Myocardial infarction: bundle-branch block worsened prognosis

Clinical bottom line (level 2b)

  1. One in seven patients with a myocardial infarction died in hospital.
  2. Patients were at increased risk of dying if they had any of the following on their admission 12-lead ECG
    • right bundle-branch block
    • ST elevation without bundle-branch block
    • left bundle-branch block
  3. There was no clear difference in in-hospital mortality between patients with right or left bundle branch block.
Go et al: Annals of Internal Medicine 1998; 129 (9): 690-697
Expires March 2003

The study

Retrospective cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: 1571 hospitals in 50 states, USA

297832 patients (aged mean 72 years, 58% male) confirmed acute myocardial infarction, defined on the basis of typical symptoms and signs plus
  • total creatine kinase level or CK-MB fraction at least twice the upper limit of normal
  • ECG evidence
  • other enzymatic, scintigraphic, echocardiographic or autopsy evidence
  • principal discharge diagnosis of myocardial infarction if none of the above were available


Excluded if
  • <18 years old
  • transfer to or out of participating hospital



    • Factors studied:
  • age, sex, race, cardiovascular history, known cardiac risk factors, chest pain on admission, clinical features on admission, 12-lead ECG on admission, therapies used
  • right bundle branch block
  • ST elevation without bundle-branch block
  • left bundle-branch block
  • left bundle branch block


    • Thrombolytic therapy was given where necessary

    Logistic regression analysis performed on prognostic factors.

    ?100% followed for length of hospital stay
    Outcomes studied:
  • in-hospital mortality
  • in-hospital mortality (RBBB)
  • in-hospital mortality (LBBB)

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    in-hospital mortality length of hospital stay 42730/297832 14.4%
    (14.2% to 14.5%)
    in-hospital mortality (RBBB) length of hospital stay 4221/14133 23.0%
    (22% to 24%)
    in-hospital mortality (LBBB) length of hospital stay 4512/15455 22.6%
    (22% to 23%)

    prognostic factor for
    in-hospital mortality     		time to outcome control rate (%) adjusted OR
    (95% CI)    		 NNF+
    (95% CI)
    right bundle branch block ? 33996/259511
    (13.1%)     		1.64
    (1.57 to 1.71)     		15
    (14 to 17)
    ST elevation without bundle-branch block ? 33996/259511
    (13.1%)     		1.53
    (1.49 to 1.58)     		18
    (16 to 19)
    left bundle-branch block ? 33996/259511
    (13.1%)     		1.34
    (1.28 to 1.39)     		27
    (24 to 33)

    prognostic factor for
    in-hospital mortality (LBBB)     		time to outcome adjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    left bundle branch block length of hospital stay 1.76
    (1.68 to 1.77)     		11
    (10 to 11)

    • 6.2% of patients had RBBB and 6.7% had LBBB.

    Comments

    1. The study is too small to show any clear difference in mortality between patients with right of left bundle branch block.

    Citation

    1. Go AS, Barron HV, Rundle AC, et al: Bundle-branch block and in-hospital mortality in acute myocardial infarction. Annals of Internal Medicine 1998; 129 (9): 690-697
    Contributor: Clare Wotton and Chris Ball, October 1999
    Reviewer:

    Clinical Question.
    Patient acute myocardial infarction
    Intervention or Exposure bundle branch block
    Outcome in-hospital mortality