Platelet activation in patients after an acute coronary syndrome: results from the TIMI-12 trial. Thrombolysis in Myocardial Infarction

Effects of exercise on platelet reactivity after myocardial infarction: a randomized clinical trial

Exercise training (ET) can lower platelet reactivity in patients with cardiovascular risk factors. However, the effects of ET on platelet reactivity in higher-risk patients is unknown. The aim of this study was to evaluate the effects of ET on platelet reactivity in patients with recent myocardial infarction (MI). Ninety patients were randomly assigned 1 month post-MI to the intervention (patients submitted to a supervised ET program) or control group. All patients were on dual antiplatelet therapy (DAPT). Platelet reactivity by VerifyNow-P2Y12 (measured by P2Y12 reaction units - PRUs) test was determined at baseline and at the end of 14 ± 2 weeks of follow-up at rest (primary endpoint), and multiplate electrode aggregometry (MEA) adenosine diphosphate (ADP) and aspirin (ASPI) tests were performed immediately before and after the maximal cardiopulmonary exercise test (CPET) at the same time points (secondary endpoints). Sixty-five patients (mean age 58.9 ± 10 years; 73.8% men; 60% ST elevation MI) completed follow-up (control group, n = 31; intervention group, n = 34). At the end of the follow-up, the mean platelet reactivity was 172.8 ± 68.9 PRUs and 166.9 ± 65.1 PRUs for the control and intervention groups, respectively (p = .72). Platelet reactivity was significantly increased after the CPET compared to rest at the beginning and at the end of the 14-week follow-up (among the intervention groups) by the MEA-ADP and MEA-ASPI tests (p < .01 for all analyses). In post-MI patients on DAPT, 14 weeks of supervised ET did not reduce platelet reactivity. Moreover, platelet reactivity was increased after high-intensity exercise (ClinicalTrials.gov: NCT02958657; https://clinicaltrials.gov/ct2/show/NCT02958657).

Diabetes- versus smoking-related thrombo-inflammation in peripheral artery disease

Peripheral artery disease (PAD) is a major health problem with increased cardiovascular mortality, morbidity and disabling critical limb threatening ischemia (CLTI) and amputation. Diabetes mellitus (DM) and cigarette smoke are the main risk factors for the development of PAD. Although diabetes related PAD shows an accelerated course with worse outcome regarding complications, mortality and amputations compared with non-diabetic patients, current medical treatment does not make this distinction and includes standard antiplatelet and lipid lowering drugs for all patients with PAD. In this review we discuss the pathophysiologic mechanisms of PAD, with focus on differences in thrombo-inflammatory processes between diabetes-related and smoking-related PAD, and hypothesize on possible mechanisms for the progressive course of PAD in DM. Furthermore, we comment on current medical treatment and speculate on alternative medical drug options for patients with PAD and DM.

Clinical Cytometry for Platelets and Platelet Disorders

Clinical flow cytometry tests for inherited and acquired platelet disorders are useful diagnostic tools but are not widely available. Flow cytometric methods are available to detect inherited glycoprotein deficiencies, granule release (secretion defects), drug-induced thrombocytopenias, presence of antiplatelet antibodies, and pharmacodynamic inhibition by antiplatelet agents. New tests take advantage of advanced multicolor cytometers and allow identification of novel platelet subsets by high-dimensional immunophenotyping. Studies are needed to evaluate the value of these new tests for diagnosis and monitoring of therapy in patients with platelet disorders.

Impaired tolerance to the autoantigen LL-37 in acute coronary syndrome

Background

LL-37 is the only member of the cathelicidin family of antimicrobial peptides in humans and is an autoantigen in several autoimmune diseases and in acute coronary syndrome (ACS). In this report, we profiled the specific T cell response to the autoimmune self-antigen LL-37 and investigated the factors modulating the response in peripheral blood mononuclear cells (PBMCs) of healthy subjects and ACS patients.

Methods and results

The activation induced marker (AIM) assay demonstrated differential T cell profiles characterized by the persistence of CD134 and CD137, markers that impair tolerance and promote immune effector and memory response, in ACS compared to Controls. Specifically, CD8+CD69+CD137+ T cells were significantly increased by LL-37 stimulation in ACS PBMCs. T effector cell response to LL-37 were either HLA dependent or independent as determined by blocking with monoclonal antibody to either Class-I HLA or Class-II HLA. Blocking of immune checkpoints PD-1 and CTLA-4 demonstrated the control of self-reactive T cell response to LL-37 was modulated predominantly by CTLA-4. Platelets from healthy controls down-modulated CD8+CD69+CD137+ T cell response to LL-37 in autologous PBMCs. CD8+CD69+CD137+ T cell AIM profile negatively correlated with platelet count in ACS patients.

Conclusions

Our report demonstrates that the immune response to the autoantigen LL-37 in ACS patients is characterized specifically by CD8+CD69+CD137+ T cell AIM profile with persistent T cell activation and the generation of immunologic memory. The results provide potentially novel insight into mechanistic pathways of antigen-specific immune signaling in ACS.

Oligosaccharide Blocks PAR1 (Proteinase-Activated Receptor 1)-PAR4-Mediated Platelet Activation by Binding to Thrombin Exosite II and Impairs Thrombosis

BACKGROUND

Inappropriate activation and aggregation of platelets can lead to arterial thrombosis. Thrombin is the most potent platelet agonist that activates human platelets via two PARs (proteinase-activated receptors), PAR1 and PAR4. The aim is to study the activity and mechanism of an oligosaccharide HS-11 (the undecasaccharide, derived from sea cucumber Holothuria fuscopunctata) in inhibiting thrombin-mediated platelet activation and aggregation and to evaluate its antithrombotic activity.

METHODS

Platelet activation was analyzed by detecting CD62P/P-selectin expression using flow cytometry. The HS-11-thrombin interaction and the binding site were studied by biolayer interferometry. Intracellular Ca²⁺ mobilization of platelets was measured by FLIPR Tetra System using Fluo-4 AM (Fluo-4 acetoxymethyl). Platelet aggregation, thrombus formation, and bleeding Assay were assessed.

RESULTS

An oligosaccharide HS-11, depolymerized from fucosylated glycosaminoglycan from sea cucumber Holothuria fuscopunctata blocks the interaction of thrombin with PAR1 and PAR4 complex by directly binding to thrombin exosite II, and completely inhibits platelet signal transduction, including intracellular Ca²⁺ mobilization and protein phosphorylation. Furthermore, HS-11 potently inhibits thrombin-PARs-mediated platelet aggregation and reduces thrombus formation in a model of ex vivo thrombosis.

CONCLUSIONS

The study firstly report that the fucosylated glycosaminoglycan oligosaccharide has antiplatelet activity by binding to thrombin exosite II, and demonstrates that thrombin exosite II plays an important role in the simultaneous activation of PAR1 and PAR4, which may be a potential antithrombotic target for effective treatment of arterial thrombosis.

A general chemical principle for creating closure-stabilizing integrin inhibitors

Integrins are validated drug targets with six approved therapeutics. However, small-molecule inhibitors to three integrins failed in late-stage clinical trials for chronic indications. Such unfavorable outcomes may in part be caused by partial agonism, i.e., the stabilization of the high-affinity, extended-open integrin conformation. Here, we show that the failed, small-molecule inhibitors of integrins αIIbβ3 and α4β1 stabilize the high-affinity conformation. Furthermore, we discovered a simple chemical feature present in multiple αIIbβ3 antagonists that stabilizes integrins in their bent-closed conformation. Closing inhibitors contain a polar nitrogen atom that stabilizes, via hydrogen bonds, a water molecule that intervenes between a serine residue and the metal in the metal-ion-dependent adhesion site (MIDAS). Expulsion of this water is a requisite for transition to the open conformation. This change in metal coordination is general to integrins, suggesting broad applicability of the drug-design principle to the integrin family, as validated with a distantly related integrin, α4β1.

