title: Treatment and outcomes of left bundle-branch block patients with myocardial infarction who present without chest pain. National Registry of Myocardial Infarction 2 Investigators.
abstract: OBJECTIVE
  We sought to determine the importance of chest pain on presentation as a predictor of in-hospital treatment and mortality in myocardial infarction (MI) patients with left bundle-branch block (LBBB).
  
  
  BACKGROUND
  Left bundle-branch block patients have a high mortality after MI but are unlikely to receive reperfusion therapy despite evidence from clinical trials demonstrating the efficacy of thrombolytic therapy. Nearly half of MI patients with LBBB present without chest pain.
  
  
  METHODS
  We studied the clinical features, treatment and in-hospital survival of 29,585 patients with LBBB enrolled in the National Registry of MI 2 June 1994 through March 1998). Multivariate logistic regression was used to assess the independent effect of chest pain on reperfusion decisions and in-hospital mortality.
  
  
  RESULTS
  Left bundle-branch block patients with chest pain were greater than five-fold more likely to receive reperfusion therapy (13.6% vs. 2.6%) than LBBB patients without chest pain; they were also more likely to receive aspirin, beta-adrenergic blocking agents, heparin and nitrates (all p < 0.0001). Unadjusted in-hospital mortality was 18% in patients with chest pain and 27% in patients without chest pain. Adjusting for patient characteristics reduced the odds ratio associated with the absence of chest pain from 1.47 (95% confidence interval: 1.41 to 1.54) to 1.21 (95% confidence interval: 1.12 to 1.30). The remainder of the mortality difference was caused by the undertreatment of patients without chest pain, particularly the low utilization of aspirin and beta-blockers.
  
  
  CONCLUSIONS
  Left bundle-branch block patients with MI who present without chest pain are less likely to receive optimal therapy and are at increased risk of death. Prompt recognition and treatment of this high-risk subgroup should improve survival.
authors.affiliation: General Internal Medicine Section, San Francisco VA Medical Center, California 94121, USA. shlip@itsa.ucsf.edu
authors.forename: M G
authors.initials: MG
authors.lastname: Shlipak
authors.forename: A S
authors.initials: AS
authors.lastname: Go
authors.forename: P D
authors.initials: PD
authors.lastname: Frederick
authors.forename: J
authors.initials: J
authors.lastname: Malmgren
authors.forename: H V
authors.initials: HV
authors.lastname: Barron
authors.forename: J G
authors.initials: JG
authors.lastname: Canto
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000150:complications* / Q000401:mortality / Q000628:therapy*; D002637:Chest Pain / Q000150:complications; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D009203:Myocardial Infarction / Q000150:complications* / Q000401:mortality; D011379:Prognosis; D011446:Prospective Studies; D012042:Registries; D016896:Treatment Outcome