Effects of intravenous lysine acetylsalicylate versus oral aspirin on platelet responsiveness in patients with ST-segment elevation myocardial infarction: the ECCLIPSE-STEMI trial.

Prasugrel and ticagrelor, new P2Y12-ADP receptor antagonists, are associated with greater pharmacodynamic inhibition and reduction of cardiovascular events in patients with an acute coronary syndrome. However, evidence is lacked about the effects of achieving faster and stronger cyclooxygenase inhibition with intravenous lysine acetylsalicylate (LA) compared to oral aspirin. Recently, we demonstrated in healthy volunteers that the administration of intravenous LA resulted in a significantly reduction of platelet reactivity compared to oral aspirin. Loading dose of LA achieves platelet inhibition faster, and with less variability than aspirin. However, there are no data of this issue in patients with an ST-segment elevation myocardial infarction (STEMI). This is a prospective, randomized, multicenter, open platelet function study conducted in STEMI patients. Subjects were randomly assigned to receive a loading dose (LD) of intravenous LA 450 mg plus oral ticagrelor 180 mg, or LD of aspirin 300 mg plus ticagrelor 180 mg orally. Platelet function was evaluated at baseline, 30 min, 1 h, 4 h and 24 h using multiple electrode aggregometry and vasodilator-stimulated phosphoprotein phosphorylation (VASP). The primary endpoint of the study is the inhibition of platelet aggregation (IPA) after arachidonic acid (AA) 0.5 mM at 30 min. Secondary endpoints were the IPA at 1, 4, and 24 h after AA, and non-AA pathways through the sequence (ADP and TRAP). A total of 32 STEMI patients were randomized (16 LA, 16 aspirin). The inhibition of platelet aggregation after AA 0.5 mM at 30 min was greater in subjects treated with LA compared with aspirin: 166 vs. 412 respectively (p = 0.001). This differential effect was observed at 1 h (p = 0.01), but not at 4 and 24 h. Subjects treated with LA presented less variability and faster inhibition of platelet aggregation wit AA compared with aspirin. The administration of intravenous LA resulted in a significantly reduction of platelet reactivity compared to oral aspirin on ticagrelor inhibited platelets in patients with STEMI. Loading dose of LA achieves an earlier platelet inhibition, and with less variability than aspirin.Trial Registration: Unique identifier: NCT02929888; URL: http://www.clinicaltrials.gov.

Vascular Injury After Stenting　- Insights of Systemic Mechanisms of Vascular Repair.

BACKGROUND: The role of circulating progenitor cells (CPC) in vascular repair following everolimus-eluting stent (EES) implantation is largely unknown. The aim of the study was to investigate the relationship between temporal variation in CPC levels following EES implantation and the degree of peri-procedural vascular damage, and stent healing, as measured by optical coherence tomography (OCT).Methods and Results: CPC populations (CD133+/KDR+/CD45low) included patients with stable coronary artery disease undergoing stent implantation, and were evaluated using a flow cytometry technique both at baseline and at 1 week. OCT evaluation was performed immediately post-implantation to quantify the stent-related injury and at a 9-month follow up to assess the mid-term vascular response. Twenty patients (mean age 66±9 years; 80% male) with EES-treated stenoses (n=24) were included in this study. Vascular injury score was associated with the 1-week increase of CD133+/KDR+/CD45low (ß 0.28 [95% CI 0.15; 0.41]; P<0.001) and with maximum neointimal thickness at a 9-month follow up (ß 0.008 [95% CI 0.0004; 0.002]; P=0.04). Inverse relationships between numbers of uncoated and apposed struts for the 9-month and the 1-week delta values of CD133+/KDR+/CD45low (ß -12.53 [95% CI -22.17; -2.90]; P=0.011), were also found. CONCLUSIONS: The extent of vessel wall injury influences early changes in the levels of CPC and had an effect on mid-term vascular healing after EES implantation. Early CPC mobilisation was associated with mid-term strut coverage.

Platelet Apoptotic Response May Be Associated With the Capacity of Aspirin to Inhibit Platelets.

