The Effect Of Autonomic Nerve System And The Third Fat Pad Radio Frequency Ablation On Atrial Electrophysiological Parameters In Dogs

Objective To investigate the effect of the autonomic nerve system(ANS) and radiofrequency ablation of the third fat pad on atrial electrophysiology parameters, including the atrial effective refractory period (AERP), the AERP dispersion , the rate adaptation of the AERP, the duration of the secondary atrial fibrillation(AF).Methods Male or female healthy mongrel dogs Eighteen cases, weight 11-20Kg, anesthesia was performed with sodium pentobarbital (initial bolus 30 mg/kg IV, 50 to 100 mg as needed for maintenance). The dogs were intubated and ventilated with dephlogisticated air. After right lateral thoracotomy , the heart was exposed in a pericardial cradle. Seven bipolar recording electrode were respectively sutured onto the low right atrial (LRA), the high right atrial(HRA), the right atrium appendage (RAA), the low left atrial(LLA), the high left atrial(HLA), the left atrium appendage (LAA). Surface ECG lead II/aVF and intracardiac tracings were recorded by use of a machine. Atrial electrophysiological characteristics at baseline were measured at 3 different basic cycle lengths (BCLs)(200ms,250ms,300ms). Finally, measurements were made every 10 minutes for 30minutes after the cessation of electrical stimulation . For cervical vagal nerve stimulation (VNS), the cervical vagosympathetic trunks were cut, and silver wires were introduced in the cranial end of the vagosympathetic trunk. Rectangular electrical stimulation were delivered at a frequency of 20 Hz and a pulse duration of 2 ms. The voltage chosen for right (left) VNS was 5 V above the voltage at which sinus arrest lasting 2 seconds (complete atrioventricular [AV] block) was achieved. These stimulation strengths were also applied during bilateral VNS and were kept constant during the experiment. Atropine was administered as 0.04 mg/kg initial bolus with a maintenance dose of 0.007 mg/kg per hour to exclude the influence of parasympathetic nerve. Metoprolol was administered as 0.1 mg/kg initial bolus with a maintenance dose of 0.04 mg/kg per hour to exclude the influence of sympathetic nerve. Delivery of radiofrequency current occurred in a unipolar mode between one of the splines and a cutaneous patch electrode. Six dogs were given radiofrequency ablation of the third fat pad with maximum temperature set at 30℃and maximal energy at 60 W. The endpoint of ablation was the elimination of heart rate which was eliminated at least 10% with vagal stimulation. The measurement of atrial electrophysiology characteristics were observed at different conditions.Results (1) During supramaximal bilateral VNS, the AERP at all seven atrial sites shortened (p<0.05), the dispersion of AERP prolonged. The percentage of AERP shortening at each of these 7 atrial sites is illustrated, especially in low left atrial (p<0.05). It demonstrates that the adaption of atrial effective refractory period is concorded , which atrial effective refractory period is not correlated with basic cycle length. (2) Excluding the influence of vagal nerve by atropine, AERP increased obviously , with statistic significance(p<0.05). The dispersion of AERP shortened, The correlation of AERP and different sites and different basic cycle length showed multiple linear regression . The correlation of AERP and different basic cycle length is positive. In our experiment, the contribution of is more in basic cycle length than sites. (3) Excluding the influence of sympathetic nerve by metropol, AERP increased obviously , with statistic significance(p<0.05). The dispersion of AERP shortened, The correlation of AERP and different basic cycle length is positive. (4) The difference of heart rate is no statistic significance after radiofrequency ablation of the third fat pad. The dispersion of AERP is no statistic significance(p>0.05). AERP shortened in HLA, LLA, LAA; AERP prolonged in LRA, HRA, RAA(p<0.05).Conclusion (1) AERP shortened, the dispersion of AERP increased by Vagal stimulation. It has been established that the vagus correlates with the pathogenesis of AF. (2) Excluding the influence of sympathetic nerve, AERP shortened, as to atropine can decreased electrical remodeling. (3) Sympathetic nerve and vagal nerve interacted complicated. (4) The imbalance of Sympathetic nerve and vagal nerve is important, and unevenness distribution after radiofrequency ablation of the third fat pad.