title: Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial.
abstract: OBJECTIVE
  Bundle branch block (BBB) early during acute myocardial infarction (AMI) is often considered high risk for mortality. Little is known about how different BBB types influence prognosis.
  
  
  RESULTS
  The HERO-2 trial recruited 17 073 patients with ischaemic symptoms lasting >30 min and either ST elevation with or without right bundle branch block (RBBB) or presumed-new left bundle branch block (LBBB). Electrocardiograms were performed before and 60 min after the start of fibrinolytic therapy. Using patients with normal intraventricular conduction as a reference, odds ratios (ORs) for 30-day mortality were calculated for different BBB types (LBBB, RBBB with anterior AMI, and RBBB with inferior AMI) present at randomization and/or 60 min, with adjustment for recruitment region, pre-infarction characteristics, time to randomization, hemodynamics, and Killip class. At randomization, the 873 patients (5.11%) with BBB had worse baseline characteristics than patients without BBB. In patients presenting with LBBB (n=300), the ORs for 30-day mortality were 1.90 (95% CI 1.39-2.59) before and 0.68 (0.48-0.99) after adjustment for other prognosticators. In patients presenting with RBBB (n=415) and anterior AMI, the ORs were 3.52 (2.82-4.38) before and 2.48 (1.93-3.19) after adjustment. In patients presenting with RBBB and inferior AMI (n=158), the ORs were 1.74 (1.06-2.86) before and 1.22 (0.71-2.08) after adjustment. Within 60 min, 143 patients (0.92%) developed new BBB. The adjusted ORs for 30-day mortality were 2.97 (1.16-7.57) in the 25 patients with new LBBB, 3.84 (2.38-6.22) in the 100 with new RBBB and anterior AMI, and 2.23 (0.54-9.21) in the 18 with new RBBB and inferior AMI.
  
  
  CONCLUSIONS
  RBBB accompanying anterior AMI at presentation and new BBB (including LBBB) early after fibrinolytic therapy are independent predictors of high 30-day mortality. These electrocardiographic features should be considered in risk stratification to identify high-risk patients.
authors.affiliation: Cardiovascular Research Unit, Green Lane Cardiovascular Service, Auckland City Hospital, Private Bag 92024, Auckland 1030, New Zealand.
authors.forename: Cheuk-Kit
authors.initials: CK
authors.lastname: Wong
authors.forename: Ralph A H
authors.initials: RA
authors.lastname: Stewart
authors.forename: Wanzhen
authors.initials: W
authors.lastname: Gao
authors.forename: John K
authors.initials: JK
authors.lastname: French
authors.forename: Christopher
authors.initials: C
authors.lastname: Raffel
authors.forename: Harvey D
authors.initials: HD
authors.lastname: White
mesh_terms: D000368:Aged; D021721:Balloon Occlusion / Q000379:methods; D002037:Bundle-Branch Block / Q000150:complications* / Q000401:mortality / Q000628:therapy; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000401:mortality / Q000628:therapy; D015425:Myocardial Reperfusion / Q000379:methods; D011379:Prognosis; D012307:Risk Factors; D015912:Thrombolytic Therapy / Q000379:methods
chemical_list: D005343:Fibrinolytic Agents