Comparison of platelet P2Y(12) ADP receptor-mediated pathway inhibition in triple versus dual antiplatelet therapy as assessed by VASP-phosphorylation in Japanese patients undergoing coronary stenting

Despite wide interindividual variability in response to clopidogrel, platelet P2Y(12) ADP receptor inhibition in Japanese patients has not been fully studied using specific methodology. This study compared platelet P2Y(12) ADP receptor inhibition during treatment with clopidogrel versus clopidogrel plus cilostazol in patients undergoing coronary stenting. Forty-two patients in whom platelet function was measured within 2 months after coronary stenting were enrolled. All patients were treated with aspirin 100 or 200 mg/day, and were divided into a dual therapy group (aspirin plus clopidogrel 75 mg/day; n = 34) and a triple therapy group (aspirin plus clopidogrel 75 mg/day plus cilostazol 200 mg/day; n = 8). Vasodilator-stimulated phosphoprotein (VASP) phosphorylation analysis and 5 and 20 μmol/L-induced maximal platelet aggregation were assessed. No differences were found in baseline characteristics except for a higher incidence of diabetes mellitus (DM) in the triple therapy group. Although there were no differences in platelet aggregation between the 2 groups, VASP index was significantly lower in the triple therapy group than in the dual therapy group (23.1 ± 15.3% versus 51.2 ± 19.9%; P = 0.001). The rate of low responsiveness to clopidogrel, defined by VASP index > 50%, was lower in the triple therapy group than in the dual therapy group (12.5% versus 55.9%; P = 0.047). Similarly, in DM patients the triple therapy group had a lower VASP index compared with the dual therapy group (23.1 ± 15.3% versus 47.0 ± 23.5%; P = 0.015).Clopidogrel plus cilostazol is more effective in inhibiting the platelet P2Y(12) ADP receptor pathway than clopidogrel alone. This may be useful for reducing clopidogrel resistance in Japanese patients.     

抗血小板治疗预防冠脉支架术后再狭窄的Meta分析

目的:就冠状动脉(冠脉)支架术后有关西洛他唑、氯吡格雷、阿司匹林三联抗血小板治疗对血小板活化和聚集功能及支架内再狭窄的影响相关文献进行系统评价。方法:计算机检索国内外公开发表的有关西洛他唑,氯吡格雷,阿司匹林对血小板聚集率、冠脉支架术后再狭窄率影响的临床随机对照试验文献,按一定标准筛选文献后进行质量评价,共纳入5篇随机对照研究文献。以Cochrane协作网的软件RevMan v5.0进行处理,主要以血小板聚集抑制率,最小管腔直径(MLD),晚期管腔丢失,再狭窄率为评价指标,进行Meta分析。结果:在以二磷酸腺苷(ADP)为诱导剂的血小板聚集抑制率方面,实验组与对照组之间差异无显著意义,在最小血管直径,晚期血管丢失,再狭窄率方面,试验组与对照组之间的差异存在显著意义。结论:三联(西洛他唑+氯吡格雷+阿司匹林)抗血小板药物治疗与常规两联(氯吡格雷+阿司匹林)治疗组相比能更有效地抑制冠脉支架术后的再狭窄,但其疗效和安全性还需要大规模临床试验的证实。     

冠状动脉支架术后三联抗血小板药物治疗对血小板功能的影响

目的探讨三联抗血小板药物治疗对冠状动脉(冠脉)支架术后患者血小板活化和聚集功能的影响。方法120例冠心病行冠脉支架植入术患者,随机分为三联组(阿司匹林、氯吡格雷和西洛他唑)和两联组(阿司匹林和氯吡格雷),三联组于术后第1天起加服西洛他唑。两组分别于术后第1天服用西洛他唑前及第5天测定血小板活化复合物(PAC-1)和CD_(62)p,同时测定5μmol/L及20μmol/L ADP诱导的血小板最大聚集率(MPAR)。结果两组临床基线资料及CD_(62)p、PAC-1和MPAR基线值差异均无统计学意义。分别计算各指标第二次测定值与基线值的差值,两组ΔMPAR差异无统计学意义,但三联组和两联组ΔCD_(62)p和ΔPAC-1分别为[(5.12±11.25)%比(1.08±4.97)%,P＜0.05]和[(12.12±12.30)%比(2.22±15.15)%,P＜0.01]。对急性冠脉综合征(ACS)患者亚组分析结果表明三联组ΔMPAR(5μmol/L)[(8.68±10.35)％比(2.92±13.06)%,P=0.018]、ΔMPAR(20μmol/L)[(11.05±11.14)%比(5.16±13.27)%,P=0.019]、ΔCD_(62)p[(5.57±12.08)％比(1.35±4.42)%,P=0.028】和ΔPAC-1[(11.62±12.73)%比(1.29±15.73)%,P= 0.001]均显著高于两联组。3个月临床随访显示三联组与两联组主要不良心、脑血管事件发生率分别为0和3.3%(2/60),出血发生率分别为5%(3/60)和3.3%(2/60),均无统计学意义。结论三联抗血小板药物治疗与常规两联治疗相比能更有效地抑制冠脉支架术后血小板活化和聚集,但其疗效和安全性还需大规模临床试验证实。     

