Are coagulation profiles in Andean highlanders with excessive erythrocytosis favouring hypercoagulability?

Chronic mountain sickness is a maladaptive syndrome that affects individuals living permanently at high altitude and is characterized primarily by excessive erythrocytosis (EE). Recent results concerning the impact of EE in Andean highlanders on clotting and the possible promotion of hypercoagulability, which can lead to thrombosis, were contradictory. We assessed the coagulation profiles of Andeans highlanders with and without excessive erythrocytosis (EE+ and EE-). Blood samples were collected from 30 EE+ and 15 EE- in La Rinconada (Peru, 5100-5300 m a.s.l.), with special attention given to the sampling pre-analytical variables. Rotational thromboelastometry tests were performed at both native and normalized (40%) haematocrit using autologous platelet-poor plasma. Thrombin generation, dosages of clotting factors and inhibitors were measured in plasma samples. Data were compared between groups and with measurements performed at native haematocrit in 10 lowlanders (LL) at sea level. At native haematocrit, in all rotational thromboelastometry assays, EE+ exhibited hypocoagulable profiles (prolonged clotting time and weaker clot strength) compared with EE- and LL (all P < 0.01). At normalized haematocrit, clotting times were normalized in most individuals. Conversely, maximal clot firmness was normalized only in FIBTEM and not in EXTEM/INTEM assays, suggesting abnormal platelet activity. Thrombin generation, levels of plasma clotting factors and inhibitors, and standard coagulation assays were mostly normal in all groups. No highlanders reported a history of venous thromboembolism based on the dedicated survey. Collectively, these results indicate that EE+ do not present a hypercoagulable profile potentially favouring thrombosis.

Using Nonheparin Anticoagulant to Treat a Near-Fatal Case With Multiple Venous Thrombotic Lesions During ChAdOx1 nCoV-19 Vaccination-Related Vaccine-Induced Immune Thrombotic Thrombocytopenia.

OBJECTIVES: To describe the successful recovery from multiple and life-threatening venous thrombosis after ChAdOx1 nCoV-19 vaccination. DESIGN: Case report. SETTING: University Hospital. PATIENT: Few days after the first dose of the ChAdOx1 nCoV-19 vaccine, a 21-year-old woman experienced massive thrombosis in the deep and superficial cerebral veins together with seizures, neurologic focal deficit, and thrombocytopenia. In the neurointensive care unit, her condition worsened despite early decompressive craniectomy. She developed bilateral segmental pulmonary embolism, left hepatic, and left external iliac venous thrombosis. INTERVENTION: Argatroban (0.5-2.2 µg/kg/min) and high-dose IV immunoglobulin (1 g/kg/d for 2 consecutive days) were initiated on day 6 after admission. With these therapies, there was a gradual resolution of multiple sites of venous thrombosis, and platelet count returned to normal. The patient left the ICU with full consciousness, expressive aphasia, and right hemiparesis. CONCLUSIONS: This case of vaccine-induced immune thrombotic thrombocytopenia shows that a good outcome can be obtained even with multiple and life-threatening venous thrombotic lesions. Argatroban and high-dose IV immunoglobulin along with management of severe cerebral venous thrombosis played a major role in this epilogue.

Fibrinogen reconstitution after therapeutic apheresis: Comparison of double-filtration plasmapheresis, plasma exchange, and immunoadsorption.

BACKGROUND: Fibrinogen reconstitution after therapeutic apheresis has been poorly studied. Apheresis modalities, for example, plasma exchange (PE), double-filtration plasmapheresis (DFPP), or selective immunoadsorption (IA), may have different impacts. METHODS: We retrospectively investigated therapeutic apheresis sessions performed at our center across four modalities (PE, DFPP, and IA with or without plasma filtration). Fibrinogen levels were assessed at the beginning and end of each apheresis session, and immediately before the subsequent session. We adjusted measurements on hematocrit values to account for hemoconcentration. RESULTS: Between January 10, 2016 and March 2, 2020, we included 90 patients for a total of 754 apheresis sessions (PE: 35; DFPP: 351; IA only: 109; IA + plasma filtration: 259). Each patient received a median of five sessions (1Q 3; 3Q 9); median plasma volume treated was 5.5 L (1Q 4.3 L; 3Q 7.0 L). Within a session, DFPP and PE induced a significantly greater depletion of fibrinogen than both IA modalities, even after adjustment for the treated plasma volume. Median fibrinogen reconstitution was 0.8 (0.4-1.2) g/L (median time between sessions: 38 hours). In multivariate analysis, fibrinogen reconstitution was significantly associated with intersession time (+0.66 g/L/log-hour P < .001), apheresis modality (ANOVA; P < .001), initial fibrinogen concentration (+0.15 g/L per gram of fibrinogen; P < .001), and the last fibrinogen concentration from the previous apheresis session (-0.14 g/L per gram of fibrinogen; P < .001). In a model that considered hemoconcentration, the results were unchanged. CONCLUSIONS: We demonstrate that fibrinogen reconstitution was highly variable between patients and apheresis sessions. Apheresis modalities had a significant impact on fibrinogen reconstitution, regardless of hemoconcentration.

