Patients with atrial fibrillation undergoing percutaneous coronary intervention with stent implantation require treatment with different antithrombotic drugs. Oral anticoagulants are prescribed to reduce the risk of stroke associated with atrial fibrillation. Antiplatelet substances are prescribed after stent implantation to reduce the risk of adverse cardiac events such as myocardial infarction or stent thrombosis. Treatment with antithrombotic medications can cause bleeding complications, particularly when these substances are combined. The currently recommended standard strategy consists of treatment with 3 antithrombotic medications for at least 1 week up to one month, followed by treatment with two of these medications for up to 6-12 months after stent implantation. Thereafter, patients usually receive long-term treatment with only one drug, an anticoagulant. In the monotherapy group of this study, the investigators will investigate a strategy where only one antithrombotic drug will be used at a time. During the first month after stent implantation, the investigators will prescribe an antiplatelet medication, followed by an oral anticoagulant as monotherapy. This strategy might be associated with fewer bleeding complications, while protecting adequately against thrombotic events. In this study the investigators would like to investigate whether treatment with a single antithrombotic drug (monotherapy strategy) is associated with benefits compared to the currently recommended combination therapy of antithrombotic medications (standard-of-care strategy).