Outcome of SARS-CoV-2 infection is linked to MAIT cell activation and cytotoxicity.

Immune system dysfunction is paramount in coronavirus disease 2019 (COVID-19) severity and fatality rate. Mucosal-associated invariant T (MAIT) cells are innate-like T cells involved in mucosal immunity and protection against viral infections. Here, we studied the immune cell landscape, with emphasis on MAIT cells, in cohorts totaling 208 patients with various stages of disease. MAIT cell frequency is strongly reduced in blood. They display a strong activated and cytotoxic phenotype that is more pronounced in lungs. Blood MAIT cell alterations positively correlate with the activation of other innate cells, proinflammatory cytokines, notably interleukin (IL)-18, and with the severity and mortality of severe acute respiratory syndrome coronavirus 2 infection. We also identified a monocyte/macrophage interferon (IFN)-α-IL-18 cytokine shift and the ability of infected macrophages to induce the cytotoxicity of MAIT cells in an MR1-dependent manner. Together, our results suggest that altered MAIT cell functions due to IFN-α-IL-18 imbalance contribute to disease severity, and their therapeutic manipulation may prevent deleterious inflammation in COVID-19 aggravation.

Thromboembolic events after major bleeding events in patients with mechanical heart valves: a 13-year analysis.

Anticoagulation in patients with mechanical heart valves (MHV) is associated with a risk of major bleeding episodes (MBE). In case of MBE, anticoagulant interruption is advocated. However, there is lack of data regarding the thrombo-embolic events (TE) risk associated with anticoagulant interruption. The main objective of the study was to evaluate the rate and risk factors of 6-months of TEs in patients with MHV experiencing MBE. This observational study was conducted over a 13-year period. Adult patients with a MHV presenting with a MBE were included. The main study endpoint was 6-month TEs, defined by clinical TEs or an echocardiographic documented thrombosis, occurring during an ICU stay or within 6-months. Thromboembolic events were recorded at ICU discharge, and 6 months after discharge. Seventy-nine MBEs were analysed, the rate of TEs at 6-months was 19% CI [11-29%]. The only difference of presentation and management between 6-month TEs and free-TE patients was the time without effective anticoagulation (TWA). The Receiver Operator Characteristic curve identified the value of 122 h of TWA as a cut-off. The multivariate analysis identified early bleeding recurrences (OR 3.62, 95% CI [1.07-12.25], p = 0.039), and TWA longer than 122 h (OR 4.24, 95% CI [1.24-14.5], p = 0.021), as independent risk factors for 6-month TEs. A higher rate of TE was associated with anticoagulation interruption longer than 5 days and early bleeding recurrences. However, the management should still be personalized and discussed for each case given the heterogeneity of causes of MBE and possibilities of haemostatic procedures.

Acquired factor V inhibitor: a nation-wide study of 38 patients.

Acquired factor V inhibitor (AFVI) is an extremely rare disorder that may cause severe bleeding. To identify factors associated with bleeding risk in AFVI patients, a national, multicentre, retrospective study was made including all AFVI patients followed in 21 centres in France between 1988 and 2015. All patients had an isolated factor V (FV) deficiency <50% associated with inhibitor activity. Patients with constitutional FV deficiency and other causes of acquired coagulation FV deficiencies were excluded. The primary outcome was incident bleeding and factors associated with the primary outcome were identified. Thirty-eight (74 [36-100] years, 42·1% females) patients with AFVI were analysed. Bleeding was reported in 18 (47·4%) patients at diagnosis and in three (7·9%) during follow-up (7 [0·2-48.7] months). At diagnosis, FV was <10% in 31 (81·6%) patients. Bleeding at diagnosis was associated with a prolonged prothrombin time that strongly correlated with the AFVI level measured in plasma {r = 0·63, 95% confidence interval (CI) [0·36-0·80], P < 0·05}. Bleeding onset during follow-up was associated with a slow AFVI clearance (P < 0·001). The corresponding receiver operating characteristics curve showed that AFVI clearance was predictive of bleeding onset with an AFVI clearance of seven months with a sensitivity of 100% (95% CI: 29-100) and a specificity of 86% (95% CI: 57-98, P = 0·02). Kaplan-Meier analysis showed that AFVI clearance >7 months increased the risk of bleeding by 8 (95% CI: [0·67-97], P = 0·075). Prothrombin time at diagnosis and time for clearance of FV inhibitor during follow-up are both associated with bleeding in patients with AFVI.

