Suppression of Fibrinolysis and Hypercoagulability, Severity of Hypoxemia, and Mortality in COVID-19 Patients: A Retrospective Cohort Study

Abstract

Background: COVID-19 causes hypercoagulability, but the association between coagulopathy and hypoxemia in critically ill patients has not been thoroughly explored. This study hypothesized that severity of coagulopathy would be associated with acute respiratory distress syndrome severity, major thrombotic events, and mortality in patients requiring intensive care unit-level care.

Methods: Viscoelastic testing by rotational thromboelastometry and coagulation factor biomarker analyses were performed in this prospective observational cohort study of critically ill COVID-19 patients from April 2020 to October 2020. Statistical analyses were performed to identify significant coagulopathic biomarkers such as fibrinolysis-inhibiting plasminogen activator inhibitor 1 and their associations with clinical outcomes such as mortality, extracorporeal membrane oxygenation requirement, occurrence of major thrombotic events, and severity of hypoxemia (arterial partial pressure of oxygen/fraction of inspired oxygen categorized into mild, moderate, and severe per the Berlin criteria).

Results: In total, 53 of 55 (96%) of the cohort required mechanical ventilation and 9 of 55 (16%) required extracorporeal membrane oxygenation. Extracorporeal membrane oxygenation-naïve patients demonstrated lysis indices at 30 min indicative of fibrinolytic suppression on rotational thromboelastometry. Survivors demonstrated fewer procoagulate acute phase reactants, such as microparticle-bound tissue factor levels (odds ratio, 0.14 [0.02, 0.99]; P = 0.049). Those who did not experience significant bleeding events had smaller changes in ADAMTS13 levels compared to those who did (odds ratio, 0.05 [0, 0.7]; P = 0.026). Elevations in plasminogen activator inhibitor 1 (odds ratio, 1.95 [1.21, 3.14]; P = 0.006), d-dimer (odds ratio, 3.52 [0.99, 12.48]; P = 0.05), and factor VIII (no clot, 1.15 ± 0.28 vs. clot, 1.42 ± 0.31; P = 0.003) were also demonstrated in extracorporeal membrane oxygenation-naïve patients who experienced major thrombotic events. Plasminogen activator inhibitor 1 levels were significantly elevated during periods of severe compared to mild and moderate acute respiratory distress syndrome (severe, 44.2 ± 14.9 ng/ml vs. mild, 31.8 ± 14.7 ng/ml and moderate, 33.1 ± 15.9 ng/ml; P = 0.029 and 0.039, respectively).

Conclusions: Increased inflammatory and procoagulant markers such as plasminogen activator inhibitor 1, microparticle-bound tissue factor, and von Willebrand factor levels are associated with severe hypoxemia and major thrombotic events, implicating fibrinolytic suppression in the microcirculatory system and subsequent micro- and macrovascular thrombosis in severe COVID-19.

Figure 1:

Patients with severe COVID-19 demonstrate procoagulant profile on ROTEM, marked by shortened Clot Formation Time (B and G), increased alpha angle (C and H), and reduced Lysis at 30 minutes after clotting time (CT) (E and J) on EXTEM and INTEM, and elevated maximum clot firmness on EXTEM, INTEM, and FIBTEM (D, I, and M). ECMO alters coagulative phenotype of COVID-19 patients, increasing average CFT (B and G) and lowering alpha angle (C and H) and MCF (D and I) into the normal range. Extrinsic coagulation time was normal (A), though drifted longer in INTEM due to anticoagulation with low molecular weight heparin (F). Grey bar indicates range of normal clinical values. Each dot represents a single patient timepoint. Significant one-way ANOVAs were followed by Tukey’s post-hoc comparisons shown in figures. P<0.05 was considered significant. * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001, and non-significant p-values are written out. Values plotted as mean +/− SD. Representative INTEM tracings from a healthy donor (K) and an ICU patient on study (L) are included for reference, with the initial green line representing coagulation time, the pink triangle clot formation time, the angle of incidence of the clot formation time as alpha angle, the thickest aspect of the tracing as maximum clot firmness, and the residual clot firmness amplitude in percentage of maximum clot firmness (MCF) at 30 min after clotting time (CT) as Lysis index at 30 minutes.

Figure 2:

Coagulative parameters for patients with and without significant thrombotic events (clot) during hospitalization, separated by ECMO status (ECMO). Regardless of ECMO status, elevations in plasminogen activator inhibitor-1 (C), von Willebrand Factor (E), and factor VIII (D) associated with thrombotic events. Neither fibrinogen (A) nor ADAMTS13 levels (F) had variance accounted for by thrombotic events, though A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) levels were lower in non-ECMO patients who had a thrombotic event (F). D-dimer levels were markedly elevated in ECMO patients who had a thrombotic event (B), which drives the significant interaction term of clot x ECMO (B). P-values shown on graphs from top to bottom are the p-values for variance accounted for by clotting term (p_clot), ECMO term (p_ecmo), and clotting x ECMO term (p_{clot x ecmo}) respectively in a two-way ANOVA for clot x ECMO. Dotted line indicates the mean of normal healthy values for swift comparison. Values plotted as mean +/− SD.

Figure 3:

Markers of endothelial damage like plasminogen activator inhibitor-1(PAI-1) and microparticle-bound tissue factor (MP-Tissue Factor) are elevated in severe Acute Respiratory Distress Syndrome (ARDS) compared to mild and moderate ARDS. Mild ARDS is defined as PaO2/FiO2 between 300 and 200, Moderate as PaO2/FiO2 between 100 and 200, and Severe as PaO2/FiO2 <100. Values are plotted as mean +/− SD. Dotted line indicates the mean of healthy normal where available. Significant one-way ANOVA for PAI-1 was followed by Tukey’s post-hoc comparison between groups displayed in the figure. P<0.05 was considered significant. * p<0.05, and non-significant p-values are written out.