Central Arterial Dynamic Evaluation from Peripheral Blood Pressure Waveforms Using CycleGAN: An In Silico Approach.

Arterial stiffness is a major condition related to many cardiovascular diseases. Traditional approaches in the assessment of arterial stiffness supported by machine learning techniques are limited to the pulse wave velocity (PWV) estimation based on pressure signals from the peripheral arteries. Nevertheless, arterial stiffness can be assessed based on the pressure-strain relationship by analyzing its hysteresis loop. In this work, the capacity of deep learning models based on generative adversarial networks (GANs) to transfer pressure signals from the peripheral arterial region to pressure and area signals located in the central arterial region is explored. The studied signals are from a public and validated virtual database. Compared to other works in which the assessment of arterial stiffness was performed via PWV, in the present work the pressure-strain hysteresis loop is reconstructed and evaluated in terms of classical machine learning metrics and clinical parameters. Least-square GAN (LSGAN) and Wasserstein GAN with gradient penalty (WGAN-GP) adversarial losses are compared, yielding better results with LSGAN. LSGAN mean ± standard deviation of error for pressure and area pulse waveforms are 0.8 ± 0.4 mmHg and 0.1 ± 0.1 cm2, respectively. Regarding the pressure-strain elastic modulus, it is achieved a mean absolute percentage error of 6.5 ± 5.1%. GAN-based deep learning models can recover the pressure-strain loop of central arteries while observing pressure signals from peripheral arteries.

Blood Pressure Morphology Assessment from Photoplethysmogram and Demographic Information Using Deep Learning with Attention Mechanism.

Arterial blood pressure (ABP) is an important vital sign from which it can be extracted valuable information about the subject's health. After studying its morphology it is possible to diagnose cardiovascular diseases such as hypertension, so ABP routine control is recommended. The most common method of controlling ABP is the cuff-based method, from which it is obtained only the systolic and diastolic blood pressure (SBP and DBP, respectively). This paper proposes a cuff-free method to estimate the morphology of the average ABP pulse (ABPM¯) through a deep learning model based on a seq2seq architecture with attention mechanism. It only needs raw photoplethysmogram signals (PPG) from the finger and includes the capacity to integrate both categorical and continuous demographic information (DI). The experiments were performed on more than 1100 subjects from the MIMIC database for which their corresponding age and gender were consulted. Without allowing the use of data from the same subjects to train and test, the mean absolute errors (MAE) were 6.57 ± 0.20 and 14.39 ± 0.42 mmHg for DBP and SBP, respectively. For ABPM¯, R correlation coefficient and the MAE were 0.98 ± 0.001 and 8.89 ± 0.10 mmHg. In summary, this methodology is capable of transforming PPG into an ABP pulse, which obtains better results when DI of the subjects is used, potentially useful in times when wireless devices are becoming more popular.

Analysis of ischaemic crisis using the informational causal entropy-complexity plane.

In the present work, an ischaemic process, mainly focused on the reperfusion stage, is studied using the informational causal entropy-complexity plane. Ischaemic wall behavior under this condition was analyzed through wall thickness and ventricular pressure variations, acquired during an obstructive flow maneuver performed on left coronary arteries of surgically instrumented animals. Basically, the induction of ischaemia depends on the temporary occlusion of left circumflex coronary artery (which supplies blood to the posterior left ventricular wall) that lasts for a few seconds. Normal perfusion of the wall was then reestablished while the anterior ventricular wall remained adequately perfused during the entire maneuver. The obtained results showed that system dynamics could be effectively described by entropy-complexity loops, in both abnormally and well perfused walls. These results could contribute to making an objective indicator of the recovery heart tissues after an ischaemic process, in a way to quantify the restoration of myocardial behavior after the supply of oxygen to the ventricular wall was suppressed for a brief period.

Resynchronization improves heart-arterial coupling reducing arterial load determinants.

