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Background and Aims: Patients with cirrhosis show alterations in primary hemostasis, yet prognostic implications of changes in platelet activation remain controversial, and assay validity is often limited by thrombocytopenia. We aimed to study the prognostic role of platelet activation in cirrhosis, focusing on bleeding/thromboembolic events, decompensation, and mortality., Approach and Results: We prospectively included 107 patients with cirrhosis undergoing a same-day hepatic venous pressure gradient (HVPG) and platelet activation measurement. Platelet activation was assessed using flow cytometry after protease-activated receptor (PAR)-1, PAR-4, or epinephrine stimulation. Over a follow-up of 25.3 (IQR: 15.7-31.2) months, first/further decompensation occurred in 29 patients and 17 died. More pronounced platelet activation was associated with an improved prognosis, even after adjusting for systemic inflammation, HVPG, and disease severity. Specifically, higher PAR-4-inducible platelet activation was independently linked to a lower decompensation risk [adjusted HR per 100 MFI (median fluorescence intensity): 0.95 (95% CI: 0.90-0.99); p =0.036] and higher PAR-1-inducible platelet activation was independently linked to longer survival [adjusted HR per 100 MFI: 0.93 (95% CI: 0.87-0.99); p =0.040]. Thromboembolic events occurred in eight patients (75% nontumoral portal vein thrombosis [PVT]). Higher epinephrine-inducible platelet activation was associated with an increased risk of thrombosis [HR per 10 MFI: 1.07 (95% CI: 1.02-1.12); p =0.007] and PVT [HR per 10 MFI: 1.08 (95% CI: 1.02-1.14); p =0.004]. In contrast, of the 11 major bleedings that occurred, 9 were portal hypertension related, and HVPG thus emerged as the primary risk factor., Conclusions: Preserved PAR-1- and PAR-4-inducible platelet activation was linked to a lower risk of decompensation and death. In contrast, higher epinephrine-inducible platelet activation was a risk factor for thromboembolism and PVT., (Copyright © 2023 American Association for the Study of Liver Diseases.)

Competing Interests: A.D.M.: Consultant to HemostOD; expert witness for Bristol Myers Squibb/Sanofi-Aventis; royalties from Elsevier.A.L.F.: Consultant to HemostOD; grant support from CSL Behring, Prolocor, and RUNX1 Research Program.R.L.H. and H.C.K.: None declared.T.G.: Speaker fees from Amgen, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Daiichi-Sankyo, Novartis, and Pfizer; grant support from Abbott, Boehringer Ingelheim, and Bristol Myers Squibb.

The HeartMate 3 (HM3) left ventricular assist device has decreased thromboembolic events and minimized the risk of pump thrombosis. However, bleeding complications due to combined antithrombotic therapy with a vitamin K antagonist (VKA) and aspirin remain high. Only limited data on the safety of VKA monotherapy in HM3 patients are available. A systematic search on the main databases was performed. Observational data and randomized trials were eligible for this analysis. As primary endpoint, we analyzed hemocompatibility-related adverse events (HRAE). As secondary endpoints, we investigated the individual components of the primary endpoint. The analysis was carried out using the odds ratio (OR) as outcome measure. A random-effects model was fitted to the data. Five manuscripts fulfilled the inclusion criteria. These trials included 785 patients (381 on VKA monotherapy, 404 on VKA and aspirin). VKA monotherapy significantly reduced HRAE (OR: 0.11 [95% confidence interval {CI}: 0.02-0.59], p = 0.01, I2 = 87%). The reduction was driven by a decrease in bleeding complications (OR: 0.12 [95% CI: 0.02-0.62], p = 0.01, I2 = 86%) without increasing the rates of thromboembolic events (OR: 0.69 [95% CI: 0.26-1.81], p = 0.45, I = 0%). Vitamin K antagonist monotherapy is associated with a significant reduction of bleeding events without increasing the risk of thromboembolic complications in HM3 patients., Competing Interests: Disclosure: T.S. received consulting/advisory fees from Medtronic Inc., Abbott Inc., BiVACOR, Berlin Heart, and CorWave; and received grant support from Medtronic Inc., Abbott Inc., Berlin Heart, and CorWave. D.W. is a proctor for Abbott Inc. and received consulting/advisory fees from Abbott Inc. and Xenios/Fresenius Medical Care. D.Z. is a proctor for and received speaker/consulting fees from Medtronic Inc., Abbott Inc., Berlin Heart, Edwards, Abiomed, and grant support from Medtronic Inc. and Abbott Inc. T.G. received speaker/consulting fees from AstraZeneca, Amgen, Bayer, Boehringer-Ingelheim, Bristol Myers Squibb, Daiichi- Sankyo, Novartis, and Pfizer, and grant support from Boehringer-Ingelheim, Bristol Myers Squibb, Medtronic and Abbott. The other authors have no conflicts of interest to report., (Copyright © ASAIO 2024.)

