Lack of evidence for pleiotropic effects of clopidogrel on endothelial function and inflammation in patients with stable coronary artery disease: results of the double-blind, randomized CASSANDRA study

Effects of Clopidogrel, Prasugrel and Ticagrelor on Microvascular Function and Platelet Reactivity in Patients With Acute Coronary Syndrome Undergoing Coronary Artery Stenting. A Randomized, Blinded, Parallel Group Trial

Aims: In this pre-specified analysis of the "endothelium, stent and antiplatelet therapy" study, we investigate the impact of antiplatelet therapies on microvascular function in patients undergoing stenting for an acute coronary syndrome. Methods and Results: Fifty-six patients [age: 63(55-67) years, males, 10 diabetics, 27 non-ST-elevation myocardial infarction] were randomized to receive clopidogrel, ticagrelor or prasugrel in form of oral loading 2 h before stenting followed by oral therapy. Investigators were blinded to the allocation. Laser-Doppler microvascular function and ADP-induced platelet aggregation capacity were measured at baseline, 2 h after oral antiplatelet loading, and 1 day, 1 week and 1 month after stenting during chronic therapy with the same antiplatelet agent. Platelet aggregation decreased in all groups 2 h after oral loading, with a significantly larger effect in the prasugrel group (P = 0.009). Similarly, prasugrel and ticagrelor loading was followed by an increase in microvascular reactive hyperemia (P = 0.007 and P = 0.042 compared to clopidogrel). This effect disappeared one day after coronary intervention, with a significant decrease in the prasugrel group (P = 0.026). Similarly, analysis of microvascular conductance showed a larger increase in the prasugrel group 2 h after loading (P = 0.022 among groups), and a decrease in all groups after stenting. Conclusions: Oral loading with prasugrel (and less consistently ticagrelor) is associated with improved microvascular function and stronger platelet inhibition in acute coronary syndrome patients. The microvascular effect was however lost 1 day after stenting and during subsequent follow-up. Further studies are necessary to clarify the the long-term effects and potential benefits of P2Y12 inhibitors on microvascular damage. ClINICALTRIALS.gov N°: NCT01700322 EUDRACT-N°: 2011-005305-73.

Effects of clopidogrel vs. prasugrel vs. ticagrelor on endothelial function, inflammatory parameters, and platelet function in patients with acute coronary syndrome undergoing coronary artery stenting: a randomized, blinded, parallel study

AIMS

In a randomized, parallel, blinded study, we investigate the impact of clopidogrel, prasugrel, or ticagrelor on peripheral endothelial function in patients undergoing stenting for an acute coronary syndrome.

METHODS AND RESULTS

The primary endpoint of the study was the change in endothelium-dependent flow-mediated dilation (FMD) following stenting. A total of 90 patients (age 62 ± 9 years, 81 males, 22 diabetics, 49 non-ST elevation myocardial infarctions) were enrolled. There were no significant differences among groups in any clinical parameter. Acutely before stenting, all three drugs improved FMD without differences between groups (P = 0.73). Stenting blunted FMD in the clopidogrel and ticagrelor group (both P < 0.01), but not in the prasugrel group. During follow-up, prasugrel was superior to clopidogrel [mean difference 2.13, 95% confidence interval (CI) 0.68-3.58; P = 0.0047] and ticagrelor (mean difference 1.57, 95% CI 0.31-2.83; P = 0.0155), but this difference was limited to patients who received the study therapy 2 h before stenting. Ticagrelor was not significantly superior to clopidogrel (mean difference 0.55, 95% CI -0.73 to 1.82; P = 0.39). No significant differences were seen among groups for low-flow-mediated dilation. Plasma interleukin (IL)-6 (P = 0.02 and P = 0.01, respectively) and platelet aggregation reactivity in response to adenosine diphosphate (P = 0.002 and P = 0.035) were lower in the prasugrel compared to clopidogrel and ticagrelor group.

