Objective: To determine the incidence and effect of unrecognized cardiac injury in critically ill patients.
Design: Prospective, blinded, single-center study.
Setting: The medical and respiratory intensive care unit of an academic health center.
Patients: Two hundred nine patients (224 admissions).
Main outcome measures: Daily measurement of levels of cardiac troponin I, a sensitive, highly specific, and long-lived marker of myocardial injury. Concurrently, signs and symptoms potentially related to myocardial ischemia were tabulated by blinded investigators. All clinical evaluation and management decisions were made by the physicians responsible for the care of the patient.
Results: Thirty-two (15%) of the 209 patients had evidence of myocardial damage based on elevated levels of cardiac troponin I. Only 12 (37%) of these 32 patients were diagnosed as having acute myocardial infarction by the intensive care unit staff. Cardiac damage was unrecognized in the other 20 (63%). Unrecognized cardiac injury was more common in young patients and in blacks. Mortality in patients with myocardial injury that was recognized (42%) or unrecognized (40%) was higher than in those without myocardial injury (15%) (P < .001). Patients with cardiac injury were more frequently hypotensive (75% vs 50%; P = .007) and in need of mechanical ventilation (66% vs 27%; P < .001) and had longer intensive care unit stays (5.3 vs 3.1 days; P < .007) than patients without cardiac injury.
Conclusion: The incidence of myocardial injury defined by elevated levels of cardiac troponin I was unexpectedly high and associated with increased morbidity and mortality. Clinically, it was often unrecognized.