Absence of bleeding upon dual antiplatelet therapy in a patient with a immune GPVI deficiency.

Acquired deficiencies in platelet glycoprotein VI are rare and have not been found associated with other defects. Here we report the case of a 64-year old male patient presenting an immune GPVI deficiency associated to a mutation in the alpha-actinin gene and who has been treated with dual anti platelet therapy without bleeding.Introduction: Glycoprotein (GP) VI, a pluripotent receptor interacting with collagen and fibrin(ogen) is responsible for thrombus formation, growth and stability (1-4). It is co-expressed with the Fc receptor γ (FcRγ) chain (5). GPVI is not critical for haemostasis since subjects with a GPVI deficiency usually present low or even no bleeding tendency (6, 7). Acquired GPVI deficiency due to antibody-induced GPVI depletion is the most frequent finding. At least 10 patients have been described with an acquired GPVI deficiency, most often associated to immune thrombocytopenia, moderate bleeding and impaired collagen-induced platelet aggregation (7). Several mechanisms leading to the GPVI deficiency are proposed including antibody-triggered GPVI internalization and/or shedding of the extracellular domain (8, 9). We report the case of a patient presenting an acquired GPVI deficiency different from those previously described: (i) he is male whereas all previous cases were female, (ii) he is heterozygous for a mutation in α (alpha)-actinin-1 gene and (iii) he was treated with dual antiplatelet therapy with no haemorrhagic manifestation.

Critical role of neutrophil extracellular traps (NETs) in patients with Behcet's disease.

OBJECTIVES: Behçet's disease (BD) is a chronic systemic vasculitis. Thrombosis is a frequent and life-threatening complication. The pathogenesis of BD is poorly understood and evidence supporting a role for primed neutrophils in BD-associated thrombotic risk is scant. To respond to inflammatory insults, neutrophils release web-like structures, known as neutrophil extracellular traps (NETs), which are prothrombotic. We evaluated the role of NETs and markers of NETs in BD. METHODS: Blood samples were collected from patients with BD, according to the International Study Group Criteria for Behçet's disease, and healthy donors (HD). NET components, including cell-free DNA (CfDNA) and neutrophil enzymes myeloperoxidase (MPO), were assessed in serum or in purified neutrophils from patients with BD and HD. RESULTS: Patients with active BD had elevated serum cfDNA levels and MPO-DNA complexes compared with patients with inactive BD and to HD. In addition, levels of cfDNA and MPO-DNA complexes were significantly higher in patients with BD with vascular involvement compared with those without vascular symptoms. Purified neutrophils from patients with BD exhibited spontaneous NETosis compared with HD. Thrombin generation in BD plasma was significantly increased and positively correlated with the levels of MPO-DNA complexes and cfDNA. Importantly, DNAse treatment significantly decreased thrombin generation in BD plasma but not in HD plasma. In addition, biopsy materials obtained from patients with BD showed NETs production in areas of vasculitic inflammation and thrombosis. CONCLUSIONS: Our data show that NETs and markers of NETS levels are elevated in patients with BD and contribute to the procoagulant state. Targeting NETs may represent a potential therapeutic target for the reduction or prevention of BD-associated thrombotic risk.

How to Manage Thrombocytopenia with ECLS: A Proposal of Clinical Reasoning Tools.

Extracorporeal life support (ECLS) is increasingly used as a rescue therapy in patients with refractory cardiac/respiratory failure for temporary support or bridge to decision-making in both adult and pediatric patients. Complications such as bleeding and thrombosis remain major causes of morbidity and mortality in patients treated with ECLS. Hemostatic complications related to ECLS are multifactorial in patients with multiple organ dysfunctions and are incompletely characterized. Persisting thrombocytopenia and/or platelet dysfunction is the most frequent one. Herein, we report the case of a patient who developed severe thrombocytopenia after 5 days of ECLS associated with thrombi deposition in the circuit and oxygenator. After ECLS circuit and membrane change, we observed an increase and normalization in platelet count in 3 days. We propose a case-based reasoning to manage thrombocytopenia with ECLS.

Abacavir has no prothrombotic effect on platelets in vitro.

