The Study Of Atrial Fibrillation Development Mechanism In Canine

The theory of focal mechanism on atrial fibrillation was regarded as a breakthroughadvance in the field of atrial fibrillation.recently,electrophysiological specialist abroadfound that regular electrical activity existed in atrium(particularly in left atrium), andfrequency of electrical activity in pulmonary vein was faster than left atrium and rightatrium,suggested that high frequency rapid electrical activities in pulmonary vein orsome regions of atrium May be the source of atrial fibrillation.but,the precisemechanism was unkonwed.Electrical remodeling was defined as atrial effective refractory period shorten, thedisperse of ERP increased ,atrial effective refractory period misadaptation tofrequency and the change of atrial conduct speed after atrial fibrillation or continuousstimulation to atrium.Althoughrecent studies suggested atrial remodeling and structural remodeling play aimportant role in maintain of atrial fibrillation, the precise mechanism wasUnkonowed.Our study build canine persistant atrial fibrillation model through chronic rapid atrialpacing, epicardium mapping was performed in pulmonary veins , left trium and rightatrium in order to find fastest electrical activity region, effects of amiodaron onelectrophysiological characteristics in a canine atrial fibrillation model were alsostudied in order to discuss the develop and maintain mechanism of persistent atrial fibrillation.Calcium concentrations inside cell, the quantities of Cx43 and collagen fibre in pulmonary veins , left trium and right atrium were measured in order to discuss the mechanism of atrial electrical remodeling and structural remodeling. We hope the study provide experiment basis for treatment of atrial fibrillation.Part I The Bulid Method of Canine Atrial Fibrillation ModelObjective to investigate the feasibility of a canine atrial fibrillation(AF) model with chronic rapid atrial pacing(400bpm) and to discuss the best pacing time. Methods atrial fibrillation(AF) model with chronic rapid atrial pacing(400bpm) was performed in l0mongrel dogs.Programmed electrical stimulation and burst-pacing technique was used to induce Af before rapid atrial pacing and 2 6 10 weeks later respectively.Results The experiment was completed in 8 dogs.At baseline study .sustained AF which defined as irregular repetitive atrial responses lasting at least 15min failed to be induced by programmed electrical stimulation;but non-sustained AF was induced by burst pacing in two dogs ;after 2weeks pacing,sustained AF was induced by programmed electrical stimulation in 3 dogs, AF was induced by burst pacing in 6 dogs(sustained AF in 4dogs,non-sustained AF in 2 dogs; after 6 weeks pacing,AF occurred sponeously in 6 dogs (75%) (the duration of sustained AF was52 ± 6min) , sustained AF was induced by programmed electrical stimulation in 8 dogs(100%)( the duration of sustained AF was62±6min),the refractory period of sustained AF was 132 ±9ms; after 10 weeks pacing, AF occurred sponeously in 6 dogs (75%)( the duration of sustained AF was 68 ± 6min), and sustained AF was induced by programmed electrical stimulation in 8 dogs(100%)( the duration of sustained AF was 66 ± 5ms) after cardiacversion, the refractory period of sustained AF was 123± 1 lms;there was no significant difference in incidence of AF occurred sponeously, the duration of AF occurred sponeously, incidence of induced sustained Af, the durationof induced sustained AF and the refractory period of sustained AF between after 6 weeks pacing and after 10 weeks pacing(p<0.05,respectively). Conclusion the model is highly reproducible , the best pacing time May be 6 weeks.