Platelet function in acute myocardial infarction treated with direct angioplasty

Prognostic Implications of Immature Platelet Fraction at 5-Year Follow-up Among ACS Patients Treated With Dual Antiplatelet Therapy

Objective: Platelets are strongly associated with cardiovascular events due to their role in thrombotic processes. Reticulated platelets have higher prothrombotic potential. The aim of the study was to evaluate the effectiveness of immature platelet fraction (IPF) in predicting long-term clinical outcomes in patients with acute coronary syndrome (ACS). Methods: This prospective, observational study enrolled patients with ACS treated with dual antiplatelet therapy comprising acetylsalicylic acid and clopidogrel or ticagrelor. The primary outcome was a composite endpoint defined as major adverse cardiovascular events (MACE): all-cause death, myocardial infarction (MI), ischemic stroke, or unplanned revascularization. IPF was determined using flow cytometry in the first 24 h of hospitalization. MACE were evaluated by 2 physicians based on electronic databases and source documentation including discharge letters received from patients upon telephone contact. Results: Overall, there were 140 ACS patients (mean age 65.1 ± 11.7, 37 females [26.4%]) included in this study. Of them, 22.9% had diabetes mellitus, 69.3% hyperlipidemia, 25% had a history of MI. The median IPF values were 2.85 [1.8-4.2] %. Clinical follow-up (median time: 57 months [interquartile range 55-59 months]) was available for 130 patients (92.9%). MACE occurred in 27 patients (20.8%). There were higher rates of MACE at higher IPF tertiles (3rd vs 1st tertile: HR = 5.341 95% CI: 1.546-18.454, P = .008). Cox regression analyses showed that IPF level was independently associated with MACE. Time-dependent receiver-operating characteristic curve analysis revealed area under the curve of 0.656 for 5-year outcome with an IPF cutoff point of 3.45% being 63.0% sensitive and 65.0% specific for MACE. Conclusions: The study showed IPF may be an independent predictor of long-term mortality and MACE (ClinicalTrials.gov number, NCT06177587).

Individualization of Duration of Dual Antiplatelet Therapy after Coronary Stenting: A Comprehensive, Evidence-Based Review

Dual antiplatelet therapy (DAPT), comprising aspirin and a P2Y12 receptor inhibitor, is the cornerstone of post-percutaneous coronary intervention treatment to prevent stent thrombosis and reduce the risk of adverse cardiovascular events. The selection of an optimal DAPT regimen, considering the interplay of various antiplatelet agents, patient profiles, and procedural characteristics, remains an evolving challenge. Traditionally, a standard duration of 12 months has been recommended for DAPT in most patients. While contemporary guidelines provide general frameworks, DAPT modulation with longer or shorter treatment courses followed by aspirin or P2Y12 inhibitor monotherapy are evolving towards an individualized strategy to optimize the balance between efficacy and safety. This review comprehensively examines the current landscape of DAPT strategies after coronary stenting, with a focus on emerging evidence for treatment individualization.

Current concepts and novel targets for antiplatelet therapy

Platelets have a crucial role in haemostasis and atherothrombosis. Pharmacological control of platelet hyper-reactivity has become a cornerstone in the prevention of thrombo-ischaemic complications in atherosclerotic diseases. Current antiplatelet therapies substantially improve clinical outcomes in patients with coronary artery disease, but at the cost of increased risk of bleeding. Beyond their role in thrombosis, platelets are known to regulate inflammatory (thrombo-inflammatory) and microcirculatory pathways. Therefore, controlling platelet hyper-reactivity might have implications for both tissue inflammation (myocardial ischaemia) and vascular inflammation (vulnerable plaque formation) to prevent atherosclerosis. In this Review, we summarize the pathophysiological role of platelets in acute myocardial ischaemia, vascular inflammation and atherosclerotic progression. Furthermore, we highlight current clinical concepts of antiplatelet therapy that have contributed to improving patient care and have facilitated more individualized therapy. Finally, we discuss novel therapeutic targets and compounds for antiplatelet therapy that are currently in preclinical development, some of which have a more favourable safety profile than currently approved drugs with regard to bleeding risk. These novel antiplatelet targets might offer new strategies to treat cardiovascular disease.

Clinical pharmacology of selatogrel for self-administration by patients with suspected acute myocardial infarction

INTRODUCTION

P2Y12 receptor antagonists (P2Y12 inhibitors) are well established for the treatment of coronary artery disease. The P2Y12 inhibitors currently commercially available present either pharmacokinetic limitations (due to delayed absorption, bioactivation requirement via CYP enzymes, or need of intravenous administration), pharmacodynamic (PD) limitations (limited % inhibition of platelet aggregation (IPA) or relevant PD interactions) or safety limitations (major bleeding in specific populations).

AREAS COVERED

Selatogrel, a 2-phenylpyrimidine-4-carboxamide analog, is a potent, reversible, and selective P2Y12 inhibitor administered subcutaneously that is under development for the treatment of acute myocardial infarction (AMI) in patients with a recent history of AMI. In this review, the authors summarize the results from preclinical, phase 1, and phase 2 trials which showed that selatogrel provides rapid, pronounced, and reversible P2Y12 receptor inhibition with a favorable safety profile.

EXPERT OPINION

These unique characteristics added to the limited potential to interact with co-medications and manageable PD interactions with other P2Y12 inhibitors provide a clear rationale for investigating the benefit of selatogrel as an emergency treatment to improve clinical outcomes in patients with AMI.

Revealing concealed cardioprotection by platelet Mfsd2b-released S1P in human and murine myocardial infarction

Antiplatelet medication is standard of care in acute myocardial infarction (AMI). However, it may have obscured beneficial properties of the activated platelet secretome. We identify platelets as major source of a sphingosine-1-phosphate (S1P) burst during AMI, and find its magnitude to favorably associate with cardiovascular mortality and infarct size in STEMI patients over 12 months. Experimentally, administration of supernatant from activated platelets reduces infarct size in murine AMI, which is blunted in platelets deficient for S1P export (Mfsd2b) or production (Sphk1) and in mice deficient for cardiomyocyte S1P receptor 1 (S1P₁). Our study reveals an exploitable therapeutic window in antiplatelet therapy in AMI as the GPIIb/IIIa antagonist tirofiban preserves S1P release and cardioprotection, whereas the P2Y12 antagonist cangrelor does not. Here, we report that platelet-mediated intrinsic cardioprotection is an exciting therapeutic paradigm reaching beyond AMI, the benefits of which may need to be considered in all antiplatelet therapies.