An inadequate platelet response to aspirin (ASA) has been identified in some patients under chronic ASA treatment. The aim of this study was to analyze if ASA-sensitive and ASA-resistant platelets have differences in their apoptotic capability. Clinically stable ischemic coronary patients who had been taking ASA (100 mg/d) for at least 9 months before inclusion were divided into ASA-resistant (n = 11) and ASA-sensitive (n = 13) groups as defined by the PFA-100 test. Platelets from ASA-sensitive patients showed higher expression of the proapoptotic proteins Bak and Bax than those from ASA-resistant patients, although only Bak protein remained different when the results were adjusted by age. In resting platelets, neither caspase-3 activity nor cytosolic cytochrome C levels were different between both experimental groups. Stimulation of platelets with calcium ionophore (10 nmol/L, A23187) increased caspase-3 activity (1.91-fold higher; P < 0.05) and cytosolic cytochrome C levels (1.84-fold higher; P < 0.05) to a higher degree in ASA-sensitive than in ASA-resistant platelets. In conclusion, ASA-sensitive platelets seem to be better prepared to undergo apoptosis during robust platelet activation.

Selected CD133⁺ progenitor cells to promote angiogenesis in patients with refractory angina: final results of the PROGENITOR randomized trial.

RATIONALE: Refractory angina constitutes a clinical problem. OBJECTIVE: The aim of this study was to assess the safety and the feasibility of transendocardial injection of CD133(+) cells to foster angiogenesis in patients with refractory angina. METHODS AND RESULTS: In this randomized, double-blinded, multicenter controlled trial, eligible patients were treated with granulocyte colony-stimulating factor, underwent an apheresis and electromechanical mapping, and were randomized to receive treatment with CD133(+) cells or no treatment. The primary end point was the safety of transendocardial injection of CD133(+) cells, as measured by the occurrence of major adverse cardiac and cerebrovascular event at 6 months. Secondary end points analyzed the efficacy. Twenty-eight patients were included (n=19 treatment; n=9 control). At 6 months, 1 patient in each group had ventricular fibrillation and 1 patient in each group died. One patient (treatment group) had a cardiac tamponade during mapping. There were no significant differences between groups with respect to efficacy parameters; however, the comparison within groups showed a significant improvement in the number of angina episodes per month (median absolute difference, -8.5 [95% confidence interval, -15.0 to -4.0]) and in angina functional class in the treatment arm but not in the control group. At 6 months, only 1 simple-photon emission computed tomography (SPECT) parameter: summed score improved significantly in the treatment group at rest and at stress (median absolute difference, -1.0 [95% confidence interval, -1.9 to -0.1]) but not in the control arm. CONCLUSIONS: Our findings support feasibility and safety of transendocardial injection of CD133(+) cells in patients with refractory angina. The promising clinical results and favorable data observed in SPECT summed score may set up the basis to test the efficacy of cell therapy in a larger randomized trial.

Platelet function in Takotsubo cardiomyopathy.

Takotsubo cardiomyopathy (TK) includes a transient left ventricular dysfunction without obstructive coronary disease, sometimes after stressful situations with elevated cathecolamines. Since catecholamines activate platelets we aimed to study the platelet influence in a TK setting. We included 32 patients with a TK diagnosis, 13 with an acute coronary syndrome (ACS) and 18 healthy volunteers. Once consent informed was obtained, blood samples were extracted and processed (at admission and after 3 months follow-up). Clinical, ecg, echocardiographic and angiographic features were thoroughly recorded.Previous treatment before admission was similar between groups. No differences were observed in clinical features or any of the acute markers studied regarding platelet reactivity between TK compared to ACS. After follow-up, aggregation levels and platelet reactivity showed differences, mainly due to the antithrombotic therapy prescribed at discharge, but similar to volunteers. Circulating epinephrine during the acute phase was significantly higher in TK (p < 0.001). Patients with higher levels of epinephrine had elevated platelet activation and aggregation after 3 months. No differences were observed in Takotsubo acute platelet aggregation compared to patients with ACS, in spite of higher blood levels of adrenaline. Takotsubo patients had elevated platelet aggregation and activation compared with ACS patients at 3 months follow-up because they were less frequently on chronic clopidogrel and ASA. However, they had similar platelet aggregation and activation levels to healthy volunteers despite treatment with low-dose ASA. Takotsubo patients who had higher levels of adrenaline in the acute phase displayed increased platelet reactivity during follow-up.

