心房颤动心房肌细胞短暂外向钾电流的特点

观察心房颤动 (AF)心房肌细胞的电生理特点 ,探讨短暂外向钾电流 (Ito)与AF电重构的关系。采用组织块酶消化法分离 7例AF(AF组 )和 14例非AF(非AF组 )患者的右心耳心房肌细胞 ,利用全细胞记录技术观察单个心房肌细胞的Ito。在各钳制电位下 ,AF组的Ito值均明显低于对照组。钳制电位在 + 60mV时AF组的Ito值 ( 14 2 .87±4 2 .2 5pA)与非AF组 ( 4 80 .12± 3 9.2 4pA)相比 ,减少 70 .2 4 %(P <0 .0 0 1)。在各钳制电位下 ,AF组的稳态电流 (Isus)均高于非AF组。钳制电位在 + 60mV时AF组的Isus值 ( 83 1.88± 72 .90pA)与非AF组 ( 5 4 3 .93± 65 .3 4pA)相比 ,增加 5 2 .94 %(P <0 .0 1)。随着刺激频率的增加 ,AF与非AF患者心房肌细胞在钳制电位 + 60mV时的Ito强度逐渐降低 ,与非AF组不同的是 ,AF组心房肌细胞的Ito在刺激频率 1～ 2Hz间电流改变的差异具有显著性。结论 :AF心房肌不应期的缩短与Ito的降低有关 ,Ito可能是AF电重构的离子机制 ,Isus可能也参与了电重构的发生。

The Characteristics ofTransient Outward Potassium Current in Single Atrial Myocytes With Atrial Fibrillation.

The aim of this research was to elucidate the relation between transient outward potassium current (Ito) and electrical remodeling in atrial fibrillation (AF).Specimens of human atrial appendage were obtained from 21 patients (7 with AF,14 without AF).Single atrial cells were isolated by tissue chunk enzymatic dissociation techniques.Ito was studied by whole cell patch clamp.Ito amplitudes were significantly reduced at all test potentials,mean current densities at +60 mV in cells isolated from patients with AF were slower than that in cells without AF (142.87±42.25 pA,n=12,compared with 480.12±39.24 pA,n=18,P<0.001),it fell by 70.24%;whereas steady-state outward current (Isus) amplitudes were higher in cells isolated from patients with AF than that in cells without AF (831.88±72.90 pA,n=12,compared with 543.93±65.34 pA,n=18,P<0.01),it increased by 52.94%.In addition,Ito in cells isolated from patients with AF was rate dependent at rates between 1 and 2 Hz.Conclusion:The changed Ito and Isus favor the development of electrical remodeling in AF,and thus contribute to the initiation and perpetuation of arrhythmia.