Plasma Fibrinolysis Research Articles

Validation of the time to attain maximal clot amplitude after reaching maximal clot formation velocity parameter as a measure of fibrinolysis using rotational thromboelastometry and its application in the assessment of fibrinolytic resistance in septic patients: a prospective observational study: communication from the ISTH SSC Subcommittee on Fibrinolysis

BackgroundIn sepsis, fibrinolysis resistance correlates with worse outcomes. Practically, rotational thromboelastometry (ROTEM) is used to report residual clot amplitude relative to maximum amplitude at specified times after clot formation clot lysis indices (CLIs). However, healthy individuals can exhibit similar CLIs, thus making it challenging to solely diagnose the low fibrinolytic state. Furthermore, CLI does not include the kinetics of clot formation, which can affect overall fibrinolysis. Therefore, a more nuanced analysis, such as time to attain maximal clot amplitude after reaching maximal clot formation velocity (t-AUCi), is needed to better identify fibrinolysis resistance in sepsis. ObjectivesTo evaluate the correlation between the degree of fibrinolytic activation and t-AUCi in healthy or septic individuals. MethodsWhole blood (n = 60) from septic or healthy donors was analyzed using tissue factor–activated (EXTEM) and nonactivated (NATEM) ROTEM assays. Lysis was initiated with tissue-type plasminogen activator, and CLI and t-AUCi were calculated. Standard coagulation tests and plasma fibrinolysis markers (D-dimer, plasmin-α2-antiplasmin complex, plasminogen activator inhibitor type 1, and plasminogen) were also measured. Resultst-AUCi values decreased with increasing fibrinolytic activity and correlated positively with CLI for different degrees of clot lysis both in EXTEM and NATEM. t-AUCi cutoff value of 1962.0 seconds in EXTEM predicted low fibrinolytic activity with 81.8% sensitivity and 83.7% specificity. In addition, t-AUCi is not influenced by clot retraction. ConclusionWhole-blood point-of-care ROTEM analyses with t-AUCi offers a more rapid and parametric evaluation of fibrinolytic potential compared with CLI, which can be used for a more rapid and accurate diagnosis of fibrinolysis resistance in sepsis.

Atorvastatin downregulates plasma procarboxypeptidase U concentrations and improves fibrinolytic potential dose-dependently in hyperlipidemic individuals

BackgroundStatins efficiently lower cholesterol and also exert pleiotropic effects that extend beyond lipid lowering. In a recent pilot study, valuable information on the carboxypeptidase U (CPU) system in hyperlipidemia and the effect of statin therapy was collected. It was shown that proCPU levels are increased in hyperlipidemic patients. Statins significantly decreased proCPU levels and improved plasma fibrinolysis. Furthermore, it was suggested that patients with high baseline proCPU levels are most likely to benefit from statin therapy. ObjectivesWe aimed to further substantiate the effect of hyperlipidemia and statin therapy on CPU-related parameters in a larger cohort of hyperlipidemic and statin-treated individuals. MethodsBlood was collected from 141 individuals treated with different dosages of atorvastatin (10-80 mg), 38 normolipidemic, and 37 hyperlipidemic controls. Lipid parameters and markers of fibrinolysis (proCPU and clot lysis time) were determined and compared between the groups. ResultsPilot study results of high proCPU concentrations in hyperlipidemic patients and the proCPU-reducing effect of atorvastatin were confirmed. Accordingly, an improvement in plasma fibrinolytic potential was seen under the influence of atorvastatin. High interindividual variation in proCPU concentrations was observed in the hyperlipidemic cohort, with up to 80% higher proCPU levels compared with normolipidemic controls. Furthermore, proCPU concentration and the dosage of atorvastatin were inversely correlated. ConclusionsThis study clearly shows that plasma proCPU concentrations and its expected effect on the fibrinolytic rate (as measured by clot lysis time) are increased in hyperlipidemic patients and that these effects can be normalized (and even further reduced compared with normolipidemic patients) by atorvastatin treatment.

Tissue factor pathway inhibitor is a potential modifier of bleeding risk in factor XI deficiency

