Exercise-Induced Left Bundle Branch Block: Prevalence and Prognosis

Background: Exercise-induced left bundle branch block (EI-LBBB) is an infrequent finding. Its prevalence and prognostic significance are not clear. Objective: To evaluate, in a longitudinal study, the prevalence and prognostic significance of EI-LBBB in American war veterans. Methods: We evaluated 9,623 patients submitted to an exercise test (ET) in treadmill between 1987 and 2007. The outcomes were compared between those with normal TE, the ones with EI-LBBB and the ones with down-sloping ST-segment. Mortality and causes of death were identified while blinded to the ET results. Results: In this prospective cohort, 6,922 individuals had normal ET results (57.2 +/- 11.4 years), 1,739 had abnormal ST-segment depression (62.7 +/- 9.8 years), and 38 had EI-LBBB (65.2 +/- 11.9 years). The prevalence of EI-LBBB was 0.38%. After 8.8 years, there were 1,699 deaths due to all-cause mortality and 610 cardiovascular (CV) deaths; coronary artery disease and heart failure were more prevalent in patients with EI-LBBB. Patients with EI-BCRE had a hazard ratio of 2.37 (p = 0.002) for all-cause mortality, but it was not significant when adjusted for age or when the CV death was the assessed outcome. Conclusion: EI-LBBB is a rare clinical finding. Individuals with BCRE-EI have higher all-cause mortality when compared to those with normal ET results. However, this fact is explained by the fact that these patients are significantly older and have more associated cardiovascular diseases. (Arq Bras Cardiol. 2011; [online].ahead print, PP.0-0)