The effect of doubling the dose of clopidogrel on platelet aggregation in patients with clopidogrel resistance

Antiplatelet drugs play a pivotal role in the management of patients with acute coronary syndrome. Clopidogrel is an important antiplatelet drug commonly used in the treatment of those patients. However, the variability in patient response to clopidogrel is worrisome because a decreased response may lead to unfavorable clinical outcomes. Thus, it is crucial to study possible ways to overcome this problem. In the current study, we measured platelet aggregation in vitro to identify patients with clopidogrel resistance. Those patients were given double the standard maintenance dose of clopidogrel and platelet aggregation was reassessed. It was found that there was a significant increase in clopidogrel response (p < 0.001). Therefore, we recommend that using double the standard maintenance dose of clopidogrel should be considered in those patients.     

阿托伐他汀联合氯吡格雷对急性冠脉综合征血小板聚集率的影响

目的:探讨急性冠脉综合征(ACS)患者急性期负荷剂量氯吡格雷联合阿托伐他汀或普伐他汀对血小板聚集率和主要不良心血管事件发生率的影响。方法:102例ACS患者被随机分成两组:普伐他汀组(P组)和阿托伐他汀组(A组),两组均予氯吡格雷300mg顿服后,75mg/d维持。P组予普伐他汀。入院后24h内和第14天分别测定TC、HDL-C、LDL-C、血小板聚集率(PAR)、肝功能,并统计两组主要不良心血管事件的发生率。结果:(1)两组TC、HDL-C、LDL-C水平在基础状态和第14d,差异无显著性(P>0.05);(2)P组或A组PAR在治疗后和基线相比,差异有显著性(P<0.05);但P、A两组在治疗后相比,差异无显著性(P>0.05);(3)心血管死亡、再发心肌梗塞复合终点发生率在两组间差异无显著性(P>0.05)。结论:阿托伐他汀或普伐他汀与负荷剂量氯吡格雷联合治疗急性冠脉综合征安全有效,两组效果相似,无显著差异。     

Platelet reactivity in diabetic patients undergoing coronary stenting for acute coronary syndrome treated with clopidogrel loading dose followed by prasugrel maintenance therapy

Background

Diabetes has been identified as a risk factor for impaired clopidogrel response, and these patients might have greater benefit with new P2Y12 blockers such as prasugrel. The present study was designed to assess response to thienopyridine in diabetic patients undergoing PCI for ACS.

Methods and results

107 diabetic patients undergoing PCI for ACS were included and treated by clopidogrel 600 mg loading dose and switched to prasugrel 10 mg daily after PCI. Platelet reactivity was assessed by PRI VASP. High-on-treatment platelet reactivity (HTPR) was defined by PRI VASP > 50% and Low-on-treatment platelet reactivity (LTPR) as PRI VASP below the 75th percentile (PRI VASP < 20%). After clopidogrel, mean PRI VASP was 47 ± 21% and 54 patients (50%) were non responders. At one month, mean PRI VASP on prasugrel 10 mg daily was 31 ± 13%, 9 patients (8%) had HTPR and 23 patients (22%) had LTPR. In multivariate analysis, factors associated with platelet reactivity were waist circumference for HTPR on clopidogrel and body weight for HTPR and LTPR on prasugrel. 10 patients (9%) suffered from BARC bleeding complications. Patients with bleeding complications had significantly lower PRI VASP values: 22 ± 9 vs. 32 ± 13, p = 0.02 and ROC curves identified a cut-off value of VASP = 28% to predict bleeding complications.

Conclusion

The present study confirmed that many diabetic patients treated with clopidogrel for ACS have inadequate platelet inhibition. Switch to prasugrel is effective with acceptable safety in this specific population. We observed a significant relationship between on-treatment platelet reactivity and bleeding complications.     

