174 patients with severe aortic stenosis and high surgical risk successfully underwent TAVR (60 ESV-XT; 114 ESV-3). Platelet Agg and PA (CD62P expression) were evaluated before and the following three days after TAVR under DAPT. Platelet Agg was inhibited to the same extent in both valve types and there was no significant difference in platelet drop between both valve types between day 0 and day 3 [ESV-XT vs ESV-3: median (25th-75th percentile): platelet count (x1000): 55 (42–74) vs 61(42–93), p=0.280]. However, there was an enhanced CD62P expression directly after TAVR with the ESV-XT compared to the ESV-3 [CD62P (MIF): 7.4 (6.8–8.6) vs 6.6 (6–7.9), p=0.014]. Surface expression of platelet CD62P was associated with the occurrence of residual aortic regurgitation (AR) and was significantly higher in patients with residual AR [CD62P (mild AR) vs CD 62P (no or trace AR): 7.9 (7.3–9.1) vs 7.1 (6.4–8.0), p < 0.001)]. PA was significantly enhanced in patients with the ESV-XT compared to the ESV-3 valve and was associated with the amount of residual AR which was significantly reduced by ESV-3. This may have implications for thromboembolic events following TAVR procedure

Platelet reactivity-adjusted antiplatelet therapy in patients with percutaneous coronary intervention: a meta-analysis of randomized controlled trials

Numerous number of evidences show that high on-treatment platelet reactivity is a well-known risk factor for adverse events in patients after percutaneous coronary intervention (PCI). Controversial situations still exist regarding the effectiveness of tailoring antiplatelet therapy according to platelet function monitoring. The PubMed, Embase, and Cochrane Central databases were searched for randomized trials comparing platelet reactivity-adjusted antiplatelet therapy with conventional antiplatelet therapy in patients undergoing PCI. The primary end point was all-cause mortality, major adverse cardiac events (MACE) including cardiovascular (CV) death, nonfatal myocardial infarction (MI), definite/probable stent thrombosis (ST), revascularization, and stroke or transient ischemic attack (TIA). The safety end point was defined as major bleeding events. We derived pooled risk ratios (RRs) with fixed-effect models. Six studies enrolling 6347 patients were included. Compared with conventional treatment, tailoring antiplatelet failed to reduce all-cause mortality (RR: 0.89, 95% confidence interval [CI]: 0.63-1.24, P = 0.48), MACE (RR: 1.02, 95% CI: 0.92-1.14, P = 0.69), MI (RR: 1.07, 95% CI: 0.95-1.21, P = 0.24), CV death (RR: 0.69, 95% CI: 0.40-1.19, P = 0.09), ST (RR: 0.83, 95% CI: 0.50-1.38, P = 0.23), stroke or TIA (RR: 1.08, 95% CI: 0.55-2.12, P = 0.83), revascularization (RR: 0.96, 95% CI: 0.69-1.33, P = 0.79), and major bleeding events (RR: 0.79, 95% CI: 0.53-1.17, P = 0.24). Compared with traditional antiplatelet treatment, tailoring antiplatelet therapy according to platelet reactivity testing failed to reduce all-cause mortality, MACE, and major bleeding events in patients undergoing PCI.

How I use laboratory monitoring of antiplatelet therapy

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

CRUSADE Score is Superior to Platelet Function Testing for Prediction of Bleeding in Patients Following Coronary Interventions

Hypothetically, diminished platelet reactivity (PR) during dual antiplatelet therapy (DAPT) should cause extra major bleeding events (MBE), although definite evidence is lacking. Multiple scores have been proposed to stratify bleeding risk, but their predictive value during DAPT is unclear. We compared the performance of the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the ACC/AHA Guidelines (CRUSADE) with PR testing to predict MBE in Korean patients with acute coronary syndrome. We screened 1105, and included 903 consecutive patients who underwent coronary interventions. All patients received DAPT, while MBE were assessed by BARC scale. Admission platelet reactivity was assessed with VerifyNow Analyzer simultaneously with CRUSADE score, and MBE were collected at 1 month and at 1 year post stenting. There were a total of 113 (11%) MBE at 1 month, and extra 41(5%) MBE at 1 year. At 1 month MBE prediction was superior by CRUSADE score (AUC: 0.816, 95% CI: 0.79 0.84, p < 0.0001), compared to PR (AUC: 0.605, 95% CI: 0.572–0.637, p = 0.0007). Moreover, CRUSADE score remains the independent predictor of MBE by multivariate analyses (OR = 2.94, 95% CI: 2.18–3.96, p < 0.0001). At 1 year MBE also correlated, but were not significantly different between admission CRUSADE score (AUC: 0.62, 95% CI: 0.58 0.66, p = 0.0183) and PR (AUC: 0.674, 95% CI: 0.63–0.71, p = 0.002). We conclude that MBE are more common in real life than reported in clinical trials. CRUSADE score was superior to PR testing for predicting short-term, but not 1 year MBE in Korean patients undergoing percutaneous coronary intervention and treated with DAPT.

