title: Three-dimensional mapping of optimal left ventricular pacing site for cardiac resynchronization.
abstract: BACKGROUND
  The efficacy of cardiac resynchronization therapy (CRT) depends on placement of the left ventricular lead within the late-activated territory. The geographic extent and 3-dimensional distribution of left ventricular (LV) locations yielding optimal CRT remain unknown.
  
  
  RESULTS
  Normal or tachypacing-induced failing canine hearts made dyssynchronous by right ventricular free wall pacing or chronic left bundle-branch ablation were acutely instrumented with a nonconstraining epicardial elastic sock containing 128 electrodes interfaced with a computer-controlled stimulation/recording system. Biventricular CRT was performed using a fixed right ventricular site and randomly selected LV sites covering the entire free wall. For each LV site, global cardiac function (conductance catheter) and mechanical synchrony (magnetic resonance imaging tagging) were determined to yield 3-dimensional maps reflecting CRT impact. Optimal CRT was achieved from LV lateral wall sites, slightly more anterior than posterior and more apical than basal. LV sites yielding > or = 70% of the maximal dP/dtmax increase covered approximately 43% of the LV free wall. This distribution and size were similar in both normal and failing hearts. The region was similar for various systolic and diastolic parameters and correlated with 3-dimensional maps based on mechanical synchrony from magnetic resonance imaging strain analysis.
  
  
  CONCLUSIONS
  In hearts with delayed lateral contraction, optimized CRT is achieved over a fairly broad area of LV lateral wall in both nonfailing and failing hearts, with modest anterior or posterior deviation still capable of providing effective CRT. Sites selected to achieve the most mechanical synchrony are generally similar to those that most improve global function, confirming a key assumption underlying the use of wall motion analysis to optimize CRT.
authors.affiliation: Division of Cardiology, Johns Hopkins University, 720 Rutland Ave, Baltimore, MD 21205, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Helm
authors.forename: Melissa
authors.initials: M
authors.lastname: Byrne
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Helm
authors.forename: Samantapudi K
authors.initials: SK
authors.lastname: Daya
authors.forename: Nael F
authors.initials: NF
authors.lastname: Osman
authors.forename: Richard
authors.initials: R
authors.lastname: Tunin
authors.forename: Henry R
authors.initials: HR
authors.lastname: Halperin
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
authors.forename: Albert C
authors.initials: AC
authors.lastname: Lardo
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004285:Dogs; D004562:Electrocardiography; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D012044:Regression Analysis