Resolution of Left Atrial-Appendage Thrombus - Effects of Dabigatran in Patients With AF

Inclusion Criteria: * Patients with documented non-valvular AF or atrial flutter (12-lead ECG) * Newly diagnosed or confirmed LAA thrombus in TEE (time of detection ≤ 28 days) * Patients 18 years old * CHA2DS2-VASc Score 1 * CrCL 30 mL/min (Cockcroft-Gault) * Women with childbearing potential have to practice a medically accepted contraception * Ability of patient to understand the character and the individual consequences of the clinical trial * Signed and dated informed consent before start of any specific trial procedures Exclusion Criteria: * Patients \> 80 years * Low body weight (\< 50 kg) * Previous failure of LAA thrombus resolution with a VKA or factor Xa antagonist * Occurrence of LAA thrombus under long-term treatment (\> 3 months) with vitamin K antagonists with an exception in the case of continued INR out of the target range * Contraindications for oral anticoagulation therapy (see current Fachinformation for Pradaxa® (150 mg) and Marcumar® (3 mg)) * History of heart valve disorder (i.e., prosthetic valve or hemodynamically relevant valve disease) * Valvular heart disease requiring intervention (including mechanical valves) * Acute myocardial infarction or MI within the last 26 weeks * Acute coronary syndrome (e.g. instable angina pectoris, STEMI, NSTEMI) * Chronic Heart Failure (\> NYHA IIIa) * Previous haemorrhagic stroke * TIA within the last 90 days * Clinical relevant bleeding within the last 26 weeks * Acute and subacute bacterial endocarditis * Recurrent pulmonary embolism * Esophagitis, gastritis and gastroesophageal reflux * Thrombocytopenia or functional platelet defects * Congenital or acquired coagulation or haemorrhagic disorders * Liver diseases (liver enzymes \>2 ULN) * Renal insufficiency (CrCL below 30 mL/min) * Pre-treatment with Dabigatran in doses higher than 110 mg bid * Concomitant treatment with rivaroxaban, apixaban, and in case of approval during the course of the trial, also edoxaban * Concomitant treatment with irreversible cyclooxygenase inhibitors (e.g. ASA) at doses \> 100 mg/d. * Concomitant treatment with high doses of Adenosine diphosphate (ADP) receptor inhibitors (e.g. clopidogrel) at doses \> 75 mg/d * Combined treatment with Adenosine diphosphate (ADP) receptor inhibitors (e.g. clopidogrel) and irreversible cyclooxygenase inhibitors (e.g. ASA) in any dose combination * Planned treatment with long-term oral anticoagulants for alternative indications * Concomitant treatment with P-glycoprotein (P-gp) inhibitors, i.e. verapamil. * Need for continued treatment with ticlopidine, ticagrelor, prasugrel, systemic ketoconazole, itraconazole, posaconazole, cyclosporine, tacrolimus, dronedarone, rifampicin, phenytoin, carbamazepine, St. John's Wort or any cytotoxic/myelosuppressive therapy * Concomitant treatment with medication not permitted * Planned surgical intervention during expected study participation or previous surgical interventions within the last 30 days * Other significant risk factors for bleeding complications (e.g. malignancy) * Pregnancy and lactation. * History of hypersensitivity to the investigational medicinal product or to any drug with similar chemical structure or to any excipient present in the pharmaceutical form of the investigational medicinal product. * Participation in other clinical trials during the present clinical trial or within the last 90 days. * Medical or psychological condition that would not permit completion of the trial or signing of informed consent.