title: Speckle tracking analysis of the left ventricular anterior wall shows significantly decreased relative radial strain patterns in dystrophin deficient mice after 9 months of age.
abstract: BACKGROUND
  Duchenne muscular dystrophy (DMD) is an inherited X-linked disorder with an incidence of 1 in 3,500 male births. Early treatment of DMD cardiomyopathy is under investigation and echocardiographic analysis of strain patterns may provide measures to better quantify early treatment outcomes.
  
  
  METHODS
  We compared cardiac function in 3, 9 and 12 month old dystrophin deficient mdx mice to wild type (C57BL10/J) using in vivo high frequency echocardiography (Vevo 770, VisualSonics, Inc., Toronto, CA) and 2D speckle tracking [Velocity Vector Imaging (VVI), Siemens Medical Solutions, Inc., Malvern, PA]. Mice were anesthetized with 1-2% inhaled isoflurane and images were obtained using a 30 MHz transducer in modified parasternal long and short axis views obtained at the level of the papillary muscles. Myocardial motion was analyzed using VVI in single-beat reconstructed images.
  
  
  RESULTS
  M-mode imaging showed significantly decreased shortening fraction in mdx mice compared to wild type at 12 months of age (SF% 26.6±3 vs. 32.2±2; p=0.002). Mdx mice showed significantly increased cardiac fibrosis at 12 months of age compared to controls (p<0.0001). Speckle tracking analysis of the left anterior mid ventricular wall segment showed significantly decreased relative radial strain in mdx mice at 9 and 12 months (4.5±1.3% vs. 8.4±0.7%; p=0.001). There were no significant differences in circumferential or longitudinal strain.
  
  
  CONCLUSIONS
  Mdx mice show significantly decreased LV anterior mid wall radial strain with mild cardiomyopathy after 9 months of age compared to wild type. Speckle tracking analysis may provide novel outcome measures for preclinical cardiac drug treatment studies in DMD.
authors.affiliation: Associate Professor of Pediatrics, Division of Pediatric Cardiology, Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC;  Research Associate, Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC and  Associate Professor of Integrative Systems Biology and Pediatrics, Department of Integrative Systems Biology, George Washington University School of Medicine and Health Sciences, Research Center for Genetic Medicine, Children's National Medical Center, Washington, DC.
authors.forename: Christopher
authors.initials: C
authors.lastname: Spurney
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
authors.forename: Kannaboyina
authors.initials: K
authors.lastname: Nagaraju