title: MR study of postnatal development of myocardial structure and left ventricular function.
abstract: OBJECTIVE
  To investigate postnatal development of left ventricular (LV) cardiac function and myocardium structure.
  
  
  METHODS
  In vivo cardiac MR and ex vivo diffusion tensor imaging (DTI) were performed in normal Sprague-Dawley rats at postnatal day 2, 4, 7, 14, 21, 28, and 56 (N = 6 per group).
  
  
  RESULTS
  Morphologically, LV size increased with age. Functionally, stroke volume and cardiac output increased. Heart rate increased gradually and became stable after day 14. On average, ejection fraction increased within the first 4 days, decreased at day 7, gradually increased until day 21, and became stable afterward. Structurally, double-helical myocardial structure was found as early as day 2. Myocardial fiber parameters, described by fractional anisotropy, mean apparent diffusion coefficient, and axial diffusivity, increased within the first 4 days. Then radial diffusivity increased until day 7 while other parameters decreased up to day 56.
  
  
  CONCLUSIONS
  Postnatal heart development was documented by MRI. DTI findings are in agreement with the two known stages of early postnatal growth: hyperplasia and hypertrophy. These results can serve as the baselines for study of postnatal heart developmental abnormalities. They also demonstrate the ability of DTI to reveal microstructural alterations in myocardium.
authors.affiliation: Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Wu
authors.forename: Ed X
authors.initials: EX
authors.lastname: Wu
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D016880:Anisotropy; D002302:Cardiac Output / Q000502:physiology; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D006321:Heart / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000033:anatomy & histology; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*