Non-severe COVID-19 is associated with endothelial damage and hypercoagulability despite pharmacological thromboprophylaxis

Abstract

Background: Hypercoagulability and endothelial dysfunction are hallmarks of coronavirus disease 2019 (COVID-19) and appear to predict disease severity. A high incidence of thrombosis despite thromboprophylaxis is reported in patients with moderate to severe COVID-19. Recent randomized clinical trials suggest that therapeutic-intensity heparin confers a survival benefit in moderate-severity COVID-19 compared to standard-intensity heparin, potentially by harnessing heparin-mediated endothelial-stabilizing and anti-inflammatory effects.

Objective: We hypothesized that patients with moderate-severity COVID-19 exhibit enhanced hypercoagulability despite standard-intensity thromboprophylaxis with low molecular weight heparin (LMWH) compared to non-COVID-19 hospitalized patients.

Methods: Patients with moderate COVID-19 and a control group (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]-negative hospitalized patients) receiving LMWH thromboprophylaxis were recruited. Markers of endothelial damage and plasma thrombin generation parameters were assessed.

Results: Tissue plasminogen activator levels were significantly increased in the COVID-19 group (8.3 ± 4.4 vs. 4.9 ± 2.4 ng/ml; P = .02) compared to non-COVID-19-hospitalized patients. Despite thromboprophylaxis, mean endogenous thrombin potential was significantly increased among COVID-19 patients (1929 ± 448 vs. 1528 ± 460.8 nM*min; P = .04) but lag time to thrombin generation was significantly prolonged (8.1 ± 1.8 vs. 6.2 ± 1.8 mins; P = .02). While tissue factor pathway inhibitor (TFPI) levels were similar in both groups, in the presence of an inhibitory anti-TFPI antibody, the difference in lag time between the groups was abrogated.

Conclusions: Collectively, these data demonstrate that COVID-19 of moderate severity is associated with increased plasma thrombin generation and endothelial damage, and that hypercoagulability persists despite standard LMWH thromboprophylaxis. These findings may be of clinical interest given recent clinical trial data which suggest escalated heparin dosing in non-severe COVID-19 may be associated with improved clinical outcomes.

Keywords: COVID-19; endothelium; heparin; thrombosis; venous thromboembolism.

FIGURE 1

Plasma tissue plasminogen activator (t‐PA) levels are significantly elevated in coronavirus disease 2019 (COVID‐19). Plasma levels of t‐PA (A) were significantly elevated in hospitalized patients with non‐severe COVID‐19 (n = 14) compared to a group of hospitalized patients (n = 11) who had screened negative for severe acute respiratory syndrome coronavirus 2 by real‐time polymerase chain reaction. Levels of soluble thrombomodulin (sTM; B), vascular cell adhesion molecule‐1 (VCAM‐1; C), intercellular adhesion molecule‐1 (ICAM‐1; D), plasminogen activator inhibitor‐1 (PAI‐1; E) and E‐selectin (F) were similar in both groups. All samples were assayed in technical duplicate. Data are presented as the mean ± standard deviation. Statistical analysis was performed using a two‐tailed Student’s t test. *P < .05

FIGURE 2

Plasma levels of tissue factor plasma inhibitor (TFPI) were similar in the group of patients with non‐severe coronavirus disease 2019 (COVID‐19; n = 11) and the group of hospitalized patients (n = 7) who had tested negative for severe acute respiratory syndrome coronavirus disease 2 (SARS‐CoV‐2) by real‐time polymerase chain reaction (A). Representative thrombin generation curves from a patient with COVID‐19 and a SARS‐CoV‐2–negative hospitalized control before and after incubation with an inhibitory antibody directed against TFPI are shown in (B). At baseline, the lag time to thrombin generation was prolonged in the COVID‐19 group but in the presence of the antibody directed against TFPI, lag time became shortened and no significant difference was observed between the COVID‐19 patients and hospitalized controls (C). All samples were assayed in technical duplicates. Data are presented as the mean ± standard deviation. Thrombin generation curves each describe the mean of duplicate replicates from an individual patient’s plasma. Statistical analysis was performed using a two‐tailed Student’s t test and P‐values were adjusted for multiple comparisons using a Bonferroni post hoc test. *P < .05; **P < .01; ***P ≤ .001