How to improve clotting factors depletion in double-filtration plasmapheresis.

BACKGROUND: Double-filtration plasmapheresis (DFPP), a selective therapeutic apheresis, can deplete pathogenic antibodies/substances, but also important coagulation factors. AIM: To determine if the use of a separator filter with different characteristics (CascadefloEC-50 W) as compared to the reference filter (PlasmafloOP-08 W) is as efficient in terms of immunoglobulin loss, but can reduce coagulation factor losses and have similar tolerability. PATIENTS/METHODS: This is a single-center prospective study including 14 patients divided into two groups (7 each): that is, group1 = CascadefloEC-50 W and group2 = PlasmafloOP-08 W. We measured immunoglobulins, lipid profiles, blood-cell counts, hemostasis (prothrombin time, activated partial thromboplastin time), coagulation factors, and natural anticoagulants at before and after the first DFPP-session. RESULTS: In group 1, the loss of coagulation factors was significantly reduced as compared to group 2 for proteins with a molecular weight of >150 kDa: there was, respectively, an average decrease of 70% vs 31% for fibrinogen (P = 0.004), 66% vs 21% for factor V (P = 2.16e-07), 60% vs 32% for factor XI (P = 6.96e-06), 75% vs 17% for XIII-antigen (P = 0.0002), and 47% vs 0% for VWF-antigen(P = 0.02). The decrease in post-session IgG was, on average, 45% in group 1 and 50% in group 2 (P = 0.13). Those results remained significant even when adjusted to the treated-plasma volume and the pre-DFPP factor values. CONCLUSION: DFPP, using a CascadefloEC-50W as a first-filter, reduces efficiently IgGs similarly to PlasmafloOP-08W but spares clotting factors.

Comparison of three modalities of plasmapheresis on coagulation: Centrifugal, single-membrane filtration, and double-filtration plasmapheresis.

BACKGROUND: Plasmapheresis can deplete pathogenic antibodies and allow ABO- and/or HLA-incompatible transplantation. AIM: To determine the impacts of three modalities of plasmapheresis (centrifugal plasmapheresis [cTPE], single-filtration plasmapheresis [mTPE], double-filtration plasmapheresis [DFPP]) on hemostasis parameters and thrombin generation. MATERIALS/METHODS: Prospective, comparative study on 21 patients that received three modalities of plasmapheresis (7 patients/group). Hemostasis (prothrombin time [PT], activated partial thromboplastin time [aPTT], procoagulant factors and natural anticoagulants) were measured before and after the first plasmapheresis session. Thrombin generation was also assessed in platelet-poor plasma using an STA-Genesia (Stago) analyzer and Thromboscreen reagents (Stago) in 4-5 patients from each group. RESULTS: Both cTPE and mTPE resulted in high decreases in proteins, whatever their molecular weights. Median post/pre ratios were 0.27 to 0.55 for cTPE for most proteins (except FVIII [0.64] and VWF [0.57]). Median post/pre-ratios of mTPE were 0.28 to 0.56 for all proteins. DFPP decreased high-molecular-weight proteins (fibrinogen, FV, FVIII, FXI, VWF) and proteins strongly bound to large molecules (protein SandTFPI). Median post/pre ratios with cTPE and mTPE were similar to DFPP for fibrinogen and FXIII. Regarding thrombin generation, cTPE and mTPE did not significantly modify endogenous thrombin potential (ETP) and DFPP induced a slight decrease in ETP (median post/pre ratio at 0.73) in the absence of thrombomodulin. ETP inhibition by thrombomodulin was decreased for all procedures. CONCLUSIONS: DFPP depleted high molecular-weight proteins in contrast to cTPE and mTPE, which significantly decreased all proteins. Regarding thrombin generation, depletion of procoagulant factors was counterbalanced by a decrease in some natural anticoagulants whatever plasmapheresis method used; with all methods, fibrinogen and FXIII were highly depleted.

