Von Willebrand Factor Activity Research Articles

Abstract 17813: Markers of Cellular Damage, Inflammatory Response, Coagulation and Platelet Activity, and Apoptosis During Catheter Ablation for Atrial Fibrillation Using Radiofrequency and Pulsed-Field Energy

Introduction: Pulsed-field ablation (PFA) presents a new technology for the ablation of AF using non-thermal ablation energy. Ablation energies producing thermal injury are associated with an inflammatory response, platelet activation, and coagulation cascade activation. The study aimed to compare markers of cell damage and platelet and coagulation activation in patients undergoing PVI using PF and radiofrequency (RF) energy. Hypothesis: PFA will be associated will more pronounced myocardial damage, but less pronounced activation of platelets and inflammation. Methods: Patients with AF indicated for PVI were enrolled and randomly assigned to undergo PVI using RF (CARTO Smart Touch, Biosense Webster, USA) or PF (Farapulse, Boston-Scientific, USA) energy. Markers of myocardial damage (high-sensitivity troponin I), apoptosis (Fas ligand, caspase-3), inflammation (interleukin-6), coagulation (D-dimers, Fibrin monomers, von Willebrand antigen and factor activity), platelet activation (P-selectin, activated Gp IIb/IIIa antigen and CD42b), and neuron axon damage (NGF-β) were measured before the procedure (T1), after transseptal puncture, (T2), after completing the ablation in the left atrium (T3), and one day after the procedure (T4). Results: Sixty-five patients were enrolled in the PFA (n=33) and RFA (n=32) groups. Both groups were similar in baseline characteristics (age 60.5±12.7 vs. 64.0±10.7 and 20 (60.6%) non-paroxysmal vs. 20 (62.5%) paroxysmal AF). Procedural and left atrial dwelling times were substantially shorter in the PFA group (55:09±11:57 vs. 151:19±41:25 min, p< 0.001; 36:00±8:05 vs. 115:58±36:49 min, p<0.001). Troponin release (1 d after the procedure) was substantially higher in the PFA group (10,102, IQR 8,272-14,207 vs. 1,006, IQR 603-1,433) and was ten times higher in PFA patients. However, during the procedure, markers of platelet activation, coagulation activation, and inflammation were similar between groups. Conclusions: PF ablation was associated with substantially more myocardial damage compared to radiofrequency ablation. However, coagulation activation, platelet activation, and inflammatory responses were similar.

Abstract 13671: A Case of Diffuse Alveolar Hemorrhage While on Systemic Anticoagulation for Impella

A 57 year old male with PMH of non-ischemic cardiomyopathy (EF 30%), atrial fibrillation, and VT s/p ICD was admitted to the cardiac intensive care unit for cardiogenic shock. His condition deteriorated necessitating Impella 5.5 implantation as bridge to cardiac transplant. Systemic heparin was started per Impella protocol with a lower anti-Xa goal of 0.2 - 0.3 given post-op bleeding at the R axillary Impella site. Five days post Impella placement he developed bloody secretions from the endotracheal tube requiring multiple blood transfusions and discontinuation of systemic heparin, while maintaining heparin purge. Labs were notable for anti-Xa 0.22, hemoglobin 9.7, and platelets 221. CT Chest demonstrated parenchymal opacities concerning for diffuse alveolar hemorrhage (DAH) which was confirmed via bronchoalveolar lavage; he had no known history of lung disease. High-dose corticosteroids were administered as a high ANA titer (1:128) and low C3 suggested capillaritis. However, decreasing ANA (1: 320) and a negative autoimmune workup decreased the likelihood of a rheumatologic cause for DAH and steroids were discontinued. DAH secondary to acquired von Willebrand syndrome (aVWS) was considered, but factor VIII and vWF activity levels were normal. The bloody secretions improved with inhaled thromboxane and systemic heparin was restarted. Orthotopic heart and kidney transplant was performed with subsequent Impella removal 104 days after Impella placement. Discussion: We present the first documented case of DAH with isolated Impella 5.5 support. Previously reported cases of DAH post-Impella were observed in patients with concurrent ECMO or RVAD. As autoimmune and coagulopathic causes of DAH were excluded, bland DAH secondary to systemic anticoagulation is most likely in this case. This raises a question about how to balance the risk of bleeding with the risk of device thrombosis, stroke and embolic events and when to switch from heparin to sodium bicarbonate purge.

Myocardial Damage, Inflammation, Coagulation, and Platelet Activity During Catheter Ablation Using Radiofrequency and Pulsed-Field Energy

BackgroundPulsed-field ablation (PFA) represents a new, nonthermal ablation energy for the ablation of atrial fibrillation (AF). Ablation energies producing thermal injury are associated with an inflammatory response, platelet activation, and coagulation activation. ObjectivesThis study aimed to compare the systemic response in patients undergoing pulmonary vein isolation (PVI) using pulsed-field and radiofrequency (RF) energy. MethodsPatients with AF indicated for PVI were enrolled and randomly assigned to undergo PVI using RF (CARTO Smart Touch, Biosense Webster) or pulsed-field (Farapulse, Boston-Scientific) energy. Markers of myocardial damage (troponin I), inflammation (interleukin-6), coagulation (D-dimers, fibrin monomers, von Willebrand antigen and factor activity), and platelet activation (P-selectin, activated GpIIb/IIIa antigen) were measured before the procedure (T1), after trans-septal puncture (T2), after completing the ablation in the left atrium (T3), and 1 day after the procedure (T4). ResultsA total of 65 patients were enrolled in the pulsed-field ablation (n = 33) and RF ablation (n = 32) groups. Both groups were similar in baseline characteristics (age 60.5 ± 12.7 years vs 64.0 ± 10.7 years; paroxysmal AF: 60.6% vs 62.5% patients). Procedural and left atrial dwelling times were substantially shorter in the PFA group (55:09 ± 11:57 min vs 151:19 ± 41:25 min; P < 0.001; 36:00 ± 8:05 min vs 115:58 ± 36:49 min; P < 0.001). Peak troponin release was substantially higher in the PFA group (10,102 ng/L [IQR: 8,272-14,207 ng/L] vs 1,006 ng/L [IQR: 603-1,433ng/L]). Both procedures were associated with similar extents (>50%) of platelet and coagulation activation. The proinflammatory response 24 h after the procedure was slightly but nonsignificantly higher in the RF group. ConclusionsDespite 10 times more myocardial damage, pulsed-field ablation was associated with a similar degree of platelet/coagulation activation, and slightly lower inflammatory response. (The Effect of Pulsed-Field and Radiofrequency Ablation on Platelet, Coagulation and Inflammation; NCT05603637)

In vitro field study and worldwide survey assessing how clinical haemostasis laboratories analyse recombinant and plasma-derived von Willebrand factor products.

