血小板功能实验预测氯吡格雷用于缺血性卒中二级预防的有效性和安全性分析

目的 探讨透射光法血小板聚集实验(light transmittance aggregometry,LTA)、血栓弹力图(thromboelastography,TEG)和血小板功能分析仪(platelet function analyzer,PFA)三种血小板功能实验对轻型缺血性卒中患者临床结局的预测价值.方法 前瞻...     

Evaluation of the platelet count drop method for assessment of platelet function in comparison with “gold standard” light transmission aggregometry

Introduction

Hyporesponsiveness to antiplatelet agents has been linked to an increased risk of major adverse cardiovascular events. However, light transmission aggregometry (LTA), the gold standard methodology for assessing platelet function, requires expertise and is labour-intensive, which render its use in clinical settings impractical. We assessed whether platelet count drop (PCD), a technique widely available in any haematology laboratory, could replace LTA in testing for inhibition of platelet aggregation induced by antiplatelet agents.

Materials and methods

One hundred and sixty-one coronary artery disease patients taking aspirin alone and 91 patients taking a combination of aspirin and clopidogrel were enrolled. Platelet aggregation was measured by LTA and PCD stimulated with 1.6 mM of arachidonic acid (AA) for aspirin and 5 and 20 μM of adenosine diphosphate (ADP) for clopidogrel.

Results

Correlation between AA-induced LTA and PCD was inexistent (r = - 0.043, p = 0.587), while correlation between ADP-induced LTA and PCD was low (r = 0.374, p < 0.0001 for ADP 5 μM and r = 0.402, p < 0001 for ADP 20 μM). PCD, whether stimulated with AA or ADP, overestimated platelet aggregation as assessed by LTA, by 13-18%. The wide 95% limits of agreement suggest that the assays can disagree significantly in individual patients.

Conclusions

Although the PCD method is widely available in non-specialized laboratories, our results demonstrate that there is poor correlation with the current gold standard, i.e. LTA. Thus, PCD should not be used in replacement of LTA to assess antiplatelet responsiveness.     

Aspirin platelet reactivity on platelet function and clinical outcome in minor stroke or transient ischemic attack

ObjectiveWhether aspirin platelet reactivity affects platelet function and clinical outcomes with different antiplatelet therapies in patients with mild stroke or transient ischemic attack (TIA) remains unclear. We conducted a subgroup analysis of the PRINCE trial.Materials and methodsPatients with mild stroke or TIA were randomized into aspirin+ticagrelor, or aspirin+clopidogrel groups; aspirin reaction units (ARU) were measured at the baseline and after 7 ± 2 days to assess response to treatment. High on-treatment platelet reactivity (HPR) was defined as ≥550 ARU (poor response to aspirin). The platelet functions of ticagrelor and clopidogrel were measured using the VerifyNow P2Y₁₂ assay for P2Y₁₂ reaction units (PRU); HPR to P2Y₁₂ was defined as >208 PRU (poor response to P2Y₁₂). Clinical outcomes included stroke and clinical vascular and bleeding events after 90 days.ResultsAmong 628 enrolled patients, 69 (11%) were poor aspirin responders. After 7 ± 2 days, the proportion of poor P2Y₁₂ responders for ticagrelor versus clopidogrel significantly reduced in poor (2.6% versus 27.4%) and good (14.3% versus 29.4%) aspirin responders. There were significant interactions between treatment groups, and between treatment groups and aspirin platelet reactivity for poor P2Y₁₂ responders (P = 0.01). After 90 ± 7 days, there were no significant interactions between treatment groups and aspirin platelet reactivity for new stroke risk (good aspirin responders: 5.5% versus 8.8%, hazard ratio [HR]: 0.61; 95% confidence interval [CI], 0.32 to 1.16; P = 0.13; poor aspirin responders: 8.6% versus 8.8%, HR: 0.97, 95% CI: 0.20–4.81; P = 0.97; P for interaction = 0.60). Major bleeding was less frequent in poor than good aspirin responders (ticagrelor/aspirin: 0.4%/0%; clopidogrel/aspirin: 1.4%/0%).ConclusionsIn patients with minor stroke or TIA, clopidogrel, and particularly ticagrelor, decreased platelet function in poor versus good aspirin responders. The poor platelet reactivity of aspirin could not sufficiently reduce the risk of recurrent stroke with ticagrelor or clopidogrel; however, HPR (poor aspirin response) may have a protective effect on clinically relevant major bleeding.     

