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.

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.

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.

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.

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.

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.

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.

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.

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

To enhance the efficiency of patient-specific risk stratification and diagnosis, an assessment of arterial structural and functional changes associated to a vascular disease in both early and advanced stages have been proposed, with the objective of limiting the progression or revert vascular alterations. In this connection, an interdisciplinary international partnership made up by research institutions from France, Argentina, Uruguay and Spain was established, with the objective of contributing to the evaluation and follow-up of factors involved in the physiopathology of cardiometabolic diseases and human aging. Several studies, such as the effect of hypertension in large arteries, alterations in arterial wall viscosity, stiffness and inertia, endothelial function and vascular reactivity, cardiovascular risk improvement, vascular age assessment and cryografts vascular response evaluation were carried out as a result of this international collaboration during the last twenty-five years.

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.

A Novel Interpretation for Arterial Pulse Pressure Amplification in Health and Disease.

Arterial pressure waves have been described in one dimension using several approaches, such as lumped (Windkessel) or distributed (using Navier-Stokes equations) models. An alternative approach consists of modeling blood pressure waves using a Korteweg-de Vries (KdV) equation and representing pressure waves as combinations of solitons. This model captures many key features of wave propagation in the systemic network and, in particular, pulse pressure amplification (PPA), which is a mechanical biomarker of cardiovascular risk. The main objective of this work is to compare the propagation dynamics described by a KdV equation in a human-like arterial tree using acquired pressure waves. Furthermore, we analyzed the ability of our model to reproduce induced elastic changes in PPA due to different pathological conditions. To this end, numerical simulations were performed using acquired central pressure signals from different subject groups (young, adults, and hypertensive) as input and then comparing the output of the model with measured radial artery pressure waveforms. Pathological conditions were modeled as changes in arterial elasticity (E). Numerical results showed that the model was able to propagate acquired pressure waveforms and to reproduce PPA variations as a consequence of elastic changes. Calculated elasticity for each group was in accordance with the existing literature.

Uncertainty Quantification in a Patient-Specific One-Dimensional Arterial Network Model: EnKF-Based Inflow Estimator.

Successful clinical use of patient-specific models for cardiovascular dynamics depends on the reliability of the model output in the presence of input uncertainties. For 1D fluid dynamics models of arterial networks, input uncertainties associated with the model output are related to the specification of vessel and network geometry, parameters within the fluid and wall equations, and parameters used to specify inlet and outlet boundary conditions. This study investigates how uncertainty in the flow profile applied at the inlet boundary of a 1D model affects area and pressure predictions at the center of a single vessel. More specifically, this study develops an iterative scheme based on the ensemble Kalman filter (EnKF) to estimate the temporal inflow profile from a prior distribution of curves. The EnKF-based inflow estimator provides a measure of uncertainty in the size and shape of the estimated inflow, which is propagated through the model to determine the corresponding uncertainty in model predictions of area and pressure. Model predictions are compared to ex vivo area and blood pressure measurements in the ascending aorta, the carotid artery, and the femoral artery of a healthy male Merino sheep. Results discuss dynamics obtained using a linear and a nonlinear viscoelastic wall model.

Deformable Surface Model for the Evaluation of Abdominal Aortic Aneurysms Treated with an Endovascular Sealing System.

Rupture of abdominal aortic aneurysms (AAA) is responsible for 1-3% of all deaths among the elderly population in developed countries. A novel endograft proposes an endovascular aneurysm sealing (EVAS) system that isolates the aneurysm wall from blood flow using a polymer-filled endobag that surrounds two balloon-expandable stents. The volume of injected polymer is determined by monitoring the endobag pressure but the final AAA expansion remains unknown. We conceived and developed a fully deformable surface model for the comparison of pre-operative sac lumen size and final endobag size (measured using a follow-up scan) with the volume of injected polymer. Computed tomography images were acquired for eight patients. Aneurysms were manually and automatically segmented twice by the same observer. The injected polymer volume resulted 9% higher than the aneurysm pre-operative lumen size (p < 0.05), and 11% lower than the final follow-up endobag volume (p < 0.01). The automated method required minimal user interaction; it was fast and used a single set of parameters for all subjects. Intra-observer and manual vs. automated variability of measured volumes were 0.35 ± 2.11 and 0.07 ± 3.04 mL, respectively. Deformable surface models were used to quantify AAA size and showed that EVAS system devices tended to expand the sac lumen size.

Hydration Status Is Associated with Aortic Stiffness, but Not with Peripheral Arterial Stiffness, in Chronically Hemodialysed Patients.

Background. Adequate fluid management could be essential to minimize high arterial stiffness observed in chronically hemodialyzed patients (CHP). Aim. To determine the association between body fluid status and central and peripheral arterial stiffness levels. Methods. Arterial stiffness was assessed in 65 CHP by measuring the pulse wave velocity (PWV) in a central arterial pathway (carotid-femoral) and in a peripheral pathway (carotid-brachial). A blood pressure-independent regional arterial stiffness index was calculated using PWV. Volume status was assessed by whole-body multiple-frequency bioimpedance. Patients were first observed as an entire group and then divided into three different fluid status-related groups: normal, overhydration, and dehydration groups. Results. Only carotid-femoral stiffness was positively associated (P < 0.05) with the hydration status evaluated through extracellular/intracellular fluid, extracellular/Total Body Fluid, and absolute and relative overhydration. Conclusion. Volume status and overload are associated with central, but not peripheral, arterial stiffness levels with independence of the blood pressure level, in CHP.

