Prediction of Functional Outcomes at Discharge Using Plasma Concentration of von Willebrand Factor Antigen at Admission in Hospitalized Patients with COVID-19

Background : Von Willebrand factor (VWF) is released from damaged endothelium, and has a role in platelet aggregation through a receptor on the platelet surface. A metalloprotease that cleaves VWF multimers has been identified, namely, ADAMTS13. We recently reported that the serial changes in plasma VWF and ADAMTS13 antigen levels in patients with acute myocardial infarction (AMI), and that the VWF/ADAMTS13 ratio was a useful prognostic indicator of long-term thrombotic events after AMI. Although previous studies have shown raised plasma VWF in patients with atrial fibrillation (AF), little is known about the role of ADAMTS13 in the pathogenesis of AF. In the present study, we examined the relation between VWF and ADAMTS13 in AF patients. Methods and Results : We measured the plasma VWF and ADAMTS13 antigen levels by ELISA in 45 AF patients and 49 control subjects, and also performed echocardiography to examine the relations between these markers and left atrial or ventricular functions. The plasma VWF antigen levels were significantly higher in AF patients compared with controls (2017±749 vs. 1504±497 mU/ml, P=0.0002). In contrast, the plasma ADAMTS13 antigen levels were significantly lower in AF patients compared with controls (825±181 vs. 911±193 mU/ml, P=0.03). The VWF/ADAMTS13 ratio was significantly higher in AF patients compared with controls (2.59±1.20 vs. 1.75±0.76, P<0.0001). The number of patients who received aspirin and warfarin was significantly higher in AF group than control subjects, however, those medical therapy did not affect the VWF and ADAMTS13 antigen levels. There was significant positive correlation between VWF antigen levels and the left atrial dimension (n=128, r=0.228, P=0.0095). Furthermore, there was significant negative correlation between VWF antigen levels and the left atrial appendage peak flow velocity measured by transesophageal echocardiography (n=23, r=-0.611, p=0.0015). Conclusions : These findings suggest that the balance between VWF and ADAMTS13 levels may play an important role in the intra-atrial thrombus formation in AF patients. The present results would open a new therapeutic target for prevention of thromboembolic complications in AF.

Primary Myeloma Cell Induced Von Willebrand Factor Release from the Endothelium Is Mediated By VEGF and Attenuated By Heparin

Is ≥ 100% the magic number to rule out the laboratory diagnosis of von Willebrand disease based on initial testing?

Background : Increased plasma levels of von Willebrand factor (VWF) has been reported in acute myocardial infarction (AMI), which indicates the injured endothelial damage in occluded coronary arteries. The larger VWF multimers are known to be more active biologically, and are more potent mediators of platelet thromubus formations. Recently, a metalloprotease that cleaves VWF multimers has been identified, namely, VWF-cleaving protease (ADAMTS13). We recently reported reduced ADAMTS13 activity in AMI patients and the importance of this protease in the prognosis after AMI. However, whether ADAMTS13 may affect the pathogenesis of unstable angina (UA) has not been fully elucidated. The purpose of this study is to examine changes in plasma VWF and ADAMTS13 levels in patients with UA. Methods and Results : Plasma VWF and ADAMTS13 levels (mU/ml) were measured in 39 patients with UA, 55 patients with stable exertional angina (SEA) and 47 patients with chest pain syndrome (CPS) at the time of coronary angiography by enzyme-linked immunosorbent assay. We measured these antigen levels after 6 months follow-up period in patients with UA. Plasma VWF antigen levels (mU/ml) increased significantly in patients with UA compared with SEA and CPS (2118.5 ± 810.5, 1571.8 ± 494.2 and 1536.0 ± 526.4, respectively; P < 0.0001 in UA vs. SEA or CPS). Plasma ADAMTS13 antigen levels (mU/ml) decreased significantly in patients with UA than SEA or CPS (741.2 ± 150.9, 875.3 ± 229.0 and 877.3 ± 199.7mU/ml, respectively; P < 0.01 in UA vs. SEA or CPS). Furthermore, there were significant inverse correlations between VWF and ADAMTS13 antigen levels (r = −0.320, P < 0.0001). Plasma VWF and ADAMTS13 antigen levels did not change compared to each level in acute phase in 15 UA patients that the blood samples could be obtained at 6 months follow-up periods. Conclusions : These findings suggested the prolonged endothelial damage in UA and tendency toward platelet thrombus formation at the injury sites after the attacks in patients with UA. The long-term antithrombotic therapy might be needed in those patients.

von Willebrand factor, endothelial dysfunction, and cardiovascular disease.

