全血电阻法检测血小板聚集程度对抗血小板治疗效果的评价

目的研究全血电阻法检测血小板聚集程度对抗血小板治疗效果的评价。方法比较全血电阻法和经典的血浆光学法测定血小板聚集程度的重复性。采用全血电阻法，分别以二磷酸腺苷（ADP）、花生四烯酸和胶原为诱导剂，检测30名健康志愿者和60例服用血小板聚集抑制剂的患者的血小板聚集程度。采用Kappa分析比较全血电阻法和经典的血浆光学法检测血小板聚集程度的一致性。结果全血电阻法的平均CV值为4．8％，优于血浆光学法（CV值为7．7％）。采用全血电阻法，分别以ADP、花生四烯酸和胶原为诱导剂，健康志愿者的平均聚集程度分别为（9．6±3．4）Ω、（10．4±2．8）Ω和（13．5±2．2）Ω。服用阿司匹林（100mg／d）的患者，以花生四烯酸为诱导剂，95％的患者血小板聚集程度为0Ω。服用血小板聚集抑制剂患者的血小板聚集程度显著低于健康志愿者（ADP为诱导剂，t=2．391，P〈0．05；花生四烯酸为诱导剂，t=4．057，P〈0．01；胶原为诱导剂t=2．047，P〈0．05）。同时服用阿司匹林和氯吡格雷两种抑制剂的患者的血小板聚集程度显著低于单独服用阿司匹林的患者（t=3．646，P〈0．01）。另外，以花生四烯酸为诱导剂，阿司匹林抵抗的患者的血小板聚集开始时间，有比健康志愿者延长的特点。经Kappa分析，表明全血电阻法和经典的血浆光学法两种方法检测患者对阿司匹林（Kappa=1）和氯吡格雷（Kappa=0．67）两种血小板聚集抑制剂的效果的一致性良好。结论采用全血电阻法和多种诱导剂测定血小板聚集能力对帮助临床判断抗血小板治疗的效果，辅助个体化用药是很有意义的。     

阿司匹林抵抗与尿11-脱氢-血栓素B2的检测及相关性研究

目的 探讨心脑血管病患者发生阿司匹林抵抗（aspirinresistance，AR）的影响因素以及AR与尿11-脱氢-血栓素B2（11-dehydro-Thromboxane，11-d-TXB2）的相关性。方法 220例心脑血管病患者服用阿司匹林（100mg／d）至少7d以上，用二磷酸腺苷和花生四烯酸作诱导剂测定血小板聚集功能，找出AR患者，测定11-d-TXB：的含量。结果 女性易发生AR，高血压患者发生AR几率高，AR者的11-d-TXB2含量同阿司匹林敏感者相比差异有统计学意义（P〈0．01）。结论 正确认识阿司匹林抵抗现象，对AR患者，可加大阿司匹林用量或换用其他抗血小板药物。     

脑梗死患者同型半胱氨酸水平与血小板聚集功能关系探讨

目的探讨脑梗死患者同型半胱氨酸水平（Homocysteine,HCY）与血小板聚集功能之间的关系。方法检测117例脑梗死患者及91名健康体检者的HCY及以二磷酸腺苷（ADP）和花生四烯酸（AA）为诱导剂的血小板聚集功能,进行统计对比分析。结果脑梗死组的HCY水平和血小板聚集功能与对照组比较有显著差异（P〈0．05）高HCY患者组的血小板聚集功能与正常HCY患者组比较有显著差异（P〈0．05）。结论HCY水平增高可引起血小板聚集功能增强,是脑梗死再发高危险因素。     

