Local myocardial stiffness variations identified by high frame rate shear wave echocardiography

Abstract

Background Shear waves are generated by the closure of the heart valves. Significant differences in shear wave velocity have been found recently between normal myocardium and disease models of diffusely increased muscle stiffness. In this study we correlate in vivo myocardial shear wave imaging (SWI) with presence of scarred tissue, as model for local increase of stiffness. Stiffness variation is hypothesized to appear as velocity variation. Methods Ten healthy volunteers (group 1), 10 hypertrophic cardiomyopathy (HCM) patients without any cardiac intervention (group 2), and 10 HCM patients with prior septal reduction therapy (group 3) underwent high frame rate tissue Doppler echocardiography. The SW in the interventricular septum after aortic valve closure was mapped along two M-mode lines, in the inner and outer layer. Results We compared SWI to 3D echocardiography and strain imaging. In groups 1 and 2, no change in velocity was detected. In group 3, 8/10 patients showed a variation in SW velocity. All three patients having transmural scar showed a simultaneous velocity variation in both layers. Out of six patients with endocardial scar, five showed variations in the inner layer. Conclusion Local variations in stiffness, with myocardial remodeling post septal reduction therapy as model, can be detected by a local variation in the propagation velocity of naturally occurring shear waves.

Automated 3D Velocity Estimation of Natural Mechanical Wave Propagation in the Myocardium

“…In the third example, we observe a complex pattern of wave propagation resulting in a wave projection with two distinct velocity regions. This wave projection in the Mmode image is consistent with previous observations [22], [23] and is documented in [17]. Two wave branches are observed, roughly perpendicular to each other.…”

“…However, increasing the reported metadata may complicate the diagnostic process and reduce clinical practicality. Without incorporating 3D wave visualization and velocity estimation, our understanding of phenomena like non-linear wave projection ( [17], [22], [23]) would be limited. This could restrict the clinical utility of MW imaging.…”

Translating High-Frame-Rate Imaging into Clinical Practice: Where Do We Stand?

“…This results in under-sampling of fast and short-lived events, e.g., in the isovolumic phases of the cardiac cycle and the in accuracy of temporal derivatives of motion and strain, i.e., velocity and strain rate. [57,58] Recently, dedicated high-frame-rate STE algorithms have been developed in order to combine the high temporal resolution of ultrafast ultrasound imaging with the comfort of 2D speckle tracking algorithms. [57,[59][60][61] Joos et al applied STE on high-frame-rate B-mode images at 500 fps that were obtained by special coherent compounding methods based on motion compensation.…”

Relation Between Early Diastolic Mid-Ventricular Flow and Elastic Forces Indicating Aneurysm Formation in Hypertrophic Cardiomyopathy

“…Lastly, emerging echocardiographic methods use high frame rate imaging in determining the myocardial stiffness 24,25 and even the presence of scars. 26 This has yet to be tested in apical forms of HCM.…”