title: Electrocardiographic characteristics in right ventricular vs biventricular pacing in patients with paced right bundle-branch block QRS pattern.
abstract: BACKGROUND
  A paced right bundle-branch block (RBBB) QRS morphology is present in most patients with biventricular pacing (BiVP) but is also present in some patients with right ventricular pacing (RVP). The aim of this study was to determine if there are electrocardiographic characteristics that distinguish BiVP from RVP in patients with a paced RBBB QRS pattern.
  
  
  METHODS
  Twelve-lead-paced electrocardiograms (ECGs) were analyzed from 356 consecutive patients (302 RVP and 54 BiVP). Further analyses were performed on those ECGs with a paced RBBB morphology, which included QRS pattern, axis, amplitude, and precordial transition. Chest radiography and coronary sinus venography were used to determine the location of the pacing leads.
  
  
  RESULTS
  Fifty (16.6%) of 302 RVP ECGs and 50 (92.6%) of 54 BiVP ECGs had RBBB-paced morphology, respectively. Electrocardiographic characteristics identified in this study with a paced RBBB QRS morphology that are associated with RVP but not with BiVP (P < .05) include positive concordance in the precordial leads, qR configuration in lead V(1), and a late QRS transition beyond lead V(3). Biventricular pacing had shorter mean-paced QRS duration than did RVP and was associated with right superior quadrant mean frontal QRS axis (P < .05). Right ventricular pacing was associated with a mean frontal QRS axis in the left superior quadrant (P < .05). Regarding left ventricular (LV) pacing site, a late precordial transition (especially beyond lead V(2)) was significantly associated with a more posterior LV lead location (P < .05).
  
  
  CONCLUSIONS
  Even among patients with a paced RBBB QRS pattern, the 12-lead ECG can help distinguish RVP from BiVP and determine LV lead location during BiVP. This information may be useful in evaluating nonresponse to BiVP resulting either from LV noncapture (with consequent RVP) or from suboptimal LV lead location during BiVP.
authors.affiliation: Cardiac Electrophysiology Service, University of California San Francisco Medical Center, San Francisco, California, USA.
authors.forename: Marwan
authors.initials: M
authors.lastname: Refaat
authors.forename: Moussa
authors.initials: M
authors.lastname: Mansour
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.forename: Jeremy
authors.initials: J
authors.lastname: Ruskin
authors.forename: E Kevin
authors.initials: EK
authors.lastname: Heist
mesh_terms: D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000517:prevention & control*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D006352:Heart Ventricles; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity