Thrombin Generation Time Research Articles

Thrombin generation, fibrin clot permeation and lysis in patients with severe mitral regurgitation undergoing transcatheter edge-to-edge mitral valve repair: mitral fibrin study

Abstract Background/Introduction The management of heart failure (HF), particularly in the context of reduced ejection fraction, is further complicated by an increased risk of thromboembolic events. Structural alterations of both left ventricle and mitral valve contribute to mitral regurgitation (MR). However, the body of evidence provides inconclusive insights into the relationship between MR and thromboembolic risk. Purpose This study aimed to investigate the impact of transcatheter edge-to-edge repair (TEER) on thrombin generation, clot permeation and clot lysis time in HF patients with severe MR eligible for mitral TEER. Methods A cohort of 31 HF patients with severe MR undergoing TEER underwent systematic evaluation at three time points. Coagulation parameters, including fibrinogen concentration, thrombin generation, fibrin clot permeability (Ks), and clot lysis time (CLT), were assessed. Comprehensive evaluations also covered echocardiographic, laboratory, and clinical parameters. Results TEER induced changes in fibrinogen levels (p=0.009, visit 3 vs. visit 2) and improved fibrin clot properties over a 50-day follow-up (Ks, p=0.005, visit 3 vs. visit 2). No significant differences were observed among time points in analyzed blood clot parameters. Linear regression, incorporating thrombin generation variables, Ks, and CLT for delta NT-proBNP, highlighted CLT as the sole predictor of NT-proBNP change between visit 2 and visit 1 (p=0.03; R2=0.18). Conclusions MR reduction through TEER led to transient alterations in fibrinogen concentration and improved fibrin clot characteristics. Additionally, baseline CLT emerged as a significant predictor of early NT-proBNP reduction, emphasizing its role as a key indicator of the hemodynamic response to TEER.

Clot lysis time and thrombin generation in patients undergoing transcatheter aortic valve implantation.

Aortic valve stenosis (AS) is the most prevalent valvular heart disease and is associated with a significant increase in mortality. AS has been shown to be linked with numerous coagulation system abnormalities, including increased fibrin deposition on the stenotic aortic valves. Transcatheter aortic valve implantation (TAVI) is the primary treatment method for patients at high surgical risk. The aim of the study was to assess the impact of treating severe AS with TAVI on thrombin generation and clot lysis time (CLT). We studied 135 symptomatic AS patients recommended for TAVI by the local Heart Team. All measurements were performed before and 5-7 days after TAVI. Alongside clinical assessment and echocardiographic analysis, we assessed clot lysis time (CLT) and thrombin generation parameters, including lag time, peak thrombin generation, time to peak thrombin generation (ttPeak), and endogenous thrombin potential (ETP). 70 patients were included in the final analysis. After TAVI, there was a significant 9% reduction in CLT despite a 12% increase in fibrinogen concentration. We observed significant increase in lag time and ttPeak (20% and 12%, respectively), and 13% decrease in peak thrombin concentration compared to pre-procedural levels. Multivariable linear regression analysis demonstrated that baseline CLT and C-reactive protein (CRP) levels were independent predictors of significant reduction in mean aortic gradient, defined as TAVI procedure success. CLT and peak thrombin concentration decreased, while Lag time and ttPeak increased significantly after TAVI. Multivariable linear regression analysis demonstrated CLT and CRP levels as independent predictors of achieving a reduction in mean aortic gradient, defining TAVI procedure success.

Challenges in prophylactic therapy with Emicizumab in patients with hemophilia A: Focus on monitoring tests

Abstract This study presents a transversal investigation that we performed at Fundeni hospital (Bucharest, Romania) into the therapeutic benefits and efficacy of Emicizumab, a non-factor therapy, in the context of hemophilia A. Ten patients diagnosed with hemophilia A were closely monitored using clinical and laboratory resources during Emicizumab treatment, with an average of 12.8 months. Among these patients, six exhibited anti-factor VIII inhibitors, changing the medical strategy and adding complexity to their clinical profiles. A comprehensive approach was adopted to assess the coagulation status of patients under Emicizumab therapy. The study employed several key coagulation monitoring tools, including thrombin generation time (TGT) and thrombelastography (TEG). These methodologies generated valuable results in evaluating the patients’ coagulation profiles during the treatment regimen. Additionally, traditional coagulation assays were utilized to gain a profound understanding of the overall coagulation dynamics and to evaluate the therapeutic response. During prophylaxis with Emicizumab all patients experienced a reduced number of bleeding events. Moreover, a subset of these patients underwent major surgical procedures (orthopedic joint replacements, cholecystectomy) with successful outcomes. These findings underscore the potential of Emicizumab therapy as an effective option for hemophilia A patients, including those with inhibitors. Our research provides physicians several insights, offering a potential avenue for improved patients’ care and treatment strategies that translate in enhanced quality of life for hemophilia A patients undergoing Emicizumab therapy.

