The Study Of Mechanism And Radiofrequency Ablation Of Focal Atrial Fibrillation In Dog

BACKGROUND:Focal atrial fibrillation(FAF) is initiated by the ectopic beats originating within or at the ostium of the pulmonary veins(PV).The structure of the PV is relation with FAF.Radiofrequency ablation(RF) of tissues in PV can eliminate FAF.But the feasibility of this technique is limited by the difficulty in mapping the focus and the incidence of PV narrowing.Circumferential ablation of PV ostium can cure atrial fibrillation.One or two bopoles electrodes showed earliest activation with later and sequential spread to the rest of the venous circumference,Ablation earliest activation site can cure some atrial fibrillation. We study the structure and morphology of PV,To investigate the relationship between structure and morphology and electrophysiology of PV and to provide more information relevant to RF.METHODS: Electrophysiology study was done in 20 structurally normal dogs.First 10 dogs were examined grossly. Histological sections were made from 35 PV. RF was done in latter 10 dogs.RESULTS:(l).The cardial sleeves in SPV were thicker than in IPV(P<0.05). For the SPV, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeve was composed mainly of circularly or spirally oriented bundles of myocytes.(2).Muscle covered the total PV perimeter and the bundles of cardial cell were disorganise in major of dog. electricty covered only various parts of the perimeter.The percent of perimetric electrical coverage was higher for both SPV than for IPV(P<0.05). (3).ERP of pulmonary vein was significantly shorter than that of left atrium.with theincreasing the frequency of pacing,ERP of pulmonary vein became shorter(P<0.05),but ERP of pulmonary vein was shorter than that of left atrium(P<0.05).Compared with IPV,the percent of atrial fibrillation induced by programmed pacing or Burst pacing was highter in SPV.the duration time of atrial fibrillation was not significantly different.(4).The conduction time from the pacing sites in SPY to left atrium was shorter than that in IPV.During premature stimulation.conductive characterize of atrial muscle was observed in the PV,the heterogeneity of conduction time was significantly bigger in SPY than that in IPV; (5).The earliest PVP was localized to any segment of the perimeter and the site of earliest PVP was not same when pacing was done at the roof,the bottom of PV or sinus rhythm.About 20% dogs, the sites of earliest PVP were same when pacing was done at difference sites;(6).RF deliveried at the earliest activated ostial segment either could elminated the total PVP or only elminated the PVP of the earliest activated site.the sequence of the other sites did chang or not chang.(7).RF total perimeter,the percent of lesion of every pulmonary vein/total lesions was higher in SPV than in IPV(P<0.05).After RKratio and time of induced atrial fibrillation were significantly lower than before RF. But ratio of induced atrial fibrillation was significantly higher in group of the earliest activated site RF, the duration time of atrial fibrillation was longer in group of the earliest activated site RF(P<0.05). (8).Our clinicial data found that 67.0% ectopic beats originated from SPV. the earliest activated site RF could cure some FAF patients,but effect was not better than electrical isolation at PV ostium.FAF could induce atrial enlargement, and electrical and anatomical remodeling.CONCLUSIONS:(l)The cardial sleeves are thicker in SPV than in IPV. For the SPV, the sleeves are thickest along the inferior walls and thinnest superiorly.The myocardial architecture in dog PV is highly variable.The complex arrangement and the spatial relationship between individual cells varies under electron-microscopicexamination and increase in fibrosis may produce greater non-uniform anisotropic properties. (2)ERP of pulmonary vein is shorter than that of left atrium, the percent of atrial fibrillation induced by programmed pacing or Burst pacing is highter in SPV.The short ERP is not only factor of atrial fibrillation.(3)The conduction time from the pacing sites in SPY...