PB0956 - The efficacy and safety of direct oral anticoagulants (DOACs) in the secondary prevention of VTE in individuals with inherited antithrombin deficiency: a cohort study from a tertiary referral centre

Background: Inherited antithrombin deficiency (ATD) is a thrombophilia associated with a high risk of venous thromboembolism (VTE). While most cases of VTE are now managed with direct oral anticoagulants (DOACs), the efficacy of DOACs in ATD is unreported due to few known cases being included in trials.

Aims: Review thrombotic and bleeding outcomes in patients with ATD treated with DOACs at our institution.

Methods: We identified patients with ATD treated with DOAC from our institutions’ antithrombin deficiency registry. We assessed patients’ characteristics, ATD type, and initial VTE characteristics with the outcomes of thrombosis recurrence and bleeding rates.

Results: 32 patients were identified who received DOACs for a median of 80 months (IQR 56, 116). There were no VTE recurrences on standard dose DOAC, except in a noncompliant patient receiving dabigatran. There was one reported thrombosis recurrence with compliant DOAC use – in a patient receiving rivaroxaban 10mg daily (event rate 3.4 events/100 patient-years for low-dose DOACs). An additional 11 (34%) patients had a VTE recurrence in the study period – however these occurred after anticoagulation was ceased (four), nonadherence to VKA prior to DOAC use (two), or related to pregnancy and postpartum (five). Six (19%) patients experienced clinically-relevant bleeding, which was predominantly menorrhagia (5/6). One major bleeding event, intracranial haemorrhage, occurred in a patient receiving full-dose rivaroxaban who also had refractory hypertension – 0.5 events/100 patient-years.

Conclusion(s): In this cohort, DOACs appear to be effective in terms of efficacy and safety in the management of patients with inherited ATD.