BackgroundFactor (F) XI deficiency is associated with increased bleeding risk in some individuals. Neither FXI levels nor clinical clotting assays predict the bleeding risk. Compared with controls, FXI-deficient bleeders have reduced clot formation, decreased fibrin network density, and increased susceptibility to fibrinolysis. Tissue factor pathway inhibitor (TFPI) was recently implicated as a modifying factor in individuals with bleeding of unknown cause. ObjectivesTo determine the potential of TFPI in modifying the bleeding risk in FXI-deficient individuals. MethodsThe effects of TFPI on thrombin generation and clot formation, structure, and fibrinolysis in FXI-deficient plasma were measured in vitro in the absence or presence of inhibitory anti-TFPI antibody or exogenous recombinant TFPIα. Total plasma TFPI concentration was measured in 2 independent cohorts of controls and FXI-deficient individuals classified as bleeders or nonbleeders (cohort 1: 10 controls and 16 FXI-deficient individuals; cohort 2: 48 controls and 57 FXI-deficient individuals) and correlated with ex vivo plasma clot formation and fibrinolysis parameters associated with bleeding risk. ResultsIn an in vitro FXI deficiency model, inhibition of TFPI enhanced thrombin generation and clot formation, increased the network density, and decreased fibrinolysis, whereas an increase in TFPI had the opposite effects. Compared with controls, plasma from FXI-deficient bleeders had higher TFPI concentration. Total plasma TFPI concentrations correlated with parameters from ex vivo clotting and fibrinolysis assays that differentiate FXI-deficient bleeders and nonbleeders. ConclusionCoagulation and fibrinolysis parameters that differentiate FXI-deficient nonbleeders and bleeders were altered by plasma TFPIα. Total plasma TFPI was increased in FXI-deficient bleeders. TFPI may modify the bleeding risk in FXI-deficient individuals.

Platelets and Sera from Donors of Convalescent Plasma after Mild COVID-19 Show No Procoagulant Phenotype.

Coronavirus disease-2019 (COVID-19) is associated with increased thromboembolic complications. Long-term alteration in the coagulation system after acute COVID-19 infection is still a subject of research. Furthermore, the effect of sera from convalescent subjects on platelets is not known. In this study, we investigated platelet phenotype, coagulation, and fibrinolysis in COVID-19 convalescent plasma (CCP) donors and analyzed convalescent sera-induced effects on platelets. We investigated CCP donors who had a history of mild COVID-19 infection and donors who did not have COVID-19 were used as controls. We analyzed phosphatidylserine (PS) externalization, CD62p expression, and glycoprotein VI (GPVI) shedding both in platelet-rich plasma (PRP) and after incubation of washed healthy platelets with donors' sera using flow cytometry. Coagulation and fibrinolysis systems were assessed with thromboelastometry. Forty-seven CCP donors (22 males, 25 females; mean age (±SD): 41.4 ± 13.7 years) with a history of mild COVID-19 infection were included. Median duration after acute COVID-19 infection was 97 days (range, 34-401). We did not find an increased PS externalization, CD62p expression, or GPVI shedding in platelets from CCP donors. Sera from CCP donors did not induce PS externalization or GPVI shedding in healthy platelets. Sera-induced CD62p expression was slightly, albeit statistically significantly, lower in CCP donors than in plasma donors without a history of COVID-19. One patient showed increased maximum clot firmness and prolonged lysis time in thromboelastometry. Our findings suggest that procoagulant platelet phenotype is not present after mild COVID-19. Furthermore, CCP sera do not affect the activation status of platelets.

The balance of comprehensive coagulation and fibrinolytic potential is disrupted in patients with moderate to severe COVID-19.

Coagulation and fibrinolytic mechanisms are enhanced in patients with coronavirus (COVID-19), but disturbances in the balance of both functions in COVID-19 patients remain unclear. We assessed global coagulation and fibrinolysis in plasma from 167 COVID-19 patients (mild/moderate/severe: 62/88/17, respectively) on admission using clot-fibrinolysis waveform analysis (CFWA). Maximum coagulation velocity (|min1|) and maximum fibrinolysis velocity (|FL-min1|) were expressed as ratios relative to normal plasma. Ten patients (6.0%) developed thrombosis, 5 (3.0%) had bleeding tendency, and 13 (7.8%) died during admission. FDP levels increased with severity of COVID-19 symptoms (mild/moderate/severe; median 2.7/4.9/9.9 μg/mL, respectively). The |min1| ratios were elevated in all categories (1.27/1.61/1.58) in keeping with enhanced coagulation potential, with significant differences between mild cases and moderate to severe cases. The |FL-min1| ratios were also elevated in all groups (1.19/1.39/1.40), reflecting enhanced fibrinolytic potential. These data identified coagulation dominance in moderate to severe cases, but balanced coagulation and fibrinolysis in mild cases. There were significant differences in FDP and TAT, but no significant differences in |min1| or |FL-min1| ratios, between patients with and without thrombosis. CFWA monitoring of coagulation and fibrinolysis dynamics could provide valuable data for understanding hemostatic changes and disease status in COVID-19 patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12185-022-03308-w.