Leukemia Inhibitory Factor, Tissue Factor, Thrombomodulin, P-Selectine, D-Dimer, Thrombin Generation and Procoagulant Phospholipid Dependent Clotting Time Are Predictive for in Vitro Fertilization Outcome. the Prospective Roadmap-IVF Study

Background The link between blood hypercoagulability, endothelial cell activation and infertility or in vitro fertilization (IVF) failure is a puzzling issue. Activation of platelets, endothelial cells and blood coagulation, proinflammatory and angiogenetic potential play important role in implantation and early embryonic development. Biomarkers of cellular hypercoagulability are associated with high risk of IVF failure. Soluble Leukemia Inhibitory Factor (LIF), an interleukin 6 class cytokine expressed in the trophectoderm of the developing embryo is an important regulator in the establishment of pregnancy. Endoglin (Eng), a co-receptor for TGF-β1 and TGF-β3 is implicated in vascular complications of pregnancy and particularly in preeclampsia. Aim: The prospective longitudinal monocentric observational cohort study ROADMAP-IVF, evaluated the synergistic prognostic value of LIF and Eng with the biomarkers of cellular hypercoagulability in predicting the endometrial receptivity of fresh IVF cycles. Materials and Methods. The ROADMAP-IVF enrolled 40 women eligible for IVF with normal blood count, PT, aPTT, Fg, renal and liver function. The control group (CG) consisted of 30 healthy women with history of uncomplicated pregnancies. Exclusion criteria: Use of anticoagulant or antiplatelet agents during the last 30 days before inclusion. Known cardiovascular disease, active cancer. Active corticosteroid treatment. Primary end-point: Echographically documented pregnancy at 7 weeks from implantation. Blood was collected on day 2 (D2) from the natural cycle and 6 days after hormone treatment initiation corresponding to D8 of the cycle. Procoagulant phospholipid-dependent clotting time (PPL-ct), tissue factor (TF), thrombomodulin (TM), von Willebrand factor (vWF) and D-Dimers (DDi) were measured with assays from Diagnostica Stago (Asnieres, France). P- and E-Selectin, LIF and Eng were measured with ELISA. Thrombin generation (TG) with the TF 5 pM PPP-Reagent ® was assessed on Calibrated Automated Thrombogram (Stago, France). The cut-off values for studied biomarkers have been selected on the basis of ROC analysis. Univariate and multivariate logistic regression analysis examined the associations between the biomarkers and the study outcome. Results: 40 women were enrolled in the study. In 11 women pregnancy was confirmed with ultrasound and in 23 women no pregnancy was echographically documented. Age was not significantly different between the IVF (41 ys; range 22 - 48 ys) and the control group (40 ys; range 20 - 46 ys). At D2 and D8 the DDi and LIF were significantly higher in IVFG as compared to the CG. At D2 most of the patients had PPL-ct, DDi and MRI of TG higher than the upper normal limit (UNL). At D8 only TF was significantly increased as compared to the CG. Analytical data are presented in Table 1. Age did not correlate with the levels of the studied biomarkers. Significant correlations (p<0.05) were found between DDi and ETP (r=0.35); TM, TF and P-Selectin (r=0.4) at D2; TF, LIF and Eng (r=0.5) at D2 and D8; P-Selectin and PPL-ct (r=-0.4) at D2; P-Selectin and TM (r=0.4), E-Selectin (r=0.5), LIF (0.4) at D2; E-Selectin and P-Selectin (r=0.5), TF (r=0.3), and LIF (r=0.4) at D2. The ROC analysis showed that IVF failure was associate with DDi increase at D2 (AUC = 0.64); P-Selectin increase at D2(AUC = 0.57) and D8 (AUC = 0.61); TM increase at D8 (AUC = 0.61); TF increase at D8 (AUC = 0.57); LIF increase at D8 (AUC = 0.59); ETP increase at D2 (AUC = 0.67) and D8 (AUC = 0.67); Peak increase at D2 (AUC = 0.64) and D8 (AUC = 0.61). Prolongation of PPL-ct on D8 was predictive for positive pregnancy outcome(AUC 0.64). Conclusion The ROADMAP-IVF study showed that at least one out of four women eligible for IVF present biological evidence of activation of platelets, endothelial cells, blood coagulation or LIF upregulation. Hormone treatment administration does not significantly alter the proinflammatory or the hypercoagulable state. Among the studied biomarkers the levels of LIF, DDi, P-Selectine, TM and TF as well as the status of thrombin generation and PPL-ct showed a significant predictive value for the IVF outcome, particularly when measured at 6 days after hormone treatment administration. These findings will lead to the elaboration of an risk assessment model for IVF failure combining the selected biomarkers of hypercoagulability with LIF.

