title: Long-term mechanical consequences of permanent right ventricular pacing: effect of pacing site.
abstract: BACKGROUND
  Long-term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long-term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function.
  
  
  METHODS
  Fifty-eight patients who were prospectively randomized to long-term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18-segment time-to-peak longitudinal systolic strain and 12-segment time-to-peak systolic tissue velocity. Intra-LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time-to-onset of systolic flow in the RVOT and LV outflow tract. Septal A' was measured using tissue velocity images.
  
  
  RESULTS
  Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end-systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT-paced group over the RVA-paced patients. RVA-pacing was associated with greater interventricular mechanical dyssynchrony and intra-LV dyssynchrony than RVOT-pacing. Septal A' was adversely affected by intra-LV dyssynchrony (P < 0.05).
  
  
  CONCLUSIONS
  Long-term RVOT-pacing was associated with superior indices of LV structure and function compared with RVA-pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing.
authors.affiliation: Cardiovascular Research Centre, Department of Cardiology, Royal Adelaide Hospital, Adelaide, Australia.
authors.forename: Darryl P
authors.initials: DP
authors.lastname: Leong
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Mitchell
authors.forename: Ingrid
authors.initials: I
authors.lastname: Salna
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Brooks
authors.forename: Gautam
authors.initials: G
authors.lastname: Sharma
authors.forename: Han S
authors.initials: HS
authors.lastname: Lim
authors.forename: Muayad
authors.initials: M
authors.lastname: Alasady
authors.forename: Malcolm
authors.initials: M
authors.lastname: Barlow
authors.forename: James
authors.initials: J
authors.lastname: Leitch
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
authors.forename: Glenn D
authors.initials: GD
authors.lastname: Young
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*