Effects of ramipril on ventricular arrhythmia after myocardial infarction in rabbits / 中华急诊医学杂志

ABSTRACT

Objective To determine whether specific angiotensin-conventing enzyme inhibitor with ramipril would affect ventricular arrhythmia generation in rabbits after myocardial infarction and discuss the mechanism of its antiarrhymic efficacy.MethodsTwenty-four New Zealand rabbits (Wuhan Laboratory Animal Research Center) were separated into 3 groupssham-operated (SHAM) group (n =8 ),myocardial infraction (MI) group ( n =8) and myocardial infraction with ramipril (RAM) group ( n =8).SHAM group received a median sternotomy without left ventricular coronary artery ligation.MI and RAM groups' rabbits received a median sternotomy followed by left coronary artery ligation. The successful anterior MI was confirmed by elevation of the ST segment with more than 0.2 mV in lead Ⅱ and Ⅲ.After MI,RAM group rabbits were fed with ramipril [ 1mg/ ( kg · d) ]by intragastric administration for 12 weeks.Before and after MI 12 weeks in three groups.Ventricular tachycardia or fibrillation episodes and the monophasic actionpotential duration in epicardium,mid-myocardium and endocardium cadiocytes were recorded.The statistical technique was t-test and ANOVA.Results Ventricular tachycardia or fibrillation episodes were markedly decreased in RAM group than that in MI group after 12 weeks [ (2.6 ± 0.8) vs.(12.4 ± 2.9),P ＜0.05 ].After MI 12 weeks,the action potential duration of repolarization 90％ (APD90) of three-tier ventricular myocytes in MI group was prolonged than that before MI [ (258.2 ±21.1 ) vs.(230.1 ±23.2),( 278.0±23.8 ) vs.(245.8±25.4),(242.6±22.7) vs.(227.0±21.7),P＜0.05]; however,it was not significant difference between before and after MI 12w in RAM group (P ＞ 0.05 ).Moreover,the transmural dispersion of repolarization(TDR) was markedly increased after MI 12w in MI group than in SHAM and RAM group [ (36.2 ± 10.2 ) vs.( 18.7 ± 6.2 ),(24.9 ± 8.7 ),P ＜ 0.05 ]; but the TDR was not significant difference between RAM and SHAM group ( 18.7 ± 6.2 ) vs.( 24.9 ± 8.7 ),P ＞ 0.05].ConclusionsRamipril significantly reduced the malignant arrhythmia incidence in rabbits after MI.Mended the abnormal TDR was the mechanism for ramipril to therapy.