title: Left ventricular strain distribution in healthy dogs and in dogs with tachycardia-induced dilated cardiomyopathy.
abstract: BACKGROUND
  Recently, left ventricular (LV) strain distribution pattern has been assessed in several cardiac disease states. Tachycardia-induced cardiomyopathy (TIC) is an animal model of non-ischemic cardiomyopathy well characterized in terms of global LV dysfunction but with poor understanding of regional variability in LV function. We hypothesized that TIC induces specific changes in LV strain distribution pattern.
  
  
  METHODS
  Twenty five adult mongrel conscious dogs were trained to lie down calmly for echocardiography. In seven selected dogs, we implanted pacing system for TIC induction under general anesthesia. We measured LV geometry and function, strains, and torsion before and after the development of TIC in awake non-sedated state.
  
  
  RESULTS
  In 25 healthy dogs, all three types of normal strain significantly increased from base to apex (p <0.05), while a definite and recognizable twist could be measured due to presence of shear strain. In 7 dogs with TIC, marked changes in LV mechanics occurred throughout the cardiac cycle, resulting in decrease of strain (p <0.001), twist (p <0.05), and negative peak twist rate (p <0.05). Interestingly, the relative decrease of strain due to TIC was more pronounced in the apex (p < 0.001), with the radial strain decreasing the most (p < 0.05).
  
  
  CONCLUSIONS
  TIC is accompanied by decreased systolic LV strain and twist deformation, as well as loss of early diastolic recoil. In addition, the decrease of strain was more profound in the apex. This "reverse" distribution of LV strain may help us understand LV dysfunction in the presence of nonischemic etiology.
authors.forename: Kenya
authors.initials: K
authors.lastname: Kusunose
authors.forename: Youhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Todor N
authors.initials: TN
authors.lastname: Mazgalev
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
authors.affiliation: Department of Cardiovascular Medicine, Cleveland Clinic, Heart and Vascular Institute, 9500 Euclid Avenue, Desk J1-5, Cleveland, OH 44195, USA. popoviz@ccf.org.
authors.forename: Zoran B
authors.initials: ZB
authors.lastname: Popović
mesh_terms: D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D004285:Dogs; D004452:Echocardiography / Q000379:methods; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D012016:Reference Values; D013314:Stress, Mechanical; D017180:Tachycardia, Ventricular / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*