High plasma level of von Willebrand factor (VWF) is a marker of future cardiovascular events in patients at high risk of coronary artery disease (CAD). The purpose of this study was to examine the changes and the prognostic value of plasma VWF-cleaving protease (ADAMTS13) levels in patients with CAD. Plasma VWF and ADAMTS13 levels were measured in 225 patients with CAD (152 men and 73 women, age, 70.3 +/- 8.9 years, mean +/- SD) and 100 patients without CAD who were age- and gender-matched to the CAD patients (60 men and 40 women, age, 68.6 +/- 8.9 years). The CAD patients had higher VWF and lower ADAMTS13 antigen levels compared to patients without CAD. During 22.3 +/- 10.4 months follow-up period, 20 major adverse cardiac and cerebrovascular events (MACCE) occurred in 222 patients with CAD who could be followed up. Kaplan-Meier analysis demonstrated that CAD patients with high plasma VWF antigen levels were significantly more likely to develop MACCE. Furthermore, eight cardiac and cerebrovascular thrombotic events [acute coronary syndrome (n=4) and cerebral infarction (n=4)] occurred in CAD patients with both high plasma VWF and low ADAMTS13 antigen levels. Multivariate Cox hazards regression analysis identified high plasma VWF and low ADAMTS13 antigen levels as significant and independent predictors of future MACCE and thrombotic events during the follow-up period in CAD patients. Our findings suggest that low plasma ADAMTS13 as well as high VWF level is a useful predictor of cardiac and cerebrovascular events in CAD patients.

