Efficacy and Safety Evaluation of Refralon®, Concentrate for Solution for Intravenous Injection in Patients With Paroxysmal and Persistent Atrial Fibrillation and Flutter

Inclusion Criteria: * Diagnosis: paroxysmal or persistent atrial fibrillation or flutter; * A chemical cardioversion procedure performed with Refralon® in a hospital setting. Exclusion Criteria: * Congenital or acquired QT interval prolongation in the electrocardiogram (ECG) in 12 standard leads for more than 440 ms at the time of cardioversion; * Bradysystolic atrial fibrillation or flutter (mean heart rate \< 50 bpm or pauses \> 3 sec, registered on the ECG or identified by the results of 24-hour Holter ECG monitoring, except for the cases of its correction by a cardiac pacemaker at the time of cardioversion; * Sick sinus syndrome (sinus bradycardia, sinoatrial blockade), previously registered as associated with sinus rhythm, except for the cases of its correction with a cardiac pacemaker at the time of cardioversion; * Degree II - III atrioventricular blockade, two- and three-beam blockade with no cardiac pacemaker at the time of cardioversion; * Acute myocardial infarction period at the time of cardioversion; * Acute period after coronary artery bypass grafting (CABG) or other cardiac surgery (at least 7 days after CABG at the time of cardioversion); * Decompensated or severe chronic heart failure (III-IV functional class according to New York Heart Association (NYHA) classification) at the time of cardioversion; * Uncontrolled bronchial asthma, severe respiratory failure at the time of cardioversion; * Pregnancy and breastfeeding at the time of cardioversion; * Administration of Class IA antiarrhythmic drugs (quinidine, hydroquinidine, disopyramide, procainamide) at the time of cardioversion; * Class III antiarrhythmic drugs administration at the time of cardioversion; * Cardiac glycosides administration at the time of cardioversion; * Administration of QT-prolonging drugs at the time of cardioversion; * Heart rate \< 50 bpm, pauses \> 3 seconds on the ECG or Holter ECG monitoring (HM-ECG) during wakefulness at the time of cardioversion; * Hyperthyroidism or decompensated hypothyroidism (thyroid stimulating hormone (TSH) \< lower limit of normal or \> 2 upper limits of normal) at the time of cardioversion; * Uncorrectable electrolyte disorders (potassium level less than 3.5 mmol/L) at the time of cardioversion; * Identified contraindications to the sinus rhythm restoration at the time of cardioversion; * Blood clots in the heart cavities or spontaneous grade III-IV echo contrast at the time of cardioversion according to transesophageal echocardiography; * The need for electrical cardioversion due to the patient's hemodynamic instability at the time of cardioversion.