PULSUS TARDUS - ITS CAUSE AND POTENTIAL LIMITATIONS IN DETECTION OF ARTERIAL-STENOSIS

PURPOSE: To determine, with hydrodynamic experiments, the true cause o f pulsus tardus, a Doppler waveform alteration that often occurs dista l to an arterial stenosis. MATERIALS AND METHODS: A flow phantom was c onstructed with a pulsatile pump, interchangeable stenoses of varying degree, and interchangeable poststenotic segments of tubing with vario us degrees of compliance. With the transstenotic pressure drop held co nstant for each stenosis, Doppler waveforms were obtained before and a fter stenosis, while the degree of poststenotic vessel compliance was varied. RESULTS: The degree of pulsus tardus increased as the complian ce of the poststenotic segment of vessel increased, independent of the transstenotic pressure drop. CONCLUSION: Poststenotic pulsus tardus i s caused by the compliance of the poststenotic vessel wall in conjunct ion 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.