Establishment Of A Canine Model Of Persistent Atrial Fibrillation By Chronic Rapid Pulmonary Vein Pacing And The Study Of The Electrophysiology About The Model

Atrial fibrillation(AF) is the most common cardiac arrhythmia. It severely damaged the health of the affected patients by causing stroke, decreasing heart function and developing myocardial disease. Work to date has identified that the pulmonary veins(PVs) play a basilic role in the paroxysmal AF. However, there were few studies about the role of the PVs in maintaining of persistent AF. In this study, we established a canine model of persistent AF by chronic rapid pulmonary vein pacing and studied the electrophysiology about the model. At last, we used radiofrequency(RF) energy to isolate the PVs from the atria in the canine model and then performed rapid pacing after ablation to study the change of the electrophysiology. These results are used to investigate the role of PVs in the maintenance of persistent AF and provide useful clues for the clinic therapy of persistent AF.Objective: 1,To investigate the feasibility of a persistent AF model of canine with chronic rapid pulmonary vein pacing. 2,To investigate the electrophysiological of the model and the changes of electrophysiological characteristics after ablating the pulmonary veins of the models.Method: 1,30 mongrel canines were randomly divided into experimental group(n=15) and control group(n=15). Canines of the experimental group were instrumented with annular pacing electrodes on the left superior pulmonary vein(LSPV) and mapping electrodes patches on the left atrium(LA). The annular pacing electrodes were connected in a stimulator with chronic rapid pulmonary vein pacing. Programmed electrical stimulation and burst pacing technique was used to examine whether the time of AF last more than 24h. 2,Biatrial areas were measured using two-dementional echocardiography before and after rapid pulmonary vein pacing in canines of the experimental group. 3,Six mapping electrodes patches were used to record the electrophysiological characteristics of canines of the experimental group, including all PVs, left atrium(LA) and right atrium(RA). RF was applied around the PVs to eliminate the electrical activity. Effective refractory period(ERP) and atrial fibrillation cycle length(AFCL) were measured before and after the ablation of PVs.Result: 1,Persistent AF(>24h) was induced in eleven of fifteen canines within 28.2±3.0 days. Persistent AF was induced in four of eleven canines without stimulating, five of eleven canines using programmed electrical stimulation and two of eleven canines using burst pacing. 2,At the end of the pacing period,biatrial areas were enlarged significantly(LA: 6.9±1.1cm2 vs 11.7±1.6cm2, P<0.05; RA: 4.3±0.8cm2 vs 7.0±1.2cm2, P <0.05). 3,In the canines of the experimental group, AFCL /ERP in free wall of the RA was significantly longer than that in the PVs and the LA free wall. AFCL /ERP in the PVs was the shortest. After ablation, all dogs converted to sinus rhythm, ERP and AFCL after re-induction were significantly longer than baseline(P<0.05).Conclution: The model with chronic rapid pulmonary vein pacing is highly reproducible, and persistent AF is readily inducible;the method is reliable and practical. PVs are important in the maintenance of AF in dogs. After the ablation of PVs using RF energy, persistent AF cannot be sustained. All of these provide useful clues for the clinic therapy of persistent AF.