心脑血管疾病患者心率变异性与阿司匹林抵抗的研究

目的阿司匹林抵抗患者心率变异性指标的变化。方法服用阿司匹林（100 mg/d）至少7天以上的心脑血管患者作为入选标准。二磷酸腺苷（adenosine disphosphate,ADP）和花生四烯酸（arachidonic acid,AA）作诱导剂在Chrono-log 560 Ca上测定血小板聚集功能。记录受检者24小时动态心电图。结果阿司匹林抵抗发生率为12.5%（n=21）。阿司匹林抵抗组HRV时域参数和频域参数与阿司匹林敏感组比较均有统计学意义（P〈0.01）。阿司匹林抵抗组高血压患者的比率（42.9%）与阿司匹林敏感组（29.3%）比较有显著差别（P=0.01）。结论阿司匹林抵抗组HRV时域参数和频域参数与阿司匹林敏感组比较均有统计学意义,这提示我们HRV下降的患者服用阿司匹林时,要定期检测血小板聚集功能,一旦发生阿司匹林抵抗,应提示这类患者要及时调整抗血小板药物,加大阿司匹林的剂量或换用其他抗血小板药物。     

社区动脉粥样硬化高危人群中阿司匹林抵抗调查

目的：调查社区动脉粥样硬化高危人群中阿司匹林抵抗（AR）或半抵抗（ASR）的发生率及其流行病学特征,并探讨其与动脉粥样硬化危险因素的相关性.方法：筛选200例动脉粥样硬化高危患者服用阿司匹林（100 mg/d）至少7 d以上,用二磷酸腺苷（ADP）和花生四烯酸（AA）作诱导剂测定其前后血小板聚集功能变化及血清血栓烷B2（TXB2）水平测定.结果：200例动脉粥样硬化高危人群中AR发生率为4.5%,ASR者占20.7%.血清TXB2水平,AA、ADP诱导的血小板聚集率与健康对照组相比差异有显著性（P〈0.01）;血清TXB2水平与血小板聚集率有较好的相关性（r=0.871）.结论：社区动脉粥样硬化高危人群服用阿司匹林后部分患者产生AR或ASR;检测AA、ADP诱导的血小板聚集率,血清TXB2水平可作为动脉粥样硬化高危人群发生AR或ASR的评价指标.     

不同剂量阿斯匹林抑制血小板聚集功能时效探讨

目的探讨阿斯匹林常用剂量下，血小板聚集率的变化规律及诱导剂的选择。方法３０名经体检健康的自愿者，随机分为３组。第一组一次服用２００ｍｇ阿斯匹林，第二组初服１００ｍｇ阿斯匹林后每日５０ｍｇ追加量，连服７天。第三组口服５０ｍｇ阿斯匹林。各组分别在不同时间进行采样，样本用花生四烯酸、瑞斯托霉素、胶原、二磷酸腺苷（ＡＤＰ）四种诱导剂进行血小板聚集实验。结果第一组停药第７天，血小板聚集率恢复到服药前水平。花生四烯酸诱导的血小板聚集实验对口服阿斯匹林最为敏感。第二组，血小板聚集率在服药的７天及停药后９天内与用药前差异有非常显著意义（Ｐ＜００１），在第１０天差异有显著意义（Ｐ＜００５），第１１天恢复至服药前水平。以上两组，花生四烯酸诱导的血小板聚集率的变化比其他诱导剂诱导的变化明显。第三组３天内血小板功能仍受明显抑制。结论首服剂量越大，维持服药的时间越长，血小板聚集功能恢复所需时间越长。花生四烯酸诱导的血小板聚集实验是监测阿斯匹林剂量比较理想的实验     

冠心病患者发生阿司匹林抵抗的有关研究

目的探讨冠心病患者发生阿司匹林抵抗的概率以及相关影响因素方法79名冠心病患者服用阿司匹林（100mg/d）7天以上，分别用ADP和从作诱导剂，检测血小板聚集功能。结果用光学法（广为使用的方法）测定血小板聚集功能，阿司匹林抵抗发生率为11．4％（n=9）。阿司匹林抵抗组高血压患者的比率（44．4％）与阿司匹林敏感组（25．0％）比较有显著差别（P=0．01）。结论对服用阿司匹林的患者要检测其血小板聚集功能。高血压患者易发生阿司匹林抵抗，这提示这类患者要调整抗血小板药物，加大阿司匹林的剂量或换用其他抗血小板药物。     