BACKGROUND: Cardiac resynchronization therapy (CRT) has benefits on left ventricle (LV) performance, but its mid-term effects on LV load and LV-arterial coupling are unknown. AIMS: To evaluate CRT mid-term effects on LV-arterial coupling, arterial load and its determinants, and the association between CRT-dependent aortic haemodynamic changes and the arterial biomechanics. METHODS AND RESULTS: Cardiac and aortic echographies were done in 25 patients (age: 61 ± 12 years; 14 men; New York Heart Association functional classes III-IV; LV ejection fraction = 28 ± 7%, QRS = 139 ± 20 ms) before and after (23 ± 12 days) CRT. Standard structural and functional parameters and dyssynchrony indices were evaluated. Ascending aorta flow and diameter waveforms were measured. Central pressure was derived using a transfer function and the diameter calibration method. Calculus: arterial elastance (EA); aortic impedance (Zc) and distensibility (AD); systemic resistances (SVR), total compliance (CT); global reflection coefficient; LV end-systolic elastance (EES); and LV-arterial coupling (EA/EES). After CRT EA diminished (-30%;P = 0.001), EES increased (29%; P = 0.001) and EA/EES improved (pre-CRT: 2.9 ± 0.9, post-CRT: 1.6 ± 0.7; P = 0.001). Arterial elastance changes were associated with changes in arterial properties. Cardiac resynchronization therapy was associated with pressure-independent increase in mean aortic diameter (pre-CRT: 30.0 ± 4.0 mm, post-CRT: 33.0 ± 5.1 mm; P = 0.005) and distensibility (pre-CRT: 3.8 ± 2.6 × 10(-3)mmHg(-1), post-CRT: 6.4 ± 2.5 × 10(-3) mmHg(-1); P = 0.002), and Zc reduction (pre-CRT: 3.5 ± 1.8 × 10(-2)mmHg.s/mL, post-CRT:1.9 ± 0.8 × 10(-2) mmHg.s/mL; P = 0.001) and SVR (pre-CRT:1.7 ± 0.4 mmHg.s/mL, post-CRT:1.0 ± 0.3 mmHg.s/mL; P = 0.001). Changes in EA determinants were associated with changes in aortic flow. CONCLUSION: Early after CRT central and peripheral arterial biomechanics improved, determining a pressure-independent increase in aortic diameter and a reduction in arterial load. Left ventricular systolic performance and LV-arterial coupling were enhanced. Arterial biomechanical changes were associated with aortic flow changes.

Different Types of Training Lead to Different Levels of Cardiovascular Energy Dissipation: Young Soccer Players Versus Ballet Dancers.

INTRODUCTION: Arterial wall viscosity is a source of energy dissipation that takes place during mechanical transduction. In our previous studies, a "global" damping effect in endurance training athletes was introduced, verifying that endurance-athletes dissipate greater pulsatile energy in the circulation compared with healthy untrained subjects. OBJECTIVE: To investigate the wall energy dissipation in the vascular bed for each beat and within the conceptual framework of ventricular-arterial coupling, in order to elucidate if different types of training could lead to differentiated levels of cardiovascular energy dissipation. MATERIALS AND METHODS: Data from subjects with different kinds of training (soccer players and ballet dancers) have been collected noninvasively and compared with a control group of untrained individuals to analyse the differentiating characteristics of the subjects, especially in terms of Stroke Work Dissipation (WDIS). RESULTS: In the endurance-trained individuals, an enhanced WDIS has been observed compared to the untrained individuals (p<0.05). However, non-significant differences were found regarding ballet-dancers group. CONCLUSION: Changes in wall energy dissipation are developed under high intensity endurance training routines.

Intra-aortic balloon pumping reduces the increased arterial load caused by acute cardiac depression, modifying central and peripheral load determinants in a time- and flow-related way.

