Inclusion Criteria:  1. Patients aged 18 until 80 years with atrial fibrillation scheduled for left atrial ablation procedure (according to 20216 ESC Guidelines for the management of atrial fibrillation" and/or "2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation" 3. signed informed consent. 4. hemoglobin >10 g/dl in Messungen up to 8 weeks before inclusion.  Exclusion criteria:  Incompliance or contraindication of oral anticoagulation prior to ablation procedure.