Continuous 12-lead electrocardiographic monitoring in an emergency department chest pain unit: an assessment of potential clinical effect.

STUDY OBJECTIVES: Continuous 12-lead serial ECG monitoring has been proposed to assist in the evaluation of patients with acute coronary syndrome and nondiagnostic ECG in an emergency department chest pain unit. However, the ability of serial ECG to detect acute coronary syndrome and its benefit in addition to a standard protocol has not been established. We evaluate the ability of continuous 12-lead ECG to detect acute coronary syndrome, assess the incremental benefit of the serial ECG in association with a set protocol in an ED chest pain unit, and evaluate whether serial ECG changes could be considered as prognostic factors.

METHODS: Patients who met Agency for Health Care Policy and Research guidelines for intermediate risk for short-term cardiovascular event unstable angina were prospectively studied in the chest pain unit. Patients were monitored with the Mortara Instruments ELI 100 STM continuous 12-lead ECG system with ST-segment analysis. ST-segment changes of greater than 100 microV in 2 or more contiguous leads or greater than 200 microV in 1 lead were considered positive. Data were compared with serial serum cardiac markers, cardiac function study results, angiographic results, and 30-day outcome results.

RESULTS: One hundred nineteen patients had serial ECG applied. The median duration of monitoring was 4.2 hours. Forty patients were given a diagnosis of acute coronary syndrome. Chest pain unit protocol detected 52 patients, and 23 were given a diagnosis of acute coronary syndrome (sensitivity 58%; specificity 63%). Sixteen patients had ST-segment changes of greater than 100 microV or greater than 200 microV, and 9 were given a diagnosis of acute coronary syndrome. The addition of the serial ECG to the chest pain unit protocol increased the sensitivity to 65% and decreased the specificity to 58%. Two patients with ST-segment changes but none without ST-segment changes had an adverse cardiac event, yielding a sensitivity of 100% and a specificity of 88%.

CONCLUSION: Serial ECG is of limited value in the diagnostic evaluation of intermediate-risk patients managed in the chest pain unit with a standard protocol. However, when ST-segment changes are present, they indicate an increased likelihood for an adverse cardiac event.