血小板的反应变异性在氯吡格雷抵抗中的研究进展

氯吡格雷抵抗是指血小板对氯吡格雷呈低反应或无反应,目前报道的影响氯吡格雷的因素很多,现就血小板在对氯吡格雷反应过程中的变异与氯吡格雷抵抗的关系,如二磷酸腺苷受体P2Y12的变异、细胞色素P450同工酶系统变异、血小板表面高α-2肾上腺素受体等因素做一综述。     

氯吡格雷抵抗研究进展

氯吡格雷广泛用于急性冠脉综合征和经皮冠状动脉介入术的患者,可以减少心血管事件的发生,降低支架内亚急性血栓形成的发生率。但是临床上服用氯吡格雷的患者表现出各自不同的反应性,部分患者反应差甚至无反应,称之为氯吡格雷抵抗。本文就氯吡咯雷抵抗的定义、检测方法、机制及临床意义作一综述。     

氯吡格雷抵抗研究进展

氯吡格雷的抗血小板聚集作用在急性冠脉综合征和经皮冠状动脉介入术患者中得到广泛应用,但氯吡格雷抵抗的出现影响了其临床疗效。现就氯吡格雷抵抗的定义、临床意义、血小板聚集检测方法、发生机制及防治策略分别加以阐述。     

氯吡格雷抵抗临床防治的研究进展

<正>阿司匹林联合氯吡格雷双联抗血小板治疗已经成为防治急性冠状动脉综合征(ACS)的基石。现已明确,双联抗血小板治疗能够有效抑制PCI术后患者支架内血栓的形成[1]。然而,尽管接受规范的双联抗血小板治疗,部分患者仍会出现反复的缺血事件[2-4]。氯吡格雷抵抗是导致患者抗血小板治疗不达标的重要原因之一。氯吡格雷抵抗的发生机制尚不明确,目前证实与相关基因多态性、药物相互作用、患者依从性、糖耐量异常、肥胖等因素相关[5-8]。近来,人们对氯吡     

氯吡格雷抵抗研究进展

氯吡格雷已确立对急性冠脉综合征患者从急性期到长期的保护作用。但氯吡格雷抗血小板作用并不能使所有患者受益。部分患者对氯吡格雷的心血管保护作用存在氯吡格雷抵抗现象，即应用氯吡格雷的患者仍会发生心血管血栓事件。     

氯吡格雷抵抗的研究进展

随着抗血小板治疗成为心血管治疗的基石,抗血小板药物氯吡格雷的使用及氯吡格雷抵抗（CR）现象的发生就愈发引起人们的关注。CR被认为是导致支架内血栓及再发缺血事件的罪魁祸首,并且增加了围手术期的发病率和死亡率。因为目前对于CR没有明确的定义,所以临床的管理仍然是个挑战。新的抗血小板制剂及易感人群中基因多态性的探测将有利于规范临床CR患者的治疗。关于抵抗的概况、发生率、发生机制及抵抗患者特定的临床治疗方案等,本文将进行阐述。     

氯吡格雷抵抗的研究进展

<正>氯吡格雷可以有效地抑制血小板的活化和聚集,其与血小板表面P2Y12受体不可逆结合,从而阻断二磷酸腺苷(adenosine diphosphate,ADP)诱导的血小板聚集。氯吡格雷联合阿司匹林这一治疗策略,现已广泛应用于急性冠状动脉综合征(acute coronary syndrome,ACS)和经皮冠状动脉介入治疗术(percutaneous coronary intervention,PCI)患者的     

