迷走神经和肺静脉刺激对心房肌动作电位和乙酰胆碱激活钾电流的影响

目的研究迷走神经和肺静脉快速刺激对心房肌动作电位和乙酰胆碱激活钾电流的影响。方法24只犬随机分为3组，每组8只犬。对照组：采用20Hz频率和0．2ms波宽刺激迷走神经，观察诱发心房颤动（房颤）情况。左上肺静脉（LSPV）刺激组：快速刺激LSPV4h，观察刺激前后左有心房和LSPV动作电位时限（APD）的变化，随后行迷走神经刺激，观察诱发房颤情况。迷走神经干预组：先采用5Hz频率、0．2ms波宽和5～10V电压刺激迷走神经30min，然后快速刺激LSPV4h，观察刺激前后APD的变化，冉迷走神经刺激观察诱发房颤情况。所有犬在电生理检测后开胸取心脏，分离LSPV和左右心房肌细胞，采用膜片钳技术观察乙酰胆碱激活钾电流（IK,ACh）变化。结果LSPV刺激组，APD。明显缩短，动作电位时限高散度（dAPD90）明显增加[（5±3）msVS（14±5）ms，P〈0．05]。迷走神经干预组，APD。无明显变化，但APD90-d明显增加[（6±3）mvs vs（12±5）ms，P〈0．05]。与对照组相比，LSPV刺激组细胞Ik、ACh明显增加，但对照组与迷走神经干预组相比，IK．ACh差异无统计学意义。结论APD缩短是胆碱能房颤诱发的基础，肺静脉快速刺激可增加IK．ACh密度，快速刺激前行迷走神经能阻止电重构的发生。

Different changes in action potential duration and IK,Ach after vagal stimulation plus pulmonary vein rapid pacing

Objective To investigate the changes of action potential duration(APD)and acetylcholine induced inward rectifier K+current(IK,ACh)after vagal stimulation(VS)plus pulmonary vein rapid pacing.Methods Twenty-four dogs were divided into three groups,each group including 8 dogs.In the control group,atrial fibrillation(AF)inducibility was investigated during VS at 20 Hz and 0.2 ms(VS1).In the left superior pulmonary vein(LSPV)pacing group,the LSPV was subjected to rapid pacing for 4 hours.APD was measured before and after pacing,after which,VS1 was delivered and tlle initiation of AF Was meagured.In the VS pacing group,VS Was delivered at 5 Hz,0.2 ms and 5～10 V(VS2)for 30 min.Then,the LSPV was subjected to rapid pacing for 4 hours.APD Was measured both before and after VS2 plus pacing.After that,initiation of AF was again measured during VS1.IK,ACh in LSPV and atrial myocardium Were measured by patch clamp.Results In tIIe LSPV pacing group,APD90 was abbreviated sharply and dispersion of APD90(dAPD90)increased significantly[(5±3)ms vs(14±5)ms,P<0.05],However,in the VS plus LSPV pacing group,APD90 was not changed significantly after pacing,while dAPD90 increased significantly[(6±3)ms vs(12±5)ms,P<0.05].In the LSPV pacing group,IK,ACh increased in the LSPV and atrial myocardium.However,there were no different changes in,IK,ACh between the VS plus LSPV pacing group and the VS group.Conclusions Decreased APD may be fundamental for the cholinergic induction of AF.LSPV rapid pacing can increase IK,Ach,however,VS before rapid pacing partly protects the atria from electrical remodeling.