Studies by pulsed Doppler ultrasonography of velocity fields downstream of graded stenoses on the abdominal aorta in pigs.

Abstract

To investigate local hemodynamics downstream of arterial stenoses, a perivascular five-element Doppler ultrasound transducer was used for registration of one-dimensional velocity profiles and estimation of Reynolds (turbulent) normal stresses downstream of smooth, graded stenoses on the abdominal aorta in six 90 kg pigs. Blood velocities were registered by a 10 MHz pulsed Doppler velocimeter that used a modified zero-crossing detector with an upper -3 dB cutoff frequency of 200 Hz. Signal analysis included ensemble averaging, turbulence analysis, and dimensional visualization of velocity profiles. Velocity profiles downstream of minor (< or = 40%) and moderate (40% to 65%) stenoses were skewed with the highest systolic velocities toward the anterior vessel wall and diastolic flow reversal occasionally present at the posterior vessel wall. Immediately downstream of severe (> or = 65%) stenoses a prominent poststenotic jet and systolic recirculation zones were present. Further downstream, vortices and eddies dominated the flow field. Reynolds normal stresses were highest at locations in the velocity field with high-velocity gradients corresponding to the parajet zone. The present study demonstrated that pulsed Doppler ultrasonography can provide detailed and quantitative information of flow phenomena such as jetlike flow, vortices, and recirculation zones in a poststenotic flow field in the abdominal aorta.