A nanobody against the VWF A3 domain detects ADAMTS13-induced proteolysis in congenital and acquired VWD.

von Willebrand factor (VWF) is a multimeric protein, the size of which is regulated via ADAMTS13-mediated proteolysis within the A2 domain. We aimed to isolate nanobodies distinguishing between proteolyzed and non-proteolyzed VWF, leading to the identification of a nanobody (designated KB-VWF-D3.1) targeting the A3 domain, the epitope of which overlaps the collagen-binding site. Although KB-VWF-D3.1 binds with similar efficiency to dimeric and multimeric derivatives of VWF, binding to VWF was lost upon proteolysis by ADAMTS13, suggesting that proteolysis in the A2 domain modulates exposure of its epitope in the A3 domain. We therefore used KB-VWF-D3.1 to monitor VWF degradation in plasma samples. Spiking experiments showed that a loss of 10% intact VWF could be detected using this nanobody. By comparing plasma from volunteers to that from congenital von Willebrand disease (VWD) patients, intact-VWF levels were significantly reduced for all VWD types, and most severely in VWD type 2A-group 2, in which mutations promote ADAMTS13-mediated proteolysis. Unexpectedly, we also observed increased proteolysis in some patients with VWD type 1 and VWD type 2M. A significant correlation (r = 0.51, P < .0001) between the relative amount of high-molecular weight multimers and levels of intact VWF was observed. Reduced levels of intact VWF were further found in plasmas from patients with severe aortic stenosis and patients receiving mechanical circulatory support. KB-VWF-D3.1 is thus a nanobody that detects changes in the exposure of its epitope within the collagen-binding site of the A3 domain. In view of its unique characteristics, it has the potential to be used as a diagnostic tool to investigate whether a loss of larger multimers is due to ADAMTS13-mediated proteolysis.

Shear Forces Induced Platelet Clearance Is a New Mechanism of Thrombocytopenia.

BACKGROUND: Thrombocytopenia has been consistently described in patients with extracorporeal membrane oxygenation (ECMO) and associated with poor outcome. However, the prevalence and underlying mechanisms remain largely unknown, and a device-related role of ECMO in thrombocytopenia has been hypothesized. This study aims to investigate the mechanisms underlying thrombocytopenia in ECMO patients. METHODS: In a prospective cohort of 107 ECMO patients, we investigated platelet count, functions, and glycoprotein shedding. In an ex vivo mock circulatory ECMO loop, we assessed platelet responses and VWF (von Willebrand factor)-GP Ibα (glycoprotein Ibα) interactions at low- and high-flow rates, in the presence or absence of red blood cells. The clearance of human platelets subjected or not to ex vivo perfusion was studied using an in vivo transfusion model in NOD/SCID (nonobese diabetic/severe combined Immunodeficient) mice. RESULTS: In ECMO patients, we observed a time-dependent decrease in platelet count starting 1 hour after device onset, with a mean drop of 7%, 35%, and 41% at 1, 24, and 48 hours post-ECMO initiation (P=0.00013, P<0.0001, and P<0.0001, respectively), regardless of the type of ECMO. This drop in platelet count was associated with a decrease in platelet GP Ibα expression (before: 47.8±9.1 versus 24 hours post-ECMO: 42.3±8.9 mean fluorescence intensity; P=0.002) and an increase in soluble GP Ibα plasma levels (before: 5.6±3.3 versus 24 hours post-ECMO: 10.8±4.1 µg/mL; P<0.0001). GP Ibα shedding was also observed ex vivo and was unaffected by (1) red blood cells, (2) the coagulation potential, (3) an antibody blocking VWF-GP Ibα interaction, (4) an antibody limiting VWF degradation, and (5) supraphysiological VWF plasma concentrations. In contrast, GP Ibα shedding was dependent on rheological conditions, with a 2.8-fold increase at high- versus low-flow rates. Platelets perfused at high-flow rates before being transfused to immunodeficient mice were eliminated faster in vivo with an accelerated clearance of GP Ibα-negative versus GP Ibα-positive platelets. CONCLUSIONS: ECMO-associated shear forces induce GP Ibα shedding and thrombocytopenia due to faster clearance of GP Ibα-negative platelets. Inhibiting GP Ibα shedding could represent an approach to reduce thrombocytopenia during ECMO.

