Abstract: AIM: To explore the relationship between plasma brain natriuretic peptide(BNP) and left ventricular ejection fraction(LVEF),left ventricular diastolic volume(LVEDV),and Killip classification and to evaluate the predictive value of BNP in patients with acute myocardial infarction(AMI).METHODS: A total of 120 AMI patients and 120 control subjects were investigated by measuring plasma BNP levels using MEIA.LVEF and LVEDV were assessed using echocardiography.RESULTS: Plasma BNP levels and LVEDV in AMI groups were significantly higher than those in control group;however,LVEF was significantly lower than that in control group(P<0.01).Plasma BNP levels and LVEDV in LVEF <40% group were higher than those in LVEF >50% group(P<0.05).BNP levels in Killip III and IV groups were also significantly higher than those in Killip I and II groups(P<0.05).Compared with those in patients with inferior myocardial infarction,BNP levels were significantly higher in patients with anterior myocardial infarction and inferior-posterior myocardial infarction(P<0.05).There was a positive correlation between BNP levels and Killip classification(r=0.97,P=0.029),but a negative correlation between BNP levels and LVEF(r=-0.33,P=0.0036).CONCLUSION: Plasma BNP levels are significantly increased in AMI patients,especially in patients with LVEF <40%,Killip IV or extensive anterior myocardial infarction.BNP indicates the severity of myocardial infarction,which may be an important predictor for left ventricular dysfunction.