scholarly journals Contact activation: important to consider when measuring the contribution of tissue factor-bearing microparticles to thrombin generation using phospholipid-containing reagents

2014 ◽  
Vol 12 (4) ◽  
pp. 515-518 ◽  
Author(s):  
N. Boknäs ◽  
L. Faxälv ◽  
T. L. Lindahl ◽  
S. Ramström
Keyword(s):  
Tissue Factor ◽  
Thrombin Generation ◽  
Contact Activation

scholarly journals The Role of Factor XI in Thrombin Generation Induced by Low Concentrations of Tissue Factor

2001 ◽  
Vol 85 (06) ◽  
pp. 1060-1065 ◽  
Author(s):  
Irene Keularts ◽  
Ariella Zivelin ◽  
Uri Seligsohn ◽  
H. Coenraad Hemker ◽  
Suzette Béguin
Keyword(s):  
Tissue Factor ◽  
Thrombin Generation ◽  
Contact Activation ◽  
Factor Xi ◽  
Platelet Poor Plasma ◽  
Low Concentrations ◽  
Time Determination ◽  
Thrombin Formation

SummaryThrombin generation has been studied in the plasma of severely factor XI deficient patients under conditions in which contact activation did not play a role. In platelet-rich as well as platelet-poor plasma, thrombin generation was dependent upon the presence of factor XI at tissue factor concentrations of between 1 and 20 pg/ml i.e. ~ 0.01 to 0.20% of the concentration normally present in the thromboplastin time determination. The requirement for factor XI is low; significant thrombin generation was seen at 1% factor XI; at 10%, thrombin formation was nearly normalised. A suspension of normal platelets in severely factor XI deficient plasma did not increase thrombin generation. This implies that there is no significant factor XI activity carried by normal platelets, although the presence of factor XI and factor XI inhibitors in platelets cannot be ruled out.

scholarly journals Laboratory Characterization of Unclassified Bleeding Disorders By Non-Conventional Tests

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4235-4235
Author(s):  
Paula Acuña ◽  
Elena Monzón Manzano ◽  
Elena G Arias-Salgado ◽  
María Teresa Alvarez Román ◽  
Mónica Martín ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Platelet Function ◽  
Research Funding ◽  
Thrombin Generation ◽  
Bleeding Tendency ◽  
Contact Activation ◽  
Normal Range ◽  
Coagulation Tests ◽  
In Vitro Treatment