P2Y12 Inhibitor Monotherapy versus Conventional Dual Antiplatelet Therapy in Patients with Acute Coronary Syndrome after Percutaneous Coronary Intervention: A Meta-Analysis

P2Y12 inhibitor monotherapy is a feasible alternative treatment for patients after percutaneous coronary intervention (PCI) in the modern era. Clinical trials have shown that it could lower the risk of bleeding complications without increased ischemic events as compared to standard dual antiplatelet therapy (DAPT). However, the efficacy and safety of this novel approach among patients with acute coronary syndrome (ACS) are controversial because they have a much higher risk for recurrent ischemic events. The purpose of this study is to evaluate the efficacy and safety of this novel approach among patients with ACS. We conducted a meta-analysis of randomized controlled trials that compared P2Y12 inhibitor monotherapy with 12-month DAPT in ACS patients who underwent PCI with stent implantation. PubMed, Embase, the Cochrane library database, ClinicalTrials.gov, and other three websites were searched for data from the earliest report to July 2022. The primary efficacy outcome was major adverse cardiovascular and cerebrovascular events (MACCE), a composite of all-cause mortality, myocardial infarction, stent thrombosis, or stroke. The primary safety outcome was major or minor bleeding events. The secondary endpoint was net adverse clinical events (NACE), defined as a composite of major bleeding and adverse cardiac and cerebrovascular events. Five randomized controlled trials with a total of 21,034 patients were included in our meta-analysis. The quantitative analysis showed a significant reduction in major or minor bleeding events in patients treated with P2Y12 inhibitor monotherapy as compared with standard DAPT(OR: 0.59, 95% CI: 0.46-0.75, p < 0.0001) without increasing the risk of MACCE (OR: 0.98, 95% CI: 0.86-1.13, p = 0.82). The NACE was favorable in the patients treated with P2Y12 inhibitor monotherapy (OR: 0.82, 95% CI: 0.73-0.93, p = 0.002). Of note, the overall clinical benefit of P2Y12 inhibitor monotherapy was quite different between ticagrelor and clopidogrel. The incidence of NACE was significantly lower in ticagrelor monotherapy as compared with DAPT (OR: 0.79, 95% CI: 0.68-0.91), but not in clopidogrel monotherapy (OR: 1.14, 95% CI: 0.79-1.63). Both clopidogrel and ticagrelor monotherapy showed a similar reduction in bleeding complications (OR: 0.46, 95% CI: 0.22-0.94; OR: 0.60, 95% CI: 0.44-0.83, respectively). Although statistically insignificant, the incidence of MACCE was numerically higher in clopidogrel monotherapy as compared with standard DAPT (OR: 1.50, 95% CI: 0.99-2.28, p = 0.06). Based on these findings, P2Y12 inhibitor monotherapy with ticagrelor would be a better choice of medical treatment for ACS patients after PCI with stent implantation in the current era.

P66Shc (Shc1) Zebrafish Mutant Line as a Platform for Testing Decreased Reactive Oxygen Species in Pathology

Reactive oxygen species (ROS) dysregulation exacerbates many pathologies but must remain within normal ranges to maintain cell function. Since ROS-mediated pathology and routine cell function are coupled, in vivo models evaluating low-ROS background effects on pathology are limited. Some models alter enzymatic antioxidant expression/activity, while others involve small molecule antioxidant administration. These models cause non-specific ROS neutralization, decreasing both beneficial and detrimental ROS. This is detrimental in cardiovascular pathology, despite the negative effects excessive ROS has on these pathologies. Thus, current trends in ROS-mediated pathology have shifted toward selective inhibition of ROS producers that are dysregulated during pathological insults, such as p66Shc. In this study, we evaluated a zebrafish heterozygote p66Shc hypomorphic mutant line as a low-ROS myocardial infarction (MI) pathology model that mimics mammalian MI. Our findings suggest this zebrafish line does not have an associated negative phenotype, but has decreased body mass and tissue ROS levels that confer protection against ROS-mediated pathology. Therefore, this line may provide a low-ROS background leading to new insights into disease.

Prognostic and Practical Validation of ESC/EACTS High Ischemic Risk Definition on Long-Term Thrombotic and Bleeding Events in Contemporary PCI Patients

AIMS

The ESC/EACTS myocardial revascularization guidelines recently standardized the definition of patients at high ischemic risk (HIR). However, the ability of ESC/EACTS-HIR criteria to stratify ischemic and bleeding risk in a contemporary real-world East Asian cohort remains unexplored.

METHODS

A total of 10,167 consecutive patients undergoing PCI from prospective Fuwai PCI Registry (January 2013 to December 2013) were reviewed. ESC/EACTS-HIR features was defined as having at least one of the eight clinical and angiographic characteristics. The primary ischemic endpoint was target vessel failure (cardiac death, target vessel myocardial infarction [MI], or target vessel revascularization [TVR]); bleeding outcome was assessed using the BARC type 2, 3, or 5 bleeding. Median follow-up was 29 months.

RESULTS

Compared with non-HIR patients, HIR patients (n=5,149, 50.6%) were associated with increased risk for target vessel failure (adjusted hazard ratio [HRadjust]: 1.48 [1.25-1.74]) and patient-oriented composite outcome (HRadjust: 1.44 [1.28-1.63]), as well as cardiac death, MI, and TVR. By contrast, the risk of clinically relevant bleeding was not significantly different between the two groups. (HRadjust: 0.84 [0.66-1.06]). Greater than or equal to three implanted stents and diabetic patients with diffuse multivessel coronary disease emerged as independent predictors for long-term adverse outcomes. There was no significant interaction between high bleeding risk (HBR) status and clinical outcomes associated with ESC/EACTS-HIR criteria (all Pinteraction ＞0.05).

CONCLUSION

The ESC/EACTS-HIR features identified patients at increased risk of thrombotic events, including cardiac death, but not for clinically relevant bleeding. Importantly, HBR did not modify cardiovascular risk subsequent to patients with ESC/EACTS-HIR features, suggesting its potential clinical applicability in tailoring antithrombotic therapy.

Effectiveness and Safety of P2Y12 Inhibitors Pretreatment in Primary Percutaneous Coronary Intervention with Long Transfer Times

BACKGROUND

Early initiation of a new P2Y12 inhibitor in ST-elevation myocardial infarction (STEMI) patients prior to primary percutaneous coronary intervention (PCI) is recommended over clopidogrel. However, comparative data remain limited, especially in semi-rural regions with subsequent longer transfer times.

OBJECTIVES

We aimed to assess the determinants, effectiveness, and safety of pretreatment with new P2Y12 inhibitors compared with clopidogrel in a primary PCI regional network.

METHODS

Outcomes of 1235 primary PCI patients pretreated with new P2Y12 inhibitors (n = 1050) or clopidogrel (n = 185) were evaluated using a prospective registry. Primary effectiveness endpoint was the composite of death, recurrent myocardial infarction, stroke, or new revascularization. Serious bleedings were defined as Bleeding Academic Research Consortium ≥ 2.

RESULTS

Clopidogrel was more likely to be used in older and female patients with more comorbidities. Mean transfer time was longer in the clopidogrel group (123.3 ± 67.3 vs. 102.3 ± 57.2 min; p < 0.01). The primary endpoint was less frequent with new P2Y12 inhibitors compared with clopidogrel (14.9 vs. 30.3%; odds ratio 0.58, 95% confidence interval [CI] 0.39-0.87; p < 0.01), mostly driven by a reduced rate of death (4.5 vs. 26% respectively; hazard ratio 0.25, 95% CI 0.16-0.38; p < 0.01). Bleeding rates did not differ between groups (1 vs. 0.5%, respectively; p = 0.96).

CONCLUSION

Compared with clopidogrel, pretreatment with new P2Y12 inhibitors seems to be associated with lower risks of mortality and ischemic outcomes, and similar risks of bleeding in a real-world registry. Our results are in line with the guidelines recommending the preferential pre-PCI administration of new P2Y12 inhibitors in STEMI patients referred for primary PCI.

