COVID-19 and Recurrent Venous Thromboembolism (CORE-VTE).

Background: Venous thromboembolism (VTE) events occur in association with COVID-19, and the optimal duration of anticoagulant treatment is uncertain.

Objectives: The primary objectives were to determine the duration of anticoagulant prescriptions filled after COVID-19-associated VTE and the proportion of patients experiencing VTE recurrence. The secondary objective was to determine the proportion of patients who experienced bleeding events.

Methods: This retrospective cohort study analyzed data for cases of COVID-19-associated VTE across Alberta, Canada, confirmed between February 23, 2020, and June 30, 2022. Outpatient cases of VTE were identified using codes from the International Classification of Diseases, Ninth Revision plus Alberta Health Service procedure codes. Inpatient cases of VTE and bleeding events were identified using codes from the International Classification of Diseases and Related Health Problems, 10th Revision.

Results: Among the 822 patients included in the analysis, median follow-up was 359.0 days, with the majority of follow-up occurring while patients were off treatment (median 273.0 days). The median age was 59 years, 61.9% of the patients were male, 82.1% had a pulmonary embolism, 71.9% had not received COVID-19 vaccinations, and the median Charlson comorbidity index score was 1. The median duration of treatment was 100.0 (interquartile range 71.0-190.0) days, with 360 patients (43.8%) filling their prescriptions for 0-3 months, 234 (28.5%) for 4-6 months, 181 (22.0%) for 7-12 months, and 47 (5.7%) for more than 12 months. Overall, recurrent VTE occurred in 49 patients (6.0%), 24 of whom had continuously filled their anticoagulant prescriptions up to the time of the event. Bleeding occurred in 72 patients (8.8%).

Conclusions: Given the prolonged follow-up period off anticoagulant treatment for most patients, it is reasonable to consider 3-6 months of therapy for COVID-19-associated VTE.