title: Left ventricular septal and apex pacing for optimal pump function in canine hearts.
abstract: OBJECTIVE
  The goal of this study was to test the hypothesis that left ventricular (LV) pump function is optimal when pacing is performed at the LV near the sites where the impulses exit the Purkinje system.
  
  
  BACKGROUND
  Pacing at the conventional site, the right ventricular (RV) apex, adversely affects hemodynamics. During normal sinus rhythm (SR), electrical activation of the working myocardium starts at the LV septal endocardium and spreads from apex to base.
  
  
  METHODS
  Experiments were conducted in anesthetized open-chest dogs with normal ventricular conduction to investigate hemodynamic effects of pacing at various epicardial LV sites, the RV apex, and combinations of these sites (n = 11) and of RV and LV septal pacing (n = 8). The LV septal endocardium was reached via the RV by puncturing through the septum with a barbed electrode. Left ventricular systolic (LVdP/dtpos and stroke work) and diastolic (LVdP/dtneg and Tau) function were assessed using pressure-volume relations (conductance catheter technique).
  
  
  RESULTS
  Left ventricular systolic and diastolic function were highly dependent on the site of pacing, but not on QRS duration. Left ventricular function was maintained at SR level during LV septal, LV apex, and multisite pacing, was moderately depressed during pacing at epicardial LV free wall sites, and was most severely depressed during RV apex pacing. On average, RV septal pacing did not improve LV function, compared with RV apex pacing, but in each experiment one (variable) RV pacing site was found, which only moderately reduced LV function.
  
  
  CONCLUSIONS
  During ventricular pacing, LV pump function is maintained best (i.e., at SR level) when pacing at the LV septum or LV apex, potentially because pacing from these sites creates a physiological propagation of electrical conduction.
authors.affiliation: Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.
authors.forename: Maaike
authors.initials: M
authors.lastname: Peschar
authors.forename: Hans
authors.initials: H
authors.lastname: de Swart
authors.forename: Koen J
authors.initials: KJ
authors.lastname: Michels
authors.forename: Robert S
authors.initials: RS
authors.lastname: Reneman
authors.forename: Frits W
authors.initials: FW
authors.lastname: Prinzen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial / Q000379:methods; D002306:Cardiac Volume / Q000502:physiology; D004285:Dogs; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate; D013318:Stroke Volume / Q000502:physiology; D016276:Ventricular Function; D016277:Ventricular Function, Left / Q000502:physiology*; D017725:Ventricular Pressure / Q000502:physiology