Abnormal Von Willebrand Factor Research Articles

Investigation of von Willebrand factor multimer abnormalities before and after aortic valve replacement using the Hydragel-5 assay

BackgroundSevere aortic stenosis (sAS) is associated with acquired von Willebrand syndrome (AVWS) by loss of high-molecular-weight multimers (HMWM) of von Willebrand factor (VWF), potentially resulting in perioperative bleeding. Analysis of VWF multimers remains challenging. Recently, the new, rapid Hydragel 5 assay has been developed, using electrophoretic protein separation for dividing VWF-multimers into low (LMWM), intermediate (IMWM), and HMWM, the hemostatically active part of VWF. Here, we evaluated its impact on predicting blood loss in presence of AVWS after surgical aortic valve replacement (SAVR). MethodsWe prospectively examined 52 patients (age: 68 ± 7 years; 54 % male) admitted to SAVR. They were divided in two groups (A: normal VWF, n = 28; B: abnormal VWF, n = 24, defined as VWF-activity/antigen (VWF:Ac/Ag)-ratio < 0.7 and/or HMWM loss). Blood samples and echocardiographic data were collected before, seven days and three months after SAVR. Blood loss and transfusions were recorded. ResultsBaseline characteristics and clinical data were similar in both groups. HMWM loss was present in 38.5 % of all patients. HMWM, the VWF:Ac/Ag- and HMWM/(IMWM+LMWM)-ratios were significantly decreased preoperatively in group B but normalized after SAVR. Bleeding, re-thoracotomy and transfusion rates were comparable. HMWM loss was inversely correlated with the peak aortic gradient (Pmax) and positively with the aortic valve area (AVA), while HMWM/(IMWM+LMWM)-ratio negatively correlated with the mean aortic gradient (Pmean). ConclusionHMWM and HMWM/(IMWM+LMWM)-ratio inversely correlate with severity of AS and normalize after SAVR. The Hydragel-5 assay's might be valuable for routine diagnostics to assess bleeding risk and postoperative normalization of AS and VWF abnormalities in SAVR patients.

Discrepant low von Willebrand factor activity results on the ACL TOP analyzer are frequent in unselected patients with myeloproliferative neoplasms and show no correlation with high-molecular-weight multimer loss or bleeding phenotype

BackgroundBleeding complications are common in patients with myeloproliferative neoplasms (MPNs), with a subset developing acquired von Willebrand disease. Despite this association, a wide spectrum of von Willebrand factor (VWF) abnormalities are described, and the performance of modern assays remains unclear. ObjectivesTo comprehensively describe the pattern of VWF laboratory abnormalities in the MPN population. MethodsWe collected samples from 74 unselected clinic patients with MPNs to evaluate VWF quantitatively and qualitatively via multiple methods, correlating findings with a retrospective analysis of clinical bleeding data. VWF assays were performed on both ACL TOP (Instrumentation Laboratory) and Acustar (Instrumentation Laboratory) analyzers using HemosIL reagents (Instrumentation Laboratory), along with multimer analysis by gel electrophoresis. ResultsFunctional VWF measurements were not concordant between assays, with a median ACL TOP VWF glycoprotein IbR to antigen ratio (VWF:GPIbR/VWF:Ag) of 0.57 (IQR, 0.43-0.71) compared to a median Acustar VWF:GPIbR/VWF:Ag of 0.91 (IQR: 0.82-1.03;P < .001). The ACL TOP showed disproportionately lower results, with 73% of patients having a ratio <0.7. Despite this, no patient experienced loss of high-molecular-weight multimers by gel electrophoresis. An inverse relationship was observed between platelet count and functional ratios on both ACL TOP (R2 = 0.20; P < .001) and Acustar (R2 = 0.18; P = .0011) analyzers. While clinically significant bleeding events were relatively common (11% patients), there was no association with VWF assay abnormalities, and generally, an alternate cause(s) was identified. ConclusionDiscrepancies in functional VWF assays are common in patients with MPN, particularly by ACL TOP VWF:GPIbR. Based on our limited series, a VWF functional to an antigenic ratio of <0.7 (“type 2 pattern”) alone is poorly predictive of bleeding risk.

