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Pulsus tardus: its cause and potential limitations in detection of arterial stenosis
R O Bude1, J M Rubin, J F Platt
1Department of Radiology, University of Michigan Medical Center, Ann Arbor 48109-0326.
Purpose:
To determine, with hydrodynamic experiments, the true cause of pulsus tardus, a Doppler waveform alteration that often occurs distal to an arterial stenosis.
Materials And Methods:
A flow phantom was constructed with a pulsatile pump, interchangeable stenoses of varying degree, and interchangeable poststenotic segments of tubing with various degrees of compliance. With the transstenotic pressure drop held constant for each stenosis, Doppler waveforms were obtained before and after stenosis, while the degree of poststenotic vessel compliance was varied.
Results:
The degree of pulsus tardus increased as the compliance of the poststenotic segment of vessel increased, independent of the transstenotic pressure drop.
Conclusion:
Poststenotic pulsus tardus is caused by the compliance of the poststenotic vessel wall in conjunction with the stenosis, which produces the tardus effect by damping the high-frequency components of the arterial waveform. This information will allow prediction of conditions that may produce false-positive or false-negative results when the tardus phenomenon is used to predict substantial upstream stenosis.