HF and LT contributed equally to this study. SummaryAlthough the pathophysiology underlying severe COVID19 remains poorly understood, accumulating data suggest that a lung-centric coagulopathy may play an important role. Elevated D-dimer levels which correlated inversely with overall survival were recently reported in Chinese cohort studies. Critically however, ethnicity has major effects on thrombotic risk, with a 3-4-fold lower risk in Chinese compared to Caucasians and a significantly higher risk in African-Americans. In this study, we investigated COVID19 coagulopathy in Caucasian patients. Our findings confirm that severe COVID19 infection is associated with a significant coagulopathy that correlates with disease severity. Importantly however, Caucasian COVID19 patients on low molecular weight heparin thromboprophylaxis rarely develop overt disseminated intravascular coagulation (DIC). In rare COVID19 cases where DIC does develop, it tends to be restricted to late-stage disease. Collectively, these data suggest that the diffuse bilateral pulmonary inflammation observed in COVID19 is associated with a novel pulmonary-specific vasculopathy termed pulmonary intravascular coagulopathy (PIC) as distinct to DIC. Given that thrombotic risk is significantly impacted by race, coupled with the accumulating evidence that coagulopathy is important in COVID19 pathogenesis, our findings raise the intriguing possibility that pulmonary vasculopathy may contribute to the unexplained differences that are beginning to emerge highlighting racial susceptibility to COVID19 mortality.

Critical clinical questions remain unanswered regarding diagnosis and management of patients with low von Willebrand factor (VWF) levels (30-50 IU/dL). To address these questions, the Low VWF Ireland Cohort (LoVIC) study investigated 126 patients registered with low VWF levels. Despite marginally reduced plasma VWF levels, International Society of Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH BAT) confirmed significant bleeding phenotypes in the majority of LoVIC patients. Importantly, bleeding tendency did not correlate with plasma VWF levels within the 30 to 50 IU/dL range. Furthermore, bleeding phenotypes could not be explained by concurrent hemostatic defects. Plasma factor VIII to VWF antigen (VWF:Ag) ratios were significantly increased in LoVIC patients compared with controls ( < .0001). In contrast, VWF propeptide to VWF:Ag ratios >3 were observed in only 6% of the LoVIC cohort. Furthermore, platelet-VWF collagen binding activity levels were both significantly reduced compared with controls ( < .05). In response to 1-desamino-8-D-arginine vasopressin (DDAVP), peak VWF:Ag levels exceeded 100 IU/dL in 88% of patients and was sustained >100 IU/dL after 4 hours in 72% of subjects. In conclusion, our novel data suggest that low VWF levels can be associated with significant bleeding and are predominantly due to reductions in VWF synthesis and/or constitutive secretion. Although enhanced VWF clearance may contribute to the pathophysiology in some individuals, the absolute reduction in VWF plasma half-life is usually mild and not sufficient to significantly impact upon the duration of DDAVP-induced VWF response. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

Background Persistent symptoms including breathlessness, fatigue and decreased exercise tolerance have been reported in patients after acute SARS‐CoV‐2 infection. The biological mechanisms underlying this ‘ Long COVID ’ syndrome remain unknown. However, autopsy studies have highlighted the key roles played by pulmonary endotheliopathy and microvascular immunothrombosis in acute COVID‐19. We hypothesized that endothelial cell activation may be sustained in convalescent COVID‐19 patients and contribute to Long COVID pathogenesis. Patients and Methods Fifty patients were reviewed at a median of 68 days following SARS‐CoV‐2 infection. In addition to clinical workup, acute phase markers, EC activation and NETosis parameters and thrombin generation were assessed. Results Thrombin generation assays revealed significantly shorter lag times (p<0.0001, 95% CI ‐2.57– ‐1.02min), increased endogenous thrombin potential (ETP) (p=0.04, 95% CI 15–416nM/min) and peak thrombin (p<0.0001, 95% CI 39–93nM) in convalescent COVID‐19 patients. These pro‐thrombotic changes were independent of ongoing acute phase response or active NETosis. Importantly, EC biomarkers including VWF:Ag, VWF propeptide (VWFpp) and Factor VIII (FVIII:C) were significantly elevated in convalescent COVID‐19 compared to controls (p=0.004, 95% CI 0.09–0.57IU/ml; p=0.009, 95% CI 0.06–0.5IU/ml; p=0.04, 95% CI 0.03–0.44IU/ml, respectively). In addition, plasma soluble thrombomodulin (sTM) levels were significantly elevated in convalescent COVID‐19 (p=0.02, 95% CI 0.01–2.7ng/ml). Sustained endotheliopathy was more frequent in older, comorbid patients and those requiring hospitalization. Finally, both plasma VWF:Ag and VWFpp levels correlated inversely with 6‐minute walk tests. Conclusions Collectively, our findings demonstrate that sustained endotheliopathy is common in convalescent COVID‐19 and raise the intriguing possibility that this may contribute to Long COVID pathogenesis.

