Ntaios G, Perlepe K, Lambrou D, et al. - Researchers used a pooled data set derived from 3 prospective stroke registries, to evaluate the prevalence as well as the degree of overlap of potential embolic sources (PES) in patients with embolic stroke of undetermined source (ESUS). Based on the PES that was/were found, the patients were classified in ≥ 1 groups. Atrial cardiopathy, atrial fibrillation diagnosed during follow-up, arterial disease, left ventricular disease, cardiac valvular disease, patent foramen ovale, and cancer were the various categories of PES, which were defined by the experts. Left ventricular disease, arterial disease, and atrial cardiopathy were identified as 3 most prevalent PES in 800 patients with ESUS (43.1% women; median age, 67.0 years). The atrial fibrillation group vs other PES had a higher risk of stroke recurrence in multivariate analysis, however, the risk was not statistically different between patients with 0 to 1, 2, or ≥ 3 PES. In patients with ESUS, a major overlap of PES was evident. This could likely offer an explanation for the negative findings of the recent large randomized controlled trials of secondary prevention in patients with ESUS, and provide a rationale for a randomized controlled trial of combination of anticoagulation and aspirin for the prevention of stroke recurrence in patients with ESUS.