Influence of HbA1c levels on platelet function profiles associated with tight glycemic control in patients presenting with hyperglycemia and an acute coronary syndrome. A subanalysis of the CHIPS Study ("Control de HIperglucemia y Actividad Plaquetaria en Pacientes con Síndrome Coronario Agudo").

Patients with hyperglycemia, an acute coronary syndrome and poor glycemic control have increased platelet reactivity and poor prognosis. However, it is unclear the influence of a tight glycemic control on platelet reactivity in these patients. This is a subanalysis of the CHIPS study. This trial randomized patients with hyperglycemia to undergo an intensive glucose control (target blood glucose 80-120 mg/dL), or conventional glucose control (target blood glucose <180 mg/dL). We analyzed platelet function at discharge on the subgroup of patients with poor glycemic control, defined with admission levels of HbA1c higher than 6.5%. The primary endpoint was maximal platelet aggregation following stimuli with 20 µM ADP. We also measured aggregation following collagen, epinephrine, and thrombin receptor-activated peptide, as well as P2Y12 reactivity index and surface expression of glycoprotein IIb/IIIa and P-selectin. A total of 67 patients presented HbA1c ≥ 6.5% (37 intensive, 30 conventional), while 42 had HbA1c < 6.5% (20 intensive, 22 conventional). There were no differences in baseline characteristics between groups. At discharge, patients with HbA1c ≥6.5% had significantly reduced MPA with intensive glucose control compared with conventional control (46.1 ± 22.3 vs. 60.4 ± 20.0%; p = 0.004). Similar findings were shown with other measures of platelet function. However, glucose control strategy did not affect platelet function parameters in patients with HbA1c < 6.5%. Intensive glucose control in patients presenting with an acute coronary syndrome and hyperglycemia results in a reduction of platelet reactivity only in the presence of elevated HbA1c levels.

Can resistance to aspirin be reversed after an additional dose?

Aspirin resistance or aspirin non-responsiveness is a recently described phenomenon which has been consistently associated with an increased risk of cardiovascular events. This study was designed to determine the effects of an additional dose of 100 mg of aspirin on platelet function and proportion of aspirin non-responders using the platelet function analyzer-100 (PFA-100), in a well characterized population of stable coronary heart disease patients already on long-term aspirin treatment. Platelet function was assessed using PFA-100 in 141 patients (64.8 ± 10.1 years, 87.9% men) on long-term aspirin treatment (100 mg/day) before and 1 h after "in site" oral aspirin administration (100 mg). Prevalence of aspirin non-responders using PFA-100 was 50.7% (95% confidence interval 42.4-59). One hour after 100 mg of oral aspirin, reassessment of aspirin effects showed a prevalence of non-responders using PFA of 35.0% (95% CI 27.3-43.2) (P < 0.001 vs. pre-dose proportion). Using the PFA-100 system, reassessment of platelet function following oral administration of daily aspirin dosage significantly reduces the number of stable coronary disease patients considered to be non-responders to such treatment.

Serum Metabolomic Analysis Suggests Impairment of Myocardial Energy Production in Takotsubo Syndrome.

INTRODUCTION: Takotsubo syndrome is a complex entity that, although it usually has a good prognosis, can be life threatening. While recent advances have improved the knowledge of takotsubo syndrome, many aspects of its etiology still remain uncertain. Metabolomics, a hypothesis generating approach, could provide novel pathophysiology information about this disease. METHODS AND RESULTS: Serum samples were obtained from takotsubo (n = 19) and acute myocardial infarction patients (n = 8) at the cath lab and, in the case of takotsubo, again once the patient had recovered, 3 months after the main event. 1H NMR spectra of the serum were acquired at 9.4T using a CPMG pulse sequence (32 ms effective delay). Supervised and unsupervised pattern recognition approaches where applied to the data. Pattern recognition was able to differentiate between takotsubo and acute myocardial infarction during the acute phase with 95% accuracy. Myocardial infarction patients showed an increase in lipid signals, a known risk factor for the disease while takotsubo patients showed a relative increase in acetate that could suggest a reduced turnover of the Krebs cycle. When comparing acute and recovered phases, we could detect an increase in alanine and creatine once patients recovered. CONCLUSIONS: Our results demonstrate that takotsubo syndrome is metabolically different than AMI, showing limited myocardial energy production capacity during the acute phase. We achieved high classification success against AMI; however, this study should be considered as a proof of concept regarding clinical application of metabolic profiling in takotsubo cardiomyopathy.

