Reference values for local arterial stiffness. Part B: femoral artery

Structural and Mechanical Properties of Human Superficial Femoral and Popliteal Arteries

The femoropopliteal artery (FPA) is the main artery in the lower limb. It supplies blood to the leg muscles and undergoes complex deformations during limb flexion. Atherosclerotic disease of the FPA (peripheral arterial disease, PAD) is a major public health burden, and despite advances in surgical and interventional therapies, the clinical outcomes of PAD repairs continue to be suboptimal, particularly in challenging calcified lesions and biomechanically active locations. A better understanding of human FPA mechanical and structural characteristics in relation to age, risk factors, and the severity of vascular disease can help develop more effective and longer-lasting treatments through computational modeling and device optimization. This review aims to summarize recent research on the main biomechanical and structural properties of human superficial femoral and popliteal arteries that comprise the FPA and describe their anatomy, composition, and mechanical behavior under different conditions.

The Ultrasound Window Into Vascular Ageing: A Technology Review by the VascAgeNet COST Action

Non-invasive ultrasound (US) imaging enables the assessment of the properties of superficial blood vessels. Various modes can be used for vascular characteristics analysis, ranging from radiofrequency (RF) data, Doppler- and standard B/M-mode imaging, to more recent ultra-high frequency and ultrafast techniques. The aim of the present work was to provide an overview of the current state-of-the-art non-invasive US technologies and corresponding vascular ageing characteristics from a technological perspective. Following an introduction about the basic concepts of the US technique, the characteristics considered in this review are clustered into: 1) vessel wall structure; 2) dynamic elastic properties, and 3) reactive vessel properties. The overview shows that ultrasound is a versatile, non-invasive, and safe imaging technique that can be adopted for obtaining information about function, structure, and reactivity in superficial arteries. The most suitable setting for a specific application must be selected according to spatial and temporal resolution requirements. The usefulness of standardization in the validation process and performance metric adoption emerges. Computer-based techniques should always be preferred to manual measures, as long as the algorithms and learning procedures are transparent and well described, and the performance leads to better results. Identification of a minimal clinically important difference is a crucial point for drawing conclusions regarding robustness of the techniques and for the translation into practice of any biomarker.

Reproduction of human blood pressure waveform using physiology-based cardiovascular simulator

This study presents a cardiovascular simulator that mimics the human cardiovascular system's physiological structure and properties to reproduce the human blood pressure waveform. Systolic, diastolic blood pressures, and its waveform are key indicators of cardiovascular health. The blood pressure waveform is closely related to the pulse wave velocity and the overlap of the forward and reflected pressure waves. The presented cardiovascular simulator includes an artificial aorta made of biomimetic silicone. The artificial aorta has the same shape and stiffness as the human standard and is encased with a compliance chamber. The compliance chamber prevents distortion of the blood pressure waveform from strain-softening by applying extravascular pressure. The blood pressure waveform reproduced by the simulator has a pressure range of 80-120 mmHg, a pulse wave velocity of 6.58 m/s, and an augmentation index of 13.3%. These values are in the middle of the human standard range, and the reproduced blood pressure waveform is similar to that of humans. The errors from the human standard values are less than 1 mmHg for blood pressure, 0.05 m/s for pulse wave velocity, and 3% for augmentation index. The changes in blood pressure waveform according to cardiovascular parameters, including heart rate, stroke volume, and peripheral resistance, were evaluated. The same pressure ranges and trends as in humans were observed for systolic and diastolic blood pressures according to cardiovascular parameters.

Aging of the Arterial System

Aging of the vascular system is associated with deep changes of the structural proprieties of the arterial wall. Arterial hypertension, diabetes mellitus, and chronic kidney disease are the major determinants for the loss of elasticity and reduced compliance of vascular wall. Arterial stiffness is a key parameter for assessing the elasticity of the arterial wall and can be easily evaluated with non-invasive methods, such as pulse wave velocity. Early assessment of vessel stiffness is critical because its alteration can precede clinical manifestation of cardiovascular disease. Although there is no specific pharmacological target for arterial stiffness, the treatment of its risk factors helps to improve the elasticity of the arterial wall.

Sex differences in pressure and flow waveform physiology across the life course

Cardiovascular disease (CVD) has long been deemed a disease of old men. However, in 2019 CVD accounted for 35% of all deaths in women and, therefore, remains the leading cause of death in both men and women. There is increasing evidence to show that risk factors, pathophysiology and health outcomes related to CVD differ in women compared with men, yet CVD in women remains understudied, underdiagnosed and undertreated. Differences exist between the sexes in relation to the structure of the heart and vasculature, which translate into differences in blood pressure and flow waveform physiology. These physiological differences between women and men may represent an important explanatory factor contributing to the sex disparity in CVD presentation and outcomes but remain understudied. In this review we aim to describe sex differences in arterial pressure and flow waveform physiology and explore how they may contribute to differences in CVD in women compared to men. Given that unfavourable alterations in the cardiovascular structure and function can start as early as in utero, we report sex differences in waveform physiology across the entire life course.

Optimised design of an arterial network model reproduces characteristic central and peripheral hemodynamic waveform features in young adults

Abstract

The arterial network in healthy young adults is thought to be structured to optimize wave reflection in the arterial system, producing an ascending aortic pressure waveform with three key features: early systolic peak, negative systolic augmentation and diastolic hump. One‐dimensional computer models have provided significant insights into arterial haemodynamics, but no previous models of the young adult have exhibited these three features. Given that this issue was likely to be related to unrepresentative or non‐optimized impedance properties of the model arterial networks, we developed a new ‘YoungAdult’ model that incorporated the following features: (i) a new and more accurate empirical equation for approximating wave speeds, based on area and relative distance to elastic–muscular arterial transition points; (ii) optimally matched arterial junctions; and (iii) an improved arterial network geometry that eliminated ‘within‐segment’ taper (which causes wave reflection in conduit arteries) whilst establishing ‘impedance‐preserving’ taper. These properties of the model led to wave reflection occurring predominantly at distal vascular beds, rather than in conduit arteries. The model predicted all three typical characteristics of an ascending aortic pressure waveform observed in young adults. When compared with non‐invasively acquired pressure and velocity measurements (obtained via tonometry and Doppler ultrasound in seven young adults), the model was also shown to reproduce the typical waveform morphology observed in the radial, brachial, carotid, temporal, femoral and tibial arteries. The YoungAdult model provides support for the concept that the arterial tree impedance in healthy young adults is exquisitely optimized, and it provides an important baseline model for investigating cardiovascular changes in ageing and disease states.

Key points

The origin of wave reflection in the arterial system is controversial, but reflection properties are likely to give rise to characteristic haemodynamic features in healthy young adults, including an early systolic peak, negative systolic augmentation and diastolic hump in the ascending aortic pressure waveform, and triphasic velocity profiles in peripheral arteries. Although computational modelling provides insights into arterial haemodynamics, no previous models have predicted all these features.

