Antiarrhythmic Effects Of Angiotensin Converting Enzyme Inhibitors During The Postischemia Reperfusion Period

Objective: To investigate the antiarrhythmic effects of Angiotensin- Converting Enzyme during the postischemia-reperfusion period in rabbits,the mechanism is also studied.Methods: A total of 30 Newzealand white rabbits underwent 30-min Coronary occlusion and 90 -min reperfusion.The duration of ventricular tachycardial and incidence of ventricular premature beats were analysed.Blood pressure and the electrocardiogram were monitored throughout the experiment and the mean artery pressure and heart rate were recorded during the control period, 15 and 30 minutes of occlusion, 15, 30, 60 minutes of reperfusion. 30 rabbits were divided into three groups at random. Saline, captopril or enapril were administrated 5 minutes before LAD occlusion and 5 minutes before reperfusion. saline group:treated with saline (5ml each time); captopril group :treated with captopril (2mg/kg, diluted to 10ml with saline, 5 ml each time);enapril grouprtreated with enapril (1.25mg/kg,diluted to 10ml with saline, 5ml each time).Blood samples obtained during 10 minutes before occlusion, 15 minutes after occlusion, and 15 , 30 , 60 minutes after reperfusion. The content of plasma MDA ,ET-1 and the activities of SOD were measured.90 minutes after reperfusion, the myocardial ultrastructures of all the 30 samples were investigated.4 additional rabbits without coronary occlusion were obtained as normal control and only investigated the ultrastructure of the uninjured myocardium..Results: The mean artery pressure descending during the postischemic-reperfusion, but there were no statistical meaning between the groups. The heart rate is unvariable throughout the experiments.In saline control group, the average duration of ventricular tachycardia was 21.25±2.13 seconds,and the total number of ventricular premature beats was 162± 11.Captopril significantly reduced the duration to 11±3.15 seconds (p <0.05),and the number of ventricular premature beats to 72±15 (p<0.05).Enapril significantlyreduced the duration of ventricular tachycardia to 9.8 ±4.1 seconds(p < 0.05) and the number of ventricular premature beats to 80±9(p< 0.05).During postischemic-reperfusion, MDA and ET-1 content in plasma were significantly increased and the activities of SOD were significantly decreased compared with the base condition(before coronary occlusion). Saline treated group compaired with both captopril treated group and enapril treated group, significantly increased the plasma content of MDA and ET-1, and also the activities of SOD were significantly decreased after occlusion. Compared with the saline group,the captopril treated group and enapil treated group showed the significantly slighter ultrastructure changes, and the significantly lower score of mitochondria and myofibril. Compared with the normal control group, all occlusion groups showed significantly ultrastructure changes.While the score of mitochondria and myofibril were significantly higher than the normal control group.Conclusion:1. Antiarrhythmic effects could provided by Angiotensin- Converting Enzyme Inhibitors during the postischmic- reperfusion.2. Angiotensin-Converting Enzyme Inhibitors play the antiarrhythmic effects through the role of free radical and oxidant scavenging.3. The mechanism of postischemic-reperfusion antiarrhythmic effects of Angiotensin-Converting Enzyme Inhibitors probably is the suppression of endogenous endothelin secretion.