Platelets are the smallest blood cells, numbering 150 to 350 × 10 9 /L in healthy individuals. The ability of activated platelets to adhere to an injured vessel wall and form aggregates was first described in the 19th century. Besides their long-established roles in thrombosis and hemostasis, platelets are increasingly recognized as pivotal players in numerous other pathophysiological processes including inflammation and atherogenesis, antimicrobial host defense, and tumor growth and metastasis. Consequently, profound knowledge of platelet structure and function is becoming more important in research and in many fields of modern medicine. This review provides an overview of platelet physiology focusing particularly on the structure, granules, surface glycoproteins, and activation pathways of platelets., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: Patients with left ventricular assist devices (LVADs) are treated with a potent antithrombotic regimen to prevent pump thrombosis and thromboembolism. High on-treatment residual platelet reactivity (HRPR) is associated with ischemic outcomes in cardiovascular disease., Objectives: In the current study, we investigated the prevalence and clinical impact of HRPR in stable LVAD patients., Methods: Pump thrombosis, bleeding events, and death were assessed in 62 LVAD patients (19 HeartWare HVAD [Medtronic] and 43 HeartMate 3 [Abbott]) during a 2-year follow-up. Platelet aggregation was measured by multiple electrode aggregometry, and HRPR was defined as arachidonic acid (AA)-inducible platelet aggregation of ≥21 aggregation units. Soluble P-selectin was determined by enzyme-linked immunosorbent assay., Results: Three patients (4.8%) had pump thrombosis and 10 patients (16.1%) suffered a bleeding complication. AA-inducible platelet aggregation was significantly higher in patients with pump thrombosis ( P  = .01), whereas platelet aggregation in response to adenosine diphosphate (ADP) and thrombin receptor-activating peptide (TRAP) was comparable between patients without and those with pump thrombosis (both P > .05). Platelet aggregation in response to AA, ADP, and TRAP was similar in patients without and with a bleeding event (all P > .05). HRPR was detected in 29 patients (46.8%) and was associated with significantly higher platelet aggregation in response to AA, ADP, and TRAP as well as higher levels of soluble P-selectin compared with patients without HRPR (all P  < .05). All pump thromboses occurred in patients with HRPR (3 vs 0; P  = .06) and HVAD., Conclusion: Platelet reactivity is associated with pump thrombosis in LVAD patients. HRPR may represent a risk marker for pump thrombosis, particularly in HVAD patients., (© 2024 The Author(s).)

Isolated pulmonary valve endocarditis (IPE) is a rare form of infectious endocarditis. This article reports the case of a 49-year-old patient with IPE who was initially admitted with suspected cholecystitis. After vegetations were detected by transthoracic (TTE) and transesophageal echocardiography (TEE), antibiotic therapy in accordance with the antibiogram was primarily attempted; however, due to persistently elevated infection parameters and structural valve damage a pulmonary valve replacement was eventually performed., (© 2024. The Author(s).)

Background: Only small randomized trials have investigated the efficacy and safety of direct oral anticoagulants (DOACs) compared with vitamin K antagonists (VKAs) in patients with non-valvular atrial fibrillation (NVAF) and end-stage kidney disease., Objectives: To perform a systematic review and meta-analysis comparing anticoagulation with DOACs to VKAs in patients with NVAF undergoing chronic hemodialysis., Methods: A systematic search using Medline, Web of Science, and Embase was performed. All randomized trials comparing DOACs with VKAs in patients with NVAF undergoing chronic hemodialysis were included. As primary endpoint, we analyzed all-cause mortality. As secondary endpoints, we investigated total bleeding events, life-threatening or major bleeding events, and thromboembolic events or stroke. We used the odds ratio as outcome measure and fitted a random-effects model due to the expected heterogeneity., Results: Three studies fulfilled the inclusion criteria comprising 383 patients (218 on apixaban or rivaroxaban, 165 on VKA). No significant difference between DOACs and VKAs regarding death (OR, 0.94; 95% CI, 0.55-1.63; p = .84), total bleedings (OR, 0.99; 95% CI, 0.63-1.54; p = .96) and life-threatening or major bleeding (OR, 0.65; 95% CI, 0.32-1.33, p = .24) was detected. There was a trend toward a reduction of thromboembolic events or stroke in patients receiving DOACs (OR, 0.39; 95% CI, 0.14-1.05; p = .06)., Conclusion: Orally administered activated factor X inhibitors carried a similar risk of bleeding and death when compared with VKAs in patients with NVAF undergoing chronic hemodialysis. Moreover, there was a trend towards a reduction of thromboembolic events or stroke in patients receiving DOACs., (© 2024 The Author(s).)