A Feasibility Study Evaluating Von Willebrand Factor in Patients with Gastrointestinal Angiodysplasia

Background: Abnormalities of von Willebrand Factor (VWF), such as those found in von Willebrand Disease (VWD) are associated with the development of abnormal blood vessels known as angiodysplasia. Angiodysplasia occurs primarily in the gastrointestinal (GI) tract, particularly the small bowel. Among patients with VWD, angiodysplasia is significantly overrepresented as a cause of GI bleeding and occurs in all VWD subtypes although it is reported more frequently in those with loss of the high molecular weight multimer of VWF. Recent studies have demonstrated more than a third of patients with VWD and GI bleeding have angiodysplasia when systematically assessed with Video Capsule Endoscopy (VCE) to examine the small bowel. Given the relationship between angiodysplasia and VWD our objective was to assess the feasibility of evaluating patients with GI angiodysplasia for abnormalities of VWF. Methods: We undertook a prospective single center pilot study to assess patients over the age of 18 with GI angiodysplasia for underlying abnormalities of VWF. Patients were identified based on angiodysplasia being present on a VCE study. Patients who consented to enrollment completed a self-administered bleeding assessment tool (BAT) as well as baseline demographic data. VWF testing included VWF antigen (VWF:Ag), VWF functional assay (VWF:GPIbM), Factor VIII coagulant activity (FVIII:C), and VWF pro-peptide (VWFpp) levels. Results: After reviewing 190 consecutive VCE studies performed at our institution between April 2021 and April 2023, we identified 50 patients who had capsule endoscopies demonstrating angiodysplasia of the GI tract. Thirteen of these patients consented to enrollment in the study. The bleeding histories of included patients are detailed in Table 1 along with their baseline clinical, laboratory, and demographic data. Two patients endorsed lifelong bleeding symptoms and three reported a significant family history of bleeding - all in a female relative. ISTH-BAT scores ranged from 0 to 18 with a median score of 2. Since our population is older than other studies that report on bleeding scores, we considered an abnormal bleeding score to be &amp;gt;6 as recent evidence indicates normal BAT scores increase over time. Five patients (38.6%) in our study had an ISTH-BAT abnormal bleeding score. VWF levels were assessed (Table 1) and one patient aged 88 years old with a significant family and lifelong history of bleeding received a new diagnosis of Type 2A VWD. Severe iron deficiency anemia requiring ongoing IV iron was diagnosed in two patients. Conclusion: In our feasibility study, we demonstrated a feasible protocol for recruitment of patients with GI angiodysplasia for clinical and laboratory testing of VWF. A significant proportion of our patients (38.6%) had abnormal bleeding scores and one patient had an underlying Type 2A VWD diagnosis.

PB0852 Abnormal von Willebrand Factor Test in Patients with Extreme Thrombocytosis

PB0852 Abnormal von Willebrand Factor Test in Patients with Extreme Thrombocytosis

A Fluorescence Cross-Correlation-Spectroscopy-Based Immunoassay for Rapid, Selective, and Accurate Protein Sizing in Human Plasma, Applied to the von Willebrand Factor.

Multimeric abnormalities in plasma von Willebrand factor (VWF) cause bleeding or clotting disorders. Electrophoretic analysis of multimers is used to detect such abnormalities but is qualitative, slow, and difficult to standardize. Fluorescence correlation spectroscopy (FCS) is a good alternative but is affected by low selectivity and concentration bias. Here, we report the development of a homogeneous immunoassay based on dual-color fluorescence cross-correlation spectroscopy (FCCS) that overcomes these challenges. By performing a mild denaturation treatment followed by reacting with polyclonal antibodies, the concentration bias was drastically reduced. The use of a dual antibody assay improved selectivity. Diffusion times of immunolabeled VWF were measured with FCCS and standardized relative to calibrator measurements. The assay measures size changes in VWF using 1 μL of plasma and less than 10 ng of antibody per measurement and was validated over a 16-fold range of VWF antigen concentration (VWF:Ag), with a sensitivity of VWF:Ag 0.8%. Concentration bias and imprecision were less than 10%. Measurements were unaffected by hemolytic, icteric, or lipemic interference. Strong correlations were obtained with reference densitometric readouts (0.97 for calibrators, 0.85 for clinical samples), and significant differences were found between normal (n = 10), type 2A (n = 5), and type 2B (n = 5) von Willebrand's disease and acquired thrombotic thrombocytopenic purpura (n = 10) samples (p < 0.01). This FCCS based immunoassay accurately and selectively determines changes in the multimeric status of plasma VWF and may be used as a simpler, faster, and a standardizable alternative for multimer analysis, following further clinical validation in larger cohorts.