Thrombosis in COVID-19 infection: Role of platelet activation-mediated immunity

Background

Thrombosis plays an important role in the Coronavrus Disease 2019 (COVID-19) infection-related complications such as acute respiratory distress syndrome and myocardial infarction. Multiple factors such as oxygen demand injuries, endothelial cells injury related to infection, and plaque formation.

Main body

Platelets obtained from the patients may have severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA, showing that the increased activation potential recommends platelet can be hyper-activated in severely ill SARS-CoV-2 cases. Platelets contain multiple receptors that interact with specific ligands. Pathogen’s receptors such as Toll-like receptors (TLRs), NOD-like receptor, C-type lectin receptor family, glycoprotein (GP) such as GPαIIbβ3 and GPIbα which allow pathogens to interact with platelets. Platelet TLRs and NOD2 are involved in platelet activation and thrombosis. Accordingly, TLRs are critical receptors that could recognize various endogenous damage-associated molecular patterns and exogenous pathogen-associated molecular patterns (PAMPs). TLRs are considered as important components in the activation of innate immunity response against pathogenic and non-pathogenic components like damaged tissues. TLRs-1,-2,-4,-6,-7 expression on or within platelets has been reported previously. Various PAMPs were indicated to be capable of binding to platelet-TLRs and inducing both the activation and promotion of downstream proinflammatory signaling cascade.

Conclusion

It is possible that the increased TLRs expression and TLR-mediated platelets activation during COVID-19 may enhance vascular and coronary thrombosis. It may be hypothesized using TLRs antagonist and monoclonal antibody against P-selectin, as the marker of leukocyte recruitment and platelet activation, besides viral therapy provide therapeutic advances in fighting against the thrombosis related complications in COVID-19.

Study on the interaction mechanism between C-reactive protein and platelets in the development of acute myocardial infarction

Background

Myocardial infarction (MI) is the single most critical event in coronary disease. Platelets are involved in the processes of acute MI (AMI). They lack nuclear DNA but retain megakaryocyte mRNAs, hence, their transcriptome could provide information preceding coronary events. However, their mechanisms are not clear. In this study, we obtained a gene expression atlas of platelets from patients after their very first AMI, and our purpose was to clarify the mechanisms of platelet involvement in the occurrence of AMI through bioinformatics analyses and animal models of AMI in vivo.

Methods

We obtained a gene expression atlas of platelets from patients after their very first AMI from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were retrieved using R language. Weighted gene co-expression network analysis (WGCNA) was implemented in order to construct a gene co-expression correlation network among DEGs. Animal models of AMI in vivo were constructed to confirm the results of the bioinformatics analysis.

Results

Gene integration analysis yielded 2,852 DEGs (P<0.05, |log2FC| >1). Bioinformatics analysis demonstrated a significant association between C-reactive protein (CRP) and Staphylococcus aureus infection (SAI) (P=0.015). Data from in vivo experiments showed that CRP increased significantly in AMI rats (P<0.001), and the expression of FCGR2B mRNA and HLA-DRB4 mRNA was elevated in response to the increase of CRP (P<0.001).

Conclusions

From the results of this study, we speculate that in the development of AMI, the increase in CRP activates platelets and induces platelets to play an anti-inflammatory role.

Pharmacokinetic/pharmacodynamic modeling of drug interactions at the P2Y12 receptor between selatogrel and oral P2Y12 antagonists

Selatogrel is a potent and reversible P2Y₁₂ receptor antagonist developed for subcutaneous self‐administration by patients with suspected acute myocardial infarction. After single‐dose emergency treatment with selatogrel, patients are switched to long‐term treatment with oral P2Y₁₂ receptor antagonists. Selatogrel shows rapid onset and offset of inhibition of platelet aggregation (IPA) to overcome the critical initial time after acute myocardial infarction. Long‐term benefit is provided by oral P2Y₁₂ receptor antagonists such as clopidogrel, prasugrel, and ticagrelor. A population pharmacokinetic (PK)/pharmacodynamic (PD) model based on data from 545 subjects in 4 phase I and 2 phase II studies well described the effect of selatogrel on IPA alone and in combination with clopidogrel, prasugrel, and ticagrelor. The PK of selatogrel were described by a three‐compartment model. The PD model included a receptor‐pool compartment to which all drugs can bind concurrently, reversibly or irreversibly, depending on their mode of action. Furthermore, ticagrelor and its active metabolite can bind to the selatogrel‐receptor complex allosterically, releasing selatogrel from the binding site. The model provided a framework for predicting the effect on IPA of selatogrel followed by reversibly and irreversibly binding oral P2Y₁₂ receptor antagonists for sustained effects. Determining the timepoint for switching from emergency to maintenance treatment is critical to achieve sufficient IPA at all times. Simulations based on the interaction model showed that loading doses of clopidogrel and prasugrel administered 15 h and 4.5 h after selatogrel, respectively, provide sustained IPA with clinically negligible drug interaction.

Residual platelet reactivity after pre-treatment with ticagrelor prior to primary percutaneous coronary intervention is associated with suboptimal myocardial reperfusion

BACKGROUND

The evidence of a clinical benefit of P2Y12 inhibitor pre-treatment in primary percutaneous coronary intervention (PCI) and the relation between the level of platelet inhibition and myocardial reperfusion with newer potent P2Y12 inhibitors remain unclear. We aimed to assess the relationship between platelet reactivity at the time of primary PCI after pre-treatment with aspirin and ticagrelor and the post-PCI myocardial blush grade (MBG).

METHODS

We prospectively included 61 patients. Platelet reaction units for ticagrelor (PRU) and aspirin reaction units (ARU) were measured using the point-of-care test VerifyNow before PCI. The high on-ticagrelor (PRU >208) and on-aspirin (ARU ⩾ 550) platelet reactivity (HPR and HaPR) were assessed. Patients were divided into two groups according to MBG 3 or <3.

RESULTS

MBG 3 was identified in 28 (46%) patients. Mean PRU was lower in such patients as compared with those with MBG <3 (155.82 ± 90.91 vs. 227.42 ± 65.18; p=0.001) while mean ARU was similar between groups. HPR and HaPR were observed in 30 (49.2%) and 11 patients (18%), respectively. HPR but not HaPR was more frequent in the group with impaired MBG (66.7 vs. 28.6%; p=0.003 and 21.2 vs. 14.3%; p=0.48 respectively).

CONCLUSION

Our study shows that higher PRU and the subsequent HPR at the time of primary PCI, after pretreatment with ticagrelor, are the only correlates of post PCI MBG. These findings support the earliest possible loading with ticagrelor prior to primary PCI.

Cell-Derived Microparticles and Acute Coronary Syndromes: Is there a Predictive Role for Microparticles?

Background:

Despite the recent advances in the treatment of Acute Coronary Syndromes (ACS), patients with ACS are still exposed to an increased risk for adverse cardiovascular events, while their prognosis is difficult to determine. Experimental and clinical studies have shown that cell-derived Microparticles (MPs) are associated with the underlying pathophysiological processes that are responsible for atherogenesis and may be causally implicated in the induction of atherothrombosis.

Objective:

In the present article, we aimed to review the available evidence regarding the predictive role of MPs in patients with ACS.

