High-Frame-Rate Echocardiography: A New Frontier in Noninvasive Functional Assessment

Figures

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  Figure 3. Representative example illustrating high-frame-rate mechanical activation analysis in a healthy volunteer: (a) scaled segmental left ventricular strain-rate curve from the mid inferior segment (segment 10); (b) corresponding ECG; and (c) left ventricular mechanical activation map, with the mid inferior segment highlighted (*). The color scale represents the time delay between the onset of QRS (green line) and the first significant negative deflection of the strain rate curve of the respective myocardial segment (red line). Adapted from Safarzadeh et al. [46].

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  Figure 4. Overview of principal modalities used in mechanical wave propagation imaging for myocardial stiffness assessment. (Top left): natural shear waves generated after mitral valve closure. (Top right): active shear waves induced by focused ultrasound excitation. (Bottom left): time harmonic elastography using external vibration for stiffness mapping. (Bottom right): stretch waves or longitudinal waves propagating from base to apex during ventricular filling. Adapted from Caenen et al. [62], Villemain et al. [66], Meyer and Wellge et al. [69], and Pislaru et al. [57], respectively.

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  Figure 5. Adapted illustration of left ventricular vortices visualized with high-frame-rate blood speckle tracking. In the healthy heart (left), vortices are compact and apically centered, indicating efficient filling, whereas in congenital heart disease (right), they appear enlarged or displaced due to altered ventricular geometry and loading. LA = left atrium; LV = left ventricle; MV = mitral valve; RA = right atrium; RV = right ventricle. Adapted from Marchese et al. [110].

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  Figure 1. Central illustration highlighting the advantages of high-frame-rate echocardiography over conventional imaging, its main clinical applications, and key technical challenges.

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  Figure 2. Conceptual illustration of strategies used to achieve high-frame-rate ultrasound imaging. Dashed lines represent imaging events. (a) Direct approaches: more frames are acquired within a given time interval by modifying the transmit–receive sequence. (b) Indirect approaches: the effective frame rate is increased through post-processing of previously acquired frames. In this schematic, sparsely sampled frames from successive cardiac cycles are retrospectively reordered and combined to reconstruct a sequence with higher effective temporal resolution. Arrows indicate imaging events acquired in different cardiac cycles that are reused and reassigned to new temporal positions in the reconstructed sequence.