Elevated Risk of Venous Thromboembolism in COVID Patients

A retrospective cohort study published on August 16, 2022, found that patients hospitalized for COVID-19 had an elevated risk of venous thromboembolism (VTE) compared to those hospitalized for the flu. According to the National Heart, Lung, and Blood Institute, VTE is more commonly referred to as a blood clot.

VTE can include pulmonary embolism (PE) and deep vein thrombosis (DVT). The CDC defines DVT as “a medical condition that occurs when a blood clot forms in a deep vein. These clots usually develop in the lower leg, thigh, or pelvis, but they can also occur in the arm.” PE occurs when the clots travel to the lungs.

According to the NIH, an increased risk of VTE can occur after surgery or with medical conditions including stroke, obesity, spinal cord injury, heart conditions, and cancer.

In this study, researchers looked at hospital diagnoses of arterial thromboembolism and venous thromboembolism within 90 days in COVID and influenza patients.

Participants in the COVID-19 cohort were patients over 18 with a COVID diagnosis between April 1, 2020, and May 31, 2021. The participants in the other cohort were adults over 18 who had an influenza diagnosis between October 1, 2018, and April 30, 2019.

While the rates of arterial thromboembolism did not differ significantly between the two groups, the rates of VTE did. The study found that the 90-day absolute VTE risk for patients with influenza was 5.3%. Conversely, for patients with COVID-19, the rate was 4.2% higher.

Researchers in the publication proposed some possible reasoning for this discrepancy stating that “the SARS-CoV-2 infection of endothelial cells incites inflammation and abnormalities in coagulation, such as an increased abundance of antiphospholipid antibodies and enhanced platelet activity. These abnormalities might be more marked in patients with COVID-19 versus in patients with influenza infections.”

While this study displayed a difference in VTE rates between the two cohorts, the publication had a few limitations. Of the eight limitations mentioned by the researchers, one included greater awareness of VTE in COVID patients, which may be associated with higher testing rates. Further studies should be done to analyze the differences between VTE rates.

“Based on data from a US public health surveillance system, hospitalization with COVID-19 before and during vaccine availability, versus hospitalization with influenza in 2018 and 2019, was significantly associated with a higher risk of venous thromboembolism within 90 days, but there was no significant difference in the risk of arterial thromboembolism within 90 days,” concluded researchers in the publication.