Initiation of anticoagulation in atrial fibrillation: which factors are associated with choice of anticoagulant?

Background: The use of non-vitamin K antagonist oral anticoagulants (NOACs) for stroke prophylaxis in atrial fibrillation (AF) is increasing rapidly. We compared characteristics of AF patients initiated on NOACs versus vitamin K antagonists (VKAs). Methods: Using Danish nationwide registry data, we identified AF patients initiating either a VKA or a NOAC from 22 August 2011 until 30 September 2016. We compared patient characteristics including age, gender, comorbidities, concomitant pharmacotherapy and CHA₂DS₂-VASc and HAS-BLED scores in patients initiated on a VKA, dabigatran, rivaroxaban or apixaban. Differences were examined using multivariable logistic regression models. Results: The study population comprised 51 981 AF patients of whom 19 989 (38.5%) were initiated on a VKA, 13 242 (25.5%) on dabigatran, 8475 (16.3%) on rivaroxaban and 10 275 (19.8%) on apixaban. Those patients initiated on apixaban had higher mean ± SD CHA₂DS₂-VASc scores than those initiated on a VKA (3.1 ± 1.6 vs. 2.9 ± 1.6). Those initiated on dabigatran had lower mean CHA₂DS₂-VASc scores (2.7 ± 1.6) than all other groups. Patients with a history of a prior stroke were significantly more likely to be initiated on a NOAC compared with a VKA [odds ratio (OR) 1.35, 95% confidence interval (CI) 1.28–1.43]. By contrast, patients with a history of myocardial infarction were less likely to be initiated on a NOAC compared with a VKA (OR 0.72, 95% CI 0.67–0.77). Conclusions: Atrial fibrillation patients who were initiated on apixaban had higher stroke risk scores than patients initiated on VKAs. Interestingly, opposite results were found for dabigatran.