氯沙坦对犬在体急性缺血心肌跨室壁复极不均一性的影响

目的:探讨氯沙坦对犬在体心肌急性缺血时跨室壁复极离散度(TDR)及心律失常发生率的影响。方法:16只健康家犬,均分为2组:①单纯缺血组:阻断左前降支主干30 min,同步记录犬在体心外膜、中层及心内膜心肌单相动作电位(MAP)及体表心电图,分析其相关参数的变化。②氯沙坦组:氯沙坦5mg·kg-1·d-1经胃管灌入,持续2周后开胸,余同单纯缺血组。结果:单纯急性缺血状态下3层心肌MAP时程(MAPD)均明显缩短,且心外膜、心内膜的MAPD缩短程度较中层心肌的MAPD缩短程度更为明显,心外膜、心内膜的MAPD与中层心肌的MAPD相比差异有显著性意义(P<0.05)。3层心肌间TDR增大。急性缺血30 min内,4只出现了室性心动过速或(和)心室颤动而死亡,恶性心律失常发生率达50％。氯沙坦组在急性缺血时,3层心肌MAPD缩短程度趋于一致,TDR较单纯缺血组减小,差异有显著性意义(P<0.05),无一例出现室性心动过速或(和)心室颤动,与单纯缺血组恶性心律失常发生率相比差异有显著性意义(P<0.01)。结论:氯沙坦可减小急性缺血心肌的TDR,且可能因此而降低急性缺血时恶性心律失常的发生率。

Effects of losartan on the electrical heterogeneity of ventricular wall during acute ischemia in canine in vivo

Objective:To explore the effects of losartan on the electrical heterogeneity of ventricular wall during acute ischemia in canine in vivo. Methods: In canine acute ischemic model, 16 dogs were divided into 2 groups, control group( n = 8) and losartan group( n =8). losartan (5 mg.kg-1.d-1 ) was administered for 2 weeks before operation. With monophasic action potential (MAP) recording technique , the MAPs in epicardium (Epi), mid-cardium and endocardium (Endo) were recorded simultaneously during myocardial ischemia in two groups. MAPD, transmural dispersion of repolarization (TDR) and arrhythmias were monitored. Results: During acute myocardial ischemia, MAPD90 was shortened remarkably in the Epi and Endo, modestly in the Mid. The difference of the MAPD90 between Mid and Epi or Endo was significant ( P <0. 05). TDR in the three layers of ventricular myocardium were increased. Ventricular tachycardia or ventricular fibrillation occured in 4 dogs under the condition of acute ischemia, but no malignant arrhythmia occurred in all dogs before acute ischemia. The TDR in the losartan group was smaller than that in the control group ( P<0.05). No ventricular tachycardia or ventricular fibrillation was found in the losartan group, the difference of the rate of malignant arrhythmia was significant between the two groups. Conclusion:The results suggest that losartan can suppress the TDR in acute ischemic myocardium, and decrease the development of malignant arrhythmias.