In vitro color flow, pulsed and continuous wave Doppler ultrasound masking of flow by prosthetic valves.
On the hypothesis that Doppler ultrasound fails to penetrate prosthetic valves, an in vitro flow simulation system was constructed in a large water tank. Conventional pulsed, continuous wave and Doppler color flow systems were used to detect flow in tubing placed diagonally within the water and maintained by a continuous pump. After control periods of flow detection within the tubing, six different prosthetic valves were interposed on a stage between the transducer and the tubing. In comparison with control measurements, detection of flow within the tubing was impossible when the Doppler beam traversed the central occluding ball of the Starr-Edwards Silastic prosthesis by any modality. Marked reduction in the detection of the Doppler signal was noted for the Starr-Edwards stellite prosthesis with only slight improvement in the ability to detect the flow signals through the central occluding discs of the Björk-Shiley, Hall-Kastor and St. Jude valves. In distinction to the other valves, the ability of Doppler ultrasound to detect flow behind the cusps of the Carpentier-Edwards heterograft was similar to that during the control period. An understanding of flow masking should improve the clinical utility of Doppler methods for investigating prosthetic valve dysfunction.
Sprecher, DL; Adamick, R; Adams, D; Kisslo, J
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