Baseline platelet size is increased in patients with acute coronary syndromes developing early stent thrombosis and predicts future residual platelet reactivity. A case-control study

Introduction

Pre-procedural predictors of early stent thrombosis (ST) and future response to platelet inhibitors are in demand. We sought to evaluate the impact of baseline platelet indices on the occurrence of early ST and future residual platelet reactivity.

Materials and methods

Hundred and eight patients with acute coronary syndromes (ACS) in whom stents were implanted were included: 36 consecutive ST cases and 72 matched controls. Platelet indices assessed with flow cytometry before stent implantation were retrieved from the department's data base. Residual platelet reactivity specific to aspirin (aspirin reaction units-ARU) and clopidogrel (P2Y12 reaction units-PRU) was assessed prospectively with VerifyNow^® under dual antiplatelet treatment.

Results

Platelet size reported as mean platelet volume (MPV) or proportion of large platelets (LPLT) was significantly higher in ST cases compared with controls (10.4, 95% confidence intervals [CI], 10.1-10.8 vs. 9.7, CI, 9.5-9.9, P = 0.0004 and 35.8, CI, 34.2-37.3 vs. 33.3, CI, 32.2-34.3, P = 0.007, respectively). Dual aspirin and clopidogrel poor-responsiveness was diagnosed significantly more often in ST cases than in controls (19.6% vs. 1.4%, P = 0.004), whereas no difference was observed for single aspirin or clopidogrel poor-responsiveness. A strong correlation was found between MPV and both, ARU (r = 0.66, P < 0.0001) and PRU (r = 0.55, P < 0.0001). Similarly, higher LPLT was associated with higher ARU (r = 0.47, P < 0.0001) and PRU (r = 0.38, P = 0.0001).

Conclusions

Baseline platelet size is increased in patients with ACS developing early ST and correlates with future residual platelet reactivity under aspirin and clopidogrel therapy. Dual but not isolated aspirin or clopidogrel poor-responsiveness appears to be associated with early ST.     

Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests

Background

The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response.Patients and methodsWe studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19 + assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor).

Results

Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R.

Conclusion

Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.     

Insights into the inhibition of platelet activation by omega-3 polyunsaturated fatty acids: beyond aspirin and clopidogrel

Objectives

We sought to examine the effects of escalating doses of omega-3 polyunsaturated fatty acid (PUFA) supplements on platelet function using light transmission aggregometry (LTA) and electrophoretic quasi-elastic light scattering technology (EQELS).

Background

PUFA may inhibit platelet function through fatty acid substitution in the platelet membrane by changing the surface charge density and causing decreased production of thromboxane A2. EQELS can measure platelet surface charge density and determine whether the platelet is in resting or activated state.

Methods

A total of 30volunteers were divided in 3 groups of 10 as follows: Group A, no antiplatelet agent; Group B, daily aspirin only, and Group C, daily aspirin and clopidogrel. All patients received escalating doses of omega-3PUFA from 1 to 8 g daily over 24 weeks. Platelet function was measured by template bleeding time, LTA, and EQELS at baseline and at 6, 12, 18 and 24 weeks.

Results

Mean bleeding time increased in a dose-dependent manner with escalating omega-3 PUFA doses. LTA confirmed expected antiplatelet effects of aspirin and clopidogrel, but did not detect any additional antiplatelet effects of omega-3 PUFA. EQELS showed a significant increase in the negative resting platelet charge compared to baseline and an attenuated response to arachidonic acid mediated platelet activation. No bleeding events were observed.

