High volume-rate echocardiography for simultaneous imaging of electromechanical activation and cardiac strain of the whole heart in a single heartbeat in humans

Figures

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  Fig 1. Flowchart of electromechanical wave imaging. Ultrasound data acquisition is performed with a 32x32-element array connected to four synchronized Verasonics ultrasound scanners (a). High volume-rate imaging is performed with diverging wave transmission from 5 virtual sources and 3D image reconstruction is performed with delay-and-sum beamforming (b). The myocardium is manually segmented and the atrio-ventricular junction is used to separate the atria from the ventricles (c). Inter-volume axial displacements are estimated using 1-D normalized cross-correlation of the beamformed radiofrequency ultrasound signals (d). Positive displacements (red) indicate motion towards the transducer (at the apex) and negative displacements (blue) indicate motion away from the transducer. Inter-volume axial strains are estimated using a least-squares estimator (e). Positive strains (red) are associated with longitudinal lengthening and negative strains (blue) are associated with longitudinal shortening. Local onset of contraction is determined by the first positive to negative zero-crossing of the temporal axial strain curve after the onset of the P wave (f). The electromechanical activation map is…

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  Fig 2. Volumetric imaging B-modes of volunteer 14 (V14). A) i-iii) The 3D B-mode shell and the B-modes reconstructed along the three imaging planes. B) i-ii) The focused B-modes used for quality assessment and segmentation from the steered and the subaperture transmits, respectively.

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  Fig 3. 3D electromechanical activation maps in 16 healthy volunteers (V1-V16). Red tones indicate early activation and blue tones indicate late activation. A similar activation pattern is observed in all cases: early activation of the right atrium (RA), followed by the left atrium (LA) followed by left (LV) and right ventricles (RV). Posterior (post) and anterior (ant) halves of the heart are shown. The ECG for each volunteer is shown with earliest and latest EWI activation time points indicated with a red and blue dot, respectively.

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  Fig 4. End-systolic 3D ventricular longitudinal strains in 16 healthy volunteers (V1-V16). Ventricular contraction (negative strain) is shown in blue, and lengthening (positive strain) is shown in red. The average global ventricular strain across all volunteers is <VGLS> = -16.6±3.4%. Anterior (ant) and posterior (post) views of the ventricles are shown. The ECG for each volunteer is shown with the beginning and end of systole indicated with a green dot. LV: left ventricle, RV: right ventricle.

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  Fig 5. End-systolic 3D atrial longitudinal strains in 16 healthy volunteers (V1-V16). Atrial relaxation (positive strain) is shown in red, and shortening (negative strain) is shown in blue. The average global atrial strain across all volunteers is <AGLS> = 26.8±6.5%. Anterior (ant) and posterior (post) views of the atria are shown. The ECG for each volunteer is shown with the beginning and end of systole indicated with a green dot. LA: left atrium, RA: right atrium.