化学诱导剂对血小板钙离子浓度变化的影响

目的探讨化学诱导剂作用下不同人群血小板钙离子浓度的变化。方法（1）以不同浓度的ADP、凝血酶、胶原、花生四烯酸、5-HT激活血小板，用流式细胞仪观察20例正常健康人血小板钙离子浓度变化。（2）用ADP、胶原、花生四烯酸、5-HT激活血小板，用流式细胞仪观察心肌梗死患者及高血压患者（各20例）血小板钙离子浓度的变化。（3）用花生四烯酸激活血小板，用流式细胞仪观察20例心肌梗死患者口服阿司匹林前后血小板钙离子浓度的变化。结果（1）ADP、瑞斯托酶素、胶原、花生四烯酸、5-HT血小板激活剂均可导致血小板钙离子浓度升高（P〈0．05），而且在一定范围内，钙离子浓度的升高幅度随激活剂的浓度升高而增加。没有观察到凝血酶导致血小板钙离子浓度升高。（2）同样激活剂刺激下，心肌梗死患者和高血压患者血小板钙离子浓度升高的幅度均高于正常健康人（P〈0．05）。（3）服用阿司匹林后心肌梗死患者血小板钙离子浓度下降的幅度低于正常健康人（P〈0．05）。结论化学诱导剂对血小板的激活过程与钙离子浓度的变化密切相关；心肌梗死、高血压患者可能存在血小板钙通道活性增高；钙离子能反应服用阿司匹林后血小板的功能状态，检测血小板钙离子对阿司匹林的疗效监测有一定的价值．     

中国北方地区汉族人群血小板膜糖蛋白Ⅰbα VNTR多态性的分布与脑梗死患者CC基因型与阿司匹林敏感相关性分析

目的研究中国北方地区汉族人群血小板膜糖蛋白(GP)Ⅰbα数目可变串联重复(VNTR)多态性与阿司匹林抵抗(AR)的关系。方法用聚合酶链反应限制性片段长度多态性(PCR-RFLP)检测300例健康人及110脑梗死患者基因型。脑梗死患者服用阿司匹林(100mg/d)至少7d以上,用二磷酸腺苷(ADP)和花生四烯酸(AA)作诱导剂测定血小板聚集功能。结果中国北方地区汉族人群中只检测出GPⅠbα三种等位基因B、C、D,没有发现A基因型。阿司匹林敏感(AS)患者CC基因型比阿司匹林半抵抗(ASR)患者更多见。结论中国东北地区仅检测出B、C、D三种基因型。GPⅠb VNTR多态性CC基因型的出现对于低剂量阿司匹林抗血小板作用更为敏感。     

冠心病患者同型半胱氨酸水平与血小板聚集功能的相关性探讨

目的探讨冠心病患者同型半胱氨酸（Homocysteine,HCY）水平与血小板聚集功能之间的关系。方法检测112例冠心病患者及91名健康体检者的HCY水平及以二磷酸腺苷（ADP）和花生四烯酸（AA）为诱导剂的血小板聚集功能,进行统计对比分析。结果冠心病组的HCY水平、血小板聚集功能与对照组比较有显著差异（P〈0．05）;高HCY患者组的血小板聚集功能与正常HCY患者组比较有显著差异（P〈0．05）。结论HCY水平增高可引起血小板聚集功能增强,是冠心病反复发作的高危因素。     

Dual antiplatelet therapy unmasks distinct platelet reactivity in patients with coronary artery disease