Randomized comparison of a high clopidogrel maintenance dose in patients with diabetes mellitus and coronary artery disease: results of the Optimizing Antiplatelet Therapy in Diabetes Mellitus (OPTIMUS) study.

BACKGROUND: After treatment with clopidogrel, patients with type 2 diabetes mellitus (T2DM) have reduced platelet inhibition compared with patients who are not diabetic. Whether platelet inhibition can be enhanced by increasing clopidogrel maintenance dosage in T2DM patients is unknown. The aim of this pilot study was to assess the functional impact of a high maintenance dose in T2DM patients with suboptimal clopidogrel-induced antiplatelet effects. METHODS AND RESULTS: T2DM patients on chronic dual antiplatelet therapy were screened to identify suboptimal clopidogrel responders. The latter were randomized to 30-day treatment with a standard (75 mg; n=20) or high (150 mg; n=20) daily maintenance dose. Platelet function was assessed at 3 time points: baseline, 30 days after randomization, and 30 days after resuming standard dosing. Platelet function parameters included adenosine diphosphate-induced (20 and 5 micromol/L) maximal and late platelet aggregation, inhibition of platelet aggregation, platelet disaggregation, and P2Y12 reactivity index. A total of 64 T2DM patients were screened to identify 40 suboptimal responders. After randomization, maximal adenosine diphosphate-induced (20 micromol/L) platelet aggregation was significantly reduced in the 150-mg group compared with the 75-mg group (P=0.002; primary end point). However, suboptimal clopidogrel response was still present in 60% of patients on the 150-mg regimen. All other platelet function parameters showed enhanced clopidogrel-induced antiplatelet effects with 150 mg, which returned to baseline values after resumption of standard dosing. CONCLUSIONS: A 150-mg maintenance dose of clopidogrel is associated with enhanced antiplatelet effects compared with 75 mg in high-risk T2DM patients. However, enhanced ex vivo platelet reactivity continues to persist, the clinical implications of which are unknown and need to be evaluated in large-scale clinical trials.

Functional impact of high clopidogrel maintenance dosing in patients undergoing elective percutaneous coronary interventions. Results of a randomized study.

The currently recommended maintenance dose of clopidogrel is often associated with inadequate platelet inhibition, suggesting the need for a higher dose. The aim of this pilot study was to assess the functional impact of a high (150 mg/day) maintenance dose of clopidogrel in patients undergoing elective percutaneous coronary intervention (PCI). This is a prospective, randomized, platelet function study which was performed in elective PCI patients assigned to treatment with either a 75 mg (n = 20) or 150 mg (n = 20) daily maintenance dose of clopidogrel for 30 days; afterwards, all patients resumed standard dosing. Platelet aggregation was performed using light transmittance aggregometry following 20 microM and 5 microM adenosine diphosphate (ADP) stimuli 30 days after randomization and 30 days after resuming standard dosing. Patients treated with 150 mg/day clopidogrel had lower 20 microM ADP-induced platelet aggregation compared to patients on 75 mg/day (52.1 +/- 9% vs. 64.0 +/- 8%; p < 0.001; primary endpoint). The dose-dependent effect was confirmed by the absolute and relative increase in platelet aggregation after resuming standard dosing (p < 0.001). No changes were observed in patients randomized to standard dosing. Parallel findings were observed following 5 microM ADP stimuli for all assessments. A broad variability in clopidogrel-induced antiplatelet effects was observed irrespective of dosing. In conclusion, a 150 mg/day maintenance dose regimen of clopidogrel is associated with reduced platelet reactivity and enhanced platelet inhibition compared to that achieved with the currently recommended 75 mg/day in patients undergoing elective PCI.

