Usefulness of N-terminal pro-B-type natriuretic peptide levels in predicting residual myocardial ischemia in patients with ST elevation acute myocardial infarction

AIM

N-terminal pro-b-type natriuretic peptide (NT pro-BNP) is a neurohormone synthesized predominantly in ventricular myocardium. In patients with symptoms of heart failure, elevation in NT pro-BNP accurately identifies ventricular dysfunction. However, NT pro-BNP levels are not specific for ventricular dysfunction in patients who do not have overt symptoms of heart failure, suggesting that other cardiac processes such as myocardial ischemia may also cause elevation in NT pro-BNP. The study was aimed to determine whether NT pro-BNP elevations are associated with myocardial ischemia.

METHODS

One hundred and thirty patients (104 males, 26 females, mean age 61+12 years), with ST elevation acute myocardial infarction (STEMI) and preserved left ventricular ejection fraction (>45%) at echocardiography performed at entry, from February 2003 and February 2004 were enrolled. In all patients NT pro-BNP plasma levels were checked at entry and 4-5 days after symptoms onset. In addition, maximal or symptom-limited exercise treadmill test (Bruce protocol), and myocardial perfusion scintigraphy using [(99m)Tc]Tetrofosmin single photon emission computed tomography (SPECT) imaging were performed within 30 days of STEMI. Ischemia was defined as reversible perfusion abnormalities.

RESULTS

Of the 130 participants, 66 (51%) had inducible ischemia. Compared with patients in the lowest tertile, those in the highest tertile of NT pro-BNP had a greater significant risk of residual ischemia (odds ratio: 8.66; 95% CI, 3.90 to 19.24). Nevertheless patients in the highest tertile were older (64.19+/-10.80 years versus 55.90+/-9.67 years, P = 0.0001), had a lower left ventricular ejection fraction (49.70+13.46% versus 59.49+/-6.58%, P = 0.0001) and had a great rate of acute myocardial infarction (anterior acute myocardial infarction = 40.63% versus 25%).

CONCLUSIONS

Elevated levels of NT pro-BNP are associated with residual myocardial ischemia among patients with STEMI and preserved left ventricular ejection fraction, as demonstrated by perfusion defect on SPECT imaging, suggesting that these patients may need further evaluation for stratification of the future risk of fatal events. The observed association between NT pro-BNP levels and ischemia may explain because tests for NT pro-BNP are not specific for ventricular dysfunction among patients with coronary artery disease.