Summary. Background: Platelet‐induced thrombosis is a major risk factor for recurrent ischemic events, although platelet function in patients with cardiovascular disease taking aspirin and clopidogrel is very poorly characterized. The aim of this study was to assess platelet reactivity in patients with cardiovascular disease taking aspirin and clopidogrel. Methods: We developed a rapid assay to measure platelet aggregation in response to arachidonic acid, collagen, adenosine diphosphate (ADP), epinephrine and thrombin receptor activating peptide (TRAP) in 80 healthy volunteers. We then recruited 200 consecutive patients from outpatient clinics and the cardiac catheterization laboratory and tested platelet function. Platelet aggregation induced by epinephrine is a marker of global platelet reactivity. We tested platelet function in 146 patients compliant with antiplatelet therapy. Platelet aggregation to epinephrine was divided into quartiles. The platelet response to the other agonists was analysed based on the response to epinephrine. Results: Platelet reactivity increased significantly across the quartiles in response to epinephrine in healthy volunteers and patients (P < 0.0001). A significant increase in response across quartiles was seen with all agonists in healthy volunteers (P < 0.001). In contrast, a significant increase in response across quartiles was only seen with ADP in patients (P < 0.0001). Hypertension, smoking and diabetes were significantly associated with increasing platelet reactivity to epinephrine (P < 0.05). Conclusion: This study shows that platelet response differs between healthy volunteers and patients on dual antiplatelet therapy. In patients with cardiovascular disease, dual antiplatelet therapy unmasks a distinct type of platelet reactivity in response to epinephrine and ADP but not other agonists.     

Clopidogrel discontinuation and platelet reactivity following coronary stenting

See also Lordkipanidzé M, Harrison P. Beware of being caught on the rebound. This issue, pp 21–3. Summary. Aims: Antiplatelet therapy with aspirin and clopidogrel is recommended for 1 year after drug‐eluting stent (DES) implantation or myocardial infarction. However, the discontinuation of antiplatelet therapy has become an important issue as recent studies have suggested a clustering of ischemic events within 90 days of clopidogrel withdrawal. The objective of this investigation was to explore the hypothesis that there is a transient ‘rebound’ increase in platelet reactivity within 3 months of clopidogrel discontinuation. Methods and Results: In this prospective study, platelet function was assessed in patients taking aspirin and clopidogrel for at least 1 year following DES implantation. Platelet aggregation was measured using a modification of light transmission aggregometry in response to multiple concentrations of adenosine diphosphate (ADP), epinephrine, arachidonic acid, thrombin receptor activating peptide and collagen. Clopidogrel was stopped and platelet function was reassessed 1 week, 1 month and 3 months later. Thirty‐two patients on dual antiplatelet therapy were recruited. Discontinuation of clopidogrel increased platelet aggregation to all agonists, except arachidonic acid. Platelet aggregation in response to ADP (2.5, 5, 10, and 20 μm ) and epinephrine (5 and 20 μm ) was significantly increased at 1 month compared with 3 months following clopidogrel withdrawal. Thus, a transient period of increased platelet reactivity to both ADP and epinephrine was observed 1 month after clopidogrel discontinuation. Conclusions: This study demonstrates a transient increase in platelet reactivity 1 month after clopidogrel withdrawal. This phenomenon may, in part, explain the known clustering of thrombotic events observed after clopidogrel discontinuation. This observation requires confirmation in larger populations.     

Clinical and preclinical pharmacology of KC-764, a novel antiplatelet agent]

Preclinical pharmacological studies showed that KC-764 was more potent and more selective in inhibiting platelet aggregation than aspirin. The concentration of KC-764 for inhibiting PGI2 production in the aorta was 70 times higher than that for inhibiting TXA2 in platelets. Antiplatelet action of KC-764 was augmented by plasma components. This augmentation by plasma may lead to selective antiplatelet activity. KC-764 has been investigated for platelet function in patients with chronic cerebral infarction. KC-764 at 10, 20 and 40 mg b i d, inhibited platelet aggregation induced by arachidonic acid, collagen, and ADP, and its potency was almost equal to aspirin at 100-330 mg daily. Plasma TXB2 levels were markedly depressed by KC-764 but plasma 6-keto-PGF1 alpha levels were not influenced. On the contrary, aspirin depressed both plasma prostanoids. These findings suggest that KC-764 can overcome the 'aspirin dilemma'.     