CONCLUSION

As compared to ticagrelor and clopidogrel, therapy with prasugrel in patients undergoing stenting for an acute coronary syndrome is associated with improved endothelial function, stronger platelet inhibition, and reduced IL-6 levels, all of which may have prognostic implications. This effect was lost in patients who received the study medication immediately after stenting.

EUDRACT-NO

2011-005305-73.

Coronary Artery Disease and Endothelial Dysfunction: Novel Diagnostic and Therapeutic Approaches

Coronary artery disease is the leading cause of morbidity and mortality worldwide. The most common pathophysiologic substrate is atherosclerosis which is an inflammatory procedure that starts at childhood and develops throughout life. Endothelial dysfunction is associated with the initiation and progression of atherosclerosis and is characterized by the impaired production of nitric oxide. In general, endothelial dysfunction is linked to poor cardiovascular prognosis and different methods, both invasive and non-invasive, have been developed for its evaluation. Ultrasound evaluation of flow mediated dilatation of the branchial artery is the most commonly used method to assessed endothelial function while intracoronary administration of vasoactive agents may be also be used to test directly endothelial properties of the coronary vasculature. Endothelial dysfunction has also been the subject of therapeutic interventions. This review article summarizes the knowledge about evaluation of endothelial function in acute coronary syndromes and stable coronary artery disease and demonstrates the current therapeutic approaches against endothelial dysfunction.

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

Interaction between platelets and endothelium: from pathophysiology to new therapeutic options

Platelets were traditionally considered to purely have a role in the maintenance of haemostasis. Recently their role in vasomotor function, inflammation and atherosclerosis has been very well-recognized. Endothelium which was originally considered as a simple passive barrier, it is now viewed as an organ whose normal functioning is crucial for maintaining vascular health. When endothelial balance is disturbed, vascular disease initiates. Platelet interactions with endothelium have an important contribution in this process. Low-grade inflammation, endothelial dysfunction, and platelet hyper-reactivity are all independently associated with an increased risk of cardiovascular events. Older antiplatelet agents like aspirin and clopidogrel and newer more potent agents like prasugrel and ticagrelor have been proven effective in all the clinical spectrum of coronary artery disease patients. Current antiplatelet medications and especially newer generation P2Y12 inhibitor ticagrelor, offer clinical benefits not only due to their well-recognized antithrombotic effect, but also via the attenuation of platelet inflammatory action, impediment of P2Y12 activation effects in other cells and through other complex and sometimes undefined pathways. Future research is expected to better define platelet-endothelium interactions and the multiple impact of current antiplatelet therapy on them.

Prasugrel as opposed to clopidogrel improves endothelial nitric oxide bioavailability and reduces platelet-leukocyte interaction in patients with unstable angina pectoris: A randomized controlled trial

BACKGROUND

Platelet inhibition has been linked to improved endothelial function, a prognostic factor in coronary artery disease. Whether prasugrel, a potent platelet inhibitor, affects endothelial function remains unknown.

METHODS

This was a double-blind, randomized, active-controlled, parallel trial. Patients with unstable angina pectoris undergoing percutaneous coronary intervention (PCI) received either a daily dose of clopidogrel 75mg (n=23) or prasugrel 10mg (n=22). Flow-mediated dilation (FMD), circulating nitrate and nitrite, inflammatory markers and platelet-leukocyte aggregates (PLAs) were assessed the day after PCI and after 3months.

RESULTS

Baseline patient demographics were well matched between treatment groups. Prasugrel led to a significant improvement of FMD after 3months (9.01±3.64% vs. 6.65±3.24%, p=0.001). In contrast, no significant change was observed in the clopidogrel group (7.21±2.84% vs. 6.30±2.97%, p=0.187). Adjusted for baseline FMD, hyperlipidemia and statin use, the treatment effect on change in FMD favoured prasugrel by an absolute 1.97% (95% CI 0.29% to 3.66%, p=0.023). A significant reduction of plasma hsCRP, myeloperoxidase and neutrophil elastase and an increase of nitrate levels were noted in both treatment arms. Interestingly, only prasugrel significantly reduced sCD40 ligand and RANTES and increased nitrite levels. Prasugrel reduced the ADP-stimulated increase in PLAs by 40% (IR: 82 to 13), whereas clopidogrel revealed no such effect (1% increase (IR: 13 to 50) (p=0.01).

