| Background and aimAtrial fibrillation (AF) is one of the most common andcomplicated arrhythmia.Although AF cann't cause death directly, itincreases the disablity and mortallity.The final aim of AF therapy is to ablate AF and restore sinus rhythm.When Cox put up the concept of maze procedure,more and more AF patient is cured.Maze procedure has a high short-term success rate,80-90 percent patients restore sinus rhythm and atrium contractile function.But the maze procedure costs much time and causes great trauma , it also bring many post-operative complications .As thing stands today, wecann't accept maze procedure as the common non-pharmaceutic therapy.In 1994,Smartz reports that catheter ablation of the "mazeprocedure" .It is the biginning of clinical catheter ablation.Thisendocardial catheter ablation can effectively treat AF.However ,to the limitation of fluorescopic view, it istechnically difficult to ditermine the ablation site,and to position and orient the catheter tip,which in turn creates difficulty in confirming continuity of the ablation line.These factors lead to time-consuming procedures,which then frequently induce thromboembolic complications.And the epicardial linear ablation proved to be effective in AF therapy.Epicardial ablation under direct vision may be advantageous for creating continuous linear ablation and preventing thromboembolic events. It also save much time.On this basis,we establish the acute AF animal model in canine induced by Ach and atrial burst-pacing to learn the the feasiblity of epicardial linear ablation guided by video-assisted thoracoscopy system(VATS) .On the purpose of minimizing trauma,we tries to find a easier routes.Methods and resultsPART I : To reasearch the effect and merchanism of acetylcholine(Ach) in inducing canine acute AF model and study the effect of epicardial radiofrequency ablation of the atrium in inhibiting AF. It was performed on 10 mongrel dogs. In this study,intravenous(IV) infusion of Ach and atrial burst-pacing were performed on the dogs,then the dose of Ach was increased gradually according to the duration of AF until sustained AF(lasting^3minutes) could be induced, in group I (n=5),left side epicardial radiofrequency ablation(RF) was performed firstly.After the inducible rate was measured,right side ablation was performed.In group II(n=5),right side ablation was.7.performed firstly, then left.Heart rate,corrected sinus node recovery time (CSNRT) andatrial effective refractive period(ERP) were measured before and after Ach, and pressure of left ventricle,maximum ascending and desending velocity of left ventricle'spressure were also measured before and after Ach and after AF was induced.They were also measured after RF. RESULTS: The experiment succeed in all ten dogs.Before the Ach,sustained AF was fail to be induced by atrial burst-pacing. With the increasing of the dose of Ach ,the duration of AF prolonged.When the Ach increasing to a certain dose (18?ug.kg"1.min~I) ,sustained AF could be induced in all ten dogs by atrial burst-pacing and AF occurred spontaneously in one dogs.The mean duration was 344 +173s. In group I (n=5).sustain AF was still inducible after left side ablation,and after right side ablation ,sustain AF become uninducible except one dog. In group II (n=5) , AF become uninducible after right side ablation alone all dogs0 The dose of Ach was increased untill sustain AF was reinducible in the dogs.There are no significant antiarrhymia effect after left side ablation.Constant transmural lesion was confirmed by postmortem histological examination in all specimen.PART II : On the animal model induced by Ach, study the feasibility of epicardial radiofrequency ablation of the atrium guided by video-assisted thoracoscopic (VATS) in inhibiting AF and choose the simplest ablative routine.Firstly, the dose of Ach was recorded when AF was just induced as threshold. Under the guide.8.of VATS,in group I (n=4),left side epicardial ablation was performed firstly.After the in... |
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