title: Normal and shear strains of the left ventricle in healthy human subjects measured by two-dimensional speckle tracking echocardiography.
abstract: BACKGROUND
  Animal studies have shown that shear deformation of myocardial sheets in transmural planes of left ventricular (LV) wall is an important mechanism for systolic wall thickening, and normal and shear strains of the LV free wall differ from those of the interventricular septum (IVS). We sought to test whether these also hold for human hearts.
  
  
  METHODS
  Thirty healthy volunteers (male 23 and female 7, aged 34 ± 6 years) from Outpatient Department of the University of Tokyo Hospital were included. Echocardiographic images were obtained in the left decubitus position using a commercially available system (Aloka SSD-6500, Japan) equipped with a 3.5-MHz transducer. The ECG was recorded simultaneously. The peak systolic radial normal strain (length change), shear strain (angle change) and time to peak systolic radial normal strain were obtained non-invasively by two-dimensional speckle tracking echocardiography.
  
  
  RESULTS
  The peak systolic radial normal strain in both IVS and LV posterior wall (LVPW) showed a trend to increase progressively from the apical level to the basal level, especially at short axis views, and the peak systolic radial normal strain of LVPW was significantly greater than that of IVS at all three levels. The time to peak systolic radial normal strain was the shortest at the basal IVS, and increased progressively from the base to the apical IVS. It gradually increased from the apical to the basal LVPW in sequence, especially at short axis views. The peak of radial normal strain of LVPW occurred much later than the peak of IVS at all three levels. For IVS, the shear deformation was clockwise at basal level, and counterclockwise at mid and apical levels in LV long-axis view. For LVPW, the shear deformations were all counterclockwise in LV long-axis view and increased slightly from base to the apex. LVPW showed larger shear strains than IVS at all three levels. Bland-Altman analysis shows very good agreement between measurements taken by the same observer and by two independent observers.
  
  
  CONCLUSIONS
  "Myocardial sheets" theory also holds true for intact human LV. Moreover, dyssynchrony exists even in healthy human subjects, which should be considered when evaluating the diseased hearts.
authors: Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, China. yuanlj@fmmu.edu.cn.
authors: Li-Jun
authors: LJ
authors: Yuan
authors: Katsu
authors: K
authors: Takenaka
authors: Kansei
authors: K
authors: Uno
authors: Aya
authors: A
authors: Ebihara
authors: Kazuno
authors: K
authors: Sasaki
authors: Takako
authors: T
authors: Komuro
authors: Makoto
authors: M
authors: Sonoda
authors: Ryozo
authors: R
authors: Nagai
mesh_terms: D000328:Adult; D004452:Echocardiography / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D015588:Observer Variation; D012016:Reference Values; D013314:Stress, Mechanical; D013318:Stroke Volume / Q000502:physiology; D013599:Systole / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D016277:Ventricular Function, Left / Q000502:physiology*