CONCLUSION

Prasugrel exhibits beneficial mid-term effects on endothelial nitric oxide bioavailability and inflammatory markers. (EudraCT number: 2009-015406-19).

Relationship between monocyte-platelet aggregation and endothelial function in middle-aged and elderly adults

Low-grade inflammation, endothelial dysfunction, and platelet hyper-reactivity to agonists are associated with an increased risk of cardiovascular events. In vitro and animal studies infer an inverse mechanistic relationship between platelet activation and the production of endothelium-derived nitric oxide and prostacyclin. This concept is supported by evidence of an inverse relationship between endothelial function and platelet activation in high-risk cardiac patients. The aim of this study was to investigate what relationship, if any, exists between platelet and endothelial function in healthy, middle-aged, and elderly adults. In 51 participants (18 male, 33 post menopausal female), endothelial function was assessed by flow-mediated dilation (FMD). Platelet function was assessed by flow cytometric determination of glycoprotein IIb/IIIa activation (measured by PAC-1 binding), granule exocytosis (measured by surface P-selectin expression), and monocyte-platelet aggregates (MPAs), with and without stimulation by canonical platelet agonists adenosine diphosphate (ADP), arachidonic acid (AA), and collagen. Correlation analysis indicated there was no significant (all P => 0.05) relationship between FMD and any marker of in vivo platelet activation (MPAs R = 0.193, PAC-1 R = -0.113, anti-CD62P R = -0.078) or inducible platelet activation by ADP (MPA R = -0.128, anti-CD62P R = -0.237), AA (MPA R = -0.122, PAC-1 R = -0.045, anti-CD62P R = -0.142), or collagen (MPA R = 0.136, PAC-1 R = 0.174, anti-CD62P R = -0.077). Our findings contrast with two previous studies performed in high-risk cardiac patients, which reported inverse relationships between platelet activation and endothelial function, suggesting that some compensatory redundancy may exist in the relationship between platelet and endothelial function in preclinical populations.

Clopidogrel Improves Skin Microcirculatory Endothelial Function in Persons With Heightened Platelet Aggregation

Background

Platelet activation can lead to enhanced oxidative stress, inflammatory response, and endothelial dysfunction. To quantify the effects of platelet inhibition on endothelial function, we assessed platelet activity of healthy persons before and after clopidogrel administration and evaluated its effects on endothelial function. We hypothesized that clopidogrel, by attenuating platelet activity, would result in enhanced endothelial function.

Methods and Results

Microcirculatory endothelial function was quantified by laser Doppler flowmetry (LDF) mediated by thermal hyperemia (TH) and postocclusive reactive hyperemia, respectively, in 287 and 241 relatively healthy and homogenous Old Order Amish persons. LDF and platelet aggregation measures were obtained at baseline and after 7 days of clopidogrel administration. Our primary outcome was percentage change in post‐ versus preclopidogrel LDF measures. Preclopidogrel TH‐LDF and platelet aggregation were higher in women than in men (P<0.001). Clopidogrel administration was associated with ≈2‐fold higher percentage change in TH‐LDF in participants with high versus low baseline platelet aggregation (39.4±10.1% versus 17.4±5.6%, P=0.03). Clopidogrel also increased absolute TH‐LDF measures in persons with high platelet aggregation (1757±766 to 2154±1055, P=0.03), with a more prominent effect in women (1909±846 to 2518±1048, P=0.001). There was no evidence that clopidogrel influenced postocclusive reactive hyperemia LDF measures.

