Changes and Clinical Significance of Plasma NT-proBNP Levels in Patients with Previous Myocardial Infarction Associated with Asymptomatic Heart Failure

Objective:To investigate the changes and clinical significance of plasma N-terminal pro-brain natriuretic peptide(NT-proBNP) levels in patients with previous myocardial infarction associated with asymptomatic heart failure.Methods:Eighty-three outpatients with a previous history of myocardial infarction not associated with symptoms of heart failure for at least one year were chosen.The concentrations of Plasma NT-proBNP were measured by enzyme-linked immunosorbent assay(ELISA).Colored Doppler echocardiography was performed to evaluate the left ventricular function.The outpatients were divided into two groups: ejection fraction(EF)≥0.5 group(n=41) and EF0.5 group(n=42) group.Results:The plasma NT-proBNP level was significantly higher in the EF0.5 group than that in the EF≥0.5 group[(1 123.8±234.3)fmol/mL vs(505.0±86.9)fmol/mL,P0.001].There were significantly negative correlations between plasma NT-proBNP concentration and EF,left ventricular fraction shortening(FS)(r=-0.96,P0.001 and r=-0.93,P0.001,respectively) in the EF0.5 group,while there were no correlations between these parameters in the EF≥0.5 group.The receiver operating characteristic(ROC)curve of concentrations of the plasma NT-proBNP in the diagnosis of asymptomatic heart failure showed: the sensitivity was 95.24%,specificity 92.68%,positive predictive accuracy value 93.02%,negative predictive accuracy value 95.00%,positive likelihood ratio 13.02,and area under ROC curve 0.940 for a plasma NT-proBNP cut-off level of 675 fmol/mL.Conclusion:The plasma NT-proBNP level is a good indicator for diagnosing asymptomatic heart failure in patients with a previous history of myocardial infarction.It increases with the increased severity of heart failure,and it can reliably reflect the left ventricular function.