title: Bundle-branch block and in-hospital mortality in acute myocardial infarction. National Registry of Myocardial Infarction 2 Investigators.
abstract: BACKGROUND
  Left bundle-branch block (BBB) is considered an important predictor of poor outcome in patients with acute myocardial infarction, but the consequences of right BBB are not well understood.
  
  
  OBJECTIVE
  To 1) estimate the prevalence of left and right BBB in patients with myocardial infarction; 2) compare the clinical characteristics of and treatments received by patients with left, right, or no BBB; and 3) determine the independent association of left BBB and right BBB with in-hospital death.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Multicenter registry of 1571 U.S. hospitals.
  
  
  METHODS
  297,832 patients with acute myocardial infarction who had left, right, or no BBB on initial electrocardiography.
  
  
  METHODS
  Presence and type of BBB, clinical characteristics of patients, therapies given, and in-hospital death.
  
  
  RESULTS
  Patients with left BBB (n = 19,967; 6.7%) or right BBB (n = 18,354; 6.2%) were older and had more comorbid illness and congestive heart failure than patients with no BBB. Among patients for whom thrombolytic therapy was clearly indicated, fewer patients with left or right BBB (16.6% and 32.0%, respectively) than patients with no BBB (66.5%) received this therapy (P < 0.001). Fewer patients with left or right BBB (60.6% and 67.3%, respectively) than patients with no BBB (75.6%) received aspirin within the first 24 hours (P < 0.001), and fewer patients with left or right BBB (23.9% and 31.8%, respectively) than patients with no BBB (40.4%) received beta-blockers within the first 24 hours (P < 0.001). Unadjusted in-hospital mortality rates were almost twice as high for patients with left or right BBB (22.6% and 23.0%, respectively) as for patients with no BBB (13.1%) (P < 0.001). Compared with no BBB and no ST-segment elevation, left BBB was associated with a 34% increase (odds ratio, 1.34 [95% CI, 1.28 to 1.39]) and right BBB was associated with a 64% increase (odds ratio, 1.64 [CI, 1.57 to 1.71]) in the risk for in-hospital death, after adjustment for potential confounders.
  
  
  CONCLUSIONS
  In patients with acute myocardial infarction, prevalences of right and left BBB are similar. Patients with BBB have more comorbid conditions, are less likely to receive therapy, and have an increased risk for in-hospital death compared with patients with no BBB. Compared with left BBB, right BBB seems to be a stronger independent predictor of in-hospital death.
authors.affiliation: Veterans Affairs Medical Center and University of California, San Francisco, 94121, USA. axg@dor.kaiser.org
authors.forename: A S
authors.initials: AS
authors.lastname: Go
authors.forename: H V
authors.initials: HV
authors.lastname: Barron
authors.forename: A C
authors.initials: AC
authors.lastname: Rundle
authors.forename: J P
authors.initials: JP
authors.lastname: Ornato
authors.forename: A L
authors.initials: AL
authors.lastname: Avins
mesh_terms: D002037:Bundle-Branch Block / Q000150:complications / Q000188:drug therapy / Q000401:mortality*; D002637:Chest Pain / Q000209:etiology; D015331:Cohort Studies; D015897:Comorbidity; D017052:Hospital Mortality; D006801:Humans; D009203:Myocardial Infarction / Q000150:complications / Q000188:drug therapy / Q000401:mortality*; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D013223:Statistics as Topic; D015912:Thrombolytic Therapy