Conclusions

The administration of clopidogrel in healthy persons with high baseline platelet aggregation results in improved TH‐induced microcirculatory endothelial function. These data suggest that clopidogrel may have a beneficial effect on microcirculatory endothelial function, presumably through antiplatelet activity, and may confer additional vascular benefits.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00799396.

Effects of P2Y12 receptor antagonists beyond platelet inhibition--comparison of ticagrelor with thienopyridines

The effect and clinical benefit of P2Y12 receptor antagonists may not be limited to platelet inhibition and the prevention of arterial thrombus formation. Potential additional effects include reduction of the pro-inflammatory role of activated platelets and effects related to P2Y12 receptor inhibition on other cells apart from platelets. P2Y12 receptor antagonists, thienopyridines and ticagrelor, differ in their mode of action being prodrugs instead of direct acting and irreversibly instead of reversibly binding to P2Y12 . These key differences may provide different potential when it comes to additional effects. In addition to P2Y12 receptor blockade, ticagrelor is unique in having the only well-documented additional target of inhibition, the equilibrative nucleoside transporter 1. The current review will address the effects of P2Y12 receptor antagonists beyond platelets and the protection against arterial thrombosis. The discussion will include the potential for thienopyridines and ticagrelor to mediate anti-inflammatory effects, to conserve vascular function, to affect atherosclerosis, to provide cardioprotection and to induce dyspnea.

The platelet P2 receptors in inflammation

In addition to their well characterized and established role in haemostasis and thrombosis, platelets contribute to the pathogenesis of inflammation. Adenine nucleotides are signalling molecules that regulate the function of virtually every cell in the body, by interacting with P2 receptors. Their important role in inflammation is well established. In the last few years, the pro-inflammatory roles of adenine nucleotides interacting with their platelet P2 receptors has emerged. In particular, it was shown that the platelet P2Y12 receptor for ADP significantly contributed to the pro-inflammatory effects of cysteinyl leukotrienes (CysLT) in experimental models of asthma in mice. More importantly, it was recently shown that P2Y12 variants were associated with lung function in a large family-based asthma cohort and that the P2Y12 antagonist prasugrel tended to decrease bronchial hyper-reactivity to mannitol in patients with allergic bronchial asthma in a randomized, placebo controlled trial.

CONCLUSION

These data strongly suggest that P2Y12 may represent an important pharmacological target for the treatment of patients with allergic bronchial asthma.

Effects of clopidogrel, prasugrel and ticagrelor on endothelial function, inflammatory and oxidative stress parameters and platelet function in patients undergoing coronary artery stenting for an acute coronary syndrome. A randomised, prospective, controlled study

INTRODUCTION

Particularly in the setting of acute coronary syndromes, the interplay between vascular and platelet function has been postulated to have direct clinical implications. The present trial is designed to test the effect of clopidogrel, prasugrel and ticagrelor on multiple parameters of vascular function, platelet aggregation, oxidative and inflammatory stress before and up to 4 weeks after coronary artery stenting.

METHODS AND ANALYSIS

The study is designed as a three-arm, parallel design, randomised, investigator-blinded study. Patients with unstable angina or non-ST elevation myocardial infarction undergoing coronary intervention with a drug-eluting stent will be randomised to receive 600 mg clopidogrel, 60 mg prasugrel or 180 mg ticagrelor followed by oral therapy with the same drug. The primary endpoint of the trial is the impact of antiplatelet treatments on endothelial function as assessed by flow-mediated dilation at 1 day, 1 week and 1 month in patients who have undergone stenting. Secondary endpoints include the impact of study medications on parameters of macrovascular and microvascular function, platelet reactivity, oxidative and inflammatory stress. The study recruitment is currently ongoing and, after an interim analysis which was performed at 50% of the initially planned population, it is planned to continue until July 2015.

ETHICS AND DISSEMINATION

The protocol was approved by the local ethics committee. The trial will provide important pathophysiological insight on the relationship between platelet aggregation and endothelial function, two parameters that have been shown to influence patients' prognosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT01700322; EudraCT-Nr.: 2011-005305-73. Current V.1.3, from 24 February 2014.

