Platelet Function Testing Research Articles

Short-Term DAPT and DAPT De-Escalation Strategies for Patients With Acute Coronary Syndromes: A Systematic Review and Network Meta-Analysis.

Short-term (≤6 months) dual antiplatelet therapy (DAPT) and DAPT de-escalation become attractive for patients with acute coronary syndrome. A systemic search identified randomized controlled trials that included patients with acute coronary syndrome treated using (1) standard DAPT (12 months) with clopidogrel, prasugrel (standard/low dose), or ticagrelor; (2) extended DAPT (≥18 months); (3) short-term DAPT (≤6 months) followed by P2Y12 inhibitor or aspirin; (4) 12-month DAPT with unguided de-escalation from potent P2Y12 inhibitors to low-dose potent P2Y12 inhibitor or clopidogrel at 1 month; and (5) guided selection DAPT with genotype or platelet function tests. The primary efficacy outcome (major adverse cardiovascular events) was a composite of cardiovascular death, myocardial infarction, or stroke. The primary safety outcome was major or minor bleeding. This meta-analysis included 32 randomized controlled trials with 103 497 patients. While there were no differences in efficacy between short, unguided de-escalation and guided selection strategies, unguided de-escalation was associated with reduced risk of major adverse cardiovascular events compared with standard DAPT with clopidogrel or ticagrelor (hazard ratio [95% CI], 0.67 [0.49-0.93] and 0.68 [0.50-0.93]). Both short DAPT followed by P2Y12 inhibitor and unguided de-escalation were associated with reduced risks in safety compared with other strategies, including guided selection (hazard ratio [95% CI], 0.66 [0.47-0.93] and 0.48 [0.33-0.71]). Short DAPT followed by a P2Y12 inhibitor was associated with reduced risk of major bleeding and all-cause death compared with standard, extended DAPT (eg, versus DAPT with clopidogrel; hazard ratio [95% CI], 0.64 [0.42-0.97] and 0.60 [0.44-0.82]). By rankogram, unguided de-escalation strategy was the safest and most effective strategy in reducing major adverse cardiovascular events and major or minor bleeding while short DAPT followed by P2Y12 inhibitor was ranked the best for major bleeding and all-cause death. In patients with acute coronary syndrome, unguided de-escalation was associated with the lowest risk of major adverse cardiovascular events and major or minor bleeding outcomes, while short DAPT followed by P2Y12 inhibitor was associated with the lowest risk of major bleeding and all-cause death.

The impact of smoking status on clopidogrel responsiveness in patients with coronary artery disease who undergo percutaneous coronary intervention

Background: Previous studies have pointed out the disproportionate action of clopidogrel in inhibiting platelet aggregation due to smoking more than ten cigarettes per a day. This study was designed to examine whether smoking enhances clopidogrel responsiveness in patients who are clinically diagnosed with coronary artery disease (CAD), following percutaneous coronary intervention (PCI). Methods: A total of 324 IHD participants were enrolled in a case-control study. Platelet function test was performed to all participants two hours before PCI procedure to measure clopidogrel response. Participants were then categorized into a non-responder group (case group n = 111) and responder group (control group n = 213). Each group was subdivided into a smoker group and a non-smoker group. All participants received clopidogrel loading dose equivalent to 600 mg and scheduled for elective PCI. Participants’ age, gender, family history of chronic illnesses was recorded in this study. Results: Smoking participants displayed a significant higher level of hemoglobin as compared to the non-smoking participants among the responder and the non-responder study groups (14.6±0.55 vs. 13.12±0.38, P < 0.029; 14.3±0.31 versus 12.96±0.39, P < 0.033) but lower AUC level (17±9 vs. 45±6, P < 0.005; 62±3 vs. 95±7, P < 0.008). Additionally, smoking intensity enhanced clopidogrel responsiveness by odd’s ratio 0.4213 at 95% C.I. (0.259 - 0.684), P < 0.0002. Conclusions: Current smokers had a good response to clopidogrel therapy which exerted a beneficial effect when undergoing PCI as compared to non-smokers. The marked difference in AUC between smokers and non-smokers could be related to the variance in hemoglobin level. The smokers’ paradox needs further justification to confirm this concept.