Functional effects of high clopidogrel maintenance dosing in patients with inadequate platelet inhibition on standard dose treatment.

Updated guidelines on percutaneous coronary intervention recommend increasing the dose of clopidogrel to 150 mg in high-risk patients if <50% platelet inhibition is demonstrated. However, to date, the functional impact of this recommendation has been poorly explored. The aim of this study was to assess the functional implications associated with the use of clopidogrel 150 mg/day in patients with inadequate platelet inhibition while receiving standard 75 mg/day maintenance treatment. Patients with diabetes mellitus have a higher prevalence of inadequate clopidogrel-induced antiplatelet effects and stent thrombosis compared with those without diabetes and were selected for this analysis. Platelet inhibition was assessed using the VerifyNow P2Y12 assay in patients with type 2 diabetes receiving dual-antiplatelet therapy. Patients (n = 17) with <50% platelet inhibition were treated with clopidogrel 150 mg/day for 1 month. Adenosine diphosphate-induced aggregation and the P2Y12 reactivity ratio were also assessed. Platelet function profiles were compared with that of a control group (n = 17) with >or=50% inhibition. Platelet inhibition increased from 27.1 +/- 12% to 40.6 +/- 18% in patients treated with clopidogrel 150 mg/day (p = 0.009; primary end point). All other functional measures also showed enhanced clopidogrel-induced antiplatelet effects. The degree of platelet inhibition achieved after treatment with clopidogrel 150 mg/day varied broadly, and only 35% of patients yielded a degree of platelet inhibition >or=50%. Increasing the dose in patients with inadequate response to clopidogrel did not reach the same degree of antiplatelet effects as those achieved in patients with adequate response while receiving 75 mg/day. In conclusion, the use of a 150 mg maintenance dose of clopidogrel in patients with type 2 diabetes with <50% platelet inhibition is associated with enhanced antiplatelet effects. However, the antiplatelet effects achieved are nonuniform, and a considerable number of patients persist with inadequate platelet inhibition.

Clopidogrel withdrawal is associated with proinflammatory and prothrombotic effects in patients with diabetes and coronary artery disease.

Inhibition of the P2Y12 pathway by the platelet antagonist clopidogrel is associated with a marked reduction in platelet reactivity. Recent reports have shown that P2Y12 inhibition has anti-inflammatory effects as well. However, whether clopidogrel withdrawal is associated with proaggregatory and proinflammatory effects has not yet been explored. Since diabetic subjects are characterized by a prothrombotic and proinflammatory status, we hypothesize that these patients may be more vulnerable to these effects. A total 54 patients with diabetes on long-term (12 months) dual antiplatelet therapy (aspirin plus clopidogrel) were studied. Platelet aggregation (following 6 and 20 micromol/l ADP stimuli) and inflammatory markers (C-reactive protein and P-selectin expression) were assessed before and 1 month following clopidogrel withdrawal. Following clopidogrel withdrawal, aspirin responsiveness using platelet function analyzer-100 was determined as well. A significant increase in all the assessed platelet (P < 0.0001 for 6 and 20 micromol/l ADP-induced aggregation) and inflammatory (P < 0.05 for C-reactive protein, P < 0.001 for P-selectin expression in resting platelets, and P < 0.0001 for P-selectin expression in ADP-stimulated platelets) biomarkers was observed following clopidogrel withdrawal. Low responders to aspirin had increased platelet aggregation profiles (P < 0.05 for 6 and 20 micromol/l ADP-induced aggregation) but no differences in inflammatory markers. In conclusion, clopidogrel withdrawal is associated with an increase in platelet and inflammatory biomarkers in diabetic patients, supporting pleiotropic effects coupled with P2Y12 receptor antagonism.

Contribution of gene sequence variations of the hepatic cytochrome P450 3A4 enzyme to variability in individual responsiveness to clopidogrel.

