Lecanemab blocks the effects of the Aß/fibrinogen complex on blood clots and synapse toxicity in organotypic culture.

Proteinaceous brain inclusions, neuroinflammation, and vascular dysfunction are common pathologies in Alzheimer's disease (AD). Vascular deficits include a compromised blood-brain barrier, which can lead to extravasation of blood proteins like fibrinogen into the brain. Fibrinogen's interaction with the amyloid-beta (Aß) peptide is known to worsen thrombotic and cerebrovascular pathways in AD. Lecanemab, an FDA-approved antibody therapy for AD, clears Aß plaque from the brain and slows cognitive decline. Here, we show that lecanemab blocks fibrinogen's binding to Aß protofibrils, preventing Aß/fibrinogen-mediated delayed fibrinolysis and clot abnormalities in vitro and in human plasma. Additionally, we show that lecanemab dissociates the Aß/fibrinogen complex and prevents fibrinogen from exacerbating Aß-induced synaptotoxicity in mouse organotypic hippocampal cultures. These findings reveal a possible protective mechanism by which lecanemab may slow disease progression in AD.

Establishment and verification of a prognostic model based on coagulation and fibrinolysis-related genes in hepatocellular carcinoma.

BACKGROUND: Studies have shown that coagulation and fibrinolysis (CFR) are correlated with Hepatocellular carcinoma (HCC) progression and prognosis. We aim to build a model based on CFR-correlated genes for risk assessment and prediction of HCC patient. METHODS: HCC samples were selected from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases respectively. The Molecular Signatures Database (MSigDB) was used to select the CFR genes. RiskScore model were established by single sample gene set enrichment analysis (ssGSEA), weighted correlation network analysis (WGCNA), multivariate Cox regression analysis, LASSO regression analysis. RESULTS: PCDH17, PGF, PDE2A, FAM110D, FSCN1, FBLN5 were selected as the key genes and designed a RiskScore model. Those key genes were Differential expressions in HCC cell and patients. Overexpression PDE2A inhibited HCC cell migration and invasion. The higher the RiskScore, the lower the probability of survival. The model has high AUC values in the first, third and fifth year prediction curves, indicating that the model has strong prediction performance. The difference analysis of clinicopathological features found that a great proportion of high clinicopathological grade samples showed higher RiskScore. RiskScore were positively correlated with immune scores and TIDE scores. High levels of immune checkpoints and immunomodulators were observed in high RiskScore group. High RiskScore groups may benefit greatly from taking traditional chemotherapy drugs. CONCLUSIONS: We screened CFR related genes to design a RiskScore model, which could accurately evaluate the prognosis and survival status of HCC patients, providing certain value for optimizing the clinical treatment of cancer in the future.

The natural anticoagulant protein S; hemostatic functions and deficiency.

Protein S (PS) is a vital endogenous anticoagulant. It plays a crucial role in regulating coagulation by acting as a cofactor for the activated protein C (APC) and tissue factor pathway inhibitor (TFPI) pathways. Additionally, it possesses direct anticoagulant properties by impeding the intrinsic tenase and prothrombinase complexes. Protein S oversees the coagulation process in both the initiation and propagation stages through these roles. The significance of protein S in regulating blood clotting can be inferred from the significant correlation between deficits in protein S and an elevated susceptibility to venous thrombosis. This is likely because activated protein C and tissue factor pathway inhibitor exhibit low efficacy as anticoagulants when no cofactors exist. The precise biochemical mechanisms underlying the roles of protein S cofactors have yet to be fully elucidated. Nevertheless, recent scientific breakthroughs have significantly enhanced comprehension findings for these functions. The diagnosis of protein S deficiency, both from a technical and genetic standpoint, is still a subject of debate due to the complex structural characteristics of the condition. This paper will provide an in-depth review of the molecular structure of protein S and its hemostatic effects. Furthermore, we shall address the insufficiency of protein S and its methods of diagnosis and treatment.

