Measurement of the local aortic stiffness by a non-invasive bioelectrical impedance technique

Aortic stiffness measurement is well recognized as an independent predictor of cardiovascular mortality and morbidity. Recently, a simple method has been proposed for the evaluation of the local aortic stiffness (AoStiff) using a non-invasive bioelectrical impedance (BI) technique. This approach relies on a novel interpretation of the arterial stiffness where AoStiff is computed from the measurement of two new BI variables: (1) the local aortic flow resistance (AoRes) exerted by the drag forces onto the flow; (2) the local aortic wall distensibility (AoDist). Herein, we propose to detail and compare these three indices with the reference pulse wave velocity (PWV) measurement and the direct assessment of the aortic drag forces (DF) and distensibility (DS) obtained by the magnetic resonance imaging technique. Our results show a significant correlation between AoStiff and PWV (r = 0.79; P < 0.0001; 120 patients at rest; mean age 44 ± 16 years), and also between AoRes and DF (r = 0.95; P = 0.0011) and between AoDist and DS (r = 0.93; P = 0.0022) on eight patients at rest (mean age 52 ± 19 years). These first results suggest that local aortic stiffness can be explored reliably by the BI technique

Assessment of aortic stiffness in computed tomography : methodology of radiological examination from 2000 to 2020

Introduction: Vascular elasticity may be a predictive factor of various diseases. Although stiffening is thought to be a natural consequence of ageing, it can be accelerated by a number of pathological conditions such as hypertension, diabetes, or renal diseases. Aim of the study was to discuss the methodology used to assess aortic stiffness, with particular emphasis on radiological examination. Material and methods: The PubMed and Google Scholar databases were screened from inception to the year 2000 by 2 independent analysts initially working separately and then comparing their results. Results: Assessment of stiffness can be divided into methods not requiring computed tomography scan, such as tonometry of carotid femoral pulse wave velocity, bioelectrical impedance analysis, and cardio ankle vascular index, and methods requiring it, such as multidetector row computed tomography - ECG gated, in which indexes such as aortic distensibility, aortic stiffness, and aortic compliance can be obtained with simultaneous calcification evaluation based on the Agatston score. Discussion: Aortic stiffness was corelated with left ventricular afterload, prehypertension, coronary artery plaques, predic tion of coronary artery diseases, bone demineralization, chronic obstructive pulmonary diseases, and diabetes mellitus. Conclusions: Being a factor of various severe diseases, aortic stiffness may play an important role in the early detection of patients requiring additional medical care

Regional body composition as a determinant of arterial stiffness in the elderly. The Hoorn Study.

Regional body composition as a determinant of arterial stiffness in the elderly: The Hoorn Study. Snijder MB, Henry RM, Visser M, Dekker JM, Seidell JC, Ferreira I, Bouter LM, Yudkin JS, Westerhof N, Stehouwer CD. Institute for Research in Extramural Medicine, VU University Medical Center, Amsterdam, The Netherlands. [email protected] OBJECTIVE: To estimate the relation of precisely measured regional body composition with peripheral and central arterial stiffness in the elderly. METHODS: We investigated 648 participants (mean age 69.0 +/- 6.0 years) of the Hoorn Study, a population-based cohort study. Trunk fat, leg fat, trunk lean and leg lean mass were distinguished by dual-energy X-ray absorptiometry. We used ultrasound to measure the distensibility and compliance of the carotid, femoral and brachial arteries, and carotid Young's elastic modulus, as estimates of peripheral stiffness. As estimates of central stiffness we measured carotid-femoral transit time, aortic augmentation index and systemic arterial compliance. RESULTS: After adjustment for sex, age, height, mean arterial pressure, leg lean and leg fat mass, a larger trunk fat mass was consistently associated with higher peripheral arterial stiffness (standardized beta (beta) of mean Z-scores of all three large arteries -0.24, P < 0.001). In contrast, larger leg fat mass (beta = 0.15, P = 0.009) and leg lean mass (beta = 0.09, P = 0.20) were associated with lower peripheral arterial stiffness. Trunk or leg fat mass were not associated with central arterial stiffness. Leg lean mass, however, was consistently associated with lower central arterial stiffness (beta = 0.29, P < 0.001). CONCLUSIONS: Trunk fat mass may have adverse effects on peripheral, but not on central arterial stiffness, while leg fat was not harmful and may have a slight protective effect. Larger leg lean mass was the most important determinant of lower central arterial stiffness. These results provide a pathophysiological framework to explain not only the higher cardiovascular risk in individuals with larger trunk fat mass, but also the reduced cardiovascular risk in individuals with larger leg lean and fat mas