Severe haemorrhages leading to a diagnosis of rare bleeding disorder occur at a very young age: A study from the FranceCoag network.

INTRODUCTION: In the context of severe unexplained haemorrhage (SH), it is usual to seek haematological evaluation and investigate for an inherited rare bleeding disorder (IRBD). In such circumstances, appropriate screen can discriminate between IRBD and suspected child abuse. Yet, little information is available about the frequency of SH in the population of patients with IRBD. AIM: To collect epidemiologic data about SH and IRBD. METHOD: The database of the FranceCoag network has collected information about IRBD since January 2004. Based on data gathered up to 16 March 2022, a retrospective search was conducted for of SH events having occurred before or at the time of IRBD diagnosis. Demographics and diagnosis circumstances were retrieved, as well as information about SH, defined as any life-threatening bleeding or intracranial haemorrhage. RESULTS: Among the 13,433 patients of the database, 109 (0.8%) fulfilled inclusion criteria including a known date of IRBD diagnosis, haemophilia A or B (HA/HB) being the most frequent (82.5%). IRBD was discovered as a consequence of an SH event in 82.6% of the cases while CNS was involved in 55%. Severe and moderate HA/HB and other severe IRBD presented significantly more intracranial haemorrhage (p < .02) and a lower age at diagnosis (p = .03). CONCLUSIONS: These data support that any unusual SH should raise a suspicion of IRBD. Particularly before 1-year of age, it is suggested to first confirm moderate or severe haemophilia and severe IRBD by standard coagulation tests (APTT, PT and fibrinogen), combined with a clotting FXIII assay as first-line investigation. Subsequent assays of coagulation factors should be performed in the case of abnormal values, in second-line investigation.

Prophylaxis with recombinant factor IX Fc fusion protein reduces the risk of bleeding and delays time to first spontaneous bleed event in previously untreated patients with haemophilia B: A post hoc analysis of the PUPs B-LONG study.

OBJECTIVES: Haemophilia B (HB), characterised by deficient factor IX (FIX), leads to spontaneous bleeds. Severe cases require prophylactic FIX replacement. This post hoc analysis assessed the first spontaneous bleeds among previously untreated patients (PUPs) with HB treated with recombinant FIX Fc fusion protein (rFIXFc) (NCT02234310) to identify factors influencing bleeds. METHODS: Subjects included paediatric PUPs with HB (≤2 IU/dL endogenous FIX). Analyses described treatment patterns (on demand [OD] vs. prophylaxis) and prophylaxis type (started on vs. switched to prophylaxis). Kaplan-Meier analyses assessed the time to first spontaneous bleed, including median time to event and fitting models with predictors for treatment regimen and/or baseline age. RESULTS: PUPs B-LONG enrolled 33 subjects. Baseline age did not influence the time to first spontaneous bleed for any rFIXFc regimen. Those who started on prophylaxis with rFIXFc (n = 11), compared with those treated OD (n = 22), had an extended time to first spontaneous bleed. Starting prophylaxis afforded a 93% reduced risk of first spontaneous bleed versus starting OD (hazard ratio [95% confidence interval]: 0.071 [0.009-0.592]) (p = .015). CONCLUSION: rFIXFc prophylaxis, particularly starting early, reduced the risk of bleeding and delayed time to first spontaneous bleed compared with rFIXFc OD. Hence, initial treatment regimens impact bleed patterns in paediatric PUPs.

Definitions of major bleeding for predicting mortality in critically ill adult patients who survived 24 hours while supported with peripheral veno-arterial extracorporeal membrane oxygenation for cardiogenic shock: a comparative historical cohort study.