Conclusions

In this pilot study we were able to successfully measure platelet surface charge variation as a measure of omega-3 PUFA effect on platelets. Our results suggest that omega-3 PUFA increase the total platelet surface charge and, therefore, attenuate platelet activation, even among patients taking aspirin or aspirin plus clopidogrel. Further studies are needed to determine the clinical significance of these measured effects and EQELS results.     

Impact of the proton pump inhibitors and CYP2C19*2 polymorphism on platelet response to clopidogrel as assessed by four platelet function assays

Background

Previous studies suggested a possible negative interference of proton pump inhibitors (PPIs) on clopidogrel’s antiplatelet effect because of the competitive inhibition of the CYP 2C19 isoenzyme. Moreover, carriers of the loss-of-function allele of CYP2C19 polymorphism (CYP2C19*2) display significantly lower responses to clopidogrel. In this study, we investigated the association between CYP2C19*2 genotype, PPI intake and clopidogrel resistance in patients with coronary artery disease (CAD) and their effect on clinical outcome.

Methods

We recruited 95 patients with CAD receiving chronic clopidogrel therapy in combination with aspirin. Platelet reactivity was simultaneously assessed by INNOVANCE PFA-100 P2Y, ADP-induced light transmission aggregometry (LTA), flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and multiple electrode aggregometry (Multiplate). Cardiovascular outcomes were recorded during 1-year follow-up period.

Results

Only platelet reactivity assessed by measuring platelet phosphorylated-VASP demonstrated a significant higher platelet reactivity in carriers of CYP2C19*2 (p = 0.023). The other methods displayed higher - but not statistically significant - platelet reactivity in patients carrying the CYP2C19*2 variant as compared with non-carriers. Patients on PPIs demonstrated almost similar suppression of platelet reactivity in comparison with those not treated with PPIs by all platelet function assays. In logistic regression analysis none of the platelet function assays measurements were related with clinical outcomes. Similarly neither CYP2C19*2 genetic variant nor PPI treatment were associated with adverse clinical events.

Conclusions

PPI co-administration did not influence clopidogrel’s antiplatelet effect on laboratory testing by all platelet function assays used. On the contrary, patients carrying CYP2C19*2 genotype had significantly higher residual platelet reactivity as estimated by VASP-phosphorylation assay.     

Genetic determinants of high on-treatment platelet reactivity in clopidogrel treated Chinese patients

Introduction

Cytochrome P450 (CYP), ATP-binding cassette transporters (ABCB1), and paraoxonase-1 (PON1) play crucial roles in clopidogel absorption and bioactivation. Genetic polymorphisms in these genes have been associated with the variability of the response to clopidogrel, however their contribution to high on-treatment platelet reactivity (HPR) in clopidogrel treated Chinese patients is less known.

Materials and methods

Five-hundred Chinese-Han patients treated with clopidogrel for acute coronary syndrome (ACS) were consecutively recruited from the Department of Geriatric Cardiology, General Hospital of Chinese People’s Liberation Army, from September 2010 to September 2012. We assessed the relations of CYP2C19*2 (rs4244285), CYP2C19*3 (rs4986893), CYP2C19*17 (rs12248560), PON1Q129R (rs662) and ABCB1C3435T (rs1045642) to the platelet aggregation after 5 days maintenance dose of clopidogrel administration, and the risk for HPR. The cutoff of HPR was defined as 20 μmol/L adenosine diphosphate (ADP)-induced platelet aggregation > 50%.

Results

Both CYP2C19*2 and *3 alleles were significantly associated with higher platelet aggregation after 5 days maintenance dose of clopidogrel administration (P < 0.00001and P = 0.042, respectively). The platelet aggregation in carriers of at least one CYP2C19 loss-of-function allele (*2 or *3, accounted for 58% of the study population) was obviously higher than that in non-carriers (P < 0.00001). Patients with the CYP2C19*2 allele had a higher risk of HPR than those with the CYP2C19 wild-type genotype [adjusted hazard ratio (HR), 1.56; 95% confidence interval(CI), 1.04–2.33, P = 0.03]. The carriers of at least one CYP2C19 loss-of-function allele could also predict significantly greater risk of HPR compared with non-carriers (adjusted HR1.79,95% CI: 1.33–2.4,P = 0.003). However, the carriage of CYP2C19*3 alone could not predict the risk of HPR significantly (adjusted HR, 1.5; 95% CI: 0.83–3, P = 0.16). Significant relation of CYP2C19*17, PON1Q129R and ABCB1C3435T to the platelet aggregation was not found.

