Clinical implications of a next-day follow-up electrocardiogram in patients with non-ST elevation acute coronary syndromes Salem Alkaabi, MD, a,b Fahad Baslaib, MD, a,b Amparo Casanova, MD, PhD, b Andrew T. Yan, MD, a,b David Fitchett, MD, a,b Aurora Mendelsohn, PhD, b Jano Y. Nikhil, MD, a,b Anatoly Langer, MD, MSc, a,b and Shaun G. Goodman, MD, MSc a,b on behalf of the Canadian Acute Coronary Syndrome Registry Investigators c Toronto, Ontario, Canada Background The prognostic value of admission ST-segment changes in patients with non-ST elevation acute coronary syndromes (NSTE ACS) is well established; however, the value of a next-day follow-up electrocardiogram (ECG) is unclear. Method We evaluated ST-depression (ST↓) and Q-wave status on the admission and 24 to 36-hour follow-up ECG in 2,743 patients in a prospective Canadian ACS registry. Results Of patients with ST↓ ≥1 mm on admission (n = 533 [19.4%]), 366 (68.7%) normalized their ST segment on follow-up ECG. Among patients without ST↓ on admission (n = 2,110), 97 (4.4%) developed new ST↓ at follow-up. Patients with normalized ST↓ at follow-up had higher 1-year myocardial infarction (MI) (10.1% vs 5.7%, odds ratio [OR] 1.77, 95% CI 1.12-2.81, P = .015) and death/MI rates (19.5% vs 10.2%, OR 1.69, 95% CI 1.18-2.41, P = .004), respectively, as compared to those who never had ST↓. Patients with persistent ST↓ had higher 1-year MI (10.8% vs 5.7%, OR 1.95, 95% CI 1.09-3.51, P = .025) and death/MI rates (25.6% vs 10.2%, OR 1.78, 95% CI 1.13-2.79, P = .013), respectively. In multivariable analysis, ST↓ on baseline ECG was an independent predictor of 1-year mortality; however, ST↓ on the follow-up ECG did not provide additional prognostic value. There were no differences in outcomes between the 4 different Q-wave status groups. Conclusions Although dynamic and persistent ST↓ are associated with worse unadjusted outcome in patients with NSTE ACS, there was no incremental prognostic value of a follow-up ECG evaluating ST depression and/or Q-wave status beyond that already provided by the initial ECG together with established prognostic factors. (Am Heart J 2008;156:797-803.) The electrocardiogram (ECG), a critical component of the early assessment and risk stratification of patients presenting with acute coronary syndromes (ACS), con- tains valuable diagnostic and prognostic information. Previous studies have demonstrated that the admission ECG provides immediate and independent prognostic information; for example, ST-segment depression on the admission ECG has been associated with poor early and long-term outcomes. 1-8 In addition, many studies have found that the presence of Q waves after acute myocardial infarction (MI) is associated with higher inhospital morbidity and mortality. 9-12 However, less is known about the prognostic significance of the next-day follow-up ECG in the current era, including the use of combining this with the admission ECG in predicting short-term and long-term outcomes in patients with non- ST elevation (NSTE) ACS. Although a recent substudy in approximately 900 patients with NSTE ACS suggested that evolutionary ST-segment changes on the admission and predischarge ECG occur in up to 40% of patients and are associated with clinical outcome, 13 these findings have not been confirmed in a nonclinical trial setting. Accordingly, the objectives of this study were to assess the (1) frequency of ST-segment depression on the admission and next-day follow-up ECG; (2) prognostic value of dynamic ST changes on the follow-up ECG relative to those ST changes at admission; (3) frequency of Q waves on the admission and follow-up ECG; and (4) prognostic value of Q-wave changes on the follow-up ECG relative to those Q waves at admission in patients with NSTE ACS. We hypothesized that ST-segment changes and new Q waves on the follow-up ECG From the a Terrence Donnelly Heart Centre, Division of Cardiology, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada, and b Canadian Heart Research Center, Toronto, Ontario, Canada. This research was sponsored by the Canadian Heart Research Center and Key Pharmaceuticals (Montreal, Quebec, Canada), Division of Schering Canada Inc. c A list of participating Canadian ACS Registry Investigators and Coordinators may be found in the Arch Intern Med 2007;167:1009-1016. Submitted January 24, 2008; accepted June 10, 2008. Reprint requests: Dr Shaun G. Goodman, MD, MSc, St Michael's Hospital, Division of Cardiology, 30 Bond St, Room 6-034 Queen, Toronto, Ontario, Canada M5B 1W8. E-mail: goodmans@smh.toronto.on.ca 0002-8703/$ - see front matter © 2008, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2008.06.014