Coronary Artery Disease
Relative contributions of a single-admission 12-lead electrocardiogram and early 24-hour continuous electrocardiographic monitoring for early risk stratification in patients with unstable coronary artery disease☆

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Abstract

Patients with unstable coronary syndromes are a heterogeneous group with varying degrees of ischemia and prognosis. The present study compares the prognostic value of a standard electrocardiogram (ECG) obtained at admission to the hospital with the information from 24-hour continuous electrocardiographic monitoring obtained immediately after admission. The admission ECGs and 24 hours of vectorcardiographic (VCG) monitoring from 308 patients admitted with unstable coronary artery disease were analyzed centrally regarding standard electrocardiographic ST-T changes, ST-vector magnitude (ST-VM), and ST change vector magnitude episodes. End points were death, acute myocardial infarction, and refractory angina pectoris within a 30-day follow-up period. ST-VM episodes (≥50 μV for ≥1 minute) during VCG monitoring was the only independent predictor of death or acute myocardial infarction by multivariate analysis. ST-VM episodes during vectorcardiography was associated with a relative risk of 12.7 for having a cardiac event, hypertension was associated with a relative risk of 1.7, and ST depression on the admission ECG was associated with a relative risk of 5.7. Patients with ST depression at admission had an event rate (death or acute myocardial infarction) of 17% at 30-day follow-up. Patients without ST depression could further be risk stratified by 24 hours of VCG monitoring into a subgroup with ST-VM episodes at similar (8%) risk and a subgroup without ST-VM episodes at low (1%) risk (p = 0.00005). Continuous VCG monitoring provides important information for evaluating patients with unstable coronary artery disease. It is recommended that patients not initially estimated at high risk based on the admission ECG are referred for 24 hours of VCG monitoring for further risk stratification.

Section snippets

Patients

The Thrombin Inhibition in Myocardial infarction (TRIM) study randomized patients with unstable angina /non–Q-wave myocardial infarction to 4 different treatment regimens of either 72 hours of conventional heparin infusion or a study drug. Acute myocardial ischemia was defined as new onset (<24 hours) of characteristic ischemic chest pain or a worsening of a previously stable effort angina or onset of angina at rest. This clinical diagnosis had to be supported by at least 1 of the following

Baseline characteristics

Table Idepicts baseline characteristics of the study population.

Electrocardiographic results

Of the 308 patients, 73 (24%) had ST-segment elevation on the admission ECG, 35 patients (11%) had ST-segment depression, 157 (51%) had inverted T waves, and in 98 (32%) the ECG was normal on admission. Five patients (2%) had both ST elevation and ST depression, 21 (7%) had ST depression in combination with T-wave inversion, and 41 (13%) had both ST elevation and inverted T waves. Eight patients (3%) had nonevaluable ECGs owing to

Discussion

Patients with unstable coronary artery disease lie in the broad spectrum between stable angina pectoris and acute transmural myocardial infarction. The extent of ischemia and the short- and long-term prognosis are quite variable in this population. The therapeutic implications of risk stratifying patients with unstable coronary artery disease are clear. Patients at very low risk can avoid a prolonged hospital stay, and the more aggressive treatment approaches can be concentrated on patients at

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    ☆

    This study was supported by grants from The Beckett Foundation, Copenhagen, Denmark; “Asta Floridan Boldings Mindelegat,” Copenhagen, Denmark; and the “Murermester Laurits Peter Christensen og hustru Kirsten Sigrid Christensens fond,” Hillerod, Denmark. Statistical support was financed through a grant from the Danish Medical Research Council. The TRIM study was planned and funded by ASTRA, ASTRA/Hässle AB, Molndal, Sweden.

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