This paper presents two patients with atrial fibrillation. The first patient is a young 46-year-old, working, active male, who has only hypertension and pharmacologically well-controlled hyperthyroidism. He was diagnosed with persistent atrial fibrillation lasting four days (EHRA III, CHA2DS2-VASc 1 point, HAS-BLED 0 point). After excluding embolic material based on the transesophageal echocardiography and implementation of non-vitamin K antagonist oral anticoagulant (NOAC), effective electrical cardioversion was performed. Due to poorly tolerated recurrences of atrial fibrillation (EHRA III) in the clinical observation, the patient has been classified for circumferential pulmonary vein isolation (PVI), which was performed after a routine transesophageal echocardiography. The patient continued anticoagulation with NOAC before and post procedure for 2 months. Another patient is a 78-year-old man, treated chronically, so far only because of hypertension. He was admitted to the cardiology department due to the cardiovascular decompensation and increased symptoms of heart failure for 3 weeks prior to hospitalization. During the hospitalization, the patient was diagnosed with persistent atrial fibrillation (EHRA II, CHA2DS2-VASc 4 points, HAS-BLED 3 points), moderate mitral and tricuspid valve regurgitation, chronic renal failure stage III, microcytic anemia, thrombocytopenia, iron deficiency, benign prostatic hypertrophy and osteoarthritis of the spine. Additional aggravating factors were newly diagnosed cognitive function decline and considerable fragility of the patient (4th degree according to the Canadian Study of Health and Aging Clinical Frailty Scale). After the improvement of the patient status, taking into account the limitations and contraindications to anticoagulation, NOAC was administered. Electrical cardioversion was planned during next hospitalization. 1. January C.T., Wann L.S., Alpert J.S. i wsp. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J. Am. Coll. Cardiol. 2014; 64: e1–e76. 2. Ezekowitz M.D., Cappato R., Klein A.L. i wsp. Rationale and design of the eXplore the efficacy and safety of once-daily oral riVaroxaban for the prEvention of caRdiovascular events in patients with nonvalvular aTrial fibrillation scheduled for cardioversion trial: a comparison of oral rivaroxaban once daily with dose-adjusted vitamin K antagonists in patients with nonvalvular atrial fibrillation undergoing elective cardioversion. Am. Heart J. 2014; 167: 646–652. 3. Moneta G.L., Edwards J.M., Chitwood R.W. i wsp. Correlation of North American Symptomatic Carotid Endarterectomy Trial (NASCET) angiographic definition of 70% to 99% internal carotid artery stenosis with duplex scanning. J. Vasc. Surg. 1993; 17: 152–157; dyskusja 7–9. 4. Flaker G.C., Pogue J., Yusuf S. i wsp. Cognitive function and anticoagulation control in patients with atrial fibrillation. Circ. Cardiovasc. Qual. Outcomes 2010; 3: 277–283. 5. Cacciatore F., Testa G., Langellotto A. i wsp. Role of ventricular rate response on dementia in cognitively impaired elderly subjects with atrial fibrillation: a 10-year study. Dement Geriatr. Cogn. Dis. 2012; 34: 143–148. Multidisciplinary approach to the choice of appropriate anticoagulant therapy, depending on the patient’s condition, the planned treatment for restoring sinus rhythm (cardioversion or PVI) with regard to comorbidities, should be a priority in everyday clinical practice.