Cilostazol could ameliorate platelet responsiveness to clopidogrel in patients undergoing primary percutaneous coronary intervention.

BACKGROUND: Cilostazol increases the cyclic adenosine monophosphate levels in platelets and might ameliorate the antiplatelet activity of clopidogrel. This study investigated the additional effect of cilostazol on platelet aggregation measured by a VerifyNow analyzer and soluble CD40 ligand (sCD40L) as a marker of activated platelet in patients undergoing primary percutaneous coronary intervention (PCI). METHODS AND RESULTS: Sixty cases of primary PCI were randomly assigned to dual (aspirin and clopidogrel) or triple (dual plus cilostazol) therapy. The antiplatelet effects of aspirin and clopidogrel were evaluated by VerifyNow tests. The plasma sCD40L levels at admission, 24 h and 21 days were measured by the ELISA method. The arachidonic acid induced platelet aggregation was similar in both groups. However, the triple group had a significantly lower P2Y12 reaction unit (dual 208.8+/-69.0 vs triple 168.2+/-79.2, p=0.041) and higher % inhibition of adenosine diphosphate (ADP)-induced platelet aggregation (dual 23.8+/-21.4% vs triple 40.5+/-21.0%, p=0.004). In the multivariate analysis, cilostazol was a negative predictor for low responders to clopidogrel (95% confidence interval 0.067-0.711). The plasma sCD40L levels were not significantly different between the 2 groups at the same point of time. CONCLUSIONS: The addition of cilostazol to the combination of aspirin plus clopidogrel significantly increases the inhibition of ADP-induced platelet aggregation. However, there was no additive effect on aspirin-induced antiplatelet activity or lowering of sCD40L.     

Effect of atorvastatin and pravastatin on platelet inhibition by aspirin and clopidogrel treatment in patients with coronary stent thrombosis

We sought to determine a potential interaction between statins and antiplatelet therapy with aspirin and clopidogrel. Previous laboratory studies have shown a possible drug-drug interaction of statins metabolized by cytochrome P450 3A4 and clopidogrel (prodrug metabolized by cytochrome P450 3A4), resulting in an impaired inhibitory effect of clopidogrel on platelet aggregation. However, conclusive prospective data assessing this potentially relevant interaction are lacking. In 73 patients, 23 with previous coronary stent thrombosis (ST) (ST group) and 50 without coronary ST (control group), platelet aggregation was measured 3 times in monthly intervals using light transmission aggregometry (adenosine diphosphate [ADP] and arachidonic acid induction). Measurements were carried out with aspirin monotherapy (100 mg/day), dual antiplatelet therapy with aspirin plus clopidogrel (75 mg/day), and additional treatment of 20 mg/day of atorvastatin or 40 mg/day of pravastatin. ADP (5 and 20 micromol)-induced platelet aggregation was significantly decreased with clopidogrel (p <0.001) but remained stable under additional treatment with atorvastatin or pravastatin in the 2 groups. Patients with previous ST showed a higher ADP-induced aggregation level than control subjects. This difference was not influenced by clopidogrel or statin treatment. In conclusion, patients with previous ST show a higher aggregation level than control subjects independent of statin treatment. Atorvastatin and pravastatin do not interfere with the antiaggregatory effect of aspirin and clopidogrel. In conclusion, drug-drug interaction between dual antiplatelet therapy and atorvastatin or pravastatin seems not to be associated with ST.     

