Parasternal Versus Apical View in Cardiac Natural Mechanical Wave Speed Measurements

Abstract

Shear wave speed measurements can potentially be used to noninvasively measure myocardial stiffness to assess the myocardial function. Several studies showed the feasibility of tracking natural mechanical waves induced by aortic valve closure in the interventricular septum, but different echocardiographic views have been used. This article systematically studied the wave propagation speeds measured in a parasternal long-axis and in an apical four-chamber view in ten healthy volunteers. The apical and parasternal views are predominantly sensitive to longitudinal or transversal tissue motion, respectively, and could, therefore, theoretically measure the speed of different wave modes. We found higher propagation speeds in apical than in the parasternal view (median of 5.1 m/s versus 3.8 m/s, p < 0.01, n = 9). The results in the different views were not correlated (r = 0.26, p = 0.49) and an unexpectedly large variability among healthy volunteers was found in apical view compared with the parasternal view (3.5-8.7 versus 3.2-4.3 m/s, respectively). Complementary finite element simulations of Lamb waves in an elastic plate showed that different propagation speeds can be measured for different particle motion components when different wave modes are induced simultaneously. The in vivo results cannot be fully explained with the theory of Lamb wave modes. Nonetheless, the results suggest that the parasternal long-axis view is a more suitable candidate for clinical diagnosis due to the lower variability in wave speeds.

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

“…Similar to the aortic valve closure, also the mitral valve closure generates a wave pattern that might appear in the TDI map. However, in previous studies [35,36], the feasibility of the mitral shear wave detection was significantly lower than the aortic. Furthermore, a large number (8/10) of surgical reduction patients also received mitral valve reconstruction.…”

A direct comparison of natural and acoustic-radiation-force-induced cardiac mechanical waves

“…transversal with respect to the IVS in parasternal view) 41 , whereas the exact orientation of the force for natural SWE is unknown. However, the force after AVC will probably not be purely transversally oriented because both a transversal (parasternal view) as well as a longitudinal component (apical view) of tissue motion in the IVS has been measured in an earlier study 33 . Second, the temporal and spatial characteristics of the excitation source are completely different, which might affect the spectral content of the wave 42 .…”

“…For example, for ARF-induced SWs, it is known that measuring their propagation along the myocardial fiber orientation at mid-IVS (as done in a parasternal short-axis view) results in a higher SW propagation speed than measuring across the fiber orientation (as done in a parasternal long-axis view) 27 . Also, natural SWs measured in parasternal or apical view can give various SW propagation speeds due to a difference in the tracked tissue-motion component 33 . Interpretation of cardiac SWE data is thus complex, and it is unsure how these different SW measurements are related to each other and to the mechanical properties of the heart.…”

Tapering of the interventricular septum can affect ultrasound shear wave elastography: An in vitro and in silico study

“…Finally, it is worth noting that the results found for the A0 curve are relevant for the S0 mode as well: in the frequency range typical of natural waves, the S0 mode shows a dispersion comparable to (and even slightly larger than) the one of A0, albeit opposite in sign. A visual comparison of A0 and S0 in a (flat) plate submerged in water, for frequencies relevant to the present work, can be found in a recent work by Keijzer et al 45 From a theoretical point of view, it is incorrect to talk about Lamb dispersion curves in plates of varying thickness, as these curves are defined for flat plates. Regardless, as a practical attempt to extract the shear modulus from wave measurements, it may still be useful to fit the known curves of a fluid-loaded flat plate to the f-k data.…”