Abstract 246: Echo Particle Image Velocimetry Generates Wall Shear Stress Biomarkers with Higher Accuracy than Doppler: Clinical Studies on 24 Healthy and 12 Tia Subjects

Wall shear stress (WSS) is an important modulator of vascular disease. We assessed the hypothesis that WSS profiles derived from Echo Particle Image Velocimetry (EchoPIV) are characteristic of vascular conditions such as TIA with superior accuracy to Doppler. We obtained ultrasound images of CCA from 24 healthy and 12 TIA subjects. Doppler provided centerline peak velocity and WSS estimate based on parabolic velocity distribution. Velocity profiles measured by EchoPIV varied from patient to patient and within the cardiac cycle. Curve-fitting to a power law function with an exponent term (n-value) showed that in healthy carotid arteries, a blunt velocity profile is present during systole with an average n-value of 5, whereas during diastole a more parabolic profile with an n-value of 2 is present. Therefore, assuming a fully parabolic velocity distribution for WSS estimation, the basis for Doppler velocimetry, introduces a mean error of 48% during diastole and 98% during systole. EchoPIV offers characterization of WSS profiles; time waveform analysis revealed smoother and fewer number of peaks per cycle for healthy and increased flow pulsatality (reverberations) for TIA (Figure). Echo PIV generated means for phase averaged peak velocity (27.95 vs 16.13 cm/s), WSS (6.45 vs 4.65 Dynes/cm2) and flow rate (0.3179 vs 0.2215 L/min) with standard deviations 3.66 vs 2.35, 2.8 vs 1.74 and 0.0723 vs 0.0744 were significantly different between healthy and TIA subjects respectively (all p