Hydrogen peroxide triggers activation of human platelets selectively exposed to nonaggregating concentrations of arachidonic acid and collagen.

The effects of H2O2 on platelet function were investigated in vitro and ex vivo. H2O2 (0.5 to 5 mumol/L) alone did not influence platelet function, but when it was combined with subthreshold concentrations of arachidonic acid or collagen, it induced platelet aggregation and serotonin release in a dose-dependent fashion. The increase in platelet aggregation was associated with thromboxane A2 production and was prevented by 100 mumol/L aspirin. The amplification of platelet response by H2O2 was also inhibited 2 hours after 300 mg aspirin was given to healthy subjects. H2O2 alone did not affect intraplatelet Ca++ influx or mobilization but, combined with subthreshold concentrations of arachidonic acid, it increased Ca++ mobilization. In platelets prelabeled with tritiated arachidonic acid, H2O2 induced tritium release in a dose-dependent fashion; this effect was prevented by mepacrine, an inhibitor of the phospholipase A2 enzyme. Platelet function was not affected by using H2O2 in combination with other agonists such as thrombin, calcium ionophore, or adenosine diphosphate. This study suggests that H2O2 triggers activation of platelets preexposed to agonists at subthreshold levels by stimulating arachidonic acid metabolism, likely by stimulating the phospholipase A2 enzyme. The stimulation of platelets by concentrations of H2O2 similar to those released by activated leukocytes may give new insights into the functional cooperation between leukocytes and platelets.     

阿司匹林对脑梗死患者C反应蛋白及血小板的影响

目的研究阿司匹林（ASP）对脑梗死患者血清C反应蛋白（CRP）水平及血小板功能的影响。方法将70例脑梗死患者随机分为2组：Ⅰ组口服ASP 150 mg.d-1,Ⅱ组口服ASP 300 mg.d-1,8周后检测2组患者的血浆CRP水平和血小板聚集率。结果2组CRP、血小板聚集率与治疗前相比差异有统计学意义（P〈0.05）;2组治疗后CRP、血小板聚集率比较差异有统计学意义（P〈0.05）。结论ASP能显著降低脑梗死患者血清CRP水平以及血小板聚集率,从而降低脑梗塞的风险,较大剂量的ASP可能有更好的二级预防作用。     

Enhanced antiplatelet effect of clopidogrel in patients whose platelets are least inhibited by aspirin: a randomized crossover trial

Summary. Objective: We aimed to determine whether adding clopidogrel to aspirin in patients at high risk of future cardiovascular events would suppress laboratory measures of the antiplatelet effects of aspirin; and have greater platelet inhibitory effects in patients with the least inhibition of platelets by aspirin. Methods: We performed a randomized, double‐blind, placebo‐controlled, crossover trial, comparing clopidogrel 75 mg day^?1 versus placebo, in 36 aspirin‐treated patients with symptomatic objectively confirmed peripheral arterial disease. Results: The addition of clopidogrel to aspirin did not suppress platelet aggregation induced by arachidonic acid, urinary 11 dehydro thromboxane B₂ concentrations, or soluble markers of platelet activation markers (P‐selectin, CD40‐ligand) and inflammation (high sensitivity serum C‐reactive protein, interleukin‐6). Clopidogrel significantly inhibited platelet aggregation induced by ADP (reduction 26.2%; 95% CI: 21.3–31.1%, P < 0.0001) and collagen (reduction 6.2%; 95% CI: 3.2–9.3%, P = 0.0003). The greatest inhibition of collagen‐induced platelet aggregation by clopidogrel was seen in patients with the least inhibition of arachidonic acid induced aggregation by aspirin [lower tertile of arachidonic acid‐induced platelet aggregation: 2.8% (95% CI: ?0.8 to 6.3%) reduction in mean collagen‐induced aggregation by clopidogrel; middle tertile: 4.0% (95% CI: 0.4–7.6%); upper tertile 12.6% (95% CI: 4.5–20.8%); P‐value for interaction 0.01]. Conclusions: The greatest platelet inhibitory effect of clopidogrel occurs in patients with the least inhibition of arachidonic acid‐induced platelet aggregation by aspirin. This raises the possibility that the clinical benefits of adding clopidogrel to aspirin may be greatest in patients whose platelets are least inhibited by aspirin. Confirmation in clinical outcome studies may allow these patients to be targeted with antiplatelet drugs that inhibit the ADP receptor, thereby overcoming the problem of laboratory aspirin resistance.     