What is the purpose of this summary? To provide an in-depth review of the molecular structure of protein S and its hemostatic effects.To address the deficiency of protein S and its methods of diagnosis and treatment.What is known? Protein S operates as an anticoagulant through its roles as a cofactor for APC, TFPI, and an inhibitor of FIXa.Protein S deficiency can be either inherited or acquired.What is new? Plasma protein S and platelet-derived protein S contribute to regulating coagulation and maintaining hemostasis. Protein S can be used as a potential promising treatment target for persons diagnosed with hemophilia.

A role of methionines in the functioning of oxidatively modified fibrinogen.

Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/-OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/-OCl, 10 µM HOCl/-OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BßMet367, γMet264, and γMet94, identified in 10 µM HOCl/-OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress.

Hemostatic Effects of Exercise-Related Hypoglycemia in Male Persons With Type 1 Diabetes.

CONTEXT: People with type 1 diabetes (T1D) are at increased risk of thrombosis, however, the underlying mechanisms remain unclear. Hypoglycemia induced at rest can induce coagulation activation, but little is known about the hemostatic effects of exercise-related hypoglycemia in people with T1D. OBJECTIVE: We compared hemostatic profiles of individuals with T1D with healthy controls and explored hemostatic effects of hypoglycemia, induced with or without exercise, in participants with T1D. METHODS: Thrombelastography (TEG) was used for a baseline hemostatic comparison between fifteen men with T1D and matched healthy controls. In addition, the participants with T1D underwent two euglycemic-hypoglycemic clamp days in a randomized, crossover fashion. Hypoglycemia was induced with the participants at rest (Hypo-rest) or during exercise (Hypo-exercise). TEG provides data on the rate of coagulation activation (R-time), the rate of clot formation (K-time, α-Angle), the maximum clot amplitude (MA), the functional fibrinogen contribution to the clot strength (MA-FF) and the fibrinolysis (LY-30). RESULTS: The T1D group exhibited shorter R-time and K-time and a greater α-Angle compared to the controls. During the clamp experiments, Hypo-exercise induced an increased clot strength (MA) with a mean difference from baseline of 2.77 mm [95% confidence interval 2.04; 3.51] accompanied with a decreased fibrinolysis (LY-30) of -0.45 percentage points [-0.60; -0.29]. Hypo-rest resulted in increased functional fibrinogen (MA-FF) of 0.74 mm [0.13; 1.36] along with an increased fibrinolysis (LY-30) of 0.54 percentage points [0.11; 0.98]. CONCLUSION: Individuals with T1D exhibit a hypercoagulable hemostatic profile compared to healthy controls and exercise-related hypoglycemia may increase the susceptibility to thrombosis via both procoagulant and antifibrinolytic effects.

Impaired fibrinolysis in patients with atrial fibrillation and elevated circulating lipopolysaccharide.

It is unknown whether elevated gut-derived serum lipopolysaccharide (LPS) can affect thrombin generation, fibrinolysis, and fibrin clot properties in atrial fibrillation (AF). We aimed to evaluate associations of circulating LPS with prothrombotic markers in AF patients. A total of 157 (women, 57.3%) ambulatory anticoagulant-naïve AF patients aged from 42 to 86 years were recruited. Clinical data together with serum LPS, inflammation, endothelial injury, coagulation and fibrinolysis markers, including fibrin clot permeability (Ks) and clot lysis time (CLT), were analyzed. A median LPS concentration was 73.0 (58.0-100.0) pg/mL and it showed association with CLT (r = 0.31, p < 0.001) and plasminogen activator inhibitor-1 (PAI-1, r = 0.57, p < 0.001), but not other fibrinolysis proteins, thrombin generation, inflammatory markers, or Ks. There were weak associations of LPS with von Willebrand factor (vWF, r = 0.2, p = 0.013), cardiac troponin I (r = 0.16, p = 0.045), and growth differentiation factor-15 (r = 0.27, p < 0.001). No associations of LPS and CHA2DS2-VASc or other clinical variables were observed. Multivariable regression adjusted for potential confounders showed that serum LPS ≥ 100 pg/mL was an independent predictor of prolonged CLT. This study is the first to demonstrate antifibrinolytic effects of elevated LPS in AF patients largely driven by enhanced PAI-1 release.

