BackgroundEndothelial damage/dysfunction may contribute to a prothrombotic state in patients with atrial fibrillation (AF) and the increased risk of thromboembolism and cardiovascular events. Raised plasma von Willebrand factor (vWf), an established marker of endothelial damage/dysfunction, has been associated with stroke and vascular events, at least in a clinical trial population. Soluble E-selectin (sE-sel) is another biomarker of endothelial activation/dysfunction, with more limited data on prognostic outcomes in AF. ObjectiveTo assess the relationship between the levels of vWf, sE-sel and clinical adverse outcomes (including stroke, MI and all-cause mortality) in a real-world' community cohort of patients with AF. MethodsWe studied 423 patients (mean age 72784years, 556% male) with nonvalvular AF, with a median follow-up of 19 (9-31) months. Plasma vWf and sE-sel levels were measured using enzyme-linked immunosorbent assay (ELISA). ResultsThere were 94 clinical adverse events (222%) observed during a median follow-up of 19months. Patients with clinical events had significantly higher vWf (P<0001) and sE-sel levels at baseline (P<0001) compared with those who were event free. Kaplan-Meir analyses demonstrated that more clinical adverse events occurred in the upper tertile of vWf [upper vs. lowest tertile, RR 38, 95% CI (263-557), P<0001; upper vs. middle tertile, RR 105, 95% CI (533-2060), P<0001]. Similarly, the highest tertile of sE-sel was associated with more adverse events [upper vs. lowest tertile, RR 37, 95% CI (251-531), P<0001; upper vs. middle tertile, RR 65, 95% CI (356-1191), P<0001]. ConclusionHigh plasma vWf and soluble E-selectin levels are associated with an increased risk of clinical adverse events (acute myocardial infarction, ischaemic stroke and all-cause mortality) in real-world' patients with AF. These soluble biomarkers may potentially aid clinical risk stratification in this common arrhythmia.