Left ventricular thrombus is a recognised complication of acute myocardial infarction, associated with stroke, recurrent myocardial infarction and adverse cardiac remodelling. The prevention, treatment and resolution of thrombus is hampered by a lack of understanding of its initiation, propagation and dissolution. Advanced non-invasive imaging holds major promise in improving our understanding of the incidence and the natural history of left ventricular thrombus as well as providing potential biomarkers to assess disease activity and treatment efficacy. In this prospective observational study, the investigators will recruit patients with recent acute anterior myocardial infarction and screen them for evidence of left ventricular thrombus and subclinical stroke using hybrid positron emission tomography and magnetic resonance imaging (PET/MR). Each patient will undergo PET/MR of the heart and head 7±2 days after acute myocardial infarction. If left ventricular thrombus is present on baseline MR, patients will be started on anticoagulation at the discretion of the attending physician, who will determine the agent used (warfarin or direct oral anticoagulant) and the duration of therapy (3-6 months). Patients will then undergo repeat PET/MR at completion of anti-coagulant therapy and then again after another 3 months. Patients with increased 18F- GP1 activity but no overt thrombus on MR will undergo repeat PET/MR of the head and heart at 3 and 6 months to establish the natural history of this observation and its association with thromboembolism in the brain. They will not routinely receive anticoagulation given the exploratory nature of this study.