Developing technologies to assess vascular ageing: a roadmap from VascAgeNet

Figures

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  Figure 1.. The four areas of the Roadmap. Source: Reproduced from Servier Medical Art. CC BY 4.0.

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  Figure 2.. (a) Standard longitudinal B-mode US image of a common carotid artery processed by software based on a contour tracking algorithm measuring diameter and intima media thickness (IMT). (b) Measurements of instantaneous diameter. (c) Applanation tonometry for carotid blood pressure estimation, calibrated through brachial pressure assessment, that, combined with the US derived analysis, provides elastic parameters.

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  Figure 3.. Main limitations and possible solutions to meet challenges related to the application of US techniques in clinical practice for vascular ageing assessment.

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  Figure 4.. Two-site oscillometric arterial stiffness assessment by calculating the brachial–ankle pulse wave velocity (baPWV) through the measurement of the transit time between the brachial artery and tibial artery through the oscillometric amplitude. Definitions: BP—blood pressure; baPWV—brachial–ankle pulse wave velocity.

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  Figure 5.. Single-site oscillometric arterial stiffness assessment method by the combination of cuff oscillometry, pulse wave analysis and validated algorithms including covariates such as age and systolic blood pressure. Definitions: oPWA—oscillometric pulse wave analysis; oPWV—oscillometric pulse wave velocity; SBP—brachial systolic blood pressure.

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  Figure 6.. Applanation tonometry. Left panel: transcutaneous arterial tonometry in radial artery. Right panel: applanation tonometry principle: a circular structure with a given pressure inside (artery) is flattened; in this way circumferential pressures are equalized and the sensor records the intra-arterial pressure (P). Tensile forces (T) are perpendicular to pressure vectors. Lower panel: raw recording of a radial applanation tonometry sampled at 1 kHz.

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  Figure 7.. Assessing vascular ageing from contact photoplethysmography. Definitions: PPG—photoplethysmography; PTT—pulse transit time; PAT—pulse arrival time; ECG—electrocardiogram. Adapted from Charlton et al (2022b). CC BY 4.0. Adapted from Charlton et al (2018). © 2018 Institute of Physics and Engineering in Medicine. CC BY 3.0. Adapted from Charlton et al (2022a). CC BY 4.0.

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  Figure 8.. Imaging photoplethysmography (iPPG) waveform extraction and analysis: facial images are captured by a colour camera. Then the forehead is selected as region of interest (ROI). The raw iPPG signal is extracted from the ROI using spatial averaging. Before extracting the waveform, the signal is smoothed and filtered. Three waveform features can be computed: (a) temporal, (b) areas and (c) derivatives and amplitude features. These features are related to heart rate, blood pressure, vascular ageing and arterial stiffness. Adapted from Djeldjli et al (2021), Copyright (2021), with permission from Elsevier.

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  Figure 9.. Some circulating biomarkers with the highest potential for early detection and diagnosis of cardiovascular disease and vascular ageing. Adapted from Gopcevic et al (2021). CC BY 4.0.

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  Figure 10.. The chronological age, the vascular age calculated based on the Systematic COronary Risk Evaluation (Vasc Age SCORE) and the vascular age calculated based on Framingham risk score (Vasc Age FRS) of the study population. Data are presented as median (minimal and maximal values in error bars). *p < 0.05 compared with Chronological Age; #p < 0.05 compared with Vasc Age SCORE. Adapted from Gyöngyösi et al (2021). CC BY 4.0.

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  Figure 11.. (Left) Current challenges using in vivo human data to develop technologies to assess vascular ageing from pulse wave (PW) signals. (Right) Advantages offered by synthetic data to overcome these challenges. * Other properties may change concurrently. ** Individual properties can be altered independently of each other.

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  Figure 12.. Examples of synthetic PW signals. (a) Arterial network used to simulate the signals. (b) The PPG at the finger changes with ageing, allowing the study of PPG-derived vascular ageing indices. (c) Central and peripheral blood pressure (BP) waves for evaluating the estimation of the former from the latter, across different age groups. Adapted from Charlton et al (2019). CC BY 4.0. (d) Cardiac cycle-averaged diameter (D) and flow velocity (U) during flow-mediated dilation (FMD). Adapted from Jin et al (2020). CC BY 4.0.