RESUMO
The diagnosis of unstable angina (troponine undetectable) is often difficult in the absence of electrocardiographic changes after suggestive chest pains. The object of this study was to analyse the kinetics of Brain Natiuretic Peptide (BNP) during acute coronary syndromes (ACS) without ST elevation. Plasma BNP was measured every 6 hours for 48 hours in 65 patients admitted for suspicion of ACS without ST elevation and without clinical, radiological or echocardiographic signs of left ventricular dysfunction. The results of BNP measurements were masked until the final diagnosis was established on the usual investigations (ECG changes, troponine I values, myocardial scintigraphy, coronary angiography). These investigations identified 3 groups of patients: non-Q wave infarction (group A: 19 patients), unstable angina (group B: 21 patients) and non-coronary chest pain (group C: 25 patients). The peak BNP was significantly higher in groups A (210 +/- 172 pg/ml) and B (152 +/- 159 pg/ml) than in group C (16 +/- 14 pg/ml). However, the BNP was normal or only slightly increased (< 50 pg/ml) in 25% of cases of ACS. Analysis of the kinetics of BNP was much more discriminating: early increase after the pain, peak between the 14th and 24th hours (19th hour on average), followed by a progressive decrease. The kinetics were identical in Groups A and B, contrasting with the flat profile of the curve in group C. A change of > 20 pg/ml in BNP was a better criterion of ACS with a diagnostic accuracy > 90% than increased troponine (group A) or undetectable troponine (group B). The authors conclude that BNP kinetics is a new and reliable diagnostic marker of unstable angina when the usual criteria of ACS are not present (notably a normal ECG and undetectable troponine).