Conclusion

In clopidogrel treated Chinese patients with ACS, carriers of at least one CYP2C19 loss-of-function allele could predict greater risk of HPR, with the impact mainly attributing to CYP2C19*2. Neither ABCB1 nor PON1 genotype could influence the antiplatelet response of clopidogrel in the cohort of Chinese patients.     

用血栓弹力图评价阿司匹林及氯吡格雷在缺血性卒中患者中血小板抑制效应的研究

目的用血栓弹力图评价缺血性卒中患者正规使用阿司匹林及氯吡格雷后血小板抑制率的变化。方法血栓弹力图检测我院123例住院患者抗血小板药物治疗后花生四烯酸(AA)通路和ADP受体途径诱导的血小板抑制率,患者抗血小板药物治疗包括阿司匹林组(n=7)、氯吡格雷组(n=8)、阿司匹林+氯吡格联合组(n=108)。结果 123例患者中,阿司匹林组AA诱导的血小板抑率为(87.04±22.71)%,氯吡格雷组ADP诱导的血小板抑制率平均值为(46.61±24.43)%,阿司匹林+氯吡格雷组AA和ADP诱导的血小板抑制率为分别(77.87±27.98)%和(50.23±29.27)%。服用阿司匹林和氯吡格雷的患者分别有115和116例,其AA和ADP途径血小板抑制率分别为(78.42±27.69)%;(49.99±28.88)%,差异具有显著统计学意义(P=0.000)。其中对阿司匹林和氯吡格雷敏感者(血小板抑制率≥50%)分别为97例(84.34%)和89例(75.72%),而不敏感者(血小板抑制率<50%)分别为18例(15.65%)和27例(23.28%),两种药物疗效间差异无显著统计学意义(χ2=3.706,P=0.054)。结论服用100mg/d阿司匹林,在绝大多数缺血性脑血管病患者中能产生较强的血小板抑制效应,而服用75mg/d氯吡格雷对血小板抑制稍弱,但多数患者仍能达有效的血小板抑制作用。     

The effect of antiplatelet drugs clopidogrel and aspirin is less immediately after stent implantation

Introduction

A decreased effect of clopidogrel or aspirin on platelets corresponds to an increased risk of major adverse coronary events. The aim was to investigate if the inhibition of platelet function by clopidogrel and aspirin is equal at two different time points: immediately after percutaneous coronary intervention (PCI) and one day thereafter.

Materials and methods

Platelet function was assessed by the Vasodilator Stimulated Phosphoprotein (VASP) phosphorylation assay, Impedance Aggregometry, Platelet Function Analyzer and the Cone and Platelet Analyzer in 30 patients on chronic treatment with clopidogrel and aspirin.

Results

Inhibition of platelets by clopidogrel and aspirin was less post PCI than one day after PCI as measured with the VASP assay and aggregometry: the platelet reactivity index, the adenosine diphosphate/prostaglandin and the arachidonic acid -induced platelet aggregation were 23% (p = 0.009), 75% (p = 0.001) and 127% (p < 0.001) higher post PCI than one day after PCI, respectively. The collagen/adenosine diphosphate closure time was 30% higher after PCI compared to one day thereafter (p = 0.047), which could in part be due to a two-fold increase in von Willebrand factor-ristocetin cofactor activity one day after PCI (p = 0.001).

Conclusion

Inhibition of platelets by clopidogrel and aspirin was less immediately post PCI as compared to one day thereafter. This indicates that the time point of platelet function testing is important for the determination of cut-off points and the definition of nonresponsiveness to antiplatelet drugs.     

Impact of clopidogrel resistance on thrombotic events after percutaneous coronary intervention with drug-eluting stent

Objectives

This study examines whether patient resistance to clopidogrel is associated with long-term thrombotic events after elective coronary drug-eluting stent (DES) implantation.

