COMPARATIVE STUDY
JOURNAL ARTICLE

Sensitivity of routine intensive care unit surveillance for detecting myocardial ischemia

Elizabeth A Martinez, Lauren J Kim, Nauder Faraday, Brian Rosenfeld, Eric B Bass, Bruce A Perler, G Melville Williams, Todd Dorman, Peter J Pronovost
Critical Care Medicine 2003, 31 (9): 2302-8
14501960

OBJECTIVE: To assess the effectiveness of routine intensive care unit surveillance compared with frequent 12-lead electrocardiogram monitoring for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia in vascular surgery patients.

DESIGN: Prospective cohort trial.

SETTING: Intensive care unit.

PARTICIPANTS: We studied 149 patients undergoing elective infrainguinal or aortic vascular surgery who were admitted to the intensive care unit postoperatively.

INTERVENTIONS: Patients were simultaneously monitored with a 10-electrode/12-lead electrocardiogram obtained every 2 mins (criterion standard) and routine intensive care unit surveillance that included standard monitoring (five-electrode/two-lead electrocardiogram with ST segment trends and routine 12-lead electrocardiogram) and clinical assessment for detecting myocardial ischemia. The results of the criterion standard were not available to the caregivers.

MEASUREMENTS AND MAIN RESULTS: We measured the ability of routine intensive care unit surveillance to detect the first 20 mins of electrocardiogram evidence suggestive of myocardial ischemia, defined as ST segment depression or elevation of >/=1 mm in two consecutive leads, during the first postoperative day. Seventeen patients (11%) had electrocardiogram evidence suggestive of prolonged myocardial ischemia, the majority of which occurred in leads V2-V4. The sensitivity of routine intensive care unit surveillance for detecting the first episode of electrocardiogram evidence suggestive of prolonged myocardial ischemia in a patient was 12% (95% confidence interval, 7-17%), and the specificity was 98% (95% confidence interval, 95-100%) with a positive predictive value of 40% (95% confidence interval, 32-48%), a negative predictive value of 90% (95% confidence interval, 85-94%), a positive likelihood ratio of 6, and a negative likelihood ratio of 1. The sensitivity of routine intensive care unit surveillance for detecting all episodes was 3% (95% confidence interval, 2-3%) and the specificity 99% (95% confidence interval, 99-100%) per 20-min monitoring interval, with a positive predictive value of 17% (95% confidence interval, 16-18%), negative predictive value of 95% (95% confidence interval, 95-96%), positive likelihood ratio of 3, and negative likelihood ratio of 1.

CONCLUSIONS: Routine intensive care unit surveillance has low sensitivity for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia compared with frequent 12-lead electrocardiograms. Because detecting electrocardiogram evidence suggestive of prolonged postoperative myocardial ischemia is important, physicians should consider alternative strategies to detect myocardial ischemia.

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