Lay summary
Atrial fibrillation is a common irregularity of the heart rhythm which increases the risk of stroke. Treatment with blood thinning medications reduces this risk, but many patients are not prescribed blood thinners because of concerns about bleeding, or because the stroke risk is thought to be low. This research will determine whether measuring two blood markers released by the heart, B-type natriuretic peptide and troponin, is useful for general practitioners to more reliably identify which patients with atrial fibrillation are most likely to benefit from blood thinners and other heart treatments.