Background:  Cirrhotic patients display an increased risk for both bleeding and thrombosis. We investigated platelet activation across Child-Pugh stages (CPSs) and portal hypertension (PH) severity., Material and Methods:  A total of 110 cirrhotic patients were prospectively included. CPS and hepatic venous pressure gradient (HVPG) were determined. Platelet surface expression of P-selectin and activated glycoprotein (GP) IIb/IIIa were measured by flow cytometry before/after stimulation with protease-activated receptor (PAR)-1 (thrombin receptor activating peptide, TRAP) and PAR-4 (AYPGKF) agonists, epinephrine, and lipopolysaccharide (LPS)., Results:  Platelet count was similar across CPS but lower with increasing PH severity. Expression of P-selectin and activated GPIIb/IIIa in response to TRAP and AYPGKF was significantly reduced in platelets of CPS-B/C versus CPS-A patients (all p <  0.05). Platelet P-selectin expression upon epinephrine and LPS stimulation was reduced in CPS-C patients, while activated GPIIb/IIIa in response to these agonists was lower in CPS-B/C (all p <  0.05). Regarding PH severity, P-selectin and activated GPIIb/IIIa in response to AYPGKF were lower in HVPG ≥20 mmHg patients (both p <  0.001 vs. HVPG < 10 mmHg). Similarly, activated GPIIb/IIIa was lower in HVPG ≥20 mmHg patients after TRAP stimulation ( p <  0.01 vs. HVPG < 10 mmHg). The lower platelet surface expression of P-selectin and activated GPIIb/IIIa upon stimulation of thrombin receptors (PAR-1/PAR-4) in CPS-B/C and HVPG ≥20 mmHg patients was paralleled by reduced antithrombin-III levels in those patients (all p <  0.05). Overall, PAR-1- and PAR-4-mediated platelet activation correlated with antithrombin-III levels ( p <  0.001)., Conclusion:  Platelet responsiveness decreases with increasing severity of liver cirrhosis and PH but is potentially counterbalanced by lower antithrombin-III levels., Competing Interests: K.B., B.S.H., P.S., and T.R. were co-supported by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development, Boehringer Ingelheim, and the Christian Doppler Research Association. B.S. was supported by the Medical Scientific Fund of the Mayor of the City of Vienna Philips, Gilead, and Siemens and has received speaker fees from AbbVie and Siemens and travel support from AbbVie and Gilead. D.B. has received travel support from Gilead and AbbVie and speaker fees from AbbVie. P.S. was supported by the Medical Scientific Fund of the Mayor of the City of Vienna (Project:18070), received consulting fees from PharmaIN, and travel support from Falk and Phenex Pharmaceuticals. M.M. served as a speaker and/or consultant and/or advisory board member for AbbVie, Bristol-Myers Squibb, Gilead, Collective Acumen, and W. L. Gore & Associates and received travel support from AbbVie, Bristol-Myers Squibb, and Gilead. T.R. received grant support from AbbVie, Boehringer-Ingelheim, Gilead, MSD, Philips Healthcare, and Gore; speaker fees from AbbVie, Gilead, Gore, Intercept, Roche, MSD; consulting/advisory board fees from AbbVie, Bayer, Boehringer-Ingelheim, Gilead, Intercept, MSD, Siemens; travel support from Boehringer-Ingelheim, Gilead, and Roche. T.G. received speaker fees from Amgen, Bayer, Boehringer-Ingelheim, Bristol Myers Squibb, Daiichi-Sankyo, Novartis, and Pfizer, and grant support from Boehringer-Ingelheim, Bristol Myers Squibb, Medtronic, and Abbott., (Thieme. All rights reserved.)

Tularemia is increasing in Austria. We report Francisella tularensis subspecies holarctica isolated from 3 patients who had been bitten by arthropods. Next-generation sequencing showed substantial isolate similarity. Clinicians should consider bloodstream F. tularensis infections for patients with signs/symptoms of ulceroglandular tularemia, and surveillance of potential vectors should be intensified.

Aims: Reduction of low-density lipoprotein cholesterol (LDL-C) decreases cardiovascular mortality and morbidity. Bempedoic acid represents a promising novel lipid-modifying agent for patients who cannot reach guideline recommended LDL-C goals or statin-intolerant patients, but data on safety and cardiovascular outcomes are limited. We therefore aimed to systematically review randomized controlled trials investigating bempedoic acid vs. placebo in patients with hyperlipidaemia., Methods: A systematic search on the databases PubMed, Web of Science, and Embase until 20 March 2023 was performed. All randomized trials comparing bempedoic acid (180 mg daily) with placebo in patients with an indication for lipid-lowering therapy were included. As a primary endpoint, we analysed three-point major adverse cardiovascular events (MACEs) consisting of cardiovascular death, non-fatal myocardial infarction (MI), or non-fatal stroke. The analysis was carried out using the odds ratio (OR) as the outcome measure. Due to the expected heterogeneity across studies, a random-effects model was fitted to the data., Results: Out of 258 manuscripts, 10 manuscripts fulfilled the inclusion criteria. In total, these trials included 18 200 patients (9765 on bempedoic acid, 8435 on placebo). Bempedoic acid significantly reduced MACEs compared with placebo (OR 0.84 [95% confidence interval (CI) 0.76-0.96]; P < 0.001; I2 = 0%). The endpoint reduction was driven by a lower rate of non-fatal MI, whereas bempedoic acid had no significant effect on stroke (OR 0.86 [95% CI 0.69-1.08]; P = 0.20, I2 = 0%) and all-cause mortality (OR 1.19 [95% CI 0.73-1.93]; P = 0.49; I2 = 18%)., Conclusion: Bempedoic acid reduced non-fatal MI in patients with hyperlipidaemia, whereas it had no significant effect on stroke and all-cause mortality., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Inflammation has a critical role in the development and progression of atherosclerosis. On the molecular level, inflammatory pathways negatively impact endothelial barrier properties and thus, tissue homeostasis. Conformational changes and destruction of the glycocalyx further promote pro-inflammatory pathways also contributing to pro-coagulability and a prothrombotic state. In addition, changes in the extracellular matrix composition lead to (peri-)vascular remodelling and alterations of the vessel wall, e.g., aneurysm formation. Moreover, progressive fibrosis leads to reduced tissue perfusion due to loss of functional capillaries. The present review aims at discussing the molecular and clinical effects of inflammatory processes on the micro- and macrovasculature with a focus on peripheral artery disease.

