Abstract 1537: Right Bundle Branch Block Induced by Exercise: Rare but Ominous
BACKGROUND: Exercise-induced right bundle branch block (EI-RBBB) is an uncommon event during exercise testing (ET). The prognostic significance of EI-RBBB has not been determined and consistent studies about its prevalence are lacking.
OBJECTIVE: To compare the prevalence and prognostic significance of EI-RBBB in male veterans to those with both normal and abnormal ST depression to exercise testing (EI-ST depression).
METHODS: We evaluated 8406 consecutive male patients who underwent ET from 1987 to 2007 at the Long Beach and Palo Alto Veteran Affairs Medical Centers. Outcomes and demographics were compared between individuals with EI-RBBB, those with EI-ST depression (defined as ≥1.0 mm horizontal or down-sloping ST-segment depression), and those with normal exercise response. Mortality and cause of death were determined using the VA electronic medical record. ANOVA was performed to analyze differences among subjects with EI-RBBB, EI-STdep, and normal ET. Kaplan Meier and age-adjusted Cox regression analyses were utilized for survival analyses.
RESULTS: In this prospective cohort, EI-RBBB, EI-STdep and normal exercise ECG response occurred in 23; 1,466; and 6,917 individuals, respectively. The prevalence of EI-RBBB was 0.27%. Over 9 years follow-up there were 6 deaths in the EI-RRBB subgroup, 3 of which were cardiovascular (CV) deaths. Both coronary artery disease and heart failure were more prevalent in those with EI-RBBB (p=0.01). Annual death rates were 7.3% (CV 1.4%) among EI-RBBB patients, 2.6% (CV 1.2%) among those with exercise-induced ST depression, and 1.8% (CV 0.6%) in those with normal ET (χ2= 98.34; P<0.0001 for all cause mortality and χ2= 80.04; P<0.0001 for CV mortality). Patients with EI-RBBB had an age-adjusted Cox proportional hazard ratio of 1.13 (p= 0.75, 95% CI: 0.5–2.5) for all-cause mortality and 1.6 (p= 0.43, 95% CI: 0.5–5.0) for cardiovascular mortality.
CONCLUSIONS: Exercise-induced right bundle branch block is a rare occurrence during routine clinical exercise testing. Individuals with EI-RBBB have significantly higher all-cause mortality rates compared to those with normal and EI-ST depression ET results, which is largely explained by age.