Several well-established clinical laboratory methods are available to measure von Willebrand factor (VWF) in plasma samples, but few data are available on their use for analysing recombinant VWF (rVWF). To evaluate how clinical diagnostic laboratories analyse rVWF and plasma-derived VWF (pdVWF) spiked in vitro into VWF-deficient plasma using quantitative protein and functional assays of VWF. Human VWF-deficient plasma samples were spiked with rVWF (vonicog alfa; Takeda) or pdVWF/factor VIII (pdVWF/FVIII; antihemophilic factor/VWF complex [human], CSL Behring), each at final concentrations of 1.0, 0.6, 0.2, 0.1 IU/mL VWF:ristocetin cofactor activity (VWF:RCo) according to labelled VWF activity. The ISTH SSC secondary coagulation standard was used as a control. Participating laboratories received three sets of these blinded aliquots. Mean results per assay were compared with the expected potency based on the labelled VWF:RCo activity. Among 39 laboratories, the most commonly established assay was VWF:RCo; 22 laboratories reported data from 2214 tests. Despite a trend to lower values, VWF:RCo activities for rVWF were in agreement with target concentrations (71%-109%), whereas VWF:platelet glycoprotein Ib (VWF:GpIb) and VWF collagen-binding activity (VWF:CB) assays gave high recoveries (up to 132% and 127%, respectively). In contrast, pdVWF/FVIII was substantially underestimated by VWF:GpIb and VWF:CB assays (56%-86% recoveries), whereas the VWF:RCo assay gave recoveries of 47%-112% for pdVWF/FVIII. The results of VWF assays used in clinical laboratories differ between rVWF and pdVWF, particularly for VWF:GpIb and VWF:CB assays. These differences may arise from the higher multimeric structure of rVWF compared to pdVWF.

Alterations in the von Willebrand factor/ADAMTS-13 axis in preeclampsia

BackgroundPreeclampsia is a gestational hypertensive disorder characterized by maternal endothelial activation and increased ratio of soluble fms-like tyrosine kinase-1 (sFlt-1) inhibitor to placental growth factor (PlGF). The von Willebrand factor (VWF)/ADAMTS-13 axis is of interest because of the underlying endothelial activation and clinical overlap with pregnancy-associated thrombotic thrombocytopenic purpura. ObjectivesTo assess VWF, ADAMTS-13, and VWF/ADAMTS-13 ratio in preeclampsia and look for associations with sFlt-1/PlGF ratio and clinical features. MethodsThirty-four preeclampsia cases and 48 normal pregnancies were assessed in a case-control study. Twelve normal pregnancies in women with a history of preeclampsia formed an additional comparator group. VWF antigen (VWF:Ag) and VWF activity (VWF:Ac [VWF:glycoprotein IbM]) were measured via automated immunoturbidimetric assay, ADAMTS-13 activity was measured via fluorescence resonance energy transfer–VWF73 assay, and sFlt-1 and PlGF were measured via enzyme-linked immunosorbent assay. ResultsVWF:Ag was higher in preeclampsia than in normal pregnancy (median, 3.07 vs 1.87 IU/mL; P < .0001). ADAMTS-13 activity was slightly lower (median, 89.6 vs 94.4 IU/dL; P = .02), with no severe deficiencies. Significant elevations in VWF:Ac were not observed in preeclampsia, resulting in reduced VWF:Ac/VWF:Ag ratios (median, 0.77 vs 0.97; P < .0001). VWF:Ag/ADAMTS-13 ratios were significantly higher in preeclampsia (median, 3.42 vs 2.06; P < .0001), with an adjusted odds ratio of 19.2 for a ratio of >2.7 (>75th centile of normal pregnancy). Those with a history of preeclampsia had similar ratios to normal pregnant controls. VWF:Ag/ADAMTS-13 and sFlt-1/PlGF were not correlated. However, percentage reduction in platelets correlated positively with VWF:Ac (P = .01), VWF:Ac/VWF:Ag ratio (P = .004), and sFlt-1/PlGF ratio (P = .01). ConclusionThe VWF/ADAMTS-13 axis is significantly altered in preeclampsia. Further investigation of potential clinical utility is warranted.

Comprehensive Characterization of Coagulation Parameters in Venous Malformations

Introduction: Localized intravascular coagulopathy (LIC) is a well-recognized, though poorly characterized complication of venous malformations (VM) that can lead to bleeding, thrombosis, and phlebolith formation. While LIC has classically been characterized by elevations in D-dimer and reductions in fibrinogen, no comprehensive studies of coagulation parameters in VM have been performed to date. Since 2021, all patients with VM undergoing evaluation for LIC in the Yale Vascular Malformations Program (VaMP) and the Yale Classical Hematology clinic have been subjected to an extensive set of coagulation tests to fully analyze LIC. Our aim was to use these laboratory test results to comprehensively characterize LIC in this population. Methods: We conducted a retrospective chart review of all VM patients presenting to the Yale VaMP and the Yale Classical Hematology clinic for assessment of LIC from 2021 to 2023. All included patients were evaluated for LIC using the following coagulation parameters: von Willebrand Factor (VWF) antigen, VWF activity, factor VIII (FVIII), alpha-2 antiplasmin (A2AP), plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex (TAT), D-dimer (DD), fibrinogen, prothrombin time (PT), international normalized ratio (INR), and partial thromboplastin time (PTT). Measurements of VWF antigen, VWF activity, FVIII and A2AP were performed using an ACL TOP system (Instrumentation Laboratory; Bedford, MA, USA), while D-dimer and fibrinogen were measured using a BCS XP System (Siemens; Malvern, PA, USA) at our institution's clinical laboratory. PAI-1 and TAT were processed at national Clinical Laboratory Improvement Amendment-certified reference laboratories using ELISA-based assays. Baseline patient characteristics and coagulation test results were extracted via manual chart review. Data analysis was done using IBM SPSS statistics software and GraphPad Prism 9 software. Categorical variables were described using frequency and percentages, while quantitative variables were described using central tendency and dispersion measures. We performed univariate analysis using the Chi-square test. We also analyzed the coagulation tests using a correlation matrix. Statistical significance was set at p&amp;lt;0.05. This project was approved by our Institutional Review Board. Results: A total of 23 patients with VM were included in the analysis (Table 1). The mean age was 38 ± 16 years; the majority (82.6%) were female. The most common anatomic location was the head and neck (52.2%), while the most frequent extent of tissue involvement was muscle (54.5%), with most patients having a single lesion (59.1%) rather than multiple ones. No patients had venous thromboembolism. Normal DD and high TAT levels were observed in most patients (68.2% and 69.6%, respectively). VWF activity, VWF antigen, FVIII, PAI-1, and fibrinogen all were positively correlated (Figure 1). TAT was positively correlated with PAI-1 and inverselycorrelated withPT and INR. DD was positively correlated only with vWF activity. TAT and DD had a poor correlation; among patients with a normal TAT (n=7), 85.7% had a normal DD, while among patients with a normal DD (n=15), only 40% had a normal TAT. Three out of 4 (75%) patients with skin involvement had a high TAT with normal DD, while 2 out of 3 (66.7%) patients with visceral involvement had both high TAT and DD, although these patternswere not statistically significant (P=0.42 and 0.31, respectively). Among patients with muscle involvement (n=11), 45.5% had a high TAT and normal DD while 36.3% had both high TAT and DD. Conclusions: In this first comprehensive hematologic study of VM, we demonstrate that VM-related LIC is characterized by derangements of multiple coagulation parameters. Due to this, measurements of DD and fibrinogen alone may be inadequate for assessing LIC, and the addition of TAT and multiple other coagulation tests may yield a more complete picture of hemostatic derangements in LIC. A lack of correlation between DD and TAT is unexpected and merits further study. Differences in the depth of the VM tissue involvement and TAT/DD correlation may indicate a progression of coagulopathy related to the extent of VM but require further investigation in a larger study.

