Quantitative assessment of left ventricular diastolic stiffness using cardiac shear wave elastography

Objectives-The purpose of this study was to systematically investigate the feasible echocardiographic views for human transthoracic cardiac shear wave elastography (SWE) and the impact of myocardial anisotropy on myocardial stiffness measurements. Methods-A novel cardiac SWE technique using pulse inversion harmonic imaging and time-aligned sequential tracking was developed for this study. The technique can measure the quantitative local myocardial stiffness noninvasively. Ten healthy volunteers were recruited and scanned by the proposed technique 3 times on 3 different days. Results-Seven combinations of echocardiographic views and left ventricular (LV) segments were found to be feasible for LV diastolic stiffness measurements: basal interventricular septum under parasternal short- and long-axis views; mid interventricular septum under parasternal short- and long-axis views; anterior LV free wall under parasternal short- and long-axis views; and posterior LV free wall under a parasternal short-axis view. Statistical analyses showed good repeatability of LV diastolic stiffness measurements among 3 different days from 70% of the participants for the basal interventricular septum and posterior LV free wall short-axis views. On the same LV segment, the mean diastolic shear wave speed measurements from the short-axis view were statistically different from the long-axis measurements: 1.82 versus 1.29 m/s for the basal interventricular septum; 1.81 versus 1.45 m/s for mid interventricular septum; and 1.96 versus 1.77 m/s for the anterior LV free wall, indicating that myocardial anisotropy plays a substantial role in LV diastolic stiffness measurements. Conclusions-These results establish the preliminary normal range of LV diastolic stiffness under different scan views and provide important guidance for future clinical studies using cardiac SWE.