The Influence of Ultra-Endurance Exercise on the Cardiovascular and Related Physiological Systems

INTRODUCTION: There is currently limited longitudinal data investigating the performance and health-related influence of ultra-endurance training and participation. Cross-sectional investigations have highlighted a potential for those performing most exercise to be at an increased risk of cardiovascular events. If such risks occur, they are likely to be due to a combination of the stress provided through training and events together. PURPOSE: To assess the development of several physiological factors associated with exercise training and to gain a greater insight regarding the changes in cardiac electrical conductance from endurance training. A sub-study sought to investigate the short and longer-term influence of an iron-distance triathlon on indirect measures of arterial stiffness. METHOD: Part 1: Seventy-six previously recreationally active participants underwent a 6 month endurance training programme in preparation for an iron-distance triathlon, consisting of a 3.86km swim, 180.25km cycle, and a 42.2km run. Multiple assessments were performed at months 0, 2, 4 and 6; including submaximal and exhaustive cycling tests, anthropometric measurements and 12-lead ECG’s. Part 2: Eleven athletes from part 1 (TRI) and 10 recreational control participants (NOTRI) were assessed on 4 occasions with identical time intervals. Arterial stiffness and cardiovascular functional parameters were obtained 7 days prior (T1) to an iron-distance triathlon, 12–18 hours post-event, 7 days post-event, and 28 days post-event. RESULTS: Part 1: Cardiorespiratory fitness and performance parameters increased over the training period, irrespective of age, with greatest improvements from month 0–2 and the least improvements from month 4–6. Additionally, a progressive increase was observed in the frequency of both training-related and training-unrelated ECG findings. Part 2: A significant difference in central arterial stiffness was found between TRI and NOTRI 12–18 hours post-event and 7 days post-event but not prior to or 28 days post-event. No differences were observed between groups for peripheral stiffness at any time-point. Additionally, no time effect was observed when the TRI group were treated separately. CONCLUSION: Training caused significant improvements to fitness related physiological factors. In a minority of individuals, endurance training induced bioelectrical patterns of what is currently referred to as abnormal criteria, which may reflect a normal change to what was previously thought of as abnormal findings or, alternatively, be pathological manifestations in previously healthy individuals. Part 2 of this study showed a delayed central arterial stiffening may occur one day and one week following a single day ultra-endurance event. Importantly, all measurements were found to be similar one month post-event; implying only a transient exercise-induced elevation to arterial stiffness

Assessment of trends in the cardiovascular system from time interval measurements using physiological signals obtained at the limbs