急性冠状动脉综合征患者冠状动脉支架术前高负荷量氯吡格雷预治疗近期疗效

目的对比研究氯吡格雷600 mg与300 mg负荷剂量预治疗的急性冠状动脉(冠脉)综合征(ACS)行冠脉支架术的病人的近期疗效和安全性.方法前瞻性注册研究,试验组为2003年2月至2004年7月间316例ACS行冠脉支架术的病人,术前均予600 mg氯吡格雷负荷量预治疗.对照组为2001年10月至2003年2月间309例相同条件病人,支架术前予300 mg氯吡格雷负荷量.研究主要终点为30天支架内亚急性血栓发生,死亡、心肌梗死和紧急靶血管血运重建的联合终点;次要终点为30天出血事件.结果两组临床、冠脉造影及介入治疗基线特征无显著差别.氯吡格雷600 mg组支架内亚急性血栓发生率显著低于300 mg组(0.0% vs 2.6%,P=0.003),300 mg组亚急性血栓发生率与服负荷剂量距手术时间<6 h显著相关(OR=6.665,95%CI1.017～43.521,P=0.048).600 mg组死亡、心肌梗死和紧急靶血管血运重建联合终点发生率显著低于300 mg组(0.95% vs 3.6%,P=0.027),主要及次要出血事件发生率600 mg组为1.27%,300 mg组为0.97%,差异无统计学意义(P=1.00).结论高负荷剂量(600 mg)氯吡格雷预治疗与常规负荷量(300 mg)相比,可显著改善ACS行冠脉支架术病人的近期疗效,且安全性相似.     

PlA polymorphism and platelet reactivity following clopidogrel loading dose in patients undergoing coronary stent implantation.

The PlA polymorphism (Leu33Pro) of the platelet glycoprotein (GP) IIIa gene has been suggested to play an important role in coronary thrombosis. In vitro studies have shown differences for this polymorphism in platelet sensitivity towards antiplatelet drugs (aspirin and abciximab), suggesting a pharmacogenetic modulation. The aim of the study was to assess the modulatory effect of the PlA polymorphism on clopidogrel-induced antiplatelet effects in 38 patients undergoing coronary stent implantation receiving a 300 mg clopidogrel loading-dose. Platelet reactivity was assessed as GPIIb/IIIa activation and P-selectin expression in platelets stimulated with 2 micromol/l adenosine diphosphate using whole blood flow cytometry. The distribution of the homozygous PlA1/A1 and heterozygous PlA1/A2 genotypes were 74 and 26%, respectively. PlA2 carriers had a higher degree of GPIIb/IIIa activation (P = 0.05) and P-selectin expression (P = 0.02) during the overall study time course and a lower antiplatelet effect to a 300 mg clopidogrel loading-dose up to 24 h following intervention (P < 0.05). In conclusion, the Pl polymorphism of the GPIIIa gene modulates platelet reactivity towards clopidogrel front loading in patients undergoing coronary stenting. This suggests the need for individualized antithrombotic regimens to optimally inhibit platelet reactivity.     

High platelet reactivity is associated with vascular function in patients after percutaneous coronary intervention receiving clopidogrel

Background

In the present study, we evaluated the association of platelet reactivity with vascular function in patients after percutaneous coronary intervention receiving clopidogrel treatment.

Methods

We enrolled 150 patients with stable CAD receiving clopidogrel regimen (75 mg/d), 1 month after percutaneous coronary intervention. Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as an index of arterial wave reflections. High on treatment platelet reactivity (HPR) was evaluated using VerifyNow Assay. VerifyNow reports its results in P2Y12 reaction units (PRU), and the diagnostic cutoff value is 230 PRU. Patients were evaluated prospectively up to 24 months. The primary end point was a composite of death from cardiovascular causes, nonfatal major cardiovascular events and hospitalization for cardiovascular causes.

Results

There was no difference in the basic clinical and demographic characteristics between subjects with HPR and non-HPR. Subjects with high on treatment platelet reactivity and PRU > 230 had significantly increased PWV (8.81 ± 2.25 m/s vs. 7.69 ± 1.95 m/s, p = 0.001) and AIx (25.27 ± 8.67% vs. 20.87 ± 10.57%, p = 0.04) compared to subjects with PRU ≤ 230. PWV was also associated with PRU (r = 0.23, p = 0.02). HPR was associated with significantly increased risk of primary end point [HR = 5.38, 95%CI:(1.15, 26.04), p = 0.03].

Conclusions

Increased platelet reactivity is associated with impaired arterial stiffness in patients after percutaneous coronary intervention receiving clopidogrel treatment, highlighting another clinical factor implicated in individual platelet response to antiplatelet therapy. Moreover, increased platelet reactivity is associated with adverse outcome in these patients.     