An established arterial network model was optimized by incorporating the following features: (i) a more accurate representation of arterial wave speeds; (ii) precisely matched junctions; and (iii) impedance‐preserving tapering, thereby minimizing wave reflection in conduit arteries in the forward direction. Comparison with in vivo data (n = 7 subjects) indicated that the characteristic waveform features in young adults were predicted accurately.

Our findings strongly imply that a healthy young arterial system is structured to optimize wave reflection in the main conduit arteries and that reflection of forward waves occurs primarily in the vicinity of vascular beds.

Estimation of Aortic Stiffness with Bramwell–Hill Equation: A Comparative Analysis with Carotid–Femoral Pulse Wave Velocity

Aortic stiffness is an important clinical parameter for predicting cardiovascular events. Carotid–femoral pulse wave velocity (cf-PWV) has been proposed for performing this evaluation non-invasively; however, it requires dedicated equipment and experienced operators. We explored the possibility of measuring aortic stiffness using ultrasound scans of the abdominal aorta coupled with the Bramwell–Hill equation. Healthy subjects were investigated; measurements of cf-PWV were taken by arterial tonometry and aortic systo-diastolic pressure difference was estimated using a validated model. Pulsatility of an abdominal tract of aorta was assessed by automated processing of ultrasound scans. Through a Bland–Altmann analysis, we found large biases when estimating each parameter by applying the Bramwell–Hill equation to the measured values of the other two paramters (bias, ± 1.96 SD; PWV, about 2.1 ± 2.5 m/s; pulsatility, 12 ± 14%; pressure jump, 47 ± 55 mmHg). These results indicate that the two measures are not interchangeable, and that a large part of the bias is attributable to blood pressure estimation. Further studies are needed to identify the possible sources of bias between cf-PWV and aortic pulsatility.

Aging-Related Moderation of the Link Between Compliance With International Physical Activity Recommendations and the Hemodynamic, Structural, and Functional Arterial Status of 3,619 Subjects Aged 3-90 Years

Background

Compliance with physical activity recommendations (CPARs) is associated with better health indicators. However, there are only few studies to date that have comprehensively analyzed the association between CPARs and cardiovascular status "as a whole" (e.g., analyzing hemodynamic, structural, and functional properties, and different arterial territories). The relationship between CPARs and cardiovascular properties could be strongly influenced by the growth and aging process.

Aim

The goal of the study is to investigate the association between CPAR and cardiovascular properties by placing special emphasis on: (i) identifying if there is an independent association, (ii) if the association is "moderated" by age, and (iii) to what extent the association depends on the arterial parameter (hemodynamic vs. structural vs. functional) and/or the arterial segment (e.g., central vs. peripheral; elastic vs. transitional vs. muscular arteries).

Methods

A total of 3,619 subjects (3-90 years of age) were studied. Extensive cardiovascular evaluations were performed. Cardiovascular risk factors (CRFs) and physical activity (PA) levels were determined. The subjects were categorized as compliant (n = 1, 969) or non-compliant (n = 1,650) with World Health Organization-related PA recommendations. Correlation and multiple regression models (including CPAR*Age interaction) were obtained, and Johnson-Neyman technique was used to produce regions of significance.

Results

The independent association between CPARs and cardiovascular characteristics were strongly moderated by age. The moderation was observed on a wide range of age but particularly notorious on the extremes of life. Certain arterial characteristics demonstrated opposite effects in relation to CPAR status depending on the range of age considered. The association between CPAR and cardiovascular characteristics was independent of CRFs and moderated by age. In subjects younger than 45-55 years, CPAR status was associated with lower central and peripheral blood pressure (i.e., the younger the subject, the higher the reduction). During adult life, as age increases in the subjects, CPARs was associated with a beneficial hemodynamic profile, which is not related with variations in pressure but strongly related with lower levels of waveform-derived indexes and ventricular afterload determinants.

Conclusions

The independent associations between CPARs and arterial properties were strongly moderated by age. Data provided by blood pressure levels and waveform-derived indexes would be enough to evaluate the independent association between CPARs and the vascular system in the general population.

Central Pressure Waveform-Derived Indexes Obtained From Carotid and Radial Tonometry and Brachial Oscillometry in Healthy Subjects (2–84 Y): Age-, Height-, and Sex-Related Profiles and Analysis of Indexes Agreement

Aortic blood pressure (aoBP) waveform-derived indexes could provide valuable (prognostic) information over and above cardiovascular risk factors (CRFs). To obtain aoBP waveform-characteristics, several (i) techniques, (ii) recording sites, (iii) pressure-only waveform analysis mathematical approaches [e.g., pulse wave analysis (PWA), wave separation analysis (WSA)], and (iv) indexes [augmentation pressure and index (AP and AIx), forward (Pf) and backward (Pb) components of aoBP, reflection magnitude (RM), and reflection index (Rix)], were proposed. An accurate clinical use of these indexes requires knowing their physiological age-related profiles and the expected values for a specific subject. There are no works that have characterized waveform-derived indexes profiles in large populations considering: (i) as a continuous, data from different age stages (childhood, adolescence, and adulthood), (ii) complementary indexes, (iii) data obtained from different techniques and approaches, and (iv) analyzing potential sex- and body height (BH)-related differences. In addition, (v) there is a lack of normative data (reference intervals, RIs) for waveform-derived indexes.

Sex- and Age-Related Physiological Profiles for Brachial, Vertebral, Carotid, and Femoral Arteries Blood Flow Velocity Parameters During Growth and Aging (4-76 Years): Comparison With Clinical Cut-Off Levels

Ultrasound-derived blood flow velocity (BFV) levels [e.g., peak systolic velocity (PSV)], intrabeat indexes (e.g., resistive), and intersegment ratios [e.g., internal/common carotid artery (ICA/CCA) PSV ratio] are assessed to describe cardiovascular physiology and health status (e.g., disease severity evaluation and/or risk stratification). In this respect, fixed cut-off values (disregard of age or sex) have been proposed to define “significant” vascular disease from BFV-derived data (parameters). However, the use of single fixed cut-off values has limitations. Accurate use of BFV-derived parameters requires knowing their physiological age-related profiles and the expected values for a specific subject. To our knowledge, there are no studies that have characterized BFV profiles in large populations taking into account: (i) data from different age-stages (as a continuous) and transitions (childhood–adolescence–adulthood), (ii) complementary parameters, (iii) data from different arteries, and (iv) potential sex- and hemibody-related differences. Furthermore, (v) there is little information regarding normative data [reference intervals (RIs)] for BFV indexes.

Aims: The aims of this study are the following: (a) to determine the need for age-, body side-, and sex-specific profiles for BFV levels and derived parameters (intrabeat indexes and intersegment ratios), and (b) to define RIs for BFV levels and parameters, obtained from CCA, ICA, external carotid, vertebral, femoral, and brachial arteries records.

