Prevalence of Guideline Discordant Aspirin use and Associated Adverse Events in Patients on Warfarin for Mechanical Valve Replacement.

BACKGROUND: For patients on warfarin for mechanical heart valve replacement, the 2020 American College of Cardiology and American Heart Association Guidelines recommend only adding aspirin in patients with a specific indication for antiplatelet therapy. This contrasts prior guidelines which recommended concomitant aspirin therapy. We sought to assess the prevalence of guideline discordant aspirin use among patients on warfarin for mechanical heart valve replacement and to compare adverse event rates among patients with and without concomitant aspirin.

METHODS: Patients on warfarin for mechanical heart valve replacement were identified from the Michigan Anticoagulation Quality Improvement Initiative (MAQI2 ) registry. Patients with myocardial infarction, percutaneous coronary intervention, or coronary artery bypass within the past 12 months were excluded. Patients were divided into two groups based on aspirin use. Patient characteristics and bleeding and thromboembolic outcomes were compared.

RESULTS: Four hundred forty-four patients met inclusion criteria, with 341 (76.8%) on concomitant aspirin. The aspirin group was older (50.6 vs 46.3 years, p=0.028) and had more hypertension (57.8% vs 46.6%, p=0.046) but other patient characteristics were similar. The aspirin group had a higher rate of bleeding events (28.3 vs 13.3 per 100 patient-years, p<0.001) and bleed-related emergency department visits (11.8 vs 2.9 per 100 patient-years, p=0.001) compared to the non-aspirin group. There was no observed difference in rates of ischemic stroke (0.56 vs 0.48 per 100 patient-years, p=0.89).

CONCLUSION: A significant proportion of patients on warfarin for mechanical heart valve replacement are on guideline discordant aspirin. Aspirin deprescribing in select patients may safely reduce bleeding events.