半负荷量氯吡格雷反应对氯吡格雷抵抗的预测价值

目的探讨半负荷量氯吡格雷反应能否预测氯吡格雷抵抗。方法急性冠脉综合征(ACS)患者138例,于服用氯吡格雷150 mg前、服药后12～18 h内及第4天,采血检测10和20μmol/L二磷酸腺苷(ADP)诱导的血小板聚集率。结果分别以10和20μmol/LADP为诱导剂时,半负荷量之后的血小板聚集值不能预测氯吡格雷抵抗(P>0.05);半负荷量之后的血小板聚集降低值小于0.5ohms以及半负荷量之后血小板聚集降低的百分率小于12.22%和16.03%可预测氯吡格雷抵抗(P<0.001)。结论服用半负荷量氯吡格雷150 mg后12～18 h内的血小板聚集值不能预测氯吡格雷抵抗现象;而此值与用药前血小板聚集值的差值以及降低的百分率均可在一定程度上预测氯吡格雷抵抗现象。     

氯吡格雷抵抗的研究进展

氯吡格雷通过拮抗血小板腺苷二磷酸(ADP)受体P2Y12,在急性冠状动脉综合征治疗中发挥重要作用,但部分患者存在药物抵抗现象。目前尚无特异性检测指标和统一定义,多以基础状态和服药后ADP诱导血小板聚集率差值≤10％作为抵抗标准;此现象发生率尚不明确,与临床血栓形成关系仅有小样本试验证实;机制方面国内外学者提出遗传因素、药物相互作用、基础疾病及胰岛素抵抗等多项可能,治疗方面目前尚无特效方法。     

氯吡格雷抵抗的研究进展

氯吡格雷是临床上广泛使用的抗血小板药物,但在长期随访中发现,应用氯吡格雷治疗的患者仍有血栓性血管事件的发生,即存在抵抗现象。目前,氯吡格雷抵抗的检测方法有ADP诱导的光学法血小板聚集,血小板激活标志物检测,以及血栓弹力图等多种方法。氯吡格雷抵抗的发生机制有不恰当的用药剂量,药物间的相互作用,遗传因素等多方面的原因。     

Options to overcome clopidogrel response variability

Oral antiplatelet agents targeting the platelet P2Y12 receptor are an integral component of treating patients with acute coronary syndrome and those undergoing percutaneous coronary intervention. Clopidogrel has been the most commonly used agent in this respect worldwide. However, there are certain shortcomings of clopdiogrel, the most important of which is the wide response variability of platelet inhibition. The response to clopidogrel is affected by various clinical variables, genetic variations involved in its activation, and drug-drug interactions. Therefore, clinicians are faced with challenges in situations where high inhibition of platelets is necessary and in cases where the response to clopidogrel may be suboptimal. There are various ways of overcoming the response variability and this review will focus on the practical methods available. Namely, the data and evidence regarding increasing the dose of clopidogrel, adding cilostazol to standard dual antiplatelet therapy, and switching to more recently developed agents will be covered.     

The inter-individual variability of the response to clopidogrel

Clopidogrel is an anti-platelet aggregation drug with proven efficacy in the prevention of atherothrombotic complications. However, according to studies, between 5 and 20% of patients have further thrombotic episodes despite treatment with clopidogrel. The principal ex vivo evaluation methods of clopidogrel's efficacy are platelet aggregometry, and using flow cytometry to measure platelet activation and the quantatitive analysis of VASP phosphorylation. VASP analysis is the most selective method for clopidogrel's effect. These tests show great inter-individual variability in the response to treatment. This variability is such that about a third of treated patients show an "insufficient" response to clopidogrel. The exact causes of this variability have not yet been clearly identified. They could correspond with observer error, inter-individual variability in intestinal absorption or hepatic metabolism, or polymorphism of clopidogrel's target, the P2Y12 receptor. Accordingly it may be necessary to adapt the dose of clopidogrel or to use an alternative treatment. Failure to respond to clopidogrel would be a risk factor for atherothrombotic complications, but this association has yet to be demonstrated.     

