title: Influence of a tilting prosthetic mitral valve orientation on the left ventricular flow - an experimental in vivo magnetic resonance imaging study.
abstract: OBJECTIVE
  Orientation-related monoleaflet mechanical valve flow and velocity studies in the downstream are limited in mitral valve replacement studies.
  
  
  METHODS
  In five sheep, ventricular blood flow was visualized prior to the implantation of a Medtronic Hall tilting valve model. In six sheep, the implant orientation was either anatomical (disc aligned with the anterior leaflet) or anti-anatomical. The mitral subvalvular apparatus was preserved. Sheep were positioned within an 1.5 T field strength MR scanner (Magnetom Sonata; Siemens) to assess time-dependent three dimensional blood flow.
  
  
  RESULTS
  The preoperative ventricular velocity profiles presented negligible individual variances. Streamlines passed homogeneously without any spatial differences in flow velocities into the left ventricle. Starting from the anatomical position, blood entered mainly through the major orifice of the mechanical valve. The single artificial leaflet mimicked the rudder effect of the natural anterior mitral leaflet, preventing blood streaming directly towards the septum. The area with inhomogeneous blood velocities in the ventricle increased but not significantly from the preoperative status. The non-axial inflow not directed directly to the apex converted to a similar helix as observed in the preoperative cases. Anti-anatomical orientation of the prosthesis caused a significant increase in turbulence immediately after passing the mitral prosthesis. The main stream was changed so significantly that the blood flow shifted towards the septum and caused higher velocities of the stream profiles and turbulence apically.
  
  
  CONCLUSIONS
  To achieve optimal hemodynamics, orientation of the mitral tilting valve has to be considered carefully, as has been long known from aortic valve replacement studies.
authors.affiliation: Division of Cardiac Surgery, Medical University Graz, A-8036 Graz, Austria. Heinrich.maechler@meduni-graz.at
authors.forename: Heinrich
authors.initials: H
authors.lastname: Mächler
authors.forename: Gert
authors.initials: G
authors.lastname: Reiter
authors.forename: Mathias
authors.initials: M
authors.lastname: Perthel
authors.forename: Ulrike
authors.initials: U
authors.lastname: Reiter
authors.forename: Peter
authors.initials: P
authors.lastname: Bergmann
authors.forename: Michael
authors.initials: M
authors.lastname: Zink
authors.forename: Rainer
authors.initials: R
authors.lastname: Rienmüller
authors.forename: Joachim
authors.initials: J
authors.lastname: Laas
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D018056:Hemorheology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008943:Mitral Valve / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery*; D012756:Sheep; D016277:Ventricular Function, Left