ADAMTS13 inhibition to treat acquired von Willebrand syndrome during mechanical circulatory support device implantation

BackgroundAcquired von Willebrand syndrome (aVWS) is common in patients with mechanical circulatory support (MCS) devices. In these patients, the high shear stress in the device leads to increased shear‐induced proteolysis of von Willebrand factor (VWF) by A Disintegrin And Metalloprotease with Thrombospondin type 1 repeats, number 13 (ADAMTS13). As a result, the high molecular weight (HMW) VWF multimers are lost, leading to a decreased VWF function and impaired hemostasis that could explain the bleeding complications that are frequently observed in these patients. To counteract this abnormal VWF degradation by ADAMTS13, we developed a novel targeted therapy, using an anti‐ADAMTS13 monoclonal antibody (mAb) that inhibits the shear‐induced proteolysis of VWF by ADAMTS13. MethodsHuman or bovine blood was circulated through in vitro MCS device systems with either inhibitory anti‐ADAMTS13 mAb 3H9 or 17C7 (20 μg/ml) or control anti‐ADAMTS13 mAb 5C11 or phosphate buffered saline (PBS). VWF multimers and function (collagen binding activity) were determined at different time points. Next, Impella pumps were implanted in calves and the calves were injected with PBS and subsequently treated with mAb 17C7. VWF, ADAMTS13, and blood parameters were determined. ResultsWe demonstrated that blocking ADAMTS13 could prevent the loss of HMW VWF multimers in in vitro MCS device systems. Importantly, our antibody could reverse aVWS in a preclinical Impella‐induced aVWS calf model. ConclusionHence, inhibition of ADAMTS13 could become a novel therapeutic strategy to manage aVWS in MCS device patients.

Investigating the Role of Von Willebrand Factor (VWF) in Modulating In Vivo angiogenesis in VWF-Deficient Mice

Background: Previous studies have demonstrated the negative regulatory role of von Willebrand Factor (VWF) in angiogenesis involving extracellular and intracellular pathways that promote vascular endothelial growth factor (VEGF) signaling. These findings have provided direct evidence for the longstanding association between inherited and acquired abnormalities of VWF and the formation of angiodysplastic lesions, which continue to remain a major challenge. Understanding the role of VWF in angiogenesis could reveal new therapeutic targets that may lead to improved patient management strategies. Aim: To examine the impact and mechanisms of localized VWF replacement on in vivo angiogenesis in a VWF-deficient mouse model. Methods: Three separate experiments were carried out in 10 to 12-week old C57Bl/6 VWF-/- mice of both sexes. In all experiments plugs were excised after seven days of incubation and processed for hematoxylin and eosin (H&E) and immunohistochemical staining (IHC) to assess vessel formation and vascular permeability/maturity, except for the directed in vivo angiogenesis assay (DIVAA) where there was technical difficulty in obtaining histological sections. In the first experiment, DIVAA was employed to decrease inter-assay variability. Angioreactors containing Matrigel mixed with fibroblast growth factor (FGF), VEGF and varying doses of recombinant VWF (rVWF, VONVENDI®) were implanted subcutaneously in the right back flank of mice. Similar angioreactors without rVWF were implanted in the left back flank of mice as a control (N=15, 3 per dose group). In the second experiment the in vivo Matrigel plug assay was used to enable histological evaluation of plugs. 300 μL of Matrigel mixed with FGF, VEGF and rVWF at 0.5IU/ml and 10.0IU/ml, was injected subcutaneously in the right back flank of each mouse based on dose group. In the left back flank, an equal volume of Matrigel without rVWF was injected as a control (N=12, 6 per dose group of rVWF). The setup of the last experiment was similar to the second, however, Matrigel was supplemented with normal endothelial-colony-forming cells (ECFCs) as the source of localized VWF in place of rVWF, in a titration curve of cell numbers (1 x 105, 5 x 105, 1 x 106 cells; N=15, 3 per dose group). Results: Generally, there was a dose response gradient across all three experiments, with higher doses of rVWF or ECFC titres yielding more pronounced effects. In comparison to the lightly coloured angioreactors from the experimental group (supplemented with rVWF), those from the control group were dark red in colour indicating the presence of more vessels and erythrocytes in the Matrigel. No clear differences were observed between plugs that received rVWF at 0.5 IU/ml and those that did not, both grossly and histologically. Most plugs with 10 IU/ml of rVWF appeared lighter in colour compared to those without rVWF. A similar pattern was observed on H&E staining with sections from plugs supplemented with rVWF showing fewer capillaries and red cells, compared with plugs that had only growth factors (Figure 1A). In line with these observations, IHC quantitation of endothelial cells (ECs), pericytes and smooth muscle cells showed a decrease in capillary formation and vessel maturity in rVWF supplemented plugs, although this did not reach significance (Figure 1B). Compared to plugs that had ECFCs, those without ECFCs were dark red in colour, indicating the presence of more mature vessels with red cells. H&E staining of control plugs showed increased cellular infiltrate and capillary formation compared to those supplemented with ECFCs. Immunostaining of control Matrigel plugs also showed increased vascularization and maturity of vessels as evidenced by higher signals for neural/glial antigen 2 (NG2) stain for pericytes and alpha-smooth muscle actin (ASMA) which stains smooth muscle, compared to plugs with ECFCs across all groups. Conclusion: Despite clear differences observed in the gross images of plugs, no significant differences were seen following microscopic quantitation. This was possibly due to the small sample size per group and the marked variability between data points. However, considering the data reported above, the findings appear to highlight a potential inhibitory role of VWF in angiogenesis. Further experimentation is required to establish whether localized VWF can reverse the proangiogenic phenotype observed in VWF-deficient mice. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