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Gynecological bleeding is frequently reported in women with von Willebrand disease (VWD). Low von Willebrand factor (VWF) may be associated with significant bleeding phenotype despite only mild plasma VWF reductions. The contribution of gynecological bleeding to this phenotype has yet to be described. The optimal clinical bleeding assessment tool (BAT) to evaluate bleeding remains unclear. Using a standardized approach to phenotypic assessment, we evaluated gynecological bleeding and directly compared the Condensed Molecular and Clinical Markers for the Diagnosis and Management of type 1 VWD (Condensed MCMDM-1 VWD) and International Society on Thrombosis and Haemostasis (ISTH) BAT scores in 120 women enrolled in the Low von Willebrand in Ireland Cohort study. Heavy menstrual bleeding (HMB) was reported in 89% of female participants; 45.8% developed iron deficiency. Using identical data, Condensed MCMDM-1 VWD menorrhagia domain scores were significantly lower than ISTH BAT scores (2 vs 3; < .0001), the discrepant results related to 40% of women not seeking medical consultation for HMB, reducing the sensitivity of the Condensed score. For those who reported HMB to physicians, the low VWF diagnosis was not expedited (age at diagnosis 34.2 vs 33.4 years in women failing to present; = .7). Postpartum hemorrhage (PPH) was self-reported in 63.5% of parous women (n = 74); 21.6% required transfusion, critical care, radiological, or surgical intervention. Our data demonstrate that gynecological bleeding is frequently reported in women with low VWF; despite pregnancy-related increases in plasma VWF levels, these women may experience PPH. Defining the optimal management approach for these patients requires further research. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Summary Endothelial cell (EC) activation plays a key role in the pathogenesis of pulmonary microvascular occlusion, which is a hallmark of severe coronavirus disease 2019 (COVID‐19). Consistent with EC activation, increased plasma von Willebrand factor antigen (VWF:Ag) levels have been reported in COVID‐19. Importantly however, studies in other microangiopathies have shown that plasma VWF propeptide (VWFpp) is a more sensitive and specific measure of acute EC activation. In the present study, we further investigated the nature of EC activation in severe COVID‐19. Markedly increased plasma VWF:Ag [median (interquatile range, IQR) 608·8 (531–830)iu/dl] and pro‐coagulant factor VIII (FVIII) levels [median (IQR) 261·9 (170–315) iu/dl] were seen in patients with severe severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) infection. Sequential testing showed that these elevated VWF–FVIII complex levels remained high for up to 3 weeks. Similarly, plasma VWFpp levels were also markedly elevated [median (IQR) 324·6 (267–524) iu/dl]. Interestingly however, the VWFpp/VWF:Ag ratio was reduced, demonstrating that decreased VWF clearance contributes to the elevated plasma VWF:Ag levels in severe COVID‐19. Importantly, plasma VWFpp levels also correlated with clinical severity indices including the Sequential Organ Failure Assessment (SOFA) score, Sepsis‐Induced Coagulopathy (SIC) score and the ratio of arterial oxygen partial pressure to fractional inspired oxygen (P/F ratio). Collectively, these findings support the hypothesis that sustained fulminant EC activation is occurring in severe COVID‐19, and further suggest that VWFpp may have a role as a biomarker in this setting.

Background Consistent with fulminant endothelial cell activation, elevated plasma von Willebrand factor (VWF) antigen levels have been reported in patients with COVID‐19. The multimeric size and function of VWF are normally regulated through A Disintegrin And Metalloprotease with ThrombSpondin Motif type 1 motif, member 13 (ADAMTS‐13)‐‐mediated proteolysis. Objectives This study investigated the hypothesis that ADAMTS‐13 regulation of VWF multimer distribution may be impaired in severe acute respiratory syndrome‐coronavirus‐2 (SARS‐CoV‐2) infection contributing to the observed microvascular thrombosis. Patients and Methods Patients with COVID‐19 ( n = 23) were recruited from the Beaumont Hospital Intensive Care Unit (ICU) in Dublin. Plasma VWF antigen, multimer distribution, ADAMTS‐13 activity, and known inhibitors thereof were assessed. Results We observed markedly increased VWF collagen‐binding activity in patients with severe COVID‐19 compared to controls (median 509.1 versus 94.3 IU/dl). Conversely, plasma ADAMTS‐13 activity was significantly reduced (median 68.2 IU/dl). In keeping with an increase in VWF:ADAMTS‐13 ratio, abnormalities in VWF multimer distribution were common in patients with COVID‐19, with reductions in high molecular weight VWF multimers. Terminal sialylation regulates VWF susceptibility to proteolysis by ADAMTS‐13 and other proteases. We observed that both N‐ and O‐linked sialylation were altered in severe COVID‐19. Furthermore, plasma levels of the ADAMTS‐13 inhibitors interleukin‐6, thrombospondin‐1, and platelet factor 4 were significantly elevated. Conclusions These findings support the hypothesis that SARS‐CoV‐2 is associated with profound quantitative and qualitative increases in plasma VWF levels, and a multifactorial down‐regulation in ADAMTS‐13 function. Further studies will be required to determine whether therapeutic interventions to correct ADAMTS‐13‐VWF multimer dysfunction may be useful in COVID‐microvascular thrombosis and angiopathy.