Abstract Introduction: Hematologists frequently face a percentage of patients with a mild bleeding tendency due to a haemostatic abnormality that cannot be identified with conventional laboratory techniques. Such patients are termed as having an unclassified bleeding disorder (UBD). A good diagnosis is important in order to prevent bleedings during invasive processes and/or childbirth by choosing the optimal therapeutic treatment. We aimed to investigate hemostatic parameters that may be altered in patients with UBD in order to determine the cause of their bleeding symptoms. In particular, possible defects in the tissue factor (TF)-mediated regulation of coagulation or in the plasmin generation during the fibrinolysis, as well as the possible beneficial effects of treatment with antibodies blockers of TFPI. Methods: This is a single-centre, case-control, non-interventionist, prospective study. During an 8 months-period, 40 patients with bleeding symptoms (evaluated with ISTH-BAT score) were studied. Routine coagulation tests (aPTT and PT) and platelet function testing [aggregometry, PFA-100, flow cytometry and Total Thrombus-formation Analysis System (T-TAS; Zarcos, Japan)] were performed. In 17 patients, no abnormalities were detected in platelet function and/or in coagulation tests; so the following procedures were performed: Thrombin generation test by Calibrated automated thrombography (CAT) in samples of platelet poor plasma with corn trypsin inhibitor (CTI), an inhibitor of contact activation phase, using a low amount of TF (1 pM TF and 4 µM phospholipids) as a trigger to allow the evaluation of the TF-dependent pathway. Plasmin generation (PG) test with a kit from Synapse Research Institute (Maastricht, The Netherlands), using Thrombinoscope software. TFPI activity in plasma, measured with ACTICHROME® TFPI kit (Biomedica Diagnostics, USA). The effects of rFVIIa (Novoseven, NovoNordisk; 90 µg/kg) and of a human Anti-TFPI recombinant Ab (clon mAb2021, Creative Biolabs; 400 ng/ml) were tested in CAT, PG and TFPI activity tests. Results: Those patients with aPTT, PT and a platelet function within normal range were further studied performing thrombin generation, plasmin generation and TFPI activity tests. Table 1 shows the results obtained. Samples from patients 1, 2, 4, 7, 8, 9 and 10 had a diminished generation of thrombin, and in vitro treatment with anti-TFPI and rFVIIa only ameliorated thrombin generation in samples from patients 4, 7, 8 and 9. Plasma from patients 8 and 10 had increased activity of TFPI. Generation of thrombin in samples from patients 3, 5, 6 and 11 was within normal range. Plasmin generation was increased and not modified by in vitro treatment with anti-TFPI and rFVIIa in samples 3 and 11; whereas samples 5 (with normal plasmin generation) and 6 (with no data of plasmin generation due to lack of enough sample) had a high TFPI activity in plasma that was inhibited by anti-TFPI. Normal values in all these parameters evaluated were found in six patients, indicating the involvement of different mechanisms that are still unknown. Conclusions: UBD have a diverse pathological basis for the bleeding. So, a single laboratory test to make a correct diagnosis of this pathology cannot be recommended. In accordance with this fact, a personalized treatment should be applied for each patient. Non-conventional laboratory tests need to be standardized and included for studying possible defects in the regulation of TF and/or plasmin pathways that can be involved in very rare mild bleeding phenotypes. TFPI inhibition might emerge as a good therapy for some of these patients. Failure to detect the bleeding cause in some of these patients, suggests the need to perform further studies in this field. This work was supported by Novo Nordisk Pharma S.A. Table 1- Thrombin and plasmin generation and TFPI activity in samples of patients with UBD. Results out of normal range are shown in red. LT: lagtime; ETP: endogenous thrombin potential; EPP: endogenous plasmin potential; TFPI: Tissue factor pathway inhibitor. Figure 1 Figure 1. Disclosures Alvarez Román: Grifols: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; CSL-Behring: Consultancy, Honoraria, Research Funding; Biomarin: Consultancy, Honoraria, Research Funding; Novo-Nordisk: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Sobi: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding. Martín: Novo Nordisk: Speakers Bureau; Pfizer: Speakers Bureau. Jiménez-Yuste: F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; BioMarin: Consultancy; Takeda: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Sobi: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding. Canales: Eusa Pharma: Consultancy, Honoraria; Sandoz: Honoraria, Speakers Bureau; Sanofi: Consultancy; Karyopharm: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Incyte: Consultancy; Gilead/Kite: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; iQone: Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria. Butta: Novo-Nordisk: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Roche: Speakers Bureau; CSL-Behring: Research Funding.

scholarly journals Novel Thermostable Inhibitor of Contact Activation Tica Effectively Blocks Contact Activation in Low Tissue Factor Thrombin Generation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1146-1146
Author(s):  
Tom Van De Berg ◽  
Dennis P.L. Suylen ◽  
M.G.L. Christella D. Thomassen ◽  
Rene van Oerle ◽  
Henri M.H. Spronk ◽  
...  
Keyword(s):  
Shelf Life ◽  
Tissue Factor ◽  
Trypsin Inhibitor ◽  
Thrombin Generation ◽  
Conflicts Of Interest ◽  
Blood Collection ◽  
Contact Activation ◽  
Current Standard ◽  
Blood Drawing ◽  
Corn Trypsin Inhibitor

Background: Thrombin generation and other clotting assays suffer from a wide variation of pre-analytical variables. One of those pre-analytical variables is contact activation through blood withdrawal methods, different syringes, differences in blood coagulation tubes, blood transport and sample handling. It has been shown that the addition of contact activation inhibitors in low tissue factor activated thrombin generation leads to a correction of the, in these circumstances significant, increase in thrombin generation due to contact activation. We compare the novel 'thermostable inhibitor of contact activation' (TICA) to the current standard 'corn trypsin inhibitor' (CTI). Aim: Comparing the effectiveness of novel contact activation inhibitor TICA to the current standard CTI in low tissue factor-induced thrombin generation and recalcification in sodium citrate anticoagulated platelet poor plasma (PPP) and platelet rich plasma (PRP). Methods: We compared TICA, Corn trypsin inhibitor and plasma without contact activation inhibitors in low tissue factor PPP thrombin generation and in PRP recalcification thrombin generation, the latter the most sensitive condition for contact activation. In addition, we compared low tissue factor activated thrombin generation in plasma from severe hemophilia A patients with and without TICA during and after blood drawing. Thermostability - as a measure of shelf life - was measured and compared to CTI. Results: TICA is able to fully block contact activation in PRP recalcification experiments and is comparable to CTI in doing so. TICA significantly lowers low tissue factor induced thrombin generation by blocking contact activation. Pre-loading vacuum blood collection tubes with contact activation inhibitors is superior in inhibiting contact activation compared to addition of the inhibitor during the thrombin generation assay itself. TICA did not alter coagulation activity when added to FXIIa deficient plasma in thrombin generation. In contrast to CTI TICA is heat stable which will be of benefit to shelf life of pre-loaded blood drawing tubes. Conclusion: TICA is able to fully block contact activation and has several advantages over CTI. Disclosures No relevant conflicts of interest to declare.

