Differences In Platelet Aggregation Research Articles

Platelet activity, coagulation, and fibrinolysis in long-term users of anabolic-androgenic steroids compared to strength-trained athletes

IntroductionUse of anabolic-androgenic steroids (AAS) is associated with adverse cardiovascular (CV) effects, including potential prothrombotic effects. This study aimed to assess platelet activation and aggregation, coagulation, and fibrinolysis, in long-term AAS users compared to non-using strength-trained athletes. Materials and methodsThirty-seven strength-trained men using AAS were compared to seventeen non-using professional strength-trained athletes at similar age (median 33 years). AAS use was verified by blood and urine analyses. Platelet Function Analyzer 100 (PFA-100) and whole blood impedance aggregometry with thrombin, arachidonic acid, and ADP as agonists, were performed to evaluate platelet aggregation. ELISA methods were used for markers of platelet activation. Fibrinogen, D-dimer, the coagulation inhibitors protein S and C activity, and antithrombin were measured by routine. Fibrinolysis was evaluated by Plasminogen Activator Inhibitor-1 (PAI-1) activity. ResultsThere were no significant differences in platelet aggregation between the two groups. Von Willebrand factor was lower among the AAS users (p < 0.01), and P-Selectin was slightly higher (p = 0.05), whereas CD40 Ligand, β-thromboglobulin, and thrombospondin did not differ significantly. No differences were found in the assessed coagulation inhibitors. Higher D-dimer levels (p < 0.01) and lower PAI-1 activity (p < 0.01) were found among the AAS users. ConclusionsThe investigated long-term users of AAS did not exhibit elevated platelet activity compared to strength-trained non-using athletes. However, AAS use was associated with higher D-dimer levels and lower PAI-1 activity. These findings suggest that any prothrombotic effect of long-term AAS use may predominantly involve other aspects of the hemostatic system than blood platelets.

Using an agonist panel and aggregation to assess antiplatelet therapy in mice

Abstract Platelets play a crucial role in hemostasis. For cardiovascular and stroke prophylaxis, patients are commonly placed on either single or dual antiplatelet drugs, such as aspirin and/or clopidogrel. Here we outline a mouse model examining antiplatelet therapy and the resulting changes in platelet activation and aggregation. Using commercially available transgenic mice with platelets expressing green fluorescent protein (GFP) or red fluorescent protein (RFP), endogenous platelets were inhibited with a single, dual, or control antiplatelet treatment. We used 100µg aspirin/g mouse or 50µg clopidogrel/g mouse for a single dose; dual antiplatelet therapy was a combined dose of 100µg aspirin/g mouse and 50µg clopidogrel/g; control treatment was DMSO alone. One hour after treatment, whole blood (WB) was collected by aseptic cardiac puncture and mixed in the following groups: aspirin treated RFP and GFP WB, clopidogrel treated RFP and GFP WB, aspirin and clopidogrel treated RFP and GFP WB, control treated RFP and GFP WB. Each combined sample was then treated with a panel of agonists: no agonist, 0.5U/mL thrombin, 20µM ADP, and 500µg/mL arachidonic acid. Thrombin samples were activated for 2 minutes at room temperature while ADP and arachidonic acid samples were activated for 10 minutes at 37°C. Platelets were labeled with anti-CD41a to label all platelets and anti-CD62P to label activated platelets. Aggregation is measured as double-colored GFP and RFP platelet events. Compared to control mice, mice treated with antiplatelet agents demonstrated statistically significant decreases in activation following thrombin administration (ranging from 90% to 83% activated); there was no significant difference in platelet aggregation following thrombin among the samples from different antiplatelet therapies. Following ADP activation, clopidogrel treatment decreased platelet activation (1% activation) compared to control (3% activation) and aspirin-treated (5% activation) mice with no additional decrease in dual treatment (1% activation); unexpectedly, aspirin treatment alone or dual therapy decreased platelet aggregation with ADP (15% and 17% aggregated, respectively) compared to control and clopidogrel (23% and 27% aggregated, respectively). Finally, after arachidonic acid activation, aspirin treatment significantly decreased activation (7% activated) compared to control (20% activated), while clopidogrel decreased activation more than that of aspirin (3% activated), with no additional decrease from dual therapy (3% activated). Though not significant, aspirin treatment (1.4% aggregation) and dual therapy (1.2%) demonstrated a trend with decreased platelet aggregation following arachidonic acid activation compared to control (1.8% aggregation) and clopidogrel-treated platelets (3.2%). These data presented here show a novel application of platelet activation and aggregation of GFP and RFP platelet populations in a mouse model following aspirin and/or clopidogrel treatment. This model can be applied generally to other drugs and disease models for platelet dysfunction using additional markers for platelet activation. Additionally, these experiments can be used to further investigate the function of transfused murine platelets.