How Do Laboratories Perform von Willebrand Disease Diagnostics and Classification of von Willebrand Disease Patients? Results from External Quality Data and an International Survey

Reduced or dysfunctional von Willebrand factor (VWF) may lead to von Willebrand disease (VWD), which is a common inherited bleeding disorder. VWD is classified into three major types: type 1 is a partial quantitative deficiency of VWF, type 3 is a complete quantitative deficiency of VWF, and type 2 consists of qualitative abnormalities of VWF. To arrive at a correct VWD diagnosis, multiple tests and a correct interpretation of these tests are needed. The aim of the present study was to gain insight into the approach of laboratories toward VWD diagnosis. Data from four samples of the external quality assessment (EQA) VWF surveys of the ECAT (External Quality Control for Assays and Tests) were evaluated. Furthermore, results were analyzed of a questionnaire that was sent to hemostasis laboratories about VWD diagnostic approaches. For most EQA samples, the majority of participants indicated the correct classification. However, 6 to 60% indicated another classification. For all samples, significant differences in VWF results were observed between the correct and incorrect classifications. The questionnaire demonstrated that the testing approach varied between the laboratories, especially for parameters that were essential for discrimination between VWD type 1 and healthy individuals, as well as the cutoff values used to discriminate VWD types 1 and 2. Diagnosis of VWD is heterogeneous in diagnostic approach, guidelines, and cutoff values within large ranges of VWF results between laboratories. Harmonization of approaches and increased accuracy of VWF measurements may help to establish a correct diagnosis.

How Do Laboratories Perform von Willebrand Disease Diagnostics and Classification of von Willebrand Disease Patients? Results from External Quality Data and an International Survey.

Reduced or dysfunctional von Willebrand factor (VWF) may lead to von Willebrand disease (VWD), which is a common inherited bleeding disorder. VWD is classified into three major types: type 1 is a partial quantitative deficiency of VWF, type 3 is a complete quantitative deficiency of VWF, and type 2 consists of qualitative abnormalities of VWF. To arrive at a correct VWD diagnosis, multiple tests and a correct interpretation of these tests are needed. The aim of the present study was to gain insight into the approach of laboratories toward VWD diagnosis. Data from four samples of the external quality assessment (EQA) VWF surveys of the ECAT (External Quality Control for Assays and Tests) were evaluated. Furthermore, results were analyzed of a questionnaire that was sent to hemostasis laboratories about VWD diagnostic approaches. For most EQA samples, the majority of participants indicated the correct classification. However, 6 to 60% indicated another classification. For all samples, significant differences in VWF results were observed between the correct and incorrect classifications. The questionnaire demonstrated that the testing approach varied between the laboratories, especially for parameters that were essential for discrimination between VWD type 1 and healthy individuals, as well as the cutoff values used to discriminate VWD types 1 and 2. Diagnosis of VWD is heterogeneous in diagnostic approach, guidelines, and cutoff values within large ranges of VWF results between laboratories. Harmonization of approaches and increased accuracy of VWF measurements may help to establish a correct diagnosis.

How Do Laboratories Perform von Willebrand Disease Diagnostics and Classification of von Willebrand Disease Patients? Results from External Quality Data and an International Survey.

Reduced or dysfunctional von Willebrand factor (VWF) may lead to von Willebrand disease (VWD), which is a common inherited bleeding disorder. VWD is classified into three major types: type 1 is a partial quantitative deficiency of VWF, type 3 is a complete quantitative deficiency of VWF, and type 2 consists of qualitative abnormalities of VWF. To arrive at a correct VWD diagnosis, multiple tests and a correct interpretation of these tests are needed. The aim of the present study was to gain insight into the approach of laboratories toward VWD diagnosis. Data from four samples of the external quality assessment (EQA) VWF surveys of the ECAT (External Quality Control for Assays and Tests) were evaluated. Furthermore, results were analyzed of a questionnaire that was sent to hemostasis laboratories about VWD diagnostic approaches. For most EQA samples, the majority of participants indicated the correct classification. However, 6 to 60% indicated another classification. For all samples, significant differences in VWF results were observed between the correct and incorrect classifications. The questionnaire demonstrated that the testing approach varied between the laboratories, especially for parameters that were essential for discrimination between VWD type 1 and healthy individuals, as well as the cutoff values used to discriminate VWD types 1 and 2. Diagnosis of VWD is heterogeneous in diagnostic approach, guidelines, and cutoff values within large ranges of VWF results between laboratories. Harmonization of approaches and increased accuracy of VWF measurements may help to establish a correct diagnosis.

