N-Terminal Pro-B-Type Natriuretic Peptide Predicts Significant Coronary Artery Lesion in the Unstable Angina Patients With Normal Electrocardiogram, Echocardiogram, and Cardiac Enzymes

BACKGROUND: Brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) are not specific for ventricular dysfunction and other cardiac processes, such as myocardial ischemia, may also cause elevation of these markers. METHODS AND RESULTS: To determine whether elevation of NT-proBNP without elevation of cardiac specific markers can predict coronary artery disease (CAD), the serum level of NT-proBNP was measured in 161 patients with unstable angina (61.0+/-8.1 years, male 54.0%) with normal ventricular function (left ventricular ejection fraction >55% and no regional wall motion abnormality by echocardiography) and normal troponin I level (<0.05 ng/ml). In these patients, levels of C-reactive protein and myoglobin were normal and none had Q wave on electrocardiographic (ECG). The NT-proBNP level was higher in patients with CAD (n=74) than in patients without CAD (n=87) (173.1+/-231.6 vs 68.1+/-62.5 pg/ml, p<0.001). At the standard cut-off point of >200 pg/ml, elevated NT-proBNP level shows high probability of CAD (odds ratio, 10.1; 95% confidence interval, 2.6-38.7, p=0.001). The NT-proBNP level positively correlated with the extent of CAD (r=0.329, p=0.001). In multivariate analysis, the NT-proBNP was an independent predictor of CAD. CONCLUSION: These results suggested that NT-proBNP is a useful screening test for CAD in the unstable angina patients with normal ECG, echocardiogram and cardiac enzyme levels.