SELP and atrial fibrillation: We have recently reported that both total GPVI (monomeric and dimeric GPVI) and GPVI-dimer are overexpressed on the platelet surface in ischemic stroke patients at admission and at day-90 post-stroke.14Our primary objective with theGRAFITEstudy was to determine whether patients with AF who have not had a stroke also express more GPVI on their platelet surface and have more active circulating platelets, as measured by surface exposure of platelet P-selectin, compared with hospitalized patients with a similar age and vascular risk-factor profile who do not have AF (noAF).