PURPOSE: The severity of bleeding events is heterogeneously defined during peripheral veno-arterial extracorporeal membrane oxygenation (pVA-ECMO). We studied three bleeding definitions in pVA-ECMO: the Extracorporeal Life Support Organization (ELSO)-serious bleeding, the Bleeding Academic Research Consortium (BARC), and the universal definition of postoperative bleeding (UPDB) classifications. METHODS: We included consecutive adult patients supported by pVA-ECMO for refractory cardiogenic shock admitted to Lille academic hospitals between January 2013 and December 2019. We assessed the association of bleeding definitions with the primary endpoint of 28-day all-cause mortality with the use of multivariate models accounting for time-dependent and competing variables. We compared models' performances using the Harrell's C-Index and the Akaike information criteria. RESULTS: Twenty-eight-day mortality occurred in 128/308 (42%) 308 patients. The ELSO-serious bleeding (hazard ratio [HR], 1.67; 95% confidence interval [CI], 1.09 to 2.56) and BARC ≥ type 2 (HR, 1.55; 95% CI, 1.01 to 2.37) were associated with 28-day mortality (Harrell's C-index, 0.69; 95% CI, 0.63 to 0.74 for both). Predictors of ELSO-serious bleeding were postcardiotomy, body mass index, baseline platelets count, fibrinogen, and hemoglobin levels. CONCLUSION: Extracorporeal Life Support Organization-serious bleeding and BARC ≥ type 2 are relevant definitions of major bleeding regarding their association with mortality in critically ill patients who survived the first 24 hr while supported with pVA-ECMO for cardiogenic shock. STUDY REGISTRATION: CERAR (IRB 00010254-2022-050, Paris, France); first submitted on 18 April 2022.

RéSUMé: OBJECTIF: La gravité des événements hémorragiques est définie de manière hétérogène pendant une oxygénation par membrane extracorporelle veino-artérielle périphérique (ECMO-VA périphérique). Nous avons étudié trois définitions du saignement sous ECMO-VA périphérique : les classifications des saignements graves selon l'Extracorporeal Life Support Organization (ELSO), celles du Bleeding Academic Research Consortium (BARC) et la définition universelle du saignement postopératoire (UPDB). MéTHODE: Nous avons inclus des patient·es adultes pris·es en charge de manière consécutive par ECMO-VA périphérique à la suite d'un choc cardiogénique réfractaire et admis·es dans les centres hospitaliers universitaires de Lille entre janvier 2013 et décembre 2019. Nous avons évalué l'association des définitions du saignement avec le critère d'évaluation principal de mortalité toutes causes confondues à 28 jours à l'aide de modèles multivariés tenant compte des variables dépendantes du temps et concurrentes. Nous avons comparé les performances des modèles à l'aide de l'indice C de Harrell et du critère d'information d'Akaike. RéSULTATS: La mortalité à 28 jours est survenue chez 128/308 (42 %) patient·es. Le saignement grave selon l'ELSO (rapport de risque [RR], 1,67; intervalle de confiance [IC] à 95 %, 1,09 à 2,56) et une classification BARC ≥ type 2 (RR, 1,55; IC 95 %, 1,01 à 2,37) étaient associés à une mortalité à 28 jours (indice C de Harrell, 0,69; IC 95 %, 0,63 à 0,74 pour les deux). Les prédicteurs d'hémorragie grave selon l'ELSO étaient la postcardiotomie, l'indice de masse corporelle, la numération plaquettaire initiale, le taux de fibrinogène et les taux d'hémoglobine. CONCLUSION: Les définitions du saignement grave de l'Extracorporeal Life Support Organization et une classification BARC ≥ type 2 sont des définitions pertinentes des saignements majeurs en ce qui touche à leur association avec la mortalité chez les personnes gravement malades qui ont survécu aux premières 24 heures alors qu'elles étaient prises en charge par ECMO-VA périphérique à la suite d'un choc cardiogénique. ENREGISTREMENT DE L'éTUDE: CERAR (IRB 00010254-2022-050, Paris, France); soumis pour la première fois le 18 avril 2022.