PB0429 Potential Difference in Platelet Aggregation between Clinical Dexmedetomidine and Experimental Medetomidine Due to Dose Differences

PB0429 Potential Difference in Platelet Aggregation between Clinical Dexmedetomidine and Experimental Medetomidine Due to Dose Differences

Does platelet aggregation differ among chronic myeloid leukemia-chronic phase (CML-CP) patients on tyrosine kinase inhibitors (TKIs)? A tertiary center experience

Abstract Background Tyrosine kinase inhibitors (TKIs) have improved the prognosis of chronic myeloid leukemia (CML) by inhibiting the BCR-ABL kinase. There are concerns regarding the effect of TKI on hemostasis by inhibiting platelet aggregation; the possible reason for this is yet unclear. Objectives To study platelet aggregation response to different agonists [(adenosine diphosphate (ADP), collagen, and arachidonic acid (AA)] using platelet aggregometry in 75 CML-chronic phase (CML-CP) patients on TKI therapy, in complete hematologic response (CHR). Patients and methods This study included 75 CML patients of both sexes of age 32–66 years. A detailed medical history, clinical examination, and platelet aggregation by PAP-4 platelet aggregometer were done for all patients. Results Imatinib-treated CML patients had a lower platelet aggregation response to AA (less than 50% aggregation) than those on nilotinib either first- or second-line treatment, in a statistically significant manner (P=0.001, P=0.025) for both comparisons. But there was no statistically significant difference in platelet aggregation between patients on nilotinib either first- or second-line therapy (P=0.073). Conclusion Platelet aggregation response to collagen and ADP was normal in all CML-CP patients, but it had an impaired response to AA&lt;AQ: Pls check whether the change is appropriate&gt;. Further studies are needed to establish the particular mechanism of this inhibition.

Ticagrelor inhibits platelet aggregation and reduces inflammatory burden more than clopidogrel in patients with stages 4 or 5 chronic kidney disease

BackgroundNo study has compared pharmacologic properties of ticagrelor and clopidogrel in non-dialysis patients with stage 4–5 chronic kidney disease (CKD). MethodsWe conducted a double-blind RCT to compare effects of ticagrelor and clopidogrel in 48 CKD, with the primary outcome of ADP-induced platelet aggregation (WBPA) after 2 weeks of DAPT. In a parallel arm, we compared effects of 2 weeks of ticagrelor plus aspirin on mean changes in WBPA and markers of thromboinflammation among non-CKD controls (n = 26) with that of CKD in the ticagrelor-arm. ResultsAverage age of CKD was 53.7 years, with 62% women, 54% African American, and 42% with stage 5 CKD. Ticagrelor generated statistically lower WBPA values post treatment [median 0 Ω (IQR 0, 2)] vs. clopidogrel [median 0 Ω (IQR 0, 5)] (P = 0.002); percent inhibition of WBPA was greater (87 ± 22% vs. 63 ± 50%; P = 0.04; and plasma IL-6 levels were much lower (8.42 ± 1.73 pg/ml vs. 18.48 ± 26.56 pg/ml; P = 0.04). No differences in mean changes in WBPA between CKD-ticagrelor and control groups were observed. Ticagrelor- DAPT reduced levels of IL-1α and IL-1β in CKD-ticagrelor and control groups, attenuated lowering of TNFα and TRAIL levels in CKD-ticagrelor (vs controls), and had global changes in correlation between various cytokines in a subgroup of CKD-ticagrelor subjects not on statins (n = 10). Peak/trough levels of ticagrelor/metabolite were not different between CKD-ticagrelor and control groups. ConclusionsWe report significant differences in platelet aggregation and anti-inflammatory properties between ticagrelor- and clopidogrel-based DAPT in non-dialysis people with stage 4–5 CKD. These notable inflammatory responses suggest ticagrelor-based DAPT might lower inflammatory burden of asymptomatic patients with stage 4 or 5 CKD. (clinicaltrials.gov # NCT03649711).