The mechanisms that explain intra-aortic balloon pumping (IABP) effects are not completely understood, and attributing them only to pressure-associated changes in cardiac function would be an oversimplification. Since IABP modifies the aortic and systemic blood-flow pattern, flow-related effects could be expected. To characterize effects of acute heart failure (AHF) on the arterial biomechanics; IABP effects on the arterial biomechanics during AHF, and their potential time-dependence; the association between hemodynamics and biomechanical changes during AHF and IABP. Sheep (n = 6) aortic pressure, flow, and diameter were measured: (1) before (Basal) and (2) 1-3 (HF(1-3)) and 28-30 (HF(28-30)) min after starting halothane to induce AHF; and (3) at specific times (1-3, 14-15 and 28-30 min) during IABP assistance. Calculus: aortic characteristic impedance (Z(c)), beta stiffness (ß), incremental (E(INC)) and pressure-strain elastic modulus (E(P)); total arterial compliance (C(G)), total systemic vascular resistance and wave propagation parameters. (1) AHF resulted in an acute increase in aortic and systemic stiffness (HF(28-30) % changes with respect to Basal conditions: ß +217%, E (P) +143%, E(INC) +101%, Z(c) +52%, C(G) -13%), associated with the reduction in the aortic blood flow; (2) during AHF IABP resulted in acute beneficial changes aortic and systemic biomechanics (% changes in IABP(1-3) with respect HF(28-30): ß -62%, E(P) -68%, E (INC) -66%, Z(c) -38%, C(G) 66%), and in wave propagation parameters, (3) IABP-related changes were time-dependent and associated with changes in aortic blood flow. Aortic and systemic biomechanical and impedance properties are detrimentally modified during AHF, being the changes rapidly reverted during IABP. IABP-related beneficial changes in arterial biomechanics were time-dependent and associated with IABP capability to increase blood flow.

Post-implant evaluation of the anastomotic mechanical and geometrical coupling between human native arteries and arterial cryografts implanted in lower-limb: mechanical, histological and ultraestructural studies of implanted cryografts.

BACKGROUND: There is an urgent need of vascular substitutes (VS) to be used in lower limb revascularization procedures when autologous veins are not available and synthetic prosthesis are contraindicated. Since the mechanical differences with respect to native vessels are determinants of the VS failure, the substitutes should have mechanical properties similar to those of the recipient vessels. The use of cryopreserved arteries (cryografts) could overcome limitations of available VS. These work aims were to characterize (a) native vessels/implanted cryografts mechanical and geometrical coupling, (b) cryografts capability to ensure mismatch levels lesser than those expected for expanded polytetrafluoroethylene (ePTFE), (c) cryografts functional properties considering their histological and ultra-structural characteristics. METHODS: Instantaneous pressure (mechano-transducers) and diameter (B-mode echography) were obtained in implanted femoro-popliteal, ileo-femoro-popliteal and axilo-humeral cryografts (n=8), in femoral arteries from recipients (n=8), recipient-like (n=15) and multiorgan donors-like (n=15) subjects, and in ePTFE segments (n=10). Calculus: (a) Mechanical parameters: elastic modulus, arterial compliance, distensibility and characteristic impedance; (b) Arterial remodeling: diameter, wall thickness, cross-sectional area and wall-to-lumen ratio; (c) Native vessels/VS coupling. Histological and structural analysis were done in explanted femoro-popliteal and axilo-humeral cryografts (n=7). RESULTS: Post-implant the cryografts remodeled. Their stiffness increased and the conduit function diminished. Remodeling resulted in an improvement in native vessels/cryograft coupling, which was always better than native vessels/ePTFE coupling. CONCLUSIONS: Post-implant cryograft remodeling improved native vessels/cryografts coupling. Cryografts would have mechanical and geometrical advantages over ePTFE. Anastomotic cryograft remodeling differed from that expected only due to haemodynamic factors. The structural properties of the remodeled cryografts contribute to explain their functional characteristics.

The endothelium modulates the arterial wall mechanical response to intra-aortic balloon counterpulsation: in vivo studies.