POSTER ABSTRACTS

POSTER ABSTRACTS

Cryopreservation of apheresis platelets treated with riboflavin and UV light

BackgroundPathogen reduction technology (PRT) is increasingly used in the preparation of platelets for therapeutic transfusion. As the Czech Republic considers PRT, we asked what effects PRT may have on the recovery and function of platelets after cryopreservation (CP), which we use in both military and civilian blood settings. Study design and methods16 Group O apheresis platelets units were treated with PRT (Mirasol, Terumo BCT, USA) before freezing; 15 similarly collected units were frozen without PRT as controls. All units were processed with 5–6% DMSO, frozen at − 80 °C, stored > 14 days, and reconstituted in thawed AB plasma. After reconstitution, all units were assessed for: platelet count, mean platelet volume (MPV), platelet recovery, thromboelastography, thrombin generation time, endogenous thrombin potential (ETP), glucose, lactate, pH, pO2, pCO2, HCO3, CD41, CD42b, CD62, Annexin V, CCL5, CD62P, and aggregates > 2 mm and selected units for Kunicki score. ResultsPRT treated platelet units had lower platelet number (247 vs 278 ×109/U), reduced thromboelastographic MA (38 vs 62 mm) and demonstrated aggregates compared to untreated platelets. Plasma coagulation functions were largely unchanged. ConclusionsSamples from PRT units showed reduced platelet number, reduced function greater than the reduced number would cause, and aggregates. While the platelet numbers are sufficient to meet the European standard, marked platelets activation with weak clot strength suggest reduced effectiveness.

Crassostrea gigas-Based Bioactive Peptide Protected Thrombin-Treated Endothelial Cells against Thrombosis and Cell Barrier Dysfunction

The activation of thrombin-treated endothelial cells resulted in disruption of the vascular tissues. A novel oyster-derived bioactive dodecapeptide (IEELEELEAER, P-2-CG) was reported to protect the human umbilical vein endothelial cells and their barrier function via the decrease of VE-cadherin disruption and the restoration of the F-actin arrangement. The promotion of the extrinsic pathway in this case triggers the release of tissue factors that occurs on the surface of the endothelial cells, thus changing the antithrombotic to prothrombotic. P-2-CG induced accordingly a prolongation of plasma clotting time and thrombin generation time, following the alteration of the antithrombotic phenotype. Furthermore, the antithrombotic activity of P-2-CG was also supported by the reduction of FXa and the inhibition of other factors release, for instance, inflammation factors, ROS, etc. In addition to its antithrombogenic role, P-2-CG displayed anti-inflammatory and antioxidant properties via the mitogen-activated protein kinase cascades and central signaling pathways as shown in an in vitro model of endothelial dysfunction.

A comprehensive method to explore inhibitory kinetics and mechanisms of an anticoagulant peptide derived from Crassostrea gigas

A comprehensive method was applied to evaluate the anticoagulant activity of a novel anticoagulant peptide (NAESLRK) derived from oyster (Crassostrea gigas). The anticoagulant peptide drastically reduced the extrinsic clotting activity and also impaired the intrinsic clotting activity slightly. Consistent with clotting data, the thrombin peak height was reduced to 84.7 nmol/L from 123.4 nmol/L, and thrombin generation time was delayed to 4.67 min from 4.42 min when the extrinsic trigger was applied. The inhibitory kinetics of FXIa, FIXa, FXa, FIIa, and APC in a purified component system rationally explained the reduction of extrinsic clotting activity and impairment of thrombin generation. Besides the inhibition of FXa and FIIa activity, the activation processes of FX and FII by intrinsic/extrinsic tenase complex and prothrombinase were also damaged. The anticoagulant activity in the plasma system was the result of comprehensive inhibition of various factors. The research provided a novel method for anticoagulant evaluation and inhibitory mechanism of bioactive peptides from food products.

Protection of β2GPI Deficient Mice from Thrombosis May Reflect a Platelet Activation Defect