Effect of Factor VIII and Von Willebrand Factor Activities on Number of Bleeding Events in Previously Treated Patients with Von Willebrand Disease on Regular Prophylaxis with a Plasma-Derived Von Willebrand Factor/Factor VIII Concentrate

Background: von Willebrand disease (VWD) is characterized by a deficiency or reduction of activity in von Willebrand factor (VWF). As VWF has a role in stabilizing coagulation factor VIII (FVIII), VWD patients often suffer from secondary FVIII deficiency. Current guidelines recommend that VWD patients with a history of severe and frequent bleeds should use long-term prophylaxis with factor replacement therapy. The WIL-31 study demonstrated the efficacy of prophylaxis with a plasma-derived VWF/factor VIII concentrate containing VWF and FVIII in a 1:1 activity ratio (pdVWF/FVIII; wilate ®) in adults and children with VWD. The primary endpoint was met, showing a decrease of 84% in the mean total annualized bleeding rate (ABR). As elevated levels of FVIII are associated with an increased risk for thrombosis, it is important to determine whether repeated dosing with pdVWF/FVIII leads to accumulation of FVIII over time. Aims: To investigate the activity levels of VWF and FVIII in patients with VWD receiving regular prophylaxis with pdVWF/FVIII. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled male/female patients, aged ≥6 years old with VWD type 1 (VWF:RCo &amp;lt;30 IU/dL), type 2 (except 2N) or type 3. Prior to entering the WIL-31 study, all patients had received on-demand treatment with a pdVWF/FVIII concentrate during a 6-month, prospective, observational, run-in study (WIL-29). Patients in WIL-31 received regular pdVWF/FVIII prophylaxis 2-3 times per week at a dose of 20-40 IU/kg for 12 months. VWF activity (VWF:RCo) and FVIII activity (measured by the chromogenic [Chr] and one-stage [OS] assays) were performed at baseline and throughout the study. Full pharmacokinetic (PK) analyses were performed in all patients aged 6-16 years, a single dose of 60 ± 10 IU/kg pdVWF/FVIII was administered. Samples were collected at up to 1 hour prior to injection and then at multiple time points post-injection (1-72 hours). Safety, including the occurrence of thrombotic events, was monitored throughout the study. Results: The overall study population included 33 patients, with a median age of 18 years consisting of 9 (27.3%) patients aged 6-11 years, 6 (18.2%) patients aged 12-16 years, and 18 (54.5%) patients aged ≥17 years. Six (18.2%) patients had severe type 1 VWD, 5 (15.2%) patients had type 2, and 22 (66.7%) patients had type 3. Baseline FVIII and VWF activities in WIL-31 were similar regardless of age group, and as expected were lower in patients with type 3 VWD compared with severe type 1 and type 2 (Figure 1). There was a negative correlation of baseline FVIII and VWF activity with the number of spontaneous bleeding episodes (BEs) during prophylaxis. Patients who had no spontaneous BEs during prophylaxis had higher baseline FVIII and VWF levels compared with those who had spontaneous BEs. Mean peak and trough FVIII and VWF activity levels remained consistent during the study and there was no accumulation of either factor over the 12-month prophylaxis period (Figure 2). Full PK assessments were performed according to protocol in 13 patients aged 6-16 years. The mean ± standard deviation in vivo half-life was 16.1±6.7, 16.2±7.7, and 9.8±7.7 hours, for FVIII Chr, FVIII OS, and VWF:RCo, respectively. No thrombotic events were observed. Conclusion: No accumulation of FVIII or VWF in the plasma was reported in 33 patients who received regular prophylaxis with pdVWF/FVIII for 12 months, regardless of VWD type and age.

The Variable Heavy Chain Antibody Syn-VWFA1 Inhibits the Interaction of Platelets to Von Willebrand Factor in Solution but Not to Immobilized Von Willebrand Factor Thereby Inhibiting 3-Dimensional but Not 2-Dimensional Thrombus Formation

