Objective:To investigate the expression of serotonin transporter(5-HTT) in right atrial appendages(RAAs) of patients with valvular atrial fibrillation(AF) and study its clinical significance. Methods:RAAs were obtained from 28 patients undergoing heart valve replacement. Among them, 13 patients were in sinus rhythm(SR), 15 patients had AF. We compared the differential mRNA and protein expression of 5-HTT in the RAA tissues between the two groups by real-time quantitative PCR, Western blot and immunohistochemisty. Results:The mRNA expression of 5-HTT in the AF group was 2.2 times higher than that of the SR group(P﹤0.01).The result of Western blot showed that the 5-HTT protein expression in AF was 2.13 times higher than that in SR(P﹤0.05), which was confirmed by immunohistochemistry. Conclusion:These data suggested that the abnormal levels of 5-HTT in RAAs may be involved in the occurrence and maintenance of valvular AF.