Myoglobin and troponin I elevation predict 5-year mortality in patients with undifferentiated chest pain in the emergency department

Background: The long-term prognostic significance of elevated cardiac markers in an undifferentiated patient population with chest pain is unknown. Methods: Serum troponin I (cTnI), creatine kinase-MB (CK-MB), and myoglobin were measured at presentation in 951 consecutive patients evaluated in the emergency department for possible acute coronary syndrome, and all-cause mortality was measured over 5 years. Results: Final diagnoses included myocardial infarction in 70 (7.4%), unstable angina in 78 (8.2%), stable angina in 26 (2.7%), heart failure in 135 (14.2%), syncope in 61 (6.4%), arrhythmia in 62 (6.5%), and noncardiac diagnoses in 519 (54.6%). Our study population had a mean (±SD) age of 63 (±16), 434 (46%) were male, 774 (81%) were African American, 408 (43%) had known coronary artery disease, 647 (68%) had hypertension, 244 (26%) had diabetes mellitus, and 237 (25%) had a serum creatinine ≥1.5 mg/dL. At 5 years, there were 349 (36.7%) deaths. In a multivariate model with adjustment for baseline covariates, an elevated cTnI ≥1.0 ng/mL (hazard ratio [HR] 1.7, 95% CI 1.3-2.3) and myoglobin ≥200 ng/mL (HR 1.6, 95% CI 1.2-2.1), but not CK-MB ≥9.0 ng/mL (HR 0.9, 95% CI 0.6-1.3), remained independent predictors of all-cause mortality. Patients with both elevated cTnI and myoglobin had a particularly high mortality rate. Conclusion: Among patients evaluated in the emergency department for possible acute coronary syndromes, myoglobin and cTnI at presentation are powerful, independent predictors of long-term (5-year) prognosis.