title: Incidence and clinical relevance of the occurrence of bundle-branch block in patients treated with thrombolytic therapy.
abstract: BACKGROUND
  Whether thrombolytic therapy alters the incidence and clinical outcome of bundle-branch block is unclear.
  
  
  RESULTS
  We examined the occurrence of new-onset bundle-branch block, both transient and persistent, in 681 patients with acute myocardial infarction enrolled in the Thrombolysis and Angioplasty in Myocardial Infarction 9 and Global Utilization of Streptokinase and t-PA for Occluded Arteries 1 protocols. Each patient underwent continuous 12-lead ECG monitoring for 36 to 72 hours with the Mortara ST monitoring system. Bundle-branch block was characterized as right, left, alternating, transient, or persistent. The overall incidence of bundle-branch block was 23.6% (n = 161), with transient block in 18.4% (n = 125) and persistent block in 5.3% (n = 36). Right bundle-branch block was found in 13% (n = 89) of the population; left bundle-branch block was found in 7% (n = 48). Alternating bundle-branch block was seen in 3.5% (n = 24) of patients. Left anterior descending artery infarcts accounted for most bundles (54%, n = 79). Patients with bundle-branch block had lower ejection fractions, higher peak creatine phosphokinase levels (P < .0001), and more diseased vessels (P < .019). Mortality rates in patients with and without bundle-branch block were 8.7% and 3.5%, respectively (P < .007). A higher mortality rate was observed in the presence of persistent (19.4%) versus transient (5.6%) or no (3.5%) bundle-branch block (P < .001).
  
  
  CONCLUSIONS
  Thrombolytic therapy reduces the overall mortality rate associated with persistent bundle-branch block. However, persistent bundle-branch block remains predictive of a higher mortality rate than either transient or no bundle-branch block. Continuous 12-lead ECG monitoring provides an accurate characterization of the incidence and type of conduction disturbances after acute myocardial infarction.
authors.affiliation: Duke University/VA Medical Center, Durham, NC, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Newby
authors.forename: E
authors.initials: E
authors.lastname: Pisanó
authors.forename: M W
authors.initials: MW
authors.lastname: Krucoff
authors.forename: C
authors.initials: C
authors.lastname: Green
authors.forename: A
authors.initials: A
authors.lastname: Natale
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000150:complications* / Q000453:epidemiology* / Q000401:mortality; D015716:Electrocardiography, Ambulatory; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000188:drug therapy* / Q000503:physiopathology; D015912:Thrombolytic Therapy