The technique of measuring thrombin generation with fluorogenic substrates: 3. The effects of sample dilution

2009 ◽  
Vol 101 (01) ◽  
pp. 165-170 ◽  
Author(s):  
Rob Wagenvoord ◽  
Coen Hemker ◽  
Erik De Smedt
Keyword(s):  
Tissue Factor ◽  
Thrombin Generation ◽  
Protein S ◽  
Generation Process ◽  
Contact Activation ◽  
Dependent Inhibition ◽  
Negative Effect ◽  
High Dilutions ◽  
Viii And Ix ◽  
Anticoagulant System

SummaryAssessing the clotting function inevitably brings about dilution of plasma. With the existing techniques of thrombin generation (TG) measurement, dilution ranges from 2:3 to 1:8. However, the possibility that dilution alters procoagulant and anticoagulant pathways differently has not been examined. We investigated the effects of dilution on the thrombin generation process and found that the anticoagulant pathways are far more affected by dilution than the procoagulant pathways. That is, when prothrombin and antithrombin concentrations are kept constant, dilution of plasma does not significantly affect tissue factor (TF)-driven thrombin generation. We demonstrate that dilution of plasma slows down the inhibitory activity of tissue factor pathway inhibitor (TFPI) to a greater extent when compared with the down regulation by diluting procoagulant factors. Dilution of plasma has also a negative effect on the participation of the anti-haemophiliac factors VIII and IX in TG driven by contact activation or low TF concentration. We also investigated the effect of dilution on the participation of the anticoagulant system that consists of thrombomodulin, protein C and protein S (APC system). We found that plasma dilution causes a loss of sensitivity towards TM and APC. Furthermore, at high dilutions (> 1:12) a second wave of prothrombinase-activity was observed that could be attributed to the suppression of protein S-dependent inhibition. In conclusion, the mechanism of TG is profoundly disturbed by plasma dilution. As a consequence, the less a plasma sample is diluted, the better a TG experiment represents the physiological process.

scholarly journals In Covid-19 Infection, Plasma Extracellular Vesicle Tissue Factor Activity Does Not Correlate with D-Dimer Levels

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1045-1045
Author(s):  
Thomas J. Girard ◽  
Irem Eldem ◽  
Kenneth E Remy ◽  
Monty Mazer ◽  
Jorge Di Paola
Keyword(s):  
Tissue Factor ◽  
Disease Severity ◽  
Trypsin Inhibitor ◽  
Thrombin Generation ◽  
Sample Collection ◽  
Contact Activation ◽  
Heparin Treatment ◽  
Significant Difference ◽  
D Dimer ◽  
Corn Trypsin Inhibitor

