Association between markers of oxidative stress in the myocardium of the left atrium and atrial fibrillation in patients with mitral valve diseases

Objective The pathogenesis of atrial fibrillation(AF) occurring in patients with cardiac valvular diseases,cardiomyopathy and coronary artery diseases remains unclear.40%～79% of patients with mitral valve diseases requiring surgical intervention were observed to have AF.However,the pathogenesis varies among mitral valve diseases.We try to investigate the characteristics of oxidative stress in the myocardium of the left atrium and the their associations with AF in different forms of mitral valve diseases.Methods Left atrial appendages were obtained from patients with mitral valve disease while they were undergoing mitral valve surgery [n=24;12 with mitral stenosis (MS),6 with AF and 6 in sinus rhythms(SR);12 with mitral regurgitation (MR),6 with AF and 6 in SR)].Control data were obtained from left appendages of 4 persons in normal SR who died of traffic accident.Immunohistochemical method was used for evaluating 3-nitrotyrosine(3-Nr),colorimetric method was used for detection myocardium creatine kinase (CK),MM isoenzyme of creatine kinase (MM-CK) and myosin ATPase,and the contents of MM-CK and MM-CK tyrosine nitration were determined with western blotting.Results The expression of 3-NT was increased throughout the atrial myocardium in the patients with mitral valve disease as compared with that in the controls (P＜0.05).The immunoreactivity of 3-NT was higher significantly in the patients with AF than those in SR (P＜0.05),and was higher significantly in patients with MS than those with MR (P＜0.05).Significantly decreased activities of CK and MM-CK were observed in the myocardium from patients with mitral valve diseases,as compared with that in the controls (P＜0.05).Correlation analysis demonstrated that an inverse correlation existed between CK activity and 3-NT expression in the atrial tissues(r=-0.382,P＜0.05).There was also an inverse correlation between MM-CK activity and extent of MM-CK tyrosine nitration (r=-0.446,P＜0.05).Conclusion Response to coridative stress was increased significantly in the myocardium of the left atrium in the patients with mitral valve disease,and the response was higher in the patients with MS than in the patients with MR.Qxidative stress relates not only to mitral valve disease,but also relates to the development and persistence of AF.The formation of 3-nitrotyrosine in CK and MM-CK may damage the activities of them. Key words: Mitral valve; Heart valve diseases; Atrial fibrillation; Myocardium; Creatine kinase; Stress; 3-nitrotyrosine