Intra-aortic balloon pump (IABP) benefits could depend on variations in the cardiovascular biomechanical properties associated with blood flow-induced endothelium-dependent changes. However, if IABP results in changes in the peripheral artery biomechanics and if the endothelium plays a role in these potential changes remains unknown. The aim of this study is to characterize acute IABP effects on peripheral artery biomechanics in control and acute heart failure (AHF) states and the role of the endothelium in IABP effects on peripheral artery biomechanics. Pressure and diameter were recorded in sheep (n= 7) iliac arteries (IAs), before and during 1:2 IABP, during four states: (i) control with intact IA; (ii) AHF with intact IA; (iii) control with de-endothelialized (DE) (mechanical rubbing) IA; and (iv) AHF with DE IA. Arterial distensibility, elastic modulus, and conduit function (CF) (1/characteristic impedance) were calculated. The results of this study include: (i) during control conditions, IABP resulted in intact IA dilatation, stiffness reduction, and CF increase; (ii) AHF induction determined a reduction in intact IA diameter and CF, and a stiffness increase. These changes reverted during IABP; (iii) the increase in IA stiffness observed after DE remained unchanged during IABP; (iv) in DE IA, AHF did not result in diameter or stiffness changes; and (v) IABP during AHF did not associate changes in diameter or stiffness in the DE IA. In conclusion, during control and AHF states, IABP results in IA dilatation and stiffness reduction. The integrity of the endothelial layer would be critical for the IABP-associated changes in IA biomechanics.

A Delineator for Arterial Blood Pressure Waveform Analysis Based on a Deep Learning Technique.

A deep learning technique based on semantic segmentation was implemented into the blood pressure detection points field. Two models were trained and evaluated in terms of a reference detector. The proposed methodology outperforms the reference detector in two of the three classic benchmarks and on signals from a public database that were modified with realistic test maneuvers and artifacts. Both models differentiate regions with valid information and artifacts. So far, no other delineator had shown this capacity.

Energy Dissipation in the Arterial Wall Analyzed by Allometric Relationships.

INTRODUCTION: Allometry describes the disproportionate changes in shape, size or function that are observed when comparing separate isolated features in animals spanning a range of body sizes. Scaling of the energy dissipation has been also observed in warm blooded animals, essentially varying as mammal's body mass (BM). Part of the energy stored in the arterial wall during elastic distension corresponding to the viscous deformation is dissipated within the arterial wall. OBJECTIVE: To elucidate the allometric existing relationship between BM and arterial wall viscosity, as a measure of energy dissipation. MATERIAL AND METHODS: Arterial viscous dissipation (WVD) was assessed in dogs, sheep, and humans in terms of BM and heart rate (HR) variations. RESULTS: An allometric law was found between WVD and BM, jointly with the assessment of WVD in terms of HR. CONCLUSION: The existence of a power-law link for viscous dissipation and BM that involve different mammals was demonstrated.

Predictive Cardiometabolic Risk Profiling of Patients Using Vascular Age in Liver Transplantation.

Liver transplantation is the last therapeutic option in patients with end-stage liver diseases. The adequate clinical management of transplant-patients impacts their vital prognosis and decisions on many occasions are made from the interaction of multiple variables involved in the process. This work is based on the National Liver Transplantation Program in Uruguay. We performed predictive analysis of cardiometabolic diseases on the transplanted cohort between 2014 and 2019, considering vascular age as a key factor. This aims at classification of the cohort based on the vascular age of the evaluated patients before transplantation for risk-profiling. Predicted high-risk group of the patients showed substantial deterioration of post-transplant health-conditions, including higher mortality rate. In our knowledge, this is the first study in Latin America incorporating vascular age toward predictive analysis of cardiometabolic risk factors in liver transplantations. Predictive risk-modeling using vascular age in a pre-transplantation scenario provides significant opportunity for early prediction of post-transplant risk factors, leading to efficient treatment with anticipation.

