Ultrasound Time-Harmonic Elastography of the Aorta: Effect of Age and Hypertension on Aortic Stiffness.

Abstract

The aim of this study was to investigate ultrasound time-harmonic elastography for quantifying aortic stiffness in vivo in the context of aging and arterial hypertension. Seventy-four participants (50 healthy participants and 24 participants with long-standing hypertension) were prospectively included between January 2018 and October 2018, and underwent ultrasound time-harmonic elastography of the upper abdominal aorta. Compound maps of shear-wave speed (SWS) as a surrogate of tissue stiffness were generated from multifrequency wave fields covering the full field-of-view of B-mode ultrasound. Blood pressure and pulse wave velocity were measured beforehand. Interobserver and intraobserver agreement was determined in 30 subjects. Reproducibility of time-harmonic elastography was assessed in subgroups with repeated measurements after 20 minutes and after 6 months. Linear regression analysis, with subsequent age adjustment of SWS obtained, receiver operating characteristic analysis, and intraclass correlation coefficients (ICCs) were used for statistical evaluation. Linear regression analysis revealed a significant effect of age on SWS with an increase by 0.024 m/s per year (P < 0.001). Age-adjusted SWS was significantly greater in hypertensives (0.24 m/s; interquartile range [IQR], 0.17-0.40 m/s) than in healthy participants (0.07 m/s; IQR, -0.01 to 0.06 m/s; P < 0.001). A cutoff value of 0.15 m/s was found to differentiate best between groups (area under the receiver operating characteristic curve, 0.966; 95% confidence interval, 0.93-1.0; P < 0.001; 83% sensitivity and 98% specificity). Interobserver and intraobserver variability was excellent (ICC, 0.987 and 0.937, respectively). Reproducibility was excellent in the short term (ICC, 0.968; confidence interval, 0.878-0.992) and good in the long term (ICC, 0.844; confidence interval, 0.491-0.959). Ultrasound time-harmonic elastography of the upper abdominal aorta allows quantification of aortic wall stiffness in vivo and shows significantly higher values in patients with arterial hypertension.