Comparison of Natural Mechanical Wave Imaging derived Myocardial Anisotropic Indicator between Healthy Volunteers and Hypertensive Subjects

Mechanical properties of myocardium have shown great clinical potentials in various pathophysiological conditions. However, non-invasive approaches of assessment are limited. Natural mechanical waves, such as shear displacement-induced shear waves and longitudinal displacement-induced pressure waves that are generated by valve closure or the atrial kick, are demonstrated capable of reflecting myocardial stiffness. Different types of natural waves propagating at different velocities along the same path reflects the intrinsic anisotropic property of the myocardial wall. This work is thus to evaluate the myocardial anisotropy (MA) by comparing the propagation characteristics of shear wave and pressure wave, which are observed in the parasternal long axis view (PLAX) and the apical four chamber view (A4C), respectively, that depict the individual propagation of perpendicular displacement components of a same material point in the cardiac wall. Six hypertensive subjects (HT, 47±15 yrs) and six healthy volunteers (HV, 15±11 yrs) were enrolled for comparison and the results have shown that the proposed MA indicators were elevated significantly in HT, probably due to the myocardial interstitial fibrosis formation and a greater afterload increment compared to HV group.