A functional deficiency of the enzyme ADAMTS 13 (Fujikawa et al, 2001; Levy et al, 2001) is associated with acute idiopathic and congenital thrombotic thrombocytopaenic purpura. Damaged endothelium and an increased release in von Willebrand factor (VWF) favours platelet activation and aggregation that relies on ADAMTS 13 to prevent formation of microvascular thrombi. ADAMTS 13 is the primary physiological modulator which determines the amounts of VWF in plasma. Increase in plasma levels of the substrate VWF may lead to reciprocal reduction in ADAMTS 13 levels, or an effect on production of ADAMTS 13. We reviewed ADAMTS 13 activity in ‘normal’ adults and children. Anonymous, surplus citrate samples from an unselected adult inpatient group, including a subgroup of intensive care patients, and children admitted to a tertiary intensive care unit (ICU) were analysed to determine if there were any changes in ADAMTS 13 activity and the extent of changes in ‘sick’ patients. ADAMTS 13 activity was measured by collagen binding assay, normal range 66–126%, and inhibitors were determined by mixing patient plasma (1:1) with pooled normal plasma for 1 h at 37°C and ADAMTS 13 activity was then measured (Yarranton et al, 2005); values <50% are considered as positive. Dade Behring VWF:Ag® kit, (Dade Behring Inc, Newark, NJ, USA) was used for the quantitative determination of VWF antigen (VWF:Ag) by immunoturbidimetry (VWF:Ag normal levels: 50–160 iu/dl). IgG antibodies to ADAMTS 13 were detected by an enzyme-linked immunosorbent assay as previously described (Scully et al, 2007). Normal Adults: 62 adults, aged 21–57 years, 36 females and 26 males were tested. The mean ADAMTS 13 for females was 111% (50–183%) and 112% (71–159%) for males. Non-acute children: Ninety-two samples (39 female and 53 male) were included from children attending Great Ormond Street Hospital (out-patients). Dividing the subjects on the basis of age, the mean ADAMTS 13 activity was 84% (13–167%) in subjects <12 months (between 5 and 12 months), 93% (27–154%) in 1–6 year old, 105% (0–201%) in 6–12 year old and 78% (50–121%) in children >12 years. Hospital adults including adults in ICU: One hundred random sequential adult in-patient samples were analysed. Twenty-three samples were from high dependency unit (HDU)/ICU patients (23%) and 35% had ADAMTS 13 activity levels <66%. Of the samples with reduced activity levels, 69% were patients in ICU/HDU (15/35). Dividing samples into those with ADAMTS 13 <66%, VWF:Ag was significantly higher in patients with ADAMTS 13 activity >66% (Wilcoxon rank sum test, P = 0·029) (Fig 1A). Patients with reduced ADAMTS 13 activity did not have a significantly different platelet count [215 × 109/l (39–512 × 109/l)] compared with those patients with normal ADAMTS 13 activity 233 × 109/l (24–636 × 109/l). Increased VWF:Ag level [318·3 (115–591) iu/dl vs. 197·25 (88·5–524·4) iu/dl] shown by ICU patients and half of the ADAMTS 13 activity [47·75 (6·4–126·5)% vs. 84·6 (5–217·2)%] shown by non-ICU patients were independent of the platelet count [200 (39–409) × 109/l vs. 231 (15–636) × 109/l]. Of 35 patients, 20 with ADAMTS 13 activity <66% had IgG antibody levels >4·2%. In one patient, IgG antibody to ADAMTS 13 was 18·4%. (A) ADAMTS 13 activity and VWF:Ag levels in random adult hospitalized samples. Adults with reduced ADAMTS 13 activity (<66%) had a significantly higher VWF:Ag (P = 0·029, Wilcoxon Rank Sum Test) compared with those with a normal ADAMTS 13 activity. (B) Scatter plot of ADAMTS 13 activity (<66%) and VWF:Ag in adult population. Children admitted to ICU: Of 48 children admitted to neonatal or paediatric ICU whose diagnosis was unrecorded, ADAMTS 13 activity was reduced (<66%) in 31 (64%) (mean 38%, range 0–61%) and 17 had normal ADAMTS 13 activity (mean 86%, range 71–104%) (Fig 2A). Between the groups, there was no significant difference in platelet counts (median 261 × 109/l vs. 276 × 109/l). VWF:Ag levels were measured in 38 patients and were raised (>150 iu/dl) in 28/38 patients (73%), but there was no significant difference in VWF:Ag levels between patients of ADAMTS 13 <66% and >66% [195·45 iu/dl (range 86·8–588 iu/dl) vs. 208·1 iu/dl (range 97·9–560·8)]. However, in those with VWF:Ag levels <150 iu/dl, only 2/38 patients had ADAMTS 13 activity <66%, but in those patients with VWF:Ag >150 iu/dl, 16/38 patients had ADAMTS 13 activity <66%. IgG antibodies to ADAMTS 13 were analysed in only 10 samples and were positive in four (>4·2%) with a maximum level of 25%. In adults and children, there was a negative inverse correlation between VWF:Ag and ADAMTS 13 activity (1, 2). (A) ADAMTS 13 activity and VWF:Ag in children admitted to neonatal/paediatric intensive care unit (ICU). The horizontal line represents the mean and the bars indicate the fifth and ninety-fifth percentile. Sixty-four per cent of children had ADAMTS 13 activity <66% and 73% had raised VWF:Ag (>150 iu/dl) levels. (B) ADAMTS 13 activity (<66%) and VWF:Ag levels in children admitted to ICU. Within a normal adult cohort, there would appear to be no difference in ADAMTS 13 activity between males and females with a baseline of 50%. The cohort of ‘non-acute’ children attended outpatients in a specialized tertiary referral hospital. The median ADAMTS 13 activity was within the adult normal range and there was no difference between males and females. However, in children admitted to ICU, 64% had reduced ADAMTS 13 activity and 73% of those measured had VWF:Ag >150 iu/dl. Platelet count was not related to either ADAMTS 13 or VWF:Ag. Samples from random hospital adult patients further demonstrate the relationship between VWF:Ag and ADAMTS 13 activity. In critically ill patients, there are often several synergistic factors that may lead to reduced ADAMTS 13; the rise in VWF:Ag only partially explains the reduction in ADAMTS 13 activity. During sepsis, accumulating ultra large VWF multimers may induce enhanced platelet aggregation, and fibrin deposition contributes to septic organ failure. The systemic inflammatory response associated with cytokine release such as interlukin-6 is known to reduce ADAMTS 13. Systemic activation of coagulation with pronounced thrombin generation (Crawley et al, 2005) may result in degradation of ADAMTS 13. Medical treatments, e.g., noradrenaline may induce the release of VWF, resulting in downregulation of ADAMTS 13. Acute hepatic dysfunction may result in reduced synthesis of ADAMTS 13. One or more of these factors may result in reduced ADAMTS 13 levels. In conclusion, ADAMTS 13 activity in children appears to be similar to adult levels. Hospital admission reduces activity in adults and children, especially within the ICU setting. Further studies in patients with thrombotic or multi-organ failure may suggest a role for ADAMTS 13 in other inflammatory or septic conditions as well as TTP, which may have consequences for treatment. We thank Dr. Scheiflinger (Baxter Bioscience, Austria) for donating rADAMTS-13. Dr Marie Scully is supported by an unrestricted Baxter (UK) research fellowship.

