New indices of arterial stiffness measured from longitudinal motion of common carotid artery in relation to reference methods, a pilot study.

BACKGROUND: Longitudinal wall motion of carotid artery is a useful but challenging parameter to measure. In this study, we tested our previously published motion tracking algorithm and validated our method against applanation tonometry measurements.

METHODS AND RESULTS: We measured the two-dimensional carotid artery wall motion from 19 healthy subjects and, as a reference, performed applanation tonometry measurements in parallel with the ultrasound study. The results show that peak velocities (R = -0·484; P<0·05) and accelerations (R = -0·524; P<0·05) of the longitudinal motion between intima and adventitia layers exhibit a greater correlation with the arterial stiffness parameters, for example the augmentation index than the corresponding amplitude of the longitudinal motion (R = -0·132; P>0·05). The amplitudes of the longitudinal motion, between intima and adventitia, are related more to the physical size of the subject, as they correlated significantly with the height (R = 0·597; P<0·01) and weight (R = 0·562; P<0·05) of the subject as well as the cross-sectional dimension of the measured artery (R = 0·611; P<0·01). Furthermore, two new indices have been introduced, Polydeg and RAlength, with which to study the shape of the longitudinal motion curve; both parameters displayed significant correlation with arterial stiffness, for example augmentation index (R = 0·468; P<0·05 and R = 0·609; P<0·01, respectively).

CONCLUSIONS: The new longitudinal motion parameters presented here displayed clear potential to be used as novel stiffness indices.