Stress-Delta B-Type Natriuretic Peptide Does Not Exclude ACS in the ED

Background: There are many detectable changes in circulating biomarkers in the setting of myocardial ischemia. We hypothesize that there are associated changes in circulating B-type natriuretic peptide (BNP) level after stress-induced myocardial ischemia, which can be used for emergency department (ED) acute coronary syndrome (ACS) risk stratification. Methods: In a prospective study, we enrolled 340 patients over the age of 30 receiving an exercise echocardiography stress test in an ED observational unit for suspected ACS. We collected blood samples at baseline and at 2 and 4h post-stress test, measuring the relative and absolute changes (stress-delta) in plasma BNP concentrations. In addition, patients were contacted at 90 days and at 1 year posttest for a follow-up. We calculated the diagnostic test characteristics of stress-delta BNP for a composite outcome of ischemic imaging on stress echocardiogram, nonelective percutaneous coronary intervention, coronary artery bypass graft surgery, subsequent acute myocardial infarction, or cardiac death at 1 year via a logistic regression. We analyzed the 2-h BNP concentrations using an ANOVA model to adjust for the baseline BNP level. Results: Baseline and 2-h post-stress BNP were both higher in the positive outcome group, but the stress-delta BNP was not. Stress-delta BNP had a sensitivity and specificity, respectively, of 53% and 76% at 2h and 67% and 68% at 4h. It was noted that patients with the composite outcome had a higher baseline BNP level. Conclusions: BNP stress-deltas are poor diagnostic means for ACS risk stratification, but resting BNP remains a promising prognostic tool for ED patients with suspected ACS.