ObjectiveTo study the influence of preoperative atrial fibrillation (AF) on early outcome after mitral valve replacement (MVR). MethodsBetween January 1998 and December 2008, a total of 2,001 patients underwent MVR with or without tricuspid valve repair in our hospital, and 1,411 patients were included in the present study. The selected patients were divided into two groups according to preoperative rhythm status: AF group(n=772) and sinus rhythm (SR) group (n=639). The clinical data of AF group and SR group were compared using t test; the early mortality and incidences of complications of MVR were compared with χ2 test between the two groups. ResultsThe early mortality of MVR in AF group was significantly higher than that in the SR group (5.1% vs 2.8%, P=0.041). Incidence of cardiovascular complications was also significantly different between the two groups (AF group 9.5% vs SR group 4.9%, P<0.001). Specially, the incidences of low cardiac output syndrome and ventricular fibrillation were significantly higher in AF group than in SR group (4.0% vs 2.0%, P=0.044; 2.7% vs 1.1%, P=0.034). There were no significant differences in the incidences of prosthetic-valve complications, systemic complications and reoperation rates between the two groups. Multivariate analysis shows that preoperative AF is not an independent predictor for early death. ConclusionEarly mortality of MVR is higher in AF group. The onset of preoperative AF is a marker of aggravated mitral valve disease.