Results:

Evidence suggests that endothelial MPs are associated with future adverse cardiovascular events in patients with ACS. Platelet-derived MPs have been excessively studied, since they have been found to trigger the coagulation cascade; however, their role as predictors of future cardiovascular events remains debatable. The role of red blood cell-derived MPs is more intriguing; they have been proposed as markers of ongoing thrombosis in patients with ACS, while previous studies have shown that they have anti-coagulant properties in healthy individuals. Leukocyte-derived MPs may also have a predictive role, although the studies regarding these are still limited. Last but not least, it was an interesting discovery that circulating MPs can provide information regarding the angiographic lesions in patients with ACS.

Conclusion:

The concept of MPs as potential circulating biomarkers in patients with ACS holds much promise. However, large-scale clinical studies are required to evaluate whether the measurement of plasma MPs could be of clinical significance and, thus, dictate a more aggressive treatment strategy in patients with high levels of circulating MPs.

Benefit-Risk Profile of DAPT Continuation Beyond 1 Year after PCI in Patients with High Thrombotic Risk Features as Endorsed by 2018 ESC/EACTS Myocardial Revascularization Guideline

PURPOSE

The ischemic/bleeding trade-off of continuing dual antiplatelet therapy (DAPT) beyond 1 year after PCI for patients with high thrombotic risk (HTR) as endorsed by 2018 ESC/EACTS myocardial revascularization guidelines remain unknown.

METHODS

Patients undergoing coronary stenting between January 2013 and December 2013 from the prospective Fuwai registry were defined as HTR if they met at least 1 ESC/EACTS guideline-endorsed HTR criteria. A total of 4578 patients who were at HTR and were events free at 1 year after the index procedure were evaluated. The primary efficacy outcome was major adverse cardiac and cerebrovascular events (MACCE) (composite of all-cause death, myocardial infarction, or stroke).

RESULTS

Median follow-up period was 2.4 years. > 1-year DAPT with clopidogrel and aspirin significantly reduced the risk of MACCE compared with ≤ 1-year DAPT (1.9% vs. 4.6%; hazard ratio (HR): 0.38; 95% confidence interval (CI): 0.27-0.54; P < 0.001), driven by a reduction in all-cause death (0.2% vs. 3.0%; HR, 0.07; 95% CI, 0.03-0.15). Cardiac death and definite/probable stent thrombosis also occurred less frequently in prolonged DAPT group. Bleeding Academic Research Consortium (BARC) type 2, 3, or 5 bleeding occurred similarly between both groups (1.1% vs. 0.9%; HR, 1.11; 95% CI, 0.58-2.13; P = 0.763). Similar results were found using multivariable Cox model, propensity score-matched, and inverse probability of treatment weighting analysis.

CONCLUSIONS

Among patients with ESC-endorsed HTR who were free from major ischemic or bleeding events 1 year after coronary stenting, continued DAPT beyond 1 year might offer better effectiveness in terms of atherothrombotic events and comparable safety in terms of clinically relevant bleeding compared with ≤ 1-year DAPT. ESC-HTR criteria is an important parameter to take into account in tailoring DAPT prolongation.

Platelet inhibition with standard vs. lower maintenance dose of ticagrelor early after myocardial infarction (ELECTRA): a randomized, open-label, active-controlled pharmacodynamic and pharmacokinetic study

AIMS

Currently available data indicate that reduction of ticagrelor maintenance dose (MD) 1-3 years after acute myocardial infarction (AMI) not only provides sufficient platelet inhibition but also can improve ticagrelor's safety profile. The aim of this study was to compare the antiplatelet effect of reduced and standard ticagrelor MD in stable patients beginning 1 month after AMI.

METHODS AND RESULTS

In a single-centre, randomized, open-label, active-controlled trial, on Day 30 following AMI, 52 patients (26 in each study arm) were assigned in a 1:1 ratio to receive either reduced (60 mg b.i.d) or standard (90 mg b.i.d) ticagrelor MD for the following 2 weeks. On Day 45 after AMI the antiplatelet effect of ticagrelor was evaluated with the VASP assay and Multiplate, and there were no significant differences in platelet inhibition between patients on reduced vs. standard MD [VASP: 10.4 (5.6-22.2) vs. 14.1 (9.4-22.1) platelet reactivity index; P = 0.30; Multiplate: 30.0 (24.0-39.0) vs. 26.5 (22.0-35.0) U; P = 0.26]. Likewise, no differences were found regarding the prevalence of on-ticagrelor high platelet reactivity between patients on ticagrelor 60 mg b.i.d vs. 90 mg b.i.d (VASP: 4% vs. 8%; P = 0.67; Multiplate: 15% vs. 8%; P = 0.54). Administration of reduced MD resulted in proportionally lower plasma concentrations of ticagrelor and its active metabolite on Day 45 after AMI.

CONCLUSION

These results suggest that lowering ticagrelor MD 1 month after AMI confers an adequate antiplatelet effect that is comparable to the standard dose. The tested strategy warrants further research to assess its clinical efficacy and safety.

CLINICALTRIALS.GOV IDENTIFIER

NCT03251859.

Clopidogrel or prasugrel reduces mortality and lessens cardiovascular damage from acute myocardial infarction in hypercholesterolemic male rats

AIMS

Hypercholesterolemia is a hazard for increasing susceptibility of the heart to myocardial infarction (MI) by inducing platelet hyperaggregability. Clopidogrel and prasugrel have documented cardioprotective effects in clinical studies. Herein, we investigated whether clopidogrel and prasugrel could protect against isoproterenol-induced acute MI (A-MI) under hypercholesterolemic conditions in rats.

MAIN METHODS

Dietary hypercholesterolemic rats were subjected to acute doses of isoproterenol. Serum lipids, inflammatory markers, aortic endothelin1 and endothelial nitric oxide synthase (eNOS) mRNAs expression and immunexpression of BCL2 were determined.

KEY FINDINGS

Hypercholesterolemic rats showed infiltration of inflammatory cells and reduction in aortic wall thickness, deposition of fibrous tissue between cardiac muscle fibers. Protective doses of prasugrel or clopidogrel for 28 days before A-MI increased survival, amended the ECG parameters -including ST segment elevation- and improved the histopathological picture in hypercholesterolemic rats. This was coupled with reductions in platelet aggregation, creatine kinase-MB activity, endothelin 1, systemic inflammation and cardiac lipid peroxidation and increment in aortic eNOS expression. Clopidogrel and prasugrel groups showed enhanced BCL2 expression in cardiac fibers and aortic wall.

SIGNIFICANCE

Prasugrel and clopidogrel protected against A-MI via anti-aggregatory and anti-inflammatory effects. These results add to the value of these drugs in correcting cardiovascular dysfunction in patients vulnerable to A-MI after confirmation by appropriate human studies.