Absence of Hyperactivation of Fibrinolysis Explains the Lack of Hemostatic Efficacy of Prophylactic Tranexamic Acid (TXA) in Hypoproliferative Thrombocytopenia

Background: We previously reported the results of the A-TREAT study (American Trial Using Tranexamic Acid in Thrombocytopenia: NCT02578901). This randomized double-blind placebo-controlled trial demonstrated that TXA administration is not superior to placebo in preventing WHO grade 2 or higher bleeding in severely thrombocytopenic patients requiring supportive platelet transfusion following myeloablative therapy for hematologic disorders (Gernsheimer T., ASH 2020 Plenary Session).Here, we present results of the A-TREAT ancillary study - Fibrinolysis Evaluation in A-TREAT (FEAT). Blood samples were collected from a subset (n=115) of A-TREAT participants just prior to initiation of study drug (when the platelet count was <30,000/µl) and at a later time point when TXA was at a steady state trough level (5 ±2 days following study drug initiation). Using global assays of fibrinolysis in plasma, our a priori hypotheses were that: 1] a baseline ‘hyperfibrinolytic’ profile would be associated with a higher proportion of grade 2+ bleeding; and 2] trough TXA levels would be associated with a ‘hypofibrinolytic’ profile and a lower proportion of grade 2+ bleeding.Methods: Fibrinolysis in platelet-free citrated plasma was assessed by 3 global assays: euglobulin clot lysis time (ECLT), plasmin generation (PG), and tPA resistance clot lysis time (tPA-CLT) using previously described methods (Ilich A. RPTH 2020, Miszta A. JTH 2021). Trough plasma TXA concentration was measured using a validated tandem mass spectrometry assay. Individual fibrinolytic analytes (PAI-1, tPA, plasminogen, alpha2-antiplasmin and plasmin-antiplasmin complexes) were quantified by ELISA.Results: Baseline samples did not demonstrate a hyperfibrinolytic profile by ECLT. To the contrary, ECLT values were significantly increased compared to healthy controls (figure 1). Furthermore, none of the measured fibrinolytic parameters (ECLT, tPA-CLT, total PAI-1, tPA, plasminogen, alpha2-antiplasmin or plasmin-antiplasmin complexes) at baseline were associated with a greater risk of grade 2+ bleeding during follow up, regardless of treatment arm. On the follow-up samples, neither pharmacokinetic (trough TXA concentration) nor pharmacodynamic parameters (PG or tPA-CLT) were associated with bleeding severity. A high inter-patient variability of TXA trough concentrations was noted in the treatment arm (min-max: 0.7-10 ug/ml), and drug levels correlated strongly with global fibrinolysis assessment by PG (Spearman r, -0.78, 95% CI -0.88 - -0.62) and tPA-CLT (r, 0.74, 0.56 - 0.85) (figure 2).Conclusions:1] No evidence of fibrinolytic hyperactivation was observed in these thrombocytopenic patients;2] trough TXA concentrations varied significantly between patients receiving the same dosing schedule; and3] tPA-CLT and PG parameters correlated well with TXA plasma concentrations and thus may be used to estimate the extent of fibrinolytic inhibition in patients treated with TXA.Discussion: The absence of hyperactivation of endogenous fibrinolysis in this study is in contrast to our recent findings in trauma. Specifically, we reported that almost half of trauma patients demonstrated evidence of fibrinolytic hyperactivation (by ECLT) on admission (Ilich A. Thromb Res, 2021). Since TXA has been shown to reduce mortality due to bleeding in trauma (CRASH II, Lancet, 2010) and given that baseline hyperfibrinolysis is common in trauma, we hypothesize that the absence of fibrinolytic hyperactivation observed in the A-TREAT study patients likely explains the clinical lack of efficacy of TXA. [Display omitted] DisclosuresGernsheimer: Amgen: Honoraria; Novartis: Honoraria; Principia: Research Funding; Rigel: Research Funding; Cellphire: Consultancy; Dova: Consultancy; Sanofi: Consultancy. Triulzi: Fresenius Kabi: Membership on an entity's Board of Directors or advisory committees; Realta: Membership on an entity's Board of Directors or advisory committees. Wolberg: CSL Behring: Consultancy; Bristol Myers Squibb: Research Funding; Takeda: Research Funding. Key: Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy; Grifols: Research Funding; Uniqure: Consultancy, Other: Participation as a clinical trial investigator.

Aprotinin Inhibits Thrombin Generation by Inhibition of the Intrinsic Pathway, but is not a Direct Thrombin Inhibitor.

