Prosthetic heart valve evaluation by magnetic resonance imaging

Objective: To evaluate the potential of magnetic resonance imaging (MRI) fo r evaluation of velocity fields downstream of prosthetic aortic valves. Fur thermore, to provide comparative data from bileaflet aortic valve prosthese s 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 ao rtic bileaflet heart valve prosthesis. Three dimensional surface plots of v elocity fields were displayed. In six NYHA class I patients blood velocity profiles were studied downstream of their St. Jude Medical aortic valves us ing 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 di stribution completely reflected the valve design. Blood velocity profiles i n humans were considerably smoother and in some cases skewed with the highe st velocities toward the anterior-right ascending aortic wall. Conclusion: Display and interpretation of fluid and blood velocity data obtained downst ream of prosthetic valves is feasible both in vitro and in vivo using the M RI technique. An in vitro model with a straight tube and the test valve ori ented orthogonally to the long axis of the test tube does not entail fluid velocity profiles which are compatible to those obtained from humans, proba bly 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 vi tro and in vivo hemodynamic evaluation of heart valves. (C) 1999 Elsevier S cience B.V. All rights reserved.