Methods

We prospectively enrolled 386 patients with stable angina who received elective percutaneous coronary intervention (PCI) with DES. Before the procedure, platelet reactivity was measured by light transmittance aggregometry (LTA) at baseline and approximately 24 h after the 300 mg loading dose of clopidogrel. Clopidogrel resistance was conservatively defined as ≤ 10% absolute difference between baseline and post-treatment platelet aggregation. All patients received chronic dual antiplatelet treatment (aspirin 300 mg and clopidogrel 75 mg daily) for 12 months. Patients were followed for 1 year after coronary stenting for the occurrence of composite thrombotic events, including cardiovascular death, non-fatal myocardial infarction (MI), stent thrombosis or cerebrovascular ischemic accident (CVA).

Results

Clopidogrel resistance was present in 65 patients (16.8%). During follow-up, composite thrombotic events occurred in 16.9% of clopidogrel resistant patients, yet in only 6.2% of non-resistant patients (p = 0.010). The incidence of definite or probable stent thrombosis was 9.2% in clopidogrel resistant patients and 2.5% in non-resistant patients (p = 0.018). After adjustment for other factors that affect cardiovascular outcome, clopidogrel resistance, diabetes, and left ventricular (LV) dysfunction were independently associated with 1-year composite thrombotic events. The hazard ratio (HR) for clopidogrel resistance was 2.44 (95% CI = 1.09 to 5.45; p = 0.031).

Conclusion

This study demonstrates the natural history of clopidogrel resistance among patients with stable cardiovascular disease, and shows that this resistance is an independent predictor of thrombotic events in patients undergoing PCI with DES.     

Measurement of the platelet retention rate in a column of collagen-coated beads is useful for the assessment of efficacy of antiplatelet therapy

Introduction

A simple, validated method to measure platelet function is unavailable for bedside use. Measurement of platelet retention rate using a column of collagen-coated beads and whole blood is a new, simple assay that reflects platelet aggregation. This study was aimed to examine the utility of this assay to assess efficacy of antiplatelet drug therapy.

Methods

Citrated whole blood (1.5 ml) in a syringe was passed through a polyvinyl tube packed with collagen-coated beads for 40 seconds using a syringe pump. Platelet retention rate in the column was calculated from platelet counts in blood before and after passage. An increase in the retention rate reflects an increase in platelet activity. This new platelet retention assay and the traditional optical aggregometry assay were performed in 331 patients with stable coronary artery disease (CAD).

Results

The retention rate was significantly reduced in patients taking dual antiplatelet therapy (aspirin plus clopidogrel or ticlopidine) compared with aspirin alone. There was a significant linear correlation between the platelet retention rate and platelet aggregability measured by the traditional method (r = 0.44, p < 0.001). In multivariate Cox proportional hazards analysis, higher platelet retention rate was an independent predictor of future cardiovascular events in patients on dual antiplatelet therapy (hazard ratio 3.9, 95% CI 1.6 to 9.5, p = 0.003).

Conclusions

Measurement of the platelet retention rate in a column of collagen-coated beads may be useful for monitoring the efficacy of antiplatelet drug therapy in patients with CAD.     

Comparison of VerifyNow P2Y12 and thrombelastography for assessing clopidogrel response in stroke patients in China