Clinical predictors of high posttreatment platelet reactivity to clopidogrel in Koreans

Introduction: High posttreatment platelet reactivity to clopidogrel (HPPR) is associated with major adverse cardiac events. However, the clinical predictors of HPPR in Asians have not been studied previously. Aims: We sought to determine clinical predictors of HPPR in Koreans. Results: We measured platelet reactivity with the VerifyNow P2Y12 assay in 1431 consecutive patients undergoing coronary angiography. We used the cut‐off value of greater than 275 P2Y12 Reaction Unit (PRU) to define patients with HPPR. The clinical characteristics were compared between patients with HPPR (36.3%) and those without HPPR (63.7%). The mean age (65.4 ± 9.1 vs. 62.2 ± 9.7 years) was higher, hypertension (68.5% vs. 62.0%), diabetes mellitus (35.4% vs. 28.5%), chronic kidney disease (36.3% vs. 22.5%), renal replacement treatment (1.2% vs. 0.2%), and congestive heart failure (1.3% vs. 0.3%) were more common among patients with HPPR, while male gender (72.6% vs. 54.8%) and smoking (19.9% vs. 13.1%) were more common among non‐HPPR patients. Mean glomerular filtration rate (63.5 ± 18.6 vs. 69.7 ± 16.1 mL/min/1.73 m³) was lower and C‐reactive protein (hs‐CRP) (6.6 ± 20.5 mg/L vs. 4.2 ± 12.1 mg/L) level was higher among those with HPPR. Independent predictors of HPPR were female gender (OR 1.90, P≤ 0.001), chronic kidney disease (OR 1.51, 0 = 0.004), diabetes mellitus (OR 1.35, P= 0.024), hs‐CRP ≥ 2.0 mg/L (OR 1.31, P= 0.005), and age increase in decades (OR 1.21, P= 0.002), while smoking was negative risk factor (OR 0.63, P= 0.015). The number of risk factors was linearly associated with the risk of HPPR, with most patients having one or two predictors. Conclusion: In Korean population, independent clinical predictors of HPPR included diabetes mellitus, increased age, female gender, chronic kidney disease, and hs‐CRP ≥ 2.0 mg/L, while cigarette smoking was associated with better responsiveness. Mean platelet reactivity and HPPR prevalence steadily increased with the number of clinical predictors.     

Simultaneous targeting of MCL1 and ABCB1 as a novel strategy to overcome drug resistance in human leukaemia

Drug resistance is a major obstacle to chemotherapy success in leukaemia. Although ABCB1 ( MDR1 ) overexpression represents a critical mechanism of drug resistance, modulation of ABCB1 shows unsatisfactory clinical outcome. Recent studies showed that MCL1 was upregulated in numerous haematological and solid tumour malignancies. The present study found that patients with newly diagnosed or relapsed/refractory leukaemia expressed higher MCL1 levels than patients that were in complete remission. We demonstrated that overexpression of MCL1 decreased sensitivity of human leukaemia cell lines to cytotoxic drugs and inhibited drug-induced apoptosis. Specific downregulation of MCL1 via RNA interference sensitized multidrug resistant leukaemia cells towards chemotherapy and induced apoptosis. Our study also demonstrated that MCL1 and ABCB1 mediated drug resistance through different mechanisms and the depletion of both MCL1 and ABCB1 showed an additive effect in reversing drug resistance and promoting drug-induced apoptosis. Thus, this study documented an important role of MCL1 in drug resistance and apoptosis. Simultaneous targeting of MCL1 and ABCB1 could be a novel approach to overcome drug resistance in leukaemia.     

Vitamin D levels and high-residual platelet reactivity in patients receiving dual antiplatelet therapy with clopidogrel or ticagrelor

Background: Suboptimal platelet inhibition still represents an important challenge, especially for patients undergoing percutaneous coronary interventions (PCIs). However, very few are known so far on the predictors of high-residual platelet reactivity (HRPR) despite antiplatelet strategies. Increasing attention has been paid in the last years to the role of vitamin D in atherothrombosis. Therefore, the aim of our study was to evaluate the impact of vitamin D levels on platelet function in patients treated with dual antiplatelet therapy (DAPT). Patients treated with DAPT (ASA and clopidogrel or ticagrelor) after a recent acute coronary syndrome (ACS) or elective PCI were scheduled for platelet function assessment at 30–90 days post-discharge. Platelet function was assessed by whole blood impedance aggregometry (Multiplate®-Roche Diagnostics AG), HRPR was considered for ASPI test values > 862 AU*min (for ASA) and adenosine diphosphate (ADP) test values ≥417 AU*min (for ADP-antagonists). Fasting samples were obtained for main chemistry parameters and vitamin D level assessment.

