Evaluating the Impact of an Institutional Practice Change from Warfarin to Therapeutic Rivaroxaban Post-Fontan Operation

Thrombotic complications post-Fontan operation remain a significant clinical concern and preventing these events is critical to improve patient outcomes. While the optimal strategy for thromboprophylaxis post-Fontan is unclear, recent randomized studies have shown comparable outcomes in patients started on Direct Oral Anticoagulants (DOACs) as compared to either antiplatelet medications (e.g. aspirin) or anticoagulants (e.g. warfarin). Based on this increasing data, the Stollery Children's Hospital (primary pediatric cardiac surgical site for Western Canada) changed the standard thromboprophylaxis strategy in May 2024 from anticoagulation with warfarin (target international normalized ratio (INR) 2-3) to treatment dose rivaroxaban (adult equivalent dose 20 mg daily). The goal of this pilot study was to compare outcomes of the first 20 patients during the rivaroxaban period to the most recent 20 patients prior to the practice change. All patients who underwent Fontan procedure March/2023-April/2024 (warfarin cohort) and May/2024-September/2025 (rivaroxaban cohort) were identified and data on bleeding/thrombotic outcomes, length of hospital stay, and laboratory monitoring was collected through retrospective review of the electronic medical record including from surgical admission until 30 days post-discharge. All patients started on rivaroxaban had peak-rivaroxaban-calibrated-anti-Xa used to monitor dosing. During the study period, no significant bleeding or thrombotic events occurred post initiation of rivaroxaban, in the warfarin cohort there was one episode of clinically relevant non-major bleeding. Results suggest that thromboprophylaxis post-Fontan procedure with treatment dose rivaroxaban had similar early outcomes to warfarin. Future work is needed to validate these results in a larger cohort and include longer-term patient outcomes.