Overview of pleiotropic effects of platelet P2Y12 receptor inhibitors

Dual antiplatelet therapy consisting of one of the P2Y12 receptor inhibitors in conjunction with aspirin is the mainstay of treatment for patients with acute coronary syndromes (ACS) and those undergoing percutaneous coronary interventions (PCI). In recent years, multiple extra-platelet features of P2Y12 receptor antagonists have been reported in numerous clinical trials. The aim of this review is to summarise reported pleiotropic effects of clopidogrel, prasugrel, ticagrelor and other P2Y12 receptor blockers. We included observations made both in human and in animal models, together with proposed mechanisms of action for described features. If confirmed in randomised studies and properly applied to everyday practice, the observed extra-platelet actions could enable us to improve efficacy of ACS and post-PCI treatment, as well as to confine mortality and occurrence rate of cardiovascular events.

Clopidogrel improves microvascular endothelial function in subjects with stable coronary artery disease

BACKGROUND

Clopidogrel therapy has recently been shown to reduce cardiovascular events in patients with stable vascular disease. This benefit may be due to effects not exclusively related to platelet aggregation. The aim of this study was to evaluate the effect of clopidogrel therapy on microvascular endothelial function in subjects with stable coronary artery disease (CAD).

METHODS AND RESULTS

Forty subjects with stable CAD were randomised to clopidogrel therapy (75mg/day) or control. Blood and endothelial function testing occurred at baseline, one week and three months following randomisation. Microvascular endothelial function was assessed via reactive hyperaemic index (RHI). Platelet function was assessed by adenosine diphosphate (ADP)-induced whole blood aggregation and the VerifyNow™ system. Plasma markers of endothelial function (asymmetric dimethylarginine, ADMA) and oxidative stress (myeloperoxidase, MPO) were also tested. The primary endpoint was endothelial function assessment (RHI) at three months. At one week RHI increased by 20±10% in the clopidogrel group; this effect was maintained at three months (21±9% increase from baseline; P<0.01). A significant decrease in ADP-induced platelet aggregation and P2Y12 reaction units was observed in the clopidogrel therapy group (P<0.01). There was no correlation between endothelial function and platelet function testing in the clopidogrel therapy group.

CONCLUSION

Clopidogrel therapy is associated with improved microvascular endothelial function in patients with stable CAD. This effect is independent of its effects on ADP-induced platelet reactivity.

Influence of genetic variations on levels of inflammatory markers of healthy subjects at baseline and one week after clopidogrel therapy; results of a preliminary study

We aimed to assess the association between the most common polymorphisms of cytochrome P450 (CYP) epoxygenases on the plasma levels of inflammatory markers in a population of healthy subjects. We also sought to determine whether CYP2C19*2 polymorphism is associated with the anti-inflammatory response to clopidogrel. In a population of 49 healthy young males, the baseline plasma levels of inflammatory markers including C-reactive protein, haptoglobin, orosomucoid acid, CD-40 were compared in carriers vs. non-carriers of the most frequent CYP epoxygenase polymorphisms: CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C8*2 and CYP2J2*7. Also, the variation of inflammatory markers from baseline to 7 days after administration of 75 mg per day of clopidogrel were compared in carriers vs. non-carriers of CYP2C19* allele and also in responders vs. hypo-responders to clopidogrel, determined by platelet reactivity tests. There was no significant association between epoxygenase polymorphisms and the baseline levels of inflammatory markers. Likewise, CYP2C19* allele was not associated with anti-inflammatory response to clopidogrel. Our findings did not support the notion that the genetic variations of CYP epoxygenases are associated with the level of inflammatory markers. Moreover, our results did not support the hypothesis that CYP2C19*2 polymorphism is associated with the variability in response to the anti-inflammatory properties of clopidogrel.

