 INTRODUCTION Atrial fibrillation AF is the most common sustained cardiac arrhythmia with a prevalence of 1-2 in the general population; additionally, the incidence increases with age. 1 Among the elderly 75 years and older, its incidence is 12. 2 AF is associated with a five-fold risk of a cardioembolic event; approximately 20 of all strokes are due to AF. 3 The annual risk of stroke in AF patients is 5 -6 in AF patients without antithrombotic treatment. Moreover, a stroke due to AF is typically more severe, i.e. associated with worse neurological deficits. 4 Not only does the incidence of AF increase with age, the risk of strokes in AF patients also increases with age with age: in patients between 50-59 years, the risk of stroke is about 1.5, while in patients between 80 - 90, the risk increases to about 23. 5 The source of an embolic stroke is a thrombus, which forms in the left atrium LA due to insufficient mechanical contraction of LA. Most often thrombi arise in the left atrial appendage LAA; according to data from autopsies and findings from transesophageal echocardiography TEE in AF patients, approximately 90 of all left atrial thrombi arise in the LAA. 6 In addition to insufficient mechanical contraction of LA, the pro-coagulant status of patients also plays an important role in thrombus development. A patients risk profile is characterized according to the CHA2DS2-VASc score. Each letter presents one recognized risk factor C - congestive heart failure or left ventricular dysfunction, H - hypertension, A - age 75 years 2 points, D - diabetes, S - history of stroke 2 points, V - present vascular disease atherosclerosis, A - age 65 years, Sc- female sex. In the CHA2DS2-VASc scoring system, each risk factor is evaluated as either 1 or 2 points. The sum of all points presents the annual risk of a cardioembolic event, in percent. The prevention of strokes or other systemic cardioembolic events thrombus can embolize to peripheral artery of upper or lower extremity, artery supplying gastrointestinal tract, renal artery etc. involve treatment using anticoagulant drugs, which were, until recently, vitamin K antagonists only e.g. warfarin. These drugs block the effect of vitamin K in the liver, which in turn blocks the production of coagulant factors II, VII, IX, and X. As a result, the coagulation cascade is slowed. The efficacy of warfarin is estimated using International Normalized Ratio INR; the effective INR to prevent thrombus formation in AF patients is between 2.0 and 3.0. The amount of vitamin K in food varies, which can lead to variations in INR despite a stable warfarin dose. This represent one of the disadvantages of warfarin treatment. In large randomized trials, in which all patients are very carefully followed, only 65 of INR values were successfully maintain between 2.0 and 3.0. 7 In real clinical praxis, it was shown that only 50 of all INR values are within the desired range. 8 This can easily lead to both overtreatment and undertreatment of patients. Vitamin K antagonism is thought to be effective when 70 of INR values are maintained in the therapeutic range. 9 Another disadvantage of warfarin treatment involves dietary restrictions. 