Local carotid pulse wave velocity (cPWV) is a parameter increasingly investigated. The diameter-velocity loop (lnD-V loop) could represent a valid approach for cPWV evaluation, since it requires the use of the ultrasound (US) equipment only. Aim of this study was to develop a fully-automatic system for assessing cPWV which is based on the lnD-V loop and the use of the Wave Intensity Analysis (WIA).

US scans were obtained from 27 healthy subjects (44.1±17.8 years, 44.4% males, BMI 25.5±3.9 kg/m²). Diameter and flow velocity instantaneous values were achieved from B-mode and PW-Doppler images using edge-detection and contour-tracking techniques. Single-beat mean diameter and velocity were calculated, time-aligned using an automatic technique and plotted together providing the lnD-V loop. The WIA, as introduced by Parker in 2009, was performed: the two local maxima (W1 and W2) were used to locate the two reflection-free linear parts of the loop. From the corresponding slopes, early-systolic (PWVes) and late-systolic PWV (PWVls) were calculated; moreover, a carotid stiffness (CS) value was obtained for each subject using Bramwell-Hill equation.

PWVes values (5.16±1.57 m/s) were lower than CS (5.86±1.50 m/s) and PWVls (6.65±3.28 m/s) assessments: the difference was significant for PWVes-PWVls comparison (p<0.05) but not for PWVes-CS and PWVls-CS comparisons. Both PWVes and PWVls values were significantly correlated with CS ones (R=0.90, p<0.001 and R=0.76, p<0.001, respectively).

The proposed approach, based on US images only and the WIA, allows an evaluation of the stiffness in two different phases of the cardiac cycle, reflecting the pressure-dependent changes in cPWV.