Neutralizing the interaction between GP1bα and von Willebrand Factor (VWF) is an attractive strategy for treatment and prevention of platelet-VWF agglutinate formation in von Willebrand disease type 2B and thrombotic thrombocytopenic purpura. The aim of this study was to characterize a llama-derived variable heavy chain antibody (VHH) targeting the A1 domain of active VWF (Syn-VWFA1), in terms of its interference with platelet VWF interaction. Syn-VWFA1 (1.5 µM) abolished platelet binding to ristocetin-activated VWF (native and Haemate® P VWF) and R1306W VWF (VWF type 2B) in a flow-cytometric platelet function assay (Figure 1). Moreover, Syn-VWFA1 dose-dependently inhibited ristocetin-activated VWF and R1306W VWF platelet agglutination, but not collagen- and ADP-induced platelet aggregation. Under flow conditions, Syn-VWFA1 (1.8 µM) did not affect adhesion of platelets to collagen at high shear. In the shear- and collagen-dependent PFA-200, Syn-VWFA1 prolonged the closure time, but only at high concentrations (&amp;gt;3 µM), while GPIba binding to immobilized VWF remained unaffected by Syn-VWFA1. Syn-VWFA1 increased the cleavage of VWF multimers by ADAMTS13. Furthermore, by applying deuterium exchange, we found a small region in the β1 to α1 loop (1288-1293) in the A1 domain of VWF, which is likely to constitute the nanobody binding site (Figure 2) and binding of Syn-VWFA1 to the A1 domain results in a conformational change exposing regions in the α2 and α3 helices. In conclusion, Syn-VWFA1 dose-dependently blocks platelet-binding to activated VWF in solution, but not to (collagen-) immobilized active VWF. This implies that immobilization of VWF to collagen affects VWF conformation in such a way (1) that access of Syn-VWFA1 to its epitope in the A1 domain is hindered or (2) that conformational changes following Syn-VWFA1 binding are blocked, while allowing platelet binding. This implies that Syn-VWFA1 has potential treatment opportunities for patients with increased circulating active VWF, to prevent 3-dimensional thrombus formation (pathological platelet-VWF aggregate formation) but not 2-dimensional thrombus formation (leaving physiological hemostasis at sites of vascular injury intact).

Quantitative System Pharmacology Modeling of the Effect of Recombinant ADAMTS13 on Platelets in Patients with Congenital Thrombotic Thrombocytopenic Purpura

Background: Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare, thrombotic microangiopathy due to an inherited deficiency of the von Willebrand factor (VWF)-cleaving protease, ADAMTS13.Accumulation of ultra-large VWF multimers increases blood clot formation in small blood vessels, leading to a low platelet count (thrombocytopenia). Treatment of cTTP consists of ADAMTS13 replacement with infusions of plasma-based therapies (PBT). Recombinant ADAMTS13 (rADAMTS13; Takeda Development Center Americas, Inc., Lexington, MA, USA) is in development for patients with cTTP.The ultra-rare nature of cTTP limits the sample size for a formally powered study to assess the impact of ADAMTS13 supplementation on efficacy outcome. This study was a proof-of-principle that model-based clinical trial simulations can be used to supplement clinical trial data in ultra-rare indications. Aims: To calibrate and validate a quantitative system pharmacology (QSP) model describing a mechanistic relationship between ADAMTS13, VWF and platelet numbers in patients with cTTP who received long-term prophylaxis with rADAMTS13 or PBT (fresh frozen or solvent/detergent treated plasma). In addition, to evaluate the treatment benefits of rADAMTS13 versus PBT using clinical trial simulations in virtual patients with cTTP as a supplement to the cTTP phase 3 study (NCT03393975) data. Methods: A QSP model was built using i) in vitro enzyme kinetic data and preclinical experimental data following administration of recombinant VWF and rADAMTS13 in ADAMTS13 knockout (KO) mice, and ii) data from the literature including platelet count and VWF activity from healthy human and untreated patients with cTTP. These data were used to calibrate the parameters corresponding to interactions between ADAMTS13 activity, VWF activity, and platelets. The model was validated against literature data from patients with cTTP treated with PBT and with data from a phase 2 study of patients with immune-mediated TTP treated with rADAMTS13 (NCT03922308). The model was then calibrated to longitudinal platelet data from the cTTP phase 3 study, in which patients with cTTP received prophylaxis for 6 months with PBT (exposure equivalent to ~10 IU/kg ADAMTS13 in the form of 10-20 mL/kg doses) and rADAMTS13 (40 IU/kg) either once every week (Q1W) or once every 2 weeks (Q2W) dosing intervals . The model was used to provide 1-year clinical trial simulations of isolated thrombocytopenia occurrences in a population of 1,000 virtual patients, phenotype-matched to patients in the cTTP phase 3 study. Results:Virtual clinical trial simulations using the QSP model suggested that rADAMTS13 administered over 1 year with a Q1W or Q2W schedule results in significantly fewer patients experiencing occurrences of thrombocytopenia (platelet count threshold of &amp;lt;150 x 10 9/L) compared to patients treated with PBT (hazard ratio [HR] relative to Q2W PBT: Q1W PBT, HR = 0.62; Q2W rADAMTS13, HR = 0.47; Q1W rADAMTS13, HR = 0.18). The treatment difference between rADAMTS13 and PBT was even more pronounced when a thrombocytopenia threshold of &amp;lt;100 x 10 9/L was used (Figure and Table). Simulations also predicted a prophylactic carry-over effect on platelets, with approximately 20 days taken to reach 90% of the long-term average platelet count when switching from rADAMTS13 to PBT or from PBT to rADAMTS13. A correlation analysis for a Q2W dosing of rADAMTS13 demonstrated that ADAMTS13 trough activity (C trough, Spearman ρ = 0.96) and time with ADAMTS13 activity above 10% (Spearman ρ = 0.93) showed stronger correlations with increased platelet count than the maximum plasma ADAMTS13 activity level (C max, Spearman ρ = 0.68). A correlation analysis for a Q1W dosing frequency produced similar results.Mean time above 10% ADAMTS13 activity was higher following rADAMTS13 versus PBT administration (5.2 vs 1.7 days). Conclusions: This model-based virtual clinical trial simulation predicts that dosing with rADAMTS13 would provide &amp;gt;50% reduction in the HR of thrombocytopenia occurrences over PBT. Patients may also have a higher level of protection for 2-3 weeks when switching from rADAMTS13 to PBT. These findings supplement the assessment of clinical benefit of rADAMTS13 in the cTTP phase 3 study and show that increased ADAMTS13 activity following rADAMTS13 administration is likely to reduce occurrences of thrombocytopenia in cTTP.