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Dual antiplatelet therapy for 1 year is a golden standard following coronary stenting in patients with acute coronary syndromes.

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Bleeding is a life-threatening major complication associated with chronic aggressive antiplatelet strategies.

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Predicting bleeding based on clinical features or established biomarkers is upmost yet unsolved mystery affecting clinical outcomes in such high-risk patients

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The CRUSADE clinical score predicts bleeding better than platelet reactivity indices

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Short-term bleedings at 30 days, but not delayed 1-yearly hemorrhages were better predicted by CRUSAIDE in East Asians.

Dual antiplatelet therapy for 1 year is common following coronary stenting in patients with acute coronary syndromes. However, bleeding is a life-threatening major complication and shortcoming associated with chronic aggressive antiplatelet strategies. CRUSADE score was introduced for better prediction of in-hospital bleeding, while delayed bleeding risks remained unclear. Usually bleeding risk is assessed based on clinical features or by established biomarkers We tested the hypothesis on the superiority of CRUSADE score versus conventional platelet reactivity in a large Korean registry, and revealed the following: major bleeding events in real life are more frequent, and are heavily unreported in clinical trials; the CRUSADE clinical score predicts bleeding better than platelet reactivity indices. Unfortunately, short-term bleedings at 30 days, but not delayed 1-yearly hemorrhages were better predicted by CRUSADE in East Asians.

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.

Rapid Evaluation of Platelet Function With T2 Magnetic Resonance

Objectives: The clinical diagnosis of qualitative platelet disorders (QPDs) based on light transmission aggregometry (LTA) requires significant blood volume, time, and expertise, all of which can be barriers to utilization in some populations and settings. Our objective was to develop a more rapid assay of platelet function by measuring platelet-mediated clot contraction in small volumes (35 µL) of whole blood using T2 magnetic resonance (T2MR).

Methods: We established normal ranges for platelet-mediated clot contraction using T2MR, used these ranges to study patients with known platelet dysfunction, and then evaluated agreement between T2MR and LTA with arachidonic acid, adenosine diphosphate, epinephrine, and thrombin receptor activator peptide.

Results: Blood from 21 healthy donors was studied. T2MR showed 100% agreement with LTA with each of the four agonists and their cognate inhibitors tested. T2MR successfully detected abnormalities in each of seven patients with known QPDs, with the exception of one patient with a novel mutation leading to Hermansky-Pudlak syndrome. T2MR appeared to detect platelet function at similar or lower platelet counts than LTA.

Conclusions: T2MR may provide a clinically useful approach to diagnose QPDs using small volumes of whole blood, while also providing new insight into platelet biology not evident using plasma-based platelet aggregation tests.

Low-dose ticagrelor yields an antiplatelet efficacy similar to that of standard-dose ticagrelor in healthy subjects: an open-label randomized controlled trial

Ticagrelor has a greater antiplatelet efficacy than clopidogrel but may be accompanied by an increased risk of bleeding. This study evaluated the antiplatelet effect and pharmacokinetic profile of low-dose ticagrelor in healthy Chinese volunteers. Thirty healthy subjects were randomized to receive standard-dose ticagrelor (180-mg loading dose, 90-mg twice daily [bid] [n = 10]), low-dose ticagrelor (90-mg loading dose, 45-mg bid [n = 10]), or clopidogrel (600-mg loading dose, 75-mg once daily [n = 10]). Platelet reactivity was assessed by using the VerifyNow P2Y12 assay at baseline and 0.5, 1, 2, 4, 8, 24, 48, and 72 hours post-dosing. The ticagrelor and AR-C124910XX concentrations were measured for pharmacokinetic analysis. The percentage inhibition of P2Y12 reaction units was higher in the low-dose and standard-dose ticagrelor group than in the clopidogrel group at 0.5, 1, 2, 4, 8, and 48 hours post-dosing (P < 0.05 for all), but did not differ significantly between the two ticagrelor doses at any time-point (P > 0.05). The plasma ticagrelor and ARC124910XX concentrations were approximately 2-fold higher with standard-dose versus low-dose ticagrelor. No serious adverse events were reported. In conclusion, low-dose ticagrelor achieved faster and higher inhibition of platelet functions in healthy Chinese subjects than did clopidogrel, with an antiplatelet efficacy similar to that of standard-dose ticagrelor.