Pharmacological Difference Between Platelet Aggregations in Cardioembolic Stroke Patients with Direct Oral Anticoagulants: A Pilot Study

Background Selecting the appropriate direct oral anticoagulants (DOACs) for embolic ischemic stroke patients, especially on concurrent antiplatelet therapy, is important. However, a limited number of studies have reported on the pharmacological differences in platelet aggregation of each DOAC. We aimed to evaluate the antiplatelet effects of selected DOACs, by comparing dabigatran (a direct oral thrombin inhibitor) and factor Xa (FXa) inhibitors (apixaban and rivaroxaban) in patients who had suffered a cardioembolic stroke.Methods We retrospectively evaluated 12 patients diagnosed with a cardioembolic stroke who took any DOAC without an antiplatelet drug and underwent platelet aggregation tests within 60 days from the onset of symptoms. The platelet aggregation tests were analyzed by both light transmission aggregometry and VerifyNow®.Results Six patients (50%) took dabigatran, while the other six (50%) took an FXa inhibitor (n = 4 for apixaban and n = 2 for rivaroxaban). From the light transmission aggregometry analysis, it was found that the maximal extent of aggregation for adenosine diphosphate (ADP) was significantly higher with dabigatran than with FXa inhibitors, and the ED50 value of ADP on platelet aggregation was significantly lower with dabigatran than with FXa inhibitors. Moreover, the VerifyNow® analyses revealed that P2Y12 reaction units were significantly higher with dabigatran than with FXa inhibitors.Conclusions Dabigatran had little impact on platelet aggregation compared to FXa inhibitors in patients who had suffered a cardioembolic stroke with atrial fibrillation, and who took DOACs for secondary prevention within 60 days from the onset.

A Systematic Review on the Effect of Common Medications on Platelet Count and Function: Which Medications Should Be Stopped Before Getting a Platelet-Rich Plasma Injection?

Background:Platelet-rich plasma (PRP) exerts its effect through the release of growth factors and cytokines from the platelet concentrate. Certain medications may affect platelet count or function, resulting in decreased efficacy of PRP injections.Purpose:To systematically review the literature regarding common medications and their effects on platelets to establish guidelines for which medications should be stopped before obtaining a PRP injection.Study Design:Systematic review; Level of evidence, 2.Methods:This review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A search for studies assessing the effect of common medications on platelet count or platelet function was performed of the PubMed, Cochrane Library, Web of Science, and OpenGrey databases. Inclusion criteria were as follows: drug studied was aspirin, acetaminophen, a nonsteroidal anti-inflammatory drug (NSAID), a statin, or gabapentin; human participants; and article in the English language. Risk of bias was assessed using the Cochrane Risk of Bias tool and the Risk of Bias in Non-randomised Studies—of Interventions tool.Results:A total of 1711 studies were identified through the initial search, with 20 studies meeting all inclusion criteria. No studies involving gabapentin met all inclusion criteria. Patients treated with aspirin (268 patients) or acetaminophen (13 patients) showed a significant decrease in platelet aggregation. Statin therapy (73 patients) did not result in a significant decrease in platelet aggregation. Patients who took NSAIDs (172 patients) demonstrated significantly decreased platelet aggregation only when treated with nonselective formulations. Those treated with cyclooxygenase (COX)-2–selective NSAIDs showed no significant difference in platelet aggregation. Treatment with aspirin, acetaminophen, statins, or NSAIDs did not lead to a significant decrease in platelet count.Conclusion:Aspirin, acetaminophen, and nonselective NSAIDs should be considered for suspension before a PRP injection because of their potential to diminish the effects of the injection. COX-2–selective NSAIDs and statins do not need to be withheld before a PRP injection.

Is endothelial dysfunction a driving force of COVID-19 induced coagulopathy?