Background Aprotinin is a broad-acting serine protease inhibitor that has been clinically used to prevent blood loss during major surgical procedures including cardiac surgery and liver transplantation. The prohemostatic properties of aprotinin likely are related to its antifibrinolytic effects, but other mechanisms including preservation of platelet function have been proposed. Aim Here we assessed effects of aprotinin on various hemostatic pathways in vitro, and compared effects to tranexamic acid(TXA), which is an antifibrinolytic but not a serine protease inhibitor. Methods We used plasma-based clot lysis assays, clotting assays in whole blood, plasma, and using purified proteins, and platelet activation assays to which aprotinin or TXA were added in pharmacological concentrations. Results Aprotinin and TXA dose-dependently inhibited fibrinolysis in plasma. Aprotinin inhibited clot formation and thrombin generation initiated via the intrinsic pathway, but had no effect on reactions initiated by tissue factor. However, in the presence of thrombomodulin, aprotinin enhanced thrombin generation in reactions started by tissue factor. TXA had no effect on coagulation. Aprotinin did not inhibit thrombin, only weakly inhibited the TF-VIIa complex and had no effect on platelet activation and aggregation by various agonists including thrombin. Aprotinin and TXA inhibited plasmin-induced platelet activation. Conclusion Pharmacologically relevant concentrations of aprotinin inhibit coagulation initiated via the intrinsic pathway. The antifibrinolytic activity of aprotinin likely explains the prohemostatic effects of aprotinin during surgical procedures. The anticoagulant properties may be beneficial during surgical procedures in which pathological activation of the intrinsic pathway, for example by extracorporeal circuits, occurs.

Chronic prothrombotic tendency in patients with granulomatosis with polyangiitis.

Patients with granulomatosis with polyangiitis (GPA) show increased tendency toward thromboembolic phenomena in exacerbation of their disease. The aim of the study was to evaluate thrombin generation potential and fibrinolytic plasma activity in patients with GPA, both in exacerbation and in remission. We included 38 patients with GPA: 18 with exacerbated GPA and 20 in remission. The control group included 39 healthy participants matched for age and sex. Plasma thrombogenic potential was assessed using calibrated automated thrombography. Plasma fibrinolytic potential was assessed using clot lysis time (CLT). We also measured levels of inflammatory markers, thrombomodulin, and fibrinolysis proteins in all participants. In the whole group of patients with GPA, endogenous thrombin potential was higher by about 25% (P <0.001), while CLT was lower by about 20% (P = 0.02) when compared with controls. The endogenous thrombin potential was higher, the CLT lower, and the levels of thrombomodulin and inflammation markers (C‑reactive protein, fibrinogen, factor VIII) higher both in patients with exacerbation and in remission than in the control group; no such differences were noted when comparing those with exacerbation and those in remission, however. The only parameter that differentiated patients with GPA exacerbation from those in remission was the D‑dimer level (median [interquartile range], 1151 [597.2-2468.7] ng/ml vs 340.4 [255.1-500.7] ng/ml; P <0.001), a marker of lysis of intravascularly formed fibrin. Patients with GPA show an increased prothrombotic state, regardless of the disease phase. This is probably related to ongoing low-grade inflammation and endothelial injury. Large clinical studies are required to address the need for, and appropriate type of, antithrombotic prophylaxis during the course of GPA.

Euglobulin clot lysis time reveals a high frequency of fibrinolytic activation in trauma

Activation of the fibrinolytic system plays a central role in the host response to trauma. There is significant heterogeneity in the degree of fibrinolysis activation at baseline that is usually assessed by whole blood thromboelastography (TEG). Few studies have focused on plasma markers of fibrinolysis that could add novel insights into the frequency and mechanisms of fibrinolytic activation in trauma. Global fibrinolysis in plasma was assessed using a modified euglobulin clot lysis time (ECLT) assay in 171 major trauma patients and compared to commonly assessed analytes of fibrinolysis. The median ECLT in trauma patients was significantly shorter at 8.5 h (IQR, 1.3–19.5) compared to 19.9 h (9.8–22.6) in healthy controls (p < 0.0001). ECLT values ≤2.5th percentile of the reference range were present in 83 (48.5%) of trauma patients, suggesting increased fibrinolytic activation. Shortened ECLT values were associated with elevated plasmin-antiplasmin (PAP) complexes and free tissue plasminogen activator (tPA) levels in plasma. Sixteen (9.2%) individuals met the primary outcome for massive transfusion, here defined as the critical administration threshold (CAT) of 3 units of packed red cells in any 60-minute period within the first 24 h. In a univariate screen, plasma biomarkers associated with CAT included D-dimer (p < 0.001), PAP (p < 0.05), free tPA (p < 0.05) and ECLT (p < 0.05). We conclude that fibrinolytic activation, measured by ECLT, is present in a high proportion of trauma patients at presentation. The shortened ECLT is partially driven by high tPA levels and is associated with high levels of circulating PAP complexes. Further studies are needed to determine whether ECLT is an independent predictor of trauma outcomes.