Cerebral Microbleeds During Transcatheter Aortic Valve Replacement: A Prospective Magnetic Resonance Imaging Cohort.

BACKGROUND: Cerebral microbleeds (CMBs) have been observed in healthy elderly people undergoing systematic brain magnetic resonance imaging. The potential role of acute triggers on the appearance of CMBs remains unknown. We aimed to describe the incidence of new CMBs after transcatheter aortic valve replacement (TAVR) and to identify clinical and procedural factors associated with new CMBs including hemostatic measures and anticoagulation management. METHODS: We evaluated a prospective cohort of patients with symptomatic aortic stenosis referred for TAVR for CMBs (METHYSTROKE [Identification of Epigenetic Risk Factors for Ischemic Complication During the TAVR Procedure in the Elderly]). Standardized neurologic assessment, brain magnetic resonance imaging, and analysis of hemostatic measures including von Willebrand factor were performed before and after TAVR. Numbers and location of microbleeds on preprocedural magnetic resonance imaging and of new microbleeds on postprocedural magnetic resonance imaging were reported by 2 independent neuroradiologists blinded to clinical data. Measures associated with new microbleeds and postprocedural outcome including neurologic functional outcome at 6 months were also examined. RESULTS: A total of 84 patients (47% men, 80.9±5.7 years of age) were included. On preprocedural magnetic resonance imaging, 22 patients (26% [95% CI, 17%-37%]) had at least 1 microbleed. After TAVR, new microbleeds were observed in 19 (23% [95% CI, 14%-33%]) patients. The occurrence of new microbleeds was independent of the presence of microbleeds at baseline and of diffusion-weighted imaging hypersignals. In univariable analysis, a previous history of bleeding (P=0.01), a higher total dose of heparin (P=0.02), a prolonged procedure (P=0.03), absence of protamine reversion (P=0.04), higher final activated partial thromboplastin time (P=0.05), lower final von Willebrand factor high-molecular-weight:multimer ratio (P=0.007), and lower final closure time with adenosine-diphosphate (P=0.02) were associated with the occurrence of new postprocedural microbleeds. In multivariable analysis, a prolonged procedure (odds ratio, 1.22 [95% CI, 1.03-1.73] for every 5 minutes of fluoroscopy time; P=0.02) and postprocedural acquired von Willebrand factor defect (odds ratio, 1.42 [95% CI, 1.08-1.89] for every lower 0.1 unit of high-molecular-weight:multimer ratio; P=0.004) were independently associated with the occurrence of new postprocedural microbleeds. New CMBs were not associated with changes in neurologic functional outcome or quality of life at 6 months. CONCLUSIONS: One out of 4 patients undergoing TAVR has CMBs before the procedure and 1 out of 4 patients develops new CMBs. Procedural or antithrombotic management and persistence of acquired von Willebrand factor defect were associated with the occurrence of new CMBs. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT02972008.

Acute Microbleeds and Microinfarcts Within the Perihematomal Area After Intracerebral Hemorrhage.

BACKGROUND: To further our understanding of the pathophysiology of spontaneous intracerebral hemorrhage (ICH) and related injury, we provided a postmortem neuropathological examination of acute microvascular lesions (microbleeds and microinfarcts) within the perihematomal area. METHODS: We included all consecutive cases (2005-2019) from the Lille University Hospital brain bank of ICH patients who died within the first month. Paraffin-embedded tissue sections from the perihematomal area were processed for several stainings and immunolabelings to investigate the presence of acute microbleeds and microinfarcts in the perihematomal area and to characterize surrounding neuronal and systemic inflammatory reaction (macrophages and neutrophils). RESULTS: We included 14 ICH cases (median age, 78 years; 10 females). Acute microbleeds were observed in the perihematomal area in 12/14 patients (86%, ranging from 1 through >10) and microinfarcts in 5/14 (36%, ranging from 1 through 4). Microbleeds were observed whatever the delay from ICH onset to death was, while most cases with acute microinfarcts were observed between day 3 and day 7 (n=3/5). Both lesions were characterized by an abundant accumulation of systemic inflammatory cells and necrotic areas. CONCLUSIONS: Acute microbleeds and microinfarcts might contribute to the propagation of secondary brain tissue damages after ICH. Our examinations also question the potential role of massive systemic inflammatory cells recruitment in the genesis of these microvascular injuries.