The Integrin Activating Protein Kindlin-3 Is Cleaved in Human Platelets during ST-Elevation Myocardial Infarction

Kindlins are important proteins for integrin signaling and regulation of the cytoskeleton, but we know little about their precise function and regulation in platelets during acute ischemic events. In this work, we investigated kindlin-3 protein levels in platelets isolated from patients with ST-elevation myocardial infarction (STEMI) compared to patients with non-ischemic chest pain. Platelets from twelve patients with STEMI and twelve patients with non-ischemic chest pain were isolated and analyzed for kindlin-3 protein levels and intracellular localization by immunoblotting and two-dimensional gel electrophoresis. Platelet proteome analysis by two-dimensional gel electrophoresis and protein sequencing identified kindlin-3 as a protein that is cleaved in platelets from patients with myocardial infarction. Kindlin-3 full-length protein was significantly decreased in patients with STEMI compared to patients with non-ischemic chest pain (1.0 ± 0.2 versus 0.28 ± 0.2, p < 0.05) by immunoblotting. Kindlin-3 showed a differential distribution and was primarily cleaved in the cytosolic and membrane compartment of platelets in myocardial infarction. Platelet activation with thrombin alone did not affect kindlin-3 protein levels. The present study demonstrates that kindlin-3 protein levels become significantly reduced in platelets of patients with myocardial infarction compared to controls. The results suggest that kindlin-3 cleavage in platelets is associated with the ischemic event of myocardial infarction.

Platelet Glycoprotein IIb/IIIa Receptor Inhibitor Tirofiban in Acute Ischemic Stroke

Tirofiban is a non-peptide selective glycoprotein (GP) IIb/IIIa receptor inhibitor that reversibly inhibits fibrinogen-dependent platelet aggregation and subsequent formation of thrombi, which contribute to the major atherosclerotic complications in the development, progression, and resolution of ischemic stroke. The adjunctive use of tirofiban has been extensively evaluated in progressive stroke, combined intravenous thrombolysis (IVT), and endovascular treatment (EVT) in both preclinical and clinical studies. A body of evidence has been accumulated on the risks and benefits associated with tirofiban in terms of prevention of stroke progression, stent thrombosis, improvement in functional independence, and mortality, especially among high-risk ischemic stroke patients as a further strategy alongside conventional treatment. In general, tirofiban has a favorable tolerability and efficacy profile in the improvement of vascular recanalization and long-term functional outcome, although the optimum dosage, application setting, and precise target patients are not yet well-established. However, its specific inhibition of ongoing platelet aggregation and thrombus formation rather than absolute thrombolysis suggests that tirofiban, one of the most widely used GP IIb/IIIa inhibitors, with high affinity and a short plasma/biologic half-life, may have great potential in the acute treatment of ischemic stroke. Substantial practical progress is likely as our understanding of the mechanism of action and pharmacological actions of tirofiban in atherosclerotic ischemic disease improves. Therefore, we classify and summarize the available findings regarding tirofiban in acute ischemic stroke to stimulate and guide further research and clinical practice.

De-escalation of anti-platelet therapy in patients with acute coronary syndromes undergoing percutaneous coronary intervention: a narrative review

Objective:

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y₁₂ receptor inhibitor is the cornerstone of treatment in patients with acute coronary syndromes (ACS) and in those undergoing percutaneous coronary intervention (PCI). In current clinical situation, availability of different oral P2Y₁₂ inhibitors (clopidogrel, prasugrel, and ticagrelor) has enabled physicians to switch among therapies owing to specific clinical scenarios. Although optimum time, loading dose and interval of transition between P2Y₁₂ inhibitors is still controversial and needs further evidence, switching between oral inhibitors frequently occurs in clinical practice for several reasons.

Data sources:

This review was based on data in articles published in PubMed up to June 2018, with the following keywords “antiplatelet therapy”, “ACS”, “PCI”, “ticagrelor”, and “clopidogrel”.

Study selection:

Original articles and critical reviews on de-escalation strategy in ACS patients after PCI were selected. References of the retrieved articles were also screened to search for potentially relevant papers.

Results:

Safety concerns associated with switching between antiplatelet agents, has prompted the use of clopidogrel for patients with ACS especially after PCI as a de-escalation strategy. Practical considerations for de-escalating therapies in patients with ACS such as reducing dose of P2Y₁₂ inhibitors or shortening duration of DAPT (followed by aspirin or P2Y₁₂ receptor inhibitor monotherapy) as potential options are yet to be standardized and validated.

Conclusions:

Current review will provide an overview of the pharmacology of common P2Y₁₂ inhibitors, definitions of de-escalation and different de-escalating strategies and its outcomes, along with possible direction to be explored in de-escalation.

Platelets Activation in Patients Undergoing PTCA and Their Responsiveness After in vitro Stimulation

We evaluated expression of platelet activation markers in blood samples of 15 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) by flow cytometry. Analysis was performed before the beginning of PTCA, during initial coronary angiography and after the end of PTCA or after a stent placement, respectively. We evaluated platelet-derived microparticles, platelet-leukocyte aggregates, platelet aggregates and a membrane expression of CD62P and CD63 molecules. Responsiveness of platelets to the activationin vitrowith thrombin-receptor activating protein – 6 (TRAP-6) was tested simultaneously. Statistically significant differences between patient samples were found only in the expression of the activation markers CD62P (before PTCA 0.22 %, during 0.39 %, after 0.67 %), CD63 (0.26 %/ 0.45 %/ 0.85 %) and platelet-leukocyte aggregates (13.57 %/ 18.39 %/ 23.63 %).In the same group the expression of all constitutive membrane markers was statistically significantly decreased: in patients undergoing PTCA was the expression of CD9:87.98 % (in comparison with control group 94.98 %), CD31: 87.10 % (92.78 %), CD36: 87.37 % (90.98 %), CD41: 88.09 % (95.62 %), CD42a: 88.54 % (94.98 %), CD42a: 88.31 % (94.13 %).

Rationale and Design of the Effectiveness of LowEr maintenanCe dose of TicagRelor early After myocardial infarction (ELECTRA) pilot study

Aims

The degree and time course of platelet inhibition using ticagrelor can vary during the acute phase and the following stable period after acute myocardial infarction (AMI). The optimal level of platelet inhibition during the various stages of AMI remains an open question. The aim of the current study is to compare the antiplatelet efficacy of two ticagrelor maintenance dose regimens (60 mg b.i.d. vs. 90 mg b.i.d.) in stable patients following an initial strategy with ticagrelor 90 mg b.i.d. during the first month after AMI.

Methods and results

The Effectiveness of LowEr maintenanCe dose of TicagRelor early After myocardial infarction (ELECTRA) pilot study is a phase III, single-centre, randomized, open-label, pharmacokinetic/pharmacodynamic trial. The study population will include 50 patients with AMI treated with percutaneous coronary intervention. At Day 30 post-AMI, all trial participants will be randomly assigned in 1:1 ratio to receive either reduced (60 mg b.i.d.) or standard (90 mg b.i.d.) maintenance ticagrelor dose until Day 45 post-AMI. Platelet function testing in each patient will be performed using up to two different methods (the VASP assay and multiple electrode aggregometry). Pharmacokinetics of ticagrelor and its active metabolite (AR-C124910XX) will be assessed by liquid chromatography mass spectrometry.

Conclusion

A de-escalation strategy with reduced dose of ticagrelor (60 mg b.i.d.) following an initial standard dose (90 mg b.i.d.) during the first month after AMI may provide equally effective platelet inhibition as compared to maintenance with the standard ticagrelor dose.

ClinicalTrials. gov Identifier

NCT03251859.

Effects of ticagrelor versus clopidogrel on platelet function in fibrinolytic-treated STEMI patients undergoing early PCI

OBJECTIVES

Patients undergoing PCI early after fibrinolytic therapy are at high risk for both thrombotic and bleeding complications. We sought to assess the pharmacodynamic effects of ticagrelor versus clopidogrel in the fibrinolytic-treated STEMI patients undergoing early PCI.

