1.6 On-Line Visual Feedback of Parallel Diameter Waveforms Improves Quality of Local Carotid Artery Pulse Wave Velocity Measurement

Background We previously demonstrated that local carotid artery pulse wave velocity (locPWV) can be obtained by high frame-rate multiple M-line ultrasonography. In this study we tested whether on-line display of diameter waveforms improves measurement acceptance rate and reproducibility. Methods and Results In 10 volunteers (age 31 ± 14 yrs) we obtained with and without visual feedback multiple M-line scans of the right common carotid artery. Using the dicrotic notch as fiducial point, locPWV was calculated as the slope of the regression line between M-line positions and time-points of 14 parallel diameter waveforms (Figure). Beat estimates were accepted when regression root mean square error (RMSE) was below 0.07, 0.10 or 0.15 ms, affecting acceptance rate and within-subject repro-ducibility (Table). Overall, on-line feedback significantly improved repro-ducibility by about 50%, enabling good discrimination between subjects: within-subject reproducibility < between-subject SD (Table). LocPWV appeared higher when measured without feedback due to low numbers of estimates in some subjects. Conclusions On-line visual feedback improves the quality of local pulse wave velocity measurements. With feedback, an RMSE threshold of 0.10 ms appears optimal in trading off measurement acceptance rate and reproducibility.