Use of Tirofiban to Prevent Ischemic Events in Patients with CYP2C19 Loss-of-Function Alleles during Flow Diversion of Intracranial Aneurysm: A Multicenter Cohort Study.

To analyze the effect of tirofiban on ischemic events in CYP2C19 loss-of-function (LOF) allele carriers during pipeline embolization device (PED) implantation. Demographic information, imaging data, ischemic complications, CYP2C19 genotyping, and platelet function test results were collected from patients with PED-treated intracranial aneurysms at three centers. Multivariate logistic regression was used to analyze risk factors for ischemic events. Patients were grouped according to LOF alleles and antiplatelet drugs, the baseline information of LOF allele carriers and non-carriers were compared, and the efficacy of tirofiban was analyzed by comparing the incidence of ischemic events in each group. In total, 278 patients were included in the study, 24 of whom had an ischemic event. 157 (56.5%) patients carried the LOF allele and were more likely to develop resistance to clopidogrel (P < 0.001) and hypertension (P = 0.010). Multivariate logistic regression analysis revealed that the independent risk factors for ischemic events were age of > 55years (OR = 3.308, P = 0.028), LOF alleles (OR = 3.960, P = 0.036), and clopidogrel nonresponsiveness (OR = 3.301, P = 0.014). For LOF allele carriers, prophylactic use of tirofiban after PED implantation helped to reduce ischemic events (4.3% vs. 16.4%, P = 0.039). This study supports CYP2C19 genotyping before flow diversion because LOF alleles increase the risk of ischemic events. Prophylactic use of tirofiban may help reduce ischemic events in LOF allele carriers.

Consensus report on flow cytometry for platelet function testing in thrombocytopenic patients: communication from the SSC of the ISTH

BackgroundPlatelet count alone does not reliably predict bleeding risk, suggesting platelet function is important to monitor in patients with thrombocytopenia. There is still an unmet need for improved platelet function diagnostics in patients with low platelet count in many clinical situations. Flow cytometry is a promising tool allowing reliable platelet function study in this setting. ObjectivesThe goal of this joint project between the International Society on Thrombosis and Haemostasis (ISTH) Scientific Standardization Committee (SSC) Subcommittees on Platelet Physiology and Platelet Immunology is to provide expert consensus guidance on the use of flow cytometry for the evaluation of platelet function, particularly activation, in patients with low platelet counts. MethodsA literature review was performed to identify relevant questions and areas of interest. An electronic expression of interest form was thereafter announced on the ISTH webpage, followed by a survey encompassing 37 issues regarding preanalytical, analytical, postanalytical, and performance aspects. Areas of disagreement or uncertainty were identified and formed the basis for 2 focus group discussions. ResultsConsensus recommendations relative to patient sample collection, preanalytical variables, sample type, platelet-count cutoff, any potential specific modification of the standard flow cytometry protocol, and results expression and reporting are proposed based on the current practices of experts in the field as well as on literature review. ConclusionThe proposed consensus recommendations would allow standardization of protocols in upcoming clinical studies. The clinical utility of platelet function testing using flow cytometry to predict bleeding risk still needs rigorous multicenter outcome studies in patients with thrombocytopenia.

De-escalation or abbreviation of dual antiplatelet therapy in acute coronary syndromes and percutaneous coronary intervention: a Consensus Statement from an international expert panel on coronary thrombosis.

Conventional dual antiplatelet therapy (DAPT) for patients with acute coronary syndromes undergoing percutaneous coronary intervention comprises aspirin with a potent P2Y purinoceptor 12 (P2Y12) inhibitor (prasugrel or ticagrelor) for 12 months. Although this approach reduces ischaemic risk, patients are exposed to a substantial risk of bleeding. Strategies to reduce bleeding include de-escalation of DAPT intensity (downgrading from potent P2Y12 inhibitor at conventional doses to either clopidogrel or reduced-dose prasugrel) or abbreviation of DAPT duration. Either strategy requires assessment of the ischaemic and bleeding risks of each individual. De-escalation of DAPT intensity can reduce bleeding without increasing ischaemic events and can be guided by platelet function testing or genotyping. Abbreviation of DAPT duration after 1-6 months, followed by monotherapy with aspirin or a P2Y12 inhibitor, reduces bleeding without an increase in ischaemic events in patients at high bleeding risk, particularly those without high ischaemic risk. However, these two strategies have not yet been compared in a head-to-head clinical trial. In this Consensus Statement, we summarize the evidence base for these treatment approaches, provide guidance on the assessment of ischaemic and bleeding risks, and provide consensus statements from an international panel of experts to help clinicians to optimize these DAPT approaches for individual patients to improve outcomes.

