The Advancing knowledge in ischemic Stroke PatiEnts on oRal Anticoagulants (ASPERA) study aims to investigate characteristics of ischemic stroke cases occurring in patients on oral anticoagulation for atrial fibrillation (AF) or other cardioembolic arrhythmias and to characterize short and long-term outcomes associated with different secondary prevention strategies to prevent stroke recurrences. The ASPERA study is a multicenter, observational, both retrospective and prospective real-world study involving acute ischemic stroke patients occurring on oral anticoagulation. The study will encompass a retrospective (ASPERA-R) and prospective (ASPERA-P) data collection. Patient will be recruited consecutively at different emergency services and stroke units worldwide. University of L'Aquila (UnivAQ) will be in charge of study coordination, data analysis and management. The duration of ASPERA-R will be of 5-year from the study initiation of the study. Participating centers will be given a 6-month timeframe to enter retrospective data, commencing from the date of study approval. ASPERA-P duration will be of 2 years of enrollment from the study approval and follow-up of 5 years. (study conclusion after 7 years of approval). Inclusion criteria will be: 1.Confirmed diagnosis of ischemic stroke. 2. Availability of at least one neuroimaging exam positive for ischemic lesion(s) consistent with patient symptoms. 3. Ongoing oral anticoagulation at the time of the index ischemic stroke. 4. Prior diagnosis of atrial fibrillation or other cardioembolic arrhythmias. 5. Written informed consent provided by the patient himself or by proxy. Patients with Symptoms not indicative of acute stroke, ongoing intravenous or subcutaneous anticoagulation at the time of stroke will be excluded. ASPERA-R: characterization of demographic, clinical and neuroimaging features of ischemic stroke cases occurring on oral anticoagulants. The primary outcome will be: ASPERA-R : characterization of demographic, clinical and neuroimaging features of ischemic stroke cases occurring on oral anticoagulants. ASPERA-P: risk of ischemic stroke recurrence of ischemic stroke cases occurring on oral anticoagulants across different secondary preventive strategies (i.e., maintaining the same type of oral anticoagulation versus switching to a different secondary prevention strategy) at 90 days, 1 and 5 years after the index stroke. Additionally, the study will aim to investigate the risk of safety events (hemorrhagic transformation, intracranial hemorrhage, other major bleeding events, any bleeding events, death due to any cause), risk of other major ischemic events (transient ischemic attack, myocardial infarction, death due to vascular causes) at each follow-up and to identify demographic, clinical and neuroimaging features of ischemic stroke recurrences.