Methods: A total of 3,619 subjects (3–90 years) were included; 1,152 were healthy (without cardiovascular disease and atheroma plaques) and non-exposed to cardiovascular risk factors. BFV data were acquired. The agreement between left and right data was analyzed (Concordance correlation, Bland–Altman). Mean and SD equations and age-related profiles were obtained for BFV levels and parameters (regression methods; fractional polynomials).

Results: Left and right body-side derived data were not always equivalent. The need for sex-specific RIs was dependent on the parameter and/or age considered. RIs were defined for each studied artery and parameter. Percentile curves were compared with recommended fixed cut-off points. The equations for sex, body-side, and age-specific BFV physiological profiles obtained in the large population (of children, adolescents, and adults) studied were included (spreadsheet formats), enabling to determine for a particular subject, the expected values and potential data deviations.

Plasma expression of microRNA-425-5p and microRNA-451a as biomarkers of cardiovascular disease in rheumatoid arthritis patients

To validate in a cohort of 214 rheumatoid arthritis patients a panel of 10 plasmatic microRNAs, which we previously identified and that can facilitate earlier diagnosis of cardiovascular disease in rheumatoid arthritis patients. We identified 10 plasma miRs that were downregulated in male rheumatoid arthritis patients and in patients with acute myocardial infarction compared to controls suggesting that these microRNAs could be epigenetic biomarkers for cardiovascular disease in rheumatoid arthritis patients. Six of those microRNAs were validated in independent plasma samples from 214 rheumatoid arthritis patients and levels of expression were associated with surrogate markers of cardiovascular disease (carotid intima-media thickness, plaque formation, pulse wave velocity and distensibility) and with prior cardiovascular disease. Multivariate analyses adjusted for traditional confounders and treatments showed that decreased expression of microRNA-425-5p in men and decreased expression of microRNA-451 in women were significantly associated with increased (β = 0.072; p = 0.017) and decreased carotid intima-media thickness (β = -0.05; p = 0.013), respectively. MicroRNA-425-5p and microRNA-451 also increased the accuracy to discriminate patients with pathological carotid intima-media thickness by 1.8% (p = 0.036) in men and 3.5% (p = 0.027) in women, respectively. In addition, microRNA-425-5p increased the accuracy to discriminate male patients with prior cardiovascular disease by 3% (p = 0.008). Additionally, decreased expression of microRNA-451 was significantly associated with decreased pulse wave velocity (β = -0.72; p = 0.035) in overall rheumatoid arthritis population. Distensibility showed no significant association with expression levels of the microRNAs studied. We provide evidence of a possible role of microRNA-425-5p and microRNA-451 as useful epigenetic biomarkers to assess cardiovascular disease risk in patients with rheumatoid arthritis.

Age- and sex-related profiles for macro, macro/micro and microvascular reactivity indexes: Association between indexes and normative data from 2609 healthy subjects (3-85 years)

Vascular reactivity (VR), defined as blood vessels’ capability to actively modify the diameter and flow resistances can be non-invasively assessed analyzing vascular response to forearm occlusion. Several VR indexes can be quantified: (i) ´microvascular´, which consider variables that depend almost exclusively on changes in distal resistances, (ii)´ macrovascular´, that evaluate the changes in brachial artery (BA) diameter, adjusting for blood flow stimulus, and (iii) ´macro/micro´, whose values depend on the micro and macrovascular response without discriminating each one´s contribution. VR indexes could not be associated. Many VR indexes have been used without availability of adequate normative data (reference intervals, RIs). Aims: (1) to evaluate macro, macro/micro and micro VR indexes obtained in a cohort of healthy children, adolescents and adults, (2) to evaluate the association between VR indexes, (3) to determine the need for age and/or sex-specific RIs, and (4) to define RIs for VR indexes. Methods: Ultrasound (B-mode/Doppler) and automatic computerized analysis were used to assess BA diameter, blood flow velocity and distal resistances, at rest and in conditions of decreased and increased blood flow. Macro, macro/micro and micro VR indexes were quantified (n = 3619). RIs-subgroups were defined according to European Reference Values for Arterial Measurements Collaboration Group (n = 1688, 3–84 years) and HUNT3-Fitness Study Group (n = 2609, 3–85 years) criteria. Mean value and standard deviation equations were obtained for VR indexes. The need for age or sex-specific RIs was analyzed. Percentile curves were defined and data were compared with those obtained in other populations. Conclusion: Macro and macro/micro VR indexes showed no association (or it was very weak) with microvascular indexes. Age- and sex-related profiles and RIs for macro, macro/micro and micro VR indexes were defined in a large population of healthy subjects (3–85 y). Equations for mean, standard deviation and percentiles values (year-to-year) were included in text and spreadsheet formats.

First experiences of local pulse wave velocity measurements in 4D-MRI in focally stented femoropopliteal arteries

Background: In peripheral arterial disease (PAD) the femoropopliteal (FP) artery is the most frequently recanalized lower limb artery. Stent-based interventions change the biomechanical properties of FP arteries. However, no clinical tool for functional imaging is established for quantitative measurements in vivo. Four-dimensional-flow magnetic resonance imaging enables a detailed evaluation of the hemodynamics of the central and - more challenging - the peripheral arteries. The present study aimed to determine the feasibility of assessing pulse wave velocities (PWV) as a marker of vessel stiffness in PAD patients with multiple spot stents and to compare the values with age-matched subjects and young-adult healthy subjects. Patients and methods: Contrast-free 4D-flow MRI was performed in seven PAD patients with focally stented FP arteries, five age-matched subjects after exclusion of PAD, and five young, healthy adults. PWV values were calculated from flow curves by using the foot-to-foot method. Results: Four-D-flow MRI sequences offering high spatial and temporal resolution enables quantification of flow velocity measurements and estimation of PWVs. Assessment of segmental PWV as a surrogate of vascular stiffness in focally stented femoral arteries is feasible. PWV values across all groups were 15.6±5.2 m/s, 13.3±4.1 m/s, and 9.9±2.2 m/s in PAD patients, senior-aged volunteers, and young-adult volunteers respectively. PWV values in PAD patients were similar with those in the senior-aged volunteers group (15.6±5.2 vs. 13.3 ±4.1 years, p=0.43). However, when compared to the young-adult volunteers, PAD patients had a statistically significantly higher mean local PWV (15.6±5.2 m/s vs. 9.9±2.2 m/s, p<0.05). Conclusions: Calculating segmental PWV in the femoral arteries is feasible in PAD patients with focally stented FP arteries. PWV values in PAD patients were similar to those in senior-aged volunteers, both of which were higher than in young-adult volunteers.

