Using acoustic quantification(AQ)techonology to observe influence of QTd on left ven-tricular function in 51 cases of myocardiol infarction patients.Using 24 hours dynamic electrocardiogram (DCG)to detect cardiac arrhythmias in 43/51 cases of myocardiol infarction patients,and compared with 30cases of normal control subjects.The results showed that QTd in myocardial infarction(MI)patients was signifficantly longer than that in normal group(P<0.01),and the left ventricular systolic and diastolic function were also demaged compared with normal group.QTd in MI accompanying cardiac arrhythmia group was signifficantly longer than that in MI accom-panying sinus rhythm group(P<0.01),and left ven-tricular systolic and diastolic function in MI accompa-nying cardiac arrhythmia group were demaged com-pared with MI accompanying sinus rhythm group.It is concluded that QTd in MI patients was longer,and it may have relationship with left ventricular dysfunc-tion and the incdence of cardiac arrhythmia in myocar-diol infarction patients.