Local myocardial stiffness variations identified by high frame rate shear wave echocardiography
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(2020) 18:40
RESEARCH
Open Access
Local myocardial stiffness variations identified by high frame rate shear wave echocardiography Mihai Strachinaru1* , Johan G. Bosch2, Arend F. L. Schinkel1, Michelle Michels1, Lida Feyz1, Nico de Jong2, Marcel L. Geleijnse1 and Hendrik J. Vos2
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. Keywords: Naturally-occurring shear waves, Elastography, High frame rate tissue Doppler, Septal reduction
Introduction Stiffness can be estimated in vivo by measuring the propagation velocity of externally induced shear waves travelling through tissue [1], the general principle being that shear waves travel faster in stiffer materials. Shear wave echography is an emerging diagnostic tool in radiology, capable of detecting relatively subtle changes in tissue elasticity. However, in cardiology, the dynamic stiffness of the myocardium over the heart cycle, as well * Correspondence: [email protected] 1 Erasmus MC Rotterdam, Cardiology, Postbus 2040, 3000, CA, Rotterdam, The Netherlands Full list of author information is available at the end of the article
as the limited acoustic access to the organ, present technical challenges to the implementation of cardiac elastography that are only addressed recently [2–7]. One technique relies on generating shear waves in the myocardium with an external source and detecting their propagation [8–10]. This approach is limited by the need for special equipment in order to induce and track these waves. Another technique, exploited in the current study, detects naturally occurring shear waves generated by the closing of the valves [3, 5, 11–14]. Studies have demonstrated that the global stiffness of
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