In-vivo platelet activation and aggregation during and after acute atherothrombotic myocardial infarction in patients with and without Type-2 diabetes mellitus treated with ticagrelor

INTRODUCTION

Patients with type-2 diabetes are twice as likely to suffer from acute myocardial infarction (AMI) and have a higher incidence of recurrent events than their non-diabetic counterparts. Ticagrelor is a platelet inhibitor known to reduce major adverse cardiovascular events (MACE) in AMI patients. This study measures the level and change in platelet activation and aggregation at the time of and following an AMI in patients with and without diabetes treated with ticagrelor.

MATERIALS/METHODS

P₂Y₁₂ receptor inhibitor naïve patients presenting with AMI were prospectively enrolled. Blood collection occurred before coronary angiography (baseline: T₀), 2, 4, 24, 48 h after baseline, and at a three-month follow-up. Ticagrelor was administered within five minutes of T₀. We assessed platelet activation via measurements of surface P-selectin and platelet activated glycoprotein IIb/IIIa-1 (PAC-1) and assessed platelet aggregation via monocyte, lymphocyte, and granulocyte aggregates. We hypothesize that platelet activation and aggregation will be proportionally impacted to the same degree by ticagrelor, regardless of diabetes status.

RESULTS

Ninety-seven patients were prospectively enrolled (diabetes, N = 33; no diabetes, N = 64). No difference was observed in the expression of P-selectin and PAC-1 at any given point between diabetes and non-diabetes groups (p > 0.05). No difference was observed in the percentage of platelet bound to leukocytes at any measured timepoint between patients with and without diabetes (p > 0.05). Platelet leukocyte aggregation was suppressed during the acute phase compared to quiescence equally among both groups.

DISCUSSION

Ticagrelor demonstrated similar in-vivo effects on platelet activation and aggregation regardless of diabetes status in patients presenting with AMI.

Antiplatelet Therapy in Atherothrombotic Diseases: Similarities and Differences Across Guidelines

Antiplatelet therapy, mainly consisting of aspirin and P2Y₁₂ receptor antagonists, is the cornerstone of the pharmacological treatment and prevention of atherothrombotic diseases. Its use, especially in secondary cardiovascular prevention, has significantly improved patient clinical outcomes in the last decades. Primary safety endpoint (i.e., bleeding complications) remain a major drawback of antiplatelet drugs. National and international societies have published and regularly updated guidelines for antiplatelet therapy aiming to provide clinicians with practical recommendations for a better handling of these drugs in various clinical settings. Many recommendations find common ground between international guidelines, but certain strategies vary across the countries, particularly with regard to the choice of molecules, dosage, and treatment duration. In this review, we detail and discuss the main antiplatelet therapy indications in the light of the different published guidelines and the significant number of recently published clinical trials and meta-analyses and highlight the areas that deserve further investigation in order to improve antiplatelet therapy in patients with atherothrombotic diseases.

Impairment of Anti-Aggregatory Responses to Nitric Oxide and Prostacyclin: Mechanisms and Clinical Implications in Cardiovascular Disease

The propensity towards platelet-rich thrombus formation increases substantially during normal ageing, and this trend is mediated by decreases in platelet responsiveness to the anti-aggregatory nitric oxide (NO) and prostacyclin (PGI₂) pathways. The impairment of soluble guanylate cyclase and adenylate cyclase-based signalling that is associated with oxidative stress represents the major mechanism of this loss of anti-aggregatory reactivity. Platelet desensitization to these autacoids represents an adverse prognostic marker in patients with ischemic heart disease and may contribute to increased thrombo-embolic risk in patients with heart failure. Patients with platelet resistance to PGI₂ also are unresponsive to ADP receptor antagonist therapy. Apart from ischemia, diabetes and aortic valve disease are also associated with impaired anti-aggregatory homeostasis. This review examines the association of impaired platelet cyclic nucleotide (i.e., cGMP and cAMP) signalling with the emerging evidence of thromboembolic risk in cardiovascular diseases, and discusses the potential therapeutic strategies targeting this abnormality.

Pharmacological Approaches to Limit Ischemic and Reperfusion Injuries of the Heart. Analysis of Experimental and Clinical Data on P2Y12 Receptor Antagonists

High mortality among people with acute myocardial infarction is one of the most urgent problems of modern cardiology. And in recent years, much attention has been paid to the search for pharmacological approaches to prevent heart damage. In this review, we tried to analyze data on the effect of P2Y₁₂ receptor antagonists on the ischemia/reperfusion tolerance of the heart.

Ischemic and reperfusion injuries of the heart underlie the pathogenesis of acute myocardial infarction (AMI) and sudden cardiac death. The mortality rate is still high and is 5–7% in patients with ST-segment elevation myocardial infarction. The review is devoted to pharmacological approaches to limitation of ischemic and reperfusion injuries of the heart. The article analyzes experimental evidence and the clinical data on the effects of P2Y₁₂ receptor antagonists on the heart’s tolerance to ischemia/reperfusion in animals with coronary artery occlusion and reperfusion and also in patients with AMI. Chronic administration of ticagrelor prevented adverse remodeling of the heart. There is evidence that sphingosine-1-phosphate is the molecule that mediates the infarct-reducing effect of P2Y₁₂ receptor antagonists. It was discussed a role of adenosine in the cardioprotective effect of ticagrelor.

Reperfusion Cardiac Injury: Receptors and the Signaling Mechanisms

It has been documented that Ca2+ overload and increased production of reactive oxygen species play a significant role in reperfusion injury (RI) of cardiomyocytes. Ischemia/reperfusion induces cell death as a result of necrosis, necroptosis, apoptosis, and possibly autophagy, pyroptosis and ferroptosis. It has also been demonstrated that the NLRP3 inflammasome is involved in RI of the heart. An increase in adrenergic system activity during the restoration of coronary perfusion negatively affected cardiac resistance to RI. Toll-like receptors are involved in RI of the heart. Angiotensin II and endothelin-1 aggravated ischemic/reperfusion injury of the heart. Activation of neutrophils, monocytes, CD4+ T-cells and platelets contributes to cardiac ischemia/reperfusion injury. Our review outlines the role of these factors in reperfusion cardiac injury.

Platelet miR-107 Participates in Clopidogrel Resistance after PCI Treatment by Regulating P2Y12

INTRODUCTION

High platelet reactivity (HPR) caused by clopidogrel tolerance is an adverse reaction of acute coronary syndrome (ACS) patients who receive clopidogrel antiplatelet therapy after percutaneous coronary intervention (PCI) surgery. Platelet microRNA (miRNA) is related to platelet reactivity. This study explored the mechanism of platelet miRNA in regulating platelet reactivity.

METHODS

We recruited 50 ACS/PCI patients and divided them into the HPR group (P2Y12 reaction units [PRU] ≥300) and the LPR group (PRU < 170) according to the PRU through the VerifyNow P2Y12 assay. P2Y12-related miRNAs were screened by TargetScan, miRWalk, and Gene Expression Omnibus. The expressions of P2Y12 and miRNAs in the HPR group and the LPR group were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Pearson correlation analysis was used to determine the correlation between P2Y12 and miRNAs. The interactions between P2Y12 and miR-107 were predicted by TargetScan and verified by dual-luciferase reporter assay. The regulation of miR-107 mimic or inhibitor on P2Y12 expression was detected by qRT-PCR and Western blot.

RESULTS

There were 22 patients in the LPR group and 28 patients in the HPR group. PY212 was highly expressed in the HPR group compared with the LPR group. We screened the P2Y12-related miRNAs (miR-145-5p, miR-4701-3p, miR-107, and miR-15b-5p), but only miR-107 and miR-15b-5p expressions were downregulated in the HPR group and were negatively correlated with PY212 expression. P2Y12 was the target gene of miR-107. PY212 expression was inhibited by miR-107 overexpression but suppressed by miR-107 silencing.

CONCLUSION

Platelet miR-107 participated in clopidogrel resistance in ACS/PCI patients by regulating P2Y12 expression.

