N-terminal probrain natriuretic peptide predicts adverse outcomes in acute-myocardial infarction even with preserved left ventricular ejection fraction.

BACKGROUND: Risk stratification of patients with acute myocardial infarction is based on various clinical, biochemical or electrocardiographic parameters. There is emerging evidence that N-terminal probrain natriuretic peptides (NT-proBNP) possess characteristics of an ideal biomarker. In this study we looked into the role of NT-proBNP in risk stratification and prediction of short-term events in patients presenting with acute myocardial infarction (MI) and having preserved left ventricular functions as assessed by ejection fraction (EF) on echocardiography.

METHODS AND RESULTS: Of a total of 250 consecutive patients admitted with a diagnosis of acute ST segment elevation myocardial infarction, 84 patients were found to have ejection fraction greater than 50% (44 with anterior MI, 40 with inferior MI. Serum NT-proBNP was measured using electrochemiluminiscence assay (Roche). On two-dimensional echocardiography, modified Simpson's technique was used to measure the EF. Follow-up at day 30 included a two-dimensional echocardiography and assessment for worsening heart failure, recurrent ischemia, and repeat hospitalization. Death due to cardiovascular cause by 30 days was also noted. The mean value of NT-proBNP for those having EF over 50% was 1542.38 + 4649.12 pg/ml. For the purpose of a dichotomous analysis, the median value was determined (907.5 pg/ml). In patients having NT-proBNP above median, the Killip class was expectedly higher 1.62 + 0.21 vs 1.0 + 0.12 ( p< 0.05) and the thrombolysis in myocardial infarction scores were worse (4.77 + 1.56 vs 2.71 + 1.11, p < 0.05). The ejection fraction was similar (59.72 + 8.8 vs 58.76 + 6.9, p= NS) in the two groups. At 30 days followup, patients having NT-proBNP above median showed a further decline in the Killip class and EF. The clinical outcomes (composite of recurrent ischemia, worsening heart failure and repeat hospitalization) were also worse in this group ( p< 0.05).

CONCLUSION: In patients with apparently normal ejection fraction and without left ventricular dysfunction, a higher NT-proBNP level would suggest poorer short-term clinical outcomes and would require a more aggressive treatment strategy.