Platelet genetic testing by next-generation sequencing: A practical update.

Inherited platelet disorders (IPDs) are a heterogeneous group of disorders characterized by normal or reduced platelet counts, bleeding diatheses of varying severities, and the presence (syndromic) or absence (non-syndromic) of involvement of other organs. Due to the lack of highly specific platelet function tests and overlapping clinical and laboratory features, diagnosing the underlying cause of IPDs remains challenging. In recent years, genetic testing via next-generation sequencing (NGS) technologies to rapidly analyze multiple genes has gradually emerged as an important part of the laboratory investigation of patients with IPDs. A systemic clinical and laboratory testing approach and thorough phenotype and genotype correlation studies of both patients and their family members are crucial for accurate diagnoses of IPDs.

Strategy of dual antiplatelet therapy for patients with ST-elevation myocardial infarction and non-ST-elevation acute coronary syndromes: A systematic review and network meta-analysis

BackgroundVarious durations and de-escalation strategies of dual antiplatelet therapy (DAPT) after ST-elevation myocardial infarction (STEMI) or non-ST-elevation acute coronary syndromes (NSTE-ACS) have been tested in randomized controlled trials (RCT)s. However, evidence by specific ACS subtype is unknown. MethodsPubMed, EMBASE, and Cochrane CENTRAL were searched in February 2023. RCTs on DAPT strategies included STEMI or NSTE-ACS patients with standard DAPT (12 months) with clopidogrel or potent P2Y12 inhibitors, short-term DAPT (≤6 months) followed by potent P2Y12 inhibitors or aspirin, unguided de-escalation from potent P2Y12 inhibitors to low-dose potent P2Y12 inhibitors or clopidogrel at one month, and guided selection with genotype or platelet function tests were identified. The primary outcome was the net adverse clinical events (NACE) defined as a composite of major adverse cardiovascular events (MACE) and clinically relevant bleeding events. ResultsTwenty RCTs with a combined total population of 24,745 STEMI and 37,891 NSTE-ACS patients were included. In STEMI patients, unguided de-escalation strategy was associated with a lower rate of NACE compared with standard DAPT using potent P2Y12 inhibitors (HR:0.57; 95% CI:0.34–0.96) without increased risk of MACE. In NSTE-ACS patients, unguided de-escalation strategy was associated with a lower rate of NACE compared with the guided selection strategy (HR:0.65; 95% CI:0.47–0.90), standard DAPT using potent P2Y12 inhibitors (HR:0.62; 95% CI:0.50–0.78) and standard DAPT using clopidogrel (HR:0.73; 95% CI:0.55–0.98) without increased risk of MACE. ConclusionUnguided de-escalation strategy was associated with a reduced risk of NACE and may be the most effective DAPT strategy for STEMI and NSTE-ACS.

Effect of Platelet Function Testing Guidance on Clinical Outcomes for Patients with Intracranial Aneurysms Undergoing Endovascular Treatment.

