The Tasmanian Atrial Fibrillation Study: Transition to Direct Oral Anticoagulants, 2011-2015

Introduction: Contemporary Australian data regarding antithrombotic prescribing patterns following approval of direct oral anticoagulants (DOACs) in patients with atrial fibrillation (AF) are limited.

Aims: We aimed to assess antithrombotic prescribing patterns in AF before, during and after the introduction of DOACs.

Methods: Using digital medical records, this retrospective cohort included all patients with AF as a primary or secondary diagnosis who were admitted to the Royal Hobart Hospital, Tasmania, Australia, between January 2011 and July 2015.

Results: Antithrombotic agents were prescribed for 2078 of 2261 (91.9%) patients with AF without documented contraindication to therapy. Warfarin or a DOAC were prescribed for 920 (40.7%) and 383 (16.9%) patients, respectively; 745 (33.0%) patients received antiplatelet therapy. A higher proportion of patients was prescribed OACs following Government subsidisation of DOACs in Quarter 3 (Q3) 2013 than OAC prescribing in the preceding quarters, (54.4% in Q3, 2013 to 68.1% in Q2, 2015, p < 0.001), with the prescribing of warfarin and antiplatelet agents declining (38.1% to 22.1% and 45.6% to 31.9%, respectively, p <0.001). The proportion of patients receiving a DOAC steadily increased from 3.9% among OAC users in Q3, 2011 to 67.6% in Q2, 2015 (p< 0.001). In a sub-set of patients with newly diagnosed AF, patients commenced on DOACs were younger (70.4 vs. 73.8 years, p = 0.04) and had lower stroke and bleeding risk scores (CHA2DS2-VASc 2.8 vs. 3.3, p = 0.03, HAS-BLED 2.1 vs. 2.3, p = 0.04) than patients newly prescribed warfarin.

Discussion: DOACs rapidly became the drugs of choice for stroke prevention in NVAF and higher OAC prescribing rates were observed later in our study period. This corresponded with the commencement of Government subsidy of the new agents in August 2013. Nonetheless, antiplatelet agents accounted for a quarter to a third of all antithrombotic prescribing after DOACs became widely available highlighting the need for further improvement.