Three-Dimensional Visualization of Velocity Fields Downstream of the St. Jude Medical Aortic Valve Implanted in Pigs
The study of velocity fields downstream of artificial heart valves is an important part of the evaluation since, for example, hemolysis and thrombus formation are considered to be caused by hemodynamic disturbances. Traditionally, velocity profiles have been visualized in one or two diameters over the cross-sectional area, leaving the major part of the flow field unstudied. Therefore, we have developed a method for a three-dimensional visualization of velocity fields downstream of aortic valves in vivo. Using standard cardiopulmonary bypass, size 25 mm ST. JUDE MEDICAL® valves were implanted in the aortic position of 15 pigs weighing approximately 100 kg each. After a short postcardioplegic recovery, the point blood velocities in the ascending aorta were registered with a 1 mm hot-film anemometer needle probe. By computerized drawing technique, a three-dimensional visualization of velocity profiles was made. Throughout one mean heart cycle (obtained by ensemble averaging of the velocity signals) 100 profiles were made. By successive photography of each profile, an animated film was made, giving a dynamic impression of the velocity profile development downstream of the ST. JUDE MEDICAL valve during one heart cycle. In the acceleration phase of systole, the profiles were flat. At top systole, the characteristics of the valve design were recognized. This showed higher velocities over the major orifices and the central opening between the leaflets and low velocities in the hinge areas.
KeywordsVelocity Profile Aortic Valve Heart Valve Heart Cycle Heart Valve Replacement
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