title: Experimental evaluation of stent retrievers' mechanical properties and effectiveness.
abstract: BACKGROUND
  Five randomized controlled trials recently appeared in the literature demonstrating that early mechanical thrombectomy in patients with acute ischemic stroke is significantly related to an improved outcome. Stent retrievers are accepted as the most effective devices for intracranial thrombectomy.
  
  
  OBJECTIVE
  To analyze the mechanical properties of stent retrievers, their behavior during retrieval, and interaction with different clots and to identify device features that might correlate with the effectiveness of thrombus removal.
  
  
  METHODS
  All stent retrievers available in France up to June 2015 were evaluated by mechanical and functional tests aimed at investigating the variation of their radial force and their behavior during retrieval. Devices were also tested during in vitro thrombectomies using white and red experimental thrombi produced with human blood. Functional tests and in vitro thrombectomies were conducted using a rigid 3D printed vascular model.
  
  
  RESULTS
  Mechanical tests showed a variation in radial force during retrieval for each stent. A constant radial force during retrieval was related to continuous cohesion over the vessel wall and a higher rate of clot removal efficacy. All stent retrievers failed when interacting with white large thrombi (diameter ≥6 mm).
  
  
  CONCLUSIONS
  None of the tested devices were effective in removing white clots of large diameter (≥6 mm). Constant radial force during retrieval allows constant cohesion to the vessel wall and pressure over the clot; such features allow for a higher rate of clot removal.
authors.affiliation: Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France.
authors.forename: Paolo
authors.initials: P
authors.lastname: Machi
authors.affiliation: Department of Mechanical Engineering, University of Montpellier, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Jourdan
authors.affiliation: Department of Mechanical Engineering, University of Montpellier, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Ambard
authors.affiliation: Department of Mechanical Engineering, University of Montpellier, France.
authors.forename: Cedric
authors.initials: C
authors.lastname: Reynaud
authors.affiliation: Imperial College Healthcare NHS, London, UK.
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Lobotesis
authors.affiliation: Department of Mechanical Engineering, University of Montpellier, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Sanchez
authors.affiliation: Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Bonafé
authors.affiliation: Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Costalat
mesh_terms: D001696:Biomechanical Phenomena; D020878:Device Removal / Q000379:methods / Q000592:standards*; D006801:Humans; D008422:Materials Testing / Q000379:methods / Q000592:standards*; D015607:Stents / Q000592:standards*; D020521:Stroke / Q000601:surgery; D017131:Thrombectomy / Q000295:instrumentation / Q000592:standards; D013927:Thrombosis / Q000601:surgery; D016896:Treatment Outcome
keywords: Stent; Stroke; Thrombectomy