Dabigatran and warfarin for secondary prevention of stroke in atrial fibrillation patients: A nationwide cohort study

BACKGROUND: This register-based observational study compares dabigatran to warfarin for secondary stroke prevention in atrial fibrillation patients among both 'new starters' on dabigatran and 'switchers' to dabigatran from warfarin.

METHODS: We identified in nationwide Danish registries 2,398 patients with atrial fibrillation and a history of stroke/TIA, making a first-time purchase of dabigatran 110mg bid (D110) and 150mg bid (D150). Patients were categorized as either vitamin K antagonist (VKA) naïve or experienced. Warfarin controls were identified using a complete (for VKA-naïve dabigatran patients) or matched sampling approach (for VKA-experienced dabigatran patients). Subjects were followed for an average of 12.6 months for stroke and transient ischemic attacks. Confounder-adjusted Cox regression models were used to compare event rates between treatments.

RESULTS: Among patients with a history of stroke/ transient ischemic attack and prior VKA experience, switching to dabigatran was associated with an increased stroke/ transient ischemic attack rate for both dabigatran doses compared to continuing on warfarin (D110 hazard ratio [HR] 1.99, 95% confidence interval [CI]: 1.42-2.78; D150 HR 2.34, 95% CI: 1.60-3.41). Among prior stroke/ transient ischemic attack patients who were new starters on dabigatran or warfarin, the rate of stroke/ transient ischemic attack for both doses of dabigatran was similar to or lower than warfarin (D110 HR 0.64, 95% CI: 0.50-0.80; D150 HR 0.92, 95% CI: 0.73-1.15).

CONCLUSIONS: In this register-based study, VKA-experienced patients with a history of stroke or transient ischemic attack who switched to dabigatran therapy had an increased rate of stroke compared to patients persisting with warfarin therapy.