title: Radiological and electrocardiographic characterization of right ventricular outflow tract pacing.
abstract: OBJECTIVE
  The right ventricular outflow tract (RVOT) is used as an alternative pacing site, but its superiority to the RV apex remains to be established. This lack of proof may in part be explained by heterogeneity within the RVOT-paced group, due to poor definitions of the RVOT. The aim of the present study is to characterize the RVOT in terms of fluoroscopic and electrocardiographic parameters.
  
  
  RESULTS
  One hundred and forty-three patients who underwent pacemaker implantation with a ventricular lead in the RVOT were included. Lead position was determined by fluoroscopy. The RVOT was divided into three areas: anterior, septal, and free wall (FW). On a 12-lead electrocardiogram (ECG) during forced ventricular pacing, QRS duration, configuration, and amplitude was determined. Lead position was judged to be anterior in 52 (36%), septal in 43 (30%), and FW in 48 (34%) patients, respectively. QRS duration is not significantly different between groups. QRS axis differs significantly between pacing sites (septal 79 ± 31°, anterior 60 ± 46°, FW 47 ± 38°, P < 0.05). QRS vector in lead I and QRS morphology and vector in lead aVL differ significantly between pacing sites. Precordial transition is earlier (towards V1) in septal pacing.
  
  
  CONCLUSIONS
  This study demonstrates heterogeneity of pacing site and depolarization pattern within a cohort of patients paced form the RVOT. However, due to considerable overlap, we could not define clear cut-off point or devise flow-charts to match ECG and pacing site.
authors.affiliation: Department of Cardiology, St Antonius Hospital, PO Box 2500, 3430 EM Nieuwegein, The Netherlands. j.balt@antoniusziekenhuis.nl
authors.forename: Jippe C
authors.initials: JC
authors.lastname: Balt
authors.forename: Norbert M
authors.initials: NM
authors.lastname: van Hemel
authors.forename: Hein J J
authors.initials: HJ
authors.lastname: Wellens
authors.forename: Willem G
authors.initials: WG
authors.lastname: de Voogt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D015331:Cohort Studies; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011859:Radiography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D054088:Ventricular Septum / Q000503:physiopathology