Abstract
Warfarin is well studied in patients with non-valvular atrial fibrillation (AF). It has low complication rates for patients achieving individual Time in Therapeutic Range (iTTR) > 70%. The risk scores SAMe-TT2R2 and PROSPER are designed to predict future TTR, but are derived from a heterogeneous population with generally low iTTR. The aim of this study was to evaluate predictors for high and low iTTR in an AF population in Sweden, where there is a generally good anticoagulation control. A retrospective register study based on Swedish warfarin dosing system AuriculA, including 28,011 AF patients starting treatment during 1 January 2006 to 31 December 2011. Complications and risk factors were analysed and related to iTTR. Mean age was 73.7 (SD ± 9.5) years, with 42.0% women. Mean CHA2DS2-VASc score (SD) was 3.6 (± 1.7). For patients with iTTR < 60% there were over three times higher prevalence of excessive alcohol consumption than for patients with iTTR > 70% (3.7% vs. 1.1%). Previous stroke were more prevalent for patients with high than low iTTR (17.1% vs. 20.3%). Concomitant comorbidities were associated with increased risk of poor iTTR. In Swedish AF patients, excessive alcohol use is clearly associated with iTTR below 60%. Patients with previous stroke are more likely to get iTTR above 70%, unlike those with concomitant disorders who more often have poor anticoagulation control. The SAMe-TT2R2-score cannot be applied in Sweden.
Highlights
In Sweden, both direct oral anticoagulants (DOACs) and vitamin K antagonists are used as stroke preventives in atrial fibrillation (AF), and national guidelines equals those treatment options [1]
Swedish warfarin treatment quality is very high in terms of high time in therapeutic range (TTR) and low complication rates [2, 3]
Patients in the in Therapeutic Range (iTTR) < 60% group had more prevalent excessive alcohol use (3.7% vs. 1.1%) and less frequently previous stroke (17.1% vs. 20.3%) compared to patients with iTTR > 70%
Summary
In Sweden, both direct oral anticoagulants (DOACs) and vitamin K antagonists (e.g. warfarin) are used as stroke preventives in atrial fibrillation (AF), and national guidelines equals those treatment options [1]. Swedish warfarin treatment quality is very high in terms of high time in therapeutic range (TTR) and low complication rates [2, 3]. A previous study on Swedish patients with non-valvular AF started on warfarin as stroke prevention, showed generally low risk of complications, especially in patients achieving TTR over 70%, concluding warfarin to be still a valid alternative for stroke prevention [4]. For warfarin patients with less optimal TTR levels, DOACs could provide a more safe and effective treatment option. The risk-scores SAMe-TT2R2 and PROSPER can be used to predict the future TTR level of. These scores are deduced in a more heterogenous population with generally lower TTR-levels, and might not be valid in a high TTR setting
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