Determinants of adherence and consequences of the transition from adolescence to adulthood among young people with severe haemophilia (TRANSHEMO): A multicentric French national observational cross-sectional study based on the FranceCoag registry.

INTRODUCTION: It is necessary to gain insights into adherence to healthcare in people with severe haemophilia (PwSH), especially during the transition from paediatric to adult care, which is an important phase in lives of young people with childhood chronic disease. This adherence can be considered as a marker of successful transition. OBJECTIVES: The main objective of the quantitative phase of the TRANSHEMO project was to compare the adherence to healthcare between adolescents and young adults (YAs) with severe haemophilia. The secondary objective was to identify the determinants (facilitators and barriers) of this adherence and associations between these determinants. METHODS: A multicentre, observational, cross-sectional study was conducted in 2017-2019 on PwSH aged between 14 and 17 years (adolescents) or between 20 and 29 years (YAs), included in the FranceCoag registry and having completed the questionnaires. The adherence to healthcare (treatment regimens and clinical follow-up) was compared between adolescents and YAs using the chi-squared test. The determinants of this adherence were analysed by structural equation modelling. RESULTS: There were 277 participants, 107 adolescents, and 170 YAs. The rate of adolescents adhering to healthcare was 82.2%, while the rate of YAs was 61.2% (p < .001). The barriers to the adherence to healthcare were being YA, having repeated at least one school grade and presenting mental health concerns. CONCLUSION: Adolescents had better adherence to healthcare than YAs. According to the determinants enlightened in this project, targeted supportive strategies and adapted therapeutic education programs can be developed for young PwSH to facilitate their adherence to healthcare.

Big picture initiatives in bleeding disorders.

INTRODUCTION: The inherited bleeding disorders (IBD) community has witnessed significant therapeutic advances recently, yet important gaps persist, particularly for those with rare disorders and historically underserved populations. AIMS: -To create a national research blueprint agenda, led by the National Hemophilia Foundation (NHF), enhancing patient-centric principles, accelerate research progress and address important gaps in care. -To review critical gaps that remain to be addressed in women with IBDs, who face specific bleeding challenges. METHODS: The NHF research blueprint research agenda was defined by input from across the community, including caregivers and patients who are considered subject matter experts of their IBD, research leaders, allied health professionals and specialists, and representatives of the biopharmaceutical industry. In addition, two medical experts in the field of IBDs performed a comprehensive review to address the knowledge gaps in women with IBDs. RESULTS: Two foundational principles of the NHF blueprint are: (1) it must deliver on key issues that significantly impact the lives of those affected by IBDs, and (2) the priorities defined are relevant and actionable aimed to achieve health equity among all those affected by IBDs. A multidisciplinary approach is necessary for an optimal management of puberty, transition to adulthood and pregnancy. Even if strict guidelines are followed, recent studies show that women with IBDs are still facing a high burden. CONCLUSION: NHF blueprint will be issued in 2022. A specific research agenda is needed in women with IBDs to further improve their management and quality of life.

Occupational integration of adults with severe haemophilia (INTHEMO): A study based on the FranceCoag registry.