Effect of immunoadsorption alone or combined with membrane filtration on hemostasis parameters.

INTRODUCTION: ABO- or HLA-incompatible kidney transplantation is possible thanks to pretransplant antibody-depletion achieved by extracorporeal-treatment modalities. These methods induce depletion of some plasma proteins and may also impact on proteins involved in hemostasis. METHODS: To determine the impact of one session of immunoadsorption (IA) alone or combined with membrane filtration (MF) on clotting factors and natural anticoagulants, we performed a prospective, observational study on 13 patients waiting for HLA-/ABO-incompatible kidney transplants. Plasma hemostasis parameters were measured before and immediately after a first session of IA alone in six patients and of IA + MF in seven patients. RESULTS: IA alone induced depletion of fibrinogen and factor XIII (FXIII) whereas IA + MF caused greater depletion of all high-molecular-weight hemostatic proteins (fibrinogen, FV, FVIII, FXI, FXIII, von-Willebrand factor [VWF]). After an IA session, median reductions were 30% for fibrinogen and 43% for FXIII compared to baseline values. After a session of IA + MF, median decreases were 70% for fibrinogen, 54% for FV, 56% for FVIII, 37% for FXI, 78% for FXIII, and 62% for VWF. Noticeably, levels of low-molecular-weight factors (<100 kDa) were far less decreased than high-molecular-weight proteins with IA + MF, except for protein S and the tissue factor pathway inhibitor, which are known to be partially physiologically bound to high-molecular-weight molecules. CONCLUSIONS: IA and IA + MF induced significant depletion of some proteins implicated in the hemostatic process; however, IA + MF resulted in stronger modifications to hemostasis parameters than IA alone. This may have potential clinical implications regarding bleeding risk, and particularly depletion of fibrinogen and FXIII.

Reducing Fibrinogen and Factor XIII Using Double-Filtration Plasmapheresis for Antibody-Mediated Rejection: Predictive Models.

BACKGROUND/AIMS: Antibody-mediated rejection (AMR) is related to circulating donor-specific anti-human leukocyte antigen alloantibodies (DSAs). DSAs can be removed by apheresis, for example, double-filtration plasmapheresis (DFPP). However, DFPP removes some clotting factors (fibrinogen and factor XIII [FXIII]). METHODS: This was a prospective trial including 6 DSA-mediated AMR kidney transplant recipients. Patients received 2 cycles of 3-4 consecutive DFPP sessions followed by 1 injection of rituximab (break of 4-5 days between the 2 cycles). We monitored fibrinogen and FXIII levels before and after each session of DFPP. RESULTS: Overall, fibrinogen and FXIII levels were significantly decreased after each session, and were significantly reduced between the very first and very last sessions. In addition, we established a model that predicted fibrinogen and FXIII values after each session and after 2 cycles. CONCLUSION: We established a model in order to predict fibrinogen and FXIII depletion after DFPP sessions; it may help clinicians supplement fibrinogen and/or FXIII when appropriate.

Antithrombin-independent effects of heparins on fibrin clot nanostructure.

OBJECTIVE: Because of the widespread clinical use of heparins, their effects on the enzymatic cascade are very well known. In contrast, little is known about the direct effect of heparins on the nanostructure of fibrin fibers, even though this nanostructure plays a major role in the mechanical strength and lysis of clots. This lack of reliable data can be correlated with the lack of a nonintrusive, quantitative method to determine this structure. We recently developed such a method that allows the simultaneous determination of the average fiber radius and the protein content using spectrometric data. In this study, we assessed the nanostructure of fibrin in a system composed of human thrombin and fibrinogen. METHODS AND RESULTS: We provide quantitative evidence showing that both unfractionated heparin and low molecular weight heparin directly alter the nanostructure of fibrin fibers independent of their other actions on the coagulation cascade; as expected, the pentasaccharide fondaparinux has no effect. CONCLUSIONS: Our results show that in addition to the effect of heparin on the coagulation cascade, modifications of the fibrin nanostructure may also contribute to improved fibrinolysis.

Cangrelor for cardiopulmonary bypass in delayed-onset heparin-induced thrombocytopenia: a case report.

