Post-discharge pharmacotherapy in people with atrial fibrillation hospitalized for acute myocardial infarction: an Australian cohort study 2018–22

Abstract Background Dual antiplatelet therapy with P2Y12 inhibitors (P2Y12i) and aspirin following acute myocardial infarction (AMI) prevents future ischaemic events. People with atrial fibrillation (AF) also require oral anticoagulants (OAC), increasing bleeding risk. Guidelines recommend post-discharge prescribing of direct OAC with clopidogrel and discontinuation of P2Y12i after 12 months, but little is known about use in clinical practice. Aim To describe post-discharge use of OACs and P2Y12i in people with AF and a history of OAC use hospitalized for AMI. Methods and results We identified 1330 people hospitalized for AMI with a diagnosis of AF and history of OAC use in New South Wales, Australia, July 2018–June 2020. We identified three aspects of post-discharge antithrombotic medicine use with possible safety implications: (1) not being dispensed OACs; (2) dispensing OAC and P2Y12i combinations associated with increased bleeding (involving warfarin, ticagrelor, or prasugrel); and (3) P2Y12i use longer than 12 months. After discharge, 74.3% of people were dispensed an OAC, 45.4% were dispensed a P2Y12i, and 35.8% were dispensed both. People with comorbid heart failure or cancer were less likely to receive OACs. Only 11.2% of people who dispensed both an OAC and P2Y12i received combinations associated with increased bleeding; this was more common among people with chronic kidney disease or prior warfarin or statin use. A total of 44.6% of people dispensed both medicines continued P2Y12i for over 12 months; this was more common in people who received a revascularization or lived in areas of social disadvantage. Conclusion We identified potential gaps in pharmacotherapy, including underuse of recommended therapies at discharge, use of combinations associated with increased bleeding, and P2Y12i use beyond 12 months. Prescribing vigilance across both hospital and community care is required.