The Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2 virus, according to stipulations, claimed about 18,2 million lives until December 31, 2021. The COVID-19 generates a hypercoagulability state. Therefore, the main guidelines recommend thromboprophylaxis in hospitalized COVID-19 patients. However, doubts remain about the use of Low-Molecular-Weight Heparin (LMWH).

To analyze the incidence of venous thromboembolism in hospitalized patients with COVID-19 in the regime of thromboprophylaxis with LMWH.

This systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) rules. EMBASE and PubMed were the selected databases. The following health descriptors were used: “venous thromboembolism” “COVID-19”, “coronavirus disease 2019”, “anticoagulant”and “anticoagulants agent”. Two authors independently performed a systematic literature search in databases. A search encompassed that was published between 01/01/2019 until 31/12/2021. The studies eligible for inclusion had a population over 18 years old, with confirmed diagnosis of COVID-19, hospitalized, and all population did use exclusively LMWH Articles were excluded if they did not provide data about Prophylactic Anticoagulation Regimen (PAR) and if they are case reports. Two authors (E.O.C and J.R.N.P) realized the data collection process, in an independent form.

Our search found 202 articles, of which 80 were duplicates. A total of 122 titles were excluded after reading the title and abstract. Therefore, 17 articles were selected for reading the full-text. In this step, 5 titles were excluded, because they don't give information about the PAR and 3 because they don't use LMWH exclusively. So, we selected 9 titles. A total of 1614 participants, from 8 countries, submitted to prophylaxis with LMWH. Being that 160 participants (9.91%) had a venous thromboembolic event. 6 articles gave information about bleeding that occurred with 43 participants (3%).

According to our article, the presence of venous thrombotic events was found in 18% to 37% of hospitalized patients who had not used prophylactic anticoagulation. The greater susceptibility to thrombotic events in patients infected with SARS-CoV-2 remains under study, however some hypotheses have already been pointed out. Among them, virus entry into cells through angiotensin S receptors (ACE2), widely expressed in lung cells, myocardium and other endothelial cells. Injury to these cells triggers an inflammatory process with the release of more cytokines and consequent pro-coagulant stimulus. Added to this factor is the ability of the virus to bind to ACE2 receptors to cause abnormal activation of the renin-angiotensin axis, leading to platelet aggregation and increased thromboembolic risk. The group of patients positive for VTE and infected by SARS-CoV-2 had a decrease in lymphocyte count and an increase in serum levels of D-Dimer.

The proportion of thrombotics events in hospitalized patients diagnosed with COVID-19 is 18% to 37%, without prophylactic anticoagulation. Our research demonstrated that less than half of the population submitted to prophylaxis anticoagulation evolved to venous thromboembolic events.