Apoptotic microparticles mediate the association between bisphenol A and subclinical atherosclerosis in a young population: A population-based study

Bisphenol A (BPA) exposure is associated with atherosclerotic cardiovascular diseases. The interactions between BPA, extracellular microparticles (MPs), and atherosclerosis are unknown. A total of 103,756 young students participated in the mass urine-screening program in Taiwan between 1992 and 2000 were analyzed. After exclusion, 886 subjects were recruited to test the relationships between serum level of BPA, endothelial and platelet MPs as well as subclinical atherosclerosis represented by carotid artery intima-media thickness (CIMT). We found that an increment of one unit of log-BPA could lead to significant association between thicker CIMT and concentrations of endothelial microparticles and platelet microparticles in the cohort (odds ratio (OR) 1.23, P < 0.001). CD31 + /CD42a- (> 50%, OR 1.229, P = 0.001) and CD31 + /CD42a+ (≦ 50%, OR 1.262, P = 0.017 and > 50%, OR 1.212, P = 0.006) were significantly associated with thicker CIMT in the presence of elevated BPA. When considering the interactions between CD31 + /CD42a- and CD31 + /CD42a+ , we observed increased OR as CD31 + /CD42a- was greater than 50% (CD31 +/CD42a- > 50% and CD31 +/CD42a+ ≦ 50%, OR 1.356, P = 0.029; CD31 +/CD42a- > 50% and CD31 +/CD42a+ > 50%, OR 1.204, P = 0.014). Our study identified a higher risk of thicker CIMT associated with altered MPs in the presence of elevated BPA levels. BPA exposure is associated with endothelial dysfunction and subclinical atherosclerosis in a young population.

Platelet apelin receptor expression is reduced in patients with acute myocardial infarction

BACKGROUND

The G-protein-coupled apelin receptor and its apelin ligand are an emerging regulatory system of the vascular homeostasis. To date, the implications of the apelin/apelin receptor system in athero-thrombosis are not completely clarified yet. This study determines the expression of the apelin receptor on human platelets, the effect of different apelin isoforms on platelet aggregation and the potential role of the apelin/apelin receptor system in acute myocardial infarction.

METHODS

We applied immunofluorescence staining, Western Blot analysis, aggregometry, and flow cytometry to elucidate the role of the apelin receptor in activated platelets. Furthermore, in an observational pilot study, we assessed platelet apelin recpetor expression and apelin-17 plasma levels in patients with acute myocardial infarction (AMI, n = 27).

RESULTS

Immunofluorescence staining indicates that the apelin receptor is located at the cell membrane in resting platelets and diminishes upon activation with a selective thrombin receptor-activating peptide (AP1, 3 to 100 μM). Western Blot analyses of AP1-activated platelets and their supernatants suggest that the apelin receptor is not predominantly internalized but is released from activated platelets. The isoform apelin-17 attenuated AP-1-induced platelet activation in-vitro, presumably via a NO-dependent mechanism. Furthermore, platelet apelin receptor expression was significantly reduced in patients with AMI (n = 27) compared to age-matched controls (n = 14; p < 0.05) and inversely correlated with troponin I plasma levels (r = -0.46; p = 0.03). Besides that, circulating apelin-17 was significantly reduced in MI patients compared to the control group.

CONCLUSION

Taken together, our data support a crucial role of the platelet apelinergic system assuming an antithrombotic effect and therefore holding a potential diagnostic and therapeutic impact.

The association between urinary levels of 1,3-butadiene metabolites, cardiovascular risk factors, microparticles, and oxidative stress products in adolescents and young adults

1,3-Butadiene (BD) is a synthetic colorless gas used in the production of synthetic rubber and polymers. Exposure to BD has been reported to increase oxidative stress and accelerate atherosclerosis in vitro and in animal studies. In occupational studies, BD exposure has been linked to cardiovascular disease (CVD). However, no previous research has been reported on whether BD exposure is associated with CVD risk factors and oxidative stress in the general population. We recruited 853 young participants to study the correlation between urinary levels of the BD metabolite, N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA), CVD risk factors, serum levels of endothelial microparticles and platelet microparticles, and the urinary levels of 8-hydroxydeoxyguanosine (8-OHdG). The results showed the DHBMA levels were positively correlated with low-density lipoprotein-C, carotid intima-media thickness (CIMT), CD31+/CD42a - counts (endothelial apoptosis markers), and urinary 8-OHdG levels. Moreover, DHBMA levels were negatively correlated with CD62 P counts (platelet activation marker). The correlation between DHBMA, CIMT, and 8-OHdG was more evident when the levels of CD31+/CD42a - or CD62 P were above 50%. In conclusion, we reported that the urinary levels of DHBMA were associated with the lipid profile, CIMT, microparticles, and marker of oxidative stress in this young population. Future studies on BD exposure and atherosclerosis are needed.

Platelet/lymphocyte ratio for prediction of no-reflow phenomenon in ST-elevation myocardial infarction managed with primary percutaneous coronary intervention

Background

Coronary no-reflow phenomenon in ST-segment elevation myocardial infarction (STEMI) is associated with a poor clinical outcome. Although its pathophysiology is not fully understood, a deregulated systemic inflammatory response plays an important role. We aimed to explore the relationship between platelet\lymphocyte ratio (PLR) and no-reflow in patients with acute STEMI who were treated with a primary percutaneous coronary intervention (PPCI).

Methods

A total of 200 patients with STEMI undergoing PPCI were included in the study. Transthoracic echocardiographic examination was performed to assess left ventricular (LV) ejection fraction (EF) and wall motion score index. Blood samples were assayed for platelet and lymphocyte count before PPCI. No-reflow was defined as coronary blood flow thrombolysis in myocardial infarction grade ≤II.

Results

No-reflow was observed in 58 (29%) of STEMI patients following PPCI. PLR was significantly higher in hypertensive patients compared to normotensive patients (144.7±91.6 vs. 109.1±47.1, respectively, P<0.001) and in the no-reflow group compared to the normal reflow group (214±93 vs. 101.6±51.3, respectively, P<0.0001). Logistic regression analysis revealed that PLR (β: 0.485, 95% CI: -0.006-0.001, P<0.002) and LV EF (β: 0.272, 95% CI: 0.009-0.034, P<0.001) were independent predictors of no-reflow after PPCI.

Conclusion

Pre-procedural increase in PLR is predictive of the no-reflow phenomenon following PPCI in STEMI patients.

Relevance for Patients

No reflow phenomenon is an unfavorable complication following PPCI in patients with acute STEMI. High pre-procedural PLR is an independent predictor of reperfusion failure and helps to identify patients who require prophylactic treatment.

Influence of diagnosis of venous thromboembolism on immature platelets, absolute platelet count and platelet aggregation over time

The extent of the involvement of platelets in venous thromboembolisms (VTE) is still not fully understood. Immature platelets are large, RNA-rich, prothrombotic platelets. They are involved in arterial thromboembolisms and are associated with adverse cardiovascular events. Their role in VTE has not been investigated before. The aim of this study was to assess different platelet parameters including immature platelet fraction (IPF), immature platelet count (IPC), absolute platelet count and platelet aggregation (PA) over time in patients with VTE at time of diagnosis, as well as at 3-10 days and at 90-110 days after diagnosis. 50 healthy volunteers similar in age and sex to patients served as controls at diagnosis. IPF was measured by the Sysmex XE-5000 analyzer, PA was assessed using the Multiplate analyzer. Diagnosis of VTE had no relevant effect on IPF and IPC whereas absolute platelet count and PA were significantly decreased compared to controls. In the course of VTE, IPF decreased significantly, whereas IPC, absolute platelet count and PA increased. In conclusion, VTE was associated with relevant changes of the absolute platelet count and PA at diagnosis, as well as changes in IPF and IPC over time reflecting a relevant and measurable platelet consumption in VTEs.