OBJECTIVES: HIV patients exposed to abacavir have an increased risk of myocardial infarction, with contradictory results in the literature. The aim of our study was to determine whether abacavir has a direct effect on platelet activation and aggregation using platelets from healthy donors and from HIV-infected patients under therapy with an undetectable viral load. METHODS: Platelet-rich plasma (PRP) or whole blood from healthy donors was treated with abacavir (5 or 10 µg/mL) or its active metabolite carbovir diphosphate. Experiments were also performed using blood of HIV-infected patients (n = 10) with an undetectable viral load. Platelet aggregation was performed on PRP by turbidimetry and under high shear conditions at 4000 s-1. Platelet procoagulant potential was analysed by measuring thrombin generation by thrombinography. RESULTS: Abacavir and carbovir diphosphate significantly increased the aggregation of platelets from healthy donors induced by collagen at 2 µg/mL (P = 0.002), but not at 0.5 µg/mL. No effect of abacavir or carbovir diphosphate was observed on platelet aggregation induced by other physiological agonists or by high shear stress, or on thrombin generation. Pretreatment of blood from HIV-infected patients with abacavir produced similar results. CONCLUSIONS: Our results suggest that abacavir does not significantly influence platelet activation in vitro when incubated with platelets from healthy donors or from HIV-infected patients. It is, however, not excluded that a synergistic effect with other drugs could promote platelet activation and thereby play a role in the pathogenesis of myocardial infarction.

Alteplase Reduces Downstream Microvascular Thrombosis and Improves the Benefit of Large Artery Recanalization in Stroke.

BACKGROUND AND PURPOSE: Downstream microvascular thrombosis (DMT) is known to be a contributing factor to incomplete reperfusion in acute ischemic stroke. The aim of this study was to determine the timing of DMT with intravital imaging and to test the hypothesis that intravenous alteplase infusion could reduce DMT in a transient middle cerebral artery occlusion (MCAO) rat stroke model. METHODS: Rats were subjected to 60-minute transient MCAO. Alteplase (10 mg/kg) was administered 30 minutes after the beginning of MCAO. Real-time intravital fluorescence microscopy through a dura-sparing craniotomy was used to visualize circulating blood cells and fibrinogen. Cerebral microvessel patency was quantitatively evaluated by fluorescein isothiocyanate-dextran perfusion. RESULTS: Immediately after MCAO, platelet and leukocyte accumulation were observed mostly in the venous compartment. Within 30 minutes after MCAO, microthrombi and parietal fibrin deposits were detected in postcapillary microvessels. Alteplase treatment significantly (P=0.006) reduced infarct volume and increased the percentage of perfused vessels during MCAO (P=0.02) compared with saline. Plasma levels of fibrinogen from alteplase-treated rats showed a rapid and profound hypofibrinogenemia. In vitro platelet aggregation demonstrated that alteplase reduced platelet aggregation (P=0.0001) and facilitated platelet disaggregation (P=0.001). These effects were reversible in the presence of exogenous fibrinogen. CONCLUSIONS: Our data demonstrate that DMT is an early phenomenon initiated before recanalization. We further show that alteplase-dependent maintenance of downstream perfusion during MCAO improves acute ischemic stroke outcome through a fibrinogen-dependent platelet aggregation reduction. Our results indicate that early targeting of DMT represents a therapeutic strategy to improve the benefit of large artery recanalization in acute ischemic stroke.

Von Willebrand factor, a versatile player in gastrointestinal bleeding in left ventricular assist device recipients?

BACKGROUND: Bleeding originating in the gastrointestinal (GI) tract is one of the most common adverse events after left ventricular assist device (LVAD) implantation. In these patients, GI bleeding appears to be the consequence of altered hemostasis on the one hand and alterations of the GI microvasculature on the other. CASE REPORT: We report the case of a patient who suffered repeated, severe GI bleeding early after implantation of a HeartMate II continuous-flow LVAD. RESULTS: After failure of conventional treatment strategies, GI bleeding was controlled using repeated transfusions of a purified von Willebrand factor (VWF) concentrate, almost devoid of Factor VIII (Wilfactin, LFB). No episodes of pump thrombosis were noted. Subsequent to VWF transfusions, we observed a progressive normalization of circulating vascular endothelial growth factor levels. CONCLUSIONS: Our data raise the possibility that, in addition to its hemostatic properties, transfusions of VWF might have acted as an antiangiogenic factor.