Background/IntroductionThere are numerous reports regarding the direct endothelial damage by the SARS-CoV-2 that can lead to activation of both plasma hemostasis and platelet aggregation. However, the mechanism of interaction between endothelium and haemostasis in COVID-19 remains unclear.PurposeThe aim of our study was to assess the relationship between each link of clot formation process (endothelial function, plasma coagulation, platelet aggregation) with the severity of the disease.Methods58 COVID-19 patients were included in our study. Patients were divided into moderate (n=39) and severe (n=18) subgroups. All patients underwent a flow-mediated dilation (FMD) test, impedance aggregation, rotational thromboelastometry, thrombodynamics and von Willebrand factor antigen (vWF: Ag) quantification. All measurements were repeated on days 3 (point 2) and 9 (point 3) of hospitalization.ResultsCOVID-19 patients demonstrated the enhanced plasma coagulation (clotting time, s 613,0 [480; 820], clot growth rate, μm/min 32,75 [29,3; 38,7]). At point 1 no significant difference in parameters of plasma coagulation between patients' subgroups was noted. At point 2 a significant decrease in the size (CS, μm 1278.0 [1216.5; 1356.5] vs 965.0 [659.8; 1098.0], p<0,01) and clot growth rate (μm/min 32,4 [29,2; 35,0] vs 17,7 [10,3; 24,4], p<0,01) under the influence of anticoagulants in the moderate subgroup compared with point 1 was observed. We didn't observe such phenomenon in severe subgroup.There was no significant difference in platelet aggregation between subgroups at point 1. During the course of the disease the patients in the moderate and severe subgroups demonstrated a significant increase in platelet aggregation induced by arachidonic acid and ADP (severe: AUC ARA 48,0 [25,0; 59,0] vs 77,5 [55,8; 92,7], p=0,04; AUC ADP 44,0 [41,0; 56,0] vs 58,0 [45,5; 69,0], p=0,04; moderate: AUC ARA 31,5 [19,8; 50,7] vs 56,0 [39,0; 76,0], p=0,01; AUC ADP 43,0 [20,0; 59,0] vs 56,6 [50,3; 70,5], p=0,04;), in moderate subgroup the significant increase in TRAP-induced aggregation was also noted (AUC TRAP 58,0 [41,0; 69,5] vs 76,0 [58,3; 81,5], p=0,048).There were no significant differences in the FMD-test results between the patient subgroups. FMD-test results were predominantly within the reference ranges (7,1 [4,0; 8,8]).Patients in the severe subgroup had significantly higher levels of vWF: Ag (228,0 [205,3; 240,7] vs 232,0 [226,0; 423,0], p=0,03).ConclusionSARS-CoV-2 infection was characterized by increased levels of vWF:Ag, that could represent the local endothelial damage, meanwhile there was no generalized endothelial dysfunction assessed via FMD-test in moderate to severe patients. At the same time the enhanced plasma coagulation in COVID-19 patients was observed.FUNDunding AcknowledgementType of funding sources: None.

The use of impedance aggregometry to evaluate platelet function after the administration of DDAVP in healthy dogs treated with aspirin or clopidogrel.

To evaluate the effect of 1-Desamino-8-d-arginine vasopressin (DDAVP; desmopressin acetate) on platelet aggregation in healthy dogs receiving aspirin or clopidogrel. 7 healthy staff-owned dogs. In this randomized double-blinded crossover study, impedance aggregometry was performed on samples of lithium-heparinized whole blood samples from dogs before (T0) treatment with aspirin (1 mg/kg, PO, q 24 h for 4 days; ASP group) or clopidogrel (1 mg/kg, PO, q 24 h for 4 days; CLP group) and then before (T1) and after (T2) treatment with DDAVP (0.3 μg/kg, IV, once). There was a 14-day washout period before the crossover component. Aggregometry was performed with 4 different assays, each of which involved a different agonist reagent to stimulate platelet function: ADP, thrombin receptor activating peptide-6, arachidonic acid, or collagen type 1. Median results for platelet aggregometry with agonist reagents ADP, arachidonic acid, or thrombin receptor activating peptide-6 significantly decreased between T0 and T1 for the CLP group; however, no meaningful difference in platelet aggregation was detected in the ASP group. Results for platelet aggregometry did not differ substantially between T1 and T2 regardless of treatment group or assay. Findings suggested that administration of DDAVP may have no effect on platelet aggregation (measured with platelet aggregometry) in healthy dogs treated with clopidogrel. Because no inhibition of platelet aggregation was detected for dogs in the ASP group, no conclusion could be made regarding the effects of DDAVP administered to dogs treated with aspirin.

