Patient Characteristics and Use of Oral Anticoagulation Therapy in New-Onset Atrial Fibrillation: Results From a Nationwide Registry Study in Finland

Background and Aims: The risk of ischemic stroke associated with atrial fibrillation (AF) can be reduced with oral anticoagulation therapy (OAC). We examined the patient characteristics and nationwide use of OACs in primary and secondary care AF patients. Methods: The Finnish AntiCoagulation in Atrial Fibrillation (FinACAF) -study is a nationwide study of AF patients that combines data from several Finnish health care registers. In this study all new-onset AF patients in Finland from January 2011 to December 2018 with laboratory data were analyzed. Comorbidities and CHA 2 DS 2 -VASc -score were recorded until date of AF diagnosis. First OAC therapies from diagnosis of AF to the end of study were analyzed. For warfarin users with sufficient laboratory data, time in therapeutic range (TTR) was calculated and patient quartiles by TTR were assigned. Results: Of the 130 533 (50.7 % male) new-onset AF patients studied, 96 051 (73.6%) used any OAC medication after AF diagnosis. The used OACs were warfarin (n= 56 857; 43.6%), apixaban (n=16 377; 12.5%) rivaroxaban (n=14 821; 11.4%), dabigatran (n=7 224; 5.5%), and edoxaban (n=723; 0.6%). The mean TTR values in warfarin TTR-quartiles were 32% (0-52%) in the 1 st quartile, 65% (56-72%) in the 2 nd quartile, 77% (72-83%) in the 3 rd quartile and 90% (83-100%) in the highest quartile. Among patients with standard dose of direct oral anticoagulants, the mean CHA 2 DS 2 VASc -score was 2.78 for dabigatran and 3.47 for apixaban. For patients with warfarin the mean CHA 2 DS 2- VASc -score was 3.50 in the highest quartile. The mean CHA 2 DS 2- VASc for patients without any OAC was 3.19. Conclusion: In unadjusted analyses patients with dabigatran had the lowest and patients with apixaban the highest mean CHA 2 DS 2- VASc score. In patients with warfarin, the highest TTR quartile had the lowest mean CHA 2 DS 2- VASc -score and mean TTR of 77%. Contrary to the guidelines, a remarkable number of patients with high CHA 2 DS 2- VASc score remained without any OAC treatment.