title: Increasing left ventricular pacing output decreases interventricular conduction time in patients with biventricular pacing systems.
abstract: OBJECTIVE
  To evaluate the effect of increasing LV pacing output on interventricular timing in patients with biventricular pacing systems.
  
  
  BACKGROUND
  Clinical improvement with biventricular pacing is likely related to reduction in ventricular dysynchrony in patients with cardiomyopathy. We hypothesized that increasing left ventricular pacing output would reduce interventricular conduction time and could affect ventricular synchrony.
  
  
  METHODS
  Forty-two sequential patients with biventricular pacing systems that permitted independent LV pacing were selected at the time of routine device interrogation. The interval between LV pacing stimulus and onset of the RV electrogram was measured during LV pacing at capture threshold and at maximum pacing output for each patient.
  
  
  RESULTS
  The average time from LV pacing stimulus to right ventricular electrogram onset was 142.5 +/- 32.5 ms (range 90-230 ms) at threshold and 132.3 +/- 30.4 ms (range 90-220 ms) at maximum pacing output, with a mean decrease in conduction time of 10.2 +/- 10.9 ms (range 0-45 ms). There was significantly greater interventricular conduction shortening with increased pacing output in patients with ischemic cardiomyopathy compared to others (14.9 +/- 11.9 ms vs 4.0 +/- 4.6 ms; P < 0.01).
  
  
  CONCLUSIONS
  Conduction time from LV to RV shortens as LV pacing output is increased. This effect is seen to a greater degree in patients with ischemic cardiomyopathy, possibly related to the presence of myocardial scar near the pacing electrode. Further investigation is needed to assess the clinical outcomes related to this new method for optimizing resynchronization therapy.
authors.affiliation: Electrophysiology Section, Division of Cardiovascular Medicine, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA. william.sauer@uphs.upenn.edu
authors.forename: William H
authors.initials: WH
authors.lastname: Sauer
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Sussman
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Verdino
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Cooper
mesh_terms: D000368:Aged; D017147:Defibrillators, Implantable; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D013997:Time Factors; D016277:Ventricular Function, Left