METHODS AND RESULTS

Patients undergoing PCI within 24 hours of tenecteplase (TNK), aspirin, and clopidogrel for STEMI were randomized to receive additional clopidogrel 300 mg followed by 75 mg daily or ticagrelor 180 mg followed by 90 mg twice daily. The platelet reactivity units (PRU) were measured with the VerifyNow Assay before study drug administration (baseline) at 4 and 24 hours post-PCI. The primary end point was PRU ≤208 at 4 hours. A total of 140 patients (74 in ticagrelor and 66 in clopidogrel group) were enrolled. The mean PRU values at baseline were similar for the 2 groups (257.8±52.9 vs 259.5±56.7, P=.85, respectively). Post-PCI, patients on ticagrelor, compared to those on clopidogrel, had significantly lower PRU at 4 hours (78.7±88 vs 193.6±86.5, respectively, P<.001) and at 24 hours (34.5±35.0 and 153.5±75.5, respectively, P<.001). The primary end point was observed in 87.8% (n=65) in the ticagrelor-treated patients compared to 57.6% (n=38) of clopidogrel-treated patients, P<.001.

CONCLUSION

Fibrinolysis-treated STEMI patients who received clopidogrel and aspirin at the time of fibrinolysis and were undergoing early PCI frequently had PRU >208. In this high-risk population, ticagrelor provides more prompt and potent platelet inhibition compared with clopidogrel (Funded by Astra Zeneca; NCT01930591, https://clinicaltrials.gov/ct2/show/NCT01930591).

Determination of risk factors affecting the in-hospital prognosis of patients with acute ST segment elevation myocardial infarction after percutaneous coronary intervention

BACKGROUND

To determine the factors affecting the in-hospital prognosis of patients with acute ST segment elevation myocardial infarction (STEMI) after percutaneous coronary intervention (PCI), and to establish its prognostic discriminant model.

METHODS

A total of 701 consecutive STEMI patients undergoing PCI were enrolled in this study. The patients were divided into two groups, good prognosis and poor prognosis, based on whether the patient had adverse outcomes (death or heart function ≥ grade III) at discharge. Demographic and basic clinical characteristics, diagnosis at admission (e.g., ventricular function, complications, or hyperlipidemia), and biomedical indicators (e.g., blood count, basal metabolism and biochemical composition, blood lipid and glucose levels, myocardial biomarkers, and coagulation) were collected and analyzed.

RESULTS

We determined 22 factors as risk factors for the in-hospital prognosis of STEMI patients after PCI: age, cardiac function during hospitalization, complications, history of diabetes mellitus, et al., among which the history of diabetes, uric acid, urea nitrogen, and activated partial thromboplastin time (APTT) were independent risk factors.

CONCLUSION

We identified four independent risk factors for the in-hospital prognosis of STEMI patients after PCI and generated a prognostic model to predict the adverse outcomes of these patients.

Sarpogrelate Based Triple Antiplatelet Therapy Improved Left Ventricular Systolic Function in Acute Myocardial Infarction: Retrospective Study

PURPOSE

The purpose of this study was to assess the potential benefit of a 5-hydroxytryptamine receptor antagonist, sarpogrelate-based triple antiplatelet therapy (TAPT) in comparison with dual antiplatelet therapy (DAPT) in patients undergoing primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI).

MATERIALS AND METHODS

119 patients of STEMI were retrospectively assessed. All patients received aspirin and clopidogrel per standard of care. Among them, 53 patients received an additional loading dose of sarpogrelate and a maintenance dose for 6 months post-PCI (TAPT group), while others did not (DAPT group).

RESULTS

The rates of complete ST-segment resolution at 30 minutes post-PCI and post-procedural thrombolysis in myocardial infarction flow were not significantly different between the two groups (52.8% vs. 48.5%, p=0.200; 92.5% vs. 89.4%, p=0.080). In addition, no significant differences were observed between the two groups with regard to 30-day and 12-month clinical outcomes (cardiac death, myocardial infarction, stent thrombosis, target vessel revascularization, and severe bleeding). Meanwhile, improvement in left ventricular (LV) systolic function was observed in the TAPT group [ΔLV ejection fraction (LVEF)=17.1±9.4%, p<0.001; Δglobal longitudinal strain (GLS)=-9.4±4.2% , p<0.001] at 6 months, whereas it was not in the DAPT group (ΔLVEF= 8.8±6.5%, p=0.090; ΔGLS=-4.6±3.4%, p=0.106). In multivariate analyses, TAPT was an independent predictor for LV functional recovery (odds ratio, 2.61; 95% confidence interval, 1.16-5.87; p=0.003).

CONCLUSION

Sarpogrelate-based TAPT improved LV systolic function at 6 months in STEMI patients undergoing primary PCI.

Platelet Toll-like receptor (TLR) expression and TLR-mediated platelet activation in acute myocardial infarction

Both platelets and Toll-like receptors (TLRs) contribute to acute myocardial infarction (AMI). Platelet activation can occur post-AMI and despite treatment with anti-platelet therapy. TLRs may represent an alternative platelet activation pathway, although the role of platelet-TLRs in AMI is poorly characterized. The aim of this study was to examine platelet-TLR expression and TLR-mediated platelet activation in healthy and AMI subjects. Here, we report that platelets from AMI patients exhibit upregulation of some, but not other, TLRs. When examined by western blotting, platelet-TLR1 and TLR4 were significantly upregulated in AMI subjects compared to healthy subjects (both p<0.05). Platelet-TLR2 was slightly, but non-significantly, upregulated in AMI patients and platelet-TLR6 expression did not change across cohorts. Platelets from both healthy and AMI subjects exhibited distinct activation patterns in response to various TLR agonists (0.1-100μg/mL), as determined by flow cytometry. Healthy and AMI platelets became dose-dependently and directly activated in response to Pam3CSK4, a TLR2/1 agonist, but were directly potently activated only in response to the highest dose (100μg) of lipopolysaccharide (LPS), a TLR4 agonist. Platelet activation in response to both of these agonists was similar across cohorts, despite treatment with anti-platelet therapy in the AMI cohort. At all doses used in this study, platelets were unable to become directly activated by FSL-1, a TLR2/6 agonist. We conclude that the platelet-TLR2/1 activation pathway is functional post-AMI and despite treatment with anti-platelet therapy. The platelet-TLR4 pathway appears to be less likely, and the platelet-TLR2/6 pathways unlikely, to contribute to post-AMI platelet activation.

