The purpose of this study is to determine the frequency of atrial fibrillation in patients with transient ischemic attack (TIA). Patients suffering TIA will have their heart rhythm extensively monitored with 72-hour Holter-monitoring and an implantable loop-recorder. Furthermore, the patients will be examined with echocardiography, coronary calcium-score and biomarkers with the purpose to predict which subjects at risk for developing atrial fibrillation.