Arachidonic acid-induced platelet aggregation and acetylsalicylic acid treatment during pregnancy in women with recurrent miscarriage, a post hoc study

In this post hoc study, arachidonic acid (AA)-induced platelet aggregation during pregnancy with and without acetylsalicylic acid (ASA) treatment was studied in 323 women with unexplained recurrent first-trimester miscarriage and in 59 healthy women with normal pregnancies. All women had normal AA-induced platelet aggregation in the non-pregnant state. Women with recurrent miscarriage were treated with 75 mg ASA or placebo daily. AA-induced platelet aggregation was measured with multiple electrode impedance aggregometry and presented in units (U), where 1 U = 10 aggregation units x minutes. There were no significant differences in platelet aggregation between placebo-treated women with recurrent miscarriage and healthy women. The mean differences were -0.7 (95%CI; −7.0; 5.6) U in the non-pregnant state, 3.8 (95%CI; −4.6; 12.2) U during the late first trimester and 1.7 (95%CI; −6.7; 10.3) U and 4.1 (95%CI; −3.9; 12.0) U during the early and late third trimester, respectively. ASA reduced platelet aggregation by median −84.0% (Q1; Q3; −89.8; −76.3), −79.9% (−84.7; −69.2) and −75.7% (−83.5; −49.5), respectively, during pregnancy. The degree of inhibition by ASA decreased during the third trimester (p < .0001). There were two (1.9%) complete non-responders to ASA and 32.1% with a partial response. The rate of subsequent miscarriage was not affected by ASA, which did not seem to influence the rate of early miscarriage if treatment was initiated when a viable pregnancy was detectable by ultrasound.

Influence of exercise test on platelet function in patients with coronary arterial disease: A systematic review.

Background:Exercise test (ET) may have adverse effects on platelet function and induce acute thrombotic events in patients with coronary artery disease (CAD). The aim of this study is to investigate the platelet function and evaluate the risk of thrombotic events in CAD patients during ET.Methods:Pubmed, Embase, Cochrane Library, and Web of Science were searched for a systematic review from initiation to October 2019. The inclusion criteria were controlled clinical trails as study design; investigating platelet function in CAD patients during ET; with ET carried out by treadmill or bicycle ergometer; written in English. Included articles were screened based on title/abstract and full-text review by 2 independent reviewers. Platelet aggregation (PA), platelet surface expression of CD62p and PAC-1, plasma levels of platelet factor 4 (PF4) and beta-thromboglobulin (β-TG) were evaluated before and after ET.Results:Eighteen articles were included out of the 427 references initially identified. In most of the studies included ET was terminated because of limited symptoms. Prior to ET, no difference in platelet aggregation was observed in CAD patients compared with healthy controls in majority of the studies, with or without the treatment with Aspirin. Dual anti-platelet therapy suppressed adenosine diphosphate (ADP)-induced platelet aggregation at rest. After ET, platelet aggregation, the serum levels of β-thromboglobulin were found unchanged in majority of studies and platelet factor-4 were found unchanged in half of studies. The expression of platelet surface markers were elevated by ET in a few study.Conclusion:Symptom-limited exercise test did not affect platelet function in patients with coronary artery disease; however exercise to higher intensity may induce platelet activation.

Camel platelet aggregation responses and the antiplatelet effect of camel urine: comparison between black and white camels

Human black and white-skinned races exhibited differences in platelet aggregation. However, no similar differences were described on white and black camels. This study aims to find out whether black and white camel skin color is associated with differences in camel platelet aggregation responses or the platelet inhibitory activity of their urine. Platelet aggregometry was undertaken in black and white camels, in response to adenosine diphosphate (ADP), Arachidonic acid (AA), Epinephrine (EPN), collagen, and Ristocetin. Platelet aggregometry was also done in human PRP after the addition of raw and serially diluted (1:2, 1:4 and 1:8) white and black camel urines. In black camels, platelet aggregation in response to ADP, AA, EPN and Collagen were slightly higher than in white camels. The addition of raw camel urine collected from mixed population of black and white camels to human platelets resulted in inhibition of platelet aggregation. Serial dilutions of camel urine (1:2, 1:4, 1:8) resulted initially in loss of the inhibitory action followed by enhancement of human platelet aggregation responses to ADP and AA. The neat and serially diluted white camel urines caused more inhibition of the human platelet aggregation responses than the black camel urines. This study uncovered a new biological feature in the camels. The camel skin color seems to be associated with different platelet aggregation responses as well as different antiplatelet activity of the camel urine; white camel urine was found to cause more platelet inhibition than black camel urine.