Aspirate from human stented saphenous vein grafts induces epicardial coronary vasoconstriction and impairs perfusion and left ventricular function in rat bioassay hearts with pharmacologically induced endothelial dysfunction

Stent implantation into aortocoronary saphenous vein grafts (SVG) releases particulate debris and soluble vasoactive mediators, for example, serotonin. We now analyzed effects of the soluble mediators released into the coronary arterial blood during stent implantation on vasomotion of isolated rat epicardial coronary artery segments and on coronary flow and left ventricular developed pressure in isolated perfused rat hearts. Coronary blood was retrieved during percutaneous SVG intervention using a distal occlusion/aspiration protection device in nine symptomatic patients with stable angina pectoris and a flow‐limiting SVG stenosis. The blood was separated into particulate debris and plasma. Responses to coronary plasma were determined in isolated rat epicardial coronary arteries and in isolated, constant pressure‐perfused rat hearts (±nitric oxide synthase [NOS] inhibition and ±serotonin receptor blockade, respectively). Coronary aspirate plasma taken after stent implantation induced a stronger vasoconstriction of rat epicardial coronary arteries (52 ± 8% of maximal potassium chloride induced vasoconstriction [% KCl_max = 100%]) than plasma taken before stent implantation (12 ± 8% of KCl_max); NOS inhibition augmented this vasoconstrictor response (to 110 ± 15% and 24 ± 9% of KCl_max). Coronary aspirate plasma taken after stent implantation reduced in isolated perfused rat hearts only under NOS inhibition coronary flow by 17 ± 3% and left ventricular developed pressure by 25 ± 4%. Blockade of serotonin receptors abrogated these effects. Coronary aspirate plasma taken after stent implantation induces vasoconstriction in isolated rat epicardial coronary arteries and reduces coronary flow and left ventricular developed pressure in isolated perfused rat hearts with pharmacologically induced endothelial dysfunction.

Optimal duration of dual anti-platelet therapy after percutaneous coronary intervention: 2016 consensus position of the Italian Society of Cardiology

Definition of the optimal duration of dual anti-platelet therapy (DAPT) is an important clinical issue, given the large number of patients having percutaneous coronary intervention (PCI), the costs and risks of pharmacologic therapy, the consequences of stent thrombosis, and the potential benefits of DAPT in preventing ischaemic outcomes beyond stent thrombosis. Nowadays, the rationale for a prolonged duration of DAPT should be not only the prevention of stent thrombosis, but also the prevention of ischaemic events unrelated to the coronary stenosis treated with index PCI. A higher predisposition to athero-thrombosis may persist for years after an acute myocardial infarction, and even stable patients with a history of prior myocardial infarction are at high risk for major adverse cardiovascular events. Recently, results of pre-specified post-hoc analyses of randomized clinical trials, including the PEGASUS-TIMI 54 trial, have shed light on strategies of DAPT in various clinical situations, and should impact the next rounds of international guidelines, and also routine practice. Accordingly, the 2015 to 2016 the Board of the Italian Society of Cardiology addressed newer recommendations on duration of DAPT based on most recent scientific information. The document states that physicians should decide duration of DAPT on an individual basis, taking into account ischaemic and bleeding risks of any given patient. Indeed, current controversy surrounding optimal duration of DAPT clearly reflects the fact that, nowadays, a one size fits all strategy cannot be reliably applied to patients treated with PCI. Indeed, patients usually have factors for both increased ischaemic and bleeding risks that must be carefully evaluated to assess the benefit/risk ratio of prolonged DAPT. Personalized management of DAPT must be seen as a dynamic prescription with regular re-evaluations of the risk/benefit to the patient according to changes in his/her clinical profile. Also, in order to derive more benefit than harm from new treatments, a multi-parametric approach using several risk scores of the ischaemic and bleeding risks might improve the process of risk factor characterization. In patients with high ischaemic risk, particularly those with a history of myocardial infarction, the benefits of extended DAPT (particularly with ticagrelor up to 3 years) are likely to outweigh the risks.

Circulating microparticle subpopulations in systemic lupus erythematosus are affected by disease activity

BACKGROUND

Immune cells under chronic inflammation shed microparticles (MPs) that could fuel the inflammatory responses and atherosclerosis typically presented in systemic lupus erythematosus (SLE). This study analyzes total and subset-specific MPs from SLE patients and their possible influence on clinical features, leukocyte activation and serum cytokines.

METHODS

Total MPs and those derived from platelets, endothelial cells, monocytes, granulocytes and T-cells were quantified in plasma of 106 SLE patients and 33 healthy controls by flow cytometry. MP amounts were analyzed according to clinical manifestations, blood leukocyte populations and circulating cytokines (IFNα, TNFα, IL-10, BLyS, IL-17, IL-1β, CXCL10, CCL-2, CCL3, leptin). Finally, the in vitro effect of SLE-isolated MPs on the leukocyte activation status was analyzed.

RESULTS

Total circulating MPs in SLE patients were related to increased disease duration and the presence of cardiovascular disease. Furthermore, patients displayed increased counts of MPs from platelets, monocytes and T-lymphocytes, especially in SLE patients with disease activity or with TNFα^high-profile. Accordingly, MPs were associated with increased expression of activation markers in blood T-cells and monocytes. Finally, analyses propose a role of glucocorticoids in MPs generation and leukocyte activation since both fresh and cultured T-cells under this treatment presented higher IL-10 and CD25 production.

CONCLUSIONS

The altered profile of subset-specific SLE-MPs was influenced by the disease activity and altered status of leukocyte native cells, also associated with a TNFα^high-profile.

TRANSLATIONAL RESULTS

SLE patients, especially those with disease activity, displayed increased counts of MPs derived from platelets, monocytes and T-lymphocytes, which were more frequently found in TNFα^high-type patients. The origin of such SLE-MP subsets seems to be related to the over-activated status of T-cells and monocytes characteristic of these patients. Ex vivo and in vitro analyses propose a role of glucocorticoids in the generation of circulating MPs and leukocyte activation in SLE patients.

Anti-Thrombotic Effects of Statins in Acute Coronary Syndromes: At the Intersection of Thrombosis, Inflammation, and Platelet-Leukocyte Interactions

HMG CoA reductase inhibitors, or statins, are standard of care for preventing cardiovascular disease in at-risk populations. Statins are a well-established therapy proven to reduce long-term cardiovascular mortality and morbidity for prevention of secondary cardiovascular events and have become guideline-recommended therapy following acute myocardial infarction. Emerging data from clinical trials over the last decade indicates that statin therapy may provide broad beneficial effects beyond their primary lipid lowering mechanisms. In coronary heart disease, statins have demonstrated a unique ability to target several cellular pathways, which appear to play an underappreciated role in acute inflammation and subsequent thrombosis. Herein, we review the potential mechanisms where statins may act as antithrombotic agents in the setting of acute coronary syndromes and discuss the clinical implications of these findings.

Microparticles from splenectomized β-thalassemia/HbE patients play roles on procoagulant activities with thrombotic potential

Thromboembolic events including cerebral thrombosis, deep vein thrombosis, and pulmonary embolism are major complications in β-thalassemia. Damaged red blood cells and chronic platelet activation in splenectomized β-thalassemia/HbE patients were associated with increased microparticles (MPs) releases into blood circulation. MPs are small membrane vesicles, which play important roles on coagulation. However, the role of MP in thalassemia is poorly understood. In this study, the effects of splenectomized-MPs on platelet activation and aggregation were investigated. The results showed that isolated MPs from fresh platelet-free plasma of patients and normal subjects directly induce platelet activation, platelet aggregation, and platelet-neutrophil aggregation in a dose-dependent manner. Interestingly, MPs obtained from splenectomized patients are more efficient in induction of platelet activation (P-selectin⁺) when compared to MPs from normal subjects (P < 0.05), tenfold lower than pathophysiological level, at 1:0.1 platelet MP ratio. Co-incubation of splenectomized-MPs with either normal-, non-splenectomized- or splenectomized-platelets at 1:10 platelet MP ratio increased platelet activation up to 5.1 ± 2.2, 5.6 ± 3.7, and 9.5 ± 3.0%, respectively, when normalized with individual baseline. These findings suggest that splenectomized patients were proned to be activated by MPs, and splenectomized-MPs could play an important role on chronic platelet activation and aggregation, leading to thrombus formation in β-thalassemia/HbE patients.

