title: Principal strain orientation in the normal human left ventricle.
abstract: BACKGROUND
  Methods that can improve the accuracy of application of directed intervention in the treatment of coronary artery disease deserve investigation. Magnetic resonance imaging with tissue tagging allows for noninvasive, quantitative determination of regionally varying minimum principal strain. Because the directional vector of minimum principal strain has been shown to be sensitive to ischemic involvement, my colleagues and I sought to fully characterize the normal range of vector direction in the in vivo human left ventricle at rest and during inotropic stimulation.
  
  
  METHODS
  Tagged magnetic resonance imaging image sets were acquired in 20 healthy volunteers at rest and during dobutamine infusion. Strain was computed from the measured displacement data by using finite element software. Orientation of minimum principal strain was characterized by measuring the angle (principal strain angle) between the minimum principal strain vector and the local circumferential-longitudinal plane. Values of this angle were computed in 6 ventricular regions and globally.
  
  
  RESULTS
  Resting values of the principal strain angle were small in every region, confirming that maximal normal myocardial contraction occurs primarily in the circumferential-longitudinal plane. Angles were similar during dobutamine infusion. Comparisons between ventricular walls, both at rest and with dobutamine, revealed no marked regional differences in the principal strain angle.
  
  
  CONCLUSIONS
  The direction of maximal myocardial contraction is known to change with ischemic injury to the myocardium and can be a sensitive, regionally varying index of myocardial ischemia. The critical first step in the clinical application of this technology is to accurately characterize normal ranges of principal strain angles.
authors.affiliation: Department of Surgery, Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Cupps
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Pomerantz
authors.forename: Marc D
authors.initials: MD
authors.lastname: Krock
authors.forename: Joseph
authors.initials: J
authors.lastname: Villard
authors.forename: Joseph
authors.initials: J
authors.lastname: Rogers
authors.forename: Nader
authors.initials: N
authors.lastname: Moazami
authors.forename: Michael K
authors.initials: MK
authors.lastname: Pasque
mesh_terms: D000328:Adult; D000368:Aged; D003326:Coronary Circulation; D004280:Dobutamine / Q000494:pharmacology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000503:physiopathology; D016276:Ventricular Function
chemical_list: D004280:Dobutamine