Introduction
Coronavirus disease 2019 (COVID-19) is an infectious disease caused by
the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).
Besides respiratory failure, COVID-19 also has high rates of
thromboembolic complications as seen in multiple retrospective
studies.1–3 In accordance, autopsy studies showed
high incidences of macro- and microemboli in patients who were infected
by SARS-CoV-2.4,5 These thrombotic complications could
be responsible for a significant part of the morbidity and mortality
seen in COVID-19 patients.3 The exact underlying
pathophysiology of COVID-19 related thrombotic complications remains
unknown, but excessive inflammation, hypoxia, immobilization, thrombotic
microangiopathy, diffuse intravascular coagulation, and complement
activation most likely play a role.6 Moreover,
low-molecular-weight heparin (LMWH) thromboprophylaxis seems to decrease
mortality in patients with COVID-19.15
Based on these data, guidelines recommend administration of prophylactic
LMWH for all hospitalized patients with COVID-19.16,17However, recent reports show that despite the use of apparently adequate
thrombosis prophylaxis, the incidence of venous thromboembolism (VTE) in
COVID-19 patients who were admitted to a hospital ward appears to be
much higher compared to patients with other infectious
diseases.2,18,19 Therefore, it was suggested that in
COVID-19 patients increased intensity thromboprophylaxis or therapeutic
anticoagulation should be considered.16,21,22 However,
studies that address the effect of therapeutic anticoagulation on
clinical outcomes show conflicting results, and often compare very
heterogeneous cohorts that lack statistical power to draw firm
conclusions.23–27 The aim of this study is to
investigate the beneficial effect of therapeutic anticoagulation used
prior to hospitalization on morbidity and mortality in a large cohort of
hospitalized COVID-19 patients.