Clinical relevance of aspirin resistance in patients with stable coronary artery disease: a prospective follow-up study (PROSPECTAR).

Aspirin resistance may increase the risk of major adverse cardiac events (MACE) more than threefold in patients with stable coronary artery disease (CAD). This study aimed to determine the prevalence of aspirin resistance in patients with stable CAD, the role of aspirin resistance on outcome in the follow-up, and the effect of clopidogrel therapy in MACE prevention in aspirin-resistant individuals. We detected the prevalence of aspirin resistance in 234 patients with stable CAD. Platelet function was determined by PFA-100 with collagen and/or epinephrine and collagen and/or ADP cartridges. The mean follow-up time was 20.6 +/- 6.9 months. The primary endpoints of the study were occurrence of myocardial infarction, unstable angina, stroke and cardiac death. Of patients, 22.2% (n = 52) were aspirin resistant by PFA-100. During follow-up, MACE occurred in eight patients (15.4%) with aspirin resistance and in 20 patients (11.0%) with aspirin-sensitive platelet aggregation (P = 0.269). MACE increased in aspirin-resistant patients after termination of clopidogrel therapy. Eleven patients experienced MACE after cessation of clopidogrel therapy (P < 0.001). The MACE risk in patients with stable CAD having detected aspirin resistance was similar compared with patients having aspirin-sensitive platelet aggregation by PFA-100. The MACE prevalence increased during follow-up, however, just after cessation of clopidogrel therapy.     

Measurement of platelet aggregation during antiplatelet therapy in ischemic stroke

Aspirin, ticlopidine and clopidogrel are used as a pharmacological means to efficiently decrease the number of reoccurrence of ischemic stroke (100-325 mg/d). This antiplatelet treatment could prevent the secondary stroke by approximately 22%. Laboratory effective platelet inhibition for the clinician, and methods for routine screening evaluation for the laboratory were studied. (1) For the standardisation of platelet aggregation technology blood samples of 150 healthy persons were studied in 5 centres. CARAT TX computerised optical aggregometer was used for measuring with collagen (2 microg/ml), epinephrine (10 microM), arachidonic acid 0.5 mM and ADP 5 microM as inductors. (2) Laboratory tests were compared in each centres performed in platelet-rich plasma of ischemic cardiovascular and stroke patients (n=823) taking 100-325 mg aspirin/d. (3) Blood samples of 555 ischemic stroke patients treated with aspirin (100-325 mg/d), 96 patients treated with ticlopidine (500 mg/d), and 67 patients treated with clopidogrel (75 mg/d) were evaluated, respectively.(1) The mean of maximal aggregation (%) - 2SD of untreated controls (n=150) were detected for collagen with 64%, epinephrine 59% and ADP 62%. (2) In 823 aspirin treated patients were found similar inhibition in different centres with same methods for standardisation. The mean inhibition level was in case of collagen 38%, epinephrine 37% and ADP 61%. (3) The distribution of ineffective platelet inhibition was detected in 17% of aspirin group (collagen and epinephrine), 4% of ticlopidine and 18% of clopidogrel group with ADP, respectively. Our findings were in the stroke cohort: effective inhibition levels: 36% in aspirin group, 73% in ticlopidine and 25% treated with clopidogrel. Platelet aggregation tests could help to find the optimal, and "custom taylored" dose of antiaggregating drugs in the secondary prevention of ischemic stroke.     