Our population is represented by 503 patients, who were divided according to vitamin D quartiles (≤9.1; 9.2–14.4; 14.5–21.7; >21.7 ng/ml). Lower vitamin D levels related with age (p = 0.04), diabetic status (p = 0.05), and previous coronary surgery (p = 0.007), therapy with beta-blockers and statins (p = 0.01 and p = 0.02). Vitamin D inversely related to the levels of total cholesterol (p = 0.01), triglycerides (p < 0.001), hemoglobin (p = 0.05), and HbA1c (p < 0.001). Significantly higher platelet reactivity was observed after platelet stimulation with ADP (p = 0.01), but not with other platelet activators. The prevalence of HRPR for ASA was low (1.2%) and not conditioned by Vitamin D levels (adjusted OR[95%CI] = 1.56[0.71–3.5], p = 0.27). HRPR with ADP-antagonists was observed in 26% of patients, and the rate increased with lower vitamin D quartiles (37.3% vs 22.2% vs 24.4% vs 20.2%, p = 0.005, adjusted OR[95%CI] = 1.23[1.02–1.49], p = 0.04).

An absolute increase in HRPR with lower vitamin D levels was similarly observed among patients receiving ticagrelor (adjusted OR[95% CI] = 1.40[0.95–2.06], p = 0.08), and those on clopidogrel (adjusted OR[95%CI] = 1.31[0.99–1.75], p = 0.06).

Thus, lower vitamin D levels are associated with higher platelet reactivity and impaired effectiveness of ADP-antagonists, while not influencing the effectiveness of ASA. Future studies will tell whether vitamin D supplementation can reduce platelet reactivity, overcoming the phenomenon of resistance to antiplatelet agents.     

PON1、ABCB1基因多态性在急性轻型脑卒中患者中的分布及其对短期预后的影响

目的 研究急性轻型脑卒中患者PON1 rs662、ABCB1 rs1045642位点的基因型分布情况,及其对短期预后的影响.方法 纳入2018年9月-2019年6月在新疆医科大学第一附属医院神经内科住院治疗的急性轻型脑卒中患者,治疗上采用阿司匹林100 mg/d加氯吡格雷75 mg/d治疗21天后改为长期服用氯吡格雷7...     

冠状动脉支架患者氯吡格雷抵抗现象探讨

目的 ①评价冠状动脉支架(CS)置入患者氯吡格雷抵抗的发生情况;②观察CS术后1个月复发缺血事件与氯吡格雷抵抗的关系.方法 ①所有入选患者于服氯吡格雷前、服药后24 h及1个月分别测定ADP(25 μmol/L)诱导的血小板聚集率,计算血小板聚集抑制率(△A),△A≤10%(包括负值)时考虑存在氯吡格雷抵抗;②观察CS术后1个月内复发缺血事件的情况.结果 ①共入选患者42例,其中△A 24 h≤10%者18例(43%),△A1m≤10%者13例(31%);②在1个月的随访中,无一例患者因心血管疾病死亡或再发心肌梗死,△A1m≤10%的患者有1例发生脑梗死,1例复发心绞痛,缺血事件发生率为15.4%,△A1m＞10%的患者未发现缺血事件.结论 ①一部分CS患者存在氯吡格雷抵抗,测定血小板聚集率有助于发现这部分患者;②氯吡格雷抵抗患者CS术后1个月内复发缺血事件增加.     

Investigation of ABCB1 1236 and 2677 SNPs in patients with peptic ulcer

Abstract

Objective. P-gp, encoded by ABCB1 gene, is an ATP-binding membrane pump, which exports substrates from the cell including drugs and xenobiotics. Changes in the function of P-gp as a result of polymorphism could have an impact in some diseases' risks and treatment outcomes. The aim of the study was to determine the significance of the ABCB1 gene SNPs: 1236 and 2677 for peptic ulcer risk and development of Helicobacter pylori infection in peptic ulcer patients. Material and methods. One hundred and ninety-five biopsy specimens obtained from peptic ulcer patients (investigated group) were genotyped using sequencing for common SNPs of ABCB1: 1236 and 2677. Genotyping data were compared with the results from healthy subjects (control) and with the presence of H. pylori infection, which was estimated by urease test. Results. No statistically significant difference in frequency of genotypes and alleles for the SNPs were found between the investigated group and the control. However, in the peptic ulcer patients, mutant TT homozygotes and those who carried at least one allele T for the polymorphisms 1236 and 2677 were observed more frequently than the control group. In the peptic ulcer group, there were no significant dependences between the presence of H. pylori infection and the investigated polymorphisms other than more frequent occurrence of TT 1236 homozygous in the group of infected women (p = 0.0298). Conclusions. The TT genotype and the mutated allele T for the polymorphisms 1236 and 2677 could increase peptic ulcer risk. ABCB1 1236 polymorphism may also be associated with an increased likelihood of H. pylori infection development, especially in women.     

