Model Of Thoracotomy Goat Atrial Fibrillation And Atrial Fibrillation Sinus Rhythm After School Reconstruction Reversed

PartⅠChronic Rapid Atrial Pacing at left atrial appendageby thoracotomy a New Model of Sustained Atrial FibrillationObjective To create a new way of developing sustained atrialfibrillation (AF) by means of suturing the rapid-pacing electrode to thegoat's left atrial appendage in an open chest way. Method 18 goats weredivided into sham group (6 goats) and AF group (12 goats) randomly.The left lateral thoracotomy was performed at the fifth intercostal space,and the heart was exposed and suspended. A pacing electrode was thensutured to the left atrial appendage surface. In AF group the pacemakerwas connected to the electrode while the sham group did not. After oneweek of support treatment, the left atrial appendage was continuouslypaced at 400 beats per minute for 12 weeks. Electrocardiogram (ECG)was used to analyze the heart rhythm and detect AF when it occurred.Atrial Effective refractory period (AERP) was measured by programmedelectrical stimulation (PES). Sustained AF was defined as AF>15minutes.Structural changes were investigated by light and electron microscopy.Result One goats of the AF group died after surgery. After 12 weeks ofcontinuous atrial pacing, AF occurred spontaneously in 2 goats (18.18%).ECG showed typical changes of AF. In AF group, sustained AF wasinduced by PES in 8 goats (72.73%) and nonsustained AF was induced in3 goats(27.27%). Left AERP was significantly shortened after pacing. In AF group, Light microscopy showed the myocardial cells disarray.Electron microscopy of atrial tissue demonstrated ultrastructural changesthat were characterized by an increase in mitochondrial size and loss ofdefinition of Z bands. Conclusion Sustained AF was readily induciblein most goats (72.73%) after rapid atrial pacing. This animal model was anew way of developing sustained AF. PartⅡA Study of Reversal Structural Remodeling AfterPersistent Atrial Fibrillation in the GoatObjective To examine the reversibility of the changes in structuralremodeling in the goat with atrial fibrillation (AF). Method 18 goatswere divided into 3 groups(1)sham group with sinus rhythm(SR). (2) AFgroup. (3)sinus rhythm after AF(post-AF). Two-dimensionalechocardiography was performed to assess the changes of left atrial size.Ultrastructural changes of the left atrial tissue samples were studied byelectron microscopy. Atrial fibrosis was quantified by Masson staining.The mRNA level of MMP-2 was measured by semi-quantitative reversetranscription-polymerase chain reaction(RT-PCR). Result In AF group,left atrial diamension increased accompaning by marked fibrosis andmyolysis. In post-AF group, the enlarged atrial diamension showed atendency to decrease. Ultrastructural abnormalities were reversed 3months after AF reversion. The fibrosis observed by staining remainedhigher in post-AF, although to a lesser extent. The mRNA level ofMMP-2, which increased significantly in the AF group were partiallyrestored when AF were converted (0.40±0.12 vs 0.70±0.16 vs 0.52±0.10,P＜0.05, respectively). Conclusion Changs of structural remodeling 3months after AF can not be fully reversed and is a slow process.