Aim. To evaluate the effect of blood concentrations of biomarkers of inflammation and fibrosis, obesity parameters, and parameters characterizing cardiac remodeling on the risk of recurrent atrial fibrillation (AF) within 6 months after elective electrical cardioversion (ECV) in patients with metabolic syndrome (MS).Materials and methods. The study included patients with AF and MS (n=60) and with AF without MS (n=41), who underwent elective ECV. Prospective observation was carried out for 6 months.Results. Arrhythmia recurrence within 6 months after ECV in patients with AF in combination with MS is higher than without MS (34/60 and 9/41, p = 0.003). Among echocardiographic parameters, left atrial volume and volume index, and epicardial adipose tissue thickness (EAT) are associated with arrhythmia resumption in patients with MS and AF. Blood concentrations of galectin-3 (17.4 (12.8-19.6) and 13.3 (5.1-14.9), p=0.0001), connective tissue growth factor (CTGF) (163, 1 (134.1-232.2) and 156.7 (104.7 - 189.1), p=0.002), growth differentiation factor 15 (GDF-15) (2343.9 (1206.1-3254.2 ) and 986.1 (812.5-1775.5), p=0.0001) and interleukin-6 (IL-6) (3.8 (2.3-7.3) and 2.3 (1, 3-3.4), p=0001) in patients with MS with recurrent arrhythmia is higher than without arrhythmia. According to the ROC analysis of EAT, the concentration of galectin-3 and IL-6 in the blood was most predictive of relapse of AF in MS; threshold values of the predictors were established: EAT more than 6.1 mm, IL-6 more than 2.8 pg/ml, galectin-3 more than 15.9 ng/ml.Conclusion. In patients with AF combined with MS, the frequency of maintaining sinus rhythm after effective ECV for 6 months is lower than in patients without MS. Epicardial adipose tissue thickness, high concentrations of galectin-3 and IL-6 are associated with relapse of AF in patients with MS.