Vascular cryografts offer better biomechanical properties in chronically hemodialyzed patients: role of cryograft type, arterial pathway, and diabetic nephropathy as matching determinants.

This study aimed to characterize the following: (i) in chronically hemodialyzed subjects (CHDSs), with and without diabetic nephropathy (DN), and in healthy subjects (non-CHDSs) different arterial pathways stiffness to determine potential pathology-dependent, etiology- and/or pathway-dependent differences; and (ii) the biomechanical mismatch (BM) between arteries from non-CHDSs or CHDSs (with and without DN) and arterial cryografts, venous cryografts, and synthetic prosthesis to determine arterial pathway, pathology, and/or etiology-related differences in the substitute of election in terms of BM. Carotid-femoral and carotid-brachial pulse wave velocity (PWV) were measured in 30 non-CHDSs and 71 CHDSs (11 with DN). In addition, PWV was measured in arterial (elastic and muscular) and venous cryografts and in expanded polytetrafluorethylene prosthesis. The arterial pathways regional differences and the subjects' arterial pathways-substitutes BM were calculated. Arterial stiffness levels and regional differences were higher in CHDS than in non-CHDS. Among CHDS, those with DN showed higher stiffness in the aorto-femoral pathway and larger regional differences. Cryografts showed always the least BM. Non-CHDS and CHDS differed in the cryograft of election. In CHDS, the BM was related with the cryograft type, arterial pathway, and renal disease etiology. The BM could be minimized, selecting the most adequate cryograft type, taking into account the recipient specific characteristic (i.e., arterial pathway and renal disease etiology).

Internet of Things and Artificial Intelligence in Healthcare During COVID-19 Pandemic-A South American Perspective.

The shudders of the COVID-19 pandemic have projected newer challenges in the healthcare domain across the world. In South American scenario, severe issues and difficulties have been noticed in areas like patient consultations, remote monitoring, medical resources, healthcare personnel etc. This work is aimed at providing a holistic view to the digital healthcare during the times of COVID-19 pandemic in South America. It includes different initiatives like mobile apps, web-platforms and intelligent analyses toward early detection and overall healthcare management. In addition to discussing briefly the key issues toward extensive implementation of eHealth paradigms, this work also sheds light on some key aspects of Artificial Intelligence and the Internet of Things along their potential applications like clinical decision support systems and predictive risk modeling, especially in the direction of combating the emergent challenges due to the COVID-19 pandemic.

Reversal blood flow component as determinant of the arterial functional capability: theoretical implications in physiological and therapeutic conditions.

In several physiological, pathological, and therapeutic circumstances, the arterial blood flow is acutely modified, increasing, in some vascular segments the reversal (SSR) and oscillatory (SSO) components of the shear stress. Recently, in an in vivo model we found a relationship between acute changes in SSR and SSO, and variations in the arterial viscoelasticity. As the arterial viscoelasticity and diameter are the main determinants of the arterial buffering (BF) and conduit (CF) functions, changes in those functions could be expected associated with variations in SSR and SSO. The aim was to analyze the association between acute increases in SSR and SSO, and changes in the aortic CF and BF. Aortic flow, pressure, and diameter were measured in 16 sheep under basal and high reversal and oscillatory flow conditions (high SSR and SSO). Aortic BF and CF were quantified, and their potential association with the SSR and SSO components were analyzed. During high reversal flow rate conditions, a smooth muscle contraction-pattern was evidenced, with an increase in BF and a decrease in CF. Changes in BF and CF were associated with the changes in SSR and SSO. The acute effects on the arterial wall biomechanics of variations in SSR and SSO could contribute to comprehend their chronic effects, and the meaning of the acute vascular effects of changes in SSR and SSO would depend on the situation. Increases in SSR and SSO could be associated with smooth muscle tone increase-dependent changes in arterial BF and CF.

