| Background:In now opinion, the most of paroxysmal atrial fibrillation originate from ectopic focus. Most of the ectopic focus were observed in pulmonary veins(especially in superior pulmonary veins).Some study revealed atrial myocardiac extending into pulmonary veins formed myocardial sleeve. Spontaneous activity was recorded in pulmonary veins. Through analysing data we found that myocardial sleeve have the basis of being ectopic focus. It have anatomical and electrophysiological base. Pulmonary vein sleeves do not display arrhythmogenic activities under normal physiological conditions. It is said under normal physiological conditions myocardial sleeve is "concealed" ectopic focus, it isn't "active" ectopic foci. It needs certain condition to wake up. the "concealed" ectopic focus. Atrial fibrillation and/or atrial arrhythmia result in shortening the atrial refractory and/or atrial depolarization period, the phenomen is described as electrical remodeling. Electrical remodeling favors its own perpetuation. Whether electrical remodeling can wake up the "concealed" ectopic foci,is not clear. Our objective was: Under electro-stimuls and/or atrial fibrillation, which one was easily electrical remoded in pulmonary veins and atrial. After electrical remodeling, which one was easily conducted atrial fibrillation. Whether electro-remodeling is the certain condition that can wake up the "concealed" ectopic focus. Materials and methods:1.Studying model made 16 dogs were included. After general anesthesia ,usingrespirator to help the dogs respire(15ml/kg weight),then open the chest to disclosure the left, right atrial and pulmonary veins.2.Recording the refractory of left , right atrial, four pulmonary veins in sinus rhythm As the electrocardiogram was well in pulmonary veins and atrial by epicardial mapping. Record the refractory of left, right atrial, four pulmonary veins in sinus rhythm through S1S2.S1S1=(RR-100)ms, S1S2=(RR-150)ms, Input=1.5 X threhold, Interval=8s, S2/Si=l:8, Pace=-5ms.3. Atrial fibrillation/stimulation lh,recording the refractory of left ? right atrial, four pulmonary veins Using SiSi> 8182(818283) & burst to induce atrial fibrillation in atrial and pulmonary veins.In Ih, repeat that operation to keep atrial fibrillation. If the inducity can't realize, paced with maximal atrial capture rate for 1 hour. Then recorde the refractory of left, right atrial, four pulmonary veins and atrial fibrillation.4. Atrial fibrillation/stimulation lh,recording the refractory of left % right atrial,four pulmonary veins Repeating pace 3, then record the refractory of left -. right atrial, four pulmonary veins and atrial fibrillation.5. Atrial fibrillation cycle length(AFCL) During AF(spontaneous or induced sustained AF),local AFCL at each mapping site was measured.6. Epicardial mapping Using electrode made by self, map the atrial and pulmonary veins.Results:The experiment was completed in 16 dogs. The refractory of left ? right atrial, four pulmonary veins were recorded under sinus rhythm and after stimulation 1,. 2h.During atrial fibrillation, atrial fibrillation cycle length(AFCL) at each mapping site was measured. Under sinus rhythm, the difference was not significant as compared the refractory of left , right atrial, four pulmonary veins with one'sown(P >0.05).After stimulation 1 N 2h, the difference was significant as compared with the data of sinus rhythm (P <0.05).In stimulation 1 >2h, the difference was significant as compared with the refractory of left, right pulmonary veins (P <0.05).One and two hours the difference was not significant in left , right atrial and two inferior pulmonary veins (P >0.05).Cross compare, the difference was significant as comparedthe refractory of superior pulmonary veins with left , right atrial(P <0.05);Two hours later the difference was not significant as compared inferior pulmonary veins with left , right atrial(P >0.05).In sinus rhythm, inducibility of atrial fibrillation was no difference as compared with left atrial and left supe...
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