Toll-like receptors (TLRs) have a critical role in the pathogenesis and disease course of viral infections. The induced pro-inflammatory responses result in the disturbance of the endovascular surface layer and impair vascular homeostasis. The injury of the vessel wall further promotes pro-thrombotic and pro-coagulatory processes, eventually leading to micro-vessel plugging and tissue necrosis. Moreover, TLRs have a direct role in the sensing of viruses and platelet activation. TLR-mediated upregulation of von Willebrand factor release and neutrophil, as well as macrophage extra-cellular trap formation, further contribute to (micro-) thrombotic processes during inflammation. The following review focuses on TLR signaling pathways of TLRs expressed in humans provoking pro-thrombotic responses, which determine patient outcome during viral infections, especially in those with cardiovascular diseases.

Cardiovascular disease, particularly coronary artery disease (CAD), remains the leading cause of mortality and morbidity in industrialized countries. Platelet activation and aggregation at the site of endothelial injury play a key role in the processes ultimately resulting in thrombus formation with vessel occlusion and subsequent end-organ damage. Consequently, antiplatelet therapy has become a mainstay in the pharmacological treatment of CAD. Several drug classes have been developed over the last decades and a broad armamentarium of antiplatelet agents is currently available. This review portrays the evolution of antiplatelet therapy, and provides an overview on previous and current antiplatelet drugs and strategies., Competing Interests: None declared., (Thieme. All rights reserved.)

Background:  The ABO blood group system is linked to hemostasis via its relationship with von Willebrand factor (VWF) and factor VIII (FVIII). In the current study, we investigated the association of the ABO system with clinical outcomes as well as VWF and platelet function in patients with left ventricular assist devices (LVADs)., Methods:  Bleeding and thromboembolic complications were assessed in 111 patients during 1 year after LVAD implantation. In 67 LVAD patients, VWF antigen, VWF activity, VWF ristocetin cofactor, VWF collagen-binding, and FVIII activity were assessed. Platelet surface P-selectin and activated glycoprotein IIb/IIIa were determined by flow cytometry, and soluble P-selectin was measured with an enzyme-linked immunoassay. Platelet aggregation was assessed by light transmission and impedance aggregometry., Results:  Thirty-six patients (32.4%) experienced a bleeding and 22 patients (19.8%) a thromboembolic event. In univariate analyses, patients with blood group O had numerically more bleeding complications and less thromboembolic events as compared to patients with blood group non-O (both p ≥ 0.05). After multivariable adjustment, blood group O was significantly associated with a higher risk of bleeding (hazard ratio 2.42 [95% confidence interval 1.03-5.70], p  = 0.044) but not linked to thromboembolic complications., Conclusion:  Patients with blood group O had significantly lower levels of VWF and FVIII (all p  < 0.05), whereas P-selectin expression in response to thrombin-receptor activating peptide and soluble P-selectin were higher as compared to patients with blood group non-O (both p  < 0.05). LVAD patients with blood group O are at an increased bleeding risk, potentially due to lower VWF and FVIII levels., Competing Interests: T.S. received research grants from Abbott, CorWave, and Medtronic, and is a consultant for Abbott and Medtronic. D.W. is a consultant and proctor for Abbott and Medtronic. D.Z. received research grants from Abbott and Medtronic, is an advisory board member for Abbott, Medtronic, and Berlin Heart, and is a proctor for Abbott and Medtronic. T.G. received research grants from Boehringer-Ingelheim, Bristol Myers Squibb, Medtronic, and Abbott, and lecture fees from Amgen, Boehringer-Ingelheim, Bayer, Bristol Myers Squibb, Vifor, Daiichi Sankyo, Pfizer, and Novartis. The other authors have no relevant conflicts of interest to declare., (Thieme. All rights reserved.)

Bleeding events in patients with acute coronary syndrome (ACS) are a risk factor for adverse outcomes, including mortality. We investigated the association of growth differentiation factor (GDF)-15, an established predictor of bleeding complications, with on-treatment platelet reactivity in ACS patients undergoing coronary stenting receiving prasugrel or ticagrelor. Platelet aggregation was measured by multiple electrode aggregometry (MEA) in response to adenosine diphosphate (ADP), arachidonic acid (AA), thrombin receptor-activating peptide (TRAP, a protease-activated receptor-1 (PAR-1) agonist), AYPGKF (a PAR-4 agonist) and collagen (COL). GDF-15 levels were measured using a commercially available assay. GDF-15 correlated inversely with MEA ADP (r = -0.202, p = 0.004), MEA AA (r = -0.139, p = 0.048) and MEA TRAP (r = -0.190, p = 0.007). After adjustment, GDF-15 was significantly associated with MEA TRAP ( β = -0.150, p = 0.044), whereas no significant associations were detectable for the other agonists. Patients with low platelet reactivity in response to ADP had significantly higher GDF-15 levels ( p = 0.005). In conclusion, GDF-15 is inversely associated with TRAP-inducible platelet aggregation in ACS patients treated with state-of-the-art antiplatelet therapy and significantly elevated in patients with low platelet reactivity in response to ADP.

