STUDIES BY PULSED DOPPLER ULTRASONOGRAPHY OF VELOCITY-FIELDS DOWNSTREAM OF GRADED STENOSES ON THE ABDOMINAL-AORTA IN PIGS

Purpose: To investigate local hemodynamics downstream of arterial sten oses, a perivascular five-element Doppler ultrasound transducer was us ed for registration of one-dimensional velocity profiles and estimatio n of Reynolds (turbulent) normal stresses downstream of smooth, graded stenoses on the abdominal aorta in six 90 kg pigs. Methods: Blood vel ocities were registered by a 10 MHz pulsed Doppler velocimeter that us ed a modified zero-crossing detector with an upper - 3 dB cutoff frequ ency of 200 Hz. Signal analysis included ensemble averaging, turbulenc e analysis, and dimensional visualization of velocity profiles. Result s: Velocity profiles downstream of minor (less than or equal to 40%) a nd moderate (40% to 65%) stenoses were skewed with the highest systoli c velocities toward the anterior vessel wall and diastolic flow revers al occasionally present at the posterior vessel wall. Immediately down stream of severe (greater than or equal to 65%) stenoses a prominent p oststenotic jet and systolic recirculation zones were present. Further downstream, vortices and eddies dominated the flow held. Reynolds nor mal stresses were highest at locations in the velocity held with high- velocity gradients corresponding to the parajet zone. Conclusions: The present study demonstrated that pulsed Doppler ultrasonography can pr ovide detailed and quantitative information of flow phenomena such as jetlike flow, vortices, and recirculation zones in a poststenotic flow field in the abdominal aorta.