BACKGROUND The purpose of this study was to determine whether high asymmetric dimethylarginine (ADMA) levels could predict early recurrence of atrial fibrillation (AF) after successful electrical cardioversion (CV). METHODS Seventy patients with persistent AF, but without known heart disease, who underwent elective electrical CV were enrolled. Blood samples for ADMA determination were drawn from all patients just before the CV. RESULTS The study population comprised 64 patients (men 73%, age 62.56 +/- 7.72 years, duration of AF 6.00 +/- 1.90 months) in whom sinus rhythm was restored. After 1-month follow-up, 30 (47%) patients had recurrence of AF. The median ADMA concentration was significantly higher in patients with AF recurrence (1.93 micromol/L vs 1.43 micromol/L; P = 0.001). AF recurrence was associated with higher pre-CV ADMA levels (odds ratio [OR]= 4.20; 95% confidence interval [CI], 1.44-12.22; P = 0.001). On multivariate analysis, ADMA was the only independent predictor of arrhythmia recurrence (OR = 4.19; 95%CI, 1.12-15.77; P = 0.034). CONCLUSIONS Our data suggest that high levels of ADMA are associated with an increased risk of AF recurrence within 1 month after electrical CV, supporting the hypothesis that ADMA might participate in the process of atrial remodeling.