INTRODUCTION: Health of people with severe haemophilia (PwSH) improves thanks to the advancements in haemophilia care, giving them more opportunities in occupational integration. However, there is little literature on the occupational integration of PwSH. OBJECTIVES: The main objective of our study was to assess the occupational integration of PwSH and to compare it with that of the general population. The secondary objective was to study the association between individual characteristics (sociodemographic, clinical and psycho-behavioural) and occupational integration of PwSH. METHODS: A multicentre, non-interventional, cross-sectional study was conducted in 2018-2020 on PwSH, aged over 18 and under 65 years and included in the FranceCoag registry. Measurements included indicators of occupational integration, sociodemographic, clinical and psycho-behavioural characteristics. The indicators of occupational integration were compared with those of the general population, using indirect standardization. The data of the general population were available from the National Institute of Statistics and Economic Studies (INSEE). Determinants of occupational integration were explored using structural equation modelling. RESULTS: Of 1262 eligible people, 588 were included. PwSH had a lower employment rate than the general population (standardized ratio, .85; 95% CI, .77-.94). There were more PwSH at tertiary education level than expected (standardized ratio, 1.38; 95% CI, 1.17-1.61). HIV infection, poor physical health and mental health concerns were associated with a higher risk of unemployment in PwSH. CONCLUSION: Employment rate of PwSH is lower than that of the general population despite their higher education level. Target interventions focusing on determinants of difficult occupational integration could be helpful for PwSH.

Vascular Endothelial Damage in the Pathogenesis of Organ Injury in Severe COVID-19.

[Figure: see text].

Pharmacological Blockade of Glycoprotein VI Promotes Thrombus Disaggregation in the Absence of Thrombin.

OBJECTIVE: Atherothrombosis occurs upon rupture of an atherosclerotic plaque and leads to the formation of a mural thrombus. Computational fluid dynamics and numerical models indicated that the mechanical stress applied to a thrombus increases dramatically as a thrombus grows, and that strong inter-platelet interactions are essential to maintain its stability. We investigated whether GPVI (glycoprotein VI)-mediated platelet activation helps to maintain thrombus stability by using real-time video-microscopy. Approach and Results: We showed that GPVI blockade with 2 distinct Fab fragments promoted efficient disaggregation of human thrombi preformed on collagen or on human atherosclerotic plaque material in the absence of thrombin. ACT017-induced disaggregation was achieved under arterial blood flow conditions, and its effect increased with wall shear rate. GPVI regulated platelet activation within a growing thrombus as evidenced by the loss in thrombus contraction when GPVI was blocked, and the absence of the disaggregating effect of an anti-GPVI agent when the thrombi were fully activated with soluble agonists. The GPVI-dependent thrombus stabilizing effect was further supported by the fact that inhibition of any of the 4 key immunoreceptor tyrosine-based motif signalling molecules, src-kinases, Syk, PI3Kß, or phospholipase C, resulted in kinetics of thrombus disaggregation similar to ACT017. The absence of ACT017-induced disaggregation of thrombi from 2 afibrinogenemic patients suggests that the role of GPVI requires interaction with fibrinogen. Finally, platelet disaggregation of fibrin-rich thrombi was also promoted by ACT017 in combination with r-tPA (recombinant tissue plasminogen activator). CONCLUSIONS: This work identifies an unrecognized role for GPVI in maintaining thrombus stability and suggests that targeting GPVI could dissolve platelet aggregates with a poor fibrin content.

Von Willebrand Factor Multimers during Transcatheter Aortic-Valve Replacement.