Aspirin and clopidogrel response variability: review of the published literature

Antiplatelet resistance has been proposed as a possible mechanism to explain recurrent cardiovascular events in patients who have coronary artery disease and who are undergoing dual antiplatelet therapy. A comprehensive search on PubMed was conducted for literature that was printed in the English language between January 1996 and November 2007 on aspirin and clopidogrel resistance. Significant traits for aspirin hyporesponsiveness were female sex, older age, and lower levels of hemoglobin. Diabetes mellitus and elevated body mass index showed trends toward a higher incidence of resistance in some aspirin trials but did not reach statistical significance. Clopidogrel studies suggested that patients with type-2 diabetes mellitus are more likely to manifest inadequate response to the medication. Although 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors were initially suspected to decrease response to clopidogrel, later studies refuted this possibility. Patients with a suboptimal response to aspirin or clopidogrel seem to be at increased risk of recurrent cardiovascular events. Large clinical trials with standardized laboratory methods and well-defined protocols are needed to determine whether common features exist in patients with suspected hyporesponsiveness to antiplatelet therapy, and to validate the clinical relevance of response variability. A concise nonarbitrary definition of physiologic "resistance" is needed, and investigators should identify patients as having a variable response to antiplatelet therapy.     

Inter-individual variability in response to clopidogrel in patients with coronary artery disease

BACKGROUND: Clopidogrel, especially when combined with aspirin, reduces the rate of ischaemic events in patients with coronary artery disease (CAD). There are scare data in literature on the inter-individual variability in response to clopidogrel. AIM: To assess the incidence of clopidogrel resistance using rapid whole blood platelet function assessment, and to examine the possibility of early identification of non-responders. METHODS: In 31 consecutive patients with stable angina treated with aspirin, the degree of platelet aggregation inhibition (DPAI) in the whole blood was assessed at baseline and 3, 6, 12 as well as 24 hours after administration of loading dose of clopidogrel (300 mg). Response to clopidogrel was measured by calculating the absolute difference between the baseline DPAI and DPAI obtained at the investigated time-points (DPAI). RESULTS: After 24 hours from clopidogrel administration, seven (22.6%) patients were identified as non-responders (DPAI < or =10%). Demographic and clinical variables as well as baseline DPAI were similar in responders and non-responders (DPAI: 5.8+/-3.7% vs 7.1+/-5.3%, p=NS). Out of the patients who were found to be resistant to clopidogrel at the six-hour time-point, 87.5% remained resistant to this agent 24 hours after drug administration. DPAI calculated at the 24-hour time-point highly correlated with the six-hour DPAI (r=0.74). No differences in the rate of ischaemic or bleeding complications between responders and non-responders were noted. CONCLUSIONS: The assessment of the degree of platelet aggregation inhibition allows early (six hours from the initiation of treatment) identification of patients who are resistant to clopidogrel. The method of the rapid whole blood platelet function assessment is feasible in every-day clinical practice.     

对氯吡格雷低反应患者换用替格瑞洛后的有效性与安全性评价

目的 探索对氯吡格雷低反应的急性冠状动脉综合征（ACS）患者换用替格瑞洛时,起始使用负荷剂量与无负荷剂量两种方案的有效性与安全性的比较.方法 前瞻性入选154例对氯吡格雷低反应拟换用替格瑞洛的患者,由主诊医师自行决定替格瑞洛是否使用负荷剂量（负荷剂量组180mg负荷量,随后90 mg每日两次维持;非负荷剂量组直接用90 mg每日两次维持）.主要终点事件为腺昔二磷酸（ADP）诱导的血小板聚集率变化情况.次要终点事件包括心源性死亡、心肌梗死、卒中事件发生率、呼吸困难、出血、尿酸变化等不良事件发生率.结果 负荷剂量组由氯吡格雷转换为替格瑞洛3d后,血小板聚集率明显低于非负荷剂量组（17.6±7.2比25.7±18.3,P=0.008）,但30 d后两组血小板聚集率差异无统计学意义.换用替格瑞洛后,两组患者均未发生心源性死亡和脑卒中事件.无负荷剂量组发生心肌梗死事件2例,分别在术后3d（转换为替格瑞洛后2d）和90d;负荷剂量组无心肌梗死事件.无负荷剂量组呼吸困难的发生率明显低于负荷剂量组（12.2％比19.4％,P=0.001）;两组的出血事件发生率差异无统计学意义.结论 与不使用负荷剂量相比,氯吡格雷低反应的患者转换为替格瑞洛时应用负荷剂量后早期血小板抑制作用更显著,且不增加出血事件,但呼吸困难发生率也更高.     