Abstract Objective: Identify a plasma-based activity, or biomarker, that defines the mechanism(s) by which Covid-19 disease triggers excessive coagulation. Introduction: While acute respiratory syndrome is the fundamental feature of severe Covid-19 disease, having a high level of the coagulation biomarker D-dimer upon admission is associated with increased thrombosis and mortality. As such, hospitalized patients are often placed on anticoagulant heparins. How Covid-19 triggers excessive coagulation is unresolved. Sars-CoV-2 infection could expose existing tissue factor (TF) to blood or, via cytokines, induce TF expression on cells that are in direct contact with blood. Extracellular vesicles (EV) are lipid bound microparticles released by all types of healthy and damaged cell and Covid-19 patient plasma EV TF activity has been recently reported. Cellular activation and damage due to SARS-CoV-2 could also release polyanionic nucleic acids and polyphosphates and generate neutrophil extracellular traps as contact surfaces for clot formation. Methods: Study 1. We attempted to identify excessive coagulation pathway activities in Covid-19 plasma-based, Ca++-induced thrombin generation assays. Assays were performed in the absence and presence of selective extrinsic (TF) and intrinsic (contact activation) pathway inhibitors (n=296 plasma samples). D-dimer levels were also determined. In a smaller study, Covid-19 patient samples were collected directly into citrate or citrate plus corn trypsin inhibitor, then processed for analysis. Study 2. We conducted studies to evaluate the extent to which EV TF activity contributes to the Covid-19-associated coagulopathies. Plasma EVs were isolated and EV TF activity determined by the difference in FXa activity in the absence vs presence of anti-TF antibody. D-dimer and tissue factor pathway inhibitor a (TFPIa) antigen levels were measured. Data from 232 samples collected from 96 Covid-19 positive patients and 18 samples from 14 healthy controls were analyzed. For each study analysis, patient samples were organized into groups based on the disease severity outcomes as follows: hospitalization (Hospitalization; n=37); intensive care (ICU; n=16); mechanical ventilation (Ventilation; n=22); or fatality (Deceased; n=22). Result: Study 1. Covid-19 samples showed considerable thrombin generation variability with some samples failing to generate thrombin; pathway selective inhibitors reduced thrombin generation while heparinase treatment increased thrombin generation. Upon analysis, thrombin generation parameters showed no significant correlations to either D-dimer levels or disease severity. Instead, plasma prepared from blood collected directly into corn trypsin inhibitor revealed that contact activation that occurred post-sample collection dominates procoagulant activity. Study 2. Figure 1, shows EV TF activities, D-dimer and TFPIα levels obtained for Covid-19 samples, with data segregated based on disease severity outcomes. Statistically significant difference versus the Hospitalized group are shown. TFPIa levels were highest in heparin IV patients (24.4+1.5 nM) vs Heparin-SQ (12.8+0.9 nM) vs enoxaparin (10.8 +0.7 nM) (p value:<0.0001). It is known that heparin treatment increases circulating TFPIα, however an increase in TFPIα might also further increase circulating TF/FVIIa/XaTFPI inhibitory complex, which would dissociate in citrated plasma, and might account for the increase in EV TF in other studies. Conclusions: Contact activation that occurs post-sample collection is sufficient to obscure endogenous triggers of coagulation, if present, in Covid-19 patients' plasma. D-dimer and TFPIα strongly correlate with disease severity although the latter is likely affected by heparin treatment. The most severe Covid-19 patients with high D-dimer did not show detectible plasma EV TF activity. Plasma EV TF activity does not appear to adequately represent the mechanism responsible for elevated D-dimer levels in Covid-19 cases. Figure 1 Figure 1. Disclosures Di Paola: CSL Behring: Consultancy, Honoraria.

Tissue Factor Pathway Inhibitor Mediates Attenuation of Tissue Factor-Stimulated Thrombin Generation in Early Onset Preeclampsia

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1431-1431
Author(s):  
Karl Egan ◽  
Hugh O'Connor ◽  
Barry Kevane ◽  
Fergal Malone ◽  
Amani Al Zadjali ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Early Onset ◽  
Research Funding ◽  
Thrombin Generation ◽  
Tissue Factor Pathway Inhibitor ◽  
Inflammatory Disorder ◽  
Contact Activation ◽  
Thrombotic Risk ◽  
Tissue Factor Pathway ◽  
Early Onset Preeclampsia

