Atrial fibrillation and fluttering are the most common cardiac arrhythmias, which progressively affect the quality and duration of life, causing thromboembolic complications and an increase in heart failure. This article presents the result of studying and analyzing modern ideas about the epidemiology, etiology, pathogenesis, clinical manifestations, course options, complications and outcomes of atrial fibrillation and flutter with the establishment of urgent unresolved issues of this pathology.