Elevated von Willebrand factor (VWF) levels correlate with higher risk of atherosclerosis-related arterial thrombosis (atherothrombosis). Silencing the VWF gene via small-interfering RNAs (siRNAs) could mitigate this risk. Previous studies successfully delivered siRNA to the endothelium of healthy, wild-type (WT) mice using lipid nanoparticles (LNPs). This study aimed to investigate whether the LNP-siRNA strategy could achieve endothelium-specific Vwf-silencing under diseased conditions of prolonged hypercholesterolemia and atherothrombosis-prone vasculature. Female transgenic mice expressing a variant of human APOE∗3 (ie, APOE∗3-Leiden) and human cholesteryl ester transfer protein (CETP), fed a cholesterol-enriched diet for 18 weeks, received an intravenous injection of LNP-encapsulated siRNA targeting Vwf (siVwf) or scrambled control siRNA at 1.5 mg siRNA/kg. For comparison, the same LNP-siRNAs were administered to young, chow-fed WT mice. Plasma VWF and Vwf mRNA levels were measured 96 hours after injection, with immunofluorescence analysis of lungs and heart aortic root to assess VWF protein expression. APOE∗3-Leiden.CETP mice exhibited elevated plasma VWF levels compared with WT mice, alongside hypercholesterolemia and aortic atherosclerosis. siVwf administration led to over 85% reduction in plasma VWF in both strains, with a strong reduction in lung Vwf mRNA and VWF protein in the pulmonary endothelium. Similarly, siVwf treatment resulted in the virtual absence of VWF protein in the endothelial liningof the aortic root of both nondiseased (WT mice) and atherosclerotic (APOE∗3-Leiden.CETP mice) vessel walls. The LNP-siRNA targeting Vwf strongly reduced plasma and endothelial VWF in mice with hypercholesterolemia and advanced atherosclerosis, indicating feasibility to target endothelial VWF under proatherothrombotic conditions.

Increased Von Willebrand Factor Antigen Clearance in Type 1 Von Willebrand Disease: Investigation of Relationship with ABO Blood Group and Tyr1584Cys Polymorphism.

Low VWF levels in children and lack of association with bleeding in children undergoing tonsillectomy

Novel Insights into the Clinical Phenotype and Pathophysiology Underlying Low VWF Levels: The Low Von Willebrand Factor in Ireland Cohort (LoVIC) Study

Reconstitution of Recombinant Factor VIII In fVIII-/- mice Restores Von Willebrand Factor Homeostasis

BackgroundA vital role in coronary artery disease is played by Von Willebrand factor (VWF), which serves as a bridge between platelets and the subendothelial matrix after vessel damage. The purpose of the study was to assess the validity of plasma VWF antigen (VWF: Ag) levels as a predictor of clinical outcomes after acute myocardial infarction (AMI).MethodsThree hundred and seventy-four patients were studied following coronary angiography, including 209 patients suffering from acute myocardial infarction and 165 healthy participants. Coronary angiography was followed by measurement of plasma VWF: Ag levels. Over a 2-year follow-up period, major adverse cardiopulmonary and cerebrovascular events (MACEs) were the primary endpoint. All-cause mortality was investigated as a secondary endpoint.ResultsWhen compared to controls, patients with AMI had mean plasma VWF: Ag levels that were ~1.63 times higher (0.860 ± 0.309 vs. 0.529 ± 0.258 IU/ml; P < 0.001). The plasma VWF: Ag levels were substantially higher in patients who experienced MACEs after myocardial infarction vs. those without MACEs (1.088 ± 0.253 vs. 0.731 ± 0.252 IU/ml; P < 0.001). For predicting long-term MACEs using the optimal cut-off value (0.7884 IU/ml) of VWF: Ag, ROC curve area for VWF: Ag was 0.847, with a sensitivity of 87.2% and a specificity of 66.3% (95%CI: 0.792–0.902; P = 0.001). Two-year follow-up revealed a strong link between higher plasma VWF: Ag levels and long-term MACEs. At the 2-year follow-up, multivariate regression analysis revealed an independent relationship between plasma VWF: Ag levels and MACEs (HR = 6.004, 95%CI: 2.987–12.070).ConclusionWe found evidence that plasma VWF: Ag levels were independent risk factors for AMI. Meanwhile, higher plasma VWF: Ag levels are associated with long-term MACEs in people with AMI.

Serial Changes in von Willebrand Factor-Cleaving Protease (ADAMTS13) and Prognosis After Acute Myocardial Infarction

Clinical phenotype and pathophysiological mechanisms underlying qualitative low VWF.