Measurement of cardiac troponin I levels in the emergency department: predictive value for cardiac and all-cause mortality

Objective: To assess the predictive value of cardiac troponin I levels in c ardiac and all-cause mortality in patients presenting to an emergency depar tment. Design: A prospective cohort study. Setting: The emergency department of a major tertiary teaching hospital in metropolitan Melbourne over a six-week period in 1998, Patients: All patients with requests for cardiac enzyme level measurement. Main outcome measures: Cardiac and all-cause mortality within 30 days of pr esentation. Results: 424 patients (232 men, 192 women; age range, 16-93 years) were rev iewed. The 30-day mortality rate was 7.3% (31/424); in patients with raised levels of both creatine kinase (CK)-MB isoenzyme and troponin I this rate was 27% (7/26; 95% CI, 13%-44%); and in those with troponin I levels above 2 mug/L, but normal CK-MB values, it was 24% (5/21; 95% CI, 5%-43%), The mo rtality rate in the group with normal results of cardiac markers was 4.3% ( 14/328; 95% CI, 2.1%-6.5%), Patients with minor increases in troponin I lev els (minimal myocardial damage) showed an intermediate 30-day mortality rat e (13%, 5/39; 95% CI, 2%-24%). Other predictors of 30-day mortality include d age, presentation with shortness of breath, and electrocardiography (ECG) changes diagnostic of acute myocardial infarction or consistent with ischa emia. Cardiovascular causes were responsible for most of the deaths in pati ents with raised troponin I levels. Multivariate logistic regression analys is showed that raised levels of troponin (> 2.0 mug/L), but not of CK-MB, p redict 30-day mortality rate. Conclusions: Compared with CK-MB, cardiac troponin I more accurately predic ts 30-day mortality rates in patients presenting to the emergency departmen t. Moreover, troponin I levels identify additional groups of patients at in creased risk of death not so identified by measuring CK-MB values.