Right bundle branch block: Prevalence, incidence, and cardiovascular morbidity and mortality in the general population.

Background: Right bundle branch block (RBBB) is among the most common electrocardiographic abnormalities. Objectives: To establish the prevalence and incidence of RBBB in the general population without cardiovascular events (CVE) and whether RBBB increases cardiovascular morbidity and mortality compared with patients with a normal electrocardiogram (ECG). Methods: A historical study of two cohorts including 2981 patients from 29 primary health centres without baseline CVE. Cox (for CVE) and logistic (for cardiovascular factors) regression was used to assess their association with RBBB. Results: Of the patients (58% women; mean age 65.9), 92.2% had a normal ECG, 4.6% incomplete RBBB (iRBBB) and 3.2% complete RBBB (cRBBB). Mean follow-up was five years. Factors associated with appearance of cRBBB were male sex (HR = 3.8; 95%CI: 2.4-6.1) and age (HR = 1.05 per year; 95%CI: 1.03-1.08). In a univariate analysis, cRBBB was associated with an increase in all-cause mortality but only bifascicular block (BFB) was significant after adjusting for confounders. cRBBB tended to increase CVE but the results were not statistically significant. Presence of iRBBB was not associated with adverse outcomes. Patients with iRBBB who progressed to cRBBB showed a higher incidence of heart failure and chronic kidney disease. Conclusion: In this general population cohort with no CV disease, 8% had RBBB, with a higher prevalence among men and elderly patients. Although all-cause mortality and CVE tended to increase in the presence of cRBBB, only BFB showed a statistically significant association with cRBBB. Patients with iRBBB who progressed to cRBBB had a higher incidence of CVE. We detected no effect of iRBBB on morbidity and mortality.