Histopathological characteristics and oxidative injury secondary to atrial fibrillation in the left atrial appendages of patients with different forms of mitral valve disease.

BACKGROUND: The prevalence of atrial fibrillation (AF) and the frequency cardioversion of AF postoperatively are different in different forms of mitral valve disease. We hypothesized that these differences would relate to different extent of histopathological characteristics and oxidative injury in different forms of mitral valve diseases.

METHODS: Left atrial appendages were obtained from 24 patients of mitral valve disease with or without AF undergoing mitral valve surgery. Control data were obtained from left appendages of 4 persons in normal sinus rhythm (SR) died of traffic accident. Histopathology, immunohistochemistry, Western blotting and enzyme kinetics examination were performed to assess the extent of histopathological characteristics and oxidative injury.

RESULTS: The average cross-sectional diameter of atrial myocyte of mitral stenosis (MS)+AF, MS+SR, mitral regurgitation (MR)+AF, MR+SR and control was 25.62±7.56 μm, 20.20±9.34 μm, 21.69±7.00 μm, 13.93±4.32 μm and 9.81±2.34 μm, respectively. Significantly statistical difference was found between each group (P<.05). Increased degree of atrial interstitial fibrosis was seen both in MS and MR with AF patients compared to other groups (P<.05), and the extent of fibrosis was more remarkable in MR patients compared to MS patients (P<.05). The extent of 3-nitrotyrosine (3-NT) immunoreactivity significantly increased in the patients with MS and AF compared to those of MR and AF (P<.05), and the immunoprevalence of 3-NT was significantly increased in patients of MS and SR compared to those of MR and SR (P<.05). Correlation analysis demonstrated a negative correlation between creatine kinase (CK) activity and extent of 3-NT immunoreactivity in atrial tissues (r=-0.382, P<.05). Significant decreases in CK activity were observed in myocardium from all patients of mitral valve disease with or without AF compared to controls (P<.05). Western blotting demonstrating an increased prevalence of 3-NT formation in CK-MM was detected compared to control group (P<.05). Correlation analysis demonstrated a negative correlation between CK-MM activity and extent of CK-MM tyrosine nitration (r=-0.446, P<.05).

CONCLUSIONS: In different forms of mitral valve disease with different cardiac rhythm, the extent of histopathological characteristics and oxidative injury are different. Histopathological characteristics and oxidative injury not only relate to mitral valve disease but also relate to the development and sustain of AF.