Incidence of venous thromboembolism, recurrence, and bleeding after isolated superficial vein thrombosis: findings from the Venous Thrombosis Registry in Østfold Hospital

Background: There are limited data on the long-term risk of venous thromboembolism (VTE) after high-risk isolated superficial vein thrombosis (iSVT) treated with anticoagulants. Objectives: To determine the short- and long-term risk of VTE and iSVT recurrence after cessation of anticoagulant treatment and to calculate 45-day cumulative bleeding incidence in patients with iSVT. Methods: Between January 2014 and December 2021, 229 patients with high-risk iSVT (ie, thrombus length >= 5cm), without active cancer, with no history of VTE or iSVT, and who had received anticoagulant treatment for the iSVT were identified through the Venous Thrombosis Registry in ostfold Hospital (TROLL registry), Norway. Cumulative incidences of VTE and iSVT recurrence, as well as cumulative incidences of major and clinically relevant nonmajor bleeding events, were assessed. Results: Median age was 60 years (IQR, 48-71), and 125 (55%) were women. Most patients were treated with direct oral anticoagulants (74%), and of these, 79% received a dose of rivaroxaban 10 mg daily. Low-molecular-weight heparin was given to 26% of the patients. The 1- and 5-year cumulative incidences of VTE after iSVT were 4.6% (95% CI, 2.5-8.3) and 15.9% (95% CI, 10.8-22.9), respectively. Further, the 1- and 5year cumulative incidences of iSVT recurrence were 6.5% (95% CI, 3.9-10.7) and 15.9% (95% CI, 10.8-23.1), respectively. The overall 45-day cumulative incidence of major and clinically relevant nonmajor bleeding events was 0.4% (95% CI, 0.06-3.06) and 1.8% (95% CI, 0.7-4.6), respectively. No major bleeding events were observed in patients treated with direct oral anticoagulants. Conclusion: Despite anticoagulant treatment, the risk of VTE after high-risk iSVT was substantial, while bleeding complications were low.