Cardiovascular diseases are an increasing source of concern in modern societies due to their increasing prevalence and high impact on the lives of many people. Monitoring cardiovascular parameters in ambulatory scenarios is an emerging approach that can provide better medical access to patients while decreasing the costs associated to the treatment of these diseases. This work analyzes systems and methods to measure time intervals between the electrocardiogram (ECG), impedance plethysmogram (IPG), and the ballistocardiogram (BCG), which can be obtained at the limbs in ambulatory scenarios using simple and cost-effective systems, to assess cardiovascular intervals of interest, such as the pulse arrival time (PAT), pulse transit time (PTT), or the pre-ejection period (PEP). The first section of this thesis analyzes the impact of the signal acquisition system on the uncertainty in timing measurements in order to establish the design specifications for systems intended for that purpose. The minimal requirements found are not very demanding yet some common signal acquisition systems do not fulfill all of them while other capabilities typically found in signal acquisition systems could be downgraded without worsening the timing uncertainty. This section is also devoted to the design of systems intended for timing measurements in ambulatory scenarios according to the specifications previously established. The systems presented have evolved from the current state-of-the-art and are designed for adequate performance in timing measurements with a minimal number of active components. The second section is focused on the measurement of time intervals from the IPG measured from limb to limb, which is a signal that until now has only been used to monitor heart rate. A model to estimate the contributions to the time events in the measured waveform of the different body segments along the current path from geometrical properties of the large arteries is proposed, and the simulation under blood pressure changes suggests that the signal is sensitive to changes in proximal sites of the current path rather than in distal sites. Experimental results show that the PAT to the hand-to-hand IPG, which is obtained from a novel four-electrode handheld system, is correlated to changes in the PEP whereas the PAT to the foot-to-foot IPG shows good performance in assessing changes in the femoral PAT. Therefore, limb-to-limb IPG measurements significantly increase the number of time intervals of interest that can be measured at the limbs since the signals deliver information from proximal sites complementary to that of other measurements typically performed at distal sites. The next section is devoted to the measurement of time intervals that involve different waves of the BCG obtained in a standing platform and whose origin is still under discussion. From the relative timing of other physiological signals, it is hypothesized that the IJ interval of the BCG is sensitive to variations in the PTT. Experimental results show that the BCG I wave is a better surrogate of the cardiac ejection time than the widely-used J wave, which is also supported by the good correlation found between the IJ interval and the aortic PTT. Finally, the novel time interval from the BCG I wave to the foot of the IPG measured between feet, which can be obtained from the same bathroom scale than the BCG, shows good performance in assessing the aortic PAT. The results presented reinforce the role of the BCG as a tool for ambulatory monitoring since the main time intervals targeted in this thesis can be obtained from the timing of its waves. Even though the methods described were tested in a small group of subjects, the results presented in this work show the feasibility and potential of several time interval measurements between the proposed signals that can be performed in ambulatory scenarios, provided the systems intended for that purpose fulfill some minimal design requirements.Les malalties cardiovasculars són una tema de preocupació creixent en societats modernes, degut a l’augment de la seva prevalença i l'elevat impacte en les vides dels pacients que les sofreixen. La mesura i monitoratge de paràmetres cardiovasculars en entorns ambulatoris és una pràctica emergent que facilita l’accés als serveis mèdics i permet reduir dràsticament els costos associats al tractament d'aquestes malalties. En aquest treball s’analitzen sistemes i mètodes per la mesura d’intervals temporals entre l’electrocardiograma (ECG), el pletismograma d’impedància (IPG) i el balistocardiograma (BCG), que es poden obtenir de les extremitats i en entorns ambulatoris a partir de sistemes de baix cost, per tal d’avaluar intervals cardiovasculars d’interès com el pulse arrival time (PAT), pulse transit time (PTT) o el pre-ejection period (PEP). En la primera secció d'aquesta tesi s’analitza l’impacte del sistema d’adquisició del senyal en la incertesa de mesures temporals, per tal d’establir els requeriments mínims que s’han de complir en entorns ambulatoris. Tot i que els valors obtinguts de l’anàlisi no són especialment exigents, alguns no són assolits en diversos sistemes habitualment utilitzats mentre que altres solen estar sobredimensionats i es podrien degradar sense augmentar la incertesa en mesures temporals. Aquesta secció també inclou el disseny i proposta de sistemes per la mesura d’intervals en entorns ambulatoris d’acord amb les especificacions anteriorment establertes, a partir de l’estat de l’art i amb l’objectiu de garantir un correcte funcionament en entorns ambulatoris amb un nombre mínim d’elements actius per reduir el cost i el consum. La segona secció es centra en la mesura d’intervals temporals a partir de l’IPG mesurat entre extremitats, que fins al moment només s’ha fet servir per mesurar el ritme cardíac. Es proposa un model per estimar la contribució de cada segment arterial per on circula el corrent a la forma d’ona obtinguda a partir de la geometria i propietats físiques de les artèries, i les simulacions suggereixen que la senyal entre extremitats és més sensible a canvis en arteries proximals que en distals. Els resultats experimentals mostren que el PAT al hand-to-hand IPG, obtingut a partir d’un innovador sistema handheld de quatre elèctrodes, està fortament correlacionat amb els canvis de PEP, mentre que el PAT al foot-to-foot IPG està correlat amb els canvis en PAT femoral. Conseqüentment, l’ILG entre extremitats augmenta de manera significativa els intervals d’interès que es poden obtenir en extremitats degut a que proporciona informació complementària a les mesures que habitualment s’hi realitzen. La tercera secció està dedicada a la mesura d’intervals que inclouen les ones del BCG vertical obtingut en plataformes, de les que encara se’n discuteix l’origen. A partir de la posició temporal relativa respecte altres ones fisiològiques, s’hipostatitza que l’interval IJ del BCG es sensible a variacions del PTT. Els resultats experimentals mostren que la ona I del BCG és un millor indicador de l’ejecció cardíaca que el pic J, tot i que aquest és el més utilitzat habitualment, degut a la bona correlació entre l’interval IJ i el PTT aòrtic. Finalment, es presenta un mètode alternatiu per la mesura del PTT aòrtic a partir de l’interval entre el pic I del BCG i el peu del foot-to-foot IPG, que es pot obtenir de la mateixa plataforma que el BCG i incrementa la robustesa de la mesura. Els resultats presentats reforcen el paper del BCG com a en mesures en entorns ambulatoris, ja que els principals intervals objectiu d’aquesta tesi es poden obtenir a partir de les seves ones. Tot i que els mètodes descrits han estat provats en grups petits de subjectes saludables, els resultats mostren la viabilitat i el potencial de diversos intervals temporals entre les senyals proposades que poden ésser realitzats en entorns ambulatoris, sempre que els sistemes emprats compleixin els requisits mínims de disseny.Postprint (published version

