title: Evaluation of pacing site in dogs with naturally occurring complete heart block.
abstract: OBJECTIVE
  To compare left ventricular synchronization and systolic performance with transvenous pacing of the right ventricular apex (RVA), left ventricular free wall (LVF) or simultaneous pacing of the RVA and LVF (BiV).
  
  
  METHODS
  Seven canine patients with complete heart block. Prospective study evaluating effect of pacing site. Twenty four hours following implantation of transvenous BiV pacing systems, electrocardiograms and echocardiograms were assessed during pacing from the: (1) Right Atrial Appendage/RVA (RAA/RVA), (2) RAA/LVF, and (3) RAA/BiV.
  
  
  RESULTS
  QRS duration was significantly shorter with BiV pacing versus LVF pacing (p<0.001), or RVA pacing (p<0.001). Echocardiographic indices of systolic performance fractional shortening (FS), ejection fraction (EF), cardiac output (CO) were significantly higher with BiV pacing than with pacing from the RVA (P=0.023, 0.006, and 0.002 respectively). Cardiac output, measured by the biplane Simpson's method, was higher with LVF versus RVA pacing (P=0.036). There was no difference in FS or EF when comparing LVF to RVA pacing. Tissue Doppler measurements of synchronization and systolic performance did not show any difference between pacing mode, but a significantly increased number of segments were seen to contract following aortic valve closure during LVF pacing (P=0.0268) and RVA pacing (P=0.0197) as compared to BiV pacing.
  
  
  CONCLUSIONS
  Findings suggest that BiV pacing improves cardiac output and systolic performance versus RVA pacing. This improvement however, is not reflected in tissue Doppler indices of synchronization and systolic performance.
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA. estradaa@vetmed.ufl.edu
authors.forename: Amara H
authors.initials: AH
authors.lastname: Estrada
authors.forename: Herbert W
authors.initials: HW
authors.lastname: Maisenbacher
authors.forename: Robert
authors.initials: R
authors.lastname: Prosek
authors.forename: Jesse
authors.initials: J
authors.lastname: Schold
authors.forename: Melanie
authors.initials: M
authors.lastname: Powell
authors.forename: James M
authors.initials: JM
authors.lastname: VanGilder
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000503:physiopathology / Q000628:therapy*; D004285:Dogs; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy / Q000662:veterinary*; D006352:Heart Ventricles / Q000503:physiopathology; D008297:Male; D010138:Pacemaker, Artificial / Q000662:veterinary*; D011446:Prospective Studies