| Objective:To explore the effect of carvedilol on ventricular arrhythmia in rabbits after acute myocardial infarction(AMI) by investigating the effect of carvedilol on ventricular fibrillation threshold (VFT) and QTc interval dispersion(QTcd) in rabbits with acute myocardial infarction..And further to investigate the antiarrhythmia mechanisms of carvedilol.Methods: 36 rabbits were divided into three groups: Sham group, left thoracotomy but no circumflex coronary artery ligation, intragastric administration of saline 5ml/d for one week.AMI group, ligation of the circumflex coronary artery, intragastric administration of saline 5ml/d for one week; Carvedilol pretreatment group, the same operation as AMI group, and intragastric administration of carvedilol 3.3mg.kg-1.d-1 for one week. QTc interval dispersions were measured respectively at different time point as follow: before the opration, immediately after operation, and 1,4,and 24hours after operation ,and then 1 and 2weeks after operation by polylead-electrocardiogram (ECG) Two weeks after surgery, rabbits were harvested for the measured of VFT or ventricular tachycardiain (VT) vivo by electric stimulation procedure(cycle length of S1S2 was 100ms).In addition, incidence of induced ventricular fibrillation and malignant arrhythmia including ventricular tachycardia and ventricular fibrillation were recorded and magnesium in serum was determined.Results :1 Sham group : there was no statistical difference for the comparison of intragroup at the different time point(P>0.05), there was no statistical difference among the three groups before the operation(P>0.05). After ligation of the circumflex coronary artery, QTcd of Sham group was lower than AMI group and Carvedilol pretreatment group at the different time point after operation(P<0.05); VFT and magnesium in serum of Sham group were higher than that of AMI group at the 2th week after operation(P<0.05), but there was no difference compared with Carvedilol pretreatment group(P > 0.05). Incidence of ventricular fibrillation and malignant ventricular arrhythmia induced by electric stimulation procedure was lower than AMI group(P<0.05), but there was no difference between Sham group and Carvedilol pretreatment group(P>0.05). 2 AMI group: Intragroup QTcd at the different time point after operation was higher than that before operation except the 24th hour after operation(P<0.05). After ligation of the circumflex coronary artery, QTcd was increased significantly within 24 hours after operation, and QTcd was gradually decreased at 1th and 2th week after operation , but it is still increased than Sham group.After ligation of the circumflex coronary artery, QTcd of AMI group was higher than Sham group at the different time point after operation (P<0.05); VFT and magnesium in serum at 2th week after operation were lower than Sham group and Carvedilol pretreatment group(P < 0.05). Incidence of ventricular fibrillation and malignant ventricular arrhythmia was higher than Sham group and Carvedilol pretreatment group(P<0.05).3 Carvedilol pretreatment group: Intragroup QTcd at the different time point after operation was higher than that before operation except the 24th hour after operation(P<0.05). After ligation of the circumflex coronary artery, QTcd was increased significantly within 24 hours after operation(P<0.05), and QTcd was gradually decreased at 1th and 2th week after operation, but the extent to increase of QTcd was lower than AMI group; QTcd at five time point (immediately after operation,1,4,and 24hours after operation, and then 1week after operation ) was higher than AMI group(P<0.05), but there was no difference between two groups at 2th week after operation(P>0.05); VFT and magnesium in serum were higher than AMI group at 2th week after operation(P<0.05), but there was no difference between Sham group and Carvedilol pretreatment group(P > 0.05). Incidence of ventricular fibrillation and malignant ventricular arrhythmia was lower than AMI group(P<0.05), but there was no difference compared with Sham group(P>0.05).4 Relation of QTcd and VFT:QTcd and VFT was treated with linear correlation and linear regression in 36 rabbits, the results showed they were inverse correlation and correlation coefficient was -0.6458. According to regression variance analysis it showed linear regression relation. Linear regression equation of QTcd Y and VFT X was QTcd=113.001– 6.414 VFT. Fig.10, Fig.12, Fig.13.Conclusion:Carvedilol can decrease QTc interval dispersion in rabbits with acute myocardial infarction, increase their VFT and reduce the incidence of malignant arrhythmia. Therefore, carvedilol played a pole in preventing malignant arrhythmia .Carvedilol increased magnesium in serum and lessened the harmful effect of decrease of. magnesium in serum.
|
PDF Full Text Request