Atrial fibrillation (AF) is one of the most common arrhythmias encountered in clinical practice. It has been found that the presence of chronic heart failure increases the risk of AF by 5 times. Furthermore, with an increase in the severity of symptoms of heart failure, the incidence and severity of AF increases. To date, markers of AF progression are not clearly defined. In this regard, it is relevant and reasonable to identify such markers in patients with heart failure. The aim of this research was to study the prognostic value of the 6-minute walk test (6MWT), NT-proBNP level, and left ventricular diastolic dysfunction for AF progression in patients with chronic heart failure (CHF). The study involved 96 participants with stable Class II and III CHF (the NYHA Functional Classification), who were included in the regional registry of CHF patients in September-November 2014. The data obtained showed that in patients with CHF, an increase in the level of Nt-proBNP, impaired myocardial relaxation, and a decrease in 6MWT distance may serve as predictors of AF progression with the transition of arrhythmias to stable forms.