Loading effect of 200 mg cilostazol on platelet inhibition in patients undergoing percutaneous coronary intervention

To date, most studies conducted on cilostazol have examined its effects as an agent of maintenance-dose therapy, but its loading effects on platelet inhibition have never been reported. This study aimed to determine the loading effects of 200 mg cilostazol in addition to aspirin and clopidogrel on platelet inhibition in patients undergoing percutaneous coronary intervention.Sixty consecutive patients undergoing coronary intervention were enrolled and assigned to receive 300 mg of aspirin and clopidogrel with or without 200 mg of cilostazol. All loading doses were given at least 3 hours before percutaneous coronary intervention and followed by dual or triple maintenance-dose therapy. Platelet function tests were performed just before and at 24 hours and 30 days after percutaneous coronary intervention by light transmittance aggregometry and VerifyNow? P2Y12 assay.There were no significant differences in baseline or angiographic characteristics between the 2 groups. The results of platelet function tests revealed that the adjunctive loading dose of 200 mg of cilostazol induced more potent platelet inhibition compared to a dual regimen at each time point. Cilostazol reduced the incidence of high post-treatment platelet reactivity (HPPR).Adjunctive 200 mg cilostazol can improve platelet responsiveness to clopidogrel in the pre- and postprocedural phases, reducing the prevalence of HPPR.     

强化抗血小板治疗对冠状动脉支架术后血小板高反应性的影响

目的 探讨强化抗血小板治疗对急性冠状动脉综合征患者冠状动脉支架术后血小板高反应性(HPR)的影响.方法 2009年3月至2011年2月在3家医院连续入选3316例置入药物洗脱支架的急性冠状动脉综合征患者,其中840例(25.3％)患者诊断为HPR.HPR定义为氯吡格雷300 mg和阿司匹林300 mg治疗24h后,20 μmol/L二磷酸腺苷诱导的血小板聚集率＞55％.HPR患者按1:2的比例随机接受标准抗血小板治疗(标准组,n=280)及强化抗血小板治疗(强化组,n=560).标准组患者服用阿司匹林300 mg/d和氯吡格雷75 mg/d.强化组患者服用阿司匹林300 mg/d和双倍剂量氯吡格雷(150 mg/d),3d后如 HPR 未改善则加用西洛他唑(50～100 mg,每天2次).观察患者的HPR改善率及发生的临床事件.结果 强化组患者治疗3d后HRP改善率为54.3％(304/560);256例HRP未改善的患者接受西洛他唑治疗3d后,强化组的HRP改善率为81.1％(454/560).术后30 d,强化组HPR改善率显著高于标准组(69.9％比55.7％,P=0.000).两组患者均未发生死亡及卒中事件.强化组发生亚急性支架血栓形成1例(0.2％),标准组未发生支架血栓形成事件(P =1.000).两组均未发生死亡和主要及次要出血事件,轻度出血发生率两组之间差异无统计学意义(强化组为4.3％,标准组为2.1％,P=0.166).结论强化抗血小板治疗可显著改善急性冠状动脉综合征患者冠状动脉支架术后的HPR,且不增加出血风险,但其临床获益还需更长时间随访研究的证实.     

Optimal management of platelet function after coronary stenting

Opinion statement Coronary stenting elicits vessel wall damage, and subsequent activation of platelets is implicated as a major component of complications such as acute, subacute, and late stent thrombosis. As such, dual antiplatelet therapy using aspirin and clopidogrel has become a routine adjunct to coronary stenting. Use of aspirin and clopidogrel with or without glycoprotein IIb/IIIa inhibitors after coronary stenting reduces the complication rate and improves long-term outcomes. Dual antiplatelet therapy using aspirin and clopidogrel is recommended for at least 4 weeks with bare metal stents, and for 3 to 6 months with drug-eluting stents for prevention of major adverse cardiac events. After coronary stenting, 1 year of dual antiplatelet therapy is recommended for prevention of future cardiac events. However, despite the use of antiplatelet agents, stent thrombosis occurs in approximately 1% of patients, with an increased likelihood of occurrence in high-risk patients or a lesion subset of patients. Although the incidence of stent thrombosis is low, stent thrombosis usually presents as acute coronary syndrome and the mortality rate is up to 45%. Thus, considering the widespread use of stents, a considerable number of people are inadequately protected from thrombotic events despite current standard antiplatelet therapy using aspirin and clopidogrel. A concern with clopidogrel is the loading time and loading dose required to achieve and maintain optimal inhibition of platelet aggregation. The current recommendation for ensuring maximum antiplatelet activity is administration of a 300-mg loading dose of clopidogrel initiated at least 6 hours prior to percutaneous coronary intervention (PCI), and ideally the day before. If this is not possible, a loading dose of 600 mg of clopidogrel should be administered at least 2 hours before PCI. Recently, new combinations of antiplatelet agents (ie, triple therapy using aspirin, clopidogrel, and cilostazol) and new drugs with potent antiplatelet effects (ie, Prasugrel [currently being developed by Sankyo Pharmaceuticals and Ube Pharmaceuticals in Japan and by Eli Lilly and Co. (Indianapolis, IN) in the United States], Cangrelor [currently being developed by AstraZeneca Pharmaceuticals, Wilmington, DE], and AZD6140) have been evaluated in clinical trials; such treatments may help reduce the number of cardiac events after coronary stenting.     