Background: Anticoagulation for cardiopulmonary bypass (CPB) in cases of heparin-induced thrombocytopenia (HIT) is challenging as no convenient and proven alternative, such as heparin alone, exists. A "platelet anesthesia" concept using antiplatelet agent cangrelor with heparin has been successfully reported in this setting. Key Clinical Question: In cases of acute HIT, is CPB with cangrelor plus heparin effective and safe?. Clinical Approach: We report the case of a patient who developed, 2 weeks after patent foramen ovale (PFO) closure, a delayed-onset HIT complicated with carotid, popliteal, and PFO device thromboses that could not be controlled by argatroban anticoagulation and required urgent cardiac surgery. CPB for PFO occluder removal and popliteal thrombectomy were performed using cangrelor with heparin without complication. Neither a new thromboembolic event nor abnormal bleeding was noticed in the postoperative period. Conclusion: CPB using cangrelor with heparin seems to be an effective alternative for acute HIT.

Toward non-factor therapy in hemophilia: an antithrombin insensitive Gla-domainless factor Xa as tissue factor pathway inhibitor bait.

Background: Gla-domainless factor (F) Xa (GD-FXa) was proposed as a trap to endogenous anticoagulant tissue factor pathway inhibitor (TFPI) to restore thrombin generation in hemophilia. Using computational chemistry and experimental approaches, we previously showed that S195A GD-FXa also binds TFPI and restores ex vivo coagulation in plasma obtained from person(s) with hemophilia. Methods: To design a GD-FXa variant with improved anti-TFPI affinity, we performed molecular dynamics simulations and identified suitable sites for mutagenesis. The calculations identified residues R150FXa and K96Fxa as cold-spots of interaction between GD-FXa and the K2 domain of TFPI. In the three-dimensional model, both residues face toward TFPI hydrophobic residues and are thus potential candidates for mutagenesis into hydrophobic residues to favor an improved protein-protein interaction. Results: Catalytically inactive GD-FXa variants containing the S195A mutation and the additional mutations K96Y, R150I, R150G, R150F, and K96YR150F, were produced to experimentally confirm these computational hypotheses. Among these mutants, the R150FFXa and the K96YR150FFXa were slightly more effective than S195A GD-FXa in restoring coagulation in FVIII deficient plasmas. However, in surface plasmon resonance experiments, they showed TFPI binding affinities in the same range and acted similarly as S195A GD-FXa in FXa/TFPI competition assays. In contrast, the R150 mutants completely lost their interactions with antithrombin as observed in the surface plasmon resonance experiments. Conclusions: We therefore conclude that their antithrombin resistance is responsible for their improved thrombin generation, through an extension of their half-lives.

Lack of the human choline transporter-like protein SLC44A2 causes hearing impairment and a rare red blood phenotype.

Blood phenotypes are defined by the presence or absence of specific blood group antigens at the red blood cell (RBC) surface, due to genetic polymorphisms among individuals. The recent development of genomic and proteomic approaches enabled the characterization of several enigmatic antigens. The choline transporter-like protein CTL2 encoded by the SLC44A2 gene plays an important role in platelet aggregation and neutrophil activation. By investigating alloantibodies to a high-prevalence antigen of unknown specificity, found in patients with a rare blood type, we showed that SLC44A2 is also expressed in RBCs and carries a new blood group system. Furthermore, we identified three siblings homozygous for a large deletion in SLC44A2, resulting in complete SLC44A2 deficiency. Interestingly, the first-ever reported SLC44A2-deficient individuals suffer from progressive hearing impairment, recurrent arterial aneurysms, and epilepsy. Furthermore, SLC44A2null individuals showed no significant platelet aggregation changes and do not suffer from any apparent hematological disorders. Overall, our findings confirm the function of SLC44A2 in hearing preservation and provide new insights into the possible role of this protein in maintaining cerebrovascular homeostasis.

Surgery in rare bleeding disorders: the prospective MARACHI study.

Background: Despite the wide use of bleeding scores and the reliability of clotting factor level measurement, bleeding risk stratification before surgery remains challenging in patients with rare inherited bleeding disorders. Objectives: This multicenter observational prospective study assessed in patients with rare coagulation factor deficiency, the perioperative hemostatic management choices by hemostasis experts and the bleeding outcomes after surgery. Methods: One hundred seventy-eight patients with low coagulation activity level (factor [F] II, FV, combined FV-FVIII, FVII, FX, or FXI <50%) underwent 207 surgical procedures. The bleeding outcome, Tosetto's bleeding score, and perioperative hemostatic protocols were collected. Results: Among the 81 procedures performed in patients with severe factor deficiency (level ≤10%), 27 were done without factor replacement (including 6 in patients at high bleeding risk), without any bleeding event. Factor replacement therapy was used mainly for orthopedic procedures. In patients with mild deficiency, 100/126 surgical procedures were carried out without perioperative hemostatic treatment. In patients with FVII or FXI deficiency, factor replacement therapy was in function of the procedure, bleeding risk, and to a lesser extent previous bleeding history. Tranexamic acid was used in almost half of the procedures, particularly in case of surgery in tissues with high fibrinolytic activity (76.8%). Conclusions: The current perioperative hemostatic management of patients with rare bleeding disorders appears to be adapted. Among the 207 procedures, only 6 were associated with excessive bleeding. Our findings suggest that rather than the bleeding score, factor level and surgery type are the most relevant criteria for perioperative factor replacement therapy.