IntroductionAntiphospholipid syndrome (APS) is an autoimmune disorder caused by “antiphospholipid” antibodies (aPL) directed against β2-glycoprotein I (β2GPI). Although β2GPI is proposed to have both anti- and procoagulant properties in vitro, its physiological role in coagulation in vivo is not well understood. Previous studies have shown that β2GPI deficient mice display impaired thrombin generation but failed to demonstrate an anticoagulant role in vivo. Recent findings from our laboratory demonstrated that β2GPI-deficient mice (APOH -/-) developed by CRISPR/Cas9 had shown delayed time to thrombosis as evidenced by prolonged clotting times in carotid artery occlusion models. However, no mechanism was identified for the delayed time to thrombosis phenotype.MethodsVenous thrombosis by complete occlusion of the IVC was performed as described previously (Wrobleski et al., 2011). In brief, an abdominal incision was made on anesthetized mice to visualize IVC. The activated partial thromboplastin time (aPTT); prothrombin time (PT) and Tissue factor-induced thrombin generation time (TGT) were performed as described previously (Stavrou et al., 2014). Protein C activity was performed according to manufacturer's recommendations (Chromogenix Coamatic® Protein C, Diapharma). To assess platelet activation, platelets were isolated under resting conditions using retro-orbital blood and the final washed platelet pellet was resuspended in Tyrodes solution. Platelets were stimulated with 0.25 U/ml thrombin and incubated with 1 µL of CD62P-FITC or Oregon Green conjugated-fibrinogen for 30 minutes. Platelets were fixed with 100 μL 2% formalin, and quantification of platelet surface P-selectin and fibrinogen binding to activated platelet GPIIb/IIIa was performed by flow cytometry (Accuri Flow Cytometer, BD Biosciences). For mouse tail vein bleeding time assays, mice were anesthetized and the tail transected approximately 5 mm from the tip. The tail was then placed in a 50 ml falcon tube containing saline pre-warmed to 37°C. The time to cessation of bleeding was determined visually. All experiments were performed on 8-12 week old mice.ResultsaPTT and PT results for APOH +/+ and APOH -/- mice were 41.82 ± 1.174 and 41.38 ± 2.026 seconds, and 14.55 ± 2.262 and 11.30 ± 0.578 seconds, respectively (NS). After IVC ligation, thrombi in APOH -/- mice had a mean weight of 16.94 ± 1.782 mg compared to 27.69 ± 1.725 mg in APOH +/+ mice littermates (P = 0.0002, Figure A). Thrombin generation induced by either tissue factor or aPPT reagent showed peak thrombin generation at 15 min with no difference between APOH +/+ and APOH -/- mice. Likewise, no significant differences were observed in percent Protein C activity levels between APOH +/+ (8.058 ± 1.433) and APOH -/- (6.453 ± 0.924).Stimulation with 0.25 U/ml thrombin resulted in significantly greater expression of P-selectin) on platelets of APOH +/+ (161.3 ± 30.62 MFI) compared to those from APOH -/- mice (54.47 ± 9.721 MFI) (P= 0.0101;Figure 1B). Likewise, there was significantly greater fibrinogen binding to stimulated platelets from APOH +/+ (129.7 ± 32.21 MFI) compared to APOH-/- mice (35.30 ± 2.144 MFI) with P = 0.0111 (Figure 1C). Finally, consistent with platelet activation studies, tail vein bleeding times were mildly, but significantly prolonged in APOH -/- mice (192.3 ± 45.86 sec) compared to APOH+/+ mice (95.14 ± 9.582 sec) with P = 0..ConclusionThe effects of β2GPI, if any, on coagulation processes is controversial, and has not been thoroughly studied in β2GPI deficient animals. The results presented here suggest that the smaller thrombi that form in mice deficient in β2GPI following IVC occlusion may reflect a mild platelet function defect. This hypothesis is supported by diminished P-selectin expression and fibrinogen binding in response to 0.25 U/ml thrombin by platelets from β2GPI deficient mice compared to wild-type littermates. Moreover, tail vein bleeding times were mildly prolonged in β2GPI deficient mice. Taken together, these studies suggest that β2GPI may actually contribute to hemostasis by supporting platelet responses to low concentrations of thrombin. Additional studies are needed to characterize these effects in detail. [Display omitted] DisclosuresMcCrae: Sanofi, Novartis, Alexion, and Johnson & Johnson: Consultancy, Honoraria; Dova, Novartis, Rigel, and Sanofi Genzyme: Consultancy.

COVID-19-associated coagulopathy in children and adolescents

The pandemic of the new coronavirus infection COVID-19 in 2020 has become the main health problem across the globe. A special characteristic of the SARSCoV-2 virus is tropism to the vascular endothelium with the development of endotheliitis, which entails a number of typical disorders of the blood coagulation system: coagulopathy with increased thrombin generation, D-dimer, decreased fibrinolysis and prolonged prothrombin time. The coagulation disorder in COVID-19 is called thromboinflammation. Hyperinflammation, increased blood levels of von Willebrand factor, coagulation factor VIII, neutrophil extracellular traps, platelet activation, microvesicles play a significant role in the pathogenesis of hypercoagulation in COVID-19. To date, it is known that cases of COVID-19 in children and adolescents constitute a small part of the total number of patients with diagnosed COVID-19, and disorders of the blood coagulation system are similar to those in adults. The degree of hypercoagulable syndrome and the risk of thrombosis depend on the severity of COVID-19. And for children they are most expressed with the development of a hyperinflammatory immune response, called multisystem inflammatory syndrome. At the same time, clinical studies of the pathogenesis of COVID-19 in adults and children and the search for optimal methods of therapy for thrombus inflammation, which underlies the pathogenesis of COVID-19, continue.