Ticagrelor improves peripheral arterial function in patients with a previous acute coronary syndrome

OBJECTIVE

The novel P2Y12 antagonist ticagrelor inhibits adenosine diphosphate (ADP)-induced platelet aggregation more potently than clopidogrel and reduces the incidence of myocardial infarction and total death in patients with an acute coronary syndrome (ACS). Furthermore, ticagrelor inhibits adenosine reuptake and increases coronary flow reserve during adenosine infusion in man. We wanted to determine whether ticagrelor improves peripheral arterial function in patients with a previous ACS compared to patients treated with aspirin, clopidogrel, or prasugrel.

METHODS

127 patients with a previous ACS (>3 months to <3 years ago) on maintenance dose of (1) no ADP blocker (n = 35); (2) clopidogrel 75 mg (n = 35); (3) prasugrel 10 mg (n = 32), or (4) ticagrelor 90 mg twice daily (n = 25) were evaluated with peripheral arterial tonometry after forearm ischemia.

RESULTS

Ticagrelor improves peripheral arterial function compared to the other groups [(1) controls 1.78 ± 0.53; (2) clopidogrel 1.78 ± 0.45; (3) prasugrel 1.64 ± 0.33, and (4) ticagrelor 2.25 ± 0.54 (means ± SD)] with a significance of p < 0.01 for ticagrelor versus no ADP blocker, p < 0.01 for ticagrelor versus clopidogrel, and p < 0.001 for ticagrelor versus prasugrel. There were fewer patients with endothelial dysfunction (<1.67 reactive hyperemia index) in the ticagrelor group (12%) compared to aspirin (51%), clopidogrel (46%), and prasugrel (53%) (p < 0.01).

CONCLUSION

Treatment with ticagrelor improves peripheral endothelial function compared to no ADP blocker, clopidogrel, or prasugrel treatment.

Chronic protection against ischemia and reperfusion-induced endothelial dysfunction during therapy with different organic nitrates

INTRODUCTION

Ischemic and pharmacologic preconditioning have great clinical potential, but it remains unclear whether their effects can be maintained over time during repeated exposure.We have previously demonstrated that the acute protective effect of nitroglycerin (GTN) is attenuated during repeated daily administration. Pentaerythrityl tetranitrate (PETN) is an organic nitrate with different hemodynamic and biochemical properties. The purpose of the current experiment was to study the preconditioning-like effects of PETN and GTN during repeated daily exposure.

METHODS AND RESULTS

In a randomized, investigator-blind parallel trial, 30 healthy (age 25-32) volunteers were randomized to receive (1) transdermal GTN (0.6 mg/h) administered for 2 h a day for 6 days; (2) oral PETN (80 mg) once a day for 6 days; or (3) no therapy. One week later, endothelium-dependent flow-mediated dilation was assessed before and after exposure to ischemia and reperfusion (IR). IR caused a significant blunting of the endothelium-dependent relaxation in the control group (FMD before IR: 5.8 ± 2.1%; after IR 1.0 ± 2.1%; P < 0.01). Daily, 2-h exposure to GTN partially prevented IR-induced endothelial dysfunction (FMD before IR: 7.7 ± 2.4%; after IR 4.3 ± 3.0%; P < 0.01 compared to before IR). In contrast, daily PETN administration afforded greater protection from IR-induced endothelial injury (FMD before IR: 7.9 ± 1.7%; after IR 6.4 ± 5.3%, P = ns; P < 0.05 ANOVA across groups). In vitro, incubation of human endothelial cells with GTN (but not PETN) was associated with inhibition (P < 0.01) of aldehyde dehydrogenase, an enzyme that is important for both nitrate biotransformation and ischemic preconditioning.

DISCUSSION

We previously showed that upon repeated administration, the preconditioning-like effects of GTN are attenuated. The present data demonstrate a gradient in the extent of protection afforded by the two nitrates, suggesting that PETN-induced preconditioning is maintained after prolonged administration in a human in vivo model of endothelial dysfunction induced by ischemia. Using isolated human endothelial cells, we propose a mechanistic explanation for this observation based on differential effects of GTN versus PETN on the activity of mitochondrial aldehyde dehydrogenase.