Effect of Statin Therapy on the Carboxypeptidase U (CPU, TAFIa, CPB2) System in Patients With Hyperlipidemia: A Proof-of-concept Observational Study

Statins are commonly used in patients with hypercholesterolemia to lower their cholesterol levels and to reduce their cardiovascular risk. There is also considerable evidence that statins possess a range of cholesterol-independent effects, including profibrinolytic properties. This pilot study aimed to explore the influence of statins on procarboxypeptidase U (proCPU) biology and to search for possible effects and associations that can be followed up in a larger study. Blood was collected from 16 patients with hyperlipidemia, before and after 3 months of statin therapy (simvastatin 20 mg or atorvastatin 20 mg). Fifteen age-matched normolipemic persons served as control subjects. Lipid parameters and markers of inflammation and fibrinolysis (proCPU levels and clot lysis times) were determined in all samples. Mean (SD) proCPU levels were significantly higher in patients with hypercholesterolemia compared to control subjects (1186 [189] U/L vs 1061 [60] U/L). Treatment of these patients with a statin led to a significant average decrease of 11.6% in proCPU levels and brought the proCPU concentrations to the same level as in the control subjects. On a functional level, enhancement in plasma fibrinolytic potential was observed in the statin group, with the largest improvement in fibrinolysis seen in patients with the highest baseline proCPU levels and largest proCPU decrease upon statin treatment. Increased proCPU levels are present in patients with hyperlipidemia. Statin treatment significantly decreased proCPU levels and improved plasma fibrinolysis in these patients. Moreover, our study indicates that patients with high baseline proCPU levels are most likely to benefit from statin therapy. The latter should be examined further in a large cohort.

Reduced expression of annexin A2 is associated with impaired cell surface fibrinolysis and venous thromboembolism

AbstractReduced plasma fibrinolysis has been identified as a potential risk factor for venous thromboembolism (VTE), but the role of cell surface fibrinolysis in VTE is unknown. The annexin A2/S100A10 complex serves as a coreceptor for plasminogen and tissue plasminogen activator (tPA), augmenting plasmin generation by 60-fold on the endothelial cell surface. Several studies in both mice and humans support the concept that A2 regulates fibrin homeostasis and intravascular thrombosis in vivo. Here, we examined A2 protein expression and function in 115 adult subjects with VTE and 87 healthy controls. Using peripheral blood mononuclear cells as a surrogate for endothelial cells, we found a 41% mean decrease in cell surface tPA-dependent fibrinolytic activity in subjects who had a positive personal and family history of VTE but tested negative for known inherited thrombophilias (ITs). A2 protein was reduced on average by 70% and messenger RNA levels by 30%, but neither decrease correlated with anticoagulant therapy. Neither cell A2 protein nor cell surface plasmin generation correlated with plasma-based clot lysis times, suggesting that the plasma and cell surface fibrinolytic systems operate independently of one another. These data suggest that reduced expression of annexin A2 protein is associated with cell surface hypofibrinolysis and may represent a novel risk factor for IT.

Plasma fibrinolysis, inflammatory markers, and postthrombotic syndrome: preliminary findings from the Kids-DOTT Biobank.

Plasma levels of markers of coagulation and inflammation have been identified as prognostic factors for adult postthrombotic syndrome (PTS). We aimed to determine whether plasma fibrinolytic capacity and cytokine levels during the first 3 months after provoked deep venous thrombosis (DVT) are associated with risk of PTS in young patients. We analyzed plasma biospecimens (6 weeks and 3 months after provoked DVT) and clinical data from a National Heart, Lung, and Blood Institute-sponsored multinational trial of anticoagulation for provoked venous thromboembolism in patients younger than age 21 years (Kids-DOTT). Patients with a provoked extremity DVT who had plasma samples available at both 6-week and 3-month post-DVT time points and PTS assessment at 1 year were included. We measured plasma fibrinolytic capacity using the Clot Formation and Lysis (CloFAL) assay and plasma cytokine levels by multiplex immunoassay. Logistic regression analyses evaluated prognostic associations with PTS. Seventy-nine patients were included (median age, 12.8 years; range, 0.04-20.8 years). PTS developed in 34%. Complete veno-occlusion at 6 weeks after diagnosis of DVT (odds ratio [OR], 3.12; 95% confidence interval [CI], 0.81-11.94; P = .097), low fibrinolytic capacity in plasma at 3 months post-DVT (OR, 2.71; 95% CI, 0.92-7.97; P = .07), and elevated serum amyloid A at 3 months post-DVT (OR, 2.85; 95% CI, 0.98-8.34; P = .055) were identified as putative prognostic factors for development of PTS. In multivariable logistic regression analysis, these factors did not retain a statistically significant independent association with PTS, but these preliminary results warrant further investigation in an independent data set to definitively evaluate these findings and identify additional potential prognostic factors for the development of PTS after a provoked DVT in young patients.