Platelet function testing has been proposed to better adjust individualized antiplatelet treatment for patients undergoing endovascular treatment for intracranial aneurysms. Its clinical significance needs to be comprehensively evaluated. Our aim was to evaluate the impact of platelet function testing-guided versus standard antiplatelet treatment in patients receiving endovascular treatment for intracranial aneurysms. PubMed, EMBASE, and the Cochrane Library of clinical trials were searched from inception until March 2023. Eleven studies comprising 6199 patients were included. ORs with 95% CIs were calculated using random effects models. The platelet function testing-guided group was associated with a decreased rate of symptomatic thromboembolic events (OR = 0.57; 95% CI, 0.42-0.76; I2 = 26%). No significant difference was found in asymptomatic thromboembolic events (OR = 1.07; 95% CI, 0.39-2.94; I2 = 48%), hemorrhagic events (OR = 0.71; 95% CI, 0.42-1.19; I2 = 34%), intracranial hemorrhagic events (OR = 0.61; 95% CI, 0.03-10.79; I2 = 62%), morbidity (OR = 0.53; 95% CI, 0.05-5.72; I2 = 86%), and mortality (OR = 1.96; 95% CI, 0.64-5.97; I2 = 0%) between the 2 groups. Subgroup analysis suggested that platelet function testing-guided therapy may contribute to fewer symptomatic thromboembolic events in patients who received stent-assisted coiling (OR = 0.43; 95% CI, 0.18-1.02; I2 = 43%) or a combination of stent-assisted and flow-diverter stent placement (OR = 0.61; 95% CI, 0.36-1.02; I2 = 0%) or who changed from clopidogrel to other thienopyridines (OR = 0.64; 95% CI, 0.40-1.02; I2 = 18%), though the difference did not reach statistical significance. Heterogeneous endovascular treatment methods and adjusted antiplatelet regimens were limitations. Platelet function testing-guided antiplatelet strategy significantly reduced the incidence of symptomatic thromboembolic events without any increase in the hemorrhagic events for patients undergoing endovascular treatment for intracranial aneurysms.

High-Dose Vitamin C Alleviates Pancreatic Necrosis by Inhibiting Platelet Activation Through the CXCL12/CXCR4 Pathway in Severe Acute Pancreatitis.

Platelet activation in the early stage of pancreatitis is the key step developing into pancreatic necrosis. Studies suggested that vitamin C (Vit C) can inhibit platelet activity by targeting CXCL12/CXCR4 pathway. High-dose Vit C were showed to reduce pancreatic necrosis in severe acute pancreatitis (SAP) but the mechanism remains unclear. Here we speculate high-dose Vit C reduce pancreatic necrosis by inhibiting platelet activation through downregulating CXCL12/CXCR4 pathway. The pancreatic microcirculation of rats was observed by intravital microscopy. The platelet activity of SAP rats treated with or without high-dose Vit C was analyzed by platelet function test. Besides, the activity of platelets preincubated with high-dose Vit C or vehicle from SAP patients was also evaluated. Then, the TFA (CXCR4 agonist) and rCXCL12 were used to neutralize the effect of high-dose Vit C in SAP rats treated with high-dose Vit C. Meanwhile, the levels of enzymes and inflammatory cytokines in rat plasma, and rats' pancreatic histopathology and mortality were assessed. Platelets from animals and patients with SAP are more sensitive to agonists and are more easily activated. Administration of high-dose Vit C significantly ameliorated excessive activation of platelets in SAP rats, ultimately increasing the microvessel density and inducing microthrombus and blood stasis; these results were consistent with clinical sample analysis. Moreover, high-dose Vit C significantly inhibited the release of amylase, lipase, TNF-α, and IL-6 in SAP rat plasma, reducing pancreatic damage and the mortality of SAP rats. However, using TFA and rCXCL12 significantly reversed the effect of high-dose Vit C on excessive activation of platelets, aggravating microcirculation impairment and pancreatic damage. The present study suggests that high-dose Vit C can ameliorate pancreatic necrosis by improving microcirculation disorders of SAP. For the first time, the underlying mechanism is related with inhibiting platelet activation through the CXCL12/CXCR4 pathway.

Extended sample storage for platelet function testing in healthy dogs.

Platelet function testing is important for monitoring the effects of antiplatelet therapy but is not readily used due to time constraints for testing and the need for specialized equipment. This study evaluated the effects of various storage methods on selected platelet function tests to determine if delayed platelet function testing is feasible in canine blood samples. Our hypotheses were that platelet function would not decline during storage and, thus, no differences in test results would be found over time. Thirteen healthy dogs were studied. Citrated blood samples were tested with a Platelet Function Analyzer-200 (PFA), which mimics high-shear conditions, using P2Y and CADP cartridges, after being held at room temperature for 2 h and refrigerated for 24 and 48 h. Plateletworks (PW), which measures aggregation based on platelet counting, was performed on an optical hematology analyzer using 10-min-old native samples, citrated samples held at room temperature for 3-4 h and refrigerated for 24 and 48 h, and samples stored in the preservative solution, AGGFix, up to 7 days. PFA closure times increased with storage, especially with the P2Y cartridge. Median aggregation with fresh PW was 94%, and this was maintained at all time points (range of median values 88%-94%). Most samples showed decreased, yet still robust (>70%), aggregation with longer storage. Spontaneous aggregation in citrate was noted in most dogs. AGGFix stabilized platelet aggregates to allow for delayed testing. Delayed platelet function testing is feasible, but ranges of expected values may differ from tests using fresh samples.