血栓弹力图评价急性冠脉综合征患者氯吡格雷抗血小板效果

目的：利用血栓弹力图评价老年急性冠脉综合征（ACS）非血运重建患者不同剂量氯吡格雷的抗血小板效果。方法：60例老年ACS未进行血运重建的患者被随机分为：甲组（30例,冠状动脉造影术后予氯吡格雷75mg／d维持）,乙组（30例,冠脉造影术后予氯吡格雷50mg／d维持）,两组冠脉造影术前均予氯吡格雷300mg口服。冠脉造影术前24h内及造影术后一周后分别测定两组患者肝肾功能及以血栓弹力图法测定血小板抑制率。并观察3个月内两组的主要心脏不良事件及不良反应。结果：与治疗前比较,治疗一周后两组患者ADP诱导的血小板抑制率[甲组：（25．8±11．4）％比（75．2±12．3）％,乙组：（24．2±13．3）％比（64．8±17．5）％]和花生四烯酸（AA）诱导的血小板抑制率[甲组：（16．7±21．6）％比（82．7±25．4）％,乙组：（23．8±22．2）％比（80．2±22．7）％,P〈0．053均明显升高,两组比较无显著差异（P〉0．05）。3个月内两组的心脏不良事件及不良反应无显著差异（P〉0．05）。结论：对非血运重建的急性冠脉综合征老年患者,低剂量氯吡格雷同样有效。     

Evidence of platelet sensitization to ADP following discontinuation of clopidogrel therapy in patients with stable coronary artery disease

Epidemiological studies have linked clopidogrel discontinuation with an increased incidence of ischemic events. This has led to the hypothesis that clopidogrel discontinuation may result in a pharmacological rebound. We evaluated the impact of clopidogrel discontinuation on platelet function. Platelet aggregation was measured by light transmission aggregometry (LTA) in response to adenosine diphosphate (ADP) 0.5, 1, 1.5, 2.5, 5 and 10?µM and by VerifyNow® P2Y₁₂, in 37 clinically stable coronary artery disease (CAD) patients scheduled to discontinue clopidogrel treatment, and 37 clinically stable CAD patients not taking clopidogrel. Platelet function was assessed the day before clopidogrel cessation and 1, 3, 7, 14, 21 and 28 days after. Clopidogrel had been initiated a median of 555 days (ranging from 200 to 2280 days) before the treating cardiologist recommended its discontinuation. All participants were taking aspirin, most commonly 80?mg daily although a minority was prescribed 325?mg daily. Following clopidogrel discontinuation, VerifyNow® P2Y₁₂ did not detect any rebound platelet activity, but ADP-induced LTA showed platelet sensitization to ADP, particularly at low ADP levels. Increased platelet activity was detectable seven days after clopidogrel cessation and remained higher than in controls 28 days after discontinuation. No clinical event occurred in any of the participants during the 28 days following clopidogrel cessation. In conclusion, platelet sensitization to ADP as a consequence of chronic clopidogrel administration may partially explain the recrudescence of ischemic events following clopidogrel discontinuation in otherwise stable coronary artery patients.     

To adjust or not to adjust the platelet count in light transmission aggregometry in patients receiving dual aspirin/clopidogrel treatment

We evaluated whether the results of light transmittance aggregometry (LTA) differ when “native” platelet-rich plasma (PRP) or adjusted (to a standard platelet count of 250.000/µL) PRP is used in patients on dual antiplatelet therapy with aspirin and clopidogrel. LTA has been performed on the blood of 142 stable angina pectoris patients who were adequately pretreated with aspirin and clopidogrel. Platelet aggregation was significant higher in native PRP as compared to platelet count adjusted PRP (P<0.0001) for all four concentrations of adenosine-5′-diphosphate (ADP) (2,?5,?10 and 20?μmol/L). The interindividual variability was significantly higher in platelet count adjusted PRP as compared to native PRP when stimulated with 10 and 20?μmol/L of ADP. The absolute magnitude of aggregation in non-adjusted PRP is clearly dependent on platelet number. These observations are important since several studies have used empirically defined cut-off levels to segregate non-responders from responders to clopidogrel therapy.