Velocidad de la onda de pulso: relevancia de la edad en normotensión, hipertensión esencial e hipertensión limítrofe / Pulse Wave Velocity: Relevance of Age in Normotensive, Essential Hypertensive and Borderline Hypertensive Patients

Introducción: Se han descripto varios parámetros de medición del estado de la función arterial y, de ellos, la velocidad de la onda de pulso (VOP) es el único que permite una medición directa de la rigidez arterial. A medida que aumenta la edad del individuo se va produciendo una pérdida de la capacidad elástica, conocida como envejecimiento vascular, proceso este que estaría acelerado en los pacientes con hipertensión arterial. Objetivos: Normalizar por décadas los valores de la VOP en pacientes normotensos (NT), hipertensos esenciales (HT) e hipertensos limítrofes (LT) y diferenciar los efectos del envejecimiento sobre la VOP de los vinculados a la hipertensión arterial. Material y métodos: Se estudiaron 221 pacientes consecutivos, de ambos sexos, que fueron clasificados, por sus valores de presión arterial (PA), en tres grupos: NT (n = 120, 46 ± 13 años): PA < 135/85 mm Hg; HT (n = 60, 50 ± 13 años): PA > 140/90 mm Hg; y LT (n = 41, 47 ± 12 años): PA = 135-139/85-89 mm Hg. Posteriormente fueron divididos en cuatro grupos por edades: GI ≤ 39 años, GII = 40-49 años, GIII = 50-59 años y GIV > 60 años. La VOP se midió con transductores mecanográficos y cálculo computarizado. Se utilizaron las pruebas de ANOVA, de Newman-Keuls y de regresión lineal multivariada. Resultados: La VOP aumentó significativamente (p < 0,05) con la edad en todos los grupos etarios (m/seg): GI: NT (n = 42): 8,6 ± 1,1, HT (n = 16): 9,5 ± 1,3, LT (n = 10): 9,0 ± 0,5; GII: NT (n = 24): 9,5 ± 1,2, HT (n = 16): 10,7 ± 1,2, LT (n = 14): 9,8 ± 0,8; GIII: NT (n = 30): 10,3 ± 1,5, HT (n = 12): 12,1 ± 1,5, LT (n = 11): 11,0 ± 1,3; y GIV: NT (n = 24): 11,4 ± 1,8, HT (n = 16): 14,1 ± 2,4, LT (n = 6): 13,3 ± 1,1. Las ecuaciones de regresión halladas fueron: en NT, VOP = 0,08 × edad + 0,04 × presión arterial sistólica (PAS) + 1,07 (r = 0,71); en HT, VOP = 0,12 × edad + 0,06 × PAS - 2,51 (r = 0,81); y en LT, VOP = 0,10 × edad + 0,02 × PAS + 0,02 (r = 0,73) (p < 0,05). Conclusiones: La VOP aumentó con la edad, siendo el incremento mayor en HT para cada grupo etario. Los sujetos LT tuvieron valores intermedios entre los otros dos grupos. Ello sugiere un deterioro de la función arterial adicional inducido por la hipertensión arterial sobre el envejecimiento. Este efecto adicional puede estimarse con la ecuación de regresión obtenida para cada grupo.

Background: Among the various parameters used to describe arterial function, pulse wave velocity (PWV) is the only one allowing direct measurement of arterial stiffness. Loss of arterial elastic capacity with increasing age, a process known as vascular aging, is enhanced in hypertensive patients. Objectives: The aim of this study was to normalize PWV in normotensive (NT), essential hypertensive (HT) and borderline hypertensive (BL) patients and differentiate the effects of aging on PWV from those associated to hypertension. Methods: A total of 221 consecutive male and female patients were included in the study. They were classified into three groups according to their blood pressure (BP) values: NT (n=120, 46±13 years): BP<135/85 mmHg; HT (n=60, 50±13 years): BP>140/90 mmHg; and BL (n=41, 47±12 years): BP=135-139/85-89 mmHg. They were then stratified into four groups according to age: GI≤39 years, GII=40-49 years, GIII=50-60 years and GIV>60 years. Mechanographic transducers and computerized calculation were used to measure PWV. Data analysis was performed using ANOVA, Newman-Keuls, and multivariate linear regression tests. Results: Pulse wave velocity increased with age in all age groups (p<0.05). Mean PWV (m/s) in G1 was: NT (n=42): 8.6±1.1, HT (n=16): 9.5±1.3, BL (n=10): 9.0±0.5; in GII: NT (n=24): 9.5±1.2, HT (n=16): 10.7±1.2, BL (n=14): 9.8±0.8; in GIII: NT (n=30): 10.3±1.5, HT (n=12): 12.1±1.5, BL (n=11): 11.0±1.3; and in GIV: NT (n=24): 11.4±1.8, HT (n=16): 14.1±2.4, BL (n=6): 13.3±1.1. Regression equations were: for NT, PWV=0.08 × age+0.04 × systolic blood pressure (SBP)+1.07 (r=0.71); for HT, PWV=0.12 × age+0.06 × SBP-2.51 (r=0.81); and for BL, PWV=0.10 × age+0.02 × SBP+0.02 (r=0.73) (p<0.05). Conclusions: Pulse wave velocity increased with age, and was higher in HT patients for each age group. Borderline hypertensive patients presented intermediate values between the other two groups. These results suggest additional vascular impairment induced by hypertension over that of aging. This surplus effect could be estimated from the regression equation obtained for each group.

