Embolic Stroke of Undetermined Source

In 2014, the clinical construct of “embolic stroke of undetermined source” (ESUS) was introduced to identify patients with nonlacunar cryptogenic ischemic strokes in whom embolism was the likely stroke mechanism. It was hypothesized that anticoagulants might be more efficacious than antiplatelet agents for secondary stroke prevention in ESUS patients. At the time of the original publication, little information was available to estimate the frequency of ESUS, patient features, or prognosis. Interest in ESUS has been fueled, in part, by 3 ongoing randomized trials comparing nonvitamin K antagonist direct-acting oral anticoagulants with aspirin for secondary stroke prevention. Here, we report the results of a systematic review of published studies about ESUS and summarize additional recent information relevant to the ESUS construct.