Frequency of heparin/platelet factor 4-dependent platelet antibodies in patients undergoing angioplasty and stenting for cardiovascular disease and their role for on-clopidogrel platelet reactivity

BACKGROUND

The frequency of heparin-induced platelet antibodies (H/PF4 antibodies) following heparin exposure during percutaneous intervention with stent implantation is unknown. These antibodies may activate platelets and therefore contribute to high on-clopidogrel residual platelet reactivity (HRPR).

METHODS

We screened 288 patients after angioplasty and stenting for H/PF4 antibodies by an IgG/A/M ELISA. The 44 (15.3%) positive samples were further evaluated for IgG only antibodies, by the particle gel immunoassay (PaGIA), the heparin induced platelet activation assay (HIPA) and MEA. Further, we determined on-treatment platelet reactivity by multiple electrode aggregometry (MEA) in these patients. In vivo platelet activation was assessed by P-selectin expression.

RESULTS

The prevalence of H/PF4 antibodies in the total patients' cohort was 15.3% (95% CI 11.3-20%) by the IgG/A/M ELISA, 9.4% (95% CI 6.3-13.4%) by the IgG ELISA, 11.5% (95% CI 8-15.7%) by PaGIA, 14.2% (95% CI 10.4-18.8%) by MEA, and 2.4% (95% CI 1-4.9%) by HIPA. On-treatment platelet reactivity was similar between patients without and with H/PF4 antibodies [39 AU (6-110 AU) vs. 41 AU (7-91 AU); P = 0.85]. HRPR was seen in 105 patients (37.5%), and occurred to a similar extent in patients without and with H/PF4 antibodies in all test systems (all P > 0.2). Further, there was no difference of the ELISA optical densities using the IgG/A/M or the IgG only ELISA between patients without or with HRPR (all P > 0.3). There was no significant difference of P-selectin expression between patients without or with H/PF4 antibodies (P = 0.97). Noteworthy, none of the patients who developed H/PF4 antibodies had heparin-induced thrombocytopenia or a thromboembolic event.

CONCLUSION

H/PF4 antibodies are not rare in patients undergoing angioplasty and stenting. However, these antibodies are not associated with the occurrence of HRPR.

The effect of binge fetal alcohol exposure on the number of vasoactive intestinal peptide-producing neurons in fetal sheep brain

Previously we demonstrated that fetal alcohol exposure attenuates hypoxic cerebral vasodilation in fetal and neonatal sheep. One mechanism may be altered expression of brain vasoactive substances. We hypothesized that early fetal alcohol exposure alters the number of fetal neurons expressing vasoactive intestinal peptide (VIP), a potent cerebral vasodilator. Thirteen pregnant ewes received daily i.v. infusions of alcohol (1.5 g/kg) or saline on days 30-54 of gestation (term = 145 days). Fourteen fetal brains (6 alcohol-exposed, 8 saline control) were obtained on gestational day 126. Using unbiased stereology, we counted immunohistochemically-labeled VIP neurons in one half of each forebrain with an optical fractionator. The total NeuN-labeled neurons were similarly counted. Alcohol-exposed fetal sheep brains had fewer VIP-immunopositive neurons per hemisphere, 14.6 x 10(6), compared to saline controls, 19.8 x 10(6). The total neuron number was not different, 1.19 x 10(9) versus 1.23 x 10(9) respectively, indicating a selective decrease in VIP neurons as a result of alcohol exposure. In sheep, alcohol exposure early in gestation is associated with fewer VIP-producing neurons later in gestation compared to saline controls; therefore, alcohol-related changes in the number of VIP-expressing neurons may be responsible in part for the attenuated hypoxic cerebral vasodilation described in fetal and neonatal sheep exposed to alcohol earlier in gestation.