C-reactive protein and D-dimer in cerebral vein thrombosis: Relation to clinical and imaging characteristics as well as outcomes in a French cohort study.

Introduction: Cerebral venous sinus thrombosis (CVST) is a rare disease with highly variable clinical presentation and outcomes. Clinical studies suggest a role of inflammation and coagulation in CVST outcomes. The aim of this study was to investigate the association of inflammation and hypercoagulability biomarkers with CVST clinical manifestations and prognosis. Methods: This prospective multicenter study was conducted from July 2011 to September 2016. Consecutive patients referred to 21 French stroke units and who had a diagnosis of symptomatic CVST were included. High-sensitivity C-reactive protein (hs-CRP), neutrophil-to-lymphocyte ratio (NLR), D-dimer, and thrombin generation using calibrated automated thrombogram system were measured at different time points until 1 month after anticoagulant therapy discontinuation. Results: Two hundred thirty-one patients were included. Eight patients died, of whom 5 during hospitalization. The day 0 hs-CRP levels, NLR, and D-dimer were higher in patients with initial consciousness disturbance than in those without (hs-CRP: 10.2 mg/L [3.6-25.5] vs 23.7 mg/L [4.8-60.0], respectively; NLR: 3.51 [2.15-5.88] vs 4.78 [3.10-9.59], respectively; D-dimer: 950 µg/L [520-2075] vs 1220 µg/L [950-2445], respectively). Patients with ischemic parenchymal lesions (n = 31) had a higher endogenous thrombin potential5pM than those with hemorrhagic parenchymal lesions (n = 31): 2025 nM min (1646-2441) vs 1629 nM min (1371-2090), respectively (P = .0082). Using unadjusted logistic regression with values >75th percentile, day 0 hs-CRP levels of >29.7 mg/L (odds ratio, 10.76 [1.55-140.4]; P = .037) and day 5 D-dimer levels of >1060 mg/L (odds ratio, 14.63 [2.28-179.9]; P = .010) were associated with death occurrence. Conclusion: Two widely available biomarkers measured upon admission, especially hs-CRP, could help predict bad prognosis in CVST in addition to patient characteristics. These results need to be validated in other cohorts.

Gla-domainless factor Xa: molecular bait to bypass a blocked tenase complex.

BACKGROUND: Hemophilia is caused by deficiencies in coagulation factor VIII or IX, resulting in direct blockade of the intrinsic tenase complex and indirect blockade of the extrinsic tenase complex which is rapidly inhibited upon binding of factor Xa to tissue factor pathway inhibitor. We evaluated the ability of Gla-domainless factor Xa, a truncated form of factor Xa devoid of procoagulant properties, to bind to tissue factor pathway inhibitor and to alleviate the physiological inhibition of the extrinsic tenase. DESIGN AND METHODS: Using a thrombin generation assay triggered by a low concentration of tissue factor, we evaluated the ability of Gla-domainless factor Xa to restore blood coagulation in plasma from hemophilia A and B patients without and with inhibitors. We then compared its efficacy to generate thrombin to depletion of antithrombin or tissue factor pathway inhibitor by specific antibodies. Finally, we compared the kinetics of neutralization of factor Xa and Gla-domainless factor Xa by antithrombin and tissue factor pathway inhibitor. RESULTS: Gla-domainless factor Xa was able to restore thrombin generation in plasma samples from hemophiliacs. This effect was observed for plasma from hemophilia A patients without or with inhibitors and for plasma from hemophilia B patients. Gla-domainless factor Xa had a lower affinity than factor Xa for tissue factor pathway inhibitor whereas the affinities of both proteins for antithrombin were similar. Finally, despite a short half-life in plasma, the effect of Gla-domainless factor Xa on thrombin generation was sustained for at least 1 hour. CONCLUSIONS: As Gla-domainless factor Xa was able to restore thrombin generation in plasma from hemophilia patients, our results suggest that it may be an effective alternative to current treatments for hemophilia with or without an inhibitor.