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Eur J Cardiothorac Surg 1999;16:300-305
© 1999 Elsevier Science NL

Prosthetic heart valve evaluation by magnetic resonance imaging

^a Department of Cardiothoracic and Vascular Surgery, Skejby Sygehus, Aarhus University Hospital, 8200 Aarhus, N., Denmark
^b Institute of Experimental Clinical Research, Aarhus University Hospital, 8200 Aarhus, N., Denmark
^c MR Center, Skejby Sygehus, Aarhus University Hospital, 8200 Aarhus, N., Denmark
^d Institute of Biomedical Engineering, University and E.T.H., Zürich, Switzerland

Corresponding author. Tel.: +45-89-49-5480; fax +45-89-49-6016
e-mail: skejmh{at}aau.dk

Objective: To evaluate the potential of magnetic resonance imaging (MRI) for evaluation of velocity fields downstream of prosthetic aortic valves. Furthermore, to provide comparative data from bileaflet aortic valve prostheses in vitro and in patients. Methods: A pulsatile flow loop was set up in a 7.0 Tesla MRI scanner to study fluid velocity data downstream of a 25 mm aortic bileaflet heart valve prosthesis. Three dimensional surface plots of velocity fields were displayed. In six NYHA class I patients blood velocity profiles were studied downstream of their St. Jude Medical aortic valves using a 1.5 Tesla MRI whole-body scanner. Blood velocity data were displayed as mentioned above. Results: Fluid velocity profiles obtained from in vitro studies 0.25 valve diameter downstream of the valve exhibited significant details about the cross sectional distribution of fluid velocities. This distribution completely reflected the valve design. Blood velocity profiles in humans were considerably smoother and in some cases skewed with the highest velocities toward the anterior-right ascending aortic wall. Conclusion: Display and interpretation of fluid and blood velocity data obtained downstream of prosthetic valves is feasible both in vitro and in vivo using the MRI technique. An in vitro model with a straight tube and the test valve oriented orthogonally to the long axis of the test tube does not entail fluid velocity profiles which are compatible to those obtained from humans, probably due to the much more complex human geometry, and variable alignment of the valve with the ascending aorta. With the steadily improving quality of MRI scanners this technique has significant potential for comparative in vitro and in vivo hemodynamic evaluation of heart valves.

Key Words: Prosthetic heart valve • Magnetic resonance imaging • Hemodynamics • In vitro • Human