Peripartum Management of Vonwildebrand Disease: A Case Report

Understanding coagulation disorders is essential, especially for obstetricians and intensive care providers managing parturients, as these disorders can have significant consequences for the mother and child during the peripartum period. Von Willebrand-Jürgens syndrome or von Willebrand disease is the most common congenital bleeding disorder. It is subject to autosomal inheritance with variable penetrance and expressivity. The cause of the disease lies in quantitative (type 1, type 3) or qualitative (type 2) abnormalities of vonWillebrand factor (vWF). vWF has two important functions in coagulation. On the one hand, it circulates in plasma as a carrier protein for factor VIII and thus has a protective function; on the other hand, it is responsible for platelet adhesion to the subendothelium of injured vessels and platelet aggregation . The risk of bleeding varies according to the severity of the injury. The therapeutic management strategy depends on the type of disease. In this paper, we report the observation of two patients with von Willebrand disease who had vaginal deliveries.

Phenotypic and genetic characterizations of the Milan cohort of von Willebrand disease type 2

Abstractvon Willebrand disease (VWD) type 2 is caused by qualitative abnormalities of von Willebrand factor (VWF). This study aimed to determine the genotypic and phenotypic characterizations of a large VWD type 2 cohort from Milan. We included 321 patients (54% female) within 148 unrelated families from 1995 to 2021. Patients were fully characterized using laboratory phenotypic tests, and the genotypic diagnosis was confirmed by target genetic analysis using Sanger sequencing. Patients were diagnosed with type 2A (n = 98; 48 families), 2B (n = 85; 38 families), 2M (n = 112; 50 families), or 2N (n = 26; 12 families). Eighty-two unique VWF variants, including 8 novel variants, were found. The potential pathogenic effect of novel variants was assessed by in silico analysis. Most patients were heterozygous for a single variant (n = 259; 81%), whereas 37 cases (11%) had 2 variants (4 homozygous, 9 in trans, and 24 in cis). Twenty-five patients (8%) had ≥3 variants, mainly as a result of gene conversions. Among the 82 distinct variants identified, 5 different types, including missense (n = 64), gene conversion (n = 10), synonymous (n = 1), deletion (n = 4), and splice (n = 3), were observed. The results from this large cohort showed that VWD type 2 is invariably due to variants that do not prevent the synthesis of the protein, and a vast majority of patients (88%) had missense variants. Given the complexity of type 2 diagnosis and the necessity of performing several phenotypic tests, genetic analysis for patients suspected of having type 2 is beneficial to establish the correct diagnosis.

Von Willebrand Disease

Von Willebrand disease is a hereditary bleeding disorder caused by a deficiency of von Willebrand factor. The prevalence of von Willebrand disease is estimated to range from approximately 1% of the general population to 125 clinically proven cases per million population. The main cause of this disease is a decrease in the level or function of abnormal von Willebrand factor due to a point mutation or large deletion that causes disruption of the structure and synthesis of von Willebrand factor. The most common symptoms include bleeding gums, hematuria, epistaxis, urinary tract bleeding, blood in the stool, easy bruising, and menorrhagia. There are several types of von Willebrand disease (VWF), namely type 1, type 2A, and type 2B which are inherited in an autosomal dominant manner, and type 2N, type 3 is inherited in an autosomal recessive manner. Management of VWD cases is generally carried out by administering drugs, plasma transfusions, and avoiding conditions that can cause involuntary injury or bleeding.

A thrombopoietin receptor agonist to rescue an unusual platelet transfusion-induced reaction in a p.V1316M-associated von Willebrand disease type 2B patient.

