Usefulness of Automated Serial 12-Lead ECG Monitoring During the Initial Emergency Department Evaluation of Patients With Chest Pain

Abstract

Study objective: To determine whether the use of automated serial 12-lead ECG monitoring (SECG) is more sensitive and specific than the initial 12-lead ECG in the detection of injury and ischemia in patients with acute coronary syndromes (ACS) during the initial ED evaluation of patients with chest pain. Methods: A prospective observational study was performed in 1,000 patients with chest pain who were admitted to a university teaching hospital and who underwent continuous ST-segment monitoring with SECG during the initial ED evaluation. The initial ECG was obtained on presentation, and SECG readings were obtained at least every 20 minutes during the ED evaluation. Diagnostic abnormalities on the initial ECG were defined as injury or ischemia. Diagnostic changes on SECG were defined as evolving injury, evolving ischemia, new injury, or new ischemia. ACS was defined as acute myocardial infarction (AMI), recent myocardial infarction, or unstable angina. Results: A diagnostic SECG was more sensitive than a diagnostic initial ECG for detection of AMI (68.1% versus 55.4%; P<.0001) and ACS (34.2% versus 27.5%; P<.0001). A diagnostic SECG was more specific than a diagnostic initial ECG for detection of ACS (99.4% versus 97.1%; P<.01). SECG detected injury in an additional 16.2% of AMI patients compared with the initial ECG (61.8% versus 45.6%; P<.0001; 95% confidence interval for difference of proportions, 10.9% to 21.4%). Conclusion: SECG during the initial ED evaluation is more sensitive and more specific than the initial ECG in the identification of ACS. Patients with a diagnostic SECG need intensive antiischemic therapy, evaluation for reperfusion therapy, and admission to an ICU. [Fesmire FM, Percy RF, Bardoner JB, Wharton DR, Calhoun FB: Usefulness of automated serial 12-lead ECG monitoring during the initial emergency department evaluation of patients with chest pain. Ann Emerg Med January 1998;31:3-11.]

Introduction

The identification of acute injury and ischemia on the ECG during initial ED evaluation is of paramount importance in determining optimal treatment and disposition for patients with acute coronary syndromes (ACS), defined as acute myocardial infarction (AMI), recent myocardial infarction (MI), or unstable angina. Patients with acute injury revealed by ECG receive the maximum benefit from emergency reperfusion therapy.1, 2 Patients with acute ischemia on the ECG are at higher risk for AMI and life-threatening complications and deserve intensive evaluation and management.3, 4, 5, 6, 7, 8

The initial ECG is diagnostic of acute injury or ischemia in approximately 40% to 65% of patients with AMI.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 There currently is no reliable information regarding the percentage of patients with unstable angina who have an ECG diagnostic of injury or ischemia, although Lee et al¹³ reported that 11 (7.7%) of 143 patients with unstable angina had an ECG interpretation of “probable MI.” Because the initial ECG consists of only 10 seconds of monitoring and ST-segment instability is characteristic of AMI and unstable angina,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 the majority of patients with ACS do not manifest a diagnostic ECG on initial presentation. To overcome the limitations of a single initial ECG, continuous 12-lead ST-segment monitoring with frequent automated serial ECGs (SECG) has been used to assist in the evaluation and management of patients with chest pain and AMI.31, 32, 33, 34, 35, 36, 37, 38, 39 Although case reports indicate that SECG may be more sensitive than the initial ECG for detection of acute injury in the presence of AMI during the initial ED evaluation,33, 34, 36, 37 no studies have investigated the sensitivity and specificity of SECG versus initial ECG for detection of injury or ischemia in patients with ACS and AMI.

In this study, we assessed the usefulness of SECG compared with the initial ECG for identification of acute injury or ischemia during the initial ED evaluation. Also, we investigated the usefulness of SECG for risk stratification for predicting ACS, AMI, in-hospital interventions, and life-threatening complications; this was done by comparing the diagnostic changes (evolving injury, evolving ischemia, new injury, or new ischemia), nondiagnostic changes (new bundle branch block [BBB], normalization of T waves, nondiagnostic T wave inversions, or nondiagnostic ST segment deviations of 1 mm or more), and no changes for predicting these outcomes.