Relationship between the serum sCD40L level and aspirin-resistant platelet aggregation in patients with stable coronary artery disease

BACKGROUND: Current evidence supports the central role of inflammation in all phases of the atherosclerotic process, including its thrombotic complications. Increased serum sCD40L may trigger platelet activation, so the aim of the present study was to determine the relation between sCD40L levels and aspirin-resistant platelet aggregation in patients with coronary atherosclerosis. METHODS AND RESULTS: A total of 167 consecutive patients (39-85 years old, 35.9% women) with stable coronary artery disease was enrolled in the study. Platelet function was evaluated by a Platelet Function Analyzer 100 device (PFA-100) with collagen and epinephrine (Col/Epi) and collagen and adenosine diphosphate (ADP) (Col/ADP) cartridges. Aspirin resistance was defined as a closure time (CT) <186 s with Col/Epi cartridges, despite regular aspirin therapy. Serum sCD40L level was determined quantitatively with an ELISA method. Fifty-seven (34.1%) patients had aspirin resistance according to the PFA-100. Mean CT measured with the Col/ADP cartridges was 83+/-18 s (65-101 s). Mean serum sCD40L was 157 pg/ml (6-700 pg/ml) in the entire cohort. Patients with aspirin resistance had a mean serum sCD40L level of 166 pg/ml and patients with aspirin-sensitive platelet aggregation had an sCD40L level of 152 pg/ml (p=0.582). CONCLUSION: The sCD40L level is similar in patients with aspirin-resistant and aspirin-sensitive platelet aggregation according to the PFA-100. There is still need for further studies to elucidate the relationship between aspirin-resistant platelet aggregation and sCD40L, which is now known to be prothrombotic, proinflammatory and to be a risk factor for cardiovascular events.     

The role of aspirin resistance on outcome in patients with acute coronary syndrome and the effect of clopidogrel therapy in the prevention of major cardiovascular events

Background: Aspirin resistance may increase up to more then threefold the risk of major cardiovascular events (MACE) in patients with stable coronary artery disease. Aim:The aim of our study was to determine; the prevalence of aspirin resistance in patients with acute coronary syndromes, the role of aspirin resistance on outcome in the follow-up and the effect of clopidogrel therapy in the prevention of MACE in aspirin resistant subjects. Material and methods: We detected the prevelance of aspirin resistance in 105 patients with acute coronary syndrome. Platelet functions were analyzed in Platelet Function Analyzer (PFA)-100 (Dade Behring, Germany) with collagen and/or epinephrine (Col/Epi) and collagen and/or ADP (Col/ADP) cartridges. Primary end points of the study were myocardial infarction, unstable angina, cardiac death. Results: 19% (n = 20) of patients were aspirin resistant by PFA-100. In the follow-up, MACE occured in 9 patients (45%) with aspirin resistance and in 10 patients (11.7%) with aspirin sensitive platelet aggregation (p = 0.001). Multivariate analysis showed that aspirin resistance was an independant predictor of MACE. The prevalence of MACE in patients who were on clopidogrel treatment for 12 months were lower compared to those who were on a clopidogrel treatment for the first six months (p = 0.040). Conclusions: We determined that the MACE risk in patients with acute coronary syndromes having detected aspirin resistance, was higher at statistically significant levels compared to patients having aspirin sensitive platelet aggregation. Our results showed that aspirin resistance, was an independant predictor of MACE in patients with acute coronary syndrome.     

Aspirin-resistant platelet aggregation in a cohort of patients with coronary heart disease.

Aspirin resistance could be defined as thrombotic and embolic cardiovascular events despite regular aspirin therapy. The study aimed to determine the profile and prevalence of aspirin resistance in coronary artery disease patients. We evaluated the prevalence of aspirin resistance in a cohort of 505 patients with the diagnosis of coronary artery disease taking 80-300 mg regular aspirin daily. Platelet functions were analyzed by the Platelet Function Analyzer (PFA)-100 with collagen and epinephrine cartridges and collagen and ADP cartridges. A closure time of 186 s or less with the collagen and epinephrine cartridge was defined as aspirin resistance. Of the patients, 118 (23.4%) were aspirin resistant by the PFA-100. Aspirin-resistant patients were more likely to be older than aspirin-sensitive patients (P = 0.024). No statistically significant differences between the aspirin-resistant and aspirin-sensitive individuals were present in gender, major risk factors of coronary artery disease, number and localization of involved coronary vessels, serum lipid levels, and blood counts. According to the high prevalence of coronary heart disease, many people are affected by aspirin resistance, which may play a role in adverse cardiovascular events. Monitoring of platelet function in patients with coronary heart disease may support the optimization of antiplatelet therapy with additional and/or alternative agents.     

