title: A composite semiresorbable armoured scaffold stabilizes pulmonary autograft after the Ross operation: Mr Ross's dream fulfilled.
abstract: OBJECTIVE
  Use of resorbable external reinforcement of the pulmonary autograft during the Ross operation has been suggested, but the differential regional potential for dilation of the aorta, mainly regarding the neo-root and the neo-Valsalva sinuses, represents an unresolved issue. Auxetic materials could be useful in preventing dilation given their favorable mechanical properties. We designed a composite semiresorbable armoured bioprosthesis constituted by polydioxanone and expanded polytetrafluoroethylene and evaluated its effectiveness as a pulmonary autograft reinforcement device in an animal model of the Ross procedure.
  
  
  METHODS
  An experimental model of the Ross procedure was performed in 20 three-month-old growing lambs. The pulmonary autograft was alternatively nonreinforced (control group n = 10) or reinforced with composite bioprosthesis (reinforced group n = 10). Animals were followed up during growth for 6 months by angiography and echocardiography. Specific stainings for extracellular matrix and immunohistochemistry for metalloproteinase-9 were performed.
  
  
  RESULTS
  Reference aortic diameter increased from 14 ± 1 mm to 19 ± 2 mm over 6 months of growth. In the control group, pulmonary autograft distension (28 ± 2 mm) was immediately noted, followed by aneurysm development at 6 months (40 ± 2 mm, P < .001 vs reference). In the reinforced group, an initial dilation to 18 ± 1 mm was detected and the final diameter was 27 ± 2 mm (42% increase). Two deaths due to pulmonary autograft rupture occurred in the control group. On histology, the control group showed medial disruption with connective fibrous replacement, whereas in the reinforced group compensatory intimal hyperplasia was present in the absence of intimal tears. The bioprosthesis promoted a positive matrix rearrangement process favoring neoarterialization and elastic remodeling as demonstrated on specific staining for elastin collagen and metalloproteinase-9.
  
  
  CONCLUSIONS
  The device adapted and functionally compensated for the characteristics of autograft growth, guaranteeing a reasonable size of the autograft at 6 months, but more important, because the device is biocompatible, it did not disrupt the biological process of growth or cause inflammatory damage to the wall.
authors.affiliation: Cardiac Surgery Centre Cardiologique du Nord de Saint-Denis, Paris, France. Electronic address: francesconappi2@gmail.com.
authors.forename: Francesco
authors.initials: F
authors.lastname: Nappi
authors.affiliation: Department of Cardiothoracic Surgery, Golden Jubilee National Hospital, Clydebank, Glasgow, United Kingdom.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Spadaccio
authors.affiliation: Department of Structures and Interdisciplinary Research Center for Biomaterials, University of Napoli Federico II, Naples, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Fraldi
authors.affiliation: Department of Public Health, University of Naples "Federico II", Naples, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Montagnani
authors.affiliation: Department of Pathology, Hôpital de la Salpétrière, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Fouret
authors.affiliation: Laboratory of Biosurgical Research, Carpentier Foundation, Pompidou Hospital, University Paris Descartes, Paris, France.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Chachques
authors.affiliation: Department of Cardiovascular Surgery, Hôpital de la Salpétrière, Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Acar
mesh_terms: D020341:Absorbable Implants; D000367:Age Factors; D000818:Animals; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000254:growth & development / Q000378:metabolism / Q000601:surgery*; D001014:Aortic Aneurysm / Q000175:diagnosis / Q000209:etiology; D001027:Aortography; D064592:Autografts; D001705:Bioprosthesis; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D004108:Dilatation, Pathologic; D005109:Extracellular Matrix / Q000378:metabolism; D006085:Graft Survival; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D023421:Models, Animal; D016687:Polydioxanone / Q000737:chemistry; D011138:Polytetrafluoroethylene / Q000737:chemistry; D011474:Prosthesis Design; D011651:Pulmonary Artery / Q000637:transplantation*; D012756:Sheep; D013997:Time Factors; D054457:Tissue Scaffolds; D014463:Ultrasonography; D066253:Vascular Remodeling
chemical_list: D016687:Polydioxanone; D011138:Polytetrafluoroethylene; D020780:Matrix Metalloproteinase 9
keywords: Ross operation; aortic remodeling; pulmonary autograft; stress shielding; tissue engineering