Platelet factor XIII-A regulates platelet function and promotes clot retraction and stability

BackgroundFactor XIII (FXIII) is an important proenzyme in the hemostatic system. The plasma-derived enzyme activated FXIII cross-links fibrin fibers within thrombi to increase their mechanical strength and cross-links fibrin to fibrinolytic inhibitors, specifically α2-antiplasmin, to increase resistance to fibrinolysis. We have previously shown that cellular FXIII (factor XIII-A [FXIII-A]), which is abundant in the platelet cytoplasm, is externalized onto the activated membrane and cross-links extracellular substrates. The contribution of cellular FXIII-A to platelet activation and platelet function has not been extensively studied. ObjectivesThis study aims to identify the role of platelet FXIII-A in platelet function. MethodsWe used normal healthy platelets with a cell permeable FXIII inhibitor and platelets from FXIII-deficient patients as a FXIII-free platelet model in a range of platelet function and clotting tests. ResultsOur data demonstrate that platelet FXIII-A enhances fibrinogen binding to the platelet surface upon agonist stimulation and improves the binding of platelets to fibrinogen and aggregation under flow in a whole-blood thrombus formation assay. In the absence of FXIII-A, platelets show reduced sensitivity to agonist stimulation, including decreased P-selectin exposure and fibrinogen binding. We show that FXIII-A is involved in platelet spreading where a lack of FXIII-A reduces the ability of platelets to fully spread on fibrinogen and collagen. Our data demonstrate that platelet FXIII-A is important for clot retraction where clots formed in its absence retracted to a lesser extent. ConclusionOverall, this study shows that platelet FXIII-A functions during thrombus formation by aiding platelet activation and thrombus retraction in addition to its antifibrinolytic roles.

Prospective assessment of platelet function in patients undergoing elective resection of glioblastoma multiforme

This prospective study was aimed to test changes in hemostasis in patients with GBM, occurring at baseline (before surgery, time 0, T0) and 2 (T2), 24 (T24), and 48-hour (T48) after surgery. We enrolled consecutive patients subjected to GBM resection (GBR group; N = 60), laparoscopic colon cancer resection (comparative CCR group; N = 40), and healthy blood donors (HBD group; N = 40). We performed 1. conventional coagulation tests 2. ROTEM (rotational thromboelastometry) parameters and 3. platelet function tests, including PFA-200 closure time when stimulated by collagen/epinephrine (COL-EPI) and ROTEM platelet, using three different activators (arachnoid acid in ARATEM, adenosine diphosphate in ADPTEM, and thrombin receptor-activating peptide-6 in TRAPTEM). Variables associated with unfavorable 1-year clinical outcome were investigated, too. We observed in GBR patients that platelet aggregometry, as assessed by ROTEM platelet parameters, was significantly impaired along with a shortened closure time. These changes were evident from T0 to T48. A decreased area under the aggregation curve in TRAPTEM was associated with improved survival (adjusted odd ratio (95% CI), 1.03 (1.01–1.06)). This study suggests that patients with GBM presented a decreased platelet aggregation from before surgery and thorough the postoperative period. Decreased platelet aggregation improved clinical outcome.

Individualized or Uniform De-Escalation Strategies for Antiplatelet Therapy in Acute Coronary Syndrome: A Review of Clinical Trials with Platelet Function Testing and Genetic Testing-Based Protocols.