Preservation of muscular and elastic artery distensibility after an intercontinental cryoconserved exchange: theoretical advances in arterial homograft generation and utilization.

While the situation of tissue donation and transplantation differs between Latin American and European countries, a common problem is tissue deficiency. Hence, at present, there is a pressing need to generate alternatives so as to increase the possibilities of obtaining the requested materials. Consequently, it would be of significant interest to establish an intercontinental network for tissue exchange, to improve international cooperation, and to help patients that need tissue transplantation, and to evaluate the feasibility of using an intercontinental network for the exchange of cryopreserved arteries (cryografts), preserving the arterial distensibility and ensuring a reduced native artery-cryograft biomechanical mismatch. Distensibility was studied in ovine arteries divided into three groups: intact (in vivo tests, conscious animals), fresh control (in vitro tests immediately after the artery excision, Uruguay), and cryografts (in vitro tests of cryopreserved-transported-defrosted arteries, Spain). Histological studies were performed so as to analyze changes in the endothelial layer and elastic components. The comparison between fresh control and cryografts showed that neither the cryopreservation nor the exchange network impaired the distensibility, despite the expected histological changes found in the cryografts. The comparison between intact and cryografts showed that the cryografts would be capable of ensuring a reduced biomechanical mismatch. The cryopreservation and the intercontinental network designed for artery exchange preserved the arterial distensibility. It could be possible to transfer cryografts between Latin America and Europe to be used in cardiovascular surgeries and/or for tissue banking reprocessing, with basic biomechanical properties similar to those of the fresh and/or native arteries.

Smooth muscle-dependent changes in aortic wall dynamics during intra-aortic counterpulsation in an animal model of acute heart failure.

PURPOSE: Intra-aortic balloon pumping (IABP) may modify arterial biomechanics; however, its effects on arterial wall properties during acute cardio-depression have not yet been fully explored. This dynamical study was designed to characterize the effects of IABP on aortic wall mechanics in an in vivo animal model of acute heart failure. METHODS: Aortic pressure, diameter and blood flow were measured in six anesthetized sheep with acute cardio-depression by halothane (4%), before and during IABP (1:2). Aortic characteristic impedance and aortic wall stiffness indexes were calculated. RESULTS: acute experimental cardio-depression resulted in a reduction in mean aortic pressure (p<0.05) and an increase in the characteristic impedance (p<0.005), incremental elastic modulus (p<0.05), stiffness index (p<0.05) and Peterson elastic modulus (p<0.05). IABP caused an increase in the cardiac output (p<0.005) and a reduction in the systemic vascular resistances (p<0.05). In addition, the aortic impedance, incremental elastic modulus, stiffness index and Peterson modulus were significantly reduced during IABP (p<0.05). CONCLUSIONS: Our findings show that IABP caused changes in aortic wall impedance and intrinsic wall properties, improving the arterial functional capability and the left ventricular afterload by a reduction in both. Systemic vascular resistances and aortic stiffness were also improved by means of smooth muscle-dependent mechanisms.

Vascular access localization determines regional changes in arterial stiffness.

BACKGROUND: Vascular access (VA) dysfunction is a common cause of hospitalization in chronically hemodialyzed patients (CHP) limiting the improvement in health and has been largely studied in order to decrease the morbidity events that involves both the artery and the vein used in the construction of the fistula. In parallel, patients in end-stage renal failure show an increase in arterial stiffness. AIM: The aims of this work were: (a) to evaluate arterial stiffness through pulse wave velocity (PWV) measurements in the carotid-brachial pathway where the arteriovenous fistulae (AVF) was constructed, and (b) to determine possible differences in arterial stiffness between the carotid-brachial pathway with and without VA. METHODS: PWV, clinical and biochemical parameters were measured in 38 CHP. PWV was obtained in the carotid-femoral, and in the left and right carotid-brachial pathway. RESULTS: Carotid-brachial PWV determination in upper limbs with AVF (10.07 +/- ;2.43 m/s) showed significantly lower values than those observed in the contra-lateral arm without VA (11.55 +/- ;2.27 m/s). Curiously, the PWV value observed in arms with an AVF was significantly lower in diabetic than in non-diabetic hemodialyzed patients (NDHP) (8.00 +/- ;2.86 m/s and 10.38 +/- ;2.33 m/s; respectively). Measurements of PWV in the carotid-femoral pathway in CHP showed a mean value of 14.09 +/- ;3.12 m/s. Carotid-femoral PWV in NDHP (14.06 +/- ;2.44 m/s) was significantly lower than that observed in the diabetic patients (16.87 +/- ;3.42 m/s). CONCLUSIONS: Carotid-brachial PWV values obtained in the upper limbs, in which VAs were constructed, were significantly lower than that measured in intact arteries in the contra-lateral pathway in CHP.

