Effectiveness and safety of drugs used for stroke prevention in a cohort of non‐valvular atrial fibrillation patients from a primary care electronic database

Purpose The aim of this study was to assess effectiveness and safety of antithrombotics for stroke prevention in non‐valvular atrial fibrillation in real‐use conditions. Methods We used a population‐based retrospective cohort study. Information emerges from SIDIAP, a database containing anonymized information from electronic health records from 274 primary healthcare centres of the Catalan Health Institute, Catalonia (Spain), with a reference population of 5 835 000 people. Population includes all adults with a new diagnosis of non‐valvular atrial fibrillation registered in SIDIAP from 2007 to 2012. The main outcome of antithrombotics' effectiveness was stroke. The main outcomes of safety were cerebral and gastrointestinal haemorrhages. We also estimated all‐cause mortality. We used multivariable Cox proportional hazard models to examine association between antithrombotic treatment and main outcomes. Results We included 22 205 subjects with non‐valvular atrial fibrillation; 40.8% initiated on vitamin K antagonists (VKA), 33.4% on antiplatelets and 25.8% untreated. We found stroke‐risk reduction with VKA, hazard ratio (HR) 0.72 (95% confidence interval (CI), 0.58–0.91), also seen in patients with CHADS2 ≥ 2, HR 0.65 (95%CI, 0.49–0.86), and CHA2DS2‐VASc ≥ 2, HR 0.66 (95%CI, 0.52–0.84). We observed a higher risk of digestive bleeding with antiplatelets, HR 1.32 (95%CI, 1.01–1.73). Both VKA and antiplatelets were associated with reduction of all‐cause mortality risk; HR 0.55 (95%CI, 0.49–0.62) and HR 0.89 (95%CI, 0.80–0.97), respectively. Conclusions This study found a stroke‐risk reduction associated with VKA and an increased risk of gastrointestinal bleeding associated with platelet‐aggregation inhibitors in comparison with untreated patients. Both antithrombotic groups showed a reduction in all‐cause mortality.