Poor response to clopidogrel is often associated with recurrent ischemic events, and reliable platelet function tests are needed to identify clopidogrel low response (CLR). The aim of the study was to compare the consistency of VerifyNow P2Y12 and thrombelastography (TEG) in acute ischemic stroke patients treated with clopidogrel. Patients hospitalized in Changhai Hospital from August 2012 to September 2013 and assigned to treatment with a daily 75-mg dose of clopidogrel. The blood samples were taken on the 5–7th day to assess the capability of VerifyNow P2Y12 and TEG for evaluation of clopidogrel response, and all instrument parameters were used to perform correlation analysis. Patients with CLR were detected by using the methods and criteria published earlier (PRU ≥ 230 assayed by VerifyNow P2Y12 or TEG-Inhib% ≤30 % measured by TEG). Totally 58 patients were enrolled for the study and there were wide varieties in parameters of VerifyNow P2Y12 and TEG. Results showed a total of 17 and 9 patients, respectively, identified as CLR assessed by VerifyNow P2Y12 and TEG, but only three patients were detected to be clopidogrel low responders with both tests. The kappa consistency analysis showed poor consistency between VerifyNow P2Y12 and TEG results in terms of CLR (Kappa = ?0.0349, p = 0.7730). Linear regression also demonstrated poor correlation between VerifyNow-PRU/VerifyNow-Inhib% and TEG-Inhib% (p = 0.07901 and p = 0.3788, respectively). Our study demonstrated that there was poor correlation between VerifyNow P2Y12 and TEG results, and VerifyNow P2Y12 showed a larger proportion of CLR than TEG.     

Influence of renal function and platelet turnover on the antiplatelet effect of aspirin

Introduction

Kidney disease predisposes to cardiovascular events. This study investigated the influence of renal function and platelet turnover on the antiplatelet effect of aspirin in patients with coronary artery disease.

Materials and Methods

We included 124 aspirin-treated patients with coronary artery disease and normal to moderately reduced renal function. All tests were performed one hour after aspirin ingestion. Renal function was assessed using creatinine, estimated glomerular filtration rate (eGFR), and cystatin C. The antiplatelet effect of aspirin was evaluated using the VerifyNow® Aspirin assay and multiple electrode aggregometry (MEA, Multiplate®) induced by collagen (1.0 μg/mL) and arachidonic acid (1.0 mmol/L). Von Willebrand factor was measured as a marker of endothelial dysfunction. Platelet turnover was evaluated by measurements of immature, reticulated platelets.

Results

Renal function did not influence the antiplatelet effect of aspirin evaluated by MEA (r = − 0.2-0.09, p = 0.03-0.77) or the VerifyNow® (r = − 0.12-0.11, all p-values > 0.1). In contrast, renal function correlated inversely with von Willebrand factor levels (r_creatinine = 0.48, p < 0.0001; r_eGFR = − 0.46, p < 0.001; r_{cystatin C} = 0.54, p < 0.0001). The number of immature platelets correlated with platelet aggregation according to MEA (r = 0.20-0.39, all p-values < 0.03), but not according to VerifyNow® (r = − 0.07, p = 0.50).

Conclusions

A reduced antiplatelet effect of aspirin may be explained by an increased number of immature platelets. Moderately impaired renal function was associated with high levels of von Willebrand factor, but not with a reduced antiplatelet effect of aspirin.     

Plasma and Whole Blood Clot Strength Measured by Thrombelastography in Patients Treated with Clopidogrel during Acute Coronary Syndromes

Introduction

Treatment with clopidogrel, a selective platelet P₂Y₁₂ receptor antagonist, reduces risk of recurrent ischemic events in patients with acute coronary syndrome (ACS), by limiting platelet aggregation and activation. Stable whole blood clot formation requires activation of platelets, generation of fibrin and final fibrin crosslinks. In this study we intended to compare plasma and whole blood thrombelastography (TEG) measurements in patients during ACS.

Materials and Methods

Whole blood and plasma samples from 32 patients with non-ST segment elevation myocardial infarction (NSTEMI) were collected after administration of clopidogrel. Whole blood and plasma fibrin clot strength (MA) were determined by TEG. Platelet aggregation was determined by light transmittance aggregometry (LTA) using adenosine 5'-diphosphate (ADP), thrombin receptor activation peptide (TRAP), or collagen as agonists. Fibrinogen and C-reactive protein (CRP) concentrations were measured by ELISA.

Results

Heightened plasma fibrin clot strength was associated with increased platelet reactivity stimulated by ADP (ρ = 0.536; p = 0.002), TRAP (ρ = 0.481; p = 0.007), and collagen (ρ = 0.538; p = 0.01). In contrast to plasma fibrin MA, whole blood MA did not correlate with platelet aggregation. Platelet count was the primary contributor to the difference in thrombin induced whole blood MA and plasma fibrin MA. Increasing levels of CRP were associated with increased plasma fibrin clot strength and platelet reactivity.

