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Eur J Cardiothorac Surg 2004;26:747-753
© 2004 Elsevier Science NL

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

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

Received 13 January 2004; received in revised form 7 June 2004; accepted 7 June 2004.

^* Corresponding author. Tel.: +43-316-385-4671; fax: +43-316-385-4672. (E-mail: heinrich.maechler{at}uni-graz.at).

Objective: Orientation-related bileaflet mechanical valve flow and velocity studies in the downstream area are limited in mitral valve replacement studies. Methods: In five sheep, ventricular blood flow was visualized prior to the implantation of a mitral Edwards Mira Bileaflet Mechanical Valve Model 9600. The implant orientation was either anatomic, with a 45° rotation, or anti-anatomic, with a 90° rotation. Sheep were positioned within an 1.5T field strength MR scanner (Magnetom Sonata; Siemens) to assess time-dependent three-dimensional blood flow velocities displayed as color-encoded vectors. Results: The preoperative ventricular velocity profiles presented negligible individual variances. Streamlines passed homogeneously without any spatial differences into the left ventricle. Starting from the anatomical position, the areas with inhomogeneous and accelerated local blood velocities increased in comparison to the preoperative status. Rotating the prosthesis until it was in a 45° position caused a significant increase in turbulence immediately downstream; fluids stagnated longer at the apex. In the anti-anatomic orientation, mean velocities decreased. In all three positions, but less so in the anatomical position, the flow pattern of the blood helix at the apex was disturbed. The intraventricular flow patterns between protheses in the three orientations were, however, not significant when compared to the differences between physiologic intraventricular flow and any of the postoperative measurements. Conclusions: To achieve optimal hemodynamics, rotation of the mitral valve has to be considered carefully, as has long been known from aortic valve replacement studies. To this end, a method for qualitative assessment of left ventricular blood flow patterns was developed.

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