Objective:To investigate the changes of myocardial cell apoptosis in order to explore the association between the atrial reverse remodeling and the myocardial cell apoptosis after chronic atrial fibrillation(AF) conversion to sinus rhythm. Methods:Eighteen goats were randomly divided into three groups(each n = 6):(A)sinus rhythm(SR),(B)Chronic AF,(C)sinus rhythm after AF. Three groups of goats were all underwent open chest surgery to implant the pacemaker electrodes into the left appendages. Group B and C were given continuous and rapid pacing(400 ± 10 bpm) in order to build chronic AF model. Group A was killed after three months without pacing. Group B was killed at the same time. Group C was stopped pacing and converted into sinus rhythm by propafenone and/or direct current. After three months’ sinus rhythm,group C was killed. The atrial tissue was obstained from the left atrium,and was stained by EdUTP-in situ end-labeling and observed by flow cytometry. Results:The apoptotic ratio of the left atrial myocytes in the goats with chronic AF was significantly higher than that in the goats with sinus rhythm(P < 0.05). It was still higher in the goats with 3 months’ SR post-AF than that in the goats with sinus rhythm,but lower than those with chronic AF(P < 0.05). Conclusion:The changes of myocardial cell apoptosis before and after AF conversion suggests that myocardial cell apoptosis is associated with the atrial remodeling and the reverse remodeling.