Conclusions

Our data suggest that inflammation is associated with increased plasma fibrin clot strength and lower platelet inhibition by clopidogrel during ACS. Platelet count is a main contributor to additional contractile force of whole blood TEG as compared to plasma TEG during treatment with clopidogrel.     

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

Background

Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy.

Patients and methods

Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting.

Results

Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p = 0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR.

Conclusion

Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.     

Dual Antiplatelet Therapy Beyond 90 days in Symptomatic Intracranial Stenosis in the SAMMPRIS Trial

BackgroundThe safety and efficacy of dual antiplatelet use for symptomatic intracranial atherosclerosis beyond 90 days is unknown. Data from SAMMPRIS was used to determine if dual antiplatelet therapy (DAPT) beyond 90 days impacted the risk of ischemic stroke and hemorrhage.MethodsThis post hoc exploratory analysis from SAMMPRIS included patients who did not have a primary endpoint within 90 days after enrollment (n = 397). Patients in both the aggressive medical management (AMM) and percutaneous transluminal angioplasty and stenting (PTAS) arms were included. Baseline features and outcomes during follow-up were compared between patients who remained on DAPT beyond 90 days (on clopidogrel) and patients who discontinued clopidogrel and remained on aspirin alone at 90 days (off clopidogrel) using Fisher's exact tests.ResultsThe stroke rate was numerically lower in the group on clopidogrel vs off clopidogrel among both the AMM alone arm (6.0% versus 10.8%, p = 0.31) and the PTAS arm (8.7% versus 9.8%; p = 0.82), but the difference was not significant. The major hemorrhage rates were numerically higher in the group on clopidogrel vs. off clopidogrel group among both the AMM alone arm (4.0% versus 2.5%; p = 0.67) and the PTAS arm (10.9% versus 3.5%; p = 0.08), but were not significant.ConclusionThis exploratory analysis suggests that prolonged DAPT use may lower the risk of stroke in medically treated patients with intracranial stenosis but may increase the risk of major hemorrhage.     

个体化抗血小板治疗对缺血性卒中二级预防的效果研究

目的 研究个体化抗血小板治疗在缺血性卒中二级预防的效果。 方法 选择2013年3月-2014年5月于陕西省人民医院就诊的急性缺血性卒中患者207例,随机分为 常规治疗组与个体化治疗组。常规治疗组应用阿司匹林100 mg/d抗血小板治疗。个体化治疗组应用 Essen卒中风险评分量表（Essen Stroke Risk Score,ESRS）将高危组给予氯吡格雷75 mg/d,低危组给 予阿司匹林100 mg/d抗血小板治疗。7 d后进行血栓弹力图（thromboela stogram,TEG）及CYP2C19基因型 检测,结合TEG及CYP2C19基因型结果,决定抗血小板治疗方案。随访1年,比较个体化治疗组和常规 治疗组患者终点事件发生率。 结果 CYP2C19快代谢基因型、中间代谢基因型患者应用氯吡格雷的血小板抑制率明显高于慢代谢 型,结果差异有显著性（P =0.018,P =0.015）。个体化治疗组（112例）和常规治疗组组（95例）终点事 件发生率差异无显著性（P＞0.01）。 结论 CYP2C19快代谢基因型、中间代谢基因型患者应用氯吡格雷的血小板抑制率明显高于慢代谢 型。与阿司匹林常规治疗方案相比,利用CYP2C19基因多态性与TEG检测指导下的个体化抗血小板方 案未显示降低缺血性卒中后终点事件发生率,可能需要更大规模、随访时间更长的研究。     

Multi-parameter assessment of platelet inhibition and its stability during aspirin and clopidogrel therapy

Introduction

Poor response to antiplatelet drugs is associated with adverse outcomes. We assessed platelet inhibition and its stability and tested correlation and agreement between platelet function assays.