Sex differences in platelet reactivity in patients with myocardial infarction treated with triple antiplatelet therapy - results from assessing platelet activity in coronary heart disease (APACHE)

)Several earlier studies have reported increased risk of bleeding in women with myocardial infarction, (MI) compared to men. The reasons for the observed difference are incompletely understood, but one suggested explanation has been excess dosing of antithrombotic drugs in women. The aim of this prospective observational study was to assess sex differences in platelet activity in patients treated with three different platelet inhibitors. We recruited 125 patients (37 women and 88 men) with MI, scheduled for coronary angiography. All patients received clopidogrel and aspirin. A subgroup of patients received glycoprotein (GP) IIb/IIIa-inhibitor. Platelet aggregation in whole blood was assessed at several time points, using impedance aggregometry. Soluble P-selectin was measured 3 days after admission. There were no significant differences between women and men in baseline features or comorbidities except higher frequency of diabetes, lower hemoglobin value, and lower estimated glomerular filtration rate, in women on admission. We observed significantly more in-hospital bleeding events in women compared to men (18.9% vs. 6.8%, p = .04). There were no differences in platelet aggregation using three different agonists, reflecting treatment effect of GPIIb/IIIa-inhibitors, clopidogrel, and aspirin, 6–8 hours, 3 days, 7–9 days, or 6 months after loading dose. Moreover, there was no significant difference in soluble P-selectin. The main finding of this study was a consistent lack of difference between the sexes in platelet aggregation, using three different agonists at several time-points. Our results do not support excess dosing of anti-platelet drugs as a major explanation for increased bleeding risk in women.

Changes in Red Blood Cell Properties and Platelet Function during Extracorporeal Membrane Oxygenation.

Extracorporeal membrane oxygenation (ECMO) is associated with frequent hemorrhagic and thromboembolic complications. The multiple effects of ECMO include inflammatory response on contact with the circuit; hemolysis acquired von Willebrand syndrome likely affects the function of red blood cells (RBC) and platelets. The aim of this prospective observational study was to analyze RBC aggregation and elongation (deformability) and platelet aggregation in the first week of ECMO. Sixteen patients were included. Blood samples were taken prior to initiation of ECMO and on days 1, 2, 3, 5, and 7. RBC aggregation and elongation were analyzed using the laser-assisted optical rotational red cell analyzer (Lorrca). Upstroke, top, and amplitude as indices of aggregation showed significant time effects. RBC elongation was not affected at low shear stress. At high shear stress there was an increase in the elongation index at day 2 (p = 0.004), followed by a decrease. Platelet function was analyzed using multiple electrode aggregometry (Multiplate®). In pairwise comparison in the days 1–7 to the value prior to ECMO there was no significant difference in platelet aggregation by any of the three agonists (ADP p = 0.61; TRAP p = 0.77; Ristocetin p = 0.25). This implies that the rheology of RBCs seemed to be more affected by ECMO than platelets. Especially the red blood cell deformability continues to decline at higher shear stress.

Platelet aggregation is not altered among men with diabetes mellitus.

Platelets are pivotal in arterial thrombosis, and platelet hyperresponsiveness may contribute to the increased incidence of cardiovascular events in diabetes mellitus. Consequently, we hypothesized that increased in vitro platelet aggregation responses exist in men with diabetes mellitus. The Danish Cardiovascular Screening Trial (DANCAVAS) is a community-based cardiovascular screening trial including men aged 65-74years. Platelet aggregation was tested using 96-well light transmission aggregometry with thrombin receptor-activating peptide (TRAP), adenosine diphosphate, collagen type 1, arachidonic acid and protease-activated receptor-4 in three concentrations. Further, cardiovascular risk factors and coronary artery calcification (CAC), estimated by CT scans and ankle-brachial index, were obtained. Included were 720 men aged 65-74years, 110 with diabetes mellitus. Overall, there was no difference in platelet aggregation among men with versus without diabetes mellitus when adjusting for or excluding platelet inhibitor treatment and men with established cardiovascular disease (CVD). This was true for all agonists, e.g., 10µM TRAP-induced platelet aggregation of median 69% (IQR 53-75) versus 70% (IQR 60-76) in men with versus without diabetes mellitus. Platelet aggregation did not correlate with HbA1c or CAC. Men with diabetes mellitus displayed higher CAC, median 257 Agatston units (IQR 74-1141) versus median 111 Agatston units (IQR 6-420) in the remaining individuals, p < 0.0001. Among outpatients with diabetes mellitus, but no CVD and no platelet inhibitor treatment, neither are platelets hyperresponsive in diabetes mellitus, nor is platelet aggregation associated with glycemic status or with the degree of coronary atherosclerosis. ISRCTN12157806.

