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作为阵发性房颤的另外一个重要异位兴奋灶的起源部位,与右心房相比,上腔静脉有着独特的电生理学特性.本实验中,通过对兔的前腔静脉观察发现,在不同刺激频率下,前腔静脉心肌细胞APD90明显大于右心房;右心房和前腔静脉心肌细胞均可出现传导阻滞;少数前腔静脉心肌细胞可出现类似起搏细胞的慢反应动作电位与早期后去极化(EAD).进一步对去极化的电流进行分析时,实验证明,兔右心房和前腔静脉心肌细胞均存在一种特殊的离子通道电流:非特异性阳离子通道电流(nonselective cation current INs);前腔静脉的INs峰值电流密度小于右心房;去除细胞外二价阳离子和葡萄糖的灌流液可激动这种INs;在右心房心肌细胞上阻断INs,动作电位时程明显增大;在前腔静脉心肌细胞上激动INs,动作电位时程缩短.结果表明,前腔静脉心肌细胞具有异位激动能力及传导阻滞的条件;兔右心房和前腔静脉心肌细胞的动作电位时程的大小存在显著差异,部分由于INs在二者之间分布的差异所致;INs的激动剂或阻滞剂可以影响兔右心房或前腔静脉心肌细胞动作电位时程,从而可能影响前腔静脉出现早后去极化和电传导阻滞的发生.兔心房上的INs与TRPC3通道非常近似,它在阵发性心房颤动机制中可能起到一定的作用.
As the origin of another important ectopic foci of paroxysmal atrial fibrillation, the superior vena cava has unique electrophysiological properties compared with the right atrium.In this experiment, we observed in the anterior chamber veins of rabbits that in different APD90 of anterior vena cava myocardial cells was significantly greater than that of the right atrium at stimulation frequency; conduction block was found in both right atrium and anterior vena cava myocardial cells; a small number of anterior vena cava myocardial cells appeared similar to slow pacemaker action potential and early Depolarization (EAD) .At the further analysis of depolarized currents, experiments have shown that there is a special ion channel current in the right atrium and vena cava of rabbit: nonspecific cation current INs ); INs in the anterior vena cava peak current densities were less than in the right atrium; removal of extracellular cations and glucose in the perfusate stimulated this INs; blocked INs on the right atrial cardiomyocytes, the action potential duration increased significantly; at The anterior chamber ventricular cardiomyocytes excited INs, action potential duration shortened.The results show that the anterior vena cava myocardial cells with ectopic activation and conduction block conditions; the rabbit right atrium And the anterior chamber ventricular cardiomyocyte action potential duration of the size of significant differences, in part due to INs in the distribution of the difference between the two; INs agonists or blockers can affect the rabbit right atrium or anterior chamber ventricular cardiomyocytes Action potentials, which may affect the occurrence of anterior chamber depolarization and electrical conduction block in the anterior chamber veins.The INs of rabbit atria are very similar to TRPC3 channel, which may play a role in the pathogenesis of paroxysmal atrial fibrillation effect.