Stroke and aspirin non-responder patients: relation with hypertension and platelet response to adenosine diphosphate

Factors associated with clopidogrel resistance and clinical outcomes in ischemic cerebrovascular disease: A retrospective study

OBJECTIVE

Clopidogrel resistance may lead to the recurrence of cerebrovascular diseases. We aimed to identify potential factors associated with clopidogrel resistance and evaluate the clinical outcomes of the patients.

MATERIALS AND METHODS

In this retrospective study, patients with ischemic cerebrovascular disease treated with clopidogrel were included and classified into 2 groups according to the adenosine diphosphate (ADP)-induced platelet aggregation. Patients with the ADP inhibition rate of <30 % were included in clopidogrel resistance group, otherwise were included in clopidogrel sensitive group. CYP2C19 genotype and other clinical data were analyzed to identify factors and clinical features in the multivariate analysis. The outcomes were vascular events in 6 months.

RESULTS

In total, 139 patients were enrolled with 81 (58.27 %) in clopidogrel sensitive group and 58 (41.73 %) in clopidogrel resistance group. Female and CYP2C19 *2*3 carrying were risk factors for clopidogrel resistance, and female was an independent risk factor (OR 2.481, 95 % CI 1.066-5.771, P=0.035). The clopidogrel resistance group showed a higher use rate of argatroban (P=0.030) and a lower arachidonic acid-induced inhibition of platelet aggregation (P=0.036). Clopidogrel resistance was related to the progressing stroke (HR 3.521, 95 % CI 1.352-9.170, P=0.010), but had no influence on the bleeding events (P>0.05).

CONCLUSIONS

The risk of clopidogrel resistance increased significantly in female patients. Patients with clopidogrel resistance may have an increased incidence of stroke progression in the acute phase.

Association among PlA1/A2 gene polymorphism, laboratory aspirin resistance and clinical outcomes in patients with coronary artery disease: An updated meta-analysis

The aim of this study was to investigate the association among the PlA1/A2 gene polymorphism, laboratory aspirin resistance and adverse clinical outcomes in coronary artery disease (CAD) patients who were on aspirin maintainance therapy. A comprehensive literature search was performed and 35 eligible clinical trials including 19025 CAD patients were recruited. Adverse clinical outcomes involving all-cause death, non-fatal myocardial infarction (MI), ischemic stroke and target vessel revascularization (TVR) were analyzed. The definition of aspirin resistance in each study was accepted. Meta-analysis was performed using the Review Manager 5.3.5 System. In CAD patients, the PlA2 gene carriers had similar incidence of laboratory aspirin resistance compared to those with PlA1/A1 genotype [29.7% vs 28.3%, OR = 0.94 (95% CI 0.63 to 1.40, P = 0.74)], and there were no significant differences in the adverse clinical outcomes between the PlA2 carriers and the PlA1/A1 genotype patients. However, the laboratory aspirin non-responders had higher risks of death [7.9% vs. 2.5%, OR = 2.42 (95% CI 1.86 to 3.15, P < 0.00001)] and TVR [4.5% vs. 1.7%, OR = 2.20 (95% CI 1.19 to 4.08, P = 0.01)] compared to the responders. In aspirin-treated CAD patients, the laboratory aspirin resistance predicts all-cause death and TVR. However, the PlA1/A2 gene polymorphism predicts neither the laboratory aspirin response nor the clinical outcomes.

Antiplatelet treatment in essential hypertension: where do we stand?

Antiplatelet agents represent a cornerstone in the management of patients at increased cardiovascular risk. Essential hypertension is considered a major public health problem leading to increased cardiovascular morbidity and mortality. The majority of patients with essential hypertension exhibit also additional cardiovascular risk factors and present with increased platelet activation. Despite recent innovations in the field of antiplatelet treatment and the introduction of novel agents, the role of antiplatelet treatment in patients with essential hypertension remains understudied. This review aims to shed light on novel experimental and clinical data in the evolving field of antiplatelet treatment in essential hypertension. In particular, recent data regarding aspirin, clopidogrel, novel P2Y12 inhibitors, and other agents with potential antiplatelet effects are critically reviewed.

The PlA1/A2 polymorphism of glycoprotein IIIa in relation to efficacy of antiplatelet drugs: a systematic review and meta-analysis

AIM

The PlA1/A2 polymorphism of glycoprotein IIIa (GPIIIa) has been associated with both antiplatelet drug resistance and increased cardiovascular events. The aim of this study was to conduct the first meta-analysis investigating the association between carriage of the PlA2 allele and resistance to currently licensed antiplatelet drugs.

METHODS

Electronic databases (MEDLINE and EMBASE) were searched for all articles evaluating genetic polymorphisms of GPIIIa. For studies where antiplatelet resistance was measured using validated techniques, pooled odds ratios (ORs) were calculated using fixed effects and random effects models.

RESULTS

Sixteen studies were eligible for statistical analysis and included 1650 PlA1 homozygous subjects and 668 carriers of the PlA2 allele. For carriers of the PlA2 allele, OR 0.924 (n = 2318; 95% CI 0.743, 1.151; P = 0.481) was observed for resistance to any antiplatelet drug, OR 0.862 (n = 2085; 95% CI 0.685, 1.086; P = 0.208) for resistance to aspirin and OR 1.429 (n = 233; 95% CI 0.791, 2.582; P = 0.237) for resistance to clopidogrel. In the aspirin cohort, sub-group analysis revealed no statistical association in either healthy subjects or those with cardiovascular disease. PlA2 carriage was marginally associated with aspirin sensitivity using the fixed effects model when identified by the PFA-100 assay (n = 1151; OR 0.743, 95% CI 0.558, 0.989; P = 0.041) but with significant heterogeneity (I(2) = 55%; P = 0.002). Significance was lost with analysis using a random effects model.