Comparison of antiplatelet effect of loading dose of clopidogrel versus abciximab during coronary intervention.

Randomized clinical trials have evidently shown that the addition of thienopyridines or abciximab to standard aspirin results in a significant reduction of ischaemic complications after coronary stent implantation. A head-to-head comparison of these antithrombotic drug regimens during coronary intervention is, however, lacking, and this was the main aim of the present study. Thirty-nine patients with angina pectoris who were scheduled for coronary stent implantation were assigned to either group 1 (160 mg aspirin + 500 mg ticlopidine post-stent), group 2 (160 mg aspirin + abciximab + 500 mg ticlopidine post-stent) or group 3 (160 mg aspirin + loading dose (375/450 mg) clopidogrel pre-stent and 75 mg clopidogrel post-stent). A loading dose of 450 mg clopidogrel was found to be more effective than the standard loading dose of 375 mg. Platelet aggregation induced by 4 micromol/l adenosine diphosphate (ADP) was assessed in samples collected before intervention and 10 min, 4 h and 20 h after intervention. Before intervention, a moderate antiplatelet effect because of aspirin intake was observed (ADP aggregation level, +/- 50%) in all study groups. After intervention, platelet aggregation tended to be enhanced in group 1 while it was strongly inhibited in the groups pre-treated with clopidogrel or abciximab: ADP induced an aggregation level early after intervention of 60 +/- 12% in group 1 (ticlopidine post-stenting) versus 30 +/- 10% in group 3 (loading dose clopidogrel) versus 3 +/- 6% in group 2 (abciximab). Abciximab achieved a more complete inhibition of aggregation than clopidogrel (P = 0.007). The overall complication rate was low with only one major bleeding and one death due to side-branch occlusion with re-infarction occurring, both in the abciximab group. Platelet aggregation during coronary intervention is strongly inhibited by both abciximab and by high loading dose of clopidogrel. Although abciximab showed a stronger antiplatelet effect than clopidogrel, it remains to be established whether this ex vivo superiority of abciximab also translates into an overall clinical benefit in patients with elective stent implantation.     

Triple versus dual antiplatelet therapy after coronary stenting: impact on stent thrombosis.

OBJECTIVES: We evaluated safety and efficacy of triple antiplatelet therapy with aspirin, clopidogrel, or ticlopidine and cilostazol after coronary stenting. BACKGROUND: Triple antiplatelet therapy might have beneficial effect to prevent thrombotic complications in patients undergoing coronary stenting. METHODS: Patients undergoing successful coronary stenting were divided into dual antiplatelet therapy (aspirin plus clopidogrel or ticlopidine, group I, n = 1,597) and triple antiplatelet therapy (aspirin plus clopidogrel or ticlopidine plus cilostazol, group II, n = 1,415) groups. The primary end point included death, myocardial infarction, target lesion revascularization, or stent thrombosis within 30 days. The secondary end point was side effects of study drugs, including major bleeding, vascular complication, hepatic dysfunction, and hematological complications. RESULTS: Multi-vessel stenting and the use of long stents were more prevalent in group II than in group I. The primary end point was 0.8% in group I and 0.3% in group II (p = 0.085). Stent thrombosis within 30 days was significantly lower in group II (n = 1, 0.1%) than in group I (n = 9, 0.5%; p = 0.024). The independent predictors of stent thrombosis were primary stenting (odds ratio [OR] 7.9, 95% confidence interval [CI] 2.0 to 30.8, p = 0.003) and triple therapy (OR 0.12, 95% CI 0.015 to 0.98, p = 0.048). The overall adverse drug effects, including major bleeding, neutropenia, and thrombocytopenia, were no different between two groups (1.8% vs. 2.6%, p = 0.104). CONCLUSIONS: Compared with the dual antiplatelet regimen, triple antiplatelet therapy seemed to be more effective in preventing thrombotic complications after stenting without an increased risk of side effects. Triple antiplatelet therapy might be safely applied in patients or lesions with a high risk of stent thrombosis.     