Impact of diabetes mellitus and metabolic syndrome on acute and chronic on-clopidogrel platelet reactivity in patients with stable coronary artery disease undergoing drug-eluting stent placement.

BACKGROUND: Previous studies, which compared the prevalence of high on-clopidogrel platelet reactivity (HCPR) in type 2 diabetes mellitus (T2DM) versus non-T2DM and obese versus nonobese patients provided conflicting results. METHODS: We compared the prevalence of HCPR in patients with T2DM, metabolic syndrome (MS), or neither T2DM nor MS undergoing drug-eluting stent implantation for stable coronary artery disease. Platelet functions were measured after a 600-mg clopidogrel loading dose and after 4 months on clopidogrel 75 mg/d. RESULTS: The prevalence of HCPR was significantly higher in 63 T2DM and 50 MS patients than in 43 patients with neither T2DM nor MS (46.0% and 52.0% vs 20.9%) after clopidogrel loading dose, whereas, at 4 months, only T2DM patients had a significantly higher prevalence of HCPR (50.8% and 31.3% vs 23.8%). By multivariable analysis, T2DM (odds ratio [OR] 3.62, 95% CI, 1.34-9.80, P = .011), MS (OR 4.00, 95% CI 1.39-11.46, P = .010), and previous chronic treatment with clopidogrel (OR 0.22, 95% CI 0.09-0.49; P < .001) were the main independent predictors of HCPR after clopidogrel loading dose, whereas only T2DM (OR 2.98, 95% CI 1.20-7.41, P = .017) was an important independent predictor of HCPR at 4 months. CONCLUSIONS: Both MS and T2DM were independent predictors of HCPR after clopidogrel loading dose. On clopidogrel maintenance therapy, only T2DM remained an independent predictor. This observation may be clinically relevant in the current era of antiplatelet therapy.

Challenges in the Monitoring of Therapeutic Plasma Exchange during Acute Heparin-Induced Thrombocytopenia in Adults under ECMO.

Therapeutic plasma exchange (TPE) has been proposed to remove heparin-induced thrombocytopenia (HIT) antibodies before planned thoracic surgery in patients with acute HIT and to allow brief re-exposure to heparin during surgery. In patients on extracorporeal membrane oxygenation (ECMO), simultaneous administration of TPE and alternative nonheparin anticoagulant therapies is challenging. We report 2 patients on ECMO with acute HIT who underwent repeated TPE to enable cardiothoracic surgery with the use of heparin. In both cases, serial monitoring of HIT antibody titer and heparin-induced platelet activation assay (HIPA) was performed. The effect of adding exogenous platelet factor 4 (PF4) in the HIPA was also tested. Negative anti-PF4/H IgG levels were achieved after 5 and 3 TPE sessions, respectively and patients could beneficiate from surgery with brief heparin re-exposure without any thrombotic complication. Negative HIPA results were obtained before negative anti-PF4/H IgG in one patient but remained positive in the other despite very low antibody titers. The addition of PF4 in HIPA led to more contrasted results for the two patients. Serial HIT screening including immunological and functional assays is necessary to closely monitor TPE in acute HIT patients on ECMO who require surgery. The addition of PF4 in HIPA could help detect clinically relevant platelet-activating antibodies and guide re-exposure to heparin.

Comparison of Direct Oral Anticoagulants vs Vitamin K Antagonists After Transcatheter Mitral Valve Replacement.

BACKGROUND: There is currently no established recommendation for antithrombotic treatment following transcatheter mitral valve replacement (TMVR). However, based on the analogy with surgical mitral bioprosthesis, vitamin K antagonists (VKAs) are predominantly used. OBJECTIVES: The purpose of this study was to compare bleeding and thrombotic events associated with direct oral anticoagulants (DOACs) or VKAs in a prospective cohort of TMVR patients. METHODS: We enrolled consecutive patients who underwent transseptal TMVR using a SAPIEN family prosthesis at our center between 2011 and 2023. The primary outcome was the occurrence of bleeding. VKAs were administered to patients until October 2019, after which DOACs were prescribed. The median follow-up was 4.7 months (Q1-Q3: 2.6-6.7 months). RESULTS: A total of 156 patients were included. The mean age was 65 ± 18.5 years, and 103 patients (66%) were women. The median EuroSCORE II was 7.48% (Q1-Q3: 3.80%-12.97%). Of the participants, 20.5% received DOACs and 79.5% were treated with VKAs. The primary outcome was observed in 50 (40%) patients in the VKA group and 3 (9%) patients in the DOAC group (adjusted HR: 0.21; 95% CI: 0.06-0.74; P = 0.02). Treatment with DOAC was associated with a shorter length of hospital stay. No significant differences were found in terms of thrombotic events, major vascular complications, stroke, or death. CONCLUSIONS: The use of DOACs after TMVR, compared with VKAs, appears to reduce the risk of bleeding complications and decrease the length of hospital stay for patients, without a significant increase in the risk of thrombotic events.

