Abstract: Objective: To explore the influence of carvedilol on the QT dispersion(QTd)in patients with acute myocardial infarction(AMI) at different times and its relation to the incidence of cardiac events.Methods: Fourty-three AMI patients were randomly divided into treatment group(23 cases) and control group(20 cases).The electrocardiogram(ECG)and Holter of the two groups were recorded and compared before therapy and at day 1,3,7,14 and 21 after therapy.The relationship between QTD and cardiac event was analyzed.Results: The QTd increased significantly at 24 h in patients with AMI but started to decrease at day 3,and the velocity was low.After 3 days of treatment with carediol,the QTd in the carwediol group decreased obviously compared with that in the control group(P<0.01).The incidence of cardiac events was 20% in the carvediol group while it was 34.8% in the control group(P>0.05).The max QTd of patients(77.19±10.81) with cardiac events was higher than that without cardiac events(58.15±9.71)(P<0.01).Conclusions: QTd increases obviously at the early stage of AMI.Carvediol may significantly lower the QTd of AMI and decrease the incidence of cardiac events.