A Novel Immunoblot Assay to Detect Contact Activation in Patients with Cancer

Introduction:The risk of thrombosis is markedly increased in patients with cancer and associated with increased morbidity and mortality. Clinical scoring systems are helpful to stratify cancer patients at a highest risk for thrombotic events. However, more precise risk prediction is needed, particularly for patients with cancers associated with intermediate thrombotic risk. In some, but not all studies, evidence of activation of coagulation proteases as measured using assays such as thrombin generation times, D-dimer levels, etc., has correlated with thrombotic risk, though these correlations are generally not robust. Recent studies have demonstrated that the contact activation pathway plays an important role in the development of pathologic thrombosis, though its role in cancer-associated thrombosis has not been clearly defined. However, unlike assays that measure prothrombin activation, limited options for assessing contact activation are available. To examine this question, we have developed a quantitative immunoassay for contact activation that assesses cleavage of high molecular weight kininogen (HK), a marker of contact system activation, in patient plasma. Circulating cleaved HK (HKa) has been found in plasma in disorders such as hereditary angioedema, and our studies in mice demonstrate that HK is quantitatively cleaved within murine tumors.Methods:To detect circulating HKa, one microliter of plasma was analyzed using SDS-PAGE on a 4-12% gel under reduced conditions. Following transfer to low-fluorescence PVDF membranes, the sample was immunoblotted using an affinity-purified rabbit polyclonal antibody raised to a peptide encompassed by the C-terminal region of the HK heavy chain (CQPLGMISLMK). Bound antibody was detected using an IRDye® 800CW-labeled goat anti-Rabbit secondary antibody followed by band quantification using a LI-COR Odyssey imaging system and Image StudioTM Lite Software. This assay detects both intact kininogen (MW ~ 120 kD) and the cleaved kininogen heavy chain (MW ~ 50 kD). To control for different levels of kininogen in individual patients, cleaved kininogen was quantified by estimating the relative amount of kininogen heavy chain as a percentage of uncleaved kininogen using LI-COR technology.Results:To date, we have used this assay to assess kininogen cleavage in 11 patients with several different cancers including breast cancer (N = 3), bladder cancer (N = 1), pancreatic cancer (N = 5), acute myeloid leukemia (N = 1), and renal cancer (N = 1). Patients with cancer demonstrated a greater percentage of cleaved HK in plasma than normal donor controls, in whom less than 1% of kininogen was present in the cleaved form. The greatest amount of cleavage was observed in pancreatic cancer, and was estimated at 33.4% (see Table).Conclusion:These studies provide evidence that the contact activation system is activated in many patients with cancer. Current effort is focused on identifying causes of variation in contact activation between cancers, and determining whether the extent of contact activation as determined by this quantitative assay correlates with or predicts the development of thrombosis in cancer patients. [Display omitted] DisclosuresKhorana:Halozyme: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Bayer: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Leo: Consultancy, Honoraria, Research Funding; Janssen Scientific Affairs, LLC: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria.

An Ex Vivo Analysis of Thrombin Generation and Thromboelastometry in Patients Undergoing Treatment with Rivaroxaban Demonstrates Sustained Anticoagulant Effect and High Inter-Individual Variability

Background : Rivaroxaban, 20 mg orally administered once daily, is widely used for secondary prevention of venous thromboembolism (VTE) without the need for routine laboratory monitoring. It is licensed for the prevention of VTE after major orthopedic surgery, for the treatment of acute symptomatic VTE, the secondary prevention of VTE and for prevention of stroke in patients with non-valvular atrial fibrillation. Rivaroxaban selectively and competitively inhibits free factor Xa (FXa) and prothrombinase/clot-associated FXa through reversible interactions thereby inhibiting thrombin generation and decreasing fibrin clot formation. The need of laboratory evaluation of rivaroxaban is actually questioned.Aim : In patients treated for secondary prevention of VTE, we evaluated ex vivo the anticoagulant potency of rivaroxaban treatment at different times after drug intake.Methods : 97 patients (39 males, 58 females; median age: 59 years) with idiopathic VTE were treated with rivaroxaban (20 mg/day) for a period longer than 6 months and compared to 30 controls age and sex-matched. Rivaroxaban concentrations (STA®-Liquid Anti-Xa), thrombin generation (PPP-reagent 5 pM TF; calibrated automated thrombogram, Stago France) and whole blood thromboelastometry (5 pM tissue factor; ROTEM® Werfen) were assessed. The interval between drug intake and blood sampling was registered.Results : Treatment with rivaroxaban significantly inhibited thrombin generation (TG) and prolonged clotting time (CT): 93% of patients had TG inferior to the lower normal limit and 77% had CT longer than the upper normal limit. This effect in both assays, was not correlated to its plasma concentrations, it was significant from the 1st hour after drug intake and persisted at similar levels during the daily therapeutic cycle even at low concentrations (30 ng/ml). Rivaroxaban had no effect on clot firmness. The inter-individual coefficient of variation of rivaroxaban concentrations and TG/ROTEM alterations after drug intake ranged from 50% to 100%.Conclusion : Once daily administration of rivaroxaban induces sustained daily anticoagulant effect, detected by TG and ROTEM assays, with no significant changes related to drug concentration reduction. This profile could explain the wide therapeutic window and the favorable benefit risk ratio of the treatment with rivaroxaban. Due to the high variability the identification of patients with extreme values of TG could be useful strategy for treatment optimization on individual basis. DisclosuresNo relevant conflicts of interest to declare.