In vitro effect of hydroxyethyl starch on COVID-19 patients-associated hypofibrinolytic state.

Background: Despite systematic thromboprophylaxis, 30% of the COVID-19 patients in intensive care units develop thrombosis. This occurrence is associated with a hypofibrinolytic state measured by thromboelastometry when adding tissue plasminogen activator (tPA) to citrated whole blood for a further run for EXTEM (ROTEM). Objectives: Because hydroxyethyl starches (HESs) affect fibrin polymerization, we have assessed its potential effect on in vitro tPA-induced fibrinolysis. Methods: Fifteen successive COVID-19 patients from the local intensive care units were selected for tPA resistance occurrence. HES was added to whole blood samples with proportion similar to the pharmacologic recommendations. Samples were run for EXTEM on a ROTEM delta device after further addition of tPA. Paired controls were whole blood samples with the same volume of saline added. To assess the impact of HES on coagulation, thrombin generation was measured in 10 COVID-19 patients in the presence of either HES or saline; then, the clots obtained were used to generate electron microscope images. Results: Clot firmness at 5 minutes and the lysis index at 30 minutes were decreased in presence of HES compared with saline (Wilcoxon test, P < .01 for HES vs saline and HES vs untreated). However, no statistically significant difference was observed for all thrombin generation assay parameters studied (endogenous thrombin potential, peak thrombin, and time to peak). With HES, fibrin fibers of either COVID-19 patients or control subjects were thicker than those of saline-treated samples. Conclusion: These results highlight that HES increased apparent in vitro tPA-induced fibrinolysis in case of severe COVID-19 disease. Use of this plasma volume expander may translate as a potential help against COVID-19-induced thrombosis occurrence.

A Case of Consumptive Coagulopathy Before Cardiopulmonary Failure in Amniotic Fluid Embolism and Review of Literature: A Perspective of the Latent Onset and Progression of Coagulopathy.

Amniotic fluid embolism (AFE) induces cardiopulmonary insufficiency with consumptive coagulopathy. Previous studies reported that refractory coagulopathy has already advanced at the onset of maternal cardiovascular and/or respiratory symptoms. However, when the consumption of coagulation factors starts during the clinical course, AFE remains to be elucidated. We report an intrapartum AFE case of consumptive coagulopathy before dyspnea with hypotension developing during urgent cesarean delivery that was revealed by non-reassuring fetal heart rate tracing. The patient, a 42-year-old multiparous parturient, underwent induced labor after a premature rupture of membranes in week 39 of pregnancy. Coagulation screening was initially within the normal range. Fetal heart rate monitoring demonstrated bradycardia coincided with uterine tachysystole after three hours, which required urgent cesarean section with preoperative blood screening. The hemoglobin level was maintained at 129 g/L; however, the fibrinogen value reduced to 1.79 g/L with D-dimer elevation over 60 µg/mL. Ninety minutes later, she developed dyspnea with hypotension at suturing hysterotomy. At the end of surgery, her fibrinogen further decreased to below 0.3 g/L with prolonged prothrombin time. After vigorous intensive care, she was discharged without sequelae. Consumptive coagulopathy may initiate and progress before apparent cardiopulmonary symptoms in some AFE cases. Non-reassuring fetal heart rate tracing concomitant with abrupt uterine tachysystole and/or hypertonus may be an earlier time point for the detection and intervention of AFE-related coagulopathy.

Spontaneous coronary artery dissection: A review of medical management approaches.

