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Aims Peripheral arterial disease (PAD) is a major public health burden requiring more intensive population screening. Ankle brachial index (ABI) using arm and ankle cuffs is considered as the reference method for the detection of PAD. Although it requires a rigorous methodology by trained operators, it remains time-consuming and more technically difficult in patients with diabetes due to mediacalcosis. Techniques based on the study of hemodynamic, such as the systolic rise time (SRT), appear promising but need to be validated. We retrospectively compared the reliability and accuracy of SRT using a photoplethysmography (PPG) technique to the SRT measured by ultrasound doppler (UD) in PAD patients diagnosed with the ABI (137 patients, 200 lower limbs). Methods and results There was a significant correlation between SRT measured with UD (SRTud) compared with that with PPG (SRTppg, r = 0.25; P = 0.001). Best correlation was found in patients without diabetes (r = 0.40; P = 0.001). Bland and Altman analysis showed a good agreement between the SRTud and SRTppg. In contrast, there was no significant correlation between UD and PPG in diabetes patients. Furthermore, patients with diabetes exhibited a significant increase of SRTppg (P = 0.02) compared with patients without diabates but not with the SRTud (P = 0.18). The SRTppg was significantly linked to the arterial velocity waveforms, the type of arterial lesion but not vascular surgery revascularization technique. Conclusion This monocentric pilot study shows that SRT measured with the PPG signal reliably correlates with SRT recorded with UD. The PPG is an easy to use technique in the hand of non-expert with a potential interest for general screening of PAD, especially in diabetes patients, due to its ease to use.

Arterial stiffness (AS), as assessed via pulse wave velocity (PWV), is a major biomarker for cardiovascular risk assessment in patients with chronic kidney disease (CKD). However, the mechanisms responsible for the changes in PWV in the presence of kidney disease are not yet fully elucidated. In the present study, we aimed to investigate the direct effects attributable to biomechanical changes in the arterial tree caused by staged renal removal, independent of any biochemical or compensatory effects. Particularly, we simulated arterial pressure and flow using a previously validated one-dimensional (1-D) model of the cardiovascular system with different kidney configurations: two kidneys (2KDN), one single kidney (1KDN), no kidneys (0KDN), and a transplanted kidney (TX) attached to the external iliac artery. We evaluated the respective variations in blood pressure (BP), as well as AS of large-, medium-, and small-sized arteries via carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and radial-digital PWV (rdPWV), respectively. Our results showed that BP was increased in 1KDN and 0KDN, and that systolic BP values were restored in the TX configuration. Furthermore, a rise was reported in all PWVs for all tested configurations. The relative difference in stiffness from 2KDN to 0KDN was higher in the case of crPWV (15%) in comparison with the increase observed for cfPWV (11%). In TX, we observed a restoration of the PWVs to values close to 1KDN. Globally, it was demonstrated that alterations of the outflow boundaries to the renal arteries with staged kidney removal led to changes in BP and central and peripheral PWV in line with previously reported clinical data. Our findings suggest that the PWV variations observed in clinical practice with different stages of kidney disease may be partially attributed to biomechanical alterations of the arterial tree and their effect on BP.

Pulse wave velocity (PWV) is used to evaluate regional stiffness of large and medium-sized arteries. Here, we examine the feasibility and reliability of radial-digital PWV (RD-PWV) as a measure of regional stiffness of small conduit arteries and its response to changes in hydrostatic pressure. In 29 healthy subjects, we used Complior Analyse piezoelectric probes to record arterial pulse wave at the radial artery and the tip of the index. We determined transit time by second-derivative and intersecting tangents using the device-embedded algorithms and in-house MATLAB-based analyses of only reliable waves and by numerical simulation using a one-dimensional (1-D) arterial tree model coupled with a heart model. Second-derivative RD-PWV was 4.68 ± 1.18, 4.69 ± 1.21, and 4.32 ± 1.19 m/s for device-embedded, MATLAB-based, and numerical simulation analyses, respectively. Intersecting-tangent RD-PWV was 4.73 ± 1.20, 4.45 ± 1.08, and 4.50 ± 0.84 m/s for device-embedded, MATLAB-based, and numerical simulation analyses, respectively. Intersession coefficients of variation were 7.0% ± 4.9% and 3.2% ± 1.9% (

