Thrombin generation (TG) in the presence of thrombomodulin (TG-TM) in the plasma of patients with cirrhosis (PWC) is tilted toward a hypercoagulable phenotype. Low protein C and elevated factor VIII ...levels play a role, but other determinants, such as the prothrombin/antithrombin pair, must also be studied.
The objectives were (i) to quantitatively assess the subprocesses (prothrombin conversion and thrombin decay) and (ii) to understand the underlying mechanism by studying TG dynamics after prothrombin and antithrombin plasma level correction in PWC.
We studied TG-TM in plasma samples of 36 healthy controls (HCs) and 41 PWC with prothrombin and antithrombin levels of <70% and after their correction. We initiated coagulation with an intermediate picomolar concentration of tissue factor. We determined the overall thrombin potential, prothrombin conversion, and thrombin decay.
TG-TM was increased in PWC compared with HC due to impaired thrombin inhibition. Indeed, thrombin decay capacity (min
) decreased from 0.37 (0.35-0.40) in HC to 0.33 (0.30-0.37) in the Child-Turcotte-Pugh A (CTP-A; P = .09), 0.27 (0.26-0.30) in the CTP-B (P < .001), and 0.20 (0.19-0.20) in the CTP-C (P < .001) group. Concomitant correction of prothrombin and antithrombin increased endogenous thrombin potential with prothrombin conversion surpassing thrombin decay. By contrast, when we corrected only antithrombin, TG-TM was normalized and even consistent with a hypocoagulable phenotype in the CTP-C group.
Our results highlight that in PWC, hypercoagulability (evidenced in the presence of TM) is due to impaired thrombin decay, whereas low prothrombin levels do not translate into decreased prothrombin conversion, likely due to altered TM-activated protein C negative feedback.
Thrombin generation assays (TGAs) performed with calibrated automated thrombography (CAT) in the presence of thrombomodulin (TM) indicate plasma hypercoagulability in cirrhosis.
To evaluate, in the ...presence of TM, the new ST-Genesia automated device developed for improving TGA vs the previously used CAT method, with plasma samples of patients with cirrhosis.
Platelet-poor plasma samples were prepared from citrated blood samples of 52 healthy controls and 85 patients with cirrhosis (severity evaluated using the Child-Pugh score CP). TGAs were performed using CAT with PPP-Reagent and ST-Genesia with the STG-ThromboScreen reagent, in the presence of TM. Endogenous thrombin potential (ETP) was chosen as the main parameter.
Whatever the method, ETP values were higher in patients than in healthy controls. All patients identified as hypercoagulable with ST-Genesia and STG-ThromboScreen were found hypercoagulable with CAT and PPP-Reagent. Conversely, eight and ten patients in the CP-A and CP-B classes respectively were identified as hypercoagulable only with CAT. The use of ST-Genesia with the STG-ThromboScreen reagent with TM led to a bias, with higher ETP values for healthy controls and lower for patients compared with CAT. Crossover analysis (CAT with the STG-ThromboScreen reagent) evidenced a substantial effect of the STG-ThromboScreen reagent; the analyzer (including calibration and data analysis) plays a lesser role.
ST-Genesia evidences hypercoagulability in patients with cirrhosis when TG is studied in the presence of TM, but the results are not interchangeable with those obtained with CAT.
Fibrin clot structure and function are major determinants of thromboembolic diseases. The study aim was to determine the impact of epicatechin (a flavonoid with cardiovascular protective effects) on ...fibrin clot structure and permeability.
Plasma samples from 12 healthy subjects were incubated with increasing concentrations of epicatechin. Turbidity of fibrin clot was analyzed by absorbance measurement at 405 nm. The fibrin clot nanostructure was determined by scanning spectrometry (wavelength from 500 to 800 nm) and fibrin fiber size by electron microscopy. Permeability was analyzed to assess the fibrin clot functional properties.