Analysis of Laboratory Parameters before the Occurrence of Hepatic Sinusoidal Obstruction Syndrome in Pediatric Patients after Hematopoietic Stem Cell Transplantation

Introduction: Hepatic sinusoidal obstruction syndrome (SOS), also known as veno-occlusive disease of the liver, is a serious complication following hematopoietic stem cell transplantation (HSCT). Early diagnosis and treatment with defibrotide can improve patient outcome. The pathogenesis is not fully understood, but it is obvious that some laboratory parameters are already changed before the onset of SOS. The aim of our retrospective study was to detect laboratory parameters following HSCT that can predict the occurrence of SOS. Methods: We analyzed 182 children with a median age of 7.2 years who underwent allogeneic or autologous HSCT for the first time and without defibrotide prophylaxis. Our study population consisted of 126 patients who received allogeneic HSCT (69.2%) and 56 patients who underwent autologous HSCT (30.8%). The stem cell sources were peripheral blood stem cells (50.5%) or bone marrow (49.5%) and the most frequent underlying diseases were solid tumors (34.1%), genetic diseases (19.2%), acute lymphoblastic leukemia (18.1%), and acute myeloid leukemia (13.7%). The diagnosis of SOS was based on the pediatric criteria of European Society for Blood and Marrow Transplantation. We investigated the following 15 laboratory parameters after HSCT before the onset of SOS: international normalized ratio (INR), activated partial thromboplastin time (aPTT), reptilase time, factor VIII, factor XIII, von Willebrand factor (vWF), von Willebrand factor activity (vWF activity), fibrinogen, antithrombin III, protein C, protein S, D-dimer, alanine aminotransferase (ALT), bilirubin, and ferritin. The last laboratory values within one week before the onset of SOS were analyzed in the SOS patient group. In the non-SOS patient group, we investigated the parameters for four weeks after transplantation and calculated the median. We selected cut-off values for the continuous parameters based on receiver operating characteristic curves analyses and existing reference values. We performed Mann-Whitney U test, univariate and multivariate analyses to find significant ( P &amp;lt; .05) associations between the values of laboratory parameters and the occurrence of SOS. The probability of developing SOS was calculated using the significant independent variables. Results: The overall incidence of SOS was 14.8% at a median time of 13 days after HSCT. SOS developed in 24 of 126 allogeneic (19.1%) and in 3 of 56 autologous (5.4%) HSCT patients. Only 3 out of 27 patients (11.1%) who suffered from very severe SOS died within 100 days after HSCT. In the univariate analysis, we found significant associations between the onset of SOS and the following parameters: INR ≥ 1.3, aPTT ≥ 40 sec, reptilase time ≥ 18.3 sec, factor VIII ≤ 80%, antithrombin III ≤ 75%, protein C ≤ 48%, D-dimer ≥ 315 µg/L, bilirubin ≥ 9 µmol/L, and ferritin ≥ 3100 µg/L. In multivariate analysis, we confirmed INR ≥ 1.3 [odds ratio (OR) = 8.104, P = .006], aPTT ≥ 40 sec (OR = 10.174, P = .001), protein C ≤ 48% (OR = 5.215, P = .014), and ferritin ≥ 3100 µg/L (OR = 7.472, P = .004) as independent risk factors after HSCT before SOS. If three of the four significant cut-off values were present, the probability of developing SOS was more than 70%. The probability of SOS was 96%, if all four laboratory parameters were changed according to the cut-off values. The values of factor XIII, vWF, vWF activity, protein S, fibrinogen, and ALT were not relevant for the occurrence of SOS. Conclusions: In summary, the laboratory parameters INR, aPTT, protein C, and ferritin were very useful to predict the occurrence of SOS. These four parameters can enable earlier diagnosis and treatment leading to an improved outcome. In addition, this is the first report on a significant association between SOS and high values of INR and aPTT after HSCT before SOS.

No Increased Incidence of Bleeding in Essential Thrombocythemia Patients with Extreme Thrombocytosis

CONCLUSIONS About 25% of essential thrombocythemia (ET) patients present with extreme thrombocytosis (ExT), defined as having a platelet count ≥1000 x 10^9/L. ExT patients may have an increased bleeding risk, at least in part associated with acquired von Willebrand disease. There are no specific guidelines for managing ExT patients, and many are started on cytoreduction, even if they are younger and otherwise at low thrombotic risk by the revised International Prognostic Score of Thrombosis for ET (R-IPSET). We analyzed the risk of bleeding and thrombosis in ExT vs. non-ExT ET patients to inform treatment decisions. METHODS : We retrospectively analyzed patients who received targeted gene sequencing at Massachusetts General Brigham / Dana-Farber Cancer Institute from 2014-2021 and met WHO 2016 criteria for ET. We performed medical record review and recorded information on treatment, diagnosis, blood counts, and von Willebrand antigen and activity levels. We abstracted the first major bleed, clinically relevant non-major bleed (CRNMB), and thrombotic event in a patient's disease course. Bleeding was categorized using the International Society on Thrombosis &amp; Haemostasis definitions.We determined the cumulative incidence rates of bleeding and thrombosis in ExT and non-ExT patients with death as a competing event and compared these rates using a Gray test. Risk factors for bleeding and thrombosis were evaluated using univariate and multivariate Fine Gray models. We identified 408 patients diagnosed with ET, of which 344 had a platelet count reported at diagnosis. There were 96 ExT patients and 248 non-ExT patients. Median follow-up was 11 and 6 years, and median platelet count at ET diagnosis was 1194 and 651, respectively. ExT patients, compared with non-ExT patients, were more likely to be younger (51 vs. 58 years old, p&amp;lt;.001), have the CALR mutation (49% vs. 23%, p&amp;lt;.001), have lower IPSET-thrombosis risk (65% vs. 49% very low or low risk, p&amp;lt;.001), and have lower von Willebrand activity levels at diagnosis or in disease course (60% vs. 94%, p&amp;lt;.001, Table 1). There were 7 (7%) major bleeds and 7 (7%) CRNMBs in the 96 ExT patients, and 11 (4%) major bleeds and 22 (9%) CRNMBs in the 248 non-ExT patients (p=.29 for major bleeding, p=.83 for CRNMB). 10 year cumulative incidence of major bleed and CRNMB was not different in ExT vs. non-ExT patients (4% vs. 5%, p=.68 for major bleed; 3% vs. 10%, p=.27 for CRNMB, Figure 1). Despite 65% of ExT patients in our sample categorized as very low or low risk for thrombosis, these patients were more likely to be treated with cytoreduction compared to non-ExT patients (63% vs. 50%, p=.21 for very low risk; 81% vs. 51%, p=.022 for low risk). However, there was no difference in the 10 year cumulative incidence of major bleeding and CRNMB in ExT patients who were treated vs. not treated with cytoreduction (6% vs. 0%, p=.13 for major bleed; 2% vs. 8%, p=.13 for CRNMB). There was also no difference in the cumulative incidence of bleeding in ExT and non-ExT patients who were not treated with cytoreduction (untreated or aspirin alone, 0% vs. 4%, p=.34 for major bleed; 8% vs. 9%, p=.75 for CRNMB). In univariate analysis, diabetes mellitus and thrombosis during disease course were significantly associated with increased combined major bleeding and CRNMB. In a multivariable analysis adjusting for these factors in addition to platelet count ≥1000 x 10^9/L and age at ET diagnosis, first von Willebrand factor activity, aspirin and cytoreduction during disease course, and JAK2 mutation status, diabetes mellitus (HR 3.45, 95% CI 1.31-8.72) and thrombosis during disease course (HR 2.92, 95% CI 1.41-6.03) remained as significant risk factors for bleeding. Cytoreduction was not significantly associated with a lower rate of bleeding in multivariable analysis (HR .42, 95% CI .09-3.06). 10 year cumulative incidence of thrombosis was not different in ExT vs. non-ExT patients (22% vs. 26%, p=.94). We found no difference in the cumulative incidence of bleeding and thrombosis in ET patients with ExT and importantly, no clear role for initiation of cytoreductive therapy in these patients who are otherwise low risk by R-IPSET. This confirms the current recommendations to initiate cytoreduction based on thrombotic risk and suggests that ExT alone should not be an indicator for cytoreduction.

