ABSTRACT
BACKGROUND: Patients with unstable angina or non Q wave myocardial infarction still have an elevated risk for subsequent cardiac events. Therefore early assessment of the risk of future cardiac events is important. In this study, prognostic value of troponin l and myoglobin was evaluated and compared with other known early available risk indicators. METHODS: Serum troponin l and myoglobin were measured at presentation and 8 hours, 16 hours, and 24 hours thereafter in 126 patients with unstable angina (n=70) or non Q myocardial infarction (n=56) from Jan 1998, through Feb 2000. Echocardiography was performed with calculation of wall motion score index. The incidence of cardiac death or myocardial infarction was compared between patients with normal troponin l, myoglobin and abnormal ones, respectively. RESULTS: (1) At 6 months, 1 death (2.2%) and 1 myocardial infarction (2.2%) occured in the 45 unstable angina patients with normal troponin l compared with 3 deaths (12.0%) and 8 myocardial infarctions (32.0%) in the 25 unstable angina patients with elevated troponin l. (2) At 6 months, 1 death (1.7%) and 3 myocardial infarctions (5.2%) occured in the 58 unstable angina patients with normal myoglobin compared with 3 deaths (25.0%) and 6 myocardial infarctions (50.0%) in the 12 unstable angina patients with elevated myoglobin.(3) When the analysis was limited to patients with normal baseline troponin l (< or = 0.4 ng/dl: n=45), increased myoglobin level remained significantly associated with increased incidence of cardiac deaths or myocardial infarction compared with normal myoglobin level (16.7% vs 0%). (4) Together with age, diabetes, wall motion score index, troponin I and myoglobin levels were identified as independent prognostic variables for myocardial infarction or cardiac death in a multivariate logistic regression analysis. (5) The maximal troponin l and myoglobin value obtained during the first 24 hours provides independent and important prognostic information regardless of whether the patient is classified as having unstable angina or non Q wave myocardial infarction. CONCLUSION: The maximum troponin l and myoglobin obtained during the first 24 hours provides independent and important prognostic information in patients with unstable angina or non Q wave myocardial infarction.