Purpose: This study evaluated the benefits of and possible contraindications to warfarin treatment in patients with atrial fibrillation (AF) prior to the introduction of new oral anticoagulants using health registry data from inpatient care, specialist ambulatory care, and primary care.
Methods: This is a cohort study including all patients in the region of Stockholm, Sweden (2.1 million inhabitants) with a diagnosis of non-valvular AF (n = 41 810) recorded during 2005-2009. The risks of suffering ischemic stroke, bleeding, or death with warfarin, aspirin, or no antithrombotic treatment during 2010 were related to CHA2DS2VASc scores, age, and complicating co-morbidities.
Results: One-year risks for ischemic stroke were 1.0-1.2 % with aspirin, 0-0.3 % with warfarin, and 0.1-0.2 % without treatment at CHA2DS2VASc scores 0-1. Among the aspirin-treated patients with CHA2DS2VASc scores ≥2, half had possible contraindications and high risks for ischemic stroke (5.2 %), bleeding (5.0 %), and death (19.3 %). The other half of the patients with no identified contraindications had a high risk for ischemic stroke (4.0 %) but a low bleeding risk (1.8 %) and a moderate mortality rate (8.4 %).
Conclusions: The present observations confirm earlier findings of undertreatment with warfarin and half of the high-risk patients treated with aspirin were obvious candidates for anticoagulant treatment. However, the other half of the patients had complicating co-morbidities, high bleeding risk, and poor prognosis. This and possible overtreatment of low-risk patients should be taken into account when considering more aggressive use of anticoagulant treatment.