Abstract 223: Adherence to Warfarin and Oral Anticoagulants: Outcomes of 12 Months Follow-up in Patients With Non-valvular Atrial Fibrillation

Abstract

Adherence to direct oral anticoagulants (DOACs) or vitamin K antagonists (warfarin) is an essential element of anticoagulation effectiveness and can be related to the outcomes of long-term therapy. Multiple studies have proved that patients with atrial fibrillation (AF) can be effectively treated with oral anticoagulants, achieving reduced morbidity and mortality which is mostly associated with stroke due to thromboembolism. However, despite these DOACs offering some potential advantages over vitamin K antagonists, their usage in the US has been slow to increase, and information on adherence and clinical outcomes based on real-world data is still limited. The goal of this retrospective study was to identify any distinct characteristics of patients with atrial fibrillation who received initial anticoagulation therapy with warfarin versus those who received DOACs. In addition, follow-up for at least the first 12 months of anticoagulation therapy was assessed for adherence to the prescribed anticoagulant or the reasons for change. Methods: This IRB approved study was conducted at Hartford Hospital using data from the Cardiology/Cardiac Arrhythmia clinic database to identify patients with non-valvular atrial fibrillation. Out of more than 4,000 encounters during 2014-2016, 100 patients on anticoagulation therapy with full records of follow-up for at least 12 months were randomly identified (35 on warfarin and 65 on DOACs). Patients’ CHA 2 DS 2 -VASc scores and clinical baseline clinical characteristics were recorded at the onset of anticoagulation treatment. Patients were followed for at least 12 months in order to assess the outcomes and reasons for changes in anticoagulation therapy. Results: The patients initially started on warfarin had a higher mean CHA 2 DS 2 -VASc score (4.54 vs. 3.69) and higher mean age (76.63 vs 72.73 years) than the composite DOACs group. At the time of initial prescription, the warfarin group tended to have a higher percentage of co-morbidities than patients on DOACs, such as previous MI - 17.14% vs 7.69%, previous CVA - 22.85% vs 15.38%, diabetes - 40.0% vs 26.15 %, CAD - 42.85% vs 29.23%, previous CABG - 22.85% vs 9.23%, and CHF - 22.85% vs 16.93 %. The 12 month follow-up showed that 22.9% of the patients on warfarin were switched to a DOAC versus only 6.2% of patients on DOACs being switched to warfarin. The most common reasons for patients on warfarin being switched to DOACs were individual patient preference or difficulties with INR monitoring. DOACs were most commonly changed to warfarin due to cost. Conclusions: Patients placed on warfarin may initially have more severe co-morbidities and higher CHA 2 DS 2 -VASc scores. The change in anticoagulation treatment from warfarin to DOACs may suggest greater patient or provider satisfaction with this new class of anticoagulants, but patient preference and cost are also important factors.