阿司匹林、氯吡格雷、西洛他唑抗血栓形成作用及其机制的研究

目的观察常用抗血小板药物阿司匹林、氯吡格雷、西洛他唑的抗血栓形成作用,并探讨其机制。方法将70只SD大鼠随机分成7组各10只,其中对照组不做特殊处理;模型组、阿司匹林组、氯吡格雷组、西洛他唑组、三联组均制备冠状动脉微栓塞模型,建模成功后分别灌服安慰剂、阿司匹林、氯吡格雷、西洛他唑及阿司匹林＋氯吡格雷＋西洛他唑,连续7 d;假手术组在冠状动脉微栓塞模型制作中以生理盐水代替血栓微粒注入左心室,术后灌服安慰剂。实验期间各组均经腹主动脉取血,用自动血凝分析仪分别测定凝血参数凝血酶原时间（PT）、活化部分凝血活酶时间（APTT）和凝血酶时间（TT）,采用血小板聚集率检测仪在6μmol/L的腺苷二磷酸（ADP）诱导下测量最大血小板聚集率,采用ELISA法测定环腺苷酸（c AMP）、血栓素A2（TXA2）和Ⅲ型磷酸二酯酶（PDEⅢ）水平;实验结束后,将各组大鼠仰卧固定消毒、麻醉,采用左颈外静脉、右颈总动脉置入聚乙烯管法检测血栓形成抑制率。结果与模型组比较,4个用药组PT、APTT及TT均明显延长,血小板聚集率明显降低,血栓形成抑制率显著升高,血浆c AMP显著升高、TXA2及PDEⅢ显著降低,尤以三联组为著（P均〈0.01）。实验第3～7天假手术组、阿司匹林组、氯吡格雷组和三联组上述凝血参数均无统计学差异。结论阿司匹林、氯吡格雷、西诺他唑均可抑制血栓形成,三者联用具有协同增效作用;主要作用机制包括减少血小板聚集、上调血浆c AMP及下调TXA2及PDEⅢ水平。     

The effect of clopidogrel, aspirin and both antiplatelet drugs on platelet function in patients with peripheral arterial disease

Peripheral arterial disease (PAD) is associated with platelet hyperactivity. Aspirin and clopidogrel, two platelet inhibitors, act by different mechanisms. Aspirin inhibits thromboxane A2 synthesis and clopidogrel acts on the P2Y12 platelet ADP receptor. We evaluated the effect of clopidogrel (75 mg/day), aspirin (75 mg/day) and then both drugs on several platelet function indices in patients with PAD (n = 20). There was a significant (P = 0.0001) decrease in ADP-induced aggregation, after clopidogrel but not after taking aspirin. Clopidogrel plus aspirin significantly decreased spontaneous platelet aggregation (SPA) (P = 0.01 to P = 0.002) but SPA was not significantly altered by either aspirin or clopidogrel monotherapy. Similarly, monotherapy did not inhibit serotonin (5HT)-induced aggregation but there was a sigificant inhibition (P = 0.03 to P < 0.02) after combination therapy. ADP (0.8 microM)-induced platelet shape change (PSC) was significantly inhibited by clopidogrel (P = 0.004) or aspirin (P = 0.01). This was also true for 5HT-induced PSC (clopidogrel, P = 0.01; aspirin, P = 0.03). Soluble P-selectin decreased significantly (from 32 +/- 24 to 25 +/- 17 ng/ml, P = 0.04) with combination therapy. Plasma platelet-derived growth factor and intraplatelet 5HT levels were not altered by combination therapy. In PAD, clopidogrel is a more potent inhibitor of ADP-induced platelet activation than aspirin; combination therapy is more effective than clopidogrel or aspirin monotherapy. These potentially clinically relevant findings should be evaluated in appropriately designed trials.     