Platelet-endothelial interactions have a critical role in microcirculatory function, which maintains tissue homeostasis. The subtle equilibrium between platelets and the vessel wall is disturbed by the coronavirus disease 2019 (COVID-19), which affects all three components of Virchow's triad (endothelial injury, stasis and a hypercoagulable state). Endotheliitis, vasculitis, glycocalyx degradation, alterations in blood flow and viscosity, neutrophil extracellular trap formation and microparticle shedding are only few pathomechanisms contributing to endothelial damage and microthrombosis resulting in capillary plugging and tissue ischemia. In the following opinion paper, we discuss major pathological processes leading to microvascular endothelial activation and thrombosis formation as a possible major adverse factor driving the deterioration of patient disease course in severe COVID-19.

Introduction: Patients undergoing acute percutaneous coronary intervention receive dual antiplatelet therapy for secondary prevention. Recurrent myocardial infarction or bleedings are possibly due to under- or overdosing of antiplatelet therapy in relation to body size., Methods: We correlated residual platelet aggregation with body mass index, body surface area, lean body mass and blood volume in 220 patients on prasugrel (n = 121) or ticagrelor (n = 99)., Results: Platelet aggregation outside the recommended window was recorded in 85 patients, but not correlated with any of the body indices., Conclusion: Body size does not affect platelet response to prasugrel or ticagrelor at the guideline-recommended fixed dosages., Competing Interests: Declaration of Competing Interest The authors of this manuscript have nothing to declare., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Cirrhotic patients have an increased risk of bleeding and thromboembolic events, with platelets being involved as key players in both situations. The impact of peripheral versus central blood sampling on platelet activation remains unclear. In 33 cirrhotic patients, we thus analyzed platelet function in peripheral (P) and central (C) blood samples. Platelet surface expression of P -selectin, activated glycoprotein (GP) IIb/IIIa, and leukocyte-platelet aggregate formation were measured by flow cytometry in response to different agonists: thrombin receptor-activating peptide-6, adenosine diphosphate, collagen-related peptide (CrP), epinephrine, AYPGKF, Pam3CSK4, and lipopolysaccharide. Unstimulated platelet surface expression of P -selectin ( p = .850) and activated GPIIb/IIIa ( p = .625) were similar in peripheral and central blood samples. Stimulation with various agonists yielded similar results of platelet surface expression of P -selectin and activated GPIIb/IIIa in peripheral and central samples, except for CrP-inducible expression of activated GPIIb/IIIa (median fluorescence intensity, MFI in P: 7.61 [0.00-24.66] vs. C: 4.12 [0.00-19.04], p < .001). The formation of leukocyte-platelet aggregate was similar in central and peripheral blood samples, both unstimulated and after stimulation with all above-mentioned agonists. In conclusion, peripheral vs. central venous blood sampling does not influence the assessment of platelet activation by flow cytometry in cirrhosis. Abbreviations: ACLD : advanced chronic liver disease; ADP : adenosine diphosphate; ALD : alcoholic liver disease; AYPGKF : PAR-4 agonist AYPGKF; CrP : collagen related protein; EPI : epinephrine; FACS : fluorescence-activated cell sorting; GP : glycoprotein; HVPG : hepatic venous pressure gradient; IQR : interquartile range; LPS : lipopolysaccharide; LSM : liver stiffness measurement; MFI : median fluorescence intensity; NAFLD : nonalcoholic fatty liver disease; PAM : lipopeptide Pam3CSK4; PAR : protease-activated receptor; PBS : phosphate-buffered saline; PH : portal hypertension; TIPS: transjugular intrahepatic portosystemic stent shunt; TLR : toll-like receptor; TRAP-6 : thrombin receptor-activator peptide-6; vWF : von Willebrand factor.

Background: Antiplatelet therapy is a cornerstone in the secondary prevention of ischemic events following percutaneous coronary intervention (PCI). The new P2Y 12 receptor inhibitors prasugrel and ticagrelor have been shown to improve patients' outcomes. Whether or not these drugs have equal efficacy in individuals with or without diabetes is disputed. Furthermore, platelets can be activated by thrombin, which is, at least in part, independent of P2Y 12 -mediated platelet activation. Protease-activated receptor (PAR)-1 and -4 are thrombin receptors on human platelets. We sought to compare the in vitro efficacy of prasugrel (n = 121) and ticagrelor (n = 99) to inhibit PAR-mediated platelet aggregation in individuals with type 2 diabetes (prasugrel n = 26, ticagrelor n = 29)., Materials and Methods: We compared P2Y 12 -, PAR-1- and PAR-4-mediated platelet aggregation as assessed by multiple electrode platelet aggregometry between prasugrel- and ticagrelor-treated patients without and with type 2 diabetes who underwent acute PCI., Results: Overall, there were no differences of P2Y 12 -, PAR-1- and PAR-4-mediated platelet aggregation between prasugrel- and ticagrelor-treated patients. However, both drugs inhibited P2Y 12 -mediated platelet aggregation stronger, and thereby to a similar extent in patients with type 2 diabetes than in those without diabetes. There was no correlation between either P2Y 12 -, or PAR-1- or PAR-4-mediated platelet aggregation and levels of HbA1c or the body mass index (BMI). However, we observed patients with high residual platelet reactivity in response to PAR-1 and PAR-4 stimulation in all cohorts., Conclusion: Prasugrel and ticagrelor inhibit P2Y 12 - and PAR-mediated platelet aggregation in individuals with diabetes to a similar extent, irrespective of HbA 1c levels and BMI., (© 2022 The Authors. Diabetic Medicine published by John Wiley & Sons Ltd on behalf of Diabetes UK.)

