title: Tissue storage ex vivo significantly increases vascular fusion bursting pressure.
abstract: BACKGROUND
  Harvested biological tissue is a common medium for surgical device assessment in a laboratory setting; this study aims to differentiate between surgical device performance in the clinical and laboratory environments prior to and following tissue storage. Vascular tissue fusion devices are sensitive to tissue-device temperature gradients, tissue pre-stretch in vivo and tissue water content, each of which can vary during tissue storage. In this study, we compare the results of tissue fusion prior to and following storage using a standardized bursting pressure protocol.
  
  
  METHODS
  Epigastric veins from seven porcine models were subject to identical bursting pressure protocols after fusion. One half of each vein was fused in vivo, harvested and immediately analyzed for burst pressure; the remainder was stored (0.9% Phosphate Buffered Saline, 24h, 4 °C) and then analyzed ex vivo. Histological slides were prepared for qualitative analysis of in versus ex vivo fusions.
  
  
  RESULTS
  Bursting pressures of vessels fused ex vivo (514.7 ± 187.0 mmHg) were significantly greater than those of vessels fused in vivo (310 ± 127.7 mmHg, p = 2.06 E-10). Histological imaging of venous axial cross-sections indicated the lamination of adventitia and media layers ex vivo, whereas in vivo samples consisted only of adventitia.
  
  
  CONCLUSIONS
  These findings suggest that the fusion of porcine venous tissue ex vivo may overestimate the clinical performance of fusion devices. Prior work has indicated that increased tissue hydration and the lamination of tissue layers both positively affect arterial fusion bursting pressures. The bursting pressure increase observed herein may therefore be due to storage-induced alterations in tissue composition and mechanics of the fusion interface. While harvested tissue provides an accessible medium for comparative study, the fusion of vascular tissue in vivo may avoid storage-induced biomechanical alterations and is likely a better indicator of fusion device performance in a clinical setting.
authors.affiliation: Department of Mechanical Engineering, University of Colorado at Boulder, 427 UCB, 1111 Engineering Drive, Boulder, CO, 80309-0427, USA, James.Cezo@colorado.edu.
authors.forename: James D
authors.initials: JD
authors.lastname: Cezo
authors.forename: Eric A
authors.initials: EA
authors.lastname: Kramer
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Schoen
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Ferguson
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Taylor
authors.forename: Mark E
authors.initials: ME
authors.lastname: Rentschler
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004867:Equipment Design; D066298:In Vitro Techniques; D008026:Ligation / Q000295:instrumentation; D008953:Models, Anatomic; D011312:Pressure; D013523:Surgical Equipment; D013552:Swine; D014021:Tissue Preservation; D014680:Veins