title: Canine left ventricle electromechanical behavior under different pacing modes.
abstract: BACKGROUND
  Cardiac resynchronization therapy may improve survival and quality of life in patients suffering from heart failure with left ventricular (LV) contraction dyssynchrony. While several studies have investigated electrical or mechanical determinants of synchronous contraction, few have focused on activation contraction coupling at a macroscopic level.
  
  
  OBJECTIVE
  The objective of the study was to characterize LV electromechanical behavior and response to pacing in a heart failure model.
  
  
  METHODS
  We analyzed data from 3D electroanatomic non-contact mapping and blood pool SPECT for 12 dogs with right ventricular (RV) tachycardia pacing-induced dilated cardiomyopathy. Surfaces generated by the two modalities were registered. Electrical signals were analyzed, and endocardial wall displacement curves were portrayed.
  
  
  RESULTS
  Rapid pacing decreased the mean LV ejection fraction (LVEF) to 20.9 % and prolonged the QRS duration to 79 ± 10 ms (normal range: 40-50 ms). QRS duration remained unchanged with biventricular pacing (88.5 ms), while single site pacing further prolonged the QRS duration (113.3 ms for RV pacing and 111.6 ms for LV pacing). No trend was observed in LV systolic function. Activation duration time was significantly increased with all pacing modes compared to baseline. Finally, electromechanical delay, as defined by the delay between electrical activation and mechanical response, was increased by single site pacing (172.9 ms for RV pacing and 174.6 ms for LV pacing) but not by biventricular pacing (162.4 ms).
  
  
  CONCLUSIONS
  Combined temporal and spatial coregistration electroanatomic maps and baseline gated blood pool SPECT imaging allowed us to quantify activation duration time, electromechanical delay, and LVEF for different pacing modes. Even if pacing modes did not significantly modify LVEF or activation duration, they produced alterations in electromechanical delay, with biventricular pacing significantly decreasing the electromechanical delay as measured by surface tracings and endocardial non-contact mapping.
authors.affiliation: Department of Nuclear Medicine, Montreal Heart Institute, University of Montreal, 5000 Belanger Street, Montreal, Quebec H1T 1C8, Canada.
authors.forename: Thanh-Thuy
authors.initials: TT
authors.lastname: Vo Thang
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.forename: Vincent
authors.initials: V
authors.lastname: Finnerty
authors.forename: Matthieu
authors.initials: M
authors.lastname: Pelletier-Galarneau
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
authors.forename: Jean
authors.initials: J
authors.lastname: Grégoire
authors.forename: François
authors.initials: F
authors.lastname: Harel
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018780:Body Surface Potential Mapping / Q000379:methods; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology*; D004195:Disease Models, Animal; D004285:Dogs; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*