This report describes the first case of splenic injury in a patient with p.V1316M-associated von Willebrand disease type 2B (VWD2B) with chronic thrombocytopenia, successfully treated with nonoperative management including von Willebrand factor (VWF) replacement therapy, and platelet transfusions relayed by a thrombopoietin receptor agonist (TPO-RA, Eltrombopag). Eltrombopag was initially introduced to rescue an unusual post-platelet-transfusion reaction exacerbating the thrombocytopenia. In-depth analysis of the dramatic platelet count drop and VWF measurements timeline ruled out an allo-immune reaction and supported an alternative hypothesis of a sudden platelet clearance as a consequence of stress-induced release of abnormal VWF. One year later, a second life-threatening bleeding episode required urgent surgery successfully managed with VWF replacement therapy and platelet transfusions. Eltrombopag was further introduced in the post-surgery period to allow bleeding-free and platelet-transfusion-free successful recovery. Treatment decisions are particularly challenging in patients with VWD2B, and this case highlights how such decisions can benefit from understanding the molecular origin of platelet count fluctuations observed in these patients. Here, we successfully used a new therapeutic approach combining VWF-replacement therapy and initial platelet-transfusion relayed by TPO-RA to optimize patient management.Plain language summaryA combination of von Willebrand factor replacement and thrombopoietin receptor agonist in thrombocytopenic patients with von Willebrand disease type 2B: a new therapy approach to optimize patient management?Therapeutic management of patients with von Willebrand disease type 2B are particularly challenging in case of severe thrombocytopenia.Treatment includes von Willebrands factor replacement therapy and iterative platelet transfusions.We describe the first case of splenic injury in a patient with p.V1316M-associated von Willebrand disease type 2B successfully treated with nonoperative management including von Willebrand factor replacement therapy and platelet transfusions relayed by a thrombopoietin receptor agonist.We showed that the unusual post-platelet-transfusion reaction associated with a dramatic platelet count drop was a consequence of stress-induced release of abnormal von Willebrand factor.The combination of von Willebrand factor replacement therapy and thrombopoietin receptor agonist may offer a new therapeutic approach to optimize patient management.

Abstract 11397: Impact of Von Willebrand Factor Multimer Abnormalities on Blood Loss After Aortic Valve Replacement Using the Semi-Automated Hydragel 5 Multimer Assay

Introduction: Acquired von Willebrand syndrome (aVWS) is common in patients with severe aortic stenosis (sAS), which is characterized by the loss of high-molecular-weight multimers (HMWM) of the von Willebrand factor (VWF). VWF abnormalities are improved after surgical aortic valve replacement (SAVR). While conventional multimer analysis is technically challenging, lengthy and non-standardized, recently a new semi-automated multimer assay, the Hydragel 5 VWF multimers (H5VWM) has become available. Therefore, the aim of our study was to analyze VWF abnormalities by H5VWM in patients undergoing SAVR in terms of echocardiography parameter and perioperative bleeding. Methods: We prospectively included 52 patients (age: 67.9±7.2 years; 53.8% male) undergoing SAVR. Patients were divided in two groups (A: abnormal VWF, n=24; B: normal VWF, n=28). Blood samples and echocardiographic data were collected at three time points (TP): day before SAVR (TP1), 7 days (TP2), and 3 months (TP3) after SAVR. Blood loss from chest drainage and the use of blood and haemostatic products were evaluated peri- and postoperatively. Results: Baseline characteristics were similar in both groups. Loss of HMWM was present in 38.5%. After SAVR the level of HMWM had increased significantly compared to baseline in group A. At TP3, we observed no loss of HMWM at all. Bleeding occurred in 15% (A: 17% vs. B: 14%; p&gt;0.999) with need of re-thoracotomy in about 10% (A: 8% vs. B: 11%; p&gt;0.999). There was no significant difference in postoperative bleeding in the first 24hrs (A: 491 ml vs. B: 701ml; p=0.255). Also, peri- and postoperative need of blood transfusion and haemostatic agents were similar between both groups. HMWM was inversely correlated with the peak aortic gradient (R=-0.557; p&lt;0.001) and positively correlated with the aortic valve area (R=0.292; p=0.04). Conclusion: Loss of HMWM was not associated with increased postoperative bleeding in patients with sAS. Echocardiographic parameters could predict the loss of HMWM. The complete restoration of altered VWF at three months postoperatively, demonstrated by H5VWM, seems to be indicative for successful SVAR. Therefore, H5VWM, as a rapid and sensitive assay, could be included as diagnostic tool of suspected aVWS in AS patients.

