Background: Longstading AF(atrial fibrillation) causes atrial dilatation and depressed atrial conduction with increased P-wave duration. We hypothesized that atrial mechanical conduction time in addition to electrical conduction time-electromechanical conduction time(EMT) can reveal delayed atrial conduction in AF and may predict long term maintenance of sinus rhythm(SR) in patients with chronic AF after electrical cardioversion(CV). Methods: Thirty consecutive patients(60 짹11 years) with chronic AF(duration> 6 mo), who had electrical CV were prospectively enrolled. The 2-dimensional Doppler echocardiography was performed before CV and at discharge. The maintenance of SR was determined in surface ECG at 6 months. EMT was defined as the time interval from the onset of the P wave on ECG to the peak late diastolic velocity at the septal and lateral mitral annulus(EMT-S and EMT-L), using pulsed wave Doppler tissue imaging in the 4-chamber view. The mean EMT was calculated as the mean of EMT-S and EMT-L. Results: Twenty patients showed sinus conversion at dischrge after CV and 9 patients of them(45%) maintained SR at 6 months. LVEF, late diastolic velocity, P-wave duration and AF duration were not different between patients with maintaining SR and with recurring AF, but LA volume(48.8짹9.8 vs. 37.0짹10.0,p=0.02), EMT-S(142.4짹24.6 vs. 110.1짹20.2,p=0.005), EMT-L(152.1짹24.0 vs. 118.7짹15.8,p=0.002) and mean EMT(147.3짹23.0 vs. 114.4짹17.6,p=0.003) were significantly larger in patients with recurring AF and related to the maintenance of SR (p<0.05 in all). Multiple logistic regression analysis showed that EMT-L was most powerful predictor for the maintenance of SR at 6 months(p=0.002) and the sensitivity and specificity of EMT-L with cutoff value of ���140ms were 81.8% and 100%, respectively. Conclusion: This study showed that electrically cardioverted AF patients with recurring after CV at 6 months had significantly delayed atrial EMT, which suggests that enlarged left atrium with more remodeling may have more depressed electromechanical conduction that is susceptible to recurring AF soon. Therefore, the atrial EMT can be used as a predictor for long term maintenance of SR in patients with chronic AF after CV.