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 reproducibility (Table). Overall, on-line feedback significantly improved reproducibility 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.