OBJECTIVE: Metabolic activity of cytochrome P450 (CYP) 3A4 has been associated with clopidogrel response variability. Because metabolic activity of CYP3A4 is genetically regulated, we hypothesized that genetic variations of this enzyme may contribute to clopidogrel response variability. METHODS AND RESULTS: The CYP3A4*1B, CYP3A4*3, IVS7+258A>G, IVS7+894C>T, and IVS10+12G>A polymorphisms of the CYP3A4 gene were assessed in 82 patients in a steady phase of clopidogrel therapy. Glycoprotein (platelet glycoprotein (GP) IIb/IIIa receptor activation and platelet aggregation were assessed. A cohort of 45 clopidogrel-naïve patients was studied to determine the modulating effects of these polymorphisms after loading dose (300 mg) administration. Only the IVS7+258A>G, IVS7+894C>T, and IVS10+12G>A polymorphisms were sufficiently polymorphic. During the steady phase of clopidogrel treatment, IVS10+12A allele carriers had reduced GP IIb/IIIa activation (P=0.025) and better responsiveness (P=0.02); similarly, clopidogrel-naïve patients carriers of the IVS10+12A allele had reduced GP IIb/IIIa activation during the first 24 hours after a loading dose (P=0.025), increased platelet inhibition (P=0.006), and a more optimal drug response (P=0.003). This polymorphism did not influence platelet aggregation profiles. No association was observed between the other polymorphisms and clopidogrel responsiveness. CONCLUSIONS: The IVS10+12G>A polymorphism of the CYP3A4 gene modulates platelet activation in patients treated with clopidogrel and may therefore contribute to clopidogrel response variability.

Neutrophil stunning by metoprolol reduces infarct size.

The ß1-adrenergic-receptor (ADRB1) antagonist metoprolol reduces infarct size in acute myocardial infarction (AMI) patients. The prevailing view has been that metoprolol acts mainly on cardiomyocytes. Here, we demonstrate that metoprolol reduces reperfusion injury by targeting the haematopoietic compartment. Metoprolol inhibits neutrophil migration in an ADRB1-dependent manner. Metoprolol acts during early phases of neutrophil recruitment by impairing structural and functional rearrangements needed for productive engagement of circulating platelets, resulting in erratic intravascular dynamics and blunted inflammation. Depletion of neutrophils, ablation of Adrb1 in haematopoietic cells, or blockade of PSGL-1, the receptor involved in neutrophil-platelet interactions, fully abrogated metoprolol's infarct-limiting effects. The association between neutrophil count and microvascular obstruction is abolished in metoprolol-treated AMI patients. Metoprolol inhibits neutrophil-platelet interactions in AMI patients by targeting neutrophils. Identification of the relevant role of ADRB1 in haematopoietic cells during acute injury and the protective role upon its modulation offers potential for developing new therapeutic strategies.

Platelet function profiles in patients with type 2 diabetes and coronary artery disease on combined aspirin and clopidogrel treatment.

To assess platelet function profiles in diabetic and nondiabetic patients on aspirin and clopidogrel therapy, two patient populations were included to investigate the 1) acute effects of a 300-mg clopidogrel loading dose (group 1, n = 52) and 2) long-term effects of clopidogrel (group 2, n = 120) on platelet function in diabetic compared with nondiabetic patients already on aspirin treatment. Patients were stratified according to the presence of type 2 diabetes. Platelet aggregation was assessed using light transmittance aggregometry (groups 1 and 2). Platelet activation (P-selectin expression and PAC-1 binding) was determined using whole-blood flow cytometry (group 2). Clopidogrel response was also assessed. In group 1, platelet aggregation was significantly increased in diabetic (n = 16) compared with nondiabetic (n = 36) patients at baseline and up to 24 h following a 300-mg loading dose (P = 0.005). In group 2, platelet aggregation and activation were increased in diabetic (n = 60) compared with nondiabetic (n = 60) subjects (P < 0.05 for all platelet function assays). Diabetic subjects had a higher number of clopidogrel nonresponders (P = 0.04). Diabetic patients have increased platelet reactivity compared with nondiabetic subjects on combined aspirin and clopidogrel treatment. Reduced sensitivity to antiplatelet drugs may contribute to the increased atherothombotic risk in diabetic patients.

Influence of aspirin resistance on platelet function profiles in patients on long-term aspirin and clopidogrel after percutaneous coronary intervention.

