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(Circulation. 2004;110:1896-1902.)
© 2004 American Heart Association, Inc.

Coronary Heart Disease

Comorbidity and Myocardial Dysfunction Are the Main Explanations for the Higher 1-Year Mortality in Acute Myocardial Infarction With Left Bundle-Branch Block

Ulf Stenestrand, MD, PhD; Fariborz Tabrizi, MD; Johan Lindbäck, MSc; Anders Englund, MD, PhD; Mårten Rosenqvist, MD, PhD; Lars Wallentin, MD, PhD

From the Department of Cardiology, University Hospital of Linköping, Linköping (U.S.); Department of Cardiology, South Hospital, Stockholm (F.T., M.R.); Uppsala Clinical Research Center, Uppsala University, Uppsala (J.L., L.W.); and Department of Cardiology, Örebro University Hospital, Örebro (A.E.), Sweden.

Correspondence to Ulf Stenestrand, MD, PhD, Department of Cardiology, University Hospital, SE 581 85 Linköping, Sweden. E-mail stenestrand{at}riks-hia.se

Received March 23, 2004; de novo received June 1, 2004; revision received June 15, 2004; accepted June 21, 2004.

Background— The purpose of this study was to assess the independent contribution of left bundle-branch block (LBBB) on cause-specific 1-year mortality in a large cohort with acute myocardial infarction (MI).

Methods and Results— We studied a prospective cohort of 88 026 cases of MI from the Register of Information and Knowledge about Swedish Heart Intensive care Admissions in 72 hospitals in 1995 to 2001. Long-term mortality was calculated by Cox regression analysis, adjusted for multiple covariates that affect mortality by calculation of a propensity score. LBBB was present in 9% (8041 of 88 026) of the MI admissions. Patients with LBBB were older and had a higher prevalence of comorbid conditions than patients with no LBBB. The unadjusted relative risk of death within 1 year was 2.16 (95% CI, 2.08 to 2.24; P<0.001) for LBBB (42%, 3350 of 8041) compared with those with no LBBB (22%, 17 044 of 79 011). After adjustment for a propensity score that takes into account differences in risk factors and acute intervention, LBBB was associated with a relative risk of death of 1.19 (95% CI, 1.14 to 1.24; P<0.001). In a subgroup of 11 812 patients for whom left ventricular ejection fraction was available and could be added to the analysis, the contributing relative risk of LBBB for death was only 1.08 (95% CI, 0.93 to 1.25; P=0.33). The most common cause of death in both groups was ischemic heart disease.

Conclusions— MI patients with LBBB have more comorbid conditions and an increased unadjusted 1-year mortality. When adjusted for age, baseline characteristics, concomitant diseases, and left ventricular ejection fraction, LBBB does not appear to be an important independent predictor of 1-year mortality in MI.

Key Words: bundle-branch block • mortality • myocardial infarction • patients • prognosis

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