Growth differentiation factor (GDF)-15 inhibits platelet activation, prevents thrombus formation, and has been linked to bleeding events. This was a prospective study including 51 left-ventricular assist device (LVAD) patients on aspirin and phenprocoumon. Platelet surface expression of activated glycoprotein (GP) IIb/IIIa was assessed by flow cytometry, and platelet aggregation was measured by multiple electrode aggregometry (MEA) in response to arachidonic acid (AA), adenosine diphosphate (ADP), and thrombin receptor-activating peptide (TRAP), a protease-activated-receptor-1 (PAR-1) agonist. GDF-15 was determined with a commercially-available assay. There was a trend towards an inverse correlation of GDF-15 with activated GPIIb/IIIa in response to TRAP (r = -0.275, p = 0.0532) but not in response to AA and ADP. Moreover, GDF-15 correlated with MEA TRAP (r = -0.326, p = 0.0194), whereas it did not correlate with MEA ADP and MEA AA. In a second step, GDF-15 levels in the fourth quartile were defined as high GDF-15. Patients with high GDF-15 showed significantly lower TRAP-inducible platelet aggregation by MEA compared to patients in the first quartile (63 AU vs. 113 AU, p = 0.0065). In conclusion, in LVAD patients receiving state-of-the-art antithrombotic therapy, GDF-15 correlates inversely with residual platelet reactivity via PAR-1.

Capillary density rarefaction and endothelial dysfunction contribute to chronic hypoperfusion and cerebral small vessel disease. Previous animal experiments revealed spatiotemporal microvascular remodeling directing post-stroke brain reorganization. We hypothesized that microcirculatory changes during acute cerebrovascular events could be reflected systemically and visualized sublingually. In a prospective observational trial in vivo sublingual sidestream darkfield videomicroscopy was performed in twenty-one patients with either acute stroke (n = 13 ischemic, n = 1 ischemic with hemorrhagic transformation and n = 2 hemorrhagic stroke) or transitory ischemic attacks (n = 5) within 24 h after hospital admission and compared to an age- and sex-matched control group. Repetitive measurements were performed on the third day and after one week. Functional and perfused total capillary density was rarefied in the overall patient group (3060 vs 3717 μm/mm 2 , p = 0.001 and 5263 vs 6550 μm/mm 2 , p = 0.002, respectively) and in patients with ischemic strokes (2897 vs. 3717 μm/mm 2 , p < 0.001 and 5263 vs. 6550 μm/mm 2 , p = 0.006, respectively) when compared to healthy controls. The perfused boundary region (PBR), which was measured as an inverse indicator of glycocalyx thickness, was markedly related to red blood cell (RBC) filling percentage (regarded as an estimate of microvessel perfusion) in the overall patient group (r = -0.843, p < 0.001), in patients with ischemic strokes (r = -0.82, p = 0.001) as well as in healthy volunteers (r = -0.845, p < 0.001). In addition, there were significant associations between platelet count or platelet aggregation values (as measured by whole blood impedance aggregometry) and microvascular parameters in the overall patient collective, as well as in patients with ischemic strokes. In conclusion, cerebrovascular events are associated with altered systemic microvascular perfusion., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Left-ventricular assist devices (LVADs) improve outcomes in end-stage heart failure patients. Two centrifugal-flow LVAD systems are currently approved, HeartMate 3 (HM3) and Medtronic/Heartware HVAD (HVAD). Clinical findings suggest differences in thrombogenicity between both systems. We compared markers of platelet activation and aggregation between HM3 and HVAD. We prospectively included 59 LVAD patients (40 HM3, 19 HVAD). Platelet P -selectin expression, activated glycoprotein (GP) IIb/IIIa and monocyte-platelet aggregates (MPA) were assessed by flow-cytometry. Platelet aggregation was measured by light-transmission aggregometry (LTA) and multiple-electrode aggregometry (MEA). Von-Willebrand factor (VWF) antigen (VWF:Ag), VWF activity (VWF:Ac), and VWF multimer pattern analysis were determined. Soluble P -selectin (sP-selectin) was measured with an enzyme-linked immunoassay. P -selectin, GPIIb/IIIa and MPA levels in vivo and in response to arachidonic acid, adenosine diphosphate, and thrombin receptor activating peptide were similar between HM3 and HVAD (all p > .05). Likewise, agonist-inducible platelet aggregation by LTA and MEA did not differ between HM3 and HVAD (all p > .05). VWF:Ag levels and FVIII:C were similar between both systems (both p > .05), but patients with HVAD had significantly lower VWF:Ac ( p = .011) and reduced large VWF multimers ( p = .013). Finally, sP-selectin levels were similar in patients with HVAD and HM3 ( p = .845). In conclusion, on-treatment platelet activation and aggregation are similar in HM3 and HVAD patients. Potential clinical implications of observed differences in VWF profiles between both LVAD systems need to be addressed in future clinical trials.

