Real-world evidence for non-valvular atrial fibrillation patients treated with oral anticoagulation in the Nordics (REATTAIN)

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with an increased risk of ischemic stroke. The risk of stroke is estimated to be on average 5% per year without preventive treatment. Non-valvular AF (NVAF) refers to cases without rheumatic mitral valve disease, prosthetic heart valve or valve repair and represents most cases of AF.

Treatment with oral anti-coagulants (OACs) decreases the risk of stroke but is associated with an increased risk of major bleeding. Vitamin K-antagonists (VKAs) are widely used OACs with efficient stroke prevention, however, the use is limited by a lifelong monitoring of the patient.  

Non-vitamin K oral anti-coagulants (NOACs) have been shown to be effective in the prevention of stroke and are associated with a lower rate of fatal bleeding compared to VKA and do not require monitoring. 

Most NVAF patients receive a standard dose of NOAC. In some cases (e.g. impaired renal function, high age, low body weight), the dose should be reduced.

The overall aim of this study is to evaluate the comparative safety and effectiveness of reduced doses of NOACs vs. VKA for stroke prevention in patients with NVAF. Further, the study aims to describe the use and outcomes associated with potential under- and overdosing of each respective NOAC. 

The study is a non-interventional, retrospective cohort study with a study period ranging from 1 January 2010 to 31 December 2018, or latest available date in the data. The baseline period is defined as the 12 months prior to and including the index date (the day of the first qualifying oral anticoagulant dispensing) and will be used to ensure naïve users of oral anticoagulants.

The study population is defined as patients with NVAF who initiate treatment with OACs (VKA or NOAC). The population will be sourced from national administrative registers in Sweden, Denmark, Finland and Norway.