BACKGROUND: Postprocedural aortic regurgitation occurs in 10 to 20% of patients undergoing transcatheter aortic-valve replacement (TAVR) for aortic stenosis. We hypothesized that assessment of defects in high-molecular-weight (HMW) multimers of von Willebrand factor or point-of-care assessment of hemostasis could be used to monitor aortic regurgitation during TAVR. METHODS: We enrolled 183 patients undergoing TAVR. Patients with aortic regurgitation after the initial implantation, as identified by means of transesophageal echocardiography, underwent additional balloon dilation to correct aortic regurgitation. HMW multimers and the closure time with adenosine diphosphate (CT-ADP), a point-of-care measure of hemostasis, were assessed at baseline and 5 minutes after each step of the procedure. Mortality was evaluated at 1 year. A second cohort (201 patients) was studied to validate the use of CT-ADP in order to identify patients with aortic regurgitation. RESULTS: After the initial implantation, HMW multimers normalized in patients without aortic regurgitation (137 patients). Among the 46 patients with aortic regurgitation, normalization occurred in 20 patients in whom additional balloon dilation was successful but did not occur in the 26 patients with persistent aortic regurgitation. A similar sequence of changes was observed with CT-ADP. A CT-ADP value of more than 180 seconds had sensitivity, specificity, and negative predictive value of 92.3%, 92.4%, and 98.6%, respectively, for aortic regurgitation, with similar results in the validation cohort. Multivariable analyses showed that the values for HMW multimers and CT-ADP at the end of TAVR were each associated with mortality at 1 year. CONCLUSIONS: The presence of HMW-multimer defects and a high value for a point-of-care hemostatic test, the CT-ADP, were each predictive of the presence of aortic regurgitation after TAVR and were associated with higher mortality 1 year after the procedure. (Funded by Lille 2 University and others; ClinicalTrials.gov number, NCT02628509.).

Relevance of platelet desialylation and thrombocytopenia in type 2B von Willebrand disease: preclinical and clinical evidence.

Patients with type 2B von Willebrand disease (vWD) (caused by gain-of-function mutations in the gene coding for von Willebrand factor) display bleeding to a variable extent and, in some cases, thrombocytopenia. There are several underlying causes of thrombocytopenia in type 2B vWD. It was recently suggested that desialylation-mediated platelet clearance leads to thrombocytopenia in this disease. However, this hypothesis has not been tested in vivo The relationship between platelet desialylation and the platelet count was probed in 36 patients with type 2B von Willebrand disease (p.R1306Q, p.R1341Q, and p.V1316M mutations) and in a mouse model carrying the severe p.V1316M mutation (the 2B mouse). We observed abnormally high elevated levels of platelet desialylation in both patients with the p.V1316M mutation and the 2B mice. In vitro, we demonstrated that 2B p.V1316M/von Willebrand factor induced more desialylation of normal platelets than wild-type von Willebrand factor did. Furthermore, we found that N-glycans were desialylated and we identified αIIb and ß3 as desialylation targets. Treatment of 2B mice with sialidase inhibitors (which correct platelet desialylation) was not associated with the recovery of a normal platelet count. Lastly, we demonstrated that a critical platelet desialylation threshold (not achieved in either 2B patients or 2B mice) was required to induce thrombocytopenia in vivo In conclusion, in type 2B vWD, platelet desialylation has a minor role and is not sufficient to mediate thrombocytopenia.

Management of bleeding and invasive procedures in haemophilia A patients with inhibitor treated with emicizumab (Hemlibra® ): Proposals from the French network on inherited bleeding disorders (MHEMO), the French Reference Centre on Haemophilia, in collaboration with the French Working Group on Perioperative Haemostasis (GIHP).

INTRODUCTION: Emicizumab (Hemlibra® ) recently became available and requires an adaptation for managing bleeding, suspected bleeding and emergency or scheduled invasive procedures in haemophilia A patients with inhibitor. This implicates a multidisciplinary approach and redaction of recommendations for care that must be regularly adapted to the available data. AIM: The following text aims to provide a guide for the management of people with haemophilia A with inhibitor treated with emicizumab in case of bleeding or invasives procedures. METHODS: The French network on inherited bleeding disorders (MHEMO), the French Reference Centre on Haemophilia (CRH), in collaboration with the French Working Group on Perioperative Haemostasis (GIHP) have been working together to make proposals for the management of these situations. RESULTS: Haemostatic treatment and other medications should be given stepwise, according to the severity and location of the bleeding or the risk of bleeding of the procedure as well as the haemostatic response obtained at each step in order to ensure an optimal benefit/risk ratio. CONCLUSION: The lack of data means that it is only possible to issue proposals rather than recommendations.