Exacerbation of thromboinflammation by JAK2V617F mutation worsens the prognosis of cerebral venous sinus thrombosis.

ABSTRACT: Cerebral venous sinus thrombosis (CVST) is an uncommon venous thromboembolic event accounting for <1% of strokes resulting in brain parenchymal injuries. JAK2V617F mutation, the most frequent driving mutation of myeloproliferative neoplasms, has been reported to be associated with worse clinical outcomes in patients with CVST. We investigated whether hematopoietic JAK2V617F expression predisposes to specific pathophysiological processes and/or worse prognosis after CVST. Using an in vivo mouse model of CVST, we analyzed clinical, biological, and imaging outcomes in mice with hematopoietic-restricted Jak2V617F expression, compared with wild-type Jak2 mice. In parallel, we studied a human cohort of JAK2V617F-positive or -negative CVST. Early after CVST, mice with hematopoietic Jak2V617F expression had increased adhesion of platelets and neutrophils in cerebral veins located in the vicinity of CVST. On day 1, Jak2V617F mice had a worse outcome characterized by significantly more frequent and severe intracranial hemorrhages (ICHs) and higher mortality rates. Peripheral neutrophil activation was enhanced, as indicated by higher circulating platelet-neutrophil aggregates, upregulated CD11b expression, and higher myeloperoxydase plasma level. Concurrently, immunohistological and brain homogenate analysis showed higher neutrophil infiltration and increased blood-brain barrier disruption. Similarly, patients with JAK2V617F-positive CVST tended to present higher thrombotic burden and had significantly higher systemic immune-inflammation index, a systemic thromboinflammatory marker, than patients who were JAK2V617F-negative. In mice with CVST, our study corroborates that Jak2V617F mutation leads to a specific pattern including increased thrombotic burden, ICH, and mortality. The exacerbated thromboinflammatory response, observed both in mice and patients positive for JAK2V617F, could contribute to hemorrhagic complications.

Circulating markers of endothelial dysfunction and platelet activation in patients with severe symptomatic cerebral small vessel disease.

BACKGROUND: Small deep infarcts (SDI), also called lacunar infarcts, resulting from the occlusion of deep branch arteries, account for 25% of ischemic strokes. The physiopathology of the disease remains largely unknown. However, evidence about the role of endothelial dysfunction has emerged. Whereas chronic platelet activation is of major importance in acute thrombosis of large atherosclerotic arteries, its role in SDI remains unclear. Frequently associated risk factors are hypertension and diabetes mellitus. The aim of this study was to determine platelet and endothelial activation in patients with recent SDI in comparison to population-based control subjects matched for age, sex and vascular risk factors. METHODS: Platelet activation markers (activated glycoprotein IIb/IIIa, P-selectin and platelet microparticles), shear-induced platelet aggregation (SIPA) studied in the SIPAgreg device at 4,000 s(-1), endothelial activation markers [including von Willebrand factor (vWF) antigen and homocysteine] and high-sensitivity C-reactive protein (hsCRP) were measured in 74 consecutive patients with recent SDI, in whom detectable large artery atherosclerosis or cardiac embolism had been ruled out. Blood samples were collected 1 and 3 months after symptom onset. These factors were also measured in 74 population-based controls with no stroke history and matched for age, sex, hypertension and diabetes. RESULTS: One month after symptom onset, the patients had similar levels of platelet activation to matched controls (p > 0.40 for all comparisons). In contrast, endothelial activation parameters were increased in patients in comparison to controls (vWF: p = 0.002 and homocysteinemia/creatinemia: p = 0.025). The level of hsCRP was slightly increased in patients compared to controls (p = 0.059). At 3 months, we observed a significant decrease in vWF and hsCRP levels in patients (median change in vWF = 10%, p = 0.004; median change in hsCRP = 0.4 mg/l, p = 0.02). Homocysteine levels and all platelet parameters remained unchanged at this time compared to at 1 month. CONCLUSIONS: Our results confirm that chronic platelet activation, when compared to controls matched for age, sex and vascular risk factors, did not seem to play a central role in the pathophysiology of lacunar stroke. In contrast, we found markers of endothelial dysfunction, the role of which in the occurrence of lacunar infarction has still to be clarified in further studies.