Relation of White Blood Cell Count to Bleeding and Ischemic Events in Patients With Acute Coronary Syndrome (from the ATLAS ACS 2-TIMI 51 Trial)

An elevated white blood cell (WBC) count is associated with an increased risk of ischemic events among acute coronary syndrome (ACS) patients, but the association between WBC count and bleeding in ACS patients is not well established. The aim of this analysis was to assess and compare the association between WBC count and the occurrence of short- and long-term bleeding and ischemic events. This was a post hoc analysis of the ATLAS ACS2-TIMI 51 trial. A subset of patients had a WBC count measurement at baseline (n = 14,231, 91.6%). Univariate and multivariable Cox proportional hazard models were constructed to determine if there is an association between WBC count at baseline and a composite outcome of Thrombolysis in Myocardial Infarction (TIMI) major and minor bleeds at 30 days and 1 year. Variables with a p <0.2 in the univariate analysis were included as potential parameters in the backward selection process A similar multivariable model was constructed to assess the association between WBC count and a composite ischemic endpoint of cardiovascular death, myocardial infarction and stroke. An increased risk of bleeding per a 1 × 10⁹/L increase in WBC at baseline was observed at 30 days (Adjusted hazard ratio [HR] 1.08 95% confidence interval [CI] 1.01 to 1.17, p = 0.019) but not at 1 year (Adjusted HR 1.02 95% CI 0.97 to 1.08, p = 0.409). Additionally, an increased risk of ischemia per a 1 × 10⁹/L increase in WBC at baseline was observed at 30 days (Adjusted HR 1.07, 95% CI: 1.03 to 1.12, p = 0.002) and at 1 year (Adjusted HR 1.05 95% CI 1.02 to 1.08, p = 0.001 at 1 year). In conclusion, a higher WBC count at baseline was associated with an increased risk of the composite bleeding endpoint by 30 days but not at 1 year. The association between WBC count and the risk of the composite ischemic endpoint was significant at 30 days and 1 year.

Role of Platelet Activation and Oxidative Stress in the Evolution of Myocardial Infarction

Myocardial infarction, commonly known as heart attack, evolves from the rupture of unstable atherosclerotic plaques to coronary thrombosis and myocardial ischemia–reperfusion injury. A body of evidence supports a close relationship between the alterations following an ischemia–reperfusion injury-induced oxidative stress and platelet activity. Through their critical role in thrombogenesis and inflammatory responses, platelets are fully (totally) implicated from atherothrombotic plaque formation to myocardial infarction onset and expansion. However, mere platelet aggregation prevention does not offer full protection, suggesting that other antiplatelet therapy mechanisms may also be involved. Thus, the present review discusses the integrative role of platelets, oxidative stress, and antiplatelet therapy in triggering myocardial infarction pathophysiology.

Mean platelet volume and clinical outcomes of patients with chest pain discharged from internal medicine wards

BACKGROUND

Currently, there are no clinical scores for risk stratification of low-risk patients with chest pain. We aimed to examine the association between mean platelet volume (MPV) and risk for adverse clinical outcomes in patients with chest pain discharged from internal medicine wards following acute coronary syndrome (ACS) rule-out.

PATIENTS AND METHODS

Included were patients who were admitted to internal medicine wards and were discharged following an ACS-rule-out during 2010-2016. The primary endpoint was the composite of all-cause mortality and hospital admission due to ACS at 30-days following hospital discharge.

RESULTS

Included in the study were12 440 patients who were divided into three groups according to MPV. The composite endpoint of 30-day all-cause mortality and hospital admission for ACS occurred more frequently among patients with high MPV. Each one-point increase in MPV was associated with an 18% increase in the risk for the composite endpoint (P = 0.02). Considering patients with MPV less than 7.8 fl as the reference group yielded adjusted hazard ratios for the composite endpoint that was significantly higher in patients in the high MPV tertile ( > 8.8 fl) (hazard ratio 1.6; 95% confidence interval = 1.1-2.5; P = 0.04). Each one-point increase in MPV was associated with an 11% increase in the risk for 1-year all-cause mortality (P = 0.01) and a 10% increase in the risk for 1-year ACS (P = 0.04).

CONCLUSION

We found an independent association between high MPV and the risk of death and ACS among patients with chest pain who were discharged from internal medicine wards following an ACS-rule-out. MPV may be combined in the risk stratification of patients with chest pain.

Hypoxia and Ischemia Promote a Maladaptive Platelet Phenotype

Supplemental Digital Content is available in the text.

Objective—

Reduced blood flow and tissue oxygen tension conditions result from thrombotic and vascular diseases such as myocardial infarction, stroke, and peripheral vascular disease. It is largely assumed that while platelet activation is increased by an acute vascular event, chronic vascular inflammation, and ischemia, the platelet activation pathways and responses are not themselves changed by the disease process. We, therefore, sought to determine whether the platelet phenotype is altered by hypoxic and ischemic conditions.

Approach and Results—

In a cohort of patients with metabolic and peripheral artery disease, platelet activity was enhanced, and inhibition with oral antiplatelet agents was impaired compared with platelets from control subjects, suggesting a difference in platelet phenotype caused by the disease. Isolated murine and human platelets exposed to reduced oxygen (hypoxia chamber, 5% O₂) had increased expression of some proteins that augment platelet activation compared with platelets in normoxic conditions (21% O₂). Using a murine model of critical limb ischemia, platelet activity was increased even 2 weeks postsurgery compared with sham surgery mice. This effect was partly inhibited in platelet-specific ERK5 (extracellular regulated protein kinase 5) knockout mice.

Conclusions—

These findings suggest that ischemic disease changes the platelet phenotype and alters platelet agonist responses because of changes in the expression of signal transduction pathway proteins. Platelet phenotype and function should, therefore, be better characterized in ischemic and hypoxic diseases to understand the benefits and limitations of antiplatelet therapy.

Usefulness of Platelet-to-Lymphocyte Ratio to Predict Long-Term All-Cause Mortality in Patients at High Risk of Coronary Artery Disease Who Underwent Coronary Angiography

Platelet-to-lymphocyte ratio (PLR) has recently been studied as a biomarker in patients with established coronary artery disease (CAD). The association between PLR and long-term all-cause mortality is unclear in patients at high risk of CAD who undergo coronary angiography for various indications. Follow-up was completed for 514 patients who underwent coronary angiography in a prospective study cohort. The primary end point was all-cause mortality. Patients were classified into tertiles based on preangiography PLR and also dichotomized based on the optimal cutoff at a PLR of 137, determined from the receiver operating characteristic curve analysis. The mean follow-up period was 5.0 ± 1.3 years, with 50 all-cause deaths. On the Kaplan-Meier analysis, patients in Tertile 3 (PLR > 145) had worse prognosis than patients in Tertiles 1 (PLR ≤ 106) and 2 (PLR 106.1 to 145) (p = 0.0075), and patients with PLR ≥ 137 had a significantly higher rate of all-cause mortality than those with PLR < 137 (p = 0.0006). On multivariate Cox regression adjusting for known cardiovascular risk factors, PLR was a strong, independent predictor of long-term all-cause mortality on the tertile analysis (Tertile 3 vs Tertile 1: hazard ratio 2.52, 95% confidence interval 1.18 to 5.39, p = 0.017) and based on the cutoff at a PLR of 137 (PLR ≥ 137 vs <137: hazard ratio 2.25, 95% confidence interval 1.21 to 4.20, p = 0.011). In conclusion, elevated PLR is associated with long-term all-cause mortality in patients at high risk of CAD who undergo coronary angiography, and PLR may be a useful prognostic biomarker in this population.

Duration of Dual Antiplatelet Therapy in Patients with an Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

BACKGROUND

The recent American Heart Association/American College of Cardiology guidelines on duration of dual antiplatelet therapy (DAPT) recommend DAPT for 1 year in patients presenting with an acute coronary syndrome, with a Class IIb recommendation for continuation. We aim to assess the evidence for these recommendations using a meta-analytic approach.

METHODS

We searched electronic databases for randomized trials comparing short-term (≤6 months) vs 12-month vs extended (>12 months) DAPT in patients with an acute coronary syndrome undergoing percutaneous coronary intervention. We evaluated all-cause mortality, cardiovascular mortality, myocardial infarction, stent thrombosis, and major bleeding. A random-effects model was used to calculate pooled relative risk (RR) and 95% confidence intervals (CI).

