Shear Wave Elastography Using High-Frame-Rate Imaging in the Follow-Up of Heart Transplantation Recipients

Abstract

Objectives: The purpose of this study was to investigate whether propagation velocities of naturally occurring shear waves (SWs) at mitral valve closure (MVC) increase with the degree of diffuse myocardial injury (DMI) and with invasively determined LV filling pressures as a reflection of an increase in myocardial stiffness in heart transplantation (HTx) recipients.

Background: After orthotopic HTx, allografts undergo DMI that contributes to functional impairment, especially to increased passive myocardial stiffness, which is an important pathophysiological determinant of left ventricular (LV) diastolic dysfunction. Echocardiographic SW elastography is an emerging approach for measuring myocardial stiffness in vivo. Natural SWs occur after mechanical excitation of the myocardium, for example, after MVC, and their propagation velocity is directly related to myocardial stiffness, thus providing an opportunity to assess myocardial stiffness at end-diastole.

Methods: A total of 52 HTx recipients who underwent right heart catheterization (all) and cardiac magnetic resonance (CMR) (n = 23) during their annual check-up were prospectively enrolled. Echocardiographic SW elastography was performed in parasternal long axis views of the LV using an experimental scanner at 1,135 ± 270 frames per second. The degree of DMI was quantified with T1 mapping.

Results: SW velocity at MVC correlated best with native myocardial T1 values (r = 0.75; p < 0.0001) and was the best noninvasive parameter that correlated with pulmonary capillary wedge pressures (PCWP) (r = 0.54; p < 0.001). Standard echocardiographic parameters of LV diastolic function correlated poorly with both native T1 and PCWP values.

Conclusions: End-diastolic SW propagation velocities, as measure of myocardial stiffness, showed a good correlation with CMR-defined diffuse myocardial injury and with invasively determined LV filling pressures in patients with HTx. Thus, these findings suggest that SW elastography has the potential to become a valuable noninvasive method for the assessment of diastolic myocardial properties in HTx recipients.

Keywords: heart transplantation; high-frame-rate echocardiography; myocardial stiffness; shear wave.