title: Predictors of long-term benefit of cardiac resynchronization therapy in patients with right bundle branch block.
abstract: OBJECTIVE
  The aims of this study were: (i) to characterize consecutive cardiac resynchronization therapy (CRT) recipients with right bundle branch block (RBBB) in comparison with left bundle branch block (LBBB) and (ii) to identify independent predictors of long-term outcome among CRT recipients with RBBB. The presence of RBBB has been associated with poorer prognosis after CRT compared with LBBB; however, little is known about the differences in cardiac mechanics between RBBB and LBBB patients. Furthermore, predictors of favourable outcome after CRT in patients with RBBB have not been identified.
  
  
  RESULTS
  Five hundred and sixty-one consecutive CRT recipients (89 with RBBB and 472 with LBBB) underwent echocardiography before and 6 months after CRT to determine left ventricular (LV) size and function, and interventricular and LV dyssynchrony (as measured by tissue Doppler imaging). Long-term follow-up to identify a composite endpoint of all-cause mortality or heart failure hospitalization was available. Right bundle branch block patients exhibited a higher prevalence of male gender, ischaemic heart disease, atrial fibrillation, and lower exercise capacity when compared with LBBB patients, despite smaller LV volumes. In addition, the extent of both interventricular and LV dyssynchrony was less in RBBB patients. Six months after CRT, RBBB patients also showed limited LV reverse remodelling. At long-term follow-up, LV dyssynchrony and mitral regurgitation were identified as independent predictors of all-cause mortality or heart failure hospitalization among RBBB patients.
  
  
  CONCLUSIONS
  Left ventricular dyssynchrony may be an important determinant of outcome following CRT in patients with RBBB and may help in the selection of CRT candidates.
authors.affiliation: Department of Cardiology,  Leiden University Medical Centre, Albinusdreef 2, 2333 ZA Leiden,  The Netherlands.
authors.forename: Darryl P
authors.initials: DP
authors.lastname: Leong
authors.forename: Ulas
authors.initials: U
authors.lastname: Höke
authors.forename: Victoria
authors.initials: V
authors.lastname: Delgado
authors.forename: Dominique
authors.initials: D
authors.lastname: Auger
authors.forename: Joep
authors.initials: J
authors.lastname: Thijssen
authors.forename: Lieselot
authors.initials: L
authors.lastname: van Erven
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schalij
authors.forename: Nina Ajmone
authors.initials: NA
authors.lastname: Marsan
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004562:Electrocardiography; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D016896:Treatment Outcome; D020257:Ventricular Remodeling / Q000502:physiology