IntroductionPatients with end-stage renal disease are at higher risk of cardiovascular morbidity and mortality, a risk mediated in part by increased aortic stiffness. Arterial stiffness is assessed at different anatomical locations (central elastic or peripheral muscular arteries) using a variety of mechanical biomarkers. However, little is known on the robustness of each of these mechanical biomarkers following a haemodynamic stress caused by a single haemodialysis (HD) session.Methods and analysisA systematic review has been designed and reported in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols. A targeted search strategy applicable in key databases (PubMed, Embase, the Cochrane Library, Web of Science and grey literature) is constructed to search articles and reviews from inception to 16 October 2020. Only articles of studies conducted with adults under chronic HD for kidney failure, with repeated measures of arterial stiffness metrics (pulse wave velocity, Augmentation Index, arterial distensibility or stiffness) following a before-and-after design surrounding a HD session will be selected. The screening process, data extraction and assessment of risk bias will be done by two independent pairs of reviewers. Meta-analysis will enable adjustments for potential confounders and subgroup analyses will be performed to discriminate changes in arterial stiffness metrics from elastic, muscular or global arterial territories.Ethics and disseminationThis study does not require ethical approval. Findings will be submitted for publication to relevant peer-reviewed journals and will be presented at profession-specific conferences.PROSPERO registration numberCRD42020213946.

Pulse waveform analyses have become established components of cardiovascular research. Recently several methods have been proposed as tools to measure aortic pulse wave velocity (aPWV). The carotid-femoral pulse wave velocity (cf-PWV), the current clinical gold standard method for the noninvasive assessment of aPWV, uses the carotid-to-femoral pulse transit time difference (cf-PTT) and an estimated path length to derive cf-PWV. Objective: The heart-ankle PWV (ha-PWV), brachial-ankle PWV (ba-PWV) and finger-toe (ft-PWV) are also methods presuming to approximate aPWV based on time delays between physiological cardiovascular signals at two locations (similar to heart-ankle PTT, ha-PTT; similar to brachial-ankle PTT, ba-PTT; similar to finger-toe PTT, ft-PTT) and a path length typically derived from the subject's height. To test the validity of these methods, we used a detailed 1D arterial network model (143 arterial segments) including the foot and hand circulation. Approach: The arterial tree dimensions and properties were taken from the literature and completed with data from patient scans. We calculated PTTs with all the methods mentioned above. The calculated PTTs were compared with the aortic PTT (aPTT), which is considered as the absolute reference method in this study. Main results: The correlation between methods and aPTT was good and significant, cf-PTT (R-2 = 0.97; P < 0.001; mean difference 5 +/- 2 ms), ha-PTT (R-2 = 0.96; P < 0.001; 150 +/- 23 ms), ba-PTT (R-2 = 0.96; P < 0.001; 70 +/- 13 ms) and ft-PTT (R-2 = 0.95; P < 0.001; 14 +/- 10 ms). Consequently, good correlation was also observed for the PWV values derived with the tested methods, but absolute values differed because of the different path lengths used. Significance: In conclusion, our computer model-based analyses demonstrate that for PWV methods based on peripheral signals, pulse transit time differences closely correlate with the aortic transit time, supporting the use of these methods in clinical practice.

