Post-discharge pharmacotherapy in people with atrial fibrillation hospitalised for acute myocardial infarction: an Australian cohort study 2018-2022.

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 hospitalised for AMI.

Methods and results: We identified 1,330 people hospitalised 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 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. 44.6% of people dispensed both medicines continued P2Y12i for over 12 months; this was more common in people who received a revascularisation 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.