RESULTS

We included 8 trials comprising 12,917 patients with an acute coronary syndrome; 5 trials compared short-term vs 12-month/extended DAPT, whereas 3 trials compared 12-month vs extended DAPT. There was no significant difference in cardiovascular mortality (RR 1.04; 95% CI, 0.67-1.60), myocardial infarction (RR 1.08; 95% CI, 0.79-1.47), or major bleeding (RR 0.91; 95% CI, 0.49-1.69) between short-term and 12-month/extended DAPT. However, compared with extended DAPT, 12-month DAPT showed significantly higher risk of myocardial infarction (RR 2.00; 95% CI, 1.47-2.73), but reduced risk of major bleeding (RR 0.58; 95% CI, 0.34-0.98). All-cause mortality was found to be similar between 12-month and extended DAPT.

CONCLUSIONS

In acute coronary syndrome, short-term DAPT may be reasonable for some patients, whereas extended DAPT may be appropriate in select others. An individualized approach is needed, taking into account the competing risks of bleeding and ischemic events.

Relationship between coronary tortuosity and plateletcrit coronary tortuosity and plateletcrit

Background

Coronary tortuosity (CorT) is a common angiographic finding and may be associated with myocardial ischaemia, even without coronary artery disease. Platelets play a crucial role in inflammatory and thrombotic processes and the physiopathology of cardiovascular disease. Larger platelets are more active enzymatically and have higher thrombotic ability compared to smaller platelets. Plateletcrit (PCT) provides complete information on total platelet mass. We aimed to evaluate the relationship between CorT and PCT in patients with chronic stable angina.

Methods

The medical records of consecutive patients who underwent coronary angiography from January 2013 to January 2016 were retrospectively reviewed for CorT. CorT and clinical, echocardiographic, haematological and biochemical parameters were evaluated. Taking into consideration the inclusion criteria, 106 patients with CorT and 108 with normal coronary angiographies (control group) were included in the study. CorT was defined as three fixed bends during both systole and diastole, with each bend ≥ 45°.

Results

The median PCT, mean platelet volume (MPV), platelet:large-cell ratio (P-LCR), neutrophil:lymphocyte ratio (NLR) and platelet:lymphocyte ratio (PLR) of the CorT group were significantly higher than those of the control group (0.26 ± 0.02 vs 0.2 ± 0.03%, p < 0.001; 10.6 ± 0.14 vs 9.6 ± 0.65 fl, p < 0.001; 29.3 ± 6.7 vs 23.4 ± 5.1, p < 0.001; 2.3 ± 1 vs 1.47 ± 0.48, p < 0.001; 1.28 ± 0.5 vs 0.82 ± 0.23, p < 0.001, respectively). The incidence of diabetes mellitus, hypertension and female gender were significantly higher in the CorT group (18.9 vs 1.9%, p < 0.001, 90.6 vs 50%, p < 0.001, 70.8 vs 44.4%, p < 0.001, respectively). Multivariate logistic regression analysis revealed age, hypertension, diabetes mellitus and plateletcrit were independently associated with CorT.

Conclusion

CorT was associated with increased PCT, MPV, P-LCR, NLR and PLR, even in the absence of coronary artery disease. Age, hypertension, diabetes mellitus and plateletcrit were independently associated with CorT.

Direct factor IXa inhibition with the RNA-aptamer pegnivacogin reduces platelet reactivity in vitro and residual platelet aggregation in patients with acute coronary syndromes

BACKGROUND

Residual platelet reactivity is a predictor of poor prognosis in patients with acute coronary syndromes (ACSs) undergoing percutaneous coronary intervention. Thrombin is a major platelet activator and upon initiation of the coagulation cascade, it is subsequently produced downstream of factor IXa, which itself is known to be increased in ACS. Pegnivacogin is a novel RNA-aptamer based factor IXa inhibitor featuring a reversal agent, anivamersen. We hypothesized that pegnivacogin could reduce platelet reactivity.

METHODS

Whole blood samples from healthy volunteers were incubated in vitro in the presence and absence of pegnivacogin and platelet reactivity was analysed. In addition, platelet aggregometry was performed in blood samples from ACS patients in the RADAR trial featuring the intravenous administration of pegnivacogin as well as reversal by anivamersen.

RESULTS

In vitro, pegnivacogin significantly reduced adenosine diphosphate-induced CD62P-expression (100% vs. 89.79±4.04%, p=0.027, n=9) and PAC-1 binding (100% vs. 83.02±4.08%, p=0.010, n=11). Platelet aggregation was reduced (97.71±5.30% vs. 66.53±9.92%, p=0.013, n=10) as evaluated by light transmission aggregometry. In the presence of the RNA-aptamer reversal agent anivamersen, neither CD62P-expression nor platelet aggregation was attenuated. In patients with ACS treated with aspirin and clopidogrel, residual platelet aggregation was significantly reduced 20 min after intravenous bolus of 1 mg/kg pegnivacogin (100% versus 43.21±8.23%, p=0.020).

CONCLUSION

Inhibition of factor IXa by pegnivacogin decreases platelet activation and aggregation in vitro. This effect was negated by anivamersen. In ACS patients, platelet aggregation was significantly reduced after intravenous pegnivacogin. An aptamer-based anticoagulant inhibiting factor IXa therefore might be a promising antithrombotic strategy in ACS patients.

New Developments in Platelet Cyclic Nucleotide Signalling: Therapeutic Implications

Altered platelet physiology may contribute to the emergence of thrombosis in patients with many forms of cardiovascular disease. Excess platelet activation may reflect increased stimulation of pro-aggregatory pathways. There is, however, increasing evidence that excessive platelet response, due to impaired efficacy of anti-aggregatory autacoids such as nitric oxide (NO) and prostacyclin (PGI₂), may be just as important. For example, diminished platelet response to NO has been documented in acute and chronic myocardial ischaemia, heart failure, aortic valve disease and in the presence of hyperglycaemia. This "NO resistance" has been shown to reflect both the scavenging of NO by reactive oxygen species and dysfunction of its intracellular "receptor", soluble guanylate cyclase. Importantly, these abnormalities of NO signalling are potentially reversible through judicious application of pharmacotherapy. The analogous condition of impaired PGI₂/adenylate cyclase (AC) signalling has received comparatively less attention to date. We have shown that platelet response to prostaglandin E₁ (PGE₁) is frequently impaired in patients with symptomatic myocardial ischaemia. Because the effects of ADP receptor antagonists such as clopidogrel and ticagrelor at the level of the P2Y₁₂ receptor are coupled with changes in activity of AC, impaired response to PGE₁ might imply both increased thrombotic risk and a reduced efficacy of anti-aggregatory drugs. Accordingly, patient response to treatment with clopidogrel is determined not only by variability of clopidogrel bio-activation, but also extensively by the integrity of platelet AC signalling. We here review these recent developments and their emerging therapeutic implications for thrombotic disorders.

Antiplatelet Therapy for Secondary Prevention After Acute Myocardial Infarction

Patients with prior myocardial infarction (MI) are at long-term heightened risk for recurrent ischemic events. Several large randomized controlled trials have demonstrated the benefit of more intensive antiplatelet strategies for long-term secondary prevention of cardiovascular death, recurrent MI, and stroke in patients with a history of MI at a cost of increased bleeding. The bleeding risk associated with long-term intensive antiplatelet strategies requires careful patient selection and involvement of patients in shared decision making regarding risks and benefits of therapy. Clinical characteristics, adherence to therapy, and integrated risk scores may aid clinicians in translating clinical trials into individualized therapy.

