B-type natriuretic peptide predicts future cardiac events in patients presenting to the emergency department with dyspnea.
STUDY OBJECTIVE
B-Type natriuretic peptide (BNP) is a neurohormone secreted from the cardiac ventricles in response to volume expansion and pressure overload. We have recently demonstrated that BNP can differentiate congestive heart failure (CHF) from other causes of dyspnea in patients presenting to the emergency department. In this study, we assess whether BNP levels drawn in patients presenting with dyspnea to the ED were a predictor of future cardiac events.


METHODS
In 325 patients presenting with dyspnea to the ED, BNP levels were determined. Patients were then followed up for 6 months to determine the following end points: death (cardiac and noncardiac), hospital admissions (cardiac), and repeat ED visits for CHF. Receiver operating characteristic (ROC) curves, relative risks (RRs), and Kaplan-Meier plots were used to assess the ability of BNP levels to predict future cardiac events.


RESULTS
The area under the ROC curve using BNP to detect a CHF end point-a CHF death, hospital admission, or repeat ED visit-was 0.870 (95% confidence interval [CI] 0.826 to 0.915). A BNP value of 480 pg/mL had a sensitivity of 68%, specificity of 88%, and an accuracy of 85% for predicting a subsequent CHF end point. The area under the ROC curve using BNP to detect death from CHF was 0.881 (95% CI 0.807 to 0.954) and for any cardiac death was 0.877 (95% CI 0.822 to 0.933). BNP was not associated with death from noncardiac causes. Using Kaplan-Meier plots for all CHF events, rising BNP levels were associated with a progressively worse prognosis. Patients with BNP levels more than 480 pg/mL had a 51% 6-month cumulative probability of a CHF event. Alternatively, patients with BNP levels less than 230 pg/mL had an excellent prognosis with only 2.5% incidence of CHF end points. The RR of 6-month CHF death in patients with BNP levels more than 230 pg/mL was 24.1. The RR of 6-month noncardiac death with BNP levels more than 230 pg/mL was 1.1. BNP levels were also predictive of CHF events in subsets of patients with positive CHF histories and ED diagnoses.


CONCLUSION
In this study population, BNP levels measured in patients presenting with dyspnea to the ED are highly predictive of cardiac events over the next 6 months.