Abstract Introduction Pregnancy increases the risk of venous thromboembolism (VTE) in women. Interestingly, preeclampsia, an extremely pro-inflammatory disorder specific to pregnancy is associated with a lower than expected increase in thrombotic risk compared to other proinflammatory disorders. The mechanism underling this lower thrombotic risk is unknown. The aim of this study was to investigate the coagulation balance, a major determinant of VTE risk, in early onset preeclampsia (EOP) patients. EOP is the most inflammatory form of preeclampsia, characterised by the development of hypertension and proteinuria prior to 34 weeks gestation. Methods Platelet-poor plasma was collected from patients with early onset preeclampsia (EOP n=26), matched pregnant (n=20) and non pregnant controls (n=16). Calibrated automated thrombography, an assay of thrombin generation and TFPI assays were performed. Data are expressed as mean ± standard deviation. Results During the study period, 15,299 women delivered and 40 patients developed EOP, of whom 26 were successfully recruited with consent. For comparison, 16 non pregnant controls and 20 pregnant controls were also recruited. When artefactual contact activation was inhibited by using corn trypsin inhibitor as anticoagulant, EOP patients were characterised by a decrease in the rate and extent of Tissue Factor (TF) thrombin generation compared to pregnant controls. There was a prolongation of the time to peak thrombin generation (16 ± 4 minutes vs. 13 ± 2 minutes, p < 0.05), a decrease in the velocity index (25 ± 17nM/minute vs. 41 ± 27nM/minute, p < 0.05), and a decrease in peak thrombin generation (150 ± 80 nM IIa vs. 210 ± 70 nM IIa, p < 0.05 ) in EOP compared to pregnant controls. This reduction in the rate and extent of thrombin generation was most amplified in patients with severe EOP (multi-organ involvement) compared with moderate EOP. This lower overall procoagulant state seen was further emphasised by the increase in sensitivity to the anticoagulant activity of exogenously added activated protein C and thrombomodulin observed in EOP. Again, the increased sensitivity to APC and thrombomodulin was most apparent in severe EOP cases. Previous studies have shown that preeclampsia is characterised by a increase in plasma TFPI activity. As such, we investigated whether increases in plasma TFPI activity explained the reduction in TF-dependent thrombin generation. Consistent with previous studies, plasma tissue factor pathway inhibitor (TFPI) levels and plasma TFPI activity significantly increased in EOP, most notably in severe EOP cases. There was a significant inverse correlation between total TFPI levels and peak thrombin generation (r2 = -0.64, p < 0.05) and TFPI activity and peak thrombin generation (r2= -0.52, p < 0.05). The inhibition of TFPI with a polyclonal anti-TFPI antibody abolished the attenuation in thrombin generation seen in severe EOP. Conclusion In conclusion, TF-dependent thrombin generation is reduced in patients with early onset preeclampsia due to increases in plasma TFPI activity. These findings may partially explain the lower thrombosis risk observed in patients with early onset preeclampsia relative to comparable systemic proinflammatory conditions. These data also have future potential in helping clinicians to manage competing bleeding and thrombotic risks in these very high-risk patients. Disclosures Maguire: Actelion UK: Research Funding. Ní Áinle:Actelion UK: Research Funding.

The Effect of Active Site-inhibited Factor VIIa on Tissue Factor-initiated Coagulation Using Platelets before and after Aspirin Administration

1997 ◽  
Vol 78 (04) ◽  
pp. 1202-1208 ◽  
Author(s):  
Marianne Kjalke ◽  
Julie A Oliver ◽  
Dougald M Monroe ◽  
Maureane Hoffman ◽  
Mirella Ezban ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Active Site ◽  
Large Scale ◽  
Thrombin Generation ◽  
Factor Viia ◽  
Dependent Manner ◽  
Antithrombotic Agent ◽  
Before And After ◽  
Ic50 Values

SummaryActive site-inactivated factor VIIa has potential as an antithrombotic agent. The effects of D-Phe-L-Phe-L-Arg-chloromethyl ketone-treated factor VIla (FFR-FVIIa) were evaluated in a cell-based system mimicking in vivo initiation of coagulation. FFR-FVIIa inhibited platelet activation (as measured by expression of P-selectin) and subsequent large-scale thrombin generation in a dose-dependent manner with IC50 values of 1.4 ± 0.8 nM (n = 8) and 0.9 ± 0.7 nM (n = 7), respectively. Kd for factor VIIa binding to monocytes ki for FFR-FVIIa competing with factor VIIa were similar (11.4 ± 0.8 pM and 10.6 ± 1.1 pM, respectively), showing that FFR-FVIIa binds to tissue factor in the tenase complex with the same affinity as factor VIIa. Using platelets from volunteers before and after ingestion of aspirin (1.3 g), there were no significant differences in the IC50 values of FFR-FVIIa [after aspirin ingestion, the IC50 values were 1.7 ± 0.9 nM (n = 8) for P-selectin expression, p = 0.37, and 1.4 ± 1.3 nM (n = 7) for thrombin generation, p = 0.38]. This shows that aspirin treatment of platelets does not influence the inhibition of tissue factor-initiated coagulation by FFR-FVIIa, probably because thrombin activation of platelets is not entirely dependent upon expression of thromboxane A2.

scholarly journals Procoagulant activity in patients with combined type 2 diabetes and coronary artery disease: No effects of long-term exercise training

2017 ◽  
Vol 14 (2) ◽  
pp. 144-151 ◽  
Author(s):  
Vibeke Bratseth ◽  
Rune Byrkjeland ◽  
Ida U Njerve ◽  
Svein Solheim ◽  
Harald Arnesen ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Exercise Training ◽  
Tissue Factor ◽  
Thrombin Generation ◽  
Tissue Factor Pathway Inhibitor ◽  
Ex Vivo ◽  
Tissue Factor Pathway ◽  
Artery Disease ◽  
Total Tissue