二磷酸腺苷介导血小板聚集率指导老年择期冠状动脉介入治疗患者术后抗血小板药物使用

目的 评价以二磷酸腺苷(ADP)介导血小板聚集率指导抗血小板药物在老年择期经皮冠状动脉介人治疗(PCI)患者中使用对心血管事件的影响.方法 选取我院2007-2008年老年择期西罗莫司涂层支架植入患者1230例,年龄60～80岁,平均(67.2±10.2)岁,随机选取615例入ADP组,首剂300 mg负荷量后,根据血小板聚集率调整氯吡格雷使用量,分别于用药前、用药第2天、第3天测定ADP介导的血小板聚集率,达标后(聚集率较用药前降低50%)75 mg/d.若未达标,第2、3天可逐次增加300 mg,累计至900 mg;若仍未达标,则改用氯吡格雷75 mg/d联合西洛他唑100 mg/d、阿司匹林100 mg/d三重抗血小板药物治疗持续1年.其余615例入常规组,以常规剂量和方法使用氯吡格雷(首剂300 mg负荷量后,继之以75 mg/d口服持续1年).分别于用药前、用药第3天测定ADP介导的血小板聚集率;两组患者均持续口服氯吡格雷1年.所有患者均在给药前、后进行安全性实验室检查.随访1年,记录心血管事件(心原性死亡、心肌梗死、血运重建、支架血栓事件)和药物不良事件发生率.结果 1230例患者首剂负荷量300 mg后.达标率44.9%ADP组累计总量至900 mg时,ADP组达标率增至67.5%,约32.5%的患者(203/615)仍未达标;改用氯吡格雷、西洛他唑、阿司匹林三重抗血小板药物治疗.相对于常规负荷剂量氯吡格雷,高负荷剂量氯吡格雷有更好的抑制血小板聚集的效果(常规负荷剂量对高负荷剂量,45%对67.5%,P=0.028).平均随访(10.0±2.4)个月,两组心血管事件发生率差异有统计学意义(2.8%对4.9%,P=0.035),常规组急性和亚急性支架血栓事件多于ADP组(4例对1例).所有患者均未出现大出血,两组间轻微出血病例差异无统计学意义,无药物不良反应.结论 PCI术后患者应该检测血小板对氯吡格雷的反应效果;ADP介导的血小板聚集率指导老年择期PCI患者围术期抗血小板药物使用安全、有效,可明显降低1年的心血管事件发生率.     

Increased risk in patients with high platelet aggregation receiving chronic clopidogrel therapy undergoing percutaneous coronary intervention: is the current antiplatelet therapy adequate?

OBJECTIVES: We sought to determine whether patients receiving chronic clopidogrel therapy undergoing nonemergent stenting who display high on-treatment preprocedural platelet aggregation measured by standard light transmittance aggregometry and thrombelastography (TEG) will be at increased risk for poststenting ischemic events. BACKGROUND: Patients exhibiting heightened platelet reactivity to adenosine diphosphate (ADP) might be at increased risk for recurrent ischemic events after coronary stenting. METHODS: A total of 100 consecutive patients receiving chronic antiplatelet therapy consisting of aspirin (325 mg qd) and clopidogrel (75 mg qd) were studied before undergoing nonemergent stenting. Patients were followed for 1 year after coronary stenting for the occurrence of death, myocardial infarction, stent thrombosis, stroke, or ischemia requiring a hospital stay. RESULTS: All patients were aspirin responsive. Patients with ischemic events (23 of 100, 23%) within 1 year had greater on-treatment prestent ADP-induced platelet aggregation than patients without ischemic events by aggregometry and TEG (p < 0.001 for both measurements). Of patients with an ischemic event, 70% and 87% displayed high on-treatment platelet reactivity at baseline by aggregometry and TEG, respectively. High on-treatment platelet reactivity as measured by aggregometry and TEG were the only variables significantly related to ischemic events (p < 0.001 for both assays). The administration of eptifibatide reduced periprocedural elevation in platelet reactivity, with no significant differences in bleeding events. CONCLUSIONS: Patients receiving chronic clopidogrel therapy undergoing nonemergent percutaneous coronary intervention who exhibit high on-treatment ADP-induced platelet aggregation are at increased risk for postprocedural ischemic events. These findings might have implications for the alteration in clopidogrel maintenance dose and use of glycoprotein IIb/IIIa inhibitors in selected patients.     

Is a 300 mg clopidogrel loading dose sufficient to inhibit platelet function early after coronary stenting? A platelet function profile study

BACKGROUND: Clopidogrel combined to aspirin reduces the early risk of stent thrombosis and a clopidogrel pre-treatment strategy is associated with a better outcome. However, in clinical practice such pre-treatment strategy is not always feasible and clopidogrel is frequently not administered until the time of intervention. Aim of the study was to compare platelet function profiles in patients undergoing coronary stenting receiving clopidogrel pre-treatment (75 mg x 2 daily at least 48 hours before intervention) compared to that of patients receiving a 300 mg loading dose at intervention time. METHODS: A total of 50 patients were included in whom patients' platelet aggregation (using light transmittance aggregometry) and platelet activation (P-selectin and PAC-1 expression by whole blood flow cytometry) were assessed following ADP stimuli at baseline, and 4 hours and 24 hours following coronary stenting. RESULTS: In the overall study population, 16/50 (32%) patients were pre-treated with clopidogrel and 34/50 (68%) received clopidogrel loading dose at intervention time. Platelet aggregation, as well as P-selectin and PAC-1 expression were significantly lower in clopidogrel pre-treated patients at baseline (p<0.001) and at 4 hours (p<0.01), while they were similarly inhibited 24 hours after intervention. In conclusion, platelet reactivity of patients treated with clopidogrel front loading at intervention time remains significantly higher than that of pre-treated patients in the early hours after coronary stenting. A higher loading dose at intervention time may be warranted to overcome the early risk of thrombotic complications.     