Epicatechin addition increased the maximum absorbance from 0.34 ± 0.066 (vehicle) to 0.35 ± 0.077 (P = 0.1), 0.35 ± 0.072 (P < 0.05) and 0.34 ± 0.065 (P = 0.5) for 1, 10 and 100 μM epicatechin, respectively. Epicatechin increased the fibrin clot fiber radius (nm) from 109.2 ± 3.2 (vehicle) to 108.9 ± 4.3 (P = 0.9), 110.0 ± 3.6 (P < 0.05) and 109.5 ± 3.3 (P = 0.4), and the distance between protofibrils (nm) from 22.2 ± 1.5 (vehicle) to 22.1 ± 2.3 (P = 0.9), 22.6 ± 1.8 (P < 0.05) and 22.3 ± 1.8 (P = 0.9) for 1, 10 and 100 μM epicatechin respectively. Electron microscopy confirmed these changes. Fibrin clot permeability, expressed as Darcy's constant (Ks, cm2), increased from 2.97 ± 1.17 (vehicle) to 3.36 ± 1.21 (P < 0.05), 3.81 ± 1.41 (P < 0.01) and 3.38 ± 1.33 (P = 0.9).
Upon epicatechin addition, the fibrin clot structure became less dense and more permeable.
We conducted a multicenter study of 101 patients with congenital dysfibrinogenemia (CD) to characterize the incidence of hemorrhagic and thrombotic events as well as complications of pregnancy and ...surgery. At the time of diagnosis, 10.9% and 13.9% had experienced major bleeding and thrombotic events, respectively. During a mean follow-up of 8.8 years after CD diagnosis, the incidence of major bleeding and thrombotic events was 2.5 and 18.7 per 1000 patient-years, respectively, with estimated cumulative incidences at age 50 years of 19.2% and 30.1%. We identified 111 pregnancies with an overall incidence of spontaneous abortions and postpartum hemorrhage of 19.8% and 21.4%, respectively. The risk of postpartum hemorrhage was associated with a previously identified bleeding phenotype (odds ratio, 5.8; 95% CI, 1.2 to 28.0). Among 137 surgical procedures analyzed, 9 (6.5%) were complicated by abnormal bleeding. Propositi vs relatives, sex, mutation hotspots, fibrinogen levels, and activity:antigen ratios were not associated with the risk of thrombotic or bleeding outcomes. In conclusion, the results of our study, the largest in genotyped CD and the first including long-term history, indicate that propositi with CD and their relatives carry not only a high risk of major bleeding, including postpartum hemorrhage, but also of thrombotic event.
•Major bleeding, thrombosis, and postpartum hemorrhage are frequent in propositi and relatives with congenital dysfibrinogenemia.•Hotspot mutations were not predictive of either phenotype or outcome.
As of 4 April 2021, a total of 169 cases of cerebral venous sinus thrombosis (CVST) and 53 cases of splanchnic vein thrombosis were reported to EudraVigilance among around 34 million people ...vaccinated in the European Economic Area and United Kingdom with COVID-19 Vaccine AstraZeneca, a chimpanzee adenoviral vector (ChAdOx1) encoding the spike protein antigen of the SARS-CoV-2 virus. The first report of the European Medicines Agency gathering data on 20 million people vaccinated with Vaxzevria® in the UK and the EEA concluded that the number of post-vaccination cases with thromboembolic events as a whole reported to EudraVigilance in relation to the number of people vaccinated was lower than the estimated rate of such events in the general population. However, the EMA's Pharmacovigilance Risk Assessment Committee concluded that unusual thromboses with low blood platelets should be listed as very rare side effects of Vaxzevria®, pointing to a possible link. The same issue was identified with the COVID-19 Vaccine Janssen (Ad26.COV2.S).
Currently, there is still a sharp contrast between the clinical or experimental data reported in the literature on COVID-19 and the scarcity of data on the unusual thrombotic events observed after the vaccination with these vaccines. Different hypotheses might support these observations and should trigger further in vitro and ex vivo investigations. Specialized studies were needed to fully understand the potential relationship between vaccination and possible risk factors in order to implement risk minimization strategies.