The Influence of Inflammation on Fibrinogen Turnover and Redistribution of the Hemostatic Balance to a Prothrombotic State in High On-Treatment Platelet Reactivity-Dual Poor Responder (HTPR-DPR) Patients.

Knowledge about the influence of inflammation on platelet function and relocation of hemostatic balance to hypercoagulable state is still unclear. We compared two groups of patients who suffer from acute vs. chronic inflammatory process and additionally present high on-treatment platelet reactivity-dual platelet resistance. We did not found any differences in platelet aggregation between both investigated groups, but patients who suffer from chronic inflammation presented stronger relocation of the hemostatic balance to the hypercoagulability. A high concentration of prothrombin fragment F1+2 together with higher activity of von Willebrand factor in critical limb ischemia shows more exaggerated fibrinogen turnover although the blood concentration of this factor was in normal range. We concluded that high on-treatment platelet reactivity-dual platelet resistance and intensified inflammation are linked with elevated platelet and fibrinogen turnover to counteract proper hemostatic balance in favor of a prothrombotic state.

Dose-response effects of omega-3 on platelet aggregation: an observational study.

ObjectiveThis study aimed to evaluate the dose-response effects of supplemental omega-3 fatty acids on platelet function in healthy volunteers.MethodsTwelve healthy volunteers ingested a normal supplemental dose of 1260 mg omega-3 fatty acids daily for 5 days, followed by a high dose of 2520 mg daily for another 5 days. Multiple electrode aggregometry (MEA) with four different agonists was used to measure platelet aggregation before and after the normal- and high-dose regimes. In vitro spiking using physiological doses of omega-3 fatty acids was also performed to determine whether MEA is capable of detecting a platelet-inhibiting effect due to omega-3 fatty acids.ResultsThere were no differences in platelet aggregation measured by the MEA assay in healthy volunteers after intake of either the normal or high dose of omega-3 fatty acids. In the in vitro experiment, a platelet-inhibiting effect of omega-3 fatty acids was shown by an arachidonic acid agonist in MEA .ConclusionsSupplemental omega-3 fatty acids do not evoke their positive health effects through inhibition of platelet aggregation measurable with MEA.

Platelet Aggregation in Healthy Participants is Not Affected by Smoking, Drinking Coffee, Consuming a High-Fat Meal, or Performing Physical Exercise.

Platelet aggregation can be measured using optical aggregation (light transmission aggregometry, LTA) as well as by impedance (Multiplate analyzer). The LTA (the gold standard method) can be influenced by many preanalytical variables. Several guidelines differ in recommendations for the duration patients should refrain from smoking, coffee, fatty meals, and physical exercise prior to blood collection for performing platelet function tests. In this pilot study, the influence of smoking, coffee, high-fat meal, or physical exercise on platelet aggregation was investigated to improve patient friendliness and laboratory logistics in platelet function diagnostics. Standardized blood collection was performed when participants were fasting and after each parameter (n=5 per group). As a control for diurnal fluctuations, participants (n=6) were fasting during both blood collections. Platelet aggregation was executed using standardized methods for LTA and Multiplate analyzer. Statistical analysis of the results using Wilcoxon signed-rank test did not show any significant differences in platelet aggregation in healthy participants under different preanalytical variables. Therefore, these variables are not expected to adversely affect testing, which can avoid canceling tests for those patients who inevitably did.