Hemostasis Biomarkers and Long-Term Risk of Recurrent Cardiovascular Events and Bleeding Complications in Young Patients with an Ischemic Stroke

Background: Patients with ischemic stroke at a young age (18-50 years) have a persistent increased risk of recurrent ischemic cardiovascular events, despite antithrombotic treatment. Additionally, antithrombotic agents result in a higher risk of bleeding complications. Balancing hemostasis to prevent thrombotic events and minimizing the risk of hemorrhagic events is challenging. Previous research observed a hypercoagulable state and a significant degree of inflammation years after an acute ischemic stroke in young adults. It is known that an increased clotting tendency is a risk factor for a first ischemic stroke, especially in young adults. However, the risk profile of a recurrent event in these individuals can be different. To this end, our study aims to investigate the role of plasma pro- and anticoagulation biomarkers, platelet activation markers and thrombin generation parameters in the risk of recurrent ischemic arterial events and bleeding complications after a first ischemic stroke or transient ischemic attack (TIA) at a young age. Method: Patients from a single-center cohort study (the FUTURE cohort) with a first-ever TIA or ischemic stroke event between 1980 and 2010 were included. Blood was collected in 2010 and patients were followed on recurrent ischemic events or bleeding complications between 2010 and 2023. The following coagulation parameters were measured: blood cell count, Von Willebrand factor, active Von Willebrand factor, factor VIII, prothrombin, fragment 1.2, d-dimer, fibrinogen, fibrin degradation products, antithrombin, alpha-2-macroglobulin, serum CXCL-4 and CXCL-7. In addition, thrombin generation (TG) was determined using 1pM and 5pM tissue factor, and thrombomodulin in platelet-poor plasma to assess the functional capacity of plasma to form thrombin. The primary outcome was a composite of recurrent ischemic stroke, TIA, acute coronary syndrome or peripheral artery disease. The secondary outcome was the occurrence of a bleeding complication using the Bleeding Academic Research Consortium (BARC) criteria. We applied Cox proportional hazard models to estimate hazard ratios (HR) with 95% confidence intervals (CI). Results : Among 378 patients (median age 42.1 years, 56% women), 74 experienced a recurrent ischemic event during a mean follow-up of 6.5 years. An increased platelet and leukocyte count, along with elevated levels of fragment 1.2, fibrinogen and D-dimer were associated with a higher risk of ischemic events (table 1). Patients with low plasma antithrombin activity had a higher risk of recurrent ischemic events, especially in women (HR 0.67 [0.47-0.96]). After adjustment for age, sex and traditional risk factors, the association between leukocytes numbers, fragment 1.2 and fibrinogen levels and antithrombin activity and the risk of recurrent ischemic events remained: HR 1.14 [1.05-1.25], 1.07 [1.01-1.14], 0.80 [0.65-0.98], and 1.09 [1.00-1.17], respectively. In patients without vitamin K antagonist treatment, the association between antithrombin activity (HR 0.78 [0.62-0.98]) and leukocytes numbers (HR 1.15 [1.05-1.25]) with recurrent ischemic events were stronger. Thrombin generation parameters were not related to recurrence. Bleeding complications were observed in 16% of patients, mainly among women and predominantly attributable to gynecological bleedings. Hemoglobin, platelets, CXCL-4 and -7, prothrombin, fragment 1.2 and alpha-2-macroglobulin were associated with a bleeding complication (table 2). The association for platelets (HR 0.93 [0.89-0.97]), CXCL-4 (HR 0.90 [0.82-0.99]) and alpha-2-macroglobulin (HR 1.15 [1.03-1.29]) remained after adjustment. Conclusion: Lower antithrombin activity and, higher fragment 1.2, fibrinogen levels, and leukocytes counts were linked to an increased risk of recurrent ischemic events. Bleeding was associated with platelets, CXCL4, and alpha-2-macroglobulin. Overall, especially platelets appear to be significantly involved in the risk of both recurrent arterial thrombosis and bleeding, whereas the observed association with risk of recurrent ischemic events implies a more dominant role of the coagulation system.

Immunogenicity of a Plasma-Derived Von Willebrand Factor/Factor VIII Concentrate during the Wil-31 Prophylaxis Study in Patients with Von Willebrand Disease

