Complete bundle branch block as an independent predictor of all-cause mortality: Report of 7,073 patients referred for nuclear exercise testing

PURPOSE: Complete left bundle branch block is a well-established independent risk factor for mortality, but. the prognostic importance of right bundle branch block is unclear. We determined whether left and right bundle branch block was associated with all-cause mortality risk after adjustment for potential confounders, including clinical, exercise, and nuclear scintigraphic variables. SUBJECTS AND METHODS: We studied 7,073 adults who were referred for symptom-limited nuclear exercise testing. Patient s with heart failure or pacemakers were excluded. The presence or absence of bundle bundle branch block was determined from resting electrocardiograms. The main outcome measure was all-cause mortality during a mean of 6.7 years of follow-up. RESULTS: One hundred ninety patients (3%) had complete right bundle branch block, and 150 (2%) had complete left bundle branch block. There were 825 deaths (12%). Mortality was greater in patients with complete right bundle branch block (24% [46 of 190]) or left bundle branch block (24% [36 of 150]) than in those without these findings (11% [779 of 6,883 and 789 of 6,923, respectively]; both P < 0.0001). After adjustment for potential confounders, right bundle branch block was as strong an independent predictor of mortality (hazard ratio [HR] 1.5; 95% confidence interval [CI]: 1.1 to 2.1; P = 0.007) as left bundle branch block (HR 1.5; 95% CI: 1.0 to 2.0; P = 0.017). Incomplete right bundle branch block was not associated with mortality. CONCLUSION: Complete right and left bundle branch block are independent predictors of all-cause mortality risk even after adjustment for exercise capacity, nuclear perfusion defects, and other risk factors.