QRS prolongation in patients with acute coronary syndromes Fahad Baslaib, MD, a Salem Alkaabi, MD, a Andrew T. Yan, MD, a,b Raymond T. Yan, MD, a,b Paul Dorian, MD, a Kumaraswamy Nanthakumar, MD, c Amparo Casanova, MD, PhD, b and Shaun G. Goodman, MD, MSc a,b for the Canadian Acute Coronary Syndrome Registry Investigators d Toronto, Canada Background QRS prolongation with or without bundle branch block (BBB) has been associated with adverse outcome in myocardial infarction; we examined the relationship between QRS duration and outcome in a broad spectrum of patients with acute coronary syndrome (ACS). Method and Results Core laboratory evaluation of the presenting electrocardiogram in Canadian ACS Registry patients (n = 5,003) showed 4,289 (85.7%) had QRS <120 milliseconds, 202 (4.0%) patients had QRS ≥120 milliseconds without BBB, 262 (5.2%) had left BBB (LBBB), and 250 (5.0%) had right BBB. Compared to patients with QRS <120 milliseconds, patients with QRS ≥120 milliseconds without BBB had higher in-hospital (3.5% vs 1.9%, odds ratio [OR] 1.87, 95% CI 0.85-4.09, P = .12) and 1-year mortality (14.9% vs 7.7%, OR 2.10, 95% CI 1.38-3.18, P = .001). In-hospital and 1-year mortality was significantly higher in patients with BBB (eg, LBBB compared with QRS <120 milliseconds) (5.0% vs 1.9%, OR 2.71, 95% CI 1.49-4.94, P = .001, and 23.8% vs 7.7%, OR 3.74, 95% CI 2.72-5.13, P < .001). Analyzed as a continuous variable and after adjustment for validated prognosticators, QRS duration was an independent predictor of 1-year death (OR 1.11, 95% CI 1.06-1.16, P < .001) and death/myocardial infarction (OR 1.06, 95% CI 1.02-1.11, P = .003). However, when using clinically applicable QRS duration evaluation, only LBBB was an independent predictor of 1-year mortality (OR 1.93, 95% CI 1.28-2.90, P = .002). Conclusions In patients presenting with a broad spectrum of suspected ACS, QRS prolongation—particularly in the setting of LBBB—is an independent predictor of in-hospital and 1-year mortality. (Am Heart J 2010;159:593-8.) The electrocardiogram (ECG) is an important diagnostic and prognostic tool in acute myocardial infarction (MI). 1 Even in the era of reperfusion therapy, distinct QRS prolongation with or without right or left bundle branch block (BBB) predicts an adverse outcome. 1-14 Patients with QRS prolongation without BBB (“periinfarction block” 9 ) appear to have more severe coronary artery disease, 8 and subsequent mortality rates have been described as similar 8 or higher when compared to those with normal conduc- tion. 9 However, these findings are derived from studies performed in selected patients with ST-segment elevation MI (STEMI). 7-14 The prognostic significance of increased QRS duration in patients with non–ST-segment elevation acute coronary syndromes (ACS; including non-ST- segment elevation MI [NSTEMI] and unstable angina [UA]) has been described in only 2 modest-sized, single- center studies. 15,16 Thus, the aim of our study is to examine the relationship between QRS duration and clinical outcome in a broad spectrum of patients with ACS, including those with STEMI, NSTEMI, and UA. Methods Study population Details of the Canadian ACS Registry have been previously published. 17 Briefly, patients were eligible if (1) they were ≥18 years old on presentation, (2) they were admitted to hospital with a suspected ACS (defined by symptoms consistent with acute cardiac ischemia within 24 hours of onset), and (3) the qualifying ACS was not precipitated by a significant concurrent event. There were no other specific exclusion criteria, and consecutive patient enrolment was encouraged at all sites. A total of 51 academic and community hospitals in 9 provinces across Canada participated in this registry. At each site, the designated physician or study coordinator recorded patient demographic and clinical data, relevant laboratory results, in-hospital treatment, outcome, and discharge diagnosis and medications on standardized case report forms, which were From the a Division of Cardiology, St Michael's Hospital, University of Toronto, Toronto, Canada, b Canadian Heart Research Centre, Toronto, Canada, and c University Health Network—Toronto General Hospital, University of Toronto, Toronto, Canada. d A list of participating Canadian ACS Registry Investigators and Coordinators may be found in Arch Intern Med 2007;167:1009-1016. Submitted October 20, 2009; accepted January 14, 2010. Reprint requests: Shaun G. Goodman, St Michael's Hospital, Division of Cardiology, 30 Bond Street, Room 6-034 Queen, Toronto, Ontario, Canada M5B 1W8. E-mail: goodmans@smh.toronto.on.ca 0002-8703/$ - see front matter © 2010, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2010.01.007