The aim of this study was to investigate the prognosis associated with bundle branch block (BBB) depending on location, time of appearance, and duration in patients with myocardial infarction (MI). From January 1998 to January 2008, we recruited 5,570 patients with acute MI. Thirty-day and 7-year all-cause mortality, according to BBB location, time of appearance, and duration were analyzed by multivariable analyses. BBB was present in 964 patients (17.3%); right BBB (RBBB) 10.6% and left BBB (LBBB) 6.7%. Overall mortality rate at 30 days was 13.2% (n = 738) and 7 years was 6.34 deaths per 100 patient-year. Both RBBB and LBBB were more frequently previous, 42.9% and 58.8%. Compared with non-BBB, all BBB groups showed higher prevalence of co-morbidities, especially rates of diabetes (49.0% vs 34.3%, p <0.001) and more often heart failure during hospitalization (54.5% vs 26.6%, p <0.001). Compared with RBBB, patients with LBBB had a higher prevalence of co-morbidities and a higher mortality, especially the new BBB, 30 days: 52.5% versus 31.6% and 7 years (incident rate): 27.2 versus 13.3 per 100 patient-year. New transient BBB had lower heart failure on admission (42.6% vs 58.3%, p = 0.008) and 30-day mortality (20.3% vs 69.6%, p <0.001) compared with permanent in both locations. New permanent RBBB was independently associated with 30-day (hazard ratio [HR] 2.01, 95% confidence interval [CI] 1.45 to 2.79) and 7-year mortality (HR 3.12, 95% CI 2.38 to 4.09). New-permanent LBBB was independently associated with 30-day (HR 2.15, 95% CI 1.47 to 3.15) and 7-year mortality (HR 2.91, 95% CI 2.08 to 4.08). In conclusion, in patients with acute MI, the appearance of a new BBB was independently associated with a higher 30-day and 7-year all-cause mortality.
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