Background: Long-term prophylaxis with a von Willebrand factor (VWF) concentrate is recommended in people with von Willebrand disease (VWD) with a history of frequent and severe bleeds. The WIL-31 study demonstrated the efficacy of prophylaxis with a plasma-derived VWF/factor VIII (pdVWF/FVIII) concentrate containing VWF and FVIII in a 1:1 activity ratio (wilate ®) in adults and children with VWD of all types. The primary endpoint was met, showing a decrease in mean total annualized bleeding rate (ABR) of 84% compared with prior on-demand treatment. Aim: To assess the immunogenicity of pdVWF/FVIII when used during the WIL-31 study in children and adults with VWD of all types. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled male/female patients aged ≥6 years with VWD type 1 (VWF: RCo &amp;lt;30 IU/dL), type 2 (except 2N) or type 3. Prior to entering the WIL-31 study, all patients had received on-demand treatment with a VWF-containing product during a 6-month, prospective, observational, run-in study (WIL-29); patients who experienced at least 6 bleeding episodes (BEs), excluding menstrual bleeds, of which ≥2 were treated with a VWF-containing product, were eligible to enter WIL-31. During WIL-31, patients received regular pdVWF/FVIII (containing VWF and FVIII in a 1:1 activity ratio) prophylaxis 2-3 times per week at a dose of 20-40 IU/kg for 12 months. FVIII (chromogenic and one-stage assays) and VWF (VWF:RCo assay) activities were assessed at baseline and throughout the study. Retention samples were collected at screening and baseline visits for possible later inhibitor testing (to be performed at a central laboratory using the Nijmegen-Bethesda assay for FVIII inhibitors and the mixing study based on VWF:RCo for VWF inhibitors). Inhibitor testing was also performed if inhibitor development was suspected. Results: Inhibitor testing was performed in 2 of 33 patients because of unusual pharmacokinetic results at the 6-month visits, even though neither patient had any clinical signs of an inhibitor. The VWF inhibitors were detected in samples from two brothers taken at their 6-month visits. However, when retained blood samples from the screening visits of both boys were tested, both samples tested inhibitor-positive, demonstrating that both boys had developed the inhibitors prior to starting prophylaxis during WIL-31. During and before the WIL-29 run-in study, both boys had been treated on demand with another pdVWF/FVIII concentrate. The boys had both been diagnosed with VWD shortly after birth, and it was suspected that they had type 2A based on family history and were 15 (patient A) and 11 years old (patient B) at the start of WIL-31. They had a family history of VWD (both parents were diagnosed with VWD), but no family history of inhibitors. After the completion of WIL-31, both patients were reclassified to type 3 VWD following further investigation including next-generation sequencing. Baseline VWF activity indicated low VWF:RCo levels (Patient A: 0.092 IU/mL and Patient B: 0.65 IU/mL; Figure 1). The boys received 38 (patient A) and 34 IU/kg (patient B) pdVWF/FVIII respectively, twice weekly during WIL-31, and their mean total ABRs decreased by 85% and 91%, respectively, during WIL-31 compared with WIL-29. All bleeding episodes during WIL-31 were spontaneous nose bleeds. Both boys continued the same prophylactic regimen until the end of WIL-31. In one patient the inhibitor titer was negative by the end of the study. Conclusion: VWF inhibitors were detected in 2 of the 33 patients on prophylaxis with pdVWF/FVIII in the WIL-31 study and subsequent investigation revealed that both patients were already positive for VWF inhibitors prior to the study start. In one of the patients, the inhibitor resolved during continued prophylaxis. Despite the inhibitors, prophylaxis was effective in both patients with an ≥85% reduction in ABR compared to on demand treatment.

Clinical and Laboratory Presentation and Underlying Mechanism in Patients with Low VWF.

Low von Willebrand factor (VWF) refers to subjects with plasma levels of 30 to 50 IU/dL. The mechanism of low VWF is poorly understood. We chose to determine the clinical presentation, laboratory phenotype, and underlying mechanisms of low VWF. We included 250 patients characterized with low VWF. The International Society on Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH-BAT) was used to assess clinical symptoms. To determine the underlying mechanisms of low VWF, we used as markers the VWF propeptide (VWFpp) assay and FVIII:C/VWF:Ag ratio for VWF synthesis and the VWFpp/VWF:Ag ratio for VWF clearance. Results were compared with those of 120 healthy controls. Cases with abnormal screening tests were further evaluated for coagulation factor levels and platelet disorders. The median age of the cohort was 35 years (range 3-85), 21% were children (n = 53), 34% were adult males (n = 85), and 45% (n = 112) were adult females. According to the ISTH-BAT, abnormal bleeding was found in 35% of children, 47% of males, and 49% of females. No association was found between VWF activity levels and ISTH-BAT. Patients showed an overall decreased VWF synthesis/secretion and an enhanced VWF clearance was identified in 33% of them. In 89 patients (36%), there were other hemostasis-related defects, but there was no difference in the ISTH-BAT between the two groups. Our findings indicate that reduced VWF synthesis/secretion and enhanced VWF clearance are major mechanisms of low VWF levels. Patients with low VWF have significant bleeding manifestations. While other hemostasis defects occurred together with low VWF, this combination did not exacerbate clinical symptoms.

Transient elastography and von Willebrand factor as predictors of portal hypertension and decompensation in children

Von Willebrand factor antigen (vWFAg), a protein measured to test the level of vWF released from the vascular endothelium has gained much attention as a marker for portal hypertension (PHT) severity. The objectives of this study were to investigate the use of vWFAg as a biomarker along with liver and spleen stiffness measurements by transient elastography as potential predictors of clinically significant varices (CSV), variceal bleeding (VB) and decompensation in children with PHT. This observational prospective cohort study included 117 children (median age 10 [IQR 6-14] years) who underwent oesophagogastroduodenoscopy between January'2012 to November'2021 and a validation group of 33 children who underwent the same procedure between December'2021 to March'2023. Measurements of vWFAg and glycoprotein Ib binding activity of VWF (GPIbR) were available in 97 patients in the study group and in all patients in the validation group.Results: vWFAg and GPIbR were significantly higher in children with CSV (223 IU/dl and 166 IU/dl; p= 0.015 and p= 0.04, respectively) and VB (218 IU/dl and 174 IU/dl; p= 0.077 and p= 0.03, respectively) than in those without CSV or VB, respectively. Ninety-six patients had liver and spleen stiffness measurements. Spleen stiffness was significantly higher in patients with CSV compared to those without CSV (p= 0.003). In a chronic liver disease subgroup, a predictive scoring tool based on vWFAg, GPIbR, platelet count, and spleen/liver stiffness measurements could predict CSV with an AUROC of 0.76 (p= 0.04). This study suggests the predictive value of vWF for CSV and VB increases when combined with spleen stiffness, with AUROCs of 0.88 and 0.82, respectively. Hence, a combination of biomarkers could assist clinicians in diagnosing CSV, preventing unnecessary invasive procedures. Surveillance endoscopies in children with portal hypertension (PHT) have their own risks and non-invasive markers, such as von Willebrand factor antigen, glycoprotein Ib binding activity of VWF (GPIbR), and transient elastography could be used to predict clinically significant varices, variceal bleeding and disease compensation in children with PHT. Such non-invasive markers for PHT and varices are lacking in the paediatric population. The results show that von Willebrand factor and GPIbR along with transient elastography can be used to formulate a scoring system which can be used as a clinical tool by paediatric hepatologists to monitor the progression of PHT and risk of bleeding, and hence to stratify the performance of invasive endoscopic procedures under general anaesthesia. However, there is a need to validate the scoring system in children with portal vein thrombosis and for hepatic decompensation in a multi-centre registry in the future.

