Elevated cardiac troponin levels in critically ill patients: prevalence, incidence, and outcomes.

Background: Levels of cardiac troponin, a sensitive and specific marker of myocardial injury, are often elevated in critically ill patients.
Objectives: To document elevated levels of cardiac troponin I in patients in a medical-surgical intensive care unit and the relationship between elevated levels and electrocardiographic findings and mortality.
Methods: A total of 198 patients expected to remain in the intensive care unit for at least 72 hours were classified as having myocardial infarction (cardiac troponin I level >or=1.2 microg/L and ischemic electrocardiographic changes), elevated troponin level only (>or=1.2 microg/L and no ischemic electrocardiographic changes), or normal troponin levels. Events were classified as prevalent if they occurred within 48 hours after admission and as incident if they occurred 48 hours or later after admission. Factors associated with mortality were examined by using regression analysis.
Results: A total of 171 patients had at least one troponin level measured in the first 48 hours. The prevalence of elevated troponin level was 42.1% (72 patients); 38 patients (22.2%) had myocardial infarction, and 34 (19.9%) had elevated troponin level only. After the first 48 hours, 136 patients had at least 1 troponin measurement. The incidence of elevated troponin level was 11.8% (16 patients); 7 patients (5.1%) met criteria for myocardial infarction, and 2 (1.5%) had elevated troponin level only. Elevated levels of troponin I at any time during admission were associated with mortality in the univariate but not the multivariate analysis.
Conclusions: Elevated levels of cardiac troponin I in critically ill patients do not always indicate myocardial infarction or an adverse prognosis.