Methods

Peripheral blood from 58 patients on both aspirin and clopidogrel who underwent percutaneous coronary intervention (PCI) was collected at hospital discharge (visit-1) and at 30-90 days (visit-2). Platelet function was measured using light transmission aggregometry (LTA-AA and LTA-ADP), VerifyNow® (Aspirin; ARU and P2Y12; PRU), ex vivo TxB₂, urinary 11dhTxB₂, and VASP (PRI) assays. Data were analyzed as continuous, quartiles and binary. Patients were defined as aspirin poor responder (PR) with ARU ≥ 550, LTA-AA maximum ≥ 20%, TxB₂ ≥ 1 ng/mL or 11dhTxB₂ ≥ 1,500 pg/mg of creatinine and as clopidogrel PR with PRU ≥ 240, PRU ≥ 208, LTA-ADP maximum ≥ 40%, PRI ≥ 50%, or PRI ≥ 66%.

Results

Aspirin PR was 3-33% and clopidogrel PR was 10-35% in visit-1. LTA-AA, 11dhTxB_2, and all clopidogrel-response measures showed correlation and agreement between visit-1 and visit-2. The highest agreement between two visits was revealed by PRU ≥ 240 and PRI ≥ 66% (PRU-κ = 0.7, 95% CI = 0.47, 0.93; PRI-κ = 0.69, 95% CI = 0.42, 0.95, p-values < 0.001). Comparison of platelet function assays in a single visit (visit-1) revealed a poor correlation between LTA-AA and 11dhTxB₂ assays and no agreement among aspirin-response assays. The highest correlation and agreement were obtained between VerifyNow® P2Y12 and VASP assays (rho = 0.7, p-value < 0.001 and PRU ≥ 208-PRI-κ = 0.41-0.42, 95% CI = 0.13, 0.69, p-values < 0.001).

Conclusions

Platelet inhibition is stable during aspirin and clopidogrel treatment. Clopidogrel-response assays correlate and agree with each other better than aspirin-response assays.     

Comparison of turbidimetric aggregation and in vitro bleeding time (PFA-100) for monitoring the platelet inhibitory profile of antiplatelet agents in patients undergoing stent implantation

The present study compared classical ADP-induced platelet aggregation vs. PFA-100 closure times using collagen/ADP membrane cartridges to monitor the degree of platelet-inhibiting effect of three drug regimens: ticlopidin, abciximab/ticlopidin and loading dose clopidogrel, each on top of aspirin (acetylsalicylic acid, ASA) during and after elective stent placement (intervention) in a total of 31 patients with acute coronary syndrome. Ticlopidin was started directly after stent implantation, abciximab was started before coronary intervention and given intravenously for 12 h, and a clopidogrel loading dose was given before intervention. The 10 patients treated with ticlopidin (500 mg daily) showed no significant prolongation of PFA closure times and a slight increase of ADP-induced platelet aggregation shortly after intervention. In 11 patients treated with abciximab/ticlopidin, the PFA closure times were significantly prolonged, and ADP-induced platelet aggregation was reduced by more than 80% during the 12-h abciximab infusion after intervention. The 10 patients pretreated with loading dose clopidogrel (450 mg followed by 75 mg daily) showed an intermediate but significant prolongation of PFA closure times and reduction of ADP-induced platelet aggregation at levels between the ticlopidin/aspirin- and the abciximab/ticlopidin/aspirin-treated groups. At 20 h after intervention, a similar degree of PFA closure time prolongation and inhibition of ADP-induced aggregation was observed in the abciximab/ticlopidin/aspirin- and the clopidogrel/aspirin-treated patient groups. Both measurement of PFA-100 closure times and inhibition of ADP-induced platelet aggregation showed a similar degree of platelet inhibition, but had rather broad SD ranges, which limit their precision for the follow-up of individual patients. In conclusion, abciximab on top of ticlopidin/aspirin showed a stronger antiplatelet effect for only less than 20 h, as compared to loading dose clopidogrel/aspirin in acute coronary syndrome patients undergoing stent implantation. Whether such a short-term superiority of abciximab, as compared to loading dose clopidogrel, translates into an overall clinical benefit of thombotic and bleeding complications remains to be established in a randomized clinical trial.