Platelet function testing in cardiac surgery

Bleeding in cardiac surgery is known to cause increased morbidity and mortality. The rise in the use of anti-platelet medication has led to an increase in the number of patients presenting for cardiac surgery with platelet dysfunction, who are at a heightened risk of bleeding. However, the extent of platelet inhibition is well known to differ among individuals. In the past few years, a number of point-of-care platelet function testing devices, which may be able to assess platelet reactivity, have entered the market. This review will examine the devices most commonly studied and the evidence surrounding their use in cardiac surgery and their effect on blood loss.

Platelet function testing as a biomarker for efficacy of antiplatelet drugs

Despite the overwhelming evidence in support of the efficacy of dual antiplatelet therapy with aspirin and clopidogrel, it is also obvious that not all patients benefit from these drugs to the same extent. This interindividual variability in platelet responses may underlie clinical differences in drug efficacy, with potential for optimization of antiplatelet therapy to prevent ischemic events without excessively increasing bleeding risk. This review presents the current evidence regarding platelet function testing for monitoring of antiplatelet therapy, with emphasis on the prognostic value of platelet function testing to predict ischemic and bleeding events. The potential of platelet function testing to provide personalized antiplatelet therapy is also discussed, with an outlook toward the future of platelet function testing in high-risk individuals.

Validation of Three Platelet Function Tests for Bleeding Risk Stratification During Dual Antiplatelet Therapy Following Coronary Interventions

BACKGROUND

Although low platelet reactivity (LPR) is commonly detected during bleeding, a validated threshold for reliable DAPT bleeding risk stratification is lacking. We tested the diagnostic utility of 3 conventional platelet-activity assays to define the predictive value (if any) of LPR for bleeding.

HYPOTHESIS

We hypothesized whether one of these tests be better than any others for predicting bleeding events.

METHODS

Patients (n = 800) following drug-eluting stent implantation received DAPT. Bleeding was assessed by Bleeding Academic Research Consortium (BARC) classification and events were collected for 1 year after stenting. Platelet reactivity was measured by light transmittance aggregometry (LTA), VerifyNow, and multiple electrode aggregometry (MEA). The LPR values for bleeding event stratification were defined as ≤15% for LTA, ≤139 PRU for VerifyNow, and ≤25 U for MEA.

RESULTS

Bleeding events occurred in 18 patients (2.3%). All tests distinguished LPR as an independent predictor for bleeding by univariate analysis ([HR]: 5.00, 95% [CI]: 1.8-14.0, P = 0.002 for LTA; HR: 21.3, 95% CI: 6.2-73.0, P < 0.0001 for VerifyNow; and HR: 7.4, 95% CI: 2.2-25.5, P = 0.002 for MEA). Multivariate analysis revealed that only VerifyNow (HR: 11.5, 95% CI: 2.9-45.7, P < 0.0004) remained an independent predictor for bleeding. However, the specificity (81.5%, 60.2%, and 81.7%, respectively) and sensitivity (61.1%, 83.3%, and 83.2%, respectively) of all 3 tests were quite low.

CONCLUSIONS

Among 3 conventional platelet-activity assays, VerifyNow was better than LTA or MEA for triaging future bleeding risks. However, all 3 tests failed to reliably predict future bleeding.

CYP2C19*2 and Other Allelic Variants Affecting Platelet Response to Clopidogrel Tested by Thrombelastography in Patients with Acute Coronary Syndrome

Background:

To investigate the contributions of CYP2C19 polymorphisms to the various clopidogrel responses tested by thrombelastography (TEG) in Chinese patients with the acute coronary syndrome (ACS).

Methods:

Patients were screened prospectively with ACS diagnose and were treated with clopidogrel and aspirin dual antiplatelet therapy. CYP2C19 loss of function (LOF) and gain of function (GOF) genotype, adenosine 5′-diphosphate (ADP)-channel platelet inhibition rate (PIR) tested by TEG and the occurrence of 3-month major adverse cardiovascular events and ischemic events were assessed in 116 patients.

Results:

High on-treatment platelet reactivity (HTPR) prevalence defined by PIR <30% by TEG in ADP-channel was 32.76% (38/116). With respect to the normal wild type, CYP2C19*2, and *3 LOF alleles, and *17 GOF alleles, patients were classified into three metabolism phenotypes: 41.38% were extensive metabolizers (EMs), 56.90% were intermediate metabolizers (IMs), and 1.72% were poor metabolizers (PMs). Of the enrolled patients, 31.47%, 5.17%, and 0.43%, respectively, were carriers of *2, *3, and *17 alleles. The HTPR incidence differed significantly according to CYP2C19 genotypes, accounting for 18.75%, 41.54%, and 100.00% in EMs, IMs, and PMs, respectively. Eighteen (17.24%) ischemic events occurred during the 3-month follow-up, and there was a significant difference in ischemic events between HTPR group and nonhigh on-treatment platelet reactivity group.