We investigated the effects of 12-month exercise training on hypercoagulability in patients with combined type 2 diabetes mellitus and coronary artery disease. Associations with severity of disease were further explored. Patients ( n = 131) were randomized to exercise training or a control group. Blood was collected at inclusion and after 12 months. Tissue factor, free and total tissue factor pathway inhibitor, prothrombin fragment 1 + 2 (F1 + 2) and D-dimer were determined by enzyme-linked immunosorbent assay and ex vivo thrombin generation by the calibrated automated thrombogram assay. Tissue factor and ex vivo thrombin generation increased from baseline to 12 months ( p < 0.01, all), with no significant differences in changes between groups. At baseline, free and total tissue factor pathway inhibitor significantly correlated to fasting glucose ( p < 0.01, both) and HbA1c ( p < 0.05, both). In patients with albuminuria ( n = 34), these correlations were strengthened, and elevated levels of D-dimer, free and total tissue factor pathway inhibitor ( p < 0.01, all) and decreased ex vivo thrombin generation ( p < 0.05, all) were observed. These results show no effects of exercise training on markers of hypercoagulability in our population with combined type 2 diabetes mellitus and coronary artery disease. The association between poor glycaemic control and tissue factor pathway inhibitor might indicate increased endothelial activation. More pronounced hypercoagulability and increased tissue factor pathway inhibitor were demonstrated in patients with albuminuria.

scholarly journals Heparin is more effective than apixaban in inhibiting in vitro contact activated coagulation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
M.M Engelen ◽  
C Van Laer ◽  
M Jacquemin ◽  
C Vandenbriele ◽  
K Peerlinck ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Heart Valves ◽  
Thrombus Formation ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Mechanical Heart Valves ◽  
Contact Activation

Abstract Introduction Contact of blood with artificial surfaces such as mechanical support devices, catheters, and mechanical heart valves activates the contact activation (CA) pathway of coagulation. Furthermore, recent animal data and clinical studies suggest a more important contribution of CA in pathological thrombus formation in other cardiovascular diseases. Direct oral anticoagulants (DOACs) are recommended as first-line treatment in most patients who require long-term anticoagulation. However, because DOACs directly inhibit a single downstream coagulation factor (thrombin (fXIIa) or factor Xa (fXa)), it has been suggested that their efficacy could be reduced in the presence of strong activation of the CA pathway as compared to anticoagulants that target multiple, more upstream located coagulation factors. Purpose To compare the efficacy of a DOAC (apixaban) and heparin to suppress thrombin generation in the presence of strong CA pathway activation. Methods Pooled platelet-poor plasma was spiked with either apixaban (dissolved in DMSO and PBS) or unfractionated heparin to achieve therapeutic plasma levels. SynthASil, a commercially available mixture of phospholipids and silica, was used to stimulate the CA pathway in two different dilutions (1–80 and 5–80). Downstream coagulation was accessed by Thrombin Generation Test using Thrombinoscope by Stago and associated Thrombin Calibrator (activity 640 nM). The endogenous thrombin potential (area under the thrombin generation curve; ETP), peak thrombin generation (PTG), time to peak (ttPeak) and time to start (ttStart) were accessed. Results With decreasing concentrations of apixaban, stimulation with the lower dose SynthASil reveals an increasing ETP and PTG. As expected, ttPeak and ttStart decreased. Even supratherapeutic levels of apixaban (i.e. 1120 ng/mL) could not inhibit thrombin from being generated, in striking contrast with UFH where no thrombin was formed. Using a five times higher dose of SynthASil showed comparable ETP for all concentrations of apixaban, allocated around the control value. PTG, however, slightly increased with decreasing concentrations of apixaban. ttPeak and ttStart slightly decreased. Except for the subtherapeutic UFH concentration of 0,114 IU/mL, no thrombin was generated with UFH. Conclusion UFH is more effective in inhibiting downstream thrombin generation compared to apixaban as a response to activation of the CA pathway in vitro. These findings could help explain why direct inhibitors were not able to show non-inferiority in patients with mechanical heart valves and support the development of specific CA pathway inhibitors for patients with conditions that activate the CA pathway. Thrombin generation curves Funding Acknowledgement Type of funding source: None

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