title: QRS prolongation in patients with acute coronary syndromes.
abstract: 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).
  
  
  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 > or =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 > or =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.
authors.affiliation: Division of Cardiology, St Michael's Hospital, University of Toronto, Toronto, Canada.
authors.forename: Fahad
authors.initials: F
authors.lastname: Baslaib
authors.forename: Salem
authors.initials: S
authors.lastname: Alkaabi
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Yan
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Yan
authors.forename: Paul
authors.initials: P
authors.lastname: Dorian
authors.forename: Kumaraswamy
authors.initials: K
authors.lastname: Nanthakumar
authors.forename: Amparo
authors.initials: A
authors.lastname: Casanova
authors.forename: Shaun G
authors.initials: SG
authors.lastname: Goodman
mesh_terms: D054058:Acute Coronary Syndrome / Q000401:mortality*; D000368:Aged; D002037:Bundle-Branch Block / Q000401:mortality*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests