title: Experimental study of anisotropic stress/strain relationships of the piglet great vessels and relevance to pediatric congenital heart disease.
abstract: BACKGROUND
  Determining material mechanical properties of neonatal aorta and pulmonary artery will aid understanding tissue behavior when subjected to abnormal hemodynamics of congenital heart disease.
  
  
  METHODS
  Aorta and pulmonary arteries were harvested from 6 neonatal piglets (mean weight 3.5 kg). Tissue samples from ventral and dorsal aspects of ascending aorta (AA) and descending aorta (DA), innominate artery (IA), left subclavian artery (LScA), main pulmonary artery (MPA), and left pulmonary artery (LPA) and right pulmonary artery (RPA) were obtained in three orientations: circumferential, diagonal, and longitudinal. Samples were subjected to uniaxial tensile testing. True strain-Cauchy stress curves were individually fitted for each orientation to calibrate the Fung model, and to measure tissue stiffness (10% strain).
  
  
  RESULTS
  All samples, for all orientations, demonstrated nonlinear hyperelastic strain-stress response to uniaxial tensile testing (Holzapfel-Gasser and fitted-Fung models R(2) > 0.95). For each vessel segment, stiffness was not significantly different among orientations. Stiffness values in all orientations, including ventral/dorsal samples, were compared between AA > MPA (p = 0.08), DA > MPA (p < 0.01), and DA > AA (p = 0.35). Comparison of circumferential orientation samples showed AA and DA are significantly stiffer than MPA (p < 0.05), and MPA stiffness was similar to that of the RPA but slightly greater than LPA. Also, dorsal circumferential samples of all segments were slightly stiffer than ventral (p = 0.21). Dorsal aspect of AA was slightly stiffer in all orientations (p = 0.248).
  
  
  CONCLUSIONS
  The neonatal aorta and pulmonary artery exhibit hyperelastic biomechanical behavior with an anisotropic effect. Differences between aorta and pulmonary artery may play a role in native tissue behavior, ventricular and arterial mechanical coupling, and risk of deformation due to abnormal hemodynamics of congenital heard disease.
authors: Department of Mechanical and Aerospace Engineering, College of Engineering and Computer Science, University of Central Florida, Orlando, Florida.
authors: Yueqian
authors: Y
authors: Jia
authors: Department of Cardiothoracic Surgery, Arnold Palmer Hospital for Children, Orlando, Florida.
authors: I Ricardo
authors: IR
authors: Argueta-Morales
authors: Department of Mechanical and Aerospace Engineering, College of Engineering and Computer Science, University of Central Florida, Orlando, Florida.
authors: Miao
authors: M
authors: Liu
authors: Department of Mechanical and Aerospace Engineering, College of Engineering and Computer Science, University of Central Florida, Orlando, Florida.
authors: Yuanli
authors: Y
authors: Bai
authors: Department of Mechanical Engineering, College of Engineering, Embry-Riddle Aeronautical University, Daytona Beach, Florida.
authors: Eduardo
authors: E
authors: Divo
authors: Department of Mechanical and Aerospace Engineering, College of Engineering and Computer Science, University of Central Florida, Orlando, Florida.
authors: Alain J
authors: AJ
authors: Kassab
authors: Department of Mechanical and Aerospace Engineering, College of Engineering and Computer Science, University of Central Florida, Orlando, Florida; Department of Cardiothoracic Surgery, Arnold Palmer Hospital for Children, Orlando, Florida; College of Medicine, University of Central Florida, Orlando, Florida. Electronic address: william.decampli@orlandohealth.com.
authors: William M
authors: WM
authors: DeCampli
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016880:Anisotropy; D001013:Aorta, Thoracic / Q000502:physiology*; D001696:Biomechanical Phenomena; D002648:Child; D004548:Elasticity / Q000502:physiology*; D006330:Heart Defects, Congenital / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D010372:Pediatrics; D011651:Pulmonary Artery / Q000502:physiology*; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013552:Swine; D020858:Tissue and Organ Harvesting