title: Right bundle branch block without overt heart disease predicts higher risk of pacemaker implantation: the study of atomic-bomb survivors.
abstract: BACKGROUND
  We investigated the clinical course of complete right bundle branch block (RBBB) or RBBB with axis deviation (AD) in terms of subsequent pacemaker implantation for high-degree atrioventricular (AV) block or sick sinus syndrome (SSS).
  
  
  RESULTS
  Among the 16,170 atomic-bomb survivors in our biennial health examination between July 1967 and December 2010, we detected 520 newly-acquired RBBB subjects with no organic heart disease, and selected 1038 age- (at RBBB diagnosis) and sex-matched subjects without RBBB to serve as comparison subjects. Multivariate Cox regression analysis was used to estimate the hazard ratios (HRs) for the risk of pacemaker implantation due to all causes, AV block or SSS between RBBB and comparison subjects and between RBBB subjects with and without AD. The risk of pacemaker implantation for RBBB was 4.79 (95% confidence interval [CI] 1.89-12.58; P=0.001), 3.77 (95% CI, 1.09-13.07; P=0.036), and 6.28 (95% CI, 1.24-31.73, P=0.026) when implantation was for all causes, AV block and SSS, respectively. RBBB subjects with AD had a higher risk for all-cause pacemaker implantation than subjects without AD (HR, 3.03; 95% CI, 1.00-9.13, P=0.049). RBBB subjects with AD were younger than subjects without AD at the time of RBBB diagnosis (59.4±7.6 vs 74.4±3.1 years old, P=0.019), and their progression from diagnosis to pacemaker implantation took longer (15.1±6.6 vs 6.4±3.0 years, P=0.032).
  
  
  CONCLUSIONS
  RBBB, especially with AD, progresses to AV block and SSS that requires pacemaker implantation; the mechanisms by which the conduction defect progresses differ among patients with and without AD.
authors.affiliation: Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan; Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan. Electronic address: kusumoto@rerf.or.jp.
authors.forename: Saburo
authors.initials: S
authors.lastname: Kusumoto
authors.affiliation: Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kawano
authors.affiliation: Department of Molecular Physiology, Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
authors.forename: Naomasa
authors.initials: N
authors.lastname: Makita
authors.affiliation: Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Ichimaru
authors.affiliation: Department of Cardiovascular Medicine, National Health Insurance Hirado Municipal Hospital, 1125-12, Kusazumicho, Hirado 859-5363, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kaku
authors.affiliation: Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan; Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Haruta
authors.affiliation: Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Hida
authors.affiliation: Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Nobuko
authors.initials: N
authors.lastname: Sera
authors.affiliation: Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Misa
authors.initials: M
authors.lastname: Imaizumi
authors.affiliation: Department of Statistics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Nakashima
authors.affiliation: Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Maemura
authors.affiliation: Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013, Japan.
authors.forename: Masazumi
authors.initials: M
authors.lastname: Akahoshi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054537:Atrioventricular Block / Q000209:etiology* / Q000628:therapy*; D002037:Bundle-Branch Block / Q000150:complications*; D015331:Cohort Studies; D005260:Female; D006331:Heart Diseases; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D054043:Nuclear Weapons; D010138:Pacemaker, Artificial; D012189:Retrospective Studies; D018570:Risk Assessment; D012804:Sick Sinus Syndrome / Q000209:etiology* / Q000628:therapy*; D017741:Survivors
keywords: Bundle-branch block; Conduction disease; Electrocardiography; Epidemiology