Acute exacerbations of COPD are associated with a prothrombotic state through platelet-monocyte complexes, endothelial activation and increased thrombin generation

IntroductionPatients with chronic obstructive pulmonary disease (COPD) are at increased risk for cardiovascular events, particularly following an acute exacerbation (AE-COPD). Exacerbations are associated with increased systemic inflammation, which may drive coagulation. This prospective cohort study aimed to determine how an AE-COPD affects platelet activation, the endothelium, plasmatic coagulation and fibrinolysis, and its association with systemic inflammation. Materials and methodsFifty-two patients with an AE-COPD were included. Blood samples at admission, at day 3 of treatment and at convalescence were available for 32 patients. Platelet-monocyte complex (PMC) formation, monocyte Mac-1 expression and platelet (re)activity (P-selectin expression, αIIbβ3 activation) were measured by flow cytometry. Von Willebrand Factor (VWF), thrombin generation (TG) and clot lysis time (CLT) were determined as measures of endothelial activation, plasmatic coagulation and fibrinolysis, respectively. ResultsExacerbations were associated with increased PMCs (MFI 31.3 vs 23.8, p = 0.004) and Mac-1 (MFI 38.2 vs 34.8, p = 0.006) compared to convalescence, but not with changes in platelet (re)activity. VWF (antigen, activity, active fraction) and TG (peak, ETP and velocity index) were all significantly higher during AE-COPD compared to convalescence. PMCs, Mac-1, VWF and TG were positively associated with systemic inflammation (CRP). CLT was prolonged in AE-COPD patients with systemic inflammation. Moreover, platelet hyperreactivity on admission was associated with an increased risk for exacerbation relapse. ConclusionsAcute exacerbations are associated with an inflammation-associated prothrombotic state, characterized by increased PMCs, endothelial activation and plasmatic coagulation. Our findings provide direction for future studies on biomarkers predicting the risk of exacerbation relapse and cardiovascular events.

Hemostatic potential of cold-stored non-leukoreduced whole blood over time: An assessment of platelet function and thrombin generation for optimal shelf life.

Cold-stored low-titer whole blood (WB) is becoming increasingly used as the preferred product for initial hemorrhagic shock resuscitation. The purpose of this study was to identify whether the current 21-day shelf life is the optimal duration for storage of WB, maintaining hemostatic efficacy. Five units of fresh low-titer group O WB (non-leukoreduced) were acquired from our regional blood center. These units were stored at 4°C for up to 21 days as per current clinical storage guidelines in our emergency department. Hemostatic parameters were measured in vitro at 0 days, 7 days, 14 days, and 21 days. Assessments of hemostatic potential included cell count, rapid thrombelastography (r-TEG) and kaolin thrombelastography (TEG), multiplate impedance aggregometry, and calibrated automated thrombogram (CAT). Univariate analysis, including one-way analysis of variance with repeated measures, was performed (STATA 12.1). Compared with baseline product (0 days), both platelet count and platelet function of WB showed sharp decreases at 7 days and again at 14 days. Platelet function deterioration was noted by r-TEG c (MA), TEG-MA, and multiplate arachidonic acid and adenosine diphosphate (all p < 0.001). With respect to clot initiation, r-TEG ACT and TEG R-time were similar over the 21-day shelf life (p = 0.058 and p = 0.620, respectively). Thrombin generation assessed by CAT demonstrated stable endogenous thrombin potential over the course of storage (p = 0.162), but increased peak thrombin generation and quicker time to peak generation after 7 days. While the platelet function of WB degrades significantly at 7 days (and again at 14 days), clot initiation remains stable over time, and thrombin generation appears to be improved at 7 days. This study supports a current storage limit for cold-stored, low-titer WB of 14 days.

