['We compared the diagnostic performance of N-terminal pro-brain natriuretic peptide (NT-proBNP) with a newly developed assay for the midregional part of pro-atrial natriuretic peptide (MR-proANP) concerning the detection of impaired left ventricular ejection function (LVEF) among patients with coronary artery disease (CAD).', 'Plasma levels of MR-proANP and NT-proBNP were determined in 102 consecutive patients with a history of ST-elevation myocardial infarction. Plasma levels of both markers were measured during a mean follow-up period of 687 days after acute myocardial infarction. Univariate analyses revealed inverse correlations between MR-proANP levels and LVEF (r=-0.39; p<0.001), NT-proBNP levels and LVEF (r=-0.39; p<0.001) and a positive correlation between MR-proANP and NT-proBNP (r=0.75; p<0.001). After adjustment for traditional risk factors, MR-proANP was the strongest predictor for LVEF (p=0.001) in multivariate analysis, being even superior to NT-proBNP. The area under the ROC curve (AUC) indicated moderate performance (AUC=0.73; p<0.01) of MR-proANP regarding the detection of a reduced LVEF<50%. The AUC of NT-proBNP for detection of impaired LVEF<50% was 0.68 (p=0.019). The negative predictive values of both markers were 86% for MR-proANP at a cut-off >135 pmol/L and NT-proBNP at a cut-off >560 pmol/L. At these cut-offs, the specificity of MR-proANP was 90%, and the specificity of NT-proBNP was 84%.'] Is midregional pro-atrial natriuretic peptide a useful indicator for the detection of impaired left ventricular function in patients with coronary artery disease?