The aim of this study is to evaluate benefits of electric cardioversion in the early and long-term postoperative period in patients after radiofrequency catheter isolation of pulmonary veins. Parameters of the left atrium will be evaluated by transthoracic echocardiography and electroanatomic mapping. Preservation of the sinus rhythm will be assessed by 24-hour electrocardiographic monitoring. The main question that is planned to be answered is: Does a reverse remodeling of the left atrium and/or a decrease in the progression of the fibrosis zone occur after performing electrical cardioversion (and before subsequent catheter ablation) in patients with persistent and long-standing persistent atrial fibrillation (AF)? Can performed electrical cardioversion serve as a predictor of AF freedom in this group of patients? Participants will undergo a follow-up examinations (echocardiography, ECG, 24-hour ECG monitoring) at the 3rd, 6th and 12th months after catheter ablation. Based on the results of these examinations, the recurrence rate of AF will be estimated. Two groups of patients will include both persistent and long-standing persistent AF. Experimental group will include patients who underwent electrical cardioversion before the intervention, and active comparator group will include those patients who did not undergo it. The experimental group will be subdivided into a persistent AF patients who were successfully cardioverted in sinus rhythm and persistent AF patients who failed to restore sinus rhythm during DC at the time of catheter ablation. Analysis and comparison of subgroups will be performed.