索他洛尔对兔在体心脏左心室壁心肌复极不均一性影响的实验研究

Experimential study on myocardial repolarization heterogeneity across the left ventricular wall in vivo

目的 观察索他洛尔对兔在体心脏左心室壁各层心肌复极的影响 ,以证实在体心肌 M细胞的存在 ,探讨其与心律失常的关系。 方法 采用单相动作电位 (m onophasic action potential,MAP)记录技术 ,同步记录 12只开胸兔左心室外膜心肌 (epicardium ,Epi)、中层心肌 (m id- myocardium ,Mid)和心内膜心肌 (endocardium ,Endo)的 MAP,静脉注射索他洛尔后 ,测量 3层心肌 MAP的复极时限和跨心室壁心肌复极离散度 (transm ural dispersion of repolarization,TDR)。 结果 1用药前 Epi、Mid、Endo的 MAP10 0 %复极时限 (APD1 0 0 )分别为 (136± 16 )、(15 2± 19)、(15 0± 2 0 ) m s,TDR为 (17± 8) m s。每间隔 30 m in静脉注射索他洛尔 0 .5、1.0、1.5和 2 .0 m g· kg- 1后发现 ,索他洛尔剂量依赖性延长 3层心肌的 APD1 0 0 ,其中以延长 Mid的 APD1 0 0 更为明显 ,对 Epi和 Endo的 APD1 0 0 延长程度相近 ,使 TDR增加 ;至静脉注射 2 .0 mg· kg- 1 后 ,Epi、Mid、Endo的 APD1 0 0 分别为 (177± 30 )、(2 34± 32 )、(194± 30 ) ms,TDR为 (5 7± 15 ) ms(P <0 .0 5 ) ;2索他洛尔剂量依赖性地增加尖端扭转性室性心动过速 (torsade depointes,TDP)的发生率。 结论 在体兔心肌存在 M细胞。

Objective To observe the effect of sotalol on repolarization heterogeneity across the left ventricular wall,and confirm the existence of M cells in rabbit in vivo. Methods With the monophasic action potential (MAP) recording technique,MAPs of epicardium(Epi),mid myocardium(Mid) and endocardium(Endo) were recorded by specially designed plunge needle electrodes at the left ventricular myocardium in 12 open chest rabbits.Action potential duration at 100% repolarization(APD 100 )and transmural dispersion of repolarization(TDR) were measured. Results ①Before intravenous injection of sotalol,APD 100 in Epi、Mid and Endo were (136±16)、(152±19)、(150±20)ms,TDR was (17±8)ms.After intravenous injection of sotalol with different doses,APD 100 were prolonged dose dependently in all three myocardial layers,but more markedly in Mid,and as a result,TDR was increased obviously.When the dose of 2 0mg·kg -1 sotalol was used,APD 100 were (177±30)、(234±32)、(194±30) ms in Epi、Mid and Endo,TDR(57±15) ms( P <0.05);②Sotalol increased the incidence of torasde de pointes with dose dependence. Conclusion The M cells do exist in vivo rabbit myocardium.Sotalol increases repolarization heterogeneity across the left ventricular wall and its proarrhythmic effect might be related to that.