Youth Vascular Consortium (YVC) Protocol: Establishing Reference Intervals for Vascular Ageing in Children, Adolescents and Young Adults

BACKGROUND

In the last two decades, the global prevalence of paediatric hypertension increased by approximately 75%. Nearly 25% of children are now classified as obese or overweight. Substantial evidence suggests that risk factors for cardiovascular disease (CVD) begin to develop in childhood, thus warranting the need for tools to better screen for early CVD risk in youth. Vascular ageing, the deterioration of vascular structure and function, may be a potentially useful tool for detecting the early and asymptomatic signs of CVD burden. However, it is currently unclear what differentiates normal from pathological ageing in youth as existing reference values for vascular ageing in youth are limited by small sample size or homogenous populations. The international Youth Vascular Consortium (YVC) has been established to address these issues.

AIMS

The primary aim of the YVC is to develop reference intervals of normal vascular ageing in children, adolescents, and young adults. The secondary, exploratory, aim is to perform head-to-head comparisons of vascular ageing biomarkers to determine which biomarker is most strongly related to cardiometabolic health.

STUDY DESIGN

The YVC is a retrospective, multicentre study and will collate data on vascular ageing in children (5-12 years), adolescents (13-18 years) and young adults (19-40 years), as well as routine clinical biochemistry, lifestyle, sociodemographic factors and parental health.

CONCLUSION

To date, 31 research groups from 19 countries have joined the YVC. To our knowledge, this will be the largest study of its kind to investigate vascular ageing in youth.

Reference Intervals for Brachial Artery Flow-Mediated Dilation and the Relation With Cardiovascular Risk Factors

[Figure: see text].

The effect of coronary angiography and femoral access on femoral artery distensibility and elasticity

AIM OF THE STUDY

The aim of this study was to evaluate the long-term effects of access to the femoral artery for the purposes of coronary angiography through the measurement of femoral artery distensibility and elasticity on the accessed and non-accessed sides.

MATERIAL AND METHODS

This cross-sectional study included patients who underwent femoral angiography at least 1 year previously. Those whose femoral artery was accessed once formed Group 1 (n = 59), those who were accessed twice formed Group 2 (n = 57), those accessed 3 times formed Group 3 (n = 55), and those with more than 3 accesses, Group 4 (n = 60). The groups were compared in respect of femoral artery elasticity and distensibility in the accessed and non-accessed sides.

RESULTS

No statistically significant difference was determined in respect of femoral distensibility and elasticity in Group 1 (9.40 ± 0.84 vs 9.48 ± 0.75, p = 0.107 and 0.23 ± 0.03 vs 0.23 ± 0.03, p = 0.433, respectively). However, a significant difference was observed between the two sides in terms of distensibility and elasticity in Group 2 (9.02 ± 0.81 vs 9.23 ± 0.75, and 0.21 ± 0.02 vs 0.22 ± 0.02), in Group 3 (8.49 ± 0.77 vs 9.18 ± 0.9 and 0.19 ± 0.02 vs 0.21 ± 0.02), and in Group 4 (8.14 ± 0.74 vs 9.03 ± 0.81 and 0.16 ± 0.01 vs 0.2 ± 0.02, p <0.001, for all comparisons).

CONCLUSION

While a single access in the femoral artery for coronary angiography does not affect femoral artery elasticity and distensibility, multiple accesses may have adverse effects.

Physiological Age- and Sex-Related Profiles for Local (Aortic) and Regional (Carotid-Femoral, Carotid-Radial) Pulse Wave Velocity and Center-to-Periphery Stiffness Gradient, with and without Blood Pressure Adjustments: Reference Intervals and Agreement between Methods in Healthy Subjects (3-84 Years)

In addition to being a marker of cardiovascular (CV) aging, aortic stiffening has been shown to be independently associated with increased CV risk (directly and/or indirectly due to stiffness-gradient attenuation). Arterial stiffness determines the rate at which the pulse pressure wave propagates (i.e., pulse wave velocity, PWV). Thus, propagated PWV (i.e., the distance between pressure-wave recording sites divided by the pulse transit time) was proposed as an arterial stiffness index. Presently, aortic PWV is considered a gold-standard for non-invasive stiffness evaluation. The limitations ascribed to PWV have hampered its use in clinical practice. To overcome the limitations, different approaches and parameters have been proposed (e.g., local PWV obtained by wave separation and pulse wave analysis). In turn, it has been proposed to determine PWV considering blood pressure (BP) levels (β-PWV), so as to evaluate intrinsic arterial stiffness. It is unknown whether the different approaches used to assess PWV or β-PWV are equivalent and there are few data regarding age- and sex-related reference intervals (RIs) for regional and local PWV, β-PWV and PWV ratio.

AIMS

(1) to evaluate agreement between data from different stiffness indexes, (2) to determine the need for sex-specific RIs, and (3) to define RIs for PWV, β-PWV and PWV ratio in a cohort of healthy children, adolescents and adults.

METHODS

3619 subjects (3-90 y) were included, 1289 were healthy and non-exposed to CV risk factors. Carotid-femoral (cfPWV) and carotid-radial (crPWV) PWV were measured (SphygmoCor System (SCOR)) and PWV ratio (cfPWV/crPWV) was quantified. Local aortic PWV was obtained directly from carotid waves (aoPWV-Carotid; SCOR) and indirectly (generalized transfer function use) from radial (aoPWV-Radial; SCOR) and brachial (aoPWV-Brachial; Mobil-O-Graph system (MOG)) recordings. β-PWV was assessed by means of cardio-ankle brachial (CAVI) and BP-corrected CAVI (CAVIo) indexes. Analyses were done before and after adjustment for BP. Data agreement was analyzed (correlation, Bland-Altman). Mean and standard deviation (age- and sex-related) equations were obtained for PWV parameters (regression methods based on fractional polynomials).

RESULTS

The methods and parameters used to assess aortic stiffness showed different association levels. Stiffness data were not equivalent but showed systematic and proportional errors. The need for sex-specific RIs depended on the parameter and/or age considered. RIs were defined for all the studied parameters. The study provides the largest data set related to agreement and RIs for stiffness parameters obtained in a single population.

Central Versus Peripheral Artery Stiffening and Cardiovascular Risk

The large elastic arteries fulfill an important role in buffering the cyclical changes in blood pressure, which result from intermittent ventricular ejection. With aging and accrual of cardiovascular risk factors, the elastic arteries stiffen, and this process holds a number of deleterious consequences for the cardiovascular system and major organs. Indeed, arterial stiffness is now recognized as an important, independent determinant of cardiovascular disease risk. Additional, important information concerning the mechanisms underlying arterial stiffening has come from longitudinal studies of arterial stiffness. More recently, attention has focused on the role of peripheral, muscular arteries in cardiovascular disease risk prediction and, in particular, the clinical consequences of reversal of the normal gradient of arterial stiffness between central and peripheral arteries, with aging and disease.

