title: Risk stratification of patients with acute anterior myocardial infarction and right bundle-branch block: importance of QRS duration and early ST-segment resolution after fibrinolytic therapy.
abstract: BACKGROUND
  Patients with an acute anterior ST-segment elevation myocardial infarction and right bundle-branch block (RBBB) have a high mortality risk, which may be stratified by early ECG changes.
  
  
  RESULTS
  In the Hirulog Early Reperfusion Occlusion (HERO-2) trial, 17 073 patients with acute myocardial infarction (AMI) within 6 hours of symptom onset were treated with streptokinase and randomized to receive bivalirudin or heparin. There was no difference in the primary end point of 30-day mortality. ECGs were recorded at randomization and 60 minutes after fibrinolytic therapy was begun. The 30-day mortality rate was 31.6% in the 415 patients with RBBB and anterior AMI at randomization and 33% in the 100 patients who developed new RBBB at 60 minutes from normal baseline conduction accompanying an anterior AMI. An increase in QRS duration by 20-ms increments was associated with increasing 30-day mortality rate in both RBBB groups on multivariable analyses with covariates of age, Killip class, systolic blood pressure, pulse, and prior infarction. Patients with QRS duration > or = 160 ms had higher 30-day mortality rate than those with QRS duration < 160 ms (37.2% versus 27.2%, P = 0.03, and 46.2% versus 24.5%, P = 0.025, in the 2 groups, respectively). For the patients with RBBB and anterior MI at randomization, RBBB resolved at 60 minutes in 40 patients, but 30-day mortality rate was unchanged. For those with persisting RBBB at 60 minutes, 30-day mortality rate was lower if ST-segment elevation had resolved by > or = 50% (20.4% versus 35.3%, P = 0.006).
  
  
  CONCLUSIONS
  In patients with anterior AMI and RBBB, increasing QRS duration is associated with increasing 30-day mortality. Early ST-segment resolution after fibrinolytic therapy despite persisting RBBB is associated with lower mortality rate.
authors.affiliation: Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Cheuk-Kit
authors.initials: CK
authors.lastname: Wong
authors.forename: Wanzhen
authors.initials: W
authors.lastname: Gao
authors.forename: Ralph A H
authors.initials: RA
authors.lastname: Stewart
authors.forename: Niels
authors.initials: N
authors.lastname: van Pelt
authors.forename: John K
authors.initials: JK
authors.lastname: French
authors.forename: Philip E G
authors.initials: PE
authors.lastname: Aylward
authors.forename: Harvey D
authors.initials: HD
authors.lastname: White
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D002037:Bundle-Branch Block / Q000150:complications*; D002318:Cardiovascular Diseases / Q000453:epidemiology; D004562:Electrocardiography; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D007839:Functional Laterality; D006629:Hirudins; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology*; D010446:Peptide Fragments / Q000627:therapeutic use*; D016032:Randomized Controlled Trials as Topic; D011994:Recombinant Proteins / Q000627:therapeutic use; D018570:Risk Assessment; D013300:Streptokinase / Q000627:therapeutic use*; D016019:Survival Analysis
chemical_list: D000925:Anticoagulants; D005343:Fibrinolytic Agents; D006629:Hirudins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013300:Streptokinase; C074619:bivalirudin