Spontaneous coronary artery dissection (SCAD) is an underdiagnosed cause of acute coronary syndrome (ACS) that usually presents in young female patients. Risk factors include female sex, physical and emotional stressors, and fibromuscular dysplasia, and diagnosis is usually made by coronary angiography aided by intravascular ultrasound (IVUS) or optical coherence tomography (OCT). While conservative treatment is usually preferred over percutaneous coronary intervention or surgery, medical management of SCAD has been under debate. This comprehensive review aims to summarize findings from recent studies exploring various medical treatment approaches for the management of SCAD. Antiplatelet therapy with aspirin is generally safe and beneficial for SCAD patients, with dual antiplatelet (DAPT) being recommended for patients undergoing PCI. In the absence of intervention, DAPT may be given for a short period followed by a longer single-antiplatelet (SAPT) therapy with aspirin. Beta-blockers appear to be safe and effective for SCAD patients. On the other hand, fibrinolytics, anticoagulants, and glycoprotein IIa/IIIb inhibitors are contraindicated. Cardiovascular medications such as renin-angiotensin-aldosterone system (RAAS) inhibitors, mineralocorticoid receptor antagonists, and statins are not recommended in the absence of left ventricular dysfunction. Hormonal therapy is contraindicated for patients who develop SCAD during pregnancy and future pregnancy is discouraged in that patient population.

Benefit of intrapleural fibrinolytic therapy in the treatment of complicated parapneumonic effusion and empyema.

Our study aimed to assess the benefit of intrapleural fibrinolysis before resorting to surgery to treat complicated parapneumonic effusion and empyema. We conducted a retrospective and descriptive study, including all patients hospitalized in the intensive care unit (ICU) of the Abderhaman Mami hospital, Tunisia for empyema treated with instillation of intrapleural fibrinolytic therapy between the 1st January 2000 and 31st December 2016. In all patients, empyema was diagnosed on clinical features, imaging findings (chest X-ray, thoracic echography and/or computed tomography (CT), and microbiological data. The fibrinolytic agent used was streptokinase. The efficiency of intrapleural fibrinolytic therapy was judged on clinical and paraclinical results. Among 103 cases of complicated parapneumonic effusion and empyema, 34 patients were included. The mean age was 34 years [15-81] with a male predominance (sex ratio at 2.77). Median APACH II score was 9. Fifty (50%) of the patients (n=17) had no past medical history; addictive behavior was described in 17 patients (50%). All patients were admitted for acute respiratory failure and one patient for septic shock. Pleural effusion was bilateral in 7 patients. Bacteria isolated were Streptococcus pneumonia (6 cases), Staphylococcus aureus (3 cases, including one which methicillin-resistant), Staphylococcus epidermidis (1 case), anaerobes (5 cases), and Klebsiella pneumoniae (1 case). First-line antimicrobial drug therapy was amoxicillin-clavulanate in 20 patients. A chest drain was placed in all cases in the first 38 hours of ICU admission. The median number of fibrinolysis sessions was 4 [2-9] and the median term of drainage was 7 days [3-16]. No side effects were observed. Video-assisted thoracoscopic surgery was proposed in 5 patients. The median length of hospitalization stay was 15 days [6-31]. One patient died due to multi-organ failure.

Potential Mechanism of Platelet GPIIb/IIIa and Fibrinogen on Retinal Vein Occlusion.

PURPOSE: To explore the role of coagulation and fibrinolytic factors, and the potential mechanism of platelet aggregation in the pathogenesis of retinal vein occlusion. METHODS: Coagulation and fibrinolytic parameters in patients with retinal vein occlusion were determined using hemagglutinin and HISCL-5000. Relationships between these elevated parameters and factors representing typical clinical manifestations of retinal vein occlusion were examined, and these parameters were analyzed using a STRING database to indicate the potential role of platelet aggregation. Platelet glycoprotein IIb/IIIa (GPIIb/IIIa) levels were evaluated by flow cytometry after antiplatelet treatment in patients and mouse models. Furthermore, the GPIIb/IIIa ligand fibrinogen in peripheral blood and retina of mouse models was assessed by the turbidimetric method and real-time PCR, respectively. RESULTS: In patients, significant increases in peripheral blood fibrinogen and GPIIb/IIIa levels were observed (p = 0.0040, p < 0.0001, respectively). A positive correlation was observed between macular thickness (MT) and both fibrinogen and GPIIb/IIIa (r = 0.4528, p = 0.0063; r = 0.3789, p = 0.0427, respectively). After intravitreal injections of anti-vascular endothelial growth factor drugs, a significant reduction in fibrinogen levels was observed (p = 0.0072). In addition, the use of antiplatelet drugs resulted in a significant decrease in GPIIb/IIIa (p < 0.0001). In a mouse model, antiplatelet therapy significantly reduced both peripheral blood and retina fibrinogen levels and the overall rate of vein occlusion 3 days after occlusion (p < 0.0005). In addition, the reduction in GPIIb/IIIa levels after antiplatelet therapy was remarkable. CONCLUSION: Fibrinogen and GPIIb/IIIa may be involved in retinal vein occlusion and blocking platelet aggregation may be a new therapeutic approach for retinal vein occlusion.