心血管病患者中的阿司匹林抵抗

目的　前瞻性地评价心血管病患者发生阿司匹林抵抗 (AR)的流行病学概况 ,并探讨其预测因子。方法　 35 2例病情稳定的心血管病住院患者 ,每日服用阿司匹林 10 0mg ,连服 7天 ,服用最后一剂后 2 4h内抽取的空腹静脉血为血样 ,分别用二磷酸腺苷 (ADP)、花生四烯酸 (AA)诱导血小板凝集试验 (PAgT) ,检测血小板聚集率。结果　患者中AR发生率为 3.98% ,阿司匹林半敏感 (ASR)者占 2 5 .9% ,且AR或ASR患者中的女性较AS者多(35 .2 %vs 18.2 % ,P =0 .0 0 1) ,而AS者中吸烟者较AR或ASR者多 (0 %vs 9.5 % ,P =0 .0 0 2 )。结论　阿司匹林用于抗血小板治疗及预防动脉硬化事件的心血管病患者 ,若有AR存在可选择其他安全有效的抗血小板制剂长期服用 ,预测AR及抗血小板治疗个体化 ,将是抗血小板治疗未来的方向     

冠心病患者阿司匹林抵抗的相关因素

目的观察冠心病患者发生阿司匹林抵抗的发生率,并探讨冠心病患者出现阿司匹林抵抗现象的相关因素。方法60例病情稳定的冠心病住院患者,每日口服拜阿司匹林100 mg,连服7 d,分别以二磷酸腺苷（ADP）和花生四烯酸（AA）为诱导剂,检测血小板聚集功能。结果阿司匹林抵抗（AR）发生率为20%;阿司匹林半敏感（ASR）者占13%。与阿司匹林敏感（AS）者相比,伴有高脂血症、糖尿病的冠心病患者AR较多（50%vs15%,P<0.05）,两组年龄、性别、吸烟和并发高血压病统计无显著性差异。结论伴有高脂血症、糖尿病的冠心病患者发生阿司匹林抵抗较多,阿司匹林抵抗与年龄、性别、吸烟和并发高血压病等因素无关。     

A prospective,blinded determination of the natural history of aspirin resistance among stable patients with cardiovascular disease

OBJECTIVES: This study was designed to determine if aspirin resistance is associated with clinical events. BACKGROUND: Aspirin resistance, defined by platelet function testing and presumed clinical unresponsiveness to aspirin, has been previously reported by our group and others. However, little information exists linking the laboratory documentation of aspirin resistance and long-term clinical events. METHODS: We prospectively enrolled 326 stable cardiovascular patients from 1997 to 1999 on aspirin (325 mg/day for > or =7 days) and no other antiplatelet agents. We tested for aspirin sensitivity by optical platelet aggregation using adenosine diphosphate (ADP) and arachidonic acid (AA). The primary outcome was the composite of death, myocardial infarction (MI), or cerebrovascular accident (CVA). Mean follow-up was 679 +/- 185 days. Aspirin resistance was defined as a mean aggregation of > or =70% with 10 microM ADP and > or =20% with 0.5 mg/ml AA. RESULTS: Of the patients studied, 17 (5.2%) were aspirin resistant and 309 (94.8%) were not aspirin resistant. During follow-up, aspirin resistance was associated with an increased risk of death, MI, or CVA compared with patients who were aspirin sensitive (24% vs. 10%, hazard ratio [HR] 3.12, 95% confidence interval [CI] 1.10 to 8.90, p = 0.03). Stratified multivariate analyses identified platelet count, age, heart failure, and aspirin resistance to be independently associated with major adverse long-term outcomes (HR for aspirin resistance 4.14, 95% CI 1.42 to 12.06, p = 0.009). CONCLUSIONS: This study demonstrates the natural history of aspirin resistance in a stable population, documenting a greater than threefold increase in the risk of major adverse events associated with aspirin resistance.     