This comprehensive literature review assessed the effectiveness of precision medicine approaches in individualizing P2Y12 de-escalation strategies, such as platelet function testing guidance, genetic testing guidance, and uniform de-escalation, for acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). Analyzing six trials with a total of 13,729 patients, the cumulative analyses demonstrated a significant reduction in major adverse cardiac events (MACE), net adverse clinical events (NACE), and major and minor bleeding events with P2Y12 de-escalation. Specifically, the analysis found a 24% reduction of MACE and a 22% reduction of adverse event risk (relative risk (RR) 0.76, 95% confidence interval (CI): 0.71-0.82, and RR: 0.78, 95% CI 0.67-0.92, respectively). Reductions in bleeding events were highest with uniform unguided de-escalation, followed by guided de-escalations, while ischemic event rates were similarly lower across all three strategies. Although the review highlights the potential of individualized P2Y12 de-escalation strategies to offer a safer alternative to the long-term potent P2Y12 inhibitor-based dual antiplatelet therapy, it also indicates that laboratory-guided precision medicine approaches may not yet offer the expected benefits, necessitating further research to optimize individualized strategies and evaluate the potential of precision medicine approaches in this context.

P212 EFFICACY AND SAFETY OF GENOTYPE–GUIDED AND PLATELET FUNCTION TEST–GUIDED ANTI–P2Y12 THERAPY IN PATIENTS UNDERGOING PCI: A META–ANALYSIS OF RCTS

Abstract Clopidogrel is the most commonly used anti–P2Y12 drug in DAPT. Impaired pharmacological response and antithrombotic efficacy associated with cytochrome–P450 and/or ABCB1 gene mutations is observed in about 1/3 of treated patients. To circumvent this problem, guided therapy has been tested, based on either identification of predisposing gene mutations or results of platelet function tests (PFTs). Patients with with predisposing gene mutations or high platelet reactivity on clopidogrel (HPR) were treated with alternative, potentially more effective regimens: higher clopidogrel doses, prasugrel, ticagrelor, or additional cylostazol. In this meta–analysis, we tested the efficacy and safety of these two different strategies of guided therapy separately. We searched relevant articles published in English until October 1th 2022 on MEDLINE, Embase and Central. Articles included all RCTs comparing standard anti–P2Y12 therapy (ST) versus genotype–guided or PFTs–guided anti–P2Y12 therapy in patients with acute coronary syndromes (ACS) or chronic coronary artery disease (CCAD) undergoing PCI. Two reviewers independently assessed study eligibility and risk of bias, and extracted data. Hazard ratios with 95% CI were calculated based on fixed effects models. Efficacy outcomes comprised major adverse cardiovascular events (MACE) as defined in each study. Main safety outcome included major bleedings (MB) according to BARC. Different sub–analyses were also performed based on type of anti–P2Y12 drug in ST, type of alternative drug, type of PFT, patients’ ethnicity, prevalence of ACS. We retrieved 6 RCTs testing genotype–guided anti–P2Y12 therapy on 10443 patients and 14 RCTs testing PFTs–guided anti–P2Y12 therapy on 11596 patients. MACE were lower in genotype–guided therapy than in ST, RR 0.68 (95% CI, 0.49–0.94) while MB did not significantly differ between the two groups, RR 0.88 (95% CI, 0.63–1.23). MACE and MB did not significantly differ between PFTs–guided anti–P2Y12 therapy and ST: RR 0.83 (95% CI, 0.58–1.18) and 1.24 (95% CI, 1.00–1.53), respectively. Sub–analyses revealed that MACE were lower in PFTs–guided anti–P2Y12 therapy compared to ST in patients of Asian descent. In conclusion, gentotype–guided anti–P2Y12 therapy reduced the incidence of MACE without increasing MB, compared with ST, in patients with ACS or CCAD undergoing PCI; in contrast, PFTs–guided anti–P2Y12 therapy did not affect the incidence of MACE or MB in these patients.

Age and outcomes following personalized antiplatelet therapy in chronic coronary syndrome patients: a post hoc analysis of the randomized PATH-PCI trial

