Ischemic stroke risk estimation in patients without oral anticoagulation: an observational cohort study based on secondary data from Germany

BACKGROUND: Oral anticoagulants can cause potentially serious adverse events. Therefore, before prescribing oral anticoagulants for ischemic stroke prevention in patients with atrial fibrillation (AF), stroke risk assessment is required to identify patients that are likely to benefit from treatment. Current guidelines recommend the CHA(2)DS(2)-VASc-score for stroke risk assessment. The CHA(2)DS(2)-VASc-score is based on observational studies from different treatment settings and countries. As ischemic stroke risk differs by setting and region, the aim of this study is to estimate ischemic stroke risk (stratified by the CHA(2)DS(2)-VASc-score) for a broadly representative population with AF from southern Germany and compare them to results from previous studies. METHODS: The study design is a retrospective cohort study on patients with atrial fibrillation based on secondary data. We calculated CHA(2)DS(2)-VASc-score based on patient’s diagnoses recorded in the year 2014 and assessed outcomes in 2015–2016. The primary outcome is hospitalization for ischemic stroke. The secondary outome is hospitalizations for any thromboembolic event, including ischemic stroke, transient ischemic attack, peripheral arterial embolism, pulmonary embolism, and mesenterial embolism. We estimated the incidence rates of the outcomes (and corresponding 95%-confidence intervals) stratified by CHA(2)DS(2)-VASc-score. RESULTS: The primary endpoint occurred in 961 of the 30,299 patients constituting the study population, resulting in a total incidence rate of 2.2 per 100 person-years. The secondary endpoint occurred in 1553 patients (3.6 per 100 person-years). Ischemic stroke rates stratified by the CHA(2)DS(2)-VASc-score tended to be lower than those reported previously. Thromboembolic event rates stratified tended to be similar to those reported previously. CONCLUSIONS: Our results show that the performance of the CHA(2)DS(2)-VASc-score differs in the German population, as compared to internationally published data, with an overall trend towards lower risk of ischemic stroke in uncoagulated patients with AF. These results should not be practice changing, but they emphasize that stroke risk estimation in patients with atrial fibrillation should be further refined.