Von Willebrand factor as a biological sensor of blood flow to monitor percutaneous aortic valve interventions.

RATIONALE: Percutaneous aortic valve procedures are a major breakthrough in the management of patients with aortic stenosis. Residual gradient and residual aortic regurgitation are major predictors of midterm and long-term outcome after percutaneous aortic valve procedures. We hypothesized that (1) induction/recovery of high molecular weight (HMW) multimers of von Willebrand factor defect could be instantaneous after acute changes in blood flow, (2) a bedside point-of-care assay (platelet function analyzer-closure time adenine DI-phosphate [PFA-CADP]), reflecting HMW multimers changes, could be used to monitor in real-time percutaneous aortic valve procedures. OBJECTIVE: To investigate the time course of HMW multimers changes in models and patients with instantaneous induction/reversal of pathological high shear and its related bedside assessment. METHODS AND RESULTS: We investigated the time course of the induction/recovery of HMW multimers defects under instantaneous changes in shear stress in an aortic stenosis rabbit model and in patients undergoing implantation of a continuous flow left ventricular assist device. We further investigated the recovery of HMW multimers and monitored these changes with PFA-CADP in aortic stenosis patients undergoing transcatheter aortic valve implantation or balloon valvuloplasty. Experiments in the aortic stenosis rabbit model and in left ventricular assist device patients demonstrated that induction/recovery of HMW multimers occurs within 5 minutes. Transcatheter aortic valve implantation patients experienced an acute decrease in shear stress and a recovery of HMW multimers within minutes of implantation which was sustained overtime. In patients with residual high shear or with residual aortic regurgitation, no recovery of HMW multimers was observed. PFA-CADP profiles mimicked HMW multimers recovery both in transcatheter aortic valve implantation patients without aortic regurgitation (correction) and transcatheter aortic valve implantation patients with aortic regurgitation or balloon valvuloplasty patients (no correction). CONCLUSIONS: These results demonstrate that variations in von Willebrand factor multimeric pattern are highly dynamic, occurring within minutes after changes in blood flow. It also demonstrates that PFA-CADP can evaluate in real time the results of transcatheter aortic valve procedures.

The Carmat Bioprosthetic Total Artificial Heart Is Associated With Early Hemostatic Recovery and no Acquired von Willebrand Syndrome in Calves.

OBJECTIVES: To determine hemostasis perturbations, including von Willebrand factor (VWF) multimers, after implantation of a new bioprosthetic and pulsatile total artificial heart (TAH). DESIGN: Preclinical study SETTING: Single-center biosurgical research laboratory. PARTICIPANTS: Female Charolais calves, 2-to-6 months old, weighing 102-to-122 kg. INTERVENTIONS: Surgical implantation of TAH through a mid-sternotomy approach. MEASUREMENTS AND MAIN RESULTS: Four of 12 calves had a support duration of several days (4, 4, 8, and 10 days), allowing for the exploration of early steps of hemostasis parameters, including prothrombin time; coagulation factor levels (II, V, VII+X, and fibrinogen); and platelet count. Multimeric analysis of VWF was performed to detect a potential loss of high-molecular weight (HMW) multimers, as previously described for continuous flow rotary blood pumps. Despite the absence of anticoagulant treatment administered in the postoperative phase, no signs of coagulation activation were detected. Indeed, after an immediate postsurgery decrease of prothrombin time, platelet count, and coagulation factor levels, most parameters returned to baseline values. HMW multimers of VWF remained stable either after initiation or during days of support. CONCLUSIONS: Coagulation parameters and platelet count recovery in the postoperative phase of the Carmat TAH (Camat SA, Velizy Villacoublay Cedex, France) implantation in calves, in the absence of anticoagulant treatment and associated with the absence of decrease in HMW multimers of VWF, is in line with early hemocompatibility that is currently being validated in human clinical studies.

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.