Very elderly patients with venous thromboembolism on oral anticoagulation with VKAs or DOACs: Results from the prospective multicenter START2-Register Study

Abstract

Introduction: Few data are available on the safety of anticoagulation in very elderly patients treated with Vitamin K antagonists (VKAs) and direct oral anticoagulants (DOACs) for venous thromboembolism (VTE).

Methods: We carried out a prospective cohort study on VTE patients aged ≥85 years enrolled in the Survey on anticoagulaTed pAtients RegisTer (START2-Register) on treatment with VKAs or DOACs, with the aim to evaluate mortality, bleeding and thrombotic rates (venous and arterial).

Results: We enrolled 272 patients, 58.7% on VKA and 41.3% on DOACs. Baseline characteristics were similar between treatment groups, with a higher prevalence of renal failure in VKAs patients and of a history of bleeding and previous stroke/TIA in DOACs patients. During follow-up of 429 patient-years, 15 major and non-major clinically relevant bleedings were recorded (rate 3.5 × 100 pt-yrs), 5 were major bleeds (rate 1.2 × 100 pt-yrs), 1 in a patient on aspirin (rate 4.3 × 100 pt-yrs). Bleeding rate was higher in patients on DOACs (crude HR 4.7; 95%CI 1.5-15.01). Eight thrombotic events were recorded (rate 1.9 × 100 pt-yrs), 3 recurrent VTE and 5 stroke/TIA. Overall, the incidence of thrombotic events was higher in DOACs patients (crude HR 4.5; 95% CI 1.5; 13.3). The rate of recurrent VTE was similar in the two group. Mortality rate was significantly lower in DOACs patients (crude HR 0.30; 95% CI 0.1;0.9).

Conclusion: A higher bleeding risk was found in very elderly VTE patients on DOACs despite the wide use of low-dosages. Similarly a higher thrombotic risk was found while the incidence of recurrent VTE was low and similar between the groups. Mortality rate were significantly lower in DOACs patients.

Keywords: Bleeding; Direct oral anticoagulant; Elderly; Venous thromboembolism; Vitamin K antagonist.