Spontaneous reperfusion in STEMI: Its mechanisms and possible modulation.

Patients with transient ST-segment elevation myocardial infarction or spontaneous reperfusion, which occurs in approximately 20% of patients with ST-segment elevation myocardial infarction (STEMI), have smaller infarcts and more favourable clinical outcomes than patients without spontaneous reperfusion. Understanding the mechanisms underlying spontaneous reperfusion is therefore important, since this may identify possible novel therapeutic targets to improve outcomes in patients with STEMI. In this review, we discuss some of the possible determinants of spontaneous reperfusion including pro-thrombotic profile, endogenous fibrinolytic status, lipoprotein(a) (Lp(a)), inflammatory markers and neutrophil extracellular traps (NETs). Effective (rapid) endogenous fibrinolysis, as assessed in whole blood in vitro, using a point-of-care technique assessment of global thrombotic status, has been strongly linked to spontaneous reperfusion. Lp(a), which has a high degree of homology to plasminogen, may impair fibrinolysis through competitive inhibition of tissue plasminogen activator-mediated plasminogen activation as well as tissue plasminogen activator-mediated clot lysis and contributing to pathogenic clot properties by decreasing fibrin clot permeation. NETs appear to negatively modulate clot lysis by increasing thrombin fibre diameter and inhibiting plasmin-driven lysis of plasma clots. There are limited data that oral anticoagulation may modulate endogenous fibrinolysis but antiplatelet agents currently appear to have no impact. Phase III trials involving subcutaneous P2Y12 or glycoprotein IIb/IIIa inhibitors, oral factor XIa inhibitors, interleukin-6 inhibitors, and apolipoprotein(a) antisense oligonucleotides in patients with cardiovascular disease are ongoing. Future studies will be needed to determine the impact of these novel antithrombotic, anti-inflammatory and lipid lowering therapies on endogenous fibrinolysis and spontaneous reperfusion.

Thrombin activatable fibrinolysis inhibitor plasma levels and TAFI Thr325Ile genetic polymorphism in a cohort of Egyptian sickle cell disease patients and impact on disease severity.

BACKGROUND: Thrombin is a critical protease modulating thrombosis as well as inflammation, which are one of the main pathophysiological mechanisms in sickle vasculopathy, and its levels were reported to be high in sickle cell disease (SCD). The thrombin-thrombomodulin complex activates the TAFI inhibitor of fibrinolysis, which acts by reducing plasmin affinity for its substrate thus hindering fibrinolysis. OBJECTIVE: We aimed to determine the influence of the Thr325Ile single nucleotide polymorphism (SNP) on TAFI antigen levels and potential effects on the severity of SCD in a cohort of Egyptian patients. METHODS: Genotyping of Thr325lle polymorphism using Taq-Man SNP genotyping assay and TAFI level measurement using an enzyme-linked immunosorbent assay were performed for 80 SCD patients (45 homozygous HbSS, 16 S/ß0 and 19 Sß+) as well as 80 age- and gender-matched healthy control subjects. RESULTS: Plasma TAFI levels were higher in SCD patients with Thr325Ile polymorphism, yet the difference was not statistically significant (p = .204). SCD patients with polymorphic genotypes had a greater number of hospital admissions (p = .03). Ten patients with acute chest syndrome had the homozygous polymorphic genotype (GG), and all patients with pulmonary hypertension had the polymorphic genotype (six were homozygous [GG] and five were heterozygous [GA]). Patients with SCD complicated with pulmonary hypertension showed significantly higher plasma TAFI levels (p = .044). CONCLUSION: The analysis of Thr325Ile polymorphisms combined with plasma TAFI levels suggests that the analyzed SNP could influence plasma TAFL levels and SCD disease severity and hospitalization rates, which could be predictors for complex disease.

