Objective       To detect the levels and the dynamic expression levels of several oxidative stress biomarkers in the serum and cardiac tissues during atrial remodeling in atrial fibrillation patients in order to investigate the underlying mechanism of atrial fibrillation development.       Methods       A total of 44 patients with rheumatic heart disease undergoing mitral valve replacement in our center from February to May 2014 were enrolled in the present study. The patients were divided into 2 groups according to their history and preoperative electrocardiography (ECG) reports

that is persistent atrial fibrillation group (AF

n=26) and sinus rhythm group (SR

n=18). Right auricle tissue samples were obtained during the operation

and then stained by Masson trichrome staining to examine the degree of fibrosis. The protein expression of NOX2 was measured by immunohistochemical assay and laser confocal microscopy. Oxidative stress was estimated by the amount of malondialdehyde (MDA)

superoxide dismutase (SOD)

reactive oxygen species (ROS)

advanced oxidative protein products (AOPP) in the right auricle

and by the serum levels of ROS and AOPP by enzyme-linked immunosorbent assay (ELISA).       Results       Significant differences were seen in the amount of MDA (15.41±1.69 vs 11.46±1.83  mol/mg)

SOD (13.32±1.25 vs 10.65±1.15  mol/mg)

ROS (18.53±3.47 vs 13.65±3.29  mol/mg)

AOPP (29.69±2.09 vs 21.94±1.94  mol/mg) between the AF group and SR group (P0.05). The serum ROS level was higher in the AF group than SR group (34.6±2.61 vs 17.8±1.03  mol/L)

but there was no obvious difference in that of AOPP (P0.05). Compared to the SR group

the AF group had markedly more collagenous fibers and stronger NOX2 protein expression in the right auricle.       Conclusion       Myocardial interstitial fibrosis is the main characteristics of atrial structural remodeling in atrial fibrillation

and oxidative stress is involved in the process of atrial fibrillation and structural remodeling.