Platelet glycoprotein VI dimerization, an active process inducing receptor competence, is an indicator of platelet reactivity.

OBJECTIVE: The immune receptor homologue glycoprotein VI (GPVI)/FcR receptor γ chain complex is primarily responsible for platelet activation by collagen. There is growing evidence that optimal binding of GPVI to collagen depends on the assembly of GPVI dimers. The valence of GPVI on resting platelets needs to be clearly established because platelet avidity for collagen would be greater if GPVI is constitutively expressed as a dimer than as a monomer. METHODS AND RESULTS: Using a monoclonal antibody (9E18) that preferentially binds to GPVI dimers, we found that GPVI was maintained in a monomeric form on human resting platelets under the control of intraplatelet cAMP concentration. Activation by soluble agonists or von Willebrand factor induced a shift toward GPVI dimerization related to increased platelet adhesion to collagen. A correlation between platelet binding of 9E18 and P-selectin exposure was observed in patients experiencing coronary artery disease, and antagonists of the ADP receptor P2Y12 limited ADP-induced GPVI dimerization. CONCLUSION: The rapid assembly of highly competent dimers of GPVI at sites of vascular lesion represents an important step in the sequence of events leading to platelet activation by collagen. GPVI dimers could represent a new marker to analyze platelet reactivity.

Pre-interventional haemostatic assessment: Guidelines from the French Society of Anaesthesia and Intensive Care.

Recently the French Society of Anaesthesia and Intensive Care (Société Française d'Anesthésie et de Réanimation [SFAR]) issued recommendations for the prescription of routine preoperative testing before a surgical or non-surgical procedure, requiring any type of anaesthesia. Thirty clinical specialists performed a systematic analysis of the literature, and recommendations were then developed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. One part of these guidelines is dedicated to haemostatic assessment. The goal of pre-anaesthetic screening for congenital or acquired haemostatic disorders is to prevent perioperative haemorrhagic complications through appropriate medical and surgical management. Preoperative assessment of bleeding risk requires a detailed patient interview to determine any personal or family history of haemorrhagic diathesis, and a physical examination is necessary in order to detect signs of coagulopathy. Laboratory investigation of haemostasis should be prescribed, not systematically, but depending on clinical evaluation and patient history. Standard tests (prothrombin time, activated partial thromboplastin time, platelet count) have a low positive predictive value for bleeding risk in the general population. Patients with no history of haemorrhagic diathesis and no conditions liable to interfere with haemostasis should not undergo pre-interventional haemostasis testing. Conversely, the existence of a positive history or a disease that could interfere with haemostasis should be an indication for clinically appropriate testing.

Heparin-induced thrombocytopenia after cardiac surgery: an observational study of 1,722 patients.

OBJECTIVES: To assess the characteristics and prognosis of patients in whom heparin-induced thrombocytopenia (HIT) was confirmed (HIT+) among suspected HIT patients after having cardiac surgery and to assess the accuracy of two HIT scoring systems. DESIGN: An observational prospective study. SETTING: A cardiac surgery unit of a tertiary center from November 2005 to September 2007. PARTICIPANTS: Of the 1,722 patients who underwent cardiac surgery, 63 were suspected of HIT based on a platelet count <100 × 10(9)/L, a decrease in platelet count of >30%, or the occurrence of a thrombotic event. INTERVENTION: The HIT criteria were as follows: (1) the absence of another cause of thrombocytopenia, (2) positive antiplatelet factor 4 (PF4) antibodies (>0.5 optical density [OD]/mn) on enzyme-linked immunoabsorbent assay, and (3) recovery in platelet count after the discontinuation of heparin and substitution by danaparoid sodium. MEASUREMENTS AND MAIN RESULTS: HIT was confirmed in 24 patients (1.4% [0.8%-1.9%]); 23 belonged to the 984 treated by intravenous unfractionated heparin (IVUH) (2.3% IQ [1.4%-3.3%]) and 1 to the 738 treated by low-molecularweight heparin (0.14% [0.13%-0.4%]) (OD = 17.6; 95% confidence interval, 2.4-131; p < 0.0001). In the HIT+ patients compared with the unconfirmed HIT patients, thrombocytopenia occurred 7 (range, 6-9) days after surgery versus 3 (range, 3-5) days (p < 0.0001), and kinetics of platelet count showed a biphasic pattern. Six HIT+ patients (25% [7.7-42.3]) presented with an arterial thromboembolic event. Diagnosis performances of HIT scoring systems were low. CONCLUSIONS: Confirmed HIT occurred predominantly in patients treated with IVUH. The timing of thrombocytopenia and the variation pattern of the postoperative platelet count are key factors in diagnosing HIT. The overall incidence of intracardiac thrombotic events was noted to be high.