Prothrombotic changes in patients with COVID‐19 are associated with disease severity and mortality

Background and AimsPatients with severe coronavirus disease 2019 (COVID‐19) are at significant risk of thrombotic complications. However, their prothrombotic state is incompletely understood. Therefore, we measured in vivo activation markers of hemostasis, plasma levels of hemostatic proteins, and functional assays of coagulation and fibrinolysis in plasma from patients with COVID‐19 and determined their association with disease severity and 30‐day mortality. MethodsWe included 102 patients with COVID‐19 receiving various levels of respiratory support admitted to general wards, intermediate units, or intensive care units and collected plasma samples shortly after hospital admission. ResultsPatients with COVID‐19 with higher respiratory support had increased in vivo activation of coagulation and fibrinolysis, as reflected by higher plasma levels of d‐dimer, thrombin‐antithrombin, and plasmin‐antiplasmin complexes as compared to patients with no to minimal respiratory support and healthy controls. Moreover, the patients with COVID‐19 with higher respiratory support exhibited substantial ex vivo thrombin generation and lower ex vivo fibrinolytic capacity, despite higher doses of anticoagulant therapy compared to less severely ill patients. Fibrinogen, factor VIII, and von Willebrand factor levels increased, and ADAMTS13 levels decreased with increasing respiratory support in patients with COVID‐19. Low platelet count; low levels of prothrombin, antithrombin, and ADAMTS13; and high levels of von Willebrand factor were associated with short‐term mortality. ConclusionsSevere COVID‐19 is associated with prothrombotic changes with increased in vivo activation of coagulation and fibrinolysis, despite anticoagulant therapy.

Correlation between plasma clot properties, thrombin generation and whole blood fibrinolytic assays in patients presenting with STEMI

Abstract Background Impaired endogenous fibrinolysis is a novel risk factor for recurrent adverse cardiovascular events in acute coronary syndrome (ACS) patients. This is independent of conventional cardiovascular risk factors and unaffected by dual antiplatelet therapy (DAPT). The mechanism underlying impaired endogenous fibrinolysis in ACS patients is currently unclear. Aim To identify the relationship between whole blood fibrinolysis, plasma fibrinolysis and thrombin generation in samples from STEMI patients. Methods In a large, prospective, observational study of 500 patients presenting with ST-segment elevation myocardial infarction (STEMI), blood samples were taken on arrival, after DAPT loading, and before administration of heparin or PPCI. Non-anticoagulated venous whole blood was analysed using the point-of-care Global Thrombosis Test, which assesses the time taken for occlusive thrombus formation under high shear (occlusion time, OT) and time required for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time, LT). Patients were divided into 4 groups based on quartiles (Q) of whole blood LT (Q1: LT&amp;lt;1500s, Q2:1501–3000s, Q3:3001–4500s, Q4:&amp;gt;4500s). Plasma samples (20 per quartile) were examined in a thrombin generation assay using 1pM tissue factor to initiate and using a turbidity assay to determine the plasma clot lysis time (CLT). Results Clinical characteristics of patients were similar in the four groups. The whole blood LT in the 4 groups were Q1: 1194 (1125–1329) s, Q2: 1859 (1634–2157) s, Q3: 3638 (3252–3962) s, Q4: 6000 (5523–6000) s. As LT increased, there was a trend towards longer plasma CLT (50% CLT Q2: 88.5 [73.5–102] vs. Q4: 100 [85–128.5] min, p=0.088). As a continuous variable, there was no significant relationship between whole blood LT and plasma CLT, or between endogenous thrombin potential (ETP) and either whole blood LT or plasma CLT. There was a significant negative correlation between OT and velocity index (r=−0.425, p=0.0138), ETP (r=−0.519, p=0.002), peak thrombin generation (r=−0.390, p=0.0247) and a positive correlation with lag-time (r=0.427, p=0.013). There was positive correlation between CLT and white cell count (WCC, r=0.388, p=0.026), C-reactive protein (CRP, r=0.477, p=0.005) and maximum absorbance (MA, r=0.530, p=0.002). MA correlated with WCC (r=0.436, p=0.011) and platelet count (r=0.357, p=0.042). There was a negative correlation between OT and WCC (r=−0.537, p=0.001) and CRP (r=−0.381, p=0.029). Conclusion In patients with STEMI, increased platelet reactivity (shorter OT) correlated with increased thrombin generation (higher ETP, peak thrombin generation, velocity index and reduced lag time), demonstrating the key role of thrombin in occlusive thrombus formation. Fibrinolysis in whole blood was poorly related to plasma CLT or thrombin generation, suggesting that cellular components such as platelets, erythrocytes and neutrophil extracellular traps may significantly influence endogenous fibrinolysis. Funding Acknowledgement Type of funding source: None