High clopidogrel loading dose during coronary stenting: effects on drug response and interindividual variability.

AIM: To assess platelet inhibitory effects, interindividual variability in platelet inhibition as well as response to a 600 mg, compared to a standard 300 mg, clopidogrel loading dose (LD) after coronary stenting METHODS AND RESULTS: Platelet function profiles were assessed in 50 patients undergoing coronary stenting receiving either a 300 mg (n=27) or 600 mg clopidogrel LD. ADP (6 microM) and collagen (6 microg/mL) induced platelet aggregation, as well as ADP (2 microM) induced glycoprotein (GP) IIb/IIIa activation and P-selectin expression were assessed at baseline and 4, 24, and 48 h following clopidogrel front-loading. A more intense and rapid inhibition of platelet activation (both GP IIb/IIIa activation and P-selectin expression) were achieved using a 600 mg, compared to a 300 mg, LD throughout the entire 48 hours (p<0.001). Although there were no differences in platelet aggregation, overall a 600 mg LD increased the number of clopidogrel responders and this was also achieved earlier compared to a 300 mg LD. A 600 mg LD did not reduce interindividual variability of platelet response. CONCLUSION: The use of a 600 mg clopidogrel LD in patients undergoing coronary stenting optimises platelet inhibitory effects early after intervention and may provide a more effective protection against early thrombotic complications.     

Platelet response to aspirin and clopidogrel. Biochemical evaluation, clinical impact, and pharmacological modulation

In the vasculature, platelets contribute to thrombotic and inflammatory responses, key processes in atherothrombosis. During percutaneous coronary interventions, several studies have emphasized the deleterious impact of enhanced platelet aggregation on early clinical outcome. However, despite the significant interest of determining platelet responsiveness appears worth, the clinically accurate and practical platelet function assay is still not widespread available. Furthermore, standardized definitions of platelet "low-responders" are still lacking. Up to now, light transmission platelet aggregometry remains the "gold-standard". Platelets "points of care" assays might overcome the limitations of conventional optical platelet aggregation but need further validation in clinical settings. The most recent ACC/AHA guideline endorses a strategy of platelet monitoring in the highest risk patients (IIb C). In "low-responders" patients, clopidogrel dose escalation was demonstrated to improve platelet responsiveness. Others potential pharmacological solutions could include the switch for another thienopyridine. Indeed, prasugrel a P2Y12 receptor inhibitor was demonstrated to provide higher levels of inhibition of ADP-induced platelet aggregation.     

Clinical importance of aspirin and clopidogrel resistance

Aspirin and clopidogrel are important components of medical therapy for patients with acute coronary syndromes, for those who received coronary artery stents and in the secondary prevention of ischaemic stroke. Despite their use, a significant number of patients experience recurrent adverse ischaemic events. Interindividual variability of platelet aggregation in response to these antiplatelet agents may be an explanation for some of these recurrent events, and small trials have linked "aspirin and/or clopidogrel resistance", as measured by platelet function tests, to adverse events. We systematically reviewed all available evidence on the prevalence of aspirin/clopidogrel resistance, their possible risk factors and their association with clinical outcomes. We also identified articles showing possible treatments. After analyzing the data on different laboratory methods, we found that aspirin/clopidogrel resistance seems to be associated with poor clinical outcomes and there is currently no standardized or widely accepted definition of clopidogrel resistance. Therefore, we conclude that specific treatment recommendations are not established for patients who exhibit high platelet reactivity during aspirin/clopidogrel therapy or who have poor platelet inhibition by clopidogrel.