Impaired Whole-Blood Fibrinolysis is a Predictor of Mortality in Intensive Care Patients.

Background Altered fibrinolysis is considered to play a crucial role in the development of coagulopathy in sepsis. However, routine laboratory tests for fibrinolysis are currently very limited, and the impact of fibrinolytic capacity on clinical outcome is poorly investigated. Objectives To assess whole-blood fibrinolysis in patients admitted to the intensive care unit (ICU) and compare fibrinolysis in sepsis patients with nonsepsis patients. Further, to investigate associations between fibrinolytic capacity and 30-day mortality and venous thromboembolism (VTE). Methods This study was designed as a prospective cohort study. Adult ICU patients were included at the Aarhus University Hospital, Denmark. All patients had a blood sample obtained the morning after admission. A modified thromboelastometry (ROTEM®) analysis with tissue plasminogen activator (ROTEM®-tPA) was used to assess fibrinolysis. The primary endpoint was difference in ROTEM®-tPA lysis time between sepsis patients and nonsepsis patients. Results ROTEM®-tPA revealed fibrinolytic impairment in sepsis patients ( n = 30) compared with nonsepsis ICU controls ( n = 129), with longer lysis time (median [interquartile range] 3,600 [3,352-3,600] vs. 3,374 seconds [2,175-3,600], p < 0.01), lower maximum lysis (23 [8-90] vs. 94% [14-100], p = 0.02), and lower fibrinolysis speed (0.41 [0.0-1.4] vs. 1.6 mm/min [0.1-2.7], p = 0.01). In the composite ICU population, 61% (97/159) demonstrated prolonged lysis time indicating impaired fibrinolytic capacity. These patients had higher 30-day mortality (adjusted odds ratio [OR]: 2.26 [0.83-6.69]) and VTE risk (OR: 3.84 [0.87-17.8]) than patients with normal lysis time. Conclusion Sepsis patients showed impaired fibrinolysis measured with ROTEM®-tPA compared with nonsepsis patients and ROTEM®-tPA lysis time was associated with 30-day mortality and VTE in the entire ICU cohort.

Corrigendum: Urokinase-type plasminogen activator and plasminogen activator inhibitor-1 complex as a serum biomarker for COVID-19.

[This corrects the article DOI: 10.3389/fimmu.2023.1299792.].

Comparison of results obtained using clot-fibrinolysis waveform analysis and global fibrinolysis capacity assay with rotational thromboelastography.

Global fibrinolysis assays detect the fibrinolysis time of clot dissolution using tissue-type plasminogen activator (tPA). Two such assays, clot-fibrinolysis waveform analysis (CFWA) and global fibrinolysis capacity (GFC) assay, were recently developed. These were compared with rotational thromboelastography (ROTEM). Healthy donor blood samples were divided into four groups based on tPA-spiked concentrations: 0, 100, 500, and 1000 ng/mL. CFWA and GFC fibrinolysis times, including 4.1 µg/mL and 100 ng/mL tPA in the assays, were determined, denoted as CFWA-Lys and GFC-Lys, respectively. Statistical differences were recognized between tPA concentrations of 0 and 500/1000 ng/mL for CFWA-Lys, and 0 and 100/500/1000 ng/mL for GFC-Lys. The correlation coefficients with lysis onset time (LOT) of extrinsic pathway evaluation and intrinsic pathway evaluation in ROTEM were statistically significant at 0.610 and 0.590 for CFWA-Lys, and 0.939 and 0.928 for GFC-Lys, respectively (p-values < 0.0001 for all correlations). Both assays showed significant correlations with ROTEM; however, the GFC assay proved to have better agreement with ROTEM compared with the CFWA assay. These assays have the potential to reflect a hyperfibrinolysis status with high tPA concentrations.

Impact of very low dose rivaroxaban in addition to dual antiplatelet therapy on endogenous fibrinolysis in acute coronary syndrome: The VaLiDate-R study.