It is particularly important to establish more effective and safer antiplatelet treatment strategies according to age. The present subanalysis of the PATH-PCI trial was to determine the safety and efficacy of any dual-antiplatelet therapy (DAPT) strategy in different age groups. We randomized 2285 chronic coronary syndrome (CCS) patients undergoing percutaneous coronary intervention (PCI) into a standard group or a personalized group from December 2016 to February 2018. The personalized group received personalized antiplatelet therapy (PAT) based on a novel platelet function test (PFT). The standard group received standard antiplatelet therapy (SAT). Then, all patients were divided according to age (under the age of 65 years and aged 65 years or over) to investigate the association and interaction of age on clinical outcomes at 180 days. In the patients under the age of 65 years, the incidence of NACEs was decreased in the personalized group compared to the standard group (5.1% vs. 8.8%, HR: 0.603, 95% CI: 0.409–0.888, P = .010). The rates of MACCEs (3.3% vs. 7.7%, HR: 0.450, 95% CI: 0.285–0.712, P = .001), MACEs (2.2% vs. 5.4%, HR: 0.423, 95% CI: 0.243–0.738, P = .002) also decreased. We did not find a significant difference in bleeding between the groups. In the patients aged 65 years or over, no difference in the primary endpoint was found (4.9% vs. 4.2%, P = .702), and comparable rates of survival were observed with the two strategies (all Ps > 0.05). The present study shows that PAT according to PFT was comparable to SAT at the 180-day follow-up for both ischemic and bleeding endpoints in CCS patients aged 65 years or over who underwent PCI. In patients under the age of 65 years, PAT can reduce ischemic events but does not increase bleeding, and it is an effective and safe treatment strategy. It may be necessary for young CCS patients after PCI to undergo PAT early after PCI.

Single antiplatelet therapy directly after percutaneous coronary intervention in non-ST-segment elevation acute coronary syndrome patients: the OPTICA study.

Early P2Y12 inhibitor monotherapy has emerged as a promising alternative to 12 months of dual antiplatelet therapy following percutaneous coronary intervention (PCI). In this single-arm pilot study, we evaluated the feasibility and safety of ticagrelor or prasugrel monotherapy directly following PCI in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). Patients received a loading dose of ticagrelor or prasugrel before undergoing platelet function testing and subsequent PCI using new-generation drug-eluting stents. The stent result was adjudicated with optical coherence tomography in the first 35 patients. Ticagrelor or prasugrel monotherapy was continued for 12 months. The primary ischaemic endpoint was the composite of all-cause mortality, myocardial infarction, definite or probable stent thrombosis or stroke within 6 months. The primary bleeding endpoint was Bleeding Academic Research Consortium type 2, 3 or 5 bleeding within 6 months. From March 2021 to March 2022, 125 patients were enrolled, of whom 75 ultimately met all in- and exclusion criteria (mean age 64.5 years, 29.3% women). Overall, 70 out of 75 (93.3%) patients were treated with ticagrelor or prasugrel monotherapy directly following PCI. The primary ischaemic endpoint occurred in 3 (4.0%) patients within 6 months. No cases of stent thrombosis or spontaneous myocardial infarction occurred. The primary bleeding endpoint occurred in 7 (9.3%) patients within 6 months. This study provides first-in-human evidence that P2Y12 inhibitor monotherapy directly following PCI for NSTE-ACS is feasible, without any overt safety concerns, and highlights the need for randomised controlled trials comparing direct P2Y12 inhibitor monotherapy with the current standard of care.

The rate of platelet activation determines thrombus size and structure at arterial shear

BackgroundThe response of platelets to activating stimuli and pharmaceutical agents varies greatly within the normal population. Current platelet function tests are used to measure end-point levels of platelet activation without taking the speed at which platelets activate into account, potentially missing vital metrics to characterize platelet reactivity. ObjectivesTo identify variability, to agonists and among individuals, in platelet activation kinetics and assess the impact of this on thrombus formation. MethodsWe have developed a bespoke real-time flow cytometry assay and analysis package to measure the rate of platelet activation over time using 2 parameters of platelet activation, fibrinogen binding and P-selectin exposure. ResultsThe rate of platelet activation varied considerably within the normal population but did not correlate with maximal platelet activation, demonstrating that platelet activation rate is a separate and novel metric to describe platelet reactivity. The relative rate of platelet response between agonists was strongly correlated, suggesting that a central control mechanism regulates the rate of platelet response to all agonists. ConclusionFor the first time, we have shown that platelet response rate corresponds to thrombus size and structure, wherein faster responders form larger, more densely packed thrombi at arterial, but crucially not venous, shear. We have demonstrated that the rate of platelet activation is an important metric in stratifying individual platelet responses and will provide a novel focus for the design and development of antiplatelet therapy, targeting high-shear thrombosis without exacerbating bleeding at low shear.

