Plasma amino-terminal pro-brain natriuretic peptide levels in subjects presenting to the Emergency Department with suspected acute coronary syndrome: possible role in selecting patients for follow up?

Abstract

Plasma amino-terminal pro-brain natriuretic peptide (NT-proBNP) level is a sensitive and specific indicator of cardiac dysfunction. To determine whether plasma NT-proBNP level is elevated at the time of presentation with acute coronary syndrome (ACS) and whether it may assist in the diagnosis of heart failure and myocardial ischaemia in the Emergency Department. Plasma NT-proBNP levels were measured prospectively in 201 unselected presentations to the Emergency Department with suspected ACS where cardiac injury markers were requested by clinicians as part of routine assessment. NT-proBNP levels were correlated with clinical, electrocardiogram (ECG), biochemical and radiological findings. Elevated NT-proBNP level detected heart failure with high sensitivity (95-96%). Among patients without heart failure, NT-proBNP levels were increased more frequently in patients with previously diagnosed ischaemic heart disease. Elevated NT-proBNP level predicted cardiomegaly and a cardiac cause of presentation. However, the NT-proBNP level was not associated with ECG or biochemical markers of myocardial ischaemia, and only one-third of patients with ACS showed an increase of 40% or more in NT-proBNP level at repeat measurement of cardiac injury markers 5 h after presentation. Although elevated NT-proBNP level detected heart failure with high sensitivity, NT-proBNP level did not assist in the diagnosis of acute myocardial ischaemia. These findings indicate that the major determinant of elevated NT-proBNP level on presentation with suspected ACS was underlying cardiac dysfunction rather than acute myocardial ischaemia. This suggests that NT-proBNP measurement in patients with a suspected cardiac reason for presentation to the Emergency Department may identify a previously unrecognized group of patients without acute ischaemia who may nevertheless benefit from further investigation of cardiac function.