Study: Venous or arterial thrombosis and deaths among COVID-19 cases: a European network cohort study. Image Credit: MattLphotography/Shutterstock

Incidence of arterial and venous thromboembolism and death in COVID-19 patients

In a recent study published in Infectious diseasesresearchers estimated the incidence of arterial or venous thrombosis in patients with coronavirus disease 2019 (COVID-19).

Study: Venous or arterial thrombosis and death among COVID-19 cases: a European network cohort study. Image Credit: MattLphotography/Shutterstock


COVID-19 could cause arterial/venous thromboembolism due to inflammation, platelet activation, endothelial dysfunction and stasis. Various researchers have studied the risk of venous thromboembolism in patients hospitalized with COVID-19. However, these studies were relatively smaller, varying in sample size, setting, and definition of outcomes, resulting in substantial heterogeneity. Additionally, they focused only on hospitalized COVID-19 patients, and the incidence of thrombotic events in non-hospitalized COVID-19 patients remains unknown.

Certain patient-related factors like advanced age, obesity, hypertension and diabetes are associated with high risk of hospitalization and mortality in COVID-19. Some of these factors have already been reported to predispose people to thrombotic events. Furthermore, the associations between thrombotic events and characteristics of COVID-19 patients have not yet been elucidated.

About the study

In the present study, researchers investigated the incidence of arterial and venous thromboembolism and mortality in patients with COVID-19. A network cohort study was conducted using healthcare data from the United Kingdom (UK), Spain, Germany, Italy and the Netherlands. The primary analyzes included two cohorts; the first cohort included people diagnosed with COVID-19. The second included hospitalized COVID-19 patients – one year of observation prior to study enrollment was required for individuals in either cohort to be eligible for primary analyses.

The index date was defined as the date of occurrence/COVID-19 test for those in the first cohort and the date of hospitalization for those in the second cohort. For sensitivity analysis, cohorts were established based on 1) clinical diagnosis alone, 2) clinical diagnosis with less specific codes for identification of COVID-19, 3) proprietary chain reaction tests by polymerase (PCR) and 4) COVID-19 tests (both antigen and PCR assays). These cohorts also had to have one year of observation before being included in the study.

The primary endpoints were arterial or venous thrombotic events and death within 90 days of the index date. Venous thrombotic events were identified by codes of deep vein thrombosis or pulmonary embolism. Arterial thromboembolism has been identified as ischemic stroke or myocardial infarction.

Cox models were used to assess associations between pre-specified variables and the risk of thrombotic events and death. The cumulative incidence of study outcomes was estimated and stratified by gender and age. The effect of thrombotic events on COVID-19 outcomes was assessed with a multistate model.


The study included over 0.9 million individuals with an index date of September 1, 2020 or later. Over 415,000 of the attendees were from the UK, over 38,000 from the Netherlands, Germany, Spain and 25,759 from Italy. The second cohort had 32,329 hospitalized patients, all from Spain. The median age varied by region, and women outnumbered men in COVID-19 cases in the overall sample. The median age was 67 years in the second cohort, with a significant proportion of men. More than 23,200 were comorbid or had previously received medication.

The 90-day cumulative incidence of venous thrombotic events in people with a diagnosis of COVID-19 or a positive SARS-CoV-2 PCR test ranged from 0.21% in the Netherlands to 0.8% in Spain, although it is 4.5% for people in the hospitalized cohort. Similarly, the cumulative incidence of arterial thromboembolism ranged from 0.06% in the UK and Italy to 0.79% in Spain, increasing further to 3.08% among hospitalized patients. Mortality was less than 2% for those in the first cohort but increased by 14.61% among those hospitalized.

Stratified by age, arterial/venous thrombotic events and deaths were more common in people aged 65 or older; however, this pattern has not been observed for venous thromboembolism in hospitalized patients. Men had a higher risk of arterial thromboembolism and death, while men from the Netherlands, the UK and Spain, but not Germany or Italy, had increased risks of venous thromboembolism.

Hazard ratios (HRs) after adjusting for gender revealed that outpatient venous thromboembolism was associated with hospitalization (HR: 1.36) and death (4.42). Similarly, hospitalized patients were associated with an increased risk of mortality (1.63). Ambulatory arterial thrombotic events increased the risk of death (3.16), but not hospitalization, and similarly, in the hospital setting, the risk of death was also higher (1.93).


The present study calculated the incidence of thromboembolism and death among COVID-19 patients. For non-hospitalized patients, the cumulative incidence of venous thromboembolism was 0.2% to 0.8% and 0.1% to 0.8% for arterial thrombotic events. The hospitalized cohort showed the highest incidence of 4.5% and 3.1% for venous and arterial thromboembolism.

Although the 90-day lethality never exceeded 2% for non-hospitalized patients, it was much higher (14.6%) for hospitalized subjects. After adjustments, men had a much higher risk of thrombotic events and death. The results showed that thrombotic events were associated with severe COVID-19-related outcomes and mortality, underpinning the need to develop strategies to reduce their incidence.

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