The impact of smoking status on clopidogrel responsiveness in patients with coronary artery disease who undergo percutaneous coronary intervention

Background: Previous studies have pointed out the disproportionate action of clopidogrel in inhibiting platelet aggregation due to smoking more than ten cigarettes per a day. This study was designed to examine whether smoking enhances clopidogrel responsiveness in patients who are clinically diagnosed with coronary artery disease (CAD), following percutaneous coronary intervention (PCI). Methods: A total of 324 IHD participants were enrolled in a case-control study. Platelet function test was performed to all participants two hours before PCI procedure to measure clopidogrel response. Participants were then categorized into a non-responder group (case group n = 111) and responder group (control group n = 213). Each group was subdivided into a smoker group and a non-smoker group. All participants received clopidogrel loading dose equivalent to 600 mg and scheduled for elective PCI. Participants’ age, gender, family history of chronic illnesses was recorded in this study. Results: Smoking participants displayed a significant higher level of hemoglobin as compared to the non-smoking participants among the responder and the non-responder study groups (14.6±0.55 vs. 13.12±0.38, P &lt; 0.029; 14.3±0.31 versus 12.96±0.39, P &lt; 0.033) but lower AUC level (17±9 vs. 45±6, P &lt; 0.005; 62±3 vs. 95±7, P &lt; 0.008). Additionally, smoking intensity enhanced clopidogrel responsiveness by odd’s ratio 0.4213 at 95% C.I. (0.259 - 0.684), P &lt; 0.0002. Conclusions: Current smokers had a good response to clopidogrel therapy which exerted a beneficial effect when undergoing PCI as compared to non-smokers. The marked difference in AUC between smokers and non-smokers could be related to the variance in hemoglobin level. The smokers’ paradox needs further justification to confirm this concept.

Nanotopography of Polystyrene/Poly(methyl methacrylate) for the Promotion of Patient Specific Von Willebrand Factor Entrapment and Platelet Adhesion in a Whole Blood Microfluidic Assay.

Platelet function testing is essential for the diagnosis of patients with bleeding disorders. Specifically, there is a need for a whole blood assay that is capable of analysing platelet behaviour in contact with a patient-specific autologous von Willebrand factor (vWF), under physiologically relevant conditions. The creation of surface topography capable of entrapping and uncoiling vWF for the support of subsequent platelet adhesion within the same blood sample offers a potential basis for such an assay. In this study, spin coating of polystyrene/poly (methyl methacrylate) (PS/PMMA) demixed solutions onto glass substrates in air has been used to attain surfaces with well-defined topographical features. The effect of augmenting the PS/PMMA solution with uniform 50 µm PS microspheres that can moderate the demixing process on the resultant surface features has also been investigated. The topographical features created here by spin coating under ambient air pressure conditions, rather than in nitrogen, which previous work reports, produces substrate surfaces with the ability to entrap vWF from flowing blood and facilitate platelet adhesion. The direct optical visualisation of fluorescently-labelled platelets indicates that topography resulting from inclusion of PS microspheres in the PS/PMMA spin coating solution increases the total number of platelets that adhere to the substrate surface over the period of the microfluidic assay. However, a detailed analysis of the adhesion rate, mean translocating velocity, mean translocation distance, and fraction of the stably adhered platelets measured during blood flow under arterial equivalent mechanical shear conditions indicates no significant difference for topographies created with or without inclusion of the PS microspheres.

Platelet function in neonates and children

Platelets are major regulators of haemostasis and coagulation. The primary role of platelets in coagulation is to form a stable clot and stop bleeding. Studies of platelet phenotype and function in neonates and children have been restricted by the large volumes required for many common platelet function tests such as platelet aggregometry. Developmental changes in platelets have not been as well described as developmental changes in plasma coagulation proteins, and overall, platelet phenotype and function in neonates and children has been understudied when compared to adults. Recent developments in more sensitive platelet function testing methods requiring smaller blood volumes such as flow cytometry has enabled recent studies to further investigate platelet phenotype and function in neonates and children. In this review we will provide an overview of recent advances from the past five years in platelets in the context of developmental haemostasis, as well as the role of platelets in neonatal paediatric disease.