The association of carotid intima-media thickness with serum Level of perfluorinated chemicals and endothelium-platelet microparticles in adolescents and young adults

Perfluorinated chemicals (PFCs) have been widely used in a variety of products worldwide. Our previous study has documented a close association of higher serum level of perfluorooctane sulfonate (PFOS) with an increased carotid intima-media thickness (CIMT) in a cohort of adolescents and young adults. Herein, we further investigated the association of oxidative stress, circulating endothelial microparticles (EMPs) and platelet microparticles (PMPs) with PFCs and CIMT in humans. We recruited 848 subjects (12-30years old) from a population-based sample to determine the relationship between serum levels of PFCs, EMPs (CD62E and CD31+/CD42a-), PMPs (CD62P and CD31+/CD42a+), and the urine levels of 8-hydroxydeoxyguanosine (8-OHdG) and CIMT. The results showed that CD31+/CD42a- (endothelial apoptosis marker) and CD31+/CD42a+ (platelet apoptosis marker) increased significantly across quartiles of PFOS in multiple linear regression analysis. Furthermore, the elevation of CD31+/CD42a- and CD31+/CD42a+ corresponded to the increase of the odds ratios of thicker CIMT (greater than 50th percentile) with higher serum PFOS concentration (greater than 50%) (OR=2.86, 95% C.I.=1.69-4.84, P<0.001) in logistic regression models. There was no association between PFC concentration and 8-OHdG. In conclusion, we found the positive association between PFOS and CIMT that was more evident when serum levels of EMPs (CD31+/CD42a-) and PMPs (CD31+/CD42a+) were elevated. Further studies are warranted to investigate the causal inference of PFOS exposure on endothelial cell damage and atherosclerosis.

Positive association between concentration of phthalate metabolites in urine and microparticles in adolescents and young adults

Di-(2-ethylhexyl) phthalate (DEHP) has been used worldwide in various products for many years. In vitro studies have shown that exposure to DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) induces endothelial cell apoptosis. Moreover, exposure to DEHP had been linked to cardiovascular risk factors and cardiovascular diseases in epidemiological studies. Circulating microparticles have been known to be indicators of vascular injury. However, whether DEHP or its metabolites are independently associated with microparticles in humans remains unknown. From 2006 to 2008, we recruited 793 subjects (12-30years) from a population-based sample to participate in this cardiovascular disease prevention examination. Each participant was subjected to interviews and biological sample collection to determine the relationship between concentrations of DEHP metabolites MEHP, mono(ethyl-5-hydroxyhexyl) phthalate, and mono(2-ethly-5-oxoheyl) phthalate in urine and concentrations of endothelial microparticles (CD62E and CD31+/CD42a-), platelet microparticles (CD62P and CD31+/CD42a+), and CD14 in serum. Multiple linear regression analysis revealed that an ln-unit increase in MEHP concentration in urine was positively associated with an increase in serum microparticle counts/μL of 0.132 (±0.016) in CD31+/CD42a- (endothelial apoptosis marker), 0.117 (±0.023) in CD31+/CD42a+ (platelet apoptosis marker), and 0.026 (±0.007) in CD14 (monocyte, macrophage, and neutrophil activation marker). There was no association between DEHP metabolite concentration and CD62E or CD62P. In conclusion, a higher MEHP concentration in urine was associated with an increase in endothelial and platelet microparticles in this cohort of adolescents and young adults. Further studies are warranted to clarify the causal relationship between exposure to DEHP and atherosclerosis.

Platelets as Predictors of Vascular Risk: Is There a Practical Index of Platelet Activity?

Activated platelets play a role in the pathogenesis of coronary heart disease (CHD). Following activation, platelets change shape, aggregate, and release several bioactive substances. The aim of this review is to identify if there is a simple and cost-effective method that indicates platelet activation and predicts the risk of CHD and vascular events. The rationale for identifying high-risk patients is to reduce their risk of vascular events by administering appropriate and effective antiplatelet treatment, like aspirin, clopidogrel, or combination regimens. Many laboratory tests estimating platelet activity have been described. Some are relatively simple, such as spontaneous or agonist-induced platelet aggregation. Other tests include measuring the mean platelet volume (MPV) or plasma soluble P-selectin levels. Some more complex tests include flow cytometry to determine platelet GP Ilb/Illa receptors, platelet surface P-selectin, plateletmonocyte aggregates, and microparticles. Only few prospective studies assessed the predictive value of platelet activation in healthy individuals. Although the MPV seems an 'easy method, there are insufficient data supporting its ability to predict the risk of a vascular event in healthy adults. Platelet aggregation, in whole blood or in platelet-rich plasma was not consistently predictive of vascular risk. Soluble P-selectin measurement is a promising method but it needs further evaluation. Flow cytometry methods are costly, time-consuming, and need specialized equipment. Thus, they are unlikely to be useful in estimating the risk in large numbers of patients. There is as yet no ideal test for the detection of platelet activation. Each currently available test has merits and disadvantages. Simple methods such as the MPV and the determination of platelet release products need further evaluation.

Platelets and Cardiovascular Disease

Platelets play an important, but often under-recognized role in cardiovascular disease. For example, the normal response of the platelet can be altered, either by increased pro-aggregatory stimuli or by diminished anti-aggregatory substances to produce conditions of increased platelet activation/aggregation and occur in active cardiovascular disease states both on a chronic (e.g. stable angina pectoris) and acute basis (e.g. acute myocardial infarction). In addition, platelet hyperaggregability is also associated with the risk factors for coronary artery disease (e.g. smoking, hypertension, and hypercholesterolaemia). Finally, the utility of an increasing range of anti-platelet therapies in the management of the above disease states further emphasizes the pivotal role platelets play in the pathogenesis of cardiovascular disease. This paper provides a comprehensive overview of the normal physiologic role of platelets in maintain homeostasis, the pathophysiologic processes that contribute to platelet dysfunction in cardiovascular disease and the associated role and benefits of anti-platelet therapies.

Extended duration dual antiplatelet therapy in patients with myocardial infarction: A study-level meta-analysis of controlled randomized trials

BACKGROUND

Whether dual antiplatelet therapy (DAPT) is beneficial beyond 1 year after myocardial infarction (MI) is not demonstrated; in particular, available studies may be individually underpowered for end points at low incidence, that is, major and fatal bleeding or mortality. We thus assessed the effectiveness and safety of prolonged DAPT after MI over the long term.

METHODS

We conducted a systematic search to identify randomized trials on the topic; 3 studies and 21,534 post-MI patients receiving placebo or aspirin plus P2Y12 inhibition for ≥2 years were included. Incidence of the following outcome measures was evaluated: major adverse cardiac events (MACE), major bleeding, fatal bleeding, and cardiovascular and noncardiovascular death.

RESULTS

Occurrence of MACE was lower in patients treated with prolonged DAPT: 6.3% vs 7.9% in those without prolonged DAPT (odds ratios 0.74, 95% CI 0.60-0.91, P = .005); in the former, there was also a significant 16% reduction in cardiovascular mortality. Increase in major bleeding with extended duration DAPT was not significant in the overall analysis (1.5% vs 1.0%; P = .10), but became significant in the analysis restricted to patients receiving ticagrelor or prasugrel as second antiplatelet agent (odds ratios 2.16, 95% CI 1.63-2.86); prolonged use of DAPT did not raise rates of fatal bleeding or noncardiovascular mortality.

CONCLUSION

Prolonged DAPT after MI reduces MACE and cardiovascular mortality over the long term; this was paralleled by higher risk of nonfatal major bleeding mainly with the newer, more potent P2Y12 antagonists. Tailoring duration of DAPT after MI on the comparative evaluation of both ischemic and bleeding risk is mandatory in this setting.

Gender differences in risk factors and clinical outcomes in young patients with acute myocardial infarction

BACKGROUND

There are limited data on the influence of gender on risk factors and clinical outcomes in young patients with acute myocardial infarction (AMI).

METHODS

This prospective study stratified outcomes according to gender in patients of age ≤50 years with a diagnosis of AMI, and who were enrolled in the nationwide registry of the Korea Working Group of Myocardial Infarction. The end point was the incidence of major adverse cardiovascular events (MACEs) defined as the composite of cardiac death, recurrent myocardial infarction (MI), and repeat revascularisation at 30 days and 1 year after admission.