Increased platelet inhibition is achieved when clopidogrel is added to aspirin (acetylsalicylic acid [ASA]). A broad variability in platelet inhibition profiles during the early phases of treatment has been demonstrated and may be attributed to ASA resistance. However, the influence of ASA sensitivity on platelet function profiles of patients on long-term dual antiplatelet therapy has yet to be explored. A total of 135 patients who had previously undergone percutaneous coronary intervention on long-term (>1 month) ASA and clopidogrel therapy was included. The PFA-100 system was used to define ASA resistance. Platelet aggregation, after adenosine diphosphate (6 and 20 micromol/L) and collagen (6 microg/ml) stimuli, and platelet activation (glycoprotein IIb/IIIa activation and P-selectin expression), after adenosine diphosphate (2 micromol/L) and thrombin receptor-activating peptide (50 micromol/L) stimuli, were assessed by light transmittance aggregometry and flow cytometry, respectively. Patient variability in response to treatment was defined by the coefficient of variability. ASA resistance was found in 60 of 135 patients (44%). Patients with diabetes were more frequently ASA resistant. Collagen/epinephrine- and collagen/adenosine diphosphate-coated cartridges on the PFA-100 had shorter closure times in the ASA-resistant population compared with ASA-sensitive patients. Platelet aggregation and activation were significantly higher in ASA-resistant patients. A broad variability (coefficient of variation >0.25) in patient response to treatment was observed in ASA-resistant and -sensitive patients. In conclusion, ASA resistance is associated with increased platelet reactivity in patients on long-term dual antiplatelet treatment.

Influence of the CD14 C260T promoter polymorphism on C-reactive protein levels in patients with coronary artery disease.

The CD14 receptor is an important mediator of inflammatory reactions, and its expression is under genetic control. The allelic variant of the C260T polymorphism located in the promoter region of the CD14 gene is associated with receptor expression and ischemic risk. To date, most studies assessing the functional implications of the C260T polymorphism have been performed under proinflammatory conditions (e.g., acute coronary syndromes), and whether gene sequence variations of the CD14 receptor have any functional effect on systemic inflammation in patients in a stable phase of their atherosclerotic disease process is unknown. Eighty-two patients with stable coronary artery disease were studied. High-sensitivity C-reactive protein (hs-CRP) was used as a measurement of systemic inflammation. The genotype distribution of the C260T polymorphism of the CD14 gene was as follows: CC in 18 of 82 patients (22%), TC in 48 of 82 patients (58.5%), and TT in 16 of 82 patients (19.5%). TT subjects had increased hs-CRP levels compared with carriers of the C allele (p = 0.04). A higher percentage of T allele homozygotes had hs-CRP levels >0.3 mg/dl (p = 0.01). Homozygosis status of the T allele was independently associated with hs-CRP levels >0.3 mg/dl (p = 0.004). In conclusion, these observations may support the findings in large-scale studies that T homozygotes of this functional polymorphism are at increased ischemic risk.

Variability in platelet aggregation following sustained aspirin and clopidogrel treatment in patients with coronary heart disease and influence of the 807 C/T polymorphism of the glycoprotein Ia gene.

A broad variability in patient response to dual antiplatelet treatment has been described during the first month of treatment. Data on platelet function profiles in patients on dual antiplatelet therapy for a more sustained period are limited. Whether gene sequence variations of the glycoprotein Ia/IIa receptor influence platelet aggregation in these patients is also unknown. The aim of this study was to characterize platelet aggregation profiles in patients on dual antiplatelet treatment (aspirin plus clopidogrel) for >1 month and to assess whether these may be influenced by the C807T polymorphism of the glycoprotein Ia gene. We included 82 patients, who were divided into 2 groups: carriers (CT + TT genotypes; n = 51) and noncarriers (CC genotype; n = 31) of the mutant T allele. Platelet aggregation was assessed using light transmittance aggregometry after stimuli with adenosine diphosphate (20 micromol/L), collagen (6 microg/ml), and epinephrine (20 micromol/L). A significant variability in the distribution of platelet aggregation was observed in the overall study population, as well as in carriers and noncarriers of the T allele. T allele carriers had increased platelet aggregation compared with noncarriers after stimuli with adenosine diphosphate, collagen, and epinephrine (p <0.05 for all platelet aggregation assays). Thus, platelet aggregation varied significantly in patients on long-term dual antiplatelet treatment and was increased in T allele carriers of the 807C/T polymorphism of the glycoprotein Ia gene. These findings may contribute to the increased ischemic risk observed in these patients.