A high platelet-to-lymphocyte ratio (PLR) has recently been associated with ischemic outcomes in cardiovascular disease. Increased platelet reactivity and leukocyte-platelet aggregate formation are directly involved in the progress of atherosclerosis and have been linked to ischemic events following percutaneous coronary intervention (PCI). In order to understand the relation of PLR with platelet reactivity, we assessed PLR as well as agonist-inducible platelet aggregation and neutrophil-platelet aggregate (NPA) formation in 182 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel (n = 96) or ticagrelor (n = 86) 3 days after PCI. PLR was calculated from the blood count. Platelet aggregation was measured by multiple electrode aggregometry and NPA formation was determined by flow cytometry, both in response to ADP and SFLLRN. A PLR ≥91 was considered as high PLR based on previous data showing an association of this threshold with adverse ischemic outcomes. In the overall cohort and in prasugrel-treated patients, high PLR was associated with higher SFLLRN-inducible platelet aggregation (67 AU [50-85 AU] vs 59.5 AU [44.3-71.3 AU], P = .01, and 73 AU [50-85 AU] vs 61.5 AU [46-69 AU], P = .02, respectively). Further, prasugrel-treated patients with high PLR exhibited higher ADP- (15% [11%-23%] vs 10.9% [7.6%-15.9%], P = .007) and SFLLRN-inducible NPA formation (64.3% [55.4%-73.8%] vs 53.8% [44.1%-70.1%], P = .01) as compared to patients with low PLR. These differences were not seen in ticagrelor-treated patients. In conclusion, high PLR is associated with increased on-treatment platelet reactivity in prasugrel-treated patients, but not in patients on ticagrelor.

Background and Aims: Protease-activated receptor (PAR)-1-mediated platelet activation may vary according to sex and clinical situation. In order to investigate sex-specific platelet activation through PAR-1, we assessed platelet response to thrombin receptor-activating peptide (TRAP) in 562 patients undergoing cardiac catheterization without (Group 1A) and with (Group 1B) acute coronary syndrome (ACS). Subsequently, we sought to confirm our findings in 287 patients undergoing elective (Group 2A) or acute (Group 2B) percutaneous coronary intervention., Methods: TRAP-stimulated platelet surface expression of P-selectin and activated glycoprotein IIb/IIIa (GPIIb/IIIa) were measured by flow cytometry in Group 1. Light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in response to TRAP were assessed in Group 2., Results: In Group 1A, platelet activation in response to TRAP was significantly higher in women compared to men (P-selectin: 511 MFI [443-597 MFI] vs. 471 MFI [393-552 MFI]; GPIIb/IIIa: 84 MFI [58-119 MFI] vs. 70 MFI [47-103 MFI]; both p ≤ 0.002). In contrast, in Group 1B, TRAP-stimulated P-selectin and activated GPIIb/IIIa were similar in men and women (both p ≥ 0.3). Likewise, TRAP-stimulated platelet aggregation was significantly higher in female patients in Group 2A (LTA: 66% [54-76%] vs. 51% [41-65%]; MEA: 78 AU [66-107 AU] vs. 62 AU [52-88 AU]; both p ≤ 0.02), whereas men and women in Group 2 B had similar platelet aggregation (p = 0.5). The occurrence of ischemic endpoints did not differ significantly between men and women in Group 1A and Group 1B., Conclusions: Platelet PAR-1 signaling is more pronounced in women than in men without ACS. In ACS, however, PAR-1-mediated platelet activation is similar in male and female patients., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: In patients with acute coronary syndrome (ACS), angiotensin-converting enzyme (ACE) inhibitors are preferred over angiotensin receptor blockers (ARBs). However, in a recent pilot study, treatment with ACE inhibitors was associated with increased platelet reactivity compared to ARBs. Therefore, we sought to investigate the impact of renin-angiotensin-aldosterone system (RAAS) blockade with ACE inhibitors and ARBs on platelet aggregation in patients with ACS undergoing percutaneous coronary intervention., Methods: On-treatment residual platelet reactivity in response to arachidonic acid (AA), adenosine diphosphate (ADP), SFLLRN, AYPGKF, and collagen was assessed by multiple electrode aggregometry (MEA) in 197 ACS patients on dual antiplatelet therapy (DAPT) with aspirin and either prasugrel or ticagrelor., Results: One hundred sixty-five (83.7%) patients were treated with ACE inhibitors, 32 (16.3%) with ARBs. On-treatment residual AA- and ADP-inducible platelet reactivity was significantly higher in patients with ACE inhibitors (both p < 0.05). Likewise, SFLLRN was significantly higher in patients with ACE inhibitors (p = 0.036) and there was a trend for higher AYPGKF- and collagen-inducible platelet reactivity (p = 0.053 and p = 0.082). The incidence of high on-treatment residual platelet reactivity AA was significantly higher in patients with ACE inhibitors (52 [31.5%] vs. 3 [9.4%] patients; p = 0.019)., Conclusion: ACE inhibitors are associated with increased on-treatment residual platelet reactivity in ACS patients with potent DAPT. Further clinical trials are needed to elucidate the role of RAAS blockade with ACE inhibitors and ARBs in ACS patients treated according to current standards., (© 2020. The Author(s).)

