Characterization of Nonlinear Elasticity of the Carotid Artery Using Pulse Wave Imaging: a Feasibility Study in Hypertensive and Carotid Artery Disease Patients in Vivo

The vascular walls of the carotid artery, as a result of its elastin and collagen content, possess nonlinear elastic behavior. As an individual ages or develops diseases such as hypertension or carotid artery disease, elastin starts to degrade and fragment, resulting in a stiffer vessel. Early identification of vascular remodeling could provide useful information for the diagnosis and treatment of cardiovascular disease. Using Pulse Wave Imaging (PWI), it is possible to estimate the pulse wave velocity (PWV) at two distinct pressure points in the cardiac cycle, end-diastole (ED) and end-systole (ES). The objective of this preliminary study was to investigate the nonlinear elastic behavior of the carotid artery in patients with hypertension (N=11) (HTN) and subjects with both hypertension and mild carotid artery stenosis (N=11)(<40%) in vivo. No significant difference was found for $PWV_{ED}$ between HTN (5.59 ± 1.42 m/s) and <40% (5.45 ± 2.04 m/s) groups (p=.86). $PWV_{ES}$ was increased in the 40% group (9.92 ± 2.50 m/s) compared to the HTN group (8.68 ± 2.98 m/s) (p=.30). The absolute percent difference between $PWV_{ED}$ and $PWV_{ES}, PWV_{\Delta \%}$, was higher in the <40% (96.7 ± 66.9 %) subjects compared to HTN (73.0 ± 61.3 %) (p=.39). The increase in $PWV_{ES}$ and $PWV_{\Delta \%}$ between <40% stenosis and HTN groups may demonstrate changes in the vascular composition and the overall nonlinear mechanical behavior of the carotid artery.