RESULTS

The registry enrolled 30 001 patients with AMI, of whom 5200 met the study inclusion criteria; 4805 patients were male and 395 were female. Current smoking was significantly higher in men, while hypertension and diabetes mellitus were significantly more common in women. Women underwent less coronary revascularisation, and were less likely to be on optimal medical therapy compared with men despite having a higher Killip class at presentation and higher risk angiographic findings. Although women had higher rates of MACEs (3.8% vs 1.8%, p=0.018 at 30 days and 7.8% vs 4.7%, p=0.004 at 1-year follow-up) compared with men, female gender was not an independent predictor of MACEs after adjusting for propensity score.

CONCLUSIONS

There were significant gender differences in the risk factors for coronary artery disease and the short-term and long-term clinical outcomes of young patients with AMI. Continued preventive strategies should be focused on gender-different risk factor reduction in these young patients.

Platelet-Mediated Thrombosis

The pivotal role that platelets play in thrombosis and resultant ischemic event occurrences in patients with high-risk coronary artery disease is well established. This role provides the fundamental basis for the current wide implementation of dual antiplatelet therapy with aspirin and a P2Y 12 receptor inhibitor. The development of user friendly point-of-care methods to assess platelet reactivity to adenosine diphosphate has increased the frequency of platelet function testing in clinical practice. Recent large observational studies have established an independent relation between the results of point-of-care platelet function testing and clinical event occurrence in patients undergoing coronary artery stenting. However, prospective, randomized trials have failed to demonstrate that personalized antiplatelet therapy based on point-of-care assessment of platelet function is effective in reducing ischemic event occurrences. Important limitations were associated with these trials. In addition, the concept of a therapeutic window of P2Y 12 receptor reactivity with an upper threshold associated with ischemic event occurrence and a lower threshold associated with bleeding has also been proposed. In the absence of strong prospective evidence to support personalized antiplatelet therapy, clinical decision making about antiplatelet therapy rests on the large body of observational data and the fundamental importance of platelet physiology in catastrophic event occurrence in patients with high-risk coronary artery disease.

Expression of the PlA2 allele of glycoprotein IIIa and its impact on platelet function

BACKGROUND

The platelet fibrinogen receptor represents the final common pathway of platelet activation, and is formed from two glycoprotein (GP) subunits (GPIIb/IIIa). Carriage of the mutant PlA2 allele of GPIIIa has been shown to confer an increased risk of cardiovascular events, but published studies have disagreed as to the mechanism for this association.

OBJECTIVES

To assess whether carriage of the PlA2 allele conforms to Mendelian patterns of expression and to identify whether carriage of the mutant allele modulates platelet function.

METHODS

Expression of the PlA2 allele was assessed in both healthy subjects (n = 25) and patients with known coronary artery disease (n = 90) through the development and validation of a liquid chromatography, tandem mass spectrometry (LC-MS/MS) assay. Platelet function was assessed in the patient cohort in response to multiple agonists, and these data were analysed in the context of the proteomic data.

RESULTS

Expression of the wild-type PlA1 allele and mutant PlA2 alleles was readily quantifiable and conformed to Mendelian patterns in both healthy and patient cohorts. Patients who were homozygous for the mutant PlA2 allele had an increased aggregatory response to adenosine diphosphate, collagen, adrenaline, ristocetin, thrombin receptor-activating peptide 6 and U46619, when assessed using agonist-concentration response curves.

CONCLUSIONS

These findings support the hypothesis that carriage of the mutant PlA2 allele mediates an increased risk of cardiovascular events through the modulation of platelet reactivity.

Recurrent acute coronary syndrome and restenosis after percutaneous coronary intervention in a patient with idiopathic thrombocytopenic purpura: a case report and literature review

BACKGROUND

Platelets play a pivotal role in the pathogenesis of acute coronary syndrome (ACS) and acute and chronic complications following percutaneous coronary intervention (PCI). Platelet inhibition is a cornerstone in the management of these patients. Idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder characterized by premature platelet destruction mediated by autoantibodies. The safety of antiplatelet therapy and PCI in patients who have ACS and ITP is unknown. The aim of the present study is to discuss the management strategies for patients who have ACS and ITP and to review limited data available in the literature.

CASE PRESENTATION

We report the case of a patient with ITP who underwent three separate coronary interventions. The first PCI with stenting was performed in the left anterior descending artery 5 years ago while the patient suffered an anterior acute myocardial infarction, and the platelet count at admission was 90 × 10(9)/L. The patient presented with recurrent ACS and severe in-stent restenosis 5 years after the first PCI, and the platelet count at admission was 18 × 10(9)/L, and elevated to 87 × 10(9)/L after platelets transfusion. He was treated successfully with cutting balloon angioplasty under anticoagulation with unfractionated heparin and antiagregation with acetylsalicylic acid and clopidogrel. Four months later after cutting balloon angioplasty, the patient received an intracoronary stent when he once again presented with recurrent ACS in the setting of restenosis. The patient has been observed for 1.5 years without restenosis after the third PCI.

CONCLUSION

We reviewed all the cases in the literature involving PCI and discussed the management strategies in patients with ITP and ACS. Available data suggest that PCI can be safe and feasible, and the risk-benefit equation of PCI procedures and antiplatelet therapies should be carefully evaluated, and the treatment should be individualized.

Association between circulating thrombopoietin levels and cardiovascular risk prediction scores in renal transplant recipients

BACKGROUND/AIMS

The 7-year Major Adverse Cardiovascular Events Calculator (CRCRTR-MACE) predicts cardiovascular events (CVE) in renal transplant recipients (RTR), and thrombopoietin (TPO) is a humoral inflammatory factor implicated in cardiovascular disease (CVD). The aim of the study was to determine if circulating TPO levels in stable RTR are positively associated with variable(s) in the CRCRTR-MACE score.

METHODS

CRCRTR-MACE scores were calculated in 95 stable RTR. TPO levels were measured by multiplexed fluorescent bead-based immunoassay in all patients and 48 controls. Multivariate analysis (MVA) was performed between TPO and CV risk variables and patient demographics. Stepwise regression with backward elimination of insignificant variables estimated the impact of risk variables on TPO levels. Significance was defined at p < 0.05. Normalized data were presented as mean ± SD and non-normalized data as median (maximum to minimum).

RESULTS

The risk of a CVE within 7 years as predicted by the median was 9.97% (range 1.93-84.2). The percentage of patients who were above 20% risk for a CVE was 28.4%. Control TPO level of 170.41 (4.4-995.9) pg/ml was significantly lower than that of 237.90 (32.77-1,386.79) pg/ml in RTR (p = 0.010). TPO level correlated significantly with the total CRCRTR-MACE score (R = 0.310, p = 0.004), smoking (p = 0.009) and eGFR (R = -0.275, p = 0.012) but not with age, diabetes, LDL level or history of CVE. Only the total CRCRTR-MACE score (p = 0.013) and smoking (p = 0.009) remained significant in the MVA. Stepwise regression estimated that smoking increased TPO levels by 206.28 pg/ml and each 10% increase in CRCRTR-MACE score increased TPO levels by an additional 44.4 pg/ml.

CONCLUSION

TPO levels are increased in RTR with high CRCRTR-MACE, particularly in smokers with diminished eGFR. Circulating TPO may serve as a biomarker and treatment target for CVD in RTR.

Prognostic value of angiographic lesion complexity in patients with acute coronary syndromes undergoing percutaneous coronary intervention (from the acute catheterization and urgent intervention triage strategy trial)

Although lesion complexity is predictive of outcomes after balloon angioplasty, it is unclear whether complex lesions continue to portend a worse prognosis in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) with contemporary interventional therapies. We sought to assess the impact of angiographic lesion complexity, defined by the modified American College of Cardiology/American Heart Association classification, on clinical outcomes after PCI in patients with ACS and to determine whether an interaction exists between lesion complexity and antithrombin regimen outcomes after PCI. Among the 3,661 patients who underwent PCI in the Acute Catheterization and Urgent Intervention Triage strategy study, patients with type C lesions (n = 1,654 [45%]) had higher 30-day rates of mortality (1.2% vs 0.6%, p = 0.049), myocardial infarction (9.2% vs 6.3%, p = 0.0006), and unplanned revascularization (4.3% vs 3.1%, p = 0.04) compared with those without type C lesions. In multivariate analysis, type C lesions were independently associated with myocardial infarction (odds ratio [95% confidence interval] = 1.37 [1.04 to 1.80], p = 0.02) and composite ischemia (odds ratio [95% confidence interval] = 1.49 [1.17 to 1.88], p = 0.001) at 30 days. Bivalirudin monotherapy compared with heparin plus a glycoprotein IIb/IIIa inhibitor reduced major bleeding complications with similar rates of composite ischemic events, regardless of the presence of type C lesions. There were no interactions between antithrombotic regimens and lesion complexity in terms of composite ischemia and major bleeding (p [interaction] = 0.91 and 0.80, respectively). In conclusion, patients with ACS with type C lesion characteristics undergoing PCI have an adverse short-term prognosis. Treatment with bivalirudin monotherapy reduces major hemorrhagic complications irrespective of lesion complexity with comparable suppression of adverse ischemic events as heparin plus glycoprotein IIb/IIIa inhibitor.