Fractional-order viscoelasticity applied to describe uniaxial stress relaxation of human arteries.

Viscoelastic models can be used to better understand arterial wall mechanics in physiological and pathological conditions. The arterial wall reveals very slow time-dependent decays in uniaxial stress-relaxation experiments, coherent with weak power-law functions. Quasi-linear viscoelastic (QLV) theory was successfully applied to modeling such responses, but an accurate estimation of the reduced relaxation function parameters can be very difficult. In this work, an alternative relaxation function based on fractional calculus theory is proposed to describe stress relaxation experiments in strips cut from healthy human aortas. Stress relaxation (1 h) was registered at three incremental stress levels. The novel relaxation function with three parameters was integrated into the QLV theory to fit experimental data. It was based in a modified Voigt model, including a fractional element of order alpha, called spring-pot. The stress-relaxation prediction was accurate and fast. Sensitivity plots for each parameter presented a minimum near their optimal values. Least-squares errors remained below 2%. Values of order alpha = 0.1-0.3 confirmed a predominant elastic behavior. The other two parameters of the model can be associated to elastic and viscous constants that explain the time course of the observed relaxation function. The fractional-order model integrated into the QLV theory proved to capture the essential features of the arterial wall mechanical response.

Regional differences in veins wall viscosity, compliance, energetics and damping: analysis of the pressure-diameter relationship during cyclical overloads.

BACKGROUND: The characterization of the dynamic process of veins walls is essential to understand venous functioning under normal and pathological conditions. However, little work has been done on dynamic venous properties. AIM: To characterize vein compliance (C), viscosity (eta), peak-strain (W St) and dissipated (W(D)) energy, damping (zeta), and their regional differences in order to evaluate their role in venous functioning during volume-pressure overloads. METHODS: In a mock circulation, pressure (P) and diameter (D) of different veins (anterior cava, jugular and femoral; from 7 sheep), were registered during cyclical volume-pressure pulses. From the P-D relationship, C, W(St) and zeta (at low and high P-D levels), eta and W(D) were calculated. RESULTS: For each vein there were P-dependent differences in biomechanical, energetics, and damping capability. There were regional-differences in C, eta), W(St) and W(D) (p<0.05), but not in zeta. CONCLUSION: The regional-dependent differences in dynamics and energetics, and regional-similitude in damping could be important to ensure venous functioning during acute overloads. The lower C and higher W(St) and W(D) found in back-limb veins (femoral), commonly submitted to high volume-pressure loads (i.e. during walking), could be considered relevant to ensure adequate venous system functionality and venous wall protection simultaneously.

Quantitative Vascular Evaluation: From Laboratory Experiments to Point-of-Care Patient (Experimental Approach).

This paper illustrates the evolution of our knowledge of arterial mechanics from our initial research works up to the present time. Several techniques focusing on this topic in terms of our experience are discussed. An interdisciplinary team composed by different institutions from Argentina, Uruguay, France and Spain was created to conduct research, to train human resources and to fulfill the inevitable social role of gaining access to technological innovation to improve public health.