BACKGROUND: Impaired endogenous fibrinolysis is adverse cardiovascular risk factor in acute coronary syndrome (ACS) patients. Addition of very low dose rivaroxaban (VLDR) to dual antiplatelet therapy (DAPT) reduces cardiovascular events but increases bleeding. OBJECTIVE: We aimed to assess whether addition of VLDR to DAPT can enhance endogenous fibrinolysis. METHODS: In a prospective, open-label trial, we assessed endogenous fibrinolysis in whole blood, in 549 patients with ACS using the Global Thrombosis Test (GTT) and Thromboelastography (TEG). Patients (n = 180) who demonstrated impaired endogenous fibrinolysis (lysis time [LT] >2000s with the GTT) were randomised 1:1:1 to (i) clopidogrel 75 mg daily; (ii) clopidogrel 75 mg daily plus rivaroxaban 2.5 mg twice daily; or (iii) ticagrelor 90 mg twice daily, for 30 days, in addition to aspirin. Fibrinolytic status was assessed at 0, 2, 4 and 8 weeks. The primary outcome was the change in LT from admission to week 4. We also measured thrombotic occlusion time (OT) at high shear, and rivaroxaban level. RESULTS: There was no difference between the groups with respect to LT or clot lysis with TEG, and no change in these parameters compared to baseline during study drug allocation. In the rivaroxaban plus clopidogrel group, OT was prolonged compared to the other groups, although rivaroxaban levels were low, suggesting non-compliance. CONCLUSION: Addition of rivaroxaban 2.5 mg twice daily to DAPT does not affect endogenous fibrinolysis of thrombus formed at either high or low shear. Further studies are needed to determine whether higher doses of rivaroxaban can favourably modulate fibrinolysis. CONDENSED ABSTRACT: Impaired endogenous fibrinolysis is a strong risk factor in ACS. We aimed to assess whether adding very low dose rivaroxaban (VLDR) to DAPT can enhance fibrinolysis. Fibrin and clot lysis were assessed in whole blood. ACS patients with impaired fibrinolysis were randomised 1:1:1 to clopidogrel 75 mg daily; clopidogrel 75 mg plus VLDR; or ticagrelor 90 mg twice daily, in addition to aspirin. At 30-days, there was no difference in lysis time between the groups, nor change from baseline. VLDR does not improve fibrinolysis at high or low shear. Further studies are needed to determine whether alternative antithrombotic regimens can enhance endogenous fibrinolysis.

Acute and subacute effects of strenuous exercise on platelet aggregation, coagulation and fibrinolysis in patients with stable coronary artery disease.

INTRODUCTION: Strenuous exercise may occasionally cause coronary thrombosis with myocardial infarction and sudden cardiac death. MATERIALS AND METHODS: Patients with stable coronary artery disease (CAD) (n = 164) and healthy individuals (n = 25) performed strenuous exercise on a bicycle ergometer. Blood was drawn at baseline, immediately after exercise and 2 h later. Platelet aggregation was measured with Multiplate® Analyzer. Thrombin generation was determined using a thrombogram and by measuring prothrombin fragment 1 + 2 (F1 + 2). A clot lysis assay was used to investigate fibrinolysis. RESULTS: From baseline to immediately after exercise, thrombin receptor activating peptide (TRAP)-induced platelet aggregation increased in CAD patients (Δ77 AU × min, 95 % confidence interval (CI): 46;107) and in healthy individuals (Δ153 AU × min, 95%CI: 75;232). Endogenous thrombin potential (ETP) was unaffected by exercise, whilst F1 + 2 increased (Δ17%, 95%CI: 11;24) in CAD patients. Fibrin clot lysis time increased by 9 % (95%CI: 1-17) in CAD patients and by 26 % (95%CI: 8;45) in healthy individuals. When comparing baseline to 2 h post-exercise, TRAP-induced platelet aggregation remained slightly elevated in both CAD patients (Δ53 AU × min, 95%CI: 22;84) and healthy individuals (Δ140 AU × min, 95%CI: 62;219). In contrast, ETP and F1 + 2 decreased in CAD patients (Δ-6 %, 95%CI: -10;-1 and Δ-8 %, 95%CI: -14;-2). Moreover, clot lysis time decreased (Δ-19 %, 95%CI: -27;-11) in patients with CAD and returned to baseline in healthy individuals. All p-values were <0.05. CONCLUSIONS: Platelet aggregation and F1 + 2 were substantially elevated immediately after exercise in CAD patients, indicating a pro-thrombotic state. After 2 h of recovery, they exhibited a markedly increase in fibrinolysis. Similar results were observed in healthy individuals.

