Atrial fibrillation is the most common cardiac arrhythmia. In atrial fibrillation, there is a risk that clots can form in the heart, especially in the left atrium. If these clots come loose, there is a risk of stroke. To prevent strokes, patients with atrial fibrillation and status post ICB can be treated with anticoagulants. This medication therapy prevents blood clots from forming in the heart, but can also cause bleeding. Another therapy option is the occlusion of the left atrium. After closure of the left atrium, only a short anticoagulation therapy is necessary until the occluder has healed. The aim of the study is to compare these two treatment approaches. In this study only already approved drugs and occlusion systems will be used.