title: Influence of twist on vein and PTFE graft hemodynamics: an ex vivo experimental study.
abstract: OBJECTIVE
  In an ex vivo infusion model, the effect of different factors affecting the critical level of twist in vein and PTFE grafts was analysed.
  
  
  METHODS
  University Hospital, Department of Surgery.
  
  
  METHODS
  Saline perfusion of grafts with various diameter and length under constant high (90 ml/min) and low (50 ml/min) flow rates against various peripheral resistance was performed.
  
  
  METHODS
  The pressure changes in the grafts were measured at increasing increments of twisting.
  
  
  RESULTS
  The critical level of twist appears to be dependent on the diameter, length, stretching, status of peripheral resistance, amount of volume flow and the type of graft material, varying between 90 to more than 360 degrees. In vein grafts critical twisting appeared earlier with a decrease in diameter, shortening in length, high peripheral resistance, high flow rate and stretching. PTFE grafts especially with external spiral support were resistant to twist.
  
  
  CONCLUSIONS
  These data suggest that the critical level of graft twist is dependent upon multiple factors and moderate or even high grade twist with especially externally supported PTFE grafts regardless of length and long mobilized vein grafts do not lead to hemodynamic changes. On the other hand total cessation of flow occurs at lower degrees of twist in stretched, short vein grafts.
authors.affiliation: Department of Surgery, University Hospital, Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Karacagil
authors.forename: S
authors.initials: S
authors.lastname: Bowald
authors.forename: B
authors.initials: B
authors.lastname: Almgren
authors.forename: D
authors.initials: D
authors.lastname: Bergqvist
mesh_terms: D001807:Blood Vessel Prosthesis; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D011138:Polytetrafluoroethylene; D012501:Saphenous Vein / Q000502:physiology*; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D011138:Polytetrafluoroethylene