Isolated systolic hypertension in the young: a position paper endorsed by the European Society of Hypertension

: Whether isolated systolic hypertension in the young (ISHY) implies a worse outcome and needs antihypertensive treatment is still a matter for dispute. ISHY is thought to have different mechanisms than systolic hypertension in the elderly. However, findings from previous studies have provided inconsistent results. From the analysis of the literature, two main lines of research and conceptualization have emerged. Simultaneous assessment of peripheral and central blood pressure led to the identification of a condition called pseudo or spurious hypertension, which was considered an innocent condition. However, an increase in pulse wave velocity has been found by some authors in about 20% of the individuals with ISHY. In addition, obesity and metabolic disturbances have often been documented to be associated with ISHY both in children and young adults. The first aspect to consider whenever evaluating a person with ISHY is the possible presence of white-coat hypertension, which has been frequently found in this condition. In addition, assessment of central blood pressure is useful for identifying ISHY patients whose central blood pressure is normal. ISHY is infrequently mentioned in the guidelines on diagnosis and treatment of hypertension. According to the 2013 European Guidelines on the management of hypertension, people with ISHY should be followed carefully, modifying risk factors by lifestyle changes and avoiding antihypertensive drugs. Only future clinical trials will elucidate if a benefit can be achieved with pharmacological treatment in some subgroups of ISHY patients with associated risk factors and/or high central blood pressure.

Percentile curves for left ventricle structural, functional and haemodynamic parameters obtained in healthy children and adolescents from echocardiography-derived data

BACKGROUND

Transthoracic echocardiography is the most common non-invasive technique for the study of the left ventricle (LV) and the proximal aorta. Despite the clinical value, there is scarcity of data about reference intervals (RIs) and percentiles for thoracic aorta dimension and LV structural and functional parameters, obtained from population-based studies in children and adolescents. The aim was to generate RIs for LV, haemodynamic and thoracic aorta parameters obtained from transthoracic echocardiography in healthy children, adolescents and young adults from a South-American population.

METHODS

One thousand ninety-five healthy subjects (5-24 years) were studied (M-mode, B-mode and Doppler echocardiography).

RESULTS

RIs for LV structural (diameters, volumes and wall thickness) and functional (stroke volume, cardiac output, cardiac index, transmitral E and A flow waves velocities) parameters; systemic vascular resistance and aortic root diameter were obtained using parametric regression analyzes based on fractional polynomials. Covariate analysis (i.e., adjusting for age, body surface) showed that specific sex-specific RIs were necessary. Then, age, body height (BH), body weight (BW), body surface area (BSA), and sex-specific 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th and 99th percentiles were obtained. Our results were in agreement with and complimentary to available international databases.

CONCLUSION

This study provides RIs for echocardiography-derived haemodynamic, LV (structural and functional) and aortic parameters in children, adolescents and young adults considering data obtained from the largest Argentinean database. In early stages of life an adequate interpretation of echocardiography-derived LV and aortic parameters requires considering age, BH, BW, BSA and/or sex-specific RIs.

Assessment of arterial stiffness variables in patients with rheumatoid arthritis: A mediation analysis

We aimed to study arterial stiffness variables in patients with rheumatoid arthritis (RA), specifically considering their associations with path model mediation analysis. We examined arterial stiffness expressed by the pulse wave velocity (PVW), augmentation index (AIx), distensibility, and clinical and biochemical characteristics in a cohort of 214 RA patients. Variable associations were analysed using multivariate linear regression analysis. We also used path model mediation analysis for PWV variable. Our results indicate that age, systolic blood pressure (SBP), and body mass index (BMI) were significantly associated with PWV, and collectively accounted for 32% of PWV variability. The parallel mediation analysis showed that SBP and BMI accounted for 21% and 7% (a total of 28%) of the total effect of age on PWV, respectively, indicating a partial mediation effect. The associated variables with AIx were age and tender joint count, while those with distensibility were BMI and sex, overall accounting for 16.5% and 4.7% of the variation in AIx and distensibility, respectively. We observed no associations of arterial stiffness with inflammatory variables, disease activity and duration, or cholesterol levels. In conclusion, in our population of RA patients, age is the most important variable that determines the increase in PWV. We have also shown that a significant proportion of the negative effects of age on PWV occurs through increases in SBP and BMI. In our study, lipid and inflammation variables were not associated with an increase in arterial stiffness.

Normal percentile curves for left atrial size in healthy children and adolescents

BACKGROUND

Despite the clinical utility of echocardiography to measure left atrial (LA) structure and function, there are scarcities of data about the percentiles of LA diameter (LA_D ), LA volume (LA_VOL ), and LA volume indexed by body surface area (LA_{VOL / BSA} ) from prospective population-based studies in healthy children and adolescents from the Southern Cone of Latin America.

METHODS

Echocardiographic studies were obtained in 1095 healthy subjects nonexposed to cardiovascular risk factors (5-24 years). Age- and sex-specific reference values of LA_D , LA_VOL , and LA_{VOL / BSA} were generated using parametric regression based on fractional polynomials.

RESULTS

After covariate analysis (ie, adjusting by age, body surface area), specific sex-specific percentiles were evidenced as necessaries. Age- and sex-specific 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th, and 99th percentile and curves were reported. Our percentiles showed high concordance and complementarity with what was previously reported for the population of North American, European, and Asiatic Populations.

CONCLUSIONS

In children and adolescents, the interpretation of the LA size requires sex-related percentiles. This study provides the largest Argentinean database concerning percentile curves of LA_D , LA_VOL , and LA_{VOL / BSA} obtained in healthy children and adolescents. These data are valuable in that they provide values with which data of populations of children, adolescents, and young adults can be compared.

Acute Cardiovascular Adaptation to Strenuous Exercise: An Integrative Ultrasound Study

OBJECTIVES

The aim of this study was to evaluate the acute effects of participation in an Ironman distance triathlon competition on arterial function by ultrasound, in relation to cardiac function and body water content.

METHODS

Twenty-eight male triathletes participating in an Ironman distance competition underwent carotid, femoral, and cardiac ultrasound examinations. Moreover, the presence of extravascular lung water was identified by lung echo B-lines (echogenic coherent wedge-shaped signal with a narrow origin from the hyperechoic pleural line) at rest and within 20 minutes of arrival.

RESULTS

At the end of the competition, athletes showed an increased heart rate (mean ± SD, from 60.2 ± 13.1 to 82.8 ± 15.6 beats/min; P < .0001) and unchanged mean blood pressure (from 93 ± 14 to 91 ± 10 mm Hg; P > .05) in the presence of negligible dehydration (total body water from 48.0 ± 4.0 to 46.5 ± 3.9 kg; P > .05). Cardiac output increased (from 5.5 ± 1.2 to 6.7 ± 2.4 L/min; P < .05) in the presence of an unchanged stroke volume (from 64 ± 14 to 59 ± 16 mL; P > .05) and unchanged left ventricular elastance (from 1.52 ± 0.48 to 1.39 ± 0.48 mm Hg/mL/m² ; P > .05). The mean carotid diameter increased (from 7.19 ± 0.65 to 7.61 ± 0.76 mm; P < .05), whereas the mean femoral diameter was unchanged at the end of the competition (from 10.41 ± 0.83 to 10.49 ± 0.82 mm; P > .05). Carotid intima-media thickness was significantly reduced (from 537 ± 70 to 495 ± 70 μm; P < .05), whereas B-lines increased significantly after the competition (from 1 [0-4] to 12 [5-23]; P < .0001).

CONCLUSIONS

These data suggest different acute functional adaptation in central arteries with respect to peripheral leg vessels.

Reference Intervals and Percentile Curves of Echocardiographic Left Ventricular Mass, Relative Wall Thickness and Ejection Fraction in Healthy Children and Adolescents

Despite the clinical utility of echocardiography to measure cardiac target organ injury (TOI) there are scarcities of data about the reference intervals (RIs) and percentiles of left ventricular (LV) mass (LVM) and derived indexes (LVMI and LVMI^2.7), relative wall thickness (LVRWT) and ejection fraction (LVEF) from population-based studies in children and adolescents. The aim of this study was to generate reference intervals RIs of LVM and derived indexes (LVMI and LVMI^2.7), LVRWT, and LVEF obtained in healthy children, adolescents, and young adults from a South-American population. Echocardiographic studies were obtained in 1096 healthy subjects (5-24 years). Age and sex-specific RIs of LVM, LVMI, LVMI^2.7, LVRWT, and LVEF were generated using parametric regression based on fractional polynomials. After covariate analysis (i.e., adjusting by age, body surface area) specific sex-specific RIs were evidenced as necessaries. Age and sex-specific 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th, and 99th percentile and curves were reported and compared with previously reported RIs. RIs showed high concordance and complementarity with what was previously reported for the population of North-American children (0-18 years old). In conclusion, in children and adolescents the interpretation of the LVM, LVMIs, LVRWT, and LVEF RIs requires sex-related RIs. This study provides the largest Argentinean database concerning RIs and percentile curves of LVM, LVMIs, LVRWT, and LVEF as markers of cardiac TOI obtained in healthy children and adolescents. These data are valuable in that they provide RIs values with which data of populations of children, adolescents can be compared.

Ambulatory pulse wave monitoring: current and future. Opinion paper of Russian Experts

The predictive value of vascular biomarkers such as pulse wave velocity (PWV), central arterial pressure (CAP), and augmentation index (AIx), obtained through pulse wave analysis (PWA) in resting conditions, has been documented in a variety of patient groups and populations. There are appropriate recommendations on their clinical use in clinical practice guidelines of various scientific societies. Operator-independent methods are currently available for estimating vascular biomarkers also in ambulatory conditions. The acceptable accuracy and reproducibility of ambulatory PWA makes it be a promising tool for evaluating vascular biomarkers in daily-life conditions. This approach may provide an opportunity to further improve the early cardiovascular screening in subjects at risk. However, there is no sufficient evidence to support the routine clinical use of PWA in ambulatory conditions at the moment. In particular, long-term outcome studies are needed to show the predictive value of ambulatory PWV, CAP and AIx values.

Reference intervals and percentile curve for left ventricular outflow tract (LVOT), velocity time integral (VTI), and LVOT-VTI-derived hemodynamic parameters in healthy children and adolescents: Analysis of echocardiographic methods association and agreement

BACKGROUND

Echocardiographic reference intervals (RIs) for left ventricular outflow tract (LVOT) and velocity time integral (VTI) are scarce in pediatrics.

AIMS

(a) to generate RIs and percentiles for LVOT, VTI, and hemodynamic variables in healthy children and adolescents from Argentina; (b) to analyze the equivalence between stroke volume (SV), cardiac output (CO), and cardiac index (CI) obtained from two-dimensional echocardiography (2D) and LVOT-VTI analysis with pulsed wave Doppler (PWD); and (c) to analyze the association between subjects' characteristics and VTI and LVOT-VTI-derived parameters.

METHODS

Two-dimensional and PWD studies were done in 385 subjects (5-24 years). Mean and standard deviation age-related and body surface area (BSA)-related equations were obtained for VTI and LVOT-VTI-derived parameters (parametric regression methods based on fractional polynomials). BSA- and age-specific percentiles were determined.

RESULTS

Pulsed wave Doppler- and 2D-derived parameters were positively correlated. However, PWD values were always lower than those from 2D. Specific RIs for PWD and 2D data were necessary. Covariance analysis showed that sex-specific RIs were required for LVOT, but not for VTI, VTI-derived CO and CI. Age-related RIs were obtained for LVOT, LVOT-VTI, and VTI-derived CO and CI. BSA-related RIs for VTI-derived CO and CI were obtained.

CONCLUSIONS

Stroke volume, CO, and CI data from 2D and PWD are not equivalent. An accurate analysis of LVOT-VTI-derived parameters requires considering age and BSA. In this study, age- and BSA-related RIs and percentiles for LVOT, VTI, and hemodynamic parameters in healthy children and adolescents were determined, discriminating data according to the methodological approach (2D or PWD).

Reference Intervals of Central Aortic Blood Pressure and Augmentation Index Assessed with an Oscillometric Device in Healthy Children, Adolescents, and Young Adults from Argentina

Age-related reference intervals (RIs) of central (aortic) systolic blood pressure (cSBP) and augmentation index (cAIx) obtained from large healthy population are lacking in Argentina (South America). Aims. To analyze the existence of associations among cSBP and cAIx with demographic, anthropometric, and hemodynamic parameters and to generate percentile curves and RIs adjusted to each level of age and gender and/or body height. cSBP and cAIx were measured in 1038 healthy children, adolescents, and young adults. First, we evaluated if RIs for males and females were necessary using correlation and covariate analysis. Second, mean (M) and standard deviation (SD) age-related equations were obtained for cSBP and cAIx, using parametric regression methods based on fractional polynomials. Third, age specific percentiles curves were generated. Fourth, body height specific percentiles curves were generated using a similar procedure. The obtained equations (considering age as independent variable) for all subjects (cSBP^0.26 and (cAIx + 12.001)^0.5) were as follows: cSBP Mean = 3.0581 + 0.2189 log(Age) − 0.001044Age; cSBP SD = −0.03919 + 0.1535 log(Age) − 0.004564Age; cAIx mean = 9.5226 − 6.1599 log(Age) + 0.1450Age; cAIx SD = 1.3880 − 0.8468 log(Age) + 0.03212Age. This study, performed in Argentinean healthy children, adolescents, and young adults with ages of 5 to 22 years, provides the first RIs and percentile curves of cSBP and cAIx. Additionally, specific body height-related cAIx percentiles are reported for the analyzed population. The RIs and percentiles contribute to the knowledge of arterial dynamic evolution along the normal aging process and the interpretation of data obtained in clinical research and daily clinical practice.

