title: Effect of cardiac resynchronization on myocardial efficiency and regional oxidative metabolism.
abstract: BACKGROUND
  Recent studies have demonstrated increased left ventricular contractility with cardiac resynchronization therapy (CRT) using atriobiventricular stimulation. This study evaluated the effect of CRT on myocardial oxidative metabolism and efficiency.
  
  
  RESULTS
  Eight patients with New York Heart Association functional class III-IV congestive heart failure were studied during atrial pacing (control) and atriobiventricular stimulation at the same rate. The monoexponential clearance rate of [11C]acetate (k(mono)) was measured with positron emission tomography to assess myocardial oxidative metabolism in the left and right ventricles (LV and RV, respectively). Myocardial efficiency was measured using the work metabolic index (WMI). Stroke volume index improved by 10% (P=0.011) with CRT, although both global LV and RV k(mono) were unchanged compared with control. Septal k(mono) increased by 15% (P=0.04), and the septal/lateral wall k(mono) ratio increased by 22% (P=0.01). WMI increased by 13% (P=0.024) with CRT.
  
  
  CONCLUSIONS
  CRT improves LV function without increasing global LV oxidative metabolism, resulting in improved myocardial efficiency. Oxidative metabolism of the interventricular septum increases relative to the lateral wall, which suggests successful resynchronization.
authors.affiliation: Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Heikki
authors.initials: H
authors.lastname: Ukkonen
authors.forename: Rob S B
authors.initials: RS
authors.lastname: Beanlands
authors.forename: Ian G
authors.initials: IG
authors.lastname: Burwash
authors.forename: Robert A
authors.initials: RA
authors.lastname: de Kemp
authors.forename: Claude
authors.initials: C
authors.lastname: Nahmias
authors.forename: Ernest
authors.initials: E
authors.lastname: Fallen
authors.forename: Michael R S
authors.initials: MR
authors.lastname: Hill
authors.forename: Anthony S L
authors.initials: AS
authors.lastname: Tang
mesh_terms: D006321:Heart / Q000000981:diagnostic imaging; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000378:metabolism*; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010138:Pacemaker, Artificial; D013318:Stroke Volume; D014055:Tomography, Emission-Computed; D016277:Ventricular Function, Left