Abstract
BackgroundShear 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.MethodsTen 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.ResultsWe 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.ConclusionLocal 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.
Highlights
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
Significant differences in shear wave velocity have been observed between normal myocardium and disease models of increased muscle stiffness, like amyloidosis [11], hypertrophic cardiomyopathy (HCM) [9, 10, 14, 16] and severe hypertension [17]
Ultrasound 2D, 3D and deformation imaging can detect localized intramyocardial variations and have been extensively validated in previous studies [21, 22, 24,25,26]. They were used as landmark references for shear wave imaging (SWI), for confirmation of the presence of local myocardial abnormalities in the investigated segments, making sure that scar tissue as visualized on Magnetic resonance imaging (MRI) (Fig. 1) was present in the 2D echocardiographic imaging plane used for SWI in each individual patient
Summary
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. Significant differences in shear wave velocity have been observed between normal myocardium and disease models of increased muscle stiffness, like amyloidosis [11], hypertrophic cardiomyopathy (HCM) [9, 10, 14, 16] and severe hypertension [17]. These studies focused on diffuse diseases of the myocardium, comparing shear wave velocity in pathological versus normal myocardium.
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