Influence of hyperinsulinemic – hypoglycemic clamp on induced platelet aggregation, activity of physiological anticoagulants and von Willebrand factor in patients with type I diabetes

Background. Intensive glycaemic control in patients with type 1 diabetes may lead to hypoglycaemia and thus increase the risk of cardiovascular and cerebrovascular events. Platelet activation and/or decreased activity of physiological anticoagulants during hypoglycaemia may play a role in the development of cardiovascular or cerebrovascular complications.&#x0D; Aims. To investigate induced platelet activity, the activity of physiological anticoagulants, and the von Wil-lebrand factor in patients with type 1 diabetes with the hyperinsulinaemichypoglycaemic clamp.&#x0D; Materials and methods. We examined 11 patients with type 1 diabetes without macro- and micro-vascular complications (6 males, 5 females, mean age 23.7 5.6 years, A1C 9.7 2.3%). Induced platelet aggregation, physiological anticoagulants (Protein S, Protein C, AT III) and the von Willebrand factor were studied at hyperglycaemic, euglycaemic, and hypoglycaemic stages during use of a hyperinsulinaemic (1 mU/kg/min) hypoglycaemic clamp.&#x0D; Results. Platelet aggregation to all agonists increased significantly during the hypoglycaemic stage, compared with the euglycaemic or hyperglycaemic stages. There was no difference in platelet aggregation between the euglycaemic and hyperglycaemic stages. Platelet aggregation to all agonists increased during the hypoglycaemic stage compared with the hyperglycaemic period: thrombin23.9%, ADP30.6%, arachidonic acid30.9%, collagen69.4% and ristocetin70.8%. During hypoglycaemia aggregation to ADP, arachidonic acid and collagen remained within normal limits (upper quartile); aggregation to thrombin was significantly above normal limits and aggregation to ristocetin remained significantly below lower limits. Protein S activity was significantly increased during hypoglycaemia compared with euglycaemia (p = 0.046) and hyperglycaemia (p = 0.046). Antithrombin-III activity decreased significantly at the euglycaemic and hypoglycaemic stages, compared with the hyperglycaemic period, but still remained significantly elevated above the upper threshold. Protein C and vWf activity did not change significantly.&#x0D; Conclusions. In patients with type 1 diabetes platelet aggregation and protein S activity increases significantly at the hypoglycaemic stage of the hyperinsulinaemichypoglycaemic clamp. Platelet activation is directly caused by hypoglycaemia and not by decreasing glucose levels. Increased protein S activity is a compensatory response to platelet activation.

Inhibitory mechanisms of very low–dose rivaroxaban in non–ST-elevation myocardial infarction

AbstractVery low–dose (VLD) factor Xa (FXa) inhibition, in combination with acetylsalicylic acid (ASA) and clopidogrel, is associated with improved outcomes in patients with acute coronary syndrome (ACS) with a tolerable bleeding risk profile. To date, there are no data documenting platelet inhibition and the anticoagulatory effects of VLD FXa inhibition on top of guideline-adherent dual-antiplatelet therapy (DAPT) in patients with ACS. Patients with non–ST-elevation myocardial infarction (NSTEMI) receiving oral DAPT (ASA + clopidogrel, n = 20; or ASA + ticagrelor, n = 20) were prospectively enrolled in a nonrandomized study. Coagulation- and platelet-dependent thrombin generation (TG), measured by means of the calibrated automated thrombogram, were significantly decreased after in vitro and in vivo addition of rivaroxaban. As shown by a total thrombus-formation analysis approach, rivaroxaban treatment led to a significantly decreased coagulation-dependent (AR-chip) thrombus formation in patients treated with ASA plus P2Y12 inhibitor (clopidogrel/ticagrelor), whereas the pure platelet-dependent (PL-chip) thrombus formation was not affected at all. Adjunctive rivaroxaban therapy was not associated with significant differences in platelet aggregation assessed by light-transmission aggregometry (LTA). Nevertheless, according to fluorescence-activated cell sorter analysis, VLD rivaroxaban treatment resulted in a significantly reduced expression of platelet HMGB-1, whereas P-selectin exposure was not affected. Furthermore, an enhanced effect of rivaroxaban on total thrombus formation and TG was observed in particular in clopidogrel nonresponder patients defined as adenosine 5′-diphosphate-induced LTA ≥40%. VLD rivaroxaban reduces thrombus formation and platelet-dependent TG in patients with ACS receiving DAPT, which can be of potential ischemic benefit. This trial was registered at www.clinicaltrials.gov as #NCT01417884.