Estimation of In-Vivo Mechanical Properties of Aortic Wall in Left Ventricular Hypertrophy Patients

Aortic wall properties such as aortic stiffness has emerged as a good tool for risk stratification because it has been linked to increased risk of heart disease. Thus, this preliminary study aims to estimate the in-vivo aortic wall properties between healthy and hypertrophy heart disease patients. Cine magnetic resonance (CMR) images of six human subjects i.e. two healthy subjects, two hypertrophy cardiomyopathy (HCM) and two hypertensive heart disease (HHD) patients were obtained. Based on the CMR images, aortic wall deformation at the ascending, arch and descending aorta were acquired at both systolic and diastolic phases. The stress and strain were then calculated and Mooney-Rivlin and Ogden hyperelastic material models were adopted to estimate the material constants at the respective regions in both phases. All the subjects were further categorized into two age groups to compare the effects of aging. Our results show that five parameters Mooney-Rivlin model has better fit of stress-strain data while the aortic wall stress is most prominent in the ascending aorta region. The greatest systolic aortic stress at the ascending aorta was found in HHD patients (238.17 kPa) followed by HCM patients (173.61 kPa) and lowest in healthy subjects (141.06 kPa). For aortic strain, an inverse trend was observed among the subjects. The older age group demonstrated a smaller aortic strain (22.60%) compared to the slightly younger age group (38.73%). This study shows that the estimated aortic wall stiffness in HHD and HCM are greater than the healthy subjects while the effect of aging is more prominent on aortic wall stiffness.