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Eur J Cardiothorac Surg 2007;32:102-107. doi:10.1016/j.ejcts.2007.02.038
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

Influence of a tilting prosthetic mitral valve orientation on the left ventricular flow — an experimental in vivo magnetic resonance imaging study

^a Division of Cardiac Surgery, Medical University Graz, A-8036 Graz, Austria
^b Division of Radiology, Medical University Graz, Austria
^c Division of Cardiac Surgery, Bad Bevensen, Germany
^d Department of Anesthesiology, Medical University Graz, Austria
^e Siemens Medical, Graz, Austria

Received 8 November 2006; received in revised form 10 February 2007; accepted 15 February 2007.

^_* Corresponding author. Tel.: +43 316 385 4671; fax: +43 316 385 4672. (Email: Heinrich.maechler{at}meduni-graz.at).

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.

Key Words: Mitral valve prosthesis • Orientation • Intra-ventricular flow • Magnetic resonance imaging

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