title: Bundle branch blocks and the risk of mortality in the Atherosclerosis Risk in Communities study.
abstract: OBJECTIVE
  The main objective of our study was to evaluate the associations between different categories of bundle branch blocks (BBBs) and mortality and to consider possible impact of QRS prolongation in these associations.
  
  
  METHODS
  This analysis included 15 408 participants (mean age 54 years, 55.2% women, and 26.9% blacks) from the Atherosclerosis Risk in Communities study. We used Cox regression to examine associations between left BBB (LBBB), right BBB (RBBB) and indetermined type of ventricular conduction defect [intraventricular conduction defect (IVCD)] with coronary heart disease (CHD) death and all-cause mortality.
  
  
  RESULTS
  During a mean 21 years of follow-up, 4767 deaths occurred; of these, 728 were CHD deaths. Compared to No-BBB, LBBB and IVCD were strongly associated with increased CHD death (hazard ratios 4.11 and 3.18, respectively; P < 0.001 for both). Furthermore, compared to No-BBB with QRS duration less than 100 ms, CHD mortality risk was increased 1.33-fold for the No-BBB group with QRS duration 100-109 ms, and 1.48-fold with QRS duration 110-119 ms, 3.52-fold for pooled LBBB-IVCD group with QRS duration less than 140 ms and 4.96-fold for pooled LBBB-IVCD group with QRS duration at least 140 ms (P < 0.001). However, mortality risk was not significantly increased for lone RBBB. For all-cause mortality, trends similar to those for CHD death were observed within the BBB groups, although at lower levels of risk.
  
  
  CONCLUSIONS
  Prevalent LBBB and IVCD, but not RBBB, are associated with increased risk of CHD death and all-cause mortality. Mortality risk is further increased as the QRS duration is prolonged above 140 ms.
authors.affiliation: aEpidemiological Cardiology Research Center (EPICARE), Department of Epidemiology and Prevention, Division of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem bDepartment of Epidemiology, Galling's School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill cDepartment of Internal Medicine, Section of Cardiology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA.
authors.forename: Zhu-Ming
authors.initials: ZM
authors.lastname: Zhang
authors.forename: Pentti M
authors.initials: PM
authors.lastname: Rautaharju
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Prineas
authors.forename: Laura
authors.initials: L
authors.lastname: Loehr
authors.forename: Wayne
authors.initials: W
authors.lastname: Rosamond
authors.forename: Elsayed Z
authors.initials: EZ
authors.lastname: Soliman
mesh_terms: D050197:Atherosclerosis / Q000401:mortality / Q000503:physiopathology; D053840:Brugada Syndrome / Q000401:mortality / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000401:mortality* / Q000503:physiopathology; D000075224:Cardiac Conduction System Disease; D003324:Coronary Artery Disease / Q000401:mortality / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment / Q000379:methods; D014481:United States / Q000453:epidemiology