Thromboembolic, bleeding, and mortality risks among patients with nonvalvular atrial fibrillation treated with dual antiplatelet therapy versus oral anticoagulants: a population-based study

BACKGROUND: Dual antiplatelet therapy (DAPT) with aspirin plus clopidogrel is used for stroke prevention in patients with atrial fibrillation (AF) when patients refuse to use oral anticoagulants (OAC) in clinical practice. However, there are limited clinical data comparing these treatments.

OBJECTIVE: To compare the clinical outcomes between DAPT and OAC in patients with AF.

METHODS: Cohort study using a population-wide database of the Hong Kong Hospital Authority. New patients with AF during 2010-2014 and prescribed DAPT or OAC (warfarin or dabigatran) were followed until July 31, 2016. Outcomes were thromboembolism, bleeding, and death. Propensity score (PS) matching at 1:2 ratio was used to select DAPT users with similar characteristics to OAC users, analyzed using Poisson regression.

RESULTS: Among 51,946 new patients with AF, 8,520 users of OAC and DAPT were identified. The likelihood of receiving DAPT over OAC increased with older age and previous intracranial hemorrhage. Among DAPT users, the incidences of thromboembolism, death, and bleeding per 100 patient-years were 15.8, 17.6, and 5.1 respectively. When compared to DAPT users, PS-matched analysis indicated a lower incidence of thromboembolism and/or death among OAC users (incidence rate ratio [IRR]=0.32, 95% confidence interval [CI]=0.19-0.55 for dabigatran and IRR=0.58, 95%CI=0.36-0.95 for warfarin), with no significant differences in bleeding events.

CONCLUSIONS: DAPT users were at markedly increased risk of thromboembolism and death compared to OAC users. These findings indicate the need for improved stroke risk reduction strategies among patients taking DAPT and the opportunities of using OAC in high risk groups to prevent more events.