•Vaxzevria® and COVID-19 Vaccine Janssen have been associated with rare case of thrombotic with thrombocytopenia syndrome.•Main mechanism explaining the risk involved antibodies directed against platelet factor 4.•Research of other physiopathological mechanisms has not been sufficiently investigated and should not be discarded.•There is a contrast between the clinical or experimental data on COVID-19 and the scarcity of data with these vaccines.•The benefits of these vaccines are well established and the risk-benefit balance remains largely positive.
Patients with cirrhosis are at high risk of thrombotic events, including portal vein thrombosis and venous thromboembolism. In such patients, hypercoagulability is not detected by conventional ...coagulation tests, but only by the thrombin generation assay (TGA) that integrates the role of pro- and anticoagulant factors. However, TGA use to predict clinical events depends on thrombin generation variability over time.
The aim of this study was to compare TGA intraindividual variability over time in patients with cirrhosis and in healthy controls.
Blood samples were prospectively collected from 34 healthy controls and 52 patients with cirrhosis at week 0 (inclusion), 6, and 12. TGA was performed with the calibrated automated thrombogram method, tissue factor (5 pM), phospholipids, and with and without thrombomodulin (4 nM) or activated protein C (1 nM).
When TGA was performed with thrombomodulin, endogenous thrombin potential in patients with cirrhosis was higher compared with controls and increased with cirrhosis severity. Stability over time of all thrombin generation parameters was excellent in healthy controls, good in Child-Turcotte-Pugh (CTP)-A patients, and poor in CTP-B/C patients (severe cirrhosis). In CTP-B/C patients, the phenotype was more variable because one-third of patients switched to normal or hypercoagulability during the 3-month follow-up.
A study with longer monitoring is needed to correlate the hypercoagulable phenotype of patients with cirrhosis with the occurrence of thrombotic events.
Summary
Acquired haemophilia A (AHA) is a rare haemorrhagic disease characterised by new‐onset haemorrhagic symptoms associated with a dramatic decrease in factor VIII levels and an anti‐factor VIII ...neutralising autoantibody concentration >0.6 Bethesda units. Elderly people are often affected, whereas children are rarely affected; the paediatric incidence reported in the literature is about 0.045 case/million/year. For some time, the paediatric standard of care has been that for adults, but clinicians have often reported poor outcomes. Here, we describe the largest retrospective paediatric AHA cohort assembled to date, including eight patients diagnosed in France from 2000 to 2020.
The different stages of hemostasis (i.e., primary hemostasis, coagulation and fibrinolysis) are involved in the early atherothrombosis steps. The aim of this study was to investigate the effect of ...epicatechin, a major flavonoid compound, on the hemostasis phenotype using clinically relevant in vitro global assays that mimic the complexity of the in vivo hemostasis systems. Plasma samples from 10 healthy volunteers were spiked with increasing concentrations of epicatechin (1 to 100 μM). Epicatechin effect on primary hemostasis, coagulation and fibrinolysis was assessed by measuring platelet aggregation using light transmission aggregometry, thrombin generation and clot lysis time (CLT), respectively. Epicatechin (100 μM) significantly decreased the maximal platelet aggregation induced by adenosine diphosphate (-39%), thrombin receptor activating peptide (-48%), epinephrine (-30%), and collagen (-30%). The endogenous thrombin potential was significantly reduced starting from 1 μM epicatechin (1332 ± 230 versus 1548 ± 241 nM min for control) (p < 0.01). Fibrinolysis was promoted by epicatechin, as indicated by CLT decrease by 16 and 33% with 10 and 100 μM epicatechin respectively, compared with control (1271 ± 775 s). These findings show that epicatechin reduces platelet function and leads to an anticoagulant and pro-fibrinolytic profile, providing new evidence of its interest for cardiovascular disease prevention.
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