Effect of 150-mg vs 300-mg loading doses of clopidogrel on platelet function in Japanese patients undergoing coronary stent placement

BACKGROUND: The loading dose of ticlopidine is 500 mg in both the US and Europe and 200 mg in Japan. A lower loading dose of clopidogrel might achieve adequate platelet inhibition in Japanese patients. METHODS AND RESULTS: Platelet aggregation was serially measured at baseline, and 2, 4, 6, and 8 h after 150-mg (n=20) and 300-mg (n=20) clopidogrel loading. Platelets were stimulated with 5 and 20 micromol/L adenosine diphosphate (ADP) and aggregation was assessed by optical aggregometry. Pretreatment ADP-induced platelet aggregation in the 150-mg clopidogrel group did not differ from that of the 300-mg group. The administration of 300-mg clopidogrel loading dose resulted in lower platelet aggregation 2 h after the administration (5 micromol/L ADP: 53+/-9% vs 61+/-12%, p<0.05 and 20 micromol/L ADP: 61+/-10% vs 68+/-9%, p<0.05). A lower platelet aggregation induced with 20 micromol/L ADP was still observed 4 h after the 300-mg clopidogrel loading (58+/-10% vs 65+/-9%, p<0.05). CONCLUSIONS: The 150-mg clopidogrel loading does not achieve rapid platelet inhibition. The 300-mg loading dose should be used to suppress platelet function rapidly even in Japanese patients undergoing coronary stent placement.     

Comparison of increased aspirin dose versus combined aspirin plus clopidogrel therapy in patients with diabetes mellitus and coronary heart disease and impaired antiplatelet response to low-dose aspirin

The effects of therapy with aspirin 300 mg/day and with combined aspirin 100 mg/day plus clopidogrel 75 mg/day on platelet function were compared in patients with diabetes mellitus and coronary artery disease and impaired antiplatelet responses to aspirin 100 mg/day. The study population consisted of 151 outpatients with type II diabetes mellitus and coronary artery disease who were taking aspirin 100 mg/day. Of the 151 patients, a subgroup of subjects with impaired aspirin response were selected on the basis of the results of platelet aggregometry. Nonresponsiveness to aspirin was defined as mean aggregation > or =69% with 3 micromol/L adenosine diphosphate and mean aggregation > or =70% with 2 micromol/L collagen. Aspirin semiresponders were defined as meeting 1 but not both of these criteria. Nonresponders and semiresponders were randomized equally to aspirin 300 mg/day and aspirin 100 mg/day plus clopidogrel 75 mg/day, and aggregation tests were repeated after 2 weeks. Sixty of the 151 patients with diabetes (40%) were found to respond to aspirin inadequately. Platelet aggregation induced by adenosine diphosphate and collagen decreased significantly after aspirin 300 mg/day or combined therapy. Combined treatment was found to have a stronger inhibitory effect on platelet aggregation induced by adenosine diphosphate than aspirin 300 mg/day (p = 0.002). Impaired aspirin response was resolved by increasing the aspirin dose or adding clopidogrel to aspirin (p <0.0001 for each). However, desired platelet inhibition was achieved in significantly more patients by combined treatment than by aspirin 300 mg/day (p <0.05). In conclusion, aspirin 100 mg/day does not inhibit platelet function adequately in a significant number of patients with diabetes mellitus and coronary artery disease. Increasing the aspirin dose to 300 mg/day or adding clopidogrel to aspirin can provide adequate platelet inhibition in a significant number of those patients with impaired responses to low-dose aspirin.     

Failure of clopidogrel to reduce platelet reactivity and activation following standard dosing in elective stenting: implications for thrombotic events and restenosis