Evaluation of thromboelastometry, thrombin generation and plasma clot lysis time in patients with bleeding of unknown cause: A prospective cohort study.

Diagnostic evaluation of patients with a bleeding tendency remains challenging, as no disorder is identified in approximately 50% of patients. An impaired interplay of several haemostatic factors might explain bleeding phenotype in these patients. To investigate whether global haemostasis assays are able to identify haemostatic abnormalities in patients with a bleeding tendency unexplained by current diagnostic laboratory tests. Patients of ≥12years with a bleeding tendency were included from a tertiary outpatient clinic. Bleeding phenotype was assessed with the ISTH-BAT. Patients were classified as having bleeding of unknown cause (BUC) or a mild bleeding disorder (MBD) based on abnormalities assessed by routine haemostatic tests. Global haemostasis tests (rotational thromboelastometry (ROTEM), thrombin generation test (TG) and plasma clot lysis time (CLT)) were measured in all patients. The results were compared with 76 controls. One hundred and eighty-one patients were included, and 60% (109/181) was classified as having BUC. BUC patients demonstrated a significantly prolonged lag time in TG (median 7.7minutes, IQR 6.7-8.7) and a significantly prolonged CLT (median 60.5minutes, IQR 54.7-66.1) compared to controls. No differences in ROTEM variables were found. Patients with MBD showed an impaired thrombin generation with a significantly decreased ETP (median 1024nmol/L*min, IQR 776-1355) and peak height (median 95nmol/L, IQR 76-138), compared to BUC patients and controls. No major differences were found in ROTEM and TG variables in BUC patients compared to controls. BUC patients did have a significantly prolonged clot lysis time. The underlying mechanism for this finding is unknown.

Plasma levels of enoxaparin oligosaccharides, antifactor-Xa and thrombin generation in patients undergoing haemodialysis.

: Low molecular weight heparins are used during haemodialysis for thromboprophylaxis of the dialysis circuit, with plasma antifactor-Xa (anti-Xa) activity used as a surrogate measure for effective anticoagulation. However, this pharmacokinetic parameter does not always correlate with pharmacodynamic effects in patients. The aim of this study was to investigate the relationship between actual plasma levels of the low molecular weight heparins enoxaparin, anti-Xa activity, and global coagulation measurement of thrombin generation during haemodialysis. Blood was analysed from 16 adult patients with end-stage kidney disease at 0, 2, 4 h, and at completion of 31 dialysis sessions where single fixed doses of 20 (n = 3), 40 (n = 16), 60 (n = 6), or 80 (n = 6) mg of enoxaparin (equating to 0.23-1.07 mg/kg) were used as thromboprophylaxis. Plasma enoxaparin oligosaccharides [degree of polymerization (dp)6-dp16] were measured by high-performance size exclusion chromatography, anti-Xa activity by colourimetric assay, and thrombin generation by calibrated automated thrombogram. Plasma enoxaparin fragments were undetectable at the beginning of each dialysis, peaked at 2 h to levels that correlated with dose (r = 0.68, P < 0.001) then remained relatively stable. In contrast, therapeutic anti-Xa levels achieved at 2 h in 18 cases (58%) quickly dropped to only six cases (19%) at the end of dialysis, by which time thrombin generation had also recovered in 81% of patients. Statistical modelling revealed a threshold value of anti-Xa at 0.53 IU/ml that supressed thrombin generation to 15.28% of baseline (P < 0.001). Despite loss of anticoagulant activity in the majority of patients, plasma levels of enoxaparin oligosaccharides remained detectable and relatively unchanged throughout dialysis.

Hydroxychloroquine reverses the prothrombotic state in a mouse model of antiphospholipid syndrome: Role of reduced inflammation and endothelial dysfunction.

Antiphospholipid antibodies (aPL) promote endothelial dysfunction, inflammation and procoagulant state. We investigated the effect of hydroxychloroquine (HCQ) on prothrombotic state and endothelial function in mice and in human aortic endothelial cells (HAEC). Human aPL were injected to C57BL/6 mice treated or not with HCQ. Vascular endothelial function and eNOS were assessed in isolated mesenteric arteries. Thrombosis was assessed both in vitro by measuring thrombin generation time (TGT) and tissue factor (TF) expression and in vivo by the measurement of the time to occlusion in carotid and the total thrombosis area in mesenteric arteries. TGT, TF, and VCAM1 expression were evaluated in HAEC. aPL increased VCAM-1 expression and reduced endothelium dependent relaxation to acetylcholine. In parallel, aPL shortened the time to occlusion and extended thrombus area in mice. This was associated with an overexpression of TF and an increased TGT in mice and in HAEC. HCQ reduced clot formation as well as TGT, and improved endothelial-dependent relaxations. Finally, HCQ increased the p-eNOS/eNOS ratio. This study provides new evidence that HCQ improves procoagulant status and vascular function in APS by modulating eNOS, leading to an improvement in the production of NO.