Anticoagulation Use and Outcomes Among Patients with Atrial Fibrillation and Von Willebrand Disease

Intro: Von Willebrand disease (VWD) is a coagulopathy caused by deficiency or dysfunction of von Willebrand factor (VWF), resulting in prolonged and excessive bleeding. Patients are advised to avoid aspirin (ASA), P2Y12 inhibitors, or anticoagulation (AC) so as not to exacerbate this condition. However, typical treatment for atrial fibrillation (AF) includes anticoagulation, particularly if the risk of stroke by CHA 2DS 2-VASC score is 2+. Current recommendations suggest giving necessary antiplatelet (AP) or AC therapy over no treatment with assessment of bleeding risk throughout the course. However, this is a conditional recommendation based on low certainty in evidence, and there are no specific guidelines on treating AF in patients with VWD. This study aims to assess anticoagulation use, bleeding risk, and stroke risk in patients with VWF and AF.Methods: We conducted an IRB-approved analysis of coded data from institutional electronic medical records to select patients with diagnosis of VWD, low ristocetin cofactor level, or any abnormal VWF panel as well as patients with diagnosis of AF or atrial flutter. Three hundred and forty patients met criteria. Patients were manually screened for inclusion criteria and excluded for inaccurate diagnosis or insufficient data. Eighty-nine patients were included in the analysis. Primary endpoint was rate of major bleeding defined by ISTH criteria while on AC or AP. Categorical data were tested using the Fisher exact test at the nominal 0.05 two-sided significance level, and all person-time comparisons are made against the rate of bleeding on AC alone.Results: Most patients were female (64.0%; 57/89), and 28.1% (25/89) were deceased at the time of data collection. Date of diagnosis of AF ranged from 1980-2020. 42.7% (38/89) of patients were ever prescribed ASA, 43.8% (39/89) a P2Y12 inhibitor, 56.2% (50/89) AC, and 23.6% (21/89) had never been prescribed AP or AC. Of patients with a CHA 2DS 2-VASC of 2+, 57.5% (46/80) were ever prescribed AC. 32.0% (16/50) of patients ever prescribed AC and 25.6% (10/39) patients never prescribed AC had at least one major bleeding event (p=0.428). The rate of major bleeding on AC alone was 8.9 events per 100 person-years (32 events/359.2 years), 10.2 events per 100 person-years on AP alone (41 events/402.3 years) (p=0.572), and 1.06 events per 100 person-years (8 events/757.47 years) in patients never prescribed AC or AP (p=<0.0001). Notably, the rate of major bleeding on AC and AP together was 28.07 events per 100 person-years (23 events/81.94 years) (p=<0.0001) occurring in 7 patients, 6 of whom also had a diagnosis of acute coronary syndrome (ACS). Length of time to first major bleed is shown in Figure 1. 16.9% (15/89) of patients had thromboembolic strokes after diagnosis of AF, and 53.3% (8/15) of those strokes occurred when patients were not prescribed AC.Discussion: This retrospective observational study over 40 years characterizes AC and AP use in patients with VWD and AF. Only 57.5% of patients with CHA 2DS 2-VASC of 2+ received standard of care AC despite conditional recommendations to give necessary anticoagulation to patients with VWD. In parallel with the general population, AC use significantly increases the rate of major bleeding in patients with VWD, but there was no difference in bleeding rate between standard AC and AP monotherapy. However, major bleeding rates were notably elevated in patients prescribed concomitant AC and AP which most commonly occurred in the setting of ACS. This analysis is limited by its retrospective nature, the lack of granular details in the coded database, and incomplete data in older charts. Overall, these data do not support the use of AP monotherapy over standard AC to reduce bleeding rates for patients with VWD and AF. Additionally, AC and AP co-administration should be avoided due to high rates of major bleeding, but more studies are required to understand AP and AC strategies in patients with VWD, AF, and ACS. Although the rate of major bleeding is elevated with AC use in patients with VWD, there is no difference in lifetime prevalence of major bleeding events by AC vs no AC use. Finally, over half of thromboembolic strokes occurred when not prescribed AC. Shared decision-making around stroke and bleeding risk is advised in considering AC use for AF in patients with VWD. Prospective studies should further evaluate the risk of major bleeding and stroke in patients with VWD and AF on standard AC vs no AC. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Recognition and management of vascular lesions in von Willebrand disease

Recognition and management of vascular lesions in von Willebrand disease

Obstacles to Early Diagnosis and Treatment of Inherited von Willebrand Disease: Current Perspectives.

