Doppler ultrasonographic features of thoracic limb arteries in clinically normal horses

Objectives-To determine blood flow velocities and indices from spectral wav eforms obtained by use of Doppler ultrasonography of thoracic limb arteries of horses and to assess interobserver and patient variability associated w ith the technique. Animals-9 clinically normal adult horses. Procedure-Left thoracic limb arteries of 8 nonsedated horses were examined at 5 sites by use of pulsed-wave Doppler ultrasonography to determine a ran ge of values for peak systolic, end diastolic, and mean velocities and resi stive and pulsatility indices. Interobserver and patient variabilities were determined by 2 operators repeating similar measurements on 1 horse 8 time s at weekly intervals. Results-A range of values for each variable measured at the 5 selected site s was obtained. For each variable, strong positive correlations (R greater than or equal to 0.7) were detected for > 70% of the site-to-site compariso ns made (excluding the coronary band). Among horses, resistive index varied least, whereas over time, mean velocity varied least. Waveform characteris tics were consistent with resistive (n = 5) or nonresistive (4) patterns. I n the single-horse experiment, waveform characteristics were consistent thr oughout the 8 weeks, and operator effects were not detected. Conclusions and Clinical Relevance-Doppler ultrasonography of no one site r esulted in more reliable measurements of blood flow characteristics in thor acic limb arteries of horses. Mean velocity and resistive index were the le ast variable measurements made. Pulsed-wave Doppler ultrasonography may be a useful technique for evaluating diseases that alter normal thoracic limb arterial blood flow in horses.