Identification of low responders to a 300-mg clopidogrel loading dose in patients undergoing coronary stenting.

BACKGROUND: Although patients undergoing coronary stenting routinely receive dual antiplatelet treatment to reduce the risk of stent thrombosis, this undesired event still occurs. A suboptimal response to clopidogrel treatment (low responders) has been suggested to contribute to stent thrombosis. In the present study, platelet function profiles were assessed in patients undergoing coronary stenting receiving a standard 300-mg clopidogrel loading dose with the aim to identify low clopidogrel responders. MATERIALS AND METHODS: Platelet aggregation was assessed by light transmittance aggregometry following 6 microM ADP stimuli in 48 patients before and 10 min, 4 and 24 h after receiving clopidogrel front-loading. Patients having > or =40% inhibition of platelet aggregation 24 h after clopidogrel administration were defined as normal responders, whereas those having <40% inhibition were low responders. Glycoprotein (GP) IIb/IIIa activation and P-selectin expression were assessed by whole blood flow cytometry following 2 microM ADP stimuli at the same time points. Platelet function profiles were compared between normal and low clopidogrel responders. RESULTS: Twenty-seven patients (56%) were normal responders and 21 (44%) low responders. Baseline GP IIb/IIIa activation was higher in low responders (74.6+/-16.6% vs. 58.2+/-24.5%, p=0.03). Although GP IIb/IIIa activation reduced following clopidogrel front-loading in both groups, it remained increased among low responders at 24 h (58.6+/-21.3% vs. 40.2+/-28.7%, p=0.05) and during the overall study time course (p=0.02). There were no differences in P-selectin expression. CONCLUSIONS: A considerable proportion of patients have an early suboptimal response to a 300-mg clopidogrel loading dose. An increased GP IIb/IIIa activation before intervention may identify this group of patients suggesting the use of a more aggressive antithrombotic treatment in these individuals.

Lack of association between the P2Y12 receptor gene polymorphism and platelet response to clopidogrel in patients with coronary artery disease.

INTRODUCTION: Clopidogrel inhibits the ADP subtype P2Y(12) receptor. Recently, polymorphisms of this receptor have been associated with different degrees of platelet aggregation in healthy volunteers and have been suggested to modulate clopidogrel response. However, the role of gene sequence variations of the P2Y(12) receptor in patients treated with clopidogrel has not yet been assessed. MATERIALS AND METHODS: The T744C polymorphism of the P2Y(12) receptor gene was assessed in 119 patients: 36 undergoing coronary stenting receiving a 300 mg loading dose (Group A) and 83 on long-term clopidogrel (75 mg/day) treatment (Group B). Patients were divided into 2 subgroups according to the presence or absence of the C allele: carriers (CT heterozygotes and CC homozygotes) and non-carriers (TT homozygotes). Platelet aggregation, assessed by light transmittance aggregometry following ADP, collagen, TRAP and epinephrine stimuli, and platelet activation (GP IIb/IIIa activation and P-selectin expression), assessed by whole blood flow cytometry in ADP and TRAP-stimulated platelets, were performed. Platelet function was assessed at baseline and 4 and 24 h following clopidogrel loading dose in Group A and when patients where on clopidogrel treatment for at least 1 month in Group B. RESULTS: The genotype distribution of Group A was: 22/36 (61.1%) non-carriers and 14/36 (38.9%) carriers of the C allele; Group B: 57/83 (68.7%) non-carriers and 26/83 (31.3%) carriers of the C allele. There were no differences between groups for all the assessed platelet function assays. CONCLUSIONS: The T744C polymorphism of the P2Y(12) receptor gene does not modulate platelet response to clopidogrel either in the early or long-term phases of treatment. This specific gene polymorphism alone is therefore unlikely to be the cause of variability in individual response to antiplatelet therapy.