BACKGROUND Carotid-femoral pulse wave velocity (PWV) (cf-PWV) is the gold standard for measuring aortic stiffness. Finger-toe PWV (ft-PWV) is a simpler noninvasive method for measuring arterial stiffness. Although the validity of the method has been previously assessed, its accuracy can be improved. ft-PWV is determined on the basis of a patented height chart for the distance and the pulse transit time (PTT) between the finger and the toe pulpar arteries signals (ft-PTT). METHOD The objective of the first study, performed in 66 patients, was to compare different algorithms (intersecting tangents, maximum of the second derivative, 10% threshold and cross-correlation) for determining the foot of the arterial pulse wave, thus the ft-PTT. The objective of the second study, performed in 101 patients, was to investigate different signal processing chains to improve the concordance of ft-PWV with the gold-standard cf-PWV. Finger-toe PWV (ft-PWV) was calculated using the four algorithms. RESULTS The best correlations relating ft-PWV and cf-PWV, and relating ft-PTT and carotid-femoral PTT were obtained with the maximum of the second derivative algorithm [PWV: r = 0.56, P

Purpose/Background/Objective: Cognitive decline is highly prevalent amongst end-stage renal disease (ESRD) patients and is accelerated upon initiation of hemodialysis (HD) [1]. ESRD increases aortic stiffness and blood flow pulsatility, which may damage small vessels of target organs like the brain [2]. In this pilot study, we aimed to evaluate the acute effect of HD on cerebral blood flow and its relation to arterial stiffness. Methods: Before, every hour during and after HD (T0–T4), we measured cerebral flow velocity (FV) using transcranial Doppler, blood pressure (BP) via digital finger cuff (Nexfin), cardiac activity using ECG and aortic pulse wave velocity (PWV) with Mobile-O-Graph. FV pulsatility index (PI) and transit times between ECG peak and the foot of both FV and BP waveforms (cerebral dT; digital dT) were computed using in house MATLAB-based analysis. Changes during HD were evaluated with Generalized Estimating Equation models adjusting for multiple comparisons in SPSS 26.0. Results: In eight participants aged 63 ± 17 y. old (4 diabetics, 3 women), peak FV decreased from baseline at T1 and T2 (−11.2 cm/s, p = 0.007; −12.2 cm/s, p < 0.001), PI decreased at T1 (0.81 to 0.77, p = 0.005), whilst minimum FV, mean BP and partial pressure of CO2 remained unchanged. Digital dT increased at T3 (0.19 to 0.22, p < 0.001) and cerebral dT increased throughout HD (T1–T4, p < 0.005), whereas aortic PWV did not change. Conclusions: During hemodialysis, cerebral and digital transit times increased, suggesting decreased stiffness of small peripheral vessels, without significant changes in aortic stiffness. Reduced stiffness of cerebral arteries may partially explain decreased cerebral flow pulsatility.

Background: Identification of intraplaque haemorrhage using magnetic resonance imaging (MRI) is expensive, technically demanding and sometimes uncomfortable. Photoacoustic imaging (PAI) is a new non-invasive technique combining multi-wavelength infrared laser light and ultrasound (US) imaging, able to discriminate blood and other components in the tissues. The measurement by the multi-spectral PAI is likely to be more applicable and therefore could be complementary to MRI. Objectives: Validate a portable multimodal and multi-wavelength PAI system, for the identification of intraplaque haemorrhage and compare with MRI. Materials and Methods: Patients underwent carotid MRI, and US. Photoacoustic acquisitions are performed and analysed a posteriori blindly of the status of the subjects and results of MRI/US. All patients gave written informed consent. Histology of plaque will be performed as gold standard. Results: We included 15 patients (71 ± 5 years old) with carotid stenosis grade of >70% (NASCET). PAI imaging was feasible in all patients. On raw images, only clutter signal can be observed. After adequate post processing, carotid wall with the intima media and plaques were clearly visible with PAI. PAI signal from the lumen can be observed, also strong PAI signals are visible inside the plaque in a reproducible manner. Correspondence between MRI and PAI will be analysed later. Conclusion: The use of the PAI technique for carotid plaque assessment is feasible, and PAI signal are observed inside the plaque. Further analyses are needed to assess the reflected PAI signal inside the plaque, for haemorrhage detection in the future.