Background:  Monocyte-platelet aggregates (MPAs) are a sensitive marker of in vivo platelet activation in acute coronary syndrome (ACS) and associated with clinical outcomes. MicroRNAs (miRs) play an important role in the regulation of platelet activation, and may influence MPA formation. Both, miRs and MPA, could be influenced by the type of P2Y12 inhibitor., Aim:  To study the association of platelet-related miRs with MPA formation in ACS patients on dual antiplatelet therapy (DAPT), and to compare miRs and MPA levels between prasugrel- and ticagrelor-treated patients., Methods and Results:  We analyzed 10 circulating platelet-related miRs in 160 consecutive ACS patients on DAPT with low-dose aspirin and either prasugrel ( n  = 80) or ticagrelor ( n  = 80). MPA formation was measured by flow cytometry without addition of platelet agonists and after simulation with the toll-like receptor (TLR)-1/2 agonist Pam3CSK4, adenosine diphosphate (ADP), or arachidonic acid (AA). In multivariate regression analyses, we identified miR-21 (β = 9.50, 95% confidence interval [CI]: 1.60-17.40, p  = 0.019) and miR-126 (β = 7.50, 95% CI: 0.55-14.44, p  = 0.035) as independent predictors of increased MPA formation in vivo and after TLR-1/2 stimulation. In contrast, none of the investigated miRs was independently associated with MPA formation after stimulation with ADP or AA. Platelet-related miR expression and MPA formation did not differ significantly between prasugrel- and ticagrelor-treated patients., Conclusion:  Platelet-related miR-21 and miR-126 are associated with MPA formation in ACS patients on DAPT. miRs and MPA levels were similar in prasugrel- and ticagrelor-treated patients., Competing Interests: None declared., (Thieme. All rights reserved.)

Since data on the agreement between light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in patients on the more potent P2Y 12 inhibitors are missing so far, we investigated if the evaluation of the responsiveness to therapy by LTA can be replaced by MEA in 160 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel or ticagrelor (n = 80 each). Cut-off values for high on-treatment residual platelet reactivity (HRPR) in response to adenosine diphosphate (ADP) or arachidonic acid (AA) were defined according to previous studies showing an association of HRPR with the occurrence of adverse ischemic outcomes. ADP- inducible platelet aggregation was 33% and 37% ( P = 0.07) by LTA and 19 AU and 20 AU ( P = 0.38) by MEA in prasugrel- and ticagrelor-treated patients, respectively. AA- inducible platelet aggregation was 2% and 3% by LTA and 15 AU and 16 AU by MEA, (all P ≥ 0.3) in patients on prasugrel and ticagrelor, respectively. By LTA, HRPR ADP and HRPR AA were seen in 5%/5% and in 4%/ 13% of patients receiving prasugrel- and ticagrelor, respectively. By MEA, HRPR ADP and HRPR AA were seen in 3%/ 25% and 0%/24% of prasugrel- and ticagrelor-treated patients, respectively. ADP-inducible platelet reactivity by MEA correlated significantly with LTA ADP in prasugrel-treated patients (r = 0.4, P < 0.001), but not in those receiving ticagrelor (r = 0.09, P = 0.45). AA-inducible platelet aggregation by LTA and MEA did not correlate in prasugrel- and ticagrelor-treated patients. Sensitivity/specificity of HRPR by MEA to detect HRPR by LTA were 25%/99% for MEA ADP and 100%/79% for MEA AA in prasugrel-treated patients, and 0%/100% for MEA ADP and 70%/83% for MEA AA in ticagrelor-treated patients. In conclusion, on-treatment residual ADP-inducible platelet reactivity by LTA and MEA shows a significant correlation in prasugrel- but not ticagrelor-treated patients. However, in both groups LTA and MEA revealed heterogeneous results regarding the classification of patients as responders or non-responders to P2Y 12 inhibition.

Activated platelet-rich plasma (PRP) has been used in the clinical settings of wound healing and regenerative medicine, with activation typically induced by the addition of bovine thrombin. To eliminate issues with availability, cost and potential side effects associated with bovine thrombin, ex vivo PRP activation using pulse electric fields (PEF) has been proposed and demonstrated. The present study characterizes the effect of PEF voltage and pulse width, in combination with a range of calcium concentrations, on clot formation, growth factor release, and serotonin (5-HT) release from dense granules. The main findings are: 1) increasing calcium concentrations with most PEF conditions leads to increased levels of PDGF and 5-HT release; 2) whether EGF levels increase or decrease with increasing calcium concentration depends on the specific PEF parameters; 3) the pattern of PDGF and EGF levels in supernatants suggest that these molecules are localized differently within platelets; 4) significant levels of PDGF, EGF, and 5-HT can be released without inducing clot formation or hemoglobin release. In conclusion, voltage, pulse width and calcium concentration can be used to control and tune the release of growth factors, serotonin and hemoglobin from PEF-activated PRP. Because growth factor requirements vary for different types of wounds and for wounds at different stages of healing, the unique balance of factors in supernatants of PEF-activated PRP may provide more clinically advantageous than the current standard of bovine thrombin-activated PRP., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: A.L. Frelinger and A. D. Michelson received research support from GE Research. B. Neculaes and S. Klopman are employees of GE Research. This does not alter the authors’ adherence to PLOS ONE policies on sharing data and materials. The remaining authors declare no competing interests.