Myocardial ischemia, cardiac troponin, and long-term survival of high-cardiac risk critically ill intensive care unit patients*

OBJECTIVES: To determine the incidence and association of myocardial ischemia with troponin elevation and survival in high-cardiac-risk intensive care patients. DESIGN: Prospective observational study. SETTING: Intensive care unit of a tertiary hospital. SUBJECTS: One-hundred one general intensive care unit patients having a history of coronary artery disease or at least two risk factors for coronary artery disease. INTERVENTIONS: Continuous 12-lead electrocardiographic monitoring with on-line ST-trend analysis, daily cardiac troponin measurements, clinical and physiologic assessment, and up to 2-yr follow-up for survival. MEASUREMENTS AND MAIN RESULTS: During 8,988 hrs or a mean +/- sd of 95 +/- 85 hrs/patient of continuous 12-lead electrocardiographic monitoring, 21 patients (21%) had ischemic ST-segment changes, characterized in most (19) by ST depression and lasting >60 mins in 15 (71.4%). Of the 38 patients (38%) with troponin elevation, myocardial infarction was clinically suspected in four and myocardial ischemia on continuous 12-lead electrocardiographic monitoring was observed in 14 (36.8%). Fourteen (66.7%) of the patients with ischemic ST changes and 12 (75%) of those with prolonged (>60 mins) ischemia had troponin elevation. The sensitivity, specificity, and positive and negative predictive values of prolonged (>60 mins) ischemia predicting troponin elevation were 31.6%, 95.2%, 80.0%, and 69.8%, respectively. Prolonged (>60 mins) ischemia was significantly associated with troponin elevation by both univariate and multivariate analyses (odds ratio = 9.0; p = .008). Acute Physiology and Chronic Health Evaluation II score, renal failure, and the use of norepinephrine also independently predicted troponin elevation. Troponin but not ischemia predicted increased 1-month, 6-month, and 2-yr mortality (odds ratio = 6.0, 3.2, and 2.99, respectively; p < .001). CONCLUSIONS: Silent ischemia is strongly associated with troponin elevation in high-cardiac-risk intensive care unit patients, and troponin elevation predicts both early and late mortality.