Arterial Stiffness (AS) is of great interest in the prediction and the management of cardiovascular events. The evaluation of AS using 2 points of measurement of the pulse wave velocity was of considerable increasing interest in the early 21st century. This paper aimed at focusing on the modeling of different measurement methods. Several measurement techniques are presented. A review of the bibliography and an explanation of the link between cardiovascular events and arterial stiffness are summarized. Novel apparatus that were developed for determining arterial stiffness claimed superiority over pioneering methods either through greater simplicity of use, better repeatability, or a more pertinent arterial pathway.

Analysis of the contour of the peripheral pulse to assess arterial properties was first described in the nineteenth century. The reference technique to estimate central blood pressure (CBP), non-invasively, is by analyzing the radial pressure pulse acquired using a tonometer and then to establish a transfer function relating the radial pressure to the CBP. An alternative technique utilizes a volume pulse. This may conveniently be acquired optically from a finger. This technique deserves further consideration because of its simplicity and ease of use. The objective is to establish a transfer function estimating the central blood pressure (CBP), calibrated with a brachial pressure cuff and using the parameters obtained with the contour analysis of the photoplethysmographic pulse measured at the finger with the pOpmetre® system. We positioned the photodiode sensor on the finger, insuring that the sensor's lens is in contact with the finger. Brachial blood pressure measurements was performed with a standard cuff. The central blood pressure values measured with Sphygmocor used as the reference values. Multiple regression analysis was done to establish the transfer functions. Sixty-nine subjects were included: 24 healthy subjects and 45 patients with essential hypertension aged 33 ± 8 years and 59 ± 17 years respectively. The correlation between the estimated central systolic pressure (CSP) and the reference one, was good and significant (r2 = 0.91; P

Background Arterial pulse wave velocity and pulse waveform analysis have become an established component of cardiovascular research. As validation and assessment of devices is not always trivial in an in vivo setting, arterial network computer models may be useful for that purpose. It is, however, mandatory that the model includes sufficient detail, especially when analysing peripheral waveforms. Purpose To extend the existing 1D arterial network model (103 segments) of Reymond et al. to a more detailed model (143 segments) including the foot and hand circulation (radial and tibial arteries). The goal is to (i) extend the existing 1D arterial network model (103 segments) of Reymond et al. to a more detailed model (143 segments) including the foot and hand circulation (Radial and Tibial arteries); (ii) use the extending model as testing tool for pOpmetre® (finger–toe pulse wave velocity). Method The arterial tree dimensions and properties were taken from the literature and completed with data from patient scans. The model solves the one-dimensional form of the Navier-Stokes equations over each arterial segment. A non-linear viscoelastic constitutive law for the arterial wall was considered. Result Comparison of simulations with & without detailed hand and foot circulation demonstrate important differences in waveform morphology in the distal beds. The completed model predicts pressure and flow waves in the hand and foot arteries which are in good qualitative agreement with the published in-vivo measurements. The agreement is especially good for the shape and wave details of the flow wave, where all features are reproduced in a rather faithful manner. The correlation between ftPWV and aPWV was good and significant (R2 = 0.95). The Bland and Altman analysis, mean difference was 0.4 m/s, classifying the ftPWV as good agreement with reference method. Conclusion The extended model yields realistic pressure and flow waveforms in arteries of the hand and the foot.

Objective: Pulse Wave Velocity (PWV) can be measured between different sites. Here we used two different aspects to assess the PWV; the standard method Carotid-Femoral (CF) Sphygmocor (AtCorMedical – Australia) and the pOpmetre ® (Axelife SAS – France) which uses the Finger to Toe (FT) signals. The aim of this study was to evaluate the agreement between FT-PWV and CF-PWV and to test the robustness of pOpmetre ® build-in algorithm. Design and method: CF and FT PWV was measured in 150 subjects. MatLab was used to calculate FT-PWV from pOpmetre ® waveforms using four methods: maximum of second derivative (used by pOpmetre ®), intersecting tangents, 10% threshold and the cross correlation method. Results: Using built in algorithms, the comparisons of the PWVs and transit times showed a good agreement between the two methods. FT-PWV correlated with CF-PWV (r2=0.51; p