Elevated troponin and myocardial infarction in the intensive care unit: a prospective study

INTRODUCTION Elevated troponin levels indicate myocardial injury but may occur in critically ill patients without evidence of myocardial ischemia. An elevated troponin alone cannot establish a diagnosis of myocardial infarction (MI), yet the optimal methods for diagnosing MI in the intensive care unit (ICU) are not established. The study objective was to estimate the frequency of MI using troponin T measurements, 12-lead electrocardiograms (ECGs) and echocardiography, and to examine the association of elevated troponin and MI with ICU and hospital mortality and length of stay. METHOD In this 2-month single centre prospective cohort study, all consecutive patients admitted to our medical-surgical ICU were classified in duplicate by two investigators as having MI or no MI based on troponin, ECGs and echocardiograms obtained during the ICU stay. The diagnosis of MI was based on an adaptation of the joint European Society of Cardiology/American College of Cardiology definition: a typical rise or fall of an elevated troponin measurement, in addition to ischemic symptoms, ischemic ECG changes, a coronary artery intervention, or a new cardiac wall motion abnormality. RESULTS We screened 117 ICU admissions and enrolled 115 predominantly medical patients. Of these, 93 (80.9%) had at least one ECG and one troponin; 44 of these 93 (47.3%) had at least one elevated troponin and 24 (25.8%) had an MI. Patients with MI had significantly higher mortality in the ICU (37.5% versus 17.6%; P = 0.050) and hospital (50.0% versus 22.0%; P = 0.010) than those without MI. After adjusting for Acute Physiology and Chronic Health Evaluation II score and need for inotropes or vasopressors, MI was an independent predictor of hospital mortality (odds ratio 3.22, 95% confidence interval 1.04-9.96). The presence of an elevated troponin (among those patients in whom troponin was measured) was not independently predictive of ICU or hospital mortality. CONCLUSION In this study, 47% of critically ill patients had an elevated troponin but only 26% of these met criteria for MI. An elevated troponin without ischemic ECG changes was not associated with adverse outcomes; however, MI in the ICU setting was an independent predictor of hospital mortality.