The independent assocıatıon of plateletcrıt wıth long-term outcomes in patıents undergoıng prımary percutaneous coronary interventıon

PURPOSE

Platelets play a key role in the genesis of thrombosis. Plateletcrit (PCT) provides complete information on total platelet mass. The relationship between PCT values and long-term outcomes in patients with ST-segment elevation myocardial infarction (STEMI) who undergo primary angioplasty is not known. We sought to determine the effect of PCT values on the outcomes of primary angioplasty for STEMI.

METHODS

Overall, 2572 consecutive STEMI patients (mean age, 56.6±11.8 years) undergoing primary percutaneous coronary intervention were enrolled retrospectively into the present study. Plateletcrit at admission was measured as part of the automated complete blood count. Patients were classified into 2 groups: high PCT (>0.237, n=852) and nonhigh PCT (<0.237, n=1720). Clinical characteristics and in-hospital and long-term (median, 21 months) outcomes of primary angioplasty were analyzed.

RESULTS

A higher in-hospital shock rate was observed among patients with high PCT values compared with those with nonhigh PCT values (6.5 vs 3.8%, respectively; P=.003). The long-term cardiovascular prognosis was worse for patients with high PCT values (Kaplan-Meier, log-rank test; P=.007). We used Cox proportional hazard models to examine the association between PCT and adverse clinical outcomes. High PCT values were also an independent predictor of cardiovascular mortality (hazard ratio, 1.85; 95% confidence interval, 1.061-3.22; P=.03).

CONCLUSION

High PCT values on admission are independently associated with long-term adverse outcomes in patients with STEMI who undergo primary angioplasty.

Mean platelet volume is associated with myocardial perfusion defect in diabetic patients

Aim

Our aim was to evaluate whether there was a relationship between mean platelet volume and myocardial perfusion defect in diabetic patients using myocardial perfusion imaging.

Method

Forty-four diabetic patients with myocardial perfusion defect (group 1) and 44 diabetic patients without myocardial perfusion defect (group 2), matched for age and gender, were retrospectively examined. Levels of mean platelet volume (MPV) in the two groups were assessed.

Results

MPV was higher in group 1 than group 2 patients (8.76 ± 0.76 and 8.25 ± 0.78 fl), respectively, p = 0.003). Levels of glucose, triglycerides (TG), total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, haemoglobin (Hb) and glycosylated haemoglobin (HbA_1c), and body mass index (BMI) in the two groups were not statistically significantly different. Multivariate logistic regression analyses showed that MPV was the only variable independently associated with myocardial perfusion defects (OR: 2.401, 95% CI: 1.298–4.440, p = 0.013).

Conclusion

This study showed that higher MPV was associated with myocardial perfusion defects. Higher MPV in diabetic patients was independently related to myocardial perfusion defects and may be an indicator of myocardial ischaemia.

Neutrophil–Lymphocyte Ratio and Platelet–Lymphocyte Ratio Combination Can Predict Prognosis in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

We assessed the effect of combination of neutrophil–lymphocyte ratio (NLR) and platelet–lymphocyte ratio (PLR) in predicting in-hospital and long-term mortality in patients (n = 2518) undergoing primary percutaneous coronary intervention (pPCI). Cutoff values for NLR and PLR were calculated with receiver–operating characteristic (ROC) curves. If both PLR and NLR were above the threshold, patients were classified as “high risk.” If either PLR or NLR was above the threshold individually, patients were classified as “intermediate risk.” High-risk (n = 693) and intermediate-risk (n = 545) groups had higher in-hospital and long-term mortality (7.2 4% vs 0.7%, P < .001; 14.1, 9.5% vs 4.5%, P < .001, respectively). Classifying patients into intermediate-risk group (hazards ratio [HR]: 1.492, 95% confidence interval [CI]: 1.022-2.178, P = .038) and high-risk group (HR: 1.845, 95% CI: 1.313-2.594, P < .001) was an independent predictor of in-hospital and long-term mortality. The combination of PLR and NLR can be useful for the prediction of in-hospital and long-term mortality in patients undergoing pPCI.

Point-of-care assessment of platelet reactivity in the emergency department may facilitate rapid rule-out of acute coronary syndromes: a prospective cohort pilot feasibility study

OBJECTIVE

Accurate, efficient and cost-effective disposition of patients presenting to emergency departments (EDs) with symptoms suggestive of acute coronary syndromes (ACS) is a growing priority. Platelet activation is an early feature in the pathogenesis of ACS; thus, we sought to obtain an insight into whether point-of-care testing of platelet function: (1) may assist in the rule-out of ACS; (2) may provide additional predictive value in identifying patients with non-cardiac symptoms versus ACS-positive patients and (3) is logistically feasible in the ED.

DESIGN

Prospective cohort feasibility study.

SETTING

Two urban tertiary care sites, one located in the USA and the second in Argentina.

PARTICIPANTS

509 adult patients presenting with symptoms of ACS.

MAIN OUTCOME MEASURES

Platelet reactivity was quantified using the Platelet Function Analyzer-100, with closure time (seconds required for blood, aspirated under high shear, to occlude a 150 µm aperture) serving as the primary endpoint. Closure times were categorised as 'normal' or 'prolonged', defined objectively as the 90th centile of the distribution for all participants enrolled in the study. Diagnosis of ACS was made using the standard criteria. The use of antiplatelet agents was not an exclusion criterion.

RESULTS

Closure times for the study population ranged from 47 to 300 s, with a 90th centile value of 138 s. The proportion of patients with closure times ≥138 s was significantly higher in patients with non-cardiac symptoms (41/330; 12.4%) versus the ACS-positive cohort (2/105 (1.9%); p=0.0006). The specificity of 'prolonged' closure times (≥138 s) for a diagnosis of non-cardiac symptoms was 98.1%, with a positive predictive value of 95.4%. Multivariate analysis revealed that the closure time provided incremental, independent predictive value in the rule-out of ACS.

CONCLUSIONS

Point-of-care assessment of platelet reactivity is feasible in the ED and may facilitate the rapid rule-out of ACS in patients with prolonged closure times.

Development of glycoprotein IIb–IIIa antagonists: translation of pharmacodynamic effects into clinical benefit

This article will review the development of glycoprotein IIb-IIIa antagonists, with particular emphasis on the characteristics and pharmacodynamic studies of each agent that is available for clinical use. Abciximab is a Fab fragment of the 7E3 antibody that has high affinity and a slow rate of dissociation from glycoprotein IIb-IIIa. In contrast, the small molecules eptifibatide and tirofiban, have a much more rapid rate of dissociation, with an off time of 10 to 15 s. Accordingly, the circulating pool of abciximab is predominantly associated with platelets, whereas maintenance of a consistent concentration of tirofiban and eptifibatide in the blood is critical in order to achieve and sustain their inhibitory effects. The affinity of abciximab and tirofiban for glycoprotein IIb-IIIa are substantially greater than that of eptifibatide, necessitating maintenance of greater molar concentrations of eptifibatide in blood in order to achieve effective inhibition of the binding of fibrinogen to the activated conformer of glycoprotein IIb-IIIa.