title: Biomechanics of Failed Pulmonary Autografts Compared With Normal Pulmonary Roots.
abstract: BACKGROUND
  Progressive dilatation of pulmonary autografts after the Ross operation may reflect inadequate remodeling of the native pulmonary root to adapt to systemic circulation. Understanding the biomechanics of autograft root dilatation may aid designing strategies to prevent dilatation. We have previously characterized normal human pulmonary root material properties; however, the mechanical properties of failed autografts are unknown. In this study, failed autograft roots explanted during reoperation were acquired, and their material properties were determined.
  
  
  METHODS
  Failed pulmonary autograft specimens were obtained from patients undergoing reoperation after the Ross operation. Fresh human native pulmonary roots were obtained from the transplant donor network as controls. Biaxial stretch testing was performed to determine tissue mechanical properties. Tissue stiffness was determined at patient-specific physiologic stresses at pulmonary pressures.
  
  
  RESULTS
  Nonlinear stress-strain response was present in both failed autografts and normal pulmonary roots. Explanted pulmonary autografts were less stiff than were their native pulmonary root counterparts at 8 mm Hg (134 ± 42 vs 175 ± 49 kPa, respectively) (p = 0.086) and 25 mm Hg (369 ± 105 vs 919 ± 353 kPa, respectively) (p = 0.006). Autograft wall stiffness at both 8 and 25 mm Hg was not correlated with age at the Ross procedure (p = 0.898 and p = 0.813, respectively) or with time in the systemic circulation (p = 0.609 and p = 0.702, respectively).
  
  
  CONCLUSIONS
  Failed pulmonary autografts retained nonlinear response to mechanical loading typical of healthy human arterial tissue. Remodeling increased wall thickness but decreased wall stiffness in failed autografts. Increased compliance may explain progressive autograft root dilatation in autograft failures.
authors.affiliation: Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Aart
authors.initials: A
authors.lastname: Mookhoek
authors.affiliation: Department of Surgery, University of California San Francisco Medical Center and San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Kapil
authors.initials: K
authors.lastname: Krishnan
authors.affiliation: Division of Cardiology, Department of Medicine, University of Texas at Houston, Houston, Texas.
authors.forename: Sam
authors.initials: S
authors.lastname: Chitsaz
authors.affiliation: Department of Surgery, University of California San Francisco Medical Center and San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Heide
authors.initials: H
authors.lastname: Kuang
authors.affiliation: Department of Surgery, University of California San Francisco Medical Center and San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.affiliation: Department of Pediatric Cardiothoracic Surgery, Utrecht University Medical Center, Utrecht, The Netherlands.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Schoof
authors.affiliation: Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Ad J J C
authors.initials: AJ
authors.lastname: Bogers
authors.affiliation: Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Johanna J M
authors.initials: JJ
authors.lastname: Takkenberg
authors.affiliation: Department of Surgery, University of California San Francisco Medical Center and San Francisco Veterans Affairs Medical Center, San Francisco, California. Electronic address: elaine.tseng@ucsfmedctr.org.
authors.forename: Elaine E
authors.initials: EE
authors.lastname: Tseng
mesh_terms: D000886:Anthropometry; D001021:Aortic Valve / Q000002:abnormalities / Q000503:physiopathology / Q000601:surgery*; D001022:Aortic Valve Insufficiency / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D000082882:Bicuspid Aortic Valve Disease; D001794:Blood Pressure; D003187:Compliance; D004108:Dilatation, Pathologic / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D005260:Female; D006349:Heart Valve Diseases / Q000503:physiopathology; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000209:etiology / Q000473:pathology / Q000503:physiopathology* / Q000517:prevention & control; D011651:Pulmonary Artery / Q000473:pathology / Q000503:physiopathology*; D011664:Pulmonary Valve / Q000503:physiopathology / Q000601:surgery / Q000637:transplantation*; D012086:Reoperation; D013314:Stress, Mechanical; D013718:Tensile Strength; D014182:Transplantation, Autologous; D059289:Vascular Stiffness; D016474:Weight-Bearing