Effect of Ginkgo biloba (EGb 761) and aspirin on platelet aggregation and platelet function analysis among older adults at risk of cardiovascular disease: a randomized clinical trial.

Several case reports have implicated Ginkgo biloba in clinically adverse bleeding disorders. Ginkgo biloba has been reported to increase pain-free walking distance among patients with peripheral artery disease (PAD). Standard PAD therapy includes 325 mg/day aspirin. The objective of this study was to examine potential adverse effects of concomitant aspirin and Ginkgo biloba on platelet function. Ginkgo biloba (EGb 761, 300 mg/day) was compared with placebo for effects on measures of platelet aggregation among adults consuming 325 mg/day aspirin in a randomized, double-blind, placebo-controlled, parallel design trial of 4-week duration. Participants were adults, age 69 +/- 10 years, with PAD or risk factors for cardiovascular disease. Outcome measures included platelet function analysis (PFA-100 analyzer) using ADP as an agonist (n = 26 placebo; n = 29 ginkgo), and platelet aggregation using ADP, epinephrine, collagen and ristocetin as agonists (n = 21 placebo; n = 23 ginkgo). Participants kept daily logs of bleeding or bruising episodes. There were no clinically or statistically significant differences between treatment groups for any agonists, for either PFA-100 analysis or platelet aggregation. Reports of bleeding or bruising were infrequent and similar for both study groups. In conclusion, in older adults with PAD or cardiovascular disease risk, a relatively high dose of Ginkgo biloba combined with 325 mg/day daily aspirin did not have a clinically or statistically detectable impact on indices of coagulation examined over 4 weeks, compared with the effect of aspirin alone. No adverse bleeding events were observed, although the trial was limited to a small sample size.     

Evaluation of platelet function in aspirin treated patients with CAD

Background: Studies of platelet function in the acute coronary syndrome (ACS) have revealed both increased and unchanged platelet activation. To obtain a better understanding of platelet function in coronary artery disease in the setting of aspirin therapy, we performed platelet functional testing in patients with ACS and compared results to patients without CAD. Methods: We measured platelet aggregation and activation in response to ADP and epinephrine in 80 age and gender matched hospitalized patients (40 with ACS, 40 with non-cardiac chest pain (NCCP)). All subjects received ASA (81–325 mg). Platelet aggregation was performed using standard light transmission in platelet-rich plasma and activation was measured via flow cytometric analyses. We also studied platelet function under high shear rates measured by the platelet function analyzer (PFA-100). Results: ASA effect was found to be present in all subjects by blunted platelet aggregation in response to arachidonic acid. Patients with ACS showed significantly higher levels of platelet aggregation to epinephrine compared to patients with NCCP (p = 0.001). Other measures of platelet function including ADP aggregation, Pselectin, activated glycoprotein IIb/IIIa expression, and PFA-100 were unchanged between the two groups. Conclusions: We have found conflicting results of platelet functional testing in ACS. Specifically aspirin therapy in patients with ACS is effective in suppressing the platelet release response and is effective in the partial suppression of platelet aggregation; however, it appears that ACS patients have increased platelet aggregation to adrenergic stimuli when compared to age and gender matched controls without CAD despite the use of aspirin. In some studies, because ACS patients have an accentuated response to adrenergic stimuli this might be interpreted as aspirin resistance. Our study suggests that depending on the assay used to determine aspirin resistance, not all patients with this label are resistant to the biological effects of aspirin but they may have higher than normal baseline platelet sensitivity to adrenergic stimuli. This research was supported by grant K23HL67066 from the National Institute of Health.