Evaluation of hemostasis parameters in recipients following related transplantation of the right lobe of the liver

Objective: to study the dynamics of hemostasis parameters in the early postoperative period and to identify the timing of restoration of the level of procoagulants and anticoagulants synthesized by the liver (received from a living related donor) in liver lobe recipients.Materials and methods. Under observation were 31 recipients and 31 related donors of liver lobe. They were treated at the Republican Specialized Scientific and Practical Medical Center for Surgery in Tashkent, Uzbekistan, from August 2022 to August 2023. Hemostasis parameters were determined in recipients, whose postoperative period was uneventful.Results. It was revealed that compensation in the hemostasis system occurs even at low levels of coagulation factors on day 10 after liver transplantation (LT). In recipients, a decrease in anticoagulants was more pronounced than that of procoagulants. In general, the hemostasis system was in an unstable equilibrium, which, under the influence of external and internal factors, can easily shift both towards hypercoagulable and hypocoagulable state. Activity of the fibrinolytic system and fibrinogen level are significant influencing factors. Gradual recovery of fibrinogen levels by the end of day 1 after surgery is the result of activation of the synthetic function of the liver. After LT, there were signs of endothelium activation, but not endothelial damage, which regress and normalize by postoperative day 10. At the same time, in the initial status, recipients had an increase in both the amount and activity of von Willebrand factor, which indicates endothelial damage and dysfunction. The low level of homocysteine in recipients is probably a protective factor against the development of thrombotic complications, and homocysteine dynamics reflects the gradual restoration of the functional activity of the liver, adaptation of the donor liver to functioning.Conclusion. Monitoring of hemostasis system in recipients after liver transplantation allows to prevent thrombohemorrhagic complications in time but also to assess the dynamic equilibrium of procoagulants and anticoagulants, the timing of restoration of the activity of the main hemostasis factors and, according to this, to vary the administration regimes of anticoagulants, antiplatelet medications, and fibrinolysis inhibitors, to carry out replacement therapy and to realize the concept of hemostasis management.

Peptidylarginine deiminase 4 and ADAMTS13 activity in Staphylococcus aureus bacteraemia.

Staphylococcus aureus infection is associated with increased levels of neutrophil extracellular traps (NETs) and von Willebrand factor (VWF), and with reduced activity of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motifs, member 13). Peptidylarginine deiminase 4 (PAD4) contributes to NET formation and inactivates ADAMTS13 in vitro. The role of PADs in the dynamics of NETs, VWF and ADAMTS13 has not yet been studied. We thus aimed to assess the longitudinal evolution of NETs, PADs, VWF and ADAMTS13 activity in S. aureus infection. Plasma samples from S. aureus bacteraemia patients were longitudinally collected and analysed for NETs, PAD4/PAD2, VWF and ADAMTS13 activity. Correlation analyses with clinical data were performed. Recombinant PAD4 and S. aureus were assessed in vitro for their potential to modulate ADAMTS13 activity. Sixty-seven patients were included. Plasma levels of NETs, VWF, PAD4 and PAD2 were increased and ADAMTS13 activity was decreased. Levels of PADs were negatively correlated with ADAMTS13 activity. NETs were positively correlated with PADs, and negatively with ADAMTS13 activity. In vitro, recombinant PAD4 but not S. aureus reduced ADAMTS13 activity in plasma. Levels of PAD4 and PAD2 correlate with reduced ADAMTS13 activity, with neutrophils as the likely source of PAD activity in S. aureus bacteraemia. This article is part of the Theo Murphy meeting issue 'The virtues and vices of protein citrullination'.

PB0824 Prospective Longitudinal Evaluation Shows Increase of VWF and FVIII Activity with Age in Patients with Type 1 and 2 von Willebrand Disease

PB0824 Prospective Longitudinal Evaluation Shows Increase of VWF and FVIII Activity with Age in Patients with Type 1 and 2 von Willebrand Disease

The Role of Biomarkers, Metabolomics, and COVID-19 in Venous Thromboembolism-A Review of Literature.

In recent years, the field of venous thromboembolism has undergone numerous innovations, starting from the recent discoveries on the role of biomarkers, passing through the role of metabolomics in expanding our knowledge on pathogenic mechanisms, which have opened up new therapeutic targets. A variety of studies have contributed to characterizing the metabolic phenotype that occurs in venous thromboembolism, identifying numerous pathways that are altered in this setting. Among these pathways are the metabolism of carnitine, tryptophan, purine, and fatty acids. Furthermore, new evidence has emerged with the recent COVID-19 pandemic. Hypercoagulability phenomena induced by this viral infection appear to be related to altered von Willebrand factor activity, alteration of the renin-angiotensin-aldosterone system, and dysregulation of both innate and adaptive immunity. This is the first literature review that brings together the most recent evidence regarding biomarkers, metabolomics, and COVID-19 in the field of venous thromboembolism, while also mentioning current therapeutic protocols.

Von Willebrand factor processing in patients with advanced chronic liver disease and its relation to portal hypertension and clinical outcome

Background and aimsEndothelial dysfunction and portal hypertension (PH) are reflected by increased von Willebrand factor antigen (VWF-Ag) levels in advanced chronic liver disease (ACLD). This study investigated VWF release and cleavage and their association with PH and clinical outcomes.MethodsLevels of VWF-Ag, VWF-N (VWF-propeptide), and VWF-A (VWF processed by the main VWF-cleaving protease ADAMTS13) were assessed in 229 patients with clinically stable ACLD (hepatic venous pressure gradient [HVPG] ≥ 6 mmHg; absence of bacterial infections or acute decompensation) undergoing HVPG-measurement. Liver-healthy individuals served as controls (n = 24).ResultsVWF-Ag and VWF-N were similarly accurate for the identification of clinically significant PH (CSPH; HVPG ≥ 10 mmHg) in compensated ACLD (AUROC: VWF-Ag 0.748; VWF-N 0.728). ADAMTS13 activity was similar between patients with ACLD and controls and did not correlate with PH and disease severity, whereas VWF cleavage decreased in patients with CSPH (i.e., VWF-Ag/-A-ratio increased). In vitro VWF activity strongly reflected VWF-Ag levels (Spearman’s r = 0.874, p < 0.001), but decreased (vs. controls) in patients with CSPH when normalized to VWF-Ag levels (VWF-activity/-Ag-ratio). VWF-Act/-Ag ratio correlated negatively with ADAMTS13 activity (r =– 0.256, p < 0.001). ADAMTS13 activity was independently predictive for (i) portal vein thrombosis (PVT) and (ii) hepatic decompensation or liver-related death.ConclusionsVWF-Ag levels and its propeptide are similarly suitable surrogates of PH in patients with compensated ACLD. ADAMTS13-Act was not linked to disease and PH severity, however, when normalized to VWF-Ag, both VWF cleavage and VWF activity were decreased in patients with CSPH, as compared to liver-healthy individuals. Low ADAMTS13-Act was associated with presumably more procoagulant VWF and adverse outcomes.Clinical trial numberNCT03267615