State of the art in cerebral venous sinus thrombosis animal models.

Cerebral venous sinus thrombosis (CVST) is an uncommon venous thromboembolic event accounting for less than 1% of strokes resulting in brain parenchymal injuries. Diagnosis and prognosis are still challenging due to highly variable clinical course and etiologies. Beyond thrombosis, different CVST-related parenchymal injuries may occur and include edema, ischemic strokes, and intra-cerebral hemorrhage (ICH; i.e., parenchymal/subdural hematomas, and subarachnoid hemorrhages), which are identified in 40%-60% of patients without clearly identified mechanisms. In this perspective, experimental animal models contribute to the understanding of initiation, propagation, and resolution of thrombosis, as well as brain-related damages. Last but not least, animal models may be useful to study new therapeutic approaches. In this review, we provide a comprehensive overview of CVST experimental models, focusing on their strengths, limits, and contribution to the current knowledge.

Hemorrhages in Polycythemia Vera and Essential Thrombocythemia: Epidemiology, Description, and Risk Factors-Learnings from a Large Cohort.

BACKGROUND: The management of myeloproliferative neoplasms (MPNs) is based on the reduction of thrombotic risk. The incidence, impact, and risk factors of bleedings have been less studied. METHODS: All patients with polycythemia vera (n=339) or essential thrombocythemia (n=528) treated in our center are included in OBENE (Observatoire BrEstois des NEoplasies myéloprolifératives) cohort (NCT02897297). Major bleeding (MB) and clinically relevant nonmajor bleeding (CRNMB) occurring after diagnosis were included, except after leukemic transformation. RESULTS: With a median follow-up of 8.3 years, incidence of hemorrhages was 1.85% patient/year, with an incidence of MB of 0.95% patient/year. The 10-year bleeding-free survival was 89%. The most frequent locations were digestive tract, "mouth, nose and throat," and muscular hematoma. The case fatality rate of MB was 25%. The proportion of potentially avoidable postoperative bleeding was remarkable (17.6%). In multivariable analysis, eight risk factors of bleeding were identified: leukocytes >20 G/L at diagnosis (hazard ratio [HR]=5.13, 95% confidence interval [CI]: 1.77-14.86), secondary hemopathies (HR=2.99, 95% CI: 1.27-7.04), aspirin use at diagnosis (HR=2.11, 95% CI: 1.24-3.6), platelet count >1,000 G/L at diagnosis (HR=1.93, 95% CI: 1.11-3.36), history of hemorrhage (HR=1.82, 95% CI: 1.03-3.24), secondary cancers (HR=1.71, 95% CI: 1.01-2.89), atrial fibrillation (HR=1.66, 95% CI: 1.01-2.72), and male sex (HR=1.54, 95% CI: 1.02-2.33). The occurrence of a CRNMB increased the risk of a secondary MB (odds ratio=6.13, 95% CI: 2.86-12.6, p<0.00001). Most patients taking hydroxyurea displayed a nonmacrocytic median corpuscular value in the months preceding bleeding (51.4%). DISCUSSION: The morbidity and mortality of bleedings in MPN should not be underestimated, and patients with platelet count >1,000 G/L and/or leukocytes >20 G/L, and possibly patients who suffered from a CRNMB could benefit from cytoreduction to reducing bleeding risk. Postoperative bleedings represent a substantial proportion of bleeding and could be better prevented.