Distress symptoms development after a single episode of ultrasound exposure

Aim. To study the influence of a single 24-hour episode of exposure to ultrasound waves propagating in air on microcirculation and parameters of hemostasis in rats.&#x0D; Methods. The study was performed on 28 Wistar male rats. The experimental group was exposed to ultrasound for 24 hours. Geometric mean frequency was 25 kHz, acoustic pressure was 84.3 dB. Parameters of microcirculation of experimental rats received by laser Doppler flowmetry were compared with those of intact animals. Also comparative analysis of platelet and coagulation hemostasis, anticoagulant and fibrinolytic plasma activity was performed in rats from both groups.&#x0D; Results. In experimental rats in response to 24-hour exposure to ultrasound, significant decrease of the studied active and passive factors of blood flow modulation occurred compared to those of intact animals: parameters of microcirculation, flax, endothelial and vasomotor wave amplitude, respiratory and pulse wave amplitude. When studying the parameters of hemostasis, significant hypercoagulation of extrinsic pathway and at the latest stages of coagulation which worsened with anticoagulant plasma activity inhibition along with decrease of fibrinolytic activity. The character of changes of hemostatic parameters confirmed the development of stress-reaction in rats registered during the study of microcirculation.&#x0D; Conclusion. 24-hour ultrasound exposure causes significant disorders of microcirculation and unfavorable shifts in hemostasis - the signs of distress.

INFLUENCE OF HEPARINOID FROM PAEONIA LACTIFLORA ON HEMOSTATIC SYSTEM WITHIN CONDITIONS OF PRETHROMBOSIS

The search and development of direct and rapid anticoagulants used per os, is an urgent problem in physiological and medical science. A number of plants contain heparin-like components with a positive effect on the hemostatic system, both within normal and in some pathological conditions of the body.The aim of the work was to study the complex effect of fibrin, a heparin-like substance (heparinoid) from the roots of Paeonia lactiflora, on fibrinolytic, anticoagulant systems of the body and polymerization processes, when it is administered per os in animals within normal conditions and when modeling the state of prethrombosis.Materials and methods. To carry out the research, the roots of Paeonia lactiflora growing in the Botanical Garden of Moscow State University, and laboratory animals – male Wistar rats – were used. To study the antithrombotic effects of the extract from roots containing heparinoid, the state of prethrombosis was modeled in rats. The determined parameters of hemostasis were: anticoagulant activity according to the tests of activated partial thromboplastin time and thrombin time, fibrinolytic activity according to the test of total fibrinolytic activity, fibrin polymerization according to the test of fibrindepolymerization activity of blood plasma.Results. With repeated (every 24 hours within 3 days) oral administration of the extract containing heparinoid, in animals within normal conditions and with prethrombosis, the following anticoagulant effects were established in the blood: an increase in anticoagulant, fibrindepolymerization and fibrinolytic plasma activity. Possible mechanisms of the activating effect of heparinoid on fibrinolysis and anticoagulant properties of plasma due to the excretion of tissue plasminogen activator into the bloodstream from the endothelium, thrombin inhibition, and fibrin polymerization are described. Moreover, the anticoagulant effect of the use of the extract from the peony roots was equivalent to that of the reference drug of low molecular weight heparin from Celsus (USA). For the first time, it was revealed that when modeling experimental prethrombosis, the administration of heparinoid in rats at the dose of 37.5 IU/kg МЕ/кг body weight restored impaired hemostasis, which requires a further study.Conclusion. The ability of heparinoid from peony roots to normalize the functional state of the anticoagulant system during the development of prethrombosis in animals has been established. The restriction of fibrin polymerization during oral administration of heparinoid from peony in animals by increasing the enzymatic fibrinolytic and fibrindepolymerization activity of blood plasma was revealed. In the future, heparinoid can be used as an antithrombotic agent.

Carbon monoxide releasing molecule enhances coagulation and decreases fibrinolysis in canine plasma exposed to Crotalus viridis venom in vitro and in vivo.

Carbon monoxide releasing molecule-2 (CORM-2), an emerging therapeutic in human medicine, enhances plasmatic coagulation and attenuates fibrinolysis in vitro in human, rabbit and horse plasma and ameliorates hypocoagulation and hyperfibrinolysis secondary to venom exposure in human plasma in vitro. Fibrinogenases in rattlesnake venom cause decreased clot strength, and in the presence of tissue plasminogen activator (tPA) in vitro, a markedly increased rate of clot lysis. CO interacts with a haem group on fibrinogen, changing its configuration so that the fibrin clot is strengthened and more resistant to fibrinolysis. We hypothesized that CORM-2 enhances coagulation and attenuates fibrinolysis in canine plasma exposed to Cviridis venom. We measured the effects of Cviridis venom on clot strength, rates of coagulation and fibrinolysis in both pooled canine plasma and plasma from individual naturally envenomed dogs, with and without CORM-2, using thromboelastography (TEG). We tested venom effects on coagulation using tissue factor (TF) activated TEG and on both coagulation and fibrinolysis using TF-activated TEG with added tPA. We found that 17.9µg/mL of venom causes a mean 26.4% decrease in clot strength, a 61.8% decrease in maximum rate of thrombus generation, 75% faster clot lysis, a 226% increase in maximum rate of lysis and a 92% decrease in total clot life span (CLS). CORM-2 ameliorated these effects, increasing CLS in the presence of venom by 603%. Additionally, we showed that CORM-2 has similar effects in vitro on plasma from naturally envenomed dogs, showing promise as an adjunct therapy for snake envenomation.