The Effect of Curcumin on Cardiovascular Health in Obese Men

Cardiovascular disease is the leading cause of death in the United States, and conventional treatment often emphasizes pharmaceutical approaches. Research has recently started exploring non-pharmaceutical approaches, including nutritional interventions. This research study was conducted to test the effectiveness of a novel nutritional approach, curcumin, on the improvement of cardiovascular health in young, obese males (BMI≥30 kg/m2). This study included 22 men, matched based on BMI and randomly assigned to the intervention (n=11) or placebo group (n=11). The intervention consisted of 12 weeks of curcumin supplementation (1.0 g/day) with fenugreek added to enhance the curcumin bioavailability; the placebo consisted of 12 weeks of equal parts fenugreek to that found in the intervention. To determine cardiovascular improvements, arterial stiffness via gold-standard carotid-femoral pulse wave velocity (cfPWV), endothelial dysfunction via reactive hyperemia index (RHI), and inflammation via plasma cytokine concentrations were measured. There were no overall differences in cfPWV (p=0.428) or RHI (p=0.951) between groups following the 12 weeks of intervention. However, some individuals did respond to the curcumin treatment with reductions in cfPWV, while others did not. Subjects who did respond to the curcumin treatment (n=6) entered the study with higher baseline values of cfPWV than those that did not respond (n=5) (6.81 m/s v. 5.84 m/s, p = 0.045). This suggests a potential role for curcumin to improve arterial stiffness in individuals with stiffer arteries at baseline. A possible mechanism to explain the difference in responsiveness is a trending increase in IL-13 (p=0.052), an anti-inflammatory cytokine that has been associated with amelioration of collagen content in the arteries. Also, 12 weeks of curcumin intervention resulted in reductions in brachial pulse pressure (p\u3c0.05), a surrogate marker of arterial stiffness. This change in brachial pulse pressure in the curcumin group could be explained by an increased trend in anti-inflammatory cytokine IL-10 (p=0.071), but further studies are required to confirm this finding. Based on the findings of this study, curcumin might serve as a non-pharmaceutical intervention to improve vascular health in young obese men, especially when arteries are stiffer than age-matched counterparts