BACKGROUND AND OBJECTIVES: Although electrical cardioversion (CV) is effective in restoring sinus rhythm (SR) in patients with atrial fibrillation (AF), AF frequently recurs in spite of antiarrhythmic medications. We investigated the predictors of failed CV and AF recurrence after successful CV. SUBJECTS AND METHODS: In 81 patients (M:F=63:18, 59.1+/-10.5 years old) with AF who underwent CV, clinical findings and pre-CV serologic markers were evaluated. RESULTS: During 13.1+/-10.6 months of follow-up, 8.6% (7/81) showed failed CV, 27.16% (22/81) showed early recurrence atrial fibrillation (ERAF; < or =2 weeks), 32.1% (26/81) had late recurrence atrial fibrillation (LRAF; >2 weeks), and 32.1% (26/81) remained in SR and had no recurrence (NR). Plasma levels of transforming growth factor beta (TGF)-beta were significantly higher in patients with failed CV than in those with successful CV (p=0.0260). Patients in whom AF recurred were older (60.4+/-9.0 years old vs. 55.3+/-12.5 years old, p=0.0220), and had lower plasma levels of stromal cell derived factor (SDF)-1alpha (p=0.0105). However, there were no significant differences in these parameters between ERAF patients and LRAF patients. CONCLUSION: Post-CV recurrence commonly occurs in patients aged >60 years and who have low plasma levels of SDF-1alpha. High plasma levels of TGF-beta predict failure of electrical CV.