Four-factor prothrombin complex concentrate improves thrombin generation and prothrombin time in patients with bleeding complications related to rivaroxaban: a single-center pilot trial

BackgroundDirect oral anticoagulants (DOACs) pose a great challenge for physicians in life-threatening bleeding events. The aim of this study was to test the efficacy of reversing the DOAC rivaroxaban using four-factor PCC (prothrombin complex concentrate), a non-specific reversing agent.MethodsPatients with life-threatening bleeding events during rivaroxaban treatment were included and administered 25 U kg−1 of PCC. Blood samples were collected immediately prior to as well as after PCC treatment at predefined time intervals. The primary endpoint was defined as the difference in thrombin generation (TG) parameters ETP (endogenous thrombin potential) and Cmax (peak thrombin generation) prior to and ten minutes subsequent to PCC treatment.ResultsThirteen patients, of whom the majority suffered from intra-cranial haemorrhage (ICH) or subdural haemorrhage (SDH), were included and administered PCC. The results show that the ETP (TG) significantly (p = 0.001) improved by 68% and Cmax (TG) by 54% (p = 0.001) during PCC treatment. In addition, the Quick value (prothrombin time: QuickPT) significantly improved by 28% and the activated partial thromboplastin time (aPTT) was decreased by 7% ten minutes after PCC administration. Cmax was reduced at baseline, but not ETP, aPTT or QuickPT. Lag time until initiation (TG, tlag), thromboelastometry clotting time (CTEXTEM) and time to peak (TG, tmax) correlated best with measured rivaroxaban levels and were out of normal ranges at baseline, but did not improve after PCC administration. In 77% of the patients bleeding (ICH/SDH-progression) ceased following PCC administration. During the study three participants passed away due to other complications not related to PCC treatment. The possibility of thrombosis formation was also evaluated seven days after administering PCC and no thromboses were found.ConclusionsThis study shows that use of PCC improved ETP, Cmax, QuickPT and aPTT. However, of these parameters, only Cmax was reduced at the defined baseline. It can be concluded that CTEXTEM, tlag and tmax correlated best with the measured rivaroxaban levels. The study drug was found to be safe. Nonetheless, additional studies specifically targeting assessment of clinical endpoints should be performed to further confirm these findings.Clinical trial registrationEudraCT trial No. 2013–004484-31.

Biocompatible sulfenamide and sulfonamide derivatives of metformin can exert beneficial effects on plasma haemostasis

As the pharmacokinetic properties of metformin are unfavourable, several analogues and prodrugs have been synthesised to improve its bioavailability. The aim of this study was to assess the plasma stability of sulfenamide and sulfonamide derivatives of metformin and establish their effects on plasma haemostasis and integrity of red blood cells (RBCs).The overall haemostasis potential was evaluated spectrophotometrically by clot formation and lysis test (CL-test). PT (Prothrombin Time) and APTT (Activated Partial Tromboplastin Time) were used to evaluate the effects if the compounds on the extrinsic and intrinsic coagulation pathway. Haemolysis assay, microscopy and flow cytometry studies were conducted to determine the effect of the compounds on RBCs.Two sulfonamide and one sulfenamide derivatives of metformin were associated with a statistically significant decrease in the overall potential of clot formation and fibrinolysis (↓ CLAUC), suggesting that these compounds may exert beneficial effects regarding plasma haemostasis, which is frequently impaired in diabetic patients. p- and o-Nitrobenzene sulfonamides contributed to the beneficial change in kinetic parameters of clot formation and fibrinolysis. o-Nitrobenzene sulfonamide significantly increased thrombin generation time (↑ TGt) and was also found to prolong both APTT and PT. All compounds did not exert any effects on the integrity of RBCs over the concentration range 0.006–0.6 μmol/mL which constitutes the expected therapeutic concentration.In conclusion, sulfonamide derivatives of metformin present potentially beneficial properties in terms of plasma haemostasis which is frequently impaired in T2DM patients. Therefore, metformin sulfonamides may become a prototype for further design and synthesis of novel metformin analogues and prodrugs with improved pharmacokinetic properties.

19 Accuracy of biomarkers for venous thromboembolism in pregnancy: the diagnosis of pulmonary embolism in pregnancy (DiPEP) biomarker study

ObjectiveTo estimate the accuracy of biomarkers for venous thromboembolism (VTE) in pregnant and postpartum women with suspected pulmonary embolism (PE).DesignObservational cohort study augmented with additional cases with VTE.SettingEmergency departments and...