Von Willebrand disease (VWD), the most common inherited bleeding disorder, is highly heterogeneous, and its early diagnosis may be difficult, especially for mild cases and in qualitative von Willebrand factor (VWF) defects. Appropriate VWD diagnosis requires the combination of personal and/or family history of bleeding and abnormal VWF laboratory testing. The use of bleeding assessment tools has been helpful in standardizing bleeding history collection and quantification of bleeding symptoms to select patients who may benefit of further hemostatic testing. Type 1 and 3 VWD which represent quantitative VWD variants are relatively easy to diagnose. The diagnosis of type 2 VWD requires multiple assessments to evaluate the effects induced by the responsible abnormality on the heterogeneous functions of VWF. Sensitive and reproducible tests are needed to evaluate different VWF activities, starting from measuring VWF-platelet interaction. In the recent years, several increasingly sensitive, rapid and automated assays have been developed, but they are not widely available so far. Genetic testing for VWD diagnosis is not a common practice because VWF gene is very large and highly polymorphic and therefore it is used only in specific cases. It is evident that the early and correct VWD diagnosis allows optimal management of bleeding and situations at risk. Tranexamic acid, desmopressin, replacement therapy with plasma-derived concentrates with a variable content of VWF and FVIII, or the new recombinant VWF are the different therapeutic options available. Careful VWD classification guides treatment because desmopressin is widely used in type 1 while replacement therapy is the cornerstone of treatment for type 2 and 3 variants.

Characterization of ADAMTS13 and von Willebrand factor levels in septic and non-septic ICU patients.

Sepsis is a life-threatening disease characterized by excessive host response to infection that can lead to activation of the coagulation system. Von Willebrand Factor (VWF) and ADAMTS13 are important regulators of hemostasis and their dysregulation during sepsis progression is not well understood. Herein we characterize ADAMTS13 and VWF in septic and non-septic patients. ADAMTS13 activity, ADAMTS13 antigen, VWF antigen, myeloperoxidase, and protein C, were measured in plasma collected from 40 septic patients (20 non-survivors and 20 survivors) and 40 non-septic patients on the first and last day of their ICU stay. ADAMTS13 activity and ADAMTS13 antigen were reduced, whereas VWF antigen was elevated among septic patients compared to non-septic patients and healthy controls. Non-septic patients also exhibited elevated VWF antigen and reduced ADAMTS13 activity, but to a lesser extent than septic patients. Non-survivor septic patients exhibited the lowest levels of ADAMTS13 activity. ADAMTS13 activity:antigen ratio was similar across all patient cohorts suggesting that the specific activity of ADAMTS13 remains unchanged. Therefore, reduced ADAMTS13 function in circulation is likely due to a reduction in circulating levels. We suggest that massive release of VWF in response to inflammation consumes limited circulating ADAMTS13, resulting in the imbalance observed between VWF and ADAMTS13 among septic and to a lesser extent in non-septic ICU patients. Changes to ADAMTS13 did not correlate with myeloperoxidase or protein C levels. Reduced ADAMTS13 activity and antigen, and elevated VWF antigen observed among all patient cohorts on admission remained unchanged in survivors at ICU discharge. Prolonged reduction in ADAMTS13 activity and antigen in septic patients coincides with elevated levels of VWF. The persistent abnormalities in ADAMTS13 and VWF in sepsis patients discharged from the ICU may contribute to a sustained prothrombotic state.

A focal extramedullary hematopoiesis of the spleen in a patient with essential thrombocythemia presenting with a complicated postoperative course: a case report

BackgroundExtramedullary hematopoiesis is a compensatory response occurring secondary to inadequate bone marrow function and is occasionally observed in essential thrombocythemia (ET). This disease usually presents as multifocal masses in the paravertebral or intra-abdominal region; however, formation of a focal mass in the liver or spleen is rare. In addition, ET is characterized by increased platelet count and shows a tendency toward thrombosis and, occasionally, bleeding. Serious bleeding is common in ET patients, caused by the decrease in or abnormalities of von Willebrand factor (vWF) as a consequence of the precipitous rise in platelets. Therefore, strict management of platelet count using medication is crucial in patients with ET who require invasive procedures, especially splenectomy.Case presentationA 68-year-old man with ET was found to have an enlargement of a focal splenic tumor. Imaging findings revealed that the tumor was likely a hemangioma or hamartoma; however, the possibility of malignant disease could not be completely ruled out because of short-term tumor enlargement, and we conducted a splenectomy. The surgery was uneventful, but the patient presented with severe polycythemia and vWF abnormalities postoperatively, which resulted in bleeding from the drain insertion site and wound, epistaxis, and hemorrhoidal bleeding. Three months after discharge, polycythemia still persisted and the level of vWF gradually decreased. With a decrease in vWF, the patient suffered from an increased bleeding tendency. Therefore, the patient has been referred for bone marrow transplantation and is currently awaiting a suitable donor.ConclusionsExtramedullary hematopoiesis should be listed as a differential diagnosis of focal enlarged splenic tumors, especially in patients with myeloproliferative disorders. Additionally, in splenectomy for ET patients, careful perioperative management taking into consideration the conflicting features of a tendency toward thrombus formation and bleeding is necessary.