title: Hemodynamic improvement in cardiac resynchronization does not require improvement in left ventricular rotation mechanics: three-dimensional tagged MRI analysis.
abstract: BACKGROUND
  Earlier studies have yielded conflicting evidence on whether or not cardiac resynchronization therapy (CRT) improves left ventricular (LV) rotation mechanics.
  
  
  RESULTS
  In dogs with left bundle branch block and pacing-induced heart failure (n=7), we studied the effects of CRT on LV rotation mechanics in vivo by 3-dimensional tagged magnetic resonance imaging with a temporal resolution of 14 ms. CRT significantly improved hemodynamic parameters but did not significantly change the LV rotation or rotation rate. LV torsion, defined as LV rotation of each slice with respect to that of the most basal slice, was not significantly changed by CRT. CRT did not significantly change the LV torsion rate. There was no significant circumferential regional heterogeneity (anterior, lateral, inferior, and septal) in LV rotation mechanics in either left bundle branch block with pacing-induced heart failure or CRT, but there was significant apex-to-base regional heterogeneity.
  
  
  CONCLUSIONS
  CRT acutely improves hemodynamic parameters without improving LV rotation mechanics. There is no significant circumferential regional heterogeneity of LV rotation mechanics in the mechanically dyssynchronous heart. These results suggest that LV rotation mechanics is an index of global LV function, which requires coordination of all regions of the left ventricle, and improvement in LV rotation mechanics appears to be a specific but insensitive index of acute hemodynamic response to CRT.
authors.affiliation: Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute/NIH, Bethesda, MD 20892, USA. hashika1@jhmi.edu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ashikaga
authors.forename: Christophe
authors.initials: C
authors.lastname: Leclercq
authors.forename: Jiangxia
authors.initials: J
authors.lastname: Wang
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
authors.forename: Elliot R
authors.initials: ER
authors.lastname: McVeigh
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D002037:Bundle-Branch Block / Q000503:physiopathology* / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D004285:Dogs; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006439:Hemodynamics; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D012399:Rotation; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology* / Q000628:therapy*