河南汉族人群血小板膜糖蛋白IaC_(807)T基因多态性及其对血小板聚集功能的影响

目的:探讨河南汉族人群血小板膜糖蛋白(GP)IaC807T基因多态性及其对血小板聚集功能的影响。方法:120例河南汉族脑梗死患者为缺血组,113例健康体检者为对照组,PCR-RELP法检测2组GPIaC807T基因多态性,体外胶原诱导法检测2组血小板聚集功能。结果:河南汉族人群GPIa基因第807位存在2种等位基因(C和T)和3种基因型(C/C、C/T、T/T);缺血组T807等位基因频率高于对照组(P0.05);GPIaT等位基因携带者较C等位基因携带者体外胶原诱导下血小板达30%聚集前的延迟期缩短(P0.05);缺血组T基因携带者血小板达30%聚集率前的延迟期较对照组缩短(P0.05);血小板最大聚集率差异无统计学意义。结论:血小板膜GPI-aT807等位基因可能是河南汉族脑梗死患者的遗传危险因素,作用机制可能与血小板聚集功能的迅速启动有关。     

Platelet activation, myocardial ischemic events and postoperative non-response to aspirin in patients undergoing major vascular surgery

OBJECTIVES: Myocardial ischemia is the leading cause of postoperative mortality and morbidity in patients undergoing major vascular surgery. Platelets have been implicated in the pathogenesis of acute thrombotic events. We hypothesized that platelet activity is increased following major vascular surgery and that this may predispose patients to myocardial ischemia. METHODS: Platelet function in 136 patients undergoing elective surgery for subcritical limb ischemia or infrarenal abdominal aortic aneurysm repair was assessed by P-selectin expression and fibrinogen binding with and without adenosine diphosphate (ADP) stimulation, and aggregation mediated by thrombin receptor-activating peptide and arachidonic acid (AA). Cardiac troponin-I (cTnI) was performed. RESULTS: P-selectin expression increased from days 1 to 3 after surgery [median increase from baseline on day 3: 53% (range: -28% to 212%, P < 0.01) for unstimulated and 12% (range: -9% to 45%, P < 0.01) for stimulated]. Fibrinogen binding increased in the immediate postoperative period [median increase from baseline: 34% (range: -46% to 155%, P < 0.05)] and decreased on postoperative day 3 (P < 0.05). ADP-stimulated fibrinogen binding increased on day1 (P < 0.05) and thereafter decreased. Platelet aggregation increased on days 1-5 (P < 0.05). Twenty-eight (21%) patients had a postoperative elevation (> 0.1 ng mL(-1)) of cTnI. They had significantly increased AA-stimulated platelet aggregation in the immediate postoperative period and on day 2 (P < 0.05), and non-response to aspirin (48% vs. 26%, P = 0.036). CONCLUSIONS: This study has shown increased platelet activity and the existence of non-response to aspirin following major vascular surgery. Patients with elevated postoperative cTnI had significantly increased AA-mediated platelet aggregation and a higher incidence of non-response to aspirin compared with patients who did not.