There is no information on long-term platelet reactivity and activation following elective stenting in patients treated with clopidogrel and aspirin. We measured platelet reactivity and activation at baseline and at 2 h, 24 h, 5 days and 30 days following coronary stenting (n = 94). Patients were treated with the standard aspirin (325 mg) and clopidogrel regimen (300 mg load/75 mg qd). Reactivity was measured by aggregation (5 and 20 microM ADP) and activation was determined by the expression of total and active GP IIb/IIIa. Reactivity and activation were defined as heightened when post-stent aggregation and receptor expression exceeded baseline levels, respectively. Prolonged heightened platelet reactivity was detected by both 5 and 20 microM ADP aggregation. Using 20 microM ADP aggregation, heightened reactivity occurred in 55% of patients at 2 h, 26% at 24 h, 21% at 5 days, and 15% at 30 days post-stenting. A high frequency of heightened platelet activation was detected by both total and active GP IIb/IIIa expression. Using expression of the active GP IIb/IIIa receptor as the marker, activation was greater than baseline in 27% of patients at 2 h, 20% at 24 h, 30% at 5 days, and 22% at 30 days post-stenting. This is the first report demonstrating that a significant percentage of patients receiving standard clopidogrel and aspirin therapy for coronary stenting will have post-drug platelet reactivity and activation above baseline that persists for 30 days after the procedure. These finding suggest insufficient platelet inhibition. The clinical importance of these findings should be further investigated to establish the potential link between insufficient platelet inhibition, stent thrombosis, and restenosis.     

Impaired responsiveness to clopidogrel and aspirin in patients with recurrent stent thrombosis following percutaneous intervention for peripheral artery disease

Patients with peripheral artery disease (PAD) following peripheral percutaneous transluminal angioplasty (PTA) with stent implantation are prone to stent thrombosis despite treatment with aspirin and clopidogrel. Impaired clopidogrel responsiveness is associated with increased risk of ischemic events in patients following coronary stent implantation. We sought to assess platelet responsiveness to clopidogrel and aspirin in patients with PAD and recurrent stent thrombosis. Platelet aggregation induced by 5 and 20?µmol/l adenosine diphosphate (ADP) and 0.5?mmol/l arachidonic acid (AA), together with platelet reactivity index (PRI) and serum thromboxane B₂ (TXB₂), were determined in 11 patients with PAD and a history of stent thrombosis (mean, 3.1?±?1.14) after PTA and in 15 patients with PAD with no such history, also in 11 controls with coronary artery disease (CAD) and previous stent thrombosis. Platelet aggregation to 5?µmol/l ADP was higher in subjects with PAD and stent thrombosis than in those without stent thrombosis (p?=?0.0003) and CAD subjects (p?=?0.002). Aggregation induced by 20?µmol/l ADP was higher in PAD group with stent thrombosis than in PAD subjects without thrombosis (p?=?0.004). The PAD group with stent thrombosis had higher AA-induced platelet aggregation than CAD controls (p?=?0.007) and serum TXB₂ concentrations higher than PAD group without thrombosis (p?=?0.002) and CAD group (p?=?0.02). Concluding, platelet responsiveness to clopidogrel and aspirin is impaired in patients with PAD and recurrent stent thrombosis following PTA, as compared with similar individuals with CAD, and PAD with no history of stent thrombosis. This indicates that atherosclerosis burden affects platelet function and might contribute to stent thrombosis following percutaneous intervention in peripheral arteries.     

Randomized comparison of cilostazol vs clopidogrel after drug-eluting stenting in diabetic patients--clilostazol for diabetic patients in drug-eluting stent (CIDES) trial.

BACKGROUND: Previous studies have shown that cilostazol may not only prevent stent thrombosis, but may also have positive effect in the prevention of restenosis. However, the effect of cilostazol on restenosis after successful deployment of drug-eluting stent (DES) in patients with diabetes mellitus has not been evaluated. METHODS AND RESULTS: A total of 280 patients at 8 clinical sites were randomized. The patients (61.7+/-9.9 years old, 163 males) who underwent successful stenting were randomized to aspirin and cilostazol (group I, n=141, 61.2+/-9.6 years old) vs aspirin and clopidogrel (group II, n=139, 62.0+/-10.0 years old) after 1 month of aspirin, cilostazol, and clopidogrel combination treatment. There were no significant differences in baseline characteristics of the groups. The type of DES implanted did not differ between the groups. There were no differences in angiographic and procedural characteristics of the groups. Major adverse cardiac events, including acute and subacute stent thrombosis within 1 month, did not occur in either group. Cases of angiographic late stent thrombosis were 1 (0.9%) in group I and 1 (0.8%) in group II. Follow-up coronary angiography was performed in 237 patients (84.6%). Mean follow-up duration was 7.1 months. The rate of angiographic restenosis (stent plus 5-mm borders) was 9 (8.0%) in group I and 20 (16.1%) in group II, p=0.041). The minimal luminal diameter at follow-up period in group I was 2.55+/-0.63 mm compared with 2.41+/-0.83 mm in group II (p=NS). CONCLUSIONS: Combination therapy with aspirin and cilostazol for the prevention of stent restenosis is comparable or superior to that of aspirin and clopidogrel in diabetic patients who undergo DES implantation.