CONCLUSIONS

The totality of published data does not support an association between carriage of the PlA2 allele and antiplatelet drug resistance. Significant heterogeneity indicates the need for larger studies using validated and standardized assays.

ASPIRIN RESISTANCE CANDIDATE GENES AND THEIR ASSOCIATION WITH THE RISK OF CARDIOVASCULAR EVENTS

The review presents the current literature evidence on the most likely genetic polymorphisms of aspirin resistance, such as polymorphisms of cyclooxygenase, glycoproteins GP Ib/IIIa, GP Ibα, GP VI, and adenosine diphosphate receptors P2Y1 and P2Y12. The authors discuss the prevalence of these polymorphisms in laboratory and clinical aspirin resistance, as well as their association with the risk of cardiovascular events during aspirin treatment. 

Genetic determinants of platelet reactivity during acetylsalicylic acid therapy in diabetic patients: evaluation of 27 polymorphisms within candidate genes

AIMS

Decreased platelet responsiveness to acetylsalicylic acid (ASA) reported previously in diabetic patients could be attributed to patient-based, clinical, genetic and cellular factors. The objective of the present study was to investigate the effect of the genomic polymorphism on the platelet reactivity in diabetic patients treated with ASA.

METHODS AND RESULTS

The study cohort consisted of 295 Caucasians with diabetes type 2 who had been taking ASA tablets at the dose of 75 mg per day for at least 3 months for primary or secondary prevention of myocardial infarction (MI). Platelet reactivity analyzes were performed using VerifyNow ASA and PFA-100 assays. Genotyping for the selected 27 single nucleotide polymorphisms (SNPs) within 19 genes was performed using a Sequenom iPLEX platform. The results indicate that the statistically significant differences in platelet reactivity were observed in the PFA-100 assay for SNPs in following genes: TXBA2R (rs1131882), ADRA2A (rs4311994), PLA2G7 (rs7756935) and 9p21.3 (rs10120688) (P = 0.02, P = 0.03, P = 0.02, P = 0.03, respectively, all significance levels corrected for multiple comparisons). When using the VerifyNow ASA test, a weak nominal statistical significance (i.e. before multiple comparison testing) was observed for two SNPs in the GPVI gene: rs1671152 and rs1613662 [P = 0.025 (0.5) for both SNPs, corrected for multiple comparisons test].

CONCLUSIONS

The results from the present study suggest that the four analyzed genes may contribute to platelet reactivity measured with the PFA-100 assay in the diabetic population treated with ASA.

Incomplete inhibition of platelet function as assessed by the platelet function analyzer (PFA-100) identifies a subset of cardiovascular patients with high residual platelet response while on aspirin

Sixty-six patients with a history of ischemic events (myocardial infarction, unstable angina, or stroke) on chronic aspirin therapy were studied by different platelet function tests: 37 patients had suffered a recurrent event while on aspirin and 29 were without recurrences. Based on results from light transmission aggregometry (LTA) induced by arachidonic acid (AA) and serum TxB(2) both COX-1-dependent methods, only one patient could be identified as aspirin "resistant". However, when methods only partially-dependent on platelet COX-1 activity were considered, the prevalence of aspirin non-responders ranged, according to the different tests, from 0 to 52%. No difference was observed between patients with recurrences and those without. Among patients with recurrent events, those with an incomplete inhibition of platelet function, as assessed by the PFA-100, had significantly higher residual serum TxB(2) (2.4 ± 2.4 ng/mL vs 0.4 ± 0.1 ng/mL, p = 0.03), residual LTA-AA (9.2 ± 10.6% vs 2.0 ± 1.6%, p = 0.008), LTA-Coll (49.3 ± 14.6% vs 10.2 ± 8.3%, p = 0.007) and LTA-ADP (50.9 ± 16.2% vs 34.3 ± 11.0%, p = 0.04). In conclusion, laboratory tests solely exploring the AA-mediated pathway of platelet function, while being the most appropriate to detect the effect of aspirin on its pharmacologic target (platelet COX-1), may fail to reveal the functional interactions between minimal residual TxA(2) and additional stimuli or primers potentially leading to aspirin-insensitive platelet aggregation. High residual platelet response in platelet function tests only partially dependent on COX-1 may reveal a condition of persistent platelet reactivity in a subset of aspirin-treated patients characterizing them as a subgroup at higher vascular risk.

Platelet function testing in clinical diagnostics

Although the utility of platelet function testing is still under debate, the necessity to inhibit platelets in patients suffering from cardiovascular and cerebrovascular disease is undoubted and well proven. The wide variety of available platelet function tests often using different methodologies, the apparent lack of standardization, and finally the emerging evidence on the clinical value of platelet function testing are resulting in a considerable uncertainty in the clinical practice, how to deal with the issue of platelet function testing. Platelet function testing might not only yield clinical benefits for the patients but also economical advantages by identifying the right drug at the right dose for the right patient. This article intends to provide an overview of the current platelet function tests such as light transmittance aggregometry, whole blood impedance aggregometry, the PFA-1001 system, the VerifyNow2 system, flow cytometry, as well as other promising technologies like Plateletworks3, IMPACT-R4, PADA, thromboelastography, and the mean platelet component (MPC), briefly addressing strengths, weaknesses and clinical utility of these tests.