A novel method to quantify fibrin-fibrin and fibrin-α2-antiplasmin cross-links in thrombi formed from human trauma patient plasma.

BACKGROUND: The widespread use of the antifibrinolytic agent, tranexamic acid (TXA), interferes with the quantification of fibrinolysis by dynamic laboratory assays such as clot lysis, making it difficult to measure fibrinolysis in many trauma patients. At the final stage of coagulation, factor (F)XIIIa catalyzes the formation of fibrin-fibrin and fibrin-α2-antiplasmin (α2AP) cross-links, which increases clot mechanical strength and resistance to fibrinolysis. OBJECTIVES: Here, we developed a method to quantify fibrin-fibrin and fibrin-α2AP cross-links that avoids the challenges posed by TXA in determining fibrinolytic resistance in conventional assays. METHODS: Fibrinogen alpha (FGA) chain (FGA-FGA), fibrinogen gamma (FGG) chain (FGG-FGG), and FGA-α2AP cross-links were quantified using liquid chromatography-mass spectrometry (LC-MS) and parallel reaction monitoring in paired plasma samples from trauma patients prefibrinogen and postfibrinogen replacement. Differences in the abundance of cross-links in trauma patients receiving cryoprecipitate (cryo) or fibrinogen concentrate (Fg-C) were analyzed. RESULTS: The abundance of cross-links was significantly increased in trauma patients postcryo, but not Fg-C transfusion (P < .0001). The abundance of cross-links was positively correlated with the toughness of individual fibrin fibers, the peak thrombin concentration, and FXIII antigen (P < .05). CONCLUSION: We have developed a novel method that allows us to quantify fibrin cross-links in trauma patients who have received TXA, providing an indirect measure of fibrinolytic resistance. Using this novel approach, we have avoided the effect of TXA and shown that cryo increases fibrin-fibrin and fibrin-α2AP cross-linking when compared with Fg-C, highlighting the importance of FXIII in clot formation and stability in trauma patients.

Time-dependent ultrastructural changes during venous thrombogenesis and thrombus resolution.

BACKGROUND: Deep vein thrombosis is a common vascular event that can result in debilitating morbidity and even death due to pulmonary embolism. Clinically, patients with faster resolution of a venous thrombus have improved prognosis, but the detailed structural information regarding changes that occur in a resolving thrombus over time is lacking. OBJECTIVES: To define the spatial-morphologic characteristics of venous thrombus formation, propagation, and resolution at the submicron level over time. METHODS: Using a murine model of stasis-induced deep vein thrombosis along with scanning electron microscopy and immunohistology, we determine the specific structural, compositional, and morphologic characteristics of venous thrombi formed after 4 days and identify the changes that take place during resolution by day 7. Comparison is made with the structure and composition of venous thrombi formed in mice genetically deficient in plasminogen activator inhibitor type 1. RESULTS: As venous thrombus resolution progresses, fibrin exists in different structural forms, and there are dynamic cellular changes in the compositions of leukocytes, platelet aggregates, and red blood cells. Intrathrombus microvesicles are present that are not evident by histology, and red blood cells in the form of polyhedrocytes are an indicator of clot contraction. Structural evidence of fibrinolysis is observed early during thrombogenesis and is accelerated by plasminogen activator inhibitor type 1 deficiency. CONCLUSION: The results reveal unique, detailed ultrastructural and compositional insights along with documentation of the dynamic changes that occur during accelerated resolution that are not evident by standard pathologic procedures and can be applied to inform diagnosis and effectiveness of thrombolytic treatments to improve patient outcomes.