Increased Histone-DNA Complexes and Endothelial-Dependent Thrombin Generation in Severe COVID-19

ObjectiveCoagulopathy in severe COVID-19 is common but poorly understood. The purpose of this study was to determine how SARS-CoV-2 infection impacts histone levels, fibrin structure, and endogenous thrombin potential in the presence and absence of endothelial cells. ApproachWe studied individuals with SARS-CoV-2 infection and acute respiratory distress syndrome at the time of initiation of mechanical ventilation compared to healthy controls. Blood samples were assayed for levels of histone-DNA complexes. Confocal microscopy was used to evaluate fibrin structure in clots formed from recalcified plasma samples using fluorescently-labeled fibrinogen. Endogenous thrombin potential was measured by calibrated automated thrombin assays in the presence of tissue factor and phospholipid (PCPS) or cultured human endothelial cells. ResultsCirculating nucleosomes were elevated in the plasma of COVID-19 patients relative to healthy controls (n=6, each group). COVID-19 patient plasma thrombin generation was also altered. Despite having an increased endogenous thrombin potential, patient plasma samples exhibited prolonged lag times and times to peak thrombin in the presence of added tissue factor and PCPS. Strikingly different results were observed when endothelial cells were used in place of tissue factor and PCPS. Control plasma samples did not generate measurable thrombin (lag time >60 min); in contrast, plasma samples from COVID-19+ patients generated thrombin (mean lag time [~]20 min). Consistent with the observed alterations in thrombin generation, clots from COVID-19 subjects exhibited a denser fibrin network, thinner fibers and lower fibrin resolvability. ConclusionsElevated histones, aberrant fibrin formation, and increased endothelial-dependent thrombin generation in COVID-19 may contribute to coagulopathy. HIGHLIGHTSO_LIHistone-DNA complexes are significantly elevated in the plasma of patients with severe SARS-CoV-2 infection. C_LIO_LIMeasures of thrombin generation by calibrated automated thrombography and fibrin clots formed in situ are altered in severe COVID-19. C_LIO_LIPlasma from COVID-19 patients promotes thrombin generation on cultured endothelial cells in the absence of added tissue factor or phospholipids. C_LIO_LIThe additive effects of histones on thrombin generation and endothelial cell function may play a major role in the thrombotic complications observed in severe SARS-CoV-2 infection. C_LI

Heparin for Moderately Ill Patients with Covid-19

BackgroundHeparin, in addition to its anticoagulant properties, has anti-inflammatory and potential anti-viral effects, and may improve endothelial function in patients with Covid-19. Early initiation of therapeutic heparin could decrease the thrombo-inflammatory process, and reduce the risk of critical illness or death. MethodsWe randomly assigned moderately ill hospitalized ward patients admitted for Covid-19 with elevated D-dimer level to therapeutic or prophylactic heparin. The primary outcome was a composite of death, invasive mechanical ventilation, non-invasive mechanical ventilation or ICU admission. Safety outcomes included major bleeding. Analysis was by intention-to-treat. ResultsAt 28 days, the primary composite outcome occurred in 37 of 228 patients (16.2%) assigned to therapeutic heparin, and 52 of 237 patients (21.9%) assigned to prophylactic heparin (odds ratio, 0.69; 95% confidence interval [CI], 0.43 to 1.10; p=0.12). Four patients (1.8%) assigned to therapeutic heparin died compared with 18 patients (7.6%) assigned to prophylactic heparin (odds ratio, 0.22; 95%-CI, 0.07 to 0.65). The composite of all-cause mortality or any mechanical ventilation occurred in 23 (10.1%) in the therapeutic heparin group and 38 (16.0%) in the prophylactic heparin group (odds ratio, 0.59; 95%-CI, 0.34 to 1.02). Major bleeding occurred in 2 patients (0.9%) with therapeutic heparin and 4 patients (1.7%) with prophylactic heparin (odds ratio, 0.52; 95%-CI, 0.09 to 2.85). ConclusionsIn moderately ill ward patients with Covid-19 and elevated D-dimer level, therapeutic heparin did not significantly reduce the primary outcome but decreased the odds of death at 28 days. Trial registration numbers: NCT04362085; NCT04444700