OBJECTIVE This study sought to examine whether plasma brain natriuretic peptide levels can predict prognosis after myocardial infarction. BACKGROUND It has been suggested that concentrations of plasma brain natriuretic peptide reflect left ventricular function. Although the prognosis after myocardial infarction depends on residual left ventricular function, it is not known whether plasma levels of brain natriuretic peptide after the onset of myocardial infarction can be used to predict long-term outcome. METHODS Plasma brain natriuretic peptide and atrial natriuretic peptide levels as well as invasive hemodynamic variables were measured in 70 patients with acute myocardial infarction (53 men, 17 women; mean age 65 years). Measurements were obtained on admission (mean 6 h after onset) and on day 2 after onset. Mean follow-up period was 18 months. RESULTS Plasma brain natriuretic peptide levels measured on admission and day 2 correlated significantly with hemodynamic variables, which are influenced by left ventricular function. However, plasma atrial natriuretic peptide levels correlated with none of the hemodynamic variables measured on admission; and of those measured on day 2, plasma atrial natriuretic peptide levels correlated only with left atrial filling pressure. During the follow-up period (mean 18 +/- 7 months), 11 patients died of cardiac causes. By Kaplan-Meier analysis, it was found that patients with plasma brain natriuretic peptide levels higher than the median level, both on admission and on day 2, had significantly higher mortality rates than those with the submedian level (on admission, p < 0.01; on day 2, p < 0.05). However, only the plasma atrial natriuretic peptide level obtained immediately after admission was significantly related to survival (p < 0.01). By Cox proportional hazards model analysis of the noninvasive variables, it was found that plasma brain natriuretic peptide concentration was more closely related to survival after myocardial infarction (p = 0.0001). CONCLUSIONS Increased plasma brain natriuretic peptide concentrations in the early or subacute phase of myocardial infarction are a powerful noninvasive indicator of poor prognosis, possibly reflecting residual left ventricular function after myocardial infarction.