Reference intervals and percentiles for carotid-femoral pulse wave velocity in a healthy population aged between 9 and 87 years

There is little information regarding age-related reference intervals (RIs) of carotid-femoral pulse wave velocity (cfPWV) for large healthy populations in South America. The aims of this study were to determine cfPWV RIs and percentiles in a cohort of healthy children, adolescents, and adults and to generate year-to-year percentile curves and body-height percentile curves for children and adolescents. cfPWV was measured in 1722 healthy participants with no cardiovascular risk factors (9-87 years, 60% men). First, RIs were evaluated for males and females through correlation and covariate analysis. Then, mean and standard deviation age-related equations were obtained for cfPWV using parametric regression methods based on fractional polynomials and age-specific (year-to-year) percentile curves that were defined using the standard normal distribution. Age-specific first, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th, and 99th percentile curves were calculated. Finally, height-related cfPWV percentile curves for children and adolescents (<21 years) were established. After adjusting for age and blood pressure differences with respect to females, males showed higher cfPWV levels (6.60 vs 6.45 m/s; P < .01). Thus, specific RIs for males and females were reported. The study provides the largest database to date concerning cfPWV in healthy people from Argentina. Specific RIs and percentiles of cfPWV are now available according to age and sex. Specific percentiles of cfPWV according to body height were reported for people younger than 21 years.

Numerical assessment and comparison of pulse wave velocity methods aiming at measuring aortic stiffness

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 (~heart-ankle PTT, ha-PTT; ~brachial-ankle PTT, ba-PTT; ~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.

Comparative Analysis of Arterial Parameters Variations Associated with Inter-Individual Variations in Peripheral and Aortic Blood Pressure: Cross-Sectional Study in Healthy Subjects Aged 2-84 years

INTRODUCTION

The association between arterial parameters and blood pressure (BP) interindividual variations could depend on the arterial segment, BP component (systolic, SBP; diastolic, DBP; pulse pressure, PP) and/or on whether central (cBP) or peripheral (pBP) BP variations are considered.

AIM

To assess and compare arterial parameters variations associated with interindividual variations in cBP and pBP.

METHODS

Healthy subjects (n = 923; 488 males, 2-84 years) were included. pBP and cBP waves were obtained (Mobil-O-Graph; SphygmoCor). Arterial diameter, intima-media thickness, local elastic modulus (carotid, CEM; brachial, BEM; femoral, FEM) and regional (carotid-radial and carotid-femoral pulse wave velocity; crPWV and cfPWV) arterial stiffness were determined. Associations between BP and arterial parameters interindividual variations were analyzed and compared (correlations; linear regressions; slopes comparisons) considering data transformed into z-scores.

RESULTS

Given a variation in z-cSBP or z-pSBP, z-CEM, z-FEM and z-cfPWV (stiffness indexes), were among the parameters with major BP-associated variations. z-crPWV and z-cfPWV, rather than local stiffness indexes were the parameters with major variations associated with z-DBP variations. z-cPP or z-pPP were associated with z-CEM and z-FEM variations, but not with brachial or regional stiffness variations. Most of the arterial parameters-BP slopes did not show significant differences when considering a variation in z-cSBP and z-pSBP. z-CEM and z-FEM were mainly associated with z-cPP and z-pPP variations, respectively.

CONCLUSION

Disregard of age and sex, the variations in arterial parameters associated with BP interindividual variations showed differences depending on whether variations were central or peripheral; in SBP, DBP or PP and depending on the arterial segment considered.

Aortic stiffness aging is influenced by past profound immunodeficiency in HIV-infected individuals: results from the EVAS-HIV (EValuation of Aortic Stiffness in HIV-infected individuals)

OBJECTIVE

We compared aortic stiffness between HIV-infected and HIV-uninfected individuals and examined the determinants of vascular aging during HIV infection.

METHODS

Aortic stiffness using carotid-femoral pulse wave velocity (cf-PWV) was evaluated cross-sectionally between HIV-infected individuals and uninfected controls frequency-matched for age and sex, and longitudinally in a subgroup of HIV-infected individuals. Determinants of elevated cf-PWV levels were assessed using logistic regression. Changes in cf-PWV levels during follow-up (mixed-effect linear regression) and risk factors for achieving cf-PWV below (Group 1) or above the median (Group 2) at last follow-up visit were evaluated only in HIV-infected individuals.

RESULTS

A total of 133 HIV-infected and 135 HIV-uninfected individuals (mean age: 47.7 ± 8.9 years, 91% men) were enrolled. Median cf-PWV at baseline was similar between HIV-infected individuals and controls [7.5 m/s (interquartile range = 6.7-8.4) vs. 7.5 m/s (interquartile range = 6.6-8.4), respectively; P = 0.64]. In multivariable analysis, only mean arterial pressure showed significant association with elevated cf-PWV in the overall population (P = 0.036). In HIV-infected individuals, elevated cf-PWV was associated with current smoking (P = 0.042), and nadir CD4 T-cell count less than 200 cells/μl (P = 0.048). Ninety-one HIV-infected individuals were followed for a mean 7.6 ± 2.0 years. cf-PWV progression was associated with age (P = 0.018), mean arterial pressure (P = 0.020), and nadir CD4 T-cell count (P = 0.005). Patients from Group 2 had higher baseline waist circumference, pulse pressure, and nadir CD4 T-cell count less than 200 cells/μl.

CONCLUSION

We observed no difference in aortic stiffness between HIV-infected and controls. Moreover, aortic stiffness aging was independently associated with past severe immunodeficiency, along with other traditional risk factors. Our results call for early antiretroviral initiation.

Twenty-Four-Hour Ambulatory Pulse Wave Analysis in Hypertension Management: Current Evidence and Perspectives

The predictive value of vascular biomarkers such as pulse wave velocity (PWV), central arterial pressure (CAP), and augmentation index (AIx), obtained through pulse wave analysis (PWA) in resting conditions, has been documented in a variety of patient groups and populations. This allowed to make appropriate recommendations in clinical practice guidelines of several scientific societies. Due to advances in technologies, largely operator-independent methods are currently available for estimating vascular biomarkers also in ambulatory conditions, over the 24 h. According to the acceptable accuracy and reproducibility of 24-h ambulatory PWA, it appears to be a promising tool for evaluating vascular biomarkers in daily life conditions. This approach may provide an opportunity to further improve the early cardiovascular screening in subjects at risk. However, concerning the clinical use of PWA over the 24 h in ambulatory conditions at the moment, there is no sufficient evidence to support its routine clinical use. In particular, long-term outcome studies are needed to show the predictive value of 24-h PWV, CAP, and AIx values, provided by these devices, over and beyond peripheral blood pressure, and to answer the many technical and clinical questions still open. To this regard, the VASOTENS Registry, an international observational prospective study recently started, will help providing answers on a large sample of hypertensive patients recruited worldwide.