Conclusions:

Genetic CYP2C19 polymorphisms are relative to the inferior, the antiplatelet activity after clopidogrel admission and may increase the incidence of ischemic events in patients with ACS.

Ticagrelor overcomes high platelet reactivity in patients with acute myocardial infarction or coronary artery in-stent restenosis: a randomized controlled trial

High on-treatment platelet reactivity (HTPR) is accompanied by an increased risk of adverse outcomes. Direct comparison of the antiplatelet effects between ticagrelor and high-dose clopidogrel has not yet been reported in acute myocardial infarction (AMI) or coronary artery in-stent restenosis (ISR) patients with HTPR. Consecutive patients with AMI or coronary artery ISR treated with standard-dose clopidogrel (75 mg/day) were screened with the VerifyNow assay, defining HTPR as P2Y12 reaction units (PRUs) >208. Of the 102 screened patients, 48 (47.06%) patients with HTPR were randomly assigned to either ticagrelor (180 mg/90 mg twice daily) or high-dose clopidogrel (150 mg/day) for 24 hours. Baseline characteristics and mean PRUs were similar in both groups. After 24 hours, ticagrelor was associated with a significantly lower platelet reactivity than high-dose clopidogrel (44.38 ± 40.26  vs. 212.58 ± 52.34 PRU, P < 0.05). No patient receiving ticagrelor exhibited HTPR, whereas 15 (62.50%) patients after treatment with high-dose clopidogrel remained HTPR (P < 0.05). During the follow-up (mean, 138.42 ± 53.59 days), no patient exhibited a major bleeding event in either treatment group. In conclusion, in patients with AMI or coronary artery ISR exhibiting HTPR after standard clopidogrel treatment, ticagrelor is significantly more effective compared with high-dose clopidogrel in overcoming HTPR.

Monitoring ASA and P2Y12-specific platelet inhibition--comparison of conventional (single) and multiple electrode aggregometry

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.

Impact of tailored anti-P2Y12 therapies in acute coronary syndromes

Acute coronary syndromes are a major disease burden and the prognosis has improved over the last decades due to improvement of medical and interventional treatments. Novel P2Y12-ADP-receptor antagonists have been introduced into clinical treatment offering more potent and rapid onset of action with the downside of increased bleeding risk. This special report will focus on interindividual variability of antiplatelet drugs in the setting of acute coronary syndromes and the current impact and potential future of point-of-care testing to personalize therapy aiming to improve prognosis in acute coronary syndrome patients.

Prostaglandin E1 potentiates the effects of P2Y12 blockade on ADP-mediated platelet aggregation in vitro: Insights using short thromboelastography

In addition to adenosine diphosphate (ADP), a number of platelet function tests including the VerifyNow P2Y12 assay (VN-P2Y12) employ prostaglandin E1 (PGE1) to improve specificity for P2Y12 blockade by mitigating the contribution of the P2Y1 pathway on ADP-mediated platelet aggregation. Using short thromboelastography (s-TEG), we have previously shown that VN-P2Y12 overestimates the functional effect of clopidogrel in some individuals. We investigated whether PGE1 systematically increases the inhibitory effects of P2Y12 blockade on ADP-mediated platelet aggregation in an in vitro model. Using s-TEG, we measured ADP-induced platelet aggregation either in the presence or absence of PGE1 (11 or 22 nM) in blood samples taken from healthy volunteers pre-incubated with prasugrel active metabolite (PAM; 0, 1, 3 or 10 µM). Individually, both PGE1 (p < 0.02) and PAM (p < 0.0001) inhibited ADP-mediated platelet aggregation in a dose-dependent manner, as expected. Furthermore, inclusion of PGE1 augmented inhibition of ADP-mediated platelet aggregation in response to PAM (p < 0.02) in a dose-dependent manner such that a 10-fold higher dose of PAM was required to attain equivalent inhibition of ADP-mediated platelet aggregation to that achieved by 1 µM PAM in the presence of 11 nM PGE1. In conclusion, PGE1 potentiates the anti-aggregatory effects of P2Y12 blockade on ADP-mediated platelet aggregation. Assays that employ PGE1 with ADP may therefore overestimate therapeutic response to prasugrel in a proportion of individuals, potentially making them unsuitable candidates for guiding delivery of personalized antiplatelet therapy.