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.

Evaluation of Platelet and Leukocyte Functions in Effort Angina Patients Using High Shear Conditions in Small-Sized Collagen Bead Columns

This study used a small-sized collagen bead column system to investigate platelet functions under high shear stress in 28 patients with effort angina and 15 healthy controls. Soluble P-selectin and soluble L-selectin were also evaluated. Patients underwent stent insertion, followed by treatment with aspirin (100 mg/day) and ticlopidine (200 mg/day). High-shear-dependent platelet function was measured using small-sized collagen beads. The retention rate of platelets from patients with angina was higher than that in healthy controls (10.9% ± 3.9% versus 5.6% ± 1.7%, P < .01). Soluble P-selectin and soluble L-selectin levels of patients with angina significantly increased after passage through the columns. Levels of soluble P-selectin and L-selectin in healthy controls did not exhibit significant changes with passage through the columns. These results suggested that high shear stress caused abnormal activation of leukocytes or adhesive proteins in patients with effort angina, and ticlopidine failed to suppress hyperaggregability of platelets in these patients.

Effects of Physical (In)activity on Platelet Function

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

Long-term dual antiplatelet therapy for secondary prevention of cardiovascular events in the subgroup of patients with previous myocardial infarction: a collaborative meta-analysis of randomized trials

AIMS

Recent trials have examined the effect of prolonged dual antiplatelet therapy (DAPT) in a variety of patient populations, with heterogeneous results regarding benefit and safety, specifically with regard to cardiovascular and non-cardiovascular mortality. We performed a meta-analysis of randomized trials comparing more than a year of DAPT with aspirin alone in high-risk patients with a history of prior myocardial infarction (MI).

METHODS AND RESULTS

A total of 33 435 patients were followed over a mean 31 months among one trial of patients with prior MI (63.3% of total) and five trials with a subgroup of patients that presented with, or had a history of, a prior MI (36.7% of total). Extended DAPT decreased the risk of major adverse cardiovascular events compared with aspirin alone (6.4 vs. 7.5%; risk ratio, RR 0.78, 95% confidence intervals, CI, 0.67-0.90; P = 0.001) and reduced cardiovascular death (2.3 vs. 2.6%; RR 0.85, 95% CI 0.74-0.98; P = 0.03), with no increase in non-cardiovascular death (RR 1.03, 95% CI 0.86-1.23; P = 0.76). The resultant effect on all-cause mortality was an RR of 0.92 (95% CI 0.83-1.03; P = 0.13). Extended DAPT also reduced MI (RR 0.70, 95% CI 0.55-0.88; P = 0.003), stroke (RR 0.81, 95% CI 0.68-0.97; P = 0.02), and stent thrombosis (RR 0.50, 95% CI 0.28-0.89; P = 0.02). There was an increased risk of major bleeding (1.85 vs. 1.09%; RR 1.73, 95% CI 1.19-2.50; P = 0.004) but not fatal bleeding (0.14 vs. 0.17%; RR 0.91, 95% CI 0.53-1.58; P = 0.75).

CONCLUSION

Compared with aspirin alone, DAPT beyond 1 year among stabilized high-risk patients with prior MI decreases ischaemic events, including significant reductions in the individual endpoints of cardiovascular death, recurrent MI, and stroke. Dual antiplatelet therapy beyond 1 year increases major bleeding, but not fatal bleeding or non-cardiovascular death.

Serial clopidogrel dose adjustment after platelet function testing improves outcome of acute coronary syndrome patients undergoing percutaneous coronary intervention with high on-treatment platelet reactivity

High on-treatment platelet reactivity (HTPR) on clopidogrel correlates with adverse outcomes in patients treated with percutaneous coronary intervention (PCI). Whether HTPR is a modifiable risk factor for future events is not clear. We evaluated the effect of serial clopidogrel dose adjustment based on platelet function testing (PFT) during 12 months of dual antiplatelet therapy (DAPT) using Multiplate) analyzer in patients with HTPR after PCI in acute coronary syndrome on clinical outcome. Eighty-seven patients were randomized to interventional (n = 43) and control group (n = 44). Blood samples for PFT were drawn at day 1, 2, 3, 7, 30 and at month 2, 3, 6, 9 and 12. Clopidogrel dose was modified at each point of PFT in the interventional group with patients taking up to two additional 600 mg loading doses and a range of 75-300 mg maintenance dose to achieve and maintain optimal platelet reactivity (19-46 U). The incidence of the primary endpoint (composite of cardiovascular death, non-fatal myocardial infarction, target vessel revascularization and ischemic stroke) was significantly higher in the control group (36.3 vs. 16.2%; p = 0.034). There were no differences in total bleeding events (6.8 vs. 4.6%, p = ns). Patients in the interventional group maintained better P2Y12 inhibition during follow-up. We hypothesize that targeting the therapeutic window of platelet reactivity continuously throughout DAPT by dose adjustment of P2Y12 inhibitor may lead to better platelet reactivity control, and thus reduce the rate of ischemic complications in this high risk group of patients.

Genetics of platelet inhibitor treatment

Dual antiplatelet therapy with aspirin and a P2Y12 receptor antagonist is the standard of care in patients undergoing percutaneous coronary intervention (PCI) and in patients with acute coronary syndromes (ACS) because this regimen has markedly decreased the rate of cardiovascular events. The substantial variability in pharmacodynamic response as well as the moderate antiplatelet efficacy of clopidogrel has raised major concerns, since high on-clopidogrel platelet reactivity has consistently been associated with increased risk for ischaemic events in PCI patients. Baseline demographic and clinical variables contributing to the observed variability have been identified. Besides this, research within the past decade has focused on the impact of genetic polymorphisms encoding transport systems or enzymes involved in the absorption and metabolism of these drugs. Loss-of-function polymorphisms in CYP2C19 are the strongest individual variables affecting pharmacokinetics and antiplatelet response to clopidogrel, but explain no more than 5 to 12% of the variability in adenosine diphosphate-induced platelet aggregation on clopidogrel. No genetic variables contributing to clinical outcomes of patients treated with the newer P2Y12 receptor antagonists, prasugrel or ticagrelor, have been identified so far. This review aims to provide an update on the current status of genotype-based personalized therapy with clopidogrel.

[Clinical pharmacology of current antiplatelet drugs]

Dual antiplatelet therapy with low-dose acetylsalicylic acid (ASA) and an inhibitor of the P2Y12 adenosine diphosphate (ADP) receptor is the standard treatment for patients presenting with acute coronary syndrome (ACS) or undergoing elective coronary interventions according to the current guidelines published by the European Society of Cardiology (ESC). New generation P2Y12 inhibitors, such as prasugrel and ticagrelor exert stronger and more consistent inhibition of the P2Y12 receptor. In clinical studies enrolling patients with ACS these drugs decreased the incidence of ischemic events compared to the standard therapy with clopidogrel and ASA; however, this beneficial effect was associated with an increase in bleeding events. Alternative therapeutic approaches via addition of drugs with different modes of action showed an overall reduction of ischemic events but also failed to uncouple this beneficial effect from an increased bleeding risk.