HIV infection and aortic stiffness

People living with human immunodeficiency virus (HIV) infection and receiving antiretroviral therapy now have the same life expectancy as the general population. However, they have a higher risk of atherosclerotic cardiovascular events because of a complex and polyfactorial vasculopathy, combining the effects of antiretroviral therapy, the HIV virus itself, immune activation, chronic inflammation and metabolic disturbances. Whether people living with HIV infection experience increased vascular aging compared with the general population remains controversial. To summarize current knowledge of the association between HIV infection and aortic stiffness as a marker of vascular aging. This review included 18 clinical studies in adult populations, published between 2009 and 2016, and identified on PubMed/MEDLINE or other databases. Search terms were aortic stiffness, arterial stiffness, vascular aging, pulse wave velocity and HIV. All 18 studies were observational, and compared groups infected (HIV+) and not infected (HIV-) with HIV. Ten studies (55%) reported no significant differences in aortic stiffness between HIV+ groups and age-matched HIV- control groups. The main reported determinants of aortic stiffness were age, blood pressure, smoking, metabolic syndrome and HIV-related variables, including CD4/CD8 ratio, current T-CD4 count < 200/mm³ and nadir T-CD4+ count < 200/mm³. We found discordant results regarding whether HIV+ patients had increased aortic stiffness compared with HIV- controls. However, HIV-related conditions were associated with vascular health. This association has been confirmed in recent prospective studies. There is emerging evidence that HIV itself and immune activity affect vascular health and the large arteries.

High Blood Pressure States in Children, Adolescents, and Young Adults Associate Accelerated Vascular Aging, with a Higher Impact in Females' Arterial Properties

The aims of the study were to determine (1) whether the presence of High blood pressure (HBP) states in the youth associate a steeper rate of age-related change in arterial geometrical and wall properties with respect to subjects with no previous cardiovascular risk factor (CRF) exposure, (2) in which parameters and in what magnitude, and (3) the existence of a gender-related difference in the impact of this condition on arterial properties. 300 individuals (mean/range: 15/4-29 years; 133 females) were included. Two groups were assembled: (1) Reference: nonprevious exposure to traditional CRF and (2) HBP: subjects with arterial hypertension and/or elevated blood pressure (BP) levels during the study. Additionally, HBP subjects were separated in BP-related subgroups. Measured parameters were (1) central (aortic) arterial BP and aortic pulse wave analysis parameters, (2) carotid and femoral artery local (pressure-strain elastic modulus) and regional (pulse wave velocity; PWV) stiffness, and (3) arterial diameters and carotid intima-media thickness (CIMT). Age-related changes in these parameters (absolute values and z-scores) were explored by obtaining simple linear regression models for each group. HBP presented a steeper rate of change (accelerated vascular aging; VA) for most of the parameters assessed, mainly in central (aortic) hemodynamics. VA increased as the HBP level got higher. Both males' and females' aging rates were affected by this condition, but females presented a more marked relative age-related increase with HBP exposure. HBP states in the youth gradually associate accelerated VA, with a progressive hemodynamic-structural-functional onset of damage, with females presenting a more marked relative HBP-associated arterial repercussion.

Aortic–Brachial Pulse Wave Velocity Ratio

Aortic stiffness, a cardiovascular risk factor, depends on the operating mean arterial pressure (MAP). The impact of aortic stiffness on cardiovascular outcomes is proposed to be mediated by the attenuation or the reversal of the arterial stiffness gradient. We hypothesized that arterial stiffness gradient is less influenced by changes in MAP. We aimed to study the relationship between MAP and aortic stiffness, brachial stiffness, and arterial stiffness gradient. In a cross-sectional study of a dialysis cohort (group A, n=304) and a cohort of hypertensive or kidney transplant recipient with an estimated glomerular filtration rate of >45 mL/min/1.73 m 2 (group B, n=114), we assessed aortic and brachial stiffness by measuring carotid–femoral and carotid–radial pulse wave velocities (PWV). We used aortic–brachial PWV ratio as a measure of arterial stiffness gradient. Although there was a positive relationship between MAP and carotid–femoral PWV ( R 2 =0.10 and 0.08; P <0.001 and P =0.003) and MAP and carotid–radial PWV ( R 2 =0.22 and 0.12; P <0.001 and P <0.001), there was no statistically or clinically significant relationship between MAP and aortic–brachial PWV ratio ( R 2 =0.0002 and 0.0001; P =0.8 and P =0.9) in group A and B, respectively. Dialysis status and increasing age increased the slope of the relationship between MAP and cf-PWV. However, we found no modifying factor (age, sex, dialysis status, diabetes mellitus, cardiovascular disease, and class of antihypertensive drugs) that could affect the lack of relationship between MAP and aortic–brachial PWV ratio. In conclusion, these results suggest that aortic–brachial PWV ratio could be considered as a blood pressure–independent measure of vascular aging.

Diabetes Mellitus, Arterial Wall, and Cardiovascular Risk Assessment

Diabetes mellitus is an independent risk factor for atherothrombotic cardiovascular disease. Adults with diabetes are two to four times more likely to develop heart disease or stroke than adults without diabetes. The two major features of diabetes, i.e., hyperglycemia and insulin-resistance, trigger arterial stiffening and increase the susceptibility of the arterial wall to atherosclerosis at any given age. These pathological changes in the arterial wall may provide a functional and structural background for cardiovascular events. The present paper provides a critical overview of the clinical evidence linking diabetes-related metabolic abnormalities to cardiovascular risk, debates the pathophysiologic mechanisms through which insulin resistance and hyperglycemia may affect the arterial wall, and discusses the associations between vascular biomarkers, metabolic abnormalities and cardiovascular events.

Arterial stiffness, atherosclerosis and cardiovascular risk: Pathophysiologic mechanisms and emerging clinical indications

Arterial stiffness results from a degenerative process affecting mainly the extracellular matrix of elastic arteries under the effect of aging and risk factors. Changes in extracellular matrix proteins and in the mechanical properties of the vessel wall related to arterial stiffening may activate number of mechanisms involved also in the process of atherosclerosis. Several noninvasive methods are now available to estimate large artery stiffness in the clinical setting, including carotid-femoral pulse wave velocity, the reference for aortic stiffness estimate, and local distensibility measures of superficial arteries, namely carotid and femoral. An independent predictive value of arterial stiffness for cardiovascular events has been demonstrated in general as well as in selected populations, and reference values adjusted for age and blood pressure have been established. Thus, arterial stiffness is emerging as an interesting tissue biomarker for cardiovascular risk stratification and estimation of the individual "biological age". This paper overviews the mechanisms accounting for development and progression of arterial stiffness and for associations between arterial stiffness, atherosclerotic burden and incident cardiovascular events, summarizes the evidence and caveat for clinical use of stiffness as surrogate marker of cardiovascular risk, and briefly outlines some emerging methods for large artery stiffness characterization.