Разработка и апробация нового метода определения параметров гемостаза у больных с психической патологией

Introduction: hemostasis is one of the most important protective systems of the organism, and its deviations from the norm can lead to fatal results. Changes in hemostasis are observed in many diseases, including mental pathology. In addition, parameters of this system may also change during antipsychotic therapy. Objective: Development and testing of a new method and device for estimating plasma hemostasis parameters in patients with mental pathologies in order to optimize treatment and eliminate fatal outcomes. Materials and methods: in the study we used frozen (-80 °C) platelet-free blood plasma (PFP) samples from patients with schizophrenia (16 patients), taken at admission to the clinic FSBSI «Mental Health Research Centre». Plasma coagulation of patients and healthy donors was assessed with the device of our design. Hemostasis assessment is based on the determination of the clot size in proportion to the brightness of the image, which changes as a result of clot formation and lysis. Results: optimal concentrations of coagulation and fibrinolysis activators, as well as concentrations of calcium ions were determined during the first stage of testing the method and device. The median values of all parameters of coagulation and fibrinolysis except «time before the formation of a clot» in patients upon admission to the clinic were reduced relative with combined plasma donors. The rates of clot formation and lysis in patients are significantly reduced at discharge compared with these parameters at admission. Consequently, these parameters can serve as an estimate of the change in the state of the coagulation and fibrinolysis systems during treatment. Conclusion: during approbation of the device and method in the process of coagulation and fibrinolysis research in patients with schizophrenia, lower levels of parameters were detected compared to donors, and a decrease in the activity of plasma coagulation and fibrinolysis during treatment with antipsychotics was shown.

Highly Potent and Selective Plasmin Inhibitors Based on the Sunflower Trypsin Inhibitor-1 Scaffold Attenuate Fibrinolysis in Plasma.

Antifibrinolytic drugs provide important pharmacological interventions to reduce morbidity and mortality from excessive bleeding during surgery and after trauma. Current drugs used for inhibiting the dissolution of fibrin, the main structural component of blood clots, are associated with adverse events due to lack of potency, high doses, and nonselective inhibition mechanisms. These drawbacks warrant the development of a new generation of highly potent and selective fibrinolysis inhibitors. Here, we use the 14-amino acid backbone-cyclic sunflower trypsin inhibitor-1 scaffold to design a highly potent ( Ki = 0.05 nM) inhibitor of the primary serine protease in fibrinolysis, plasmin. This compound displays a million-fold selectivity over other serine proteases in blood, inhibits fibrinolysis in plasma more effectively than the gold-standard therapeutic inhibitor aprotinin, and is a promising candidate for development of highly specific fibrinolysis inhibitors with reduced side effects.

Assessment and determinants of whole blood and plasma fibrinolysis in patients with mild bleeding symptoms

Enhanced clot lysis is associated with bleeding, but assessment of lysis capacity remains difficult. The plasma turbidity lysis and whole blood tissue Plasminogen Activator-Rotational Thromboelastometry (tPA-ROTEM) assays estimate fibrinolysis under more physiological conditions than clinically used assays. We hypothesized that these assays could find signs of enhanced lysis capacity in patients who report bleeding symptoms, but are not diagnosed with bleeding disorders. We also aimed to gain insight in determinants of the results of these lysis assays. Data from 240 patients with and 95 patients without self-reported bleeding symptoms were obtained, who were included in a study that primarily aimed to assess prevalence of haemostatic abnormalities in preoperative patients. ROTEM and turbidity assays were performed with rtPA. Blood counts, fibrinolysis and coagulation factor activities were determined. Data were analysed using multivariable linear regression models. Remarkably, patients reporting bleeding symptoms showed signs of significantly impaired lysis capacity in the tPA-ROTEM, but not in the turbidity lysis assay. In these patients, the tPA-ROTEM results depended on FII, FXII, plasminogen, α2-antiplasmin, PAI-1 and TAFI levels. The turbidity lysis results were significantly influenced by fibrinogen, α2-antiplasmin, PAI-1 and TAFI. In conclusion, the tPA-ROTEM and the turbidity lysis assay could not detect enhanced fibrinolytic capacity in patients with bleeding symptoms. This suggests that these symptoms are not caused by enhanced fibrinolytic activity. As both assays were sensitive to important determinants of fibrinolysis they may be able to detect a fibrinolytic imbalance, but this needs to be validated in patients with known hypo- or hyperfibrinolytic disorders.