Hemodialysis decreases carotid-brachial and carotid-femoral pulse wave velocities: A 5-year follow-up study.

Aortic stiffness is a prognostic parameter associated with patient mortality. Vascular access creation has been shown to have effects on arterial stiffness both in the aorta and in the upper limb arteries in chronically hemodialyzed patients (CHPs). However, no longitudinal studies have been conducted in order to characterize the evolution of arterial stiffness in CHPs. The aims of this work were (a) to measure baseline pulse wave velocity (PWV) in the carotid-femoral and in right and left carotid-brachial pathways in a cohort of CHP and (b) to conduct a 5-year prospective study on the same cohort to determine possible time-related differences. Pulse wave velocity was measured both in the carotid-femoral and in the carotid-brachial pathways, and clinical and biochemical parameters were collected in 25 CHPs, which were followed up after a 5-year lapse. Right and left carotid-brachial pathway PWV values showed significant decreases after the 5-year follow-up, independently of the presence of the vascular access (P < 0.001). Additionally, baseline carotid-brachial PWV was significantly higher (P < 0.001) than values measured 5 years later for upper limbs with vascular access (11.97 ± 2.97 m/sec vs. 6.76 ± 1.48 m/sec, respectively) and without vascular access (12.25 ± 2.38 m/sec vs. 7.18 ± 1.88 m/sec, respectively). Similarly, PWV values in the carotid-femoral pathway decreased significantly (P < 0.001) over the same period (13.27 ± 2.96 m/sec vs. 9.75 ± 2.99 m/sec, respectively). The 5-year follow-up of PWV showed significant decreases in both carotid-brachial and carotid-femoral pathways. The general changes in arterial stiffness could be related to the vascular access creation, hemodialysis therapy, and to the improvement of arterial pressure management.

High pressure assessment of bilayered electrospun vascular grafts by means of an Electroforce Biodynamic System®.

INTRODUCTION: Tissue engineering offers the possibility of developing a biological substitute material in vitro with the inherent properties required in vivo. However, the inadequate performance in vascular replacement of small diameter vascular grafts (VG) reduces considerably the current alternatives in this field. In this study, a bilayered tubular VG was produced, where its mechanical response was tested at high pressure ranges and compared to a native femoral artery. MATERIALS AND METHOD: The VG was obtained using sequential electrospinning technique, by means of two blends of Poly(L-lactic acid) and segmented poly(ester urethane). Mechanical testing was performed in a biodynamic system and the pressure-strain relationship was used to determine the elastic modulus. RESULTS: Elastic modulus assessed value of femoral artery at a high pressure range (33.02×106 dyn/cm(2)) was founded to be 36% the magnitude of VG modulus (91.47×106 dyn/cm(2)) at the same interval. CONCLUSION: A new circulating mock in combination with scan laser micrometry have been employed for the mechanical evaluation of bioresorbable bilayered VGs. At same pressure levels, graft elasticity showed a purely "collagenic" behavior with respect to a femoral artery response.

A proposal to enhance Engineering education in biology and Medicine by following the legacy of René Favaloro.

The synergy amongst Engineering, Medicine and Biology evolves as fast as these disciplines. We propose to articulate these specialties based on the premise that new professionals must face different situations or crisis due to the so-called islands of excellence. René Favaloro focused his work and struggles against poverty, since malnutrition and environmental degradation may increase the propensity to cardiovascular diseases. Doctor Favaloro has dedicated, throughout his career, a considerable amount of time to prepare and qualify a research group, aware of the importance that an adequate working environment has over the final results. He created a team of young students, engineers, medical doctors, physicists, mathematicians and other specialists. He centered his attention on human resources, in order to disseminate his latest advances in Biology, Medicine and Engineering. We are revising the programs of biomedical engineering education and the application of new pedagogic paradigms, where critical thinking is the key: a holistic challenge that consists of a new way of learning, innovating, communicating and shearing, with a creative attitude that represents quality of perception.

Composición y biomecánica de placas de ateroma carotídeas / Composition and biomechanics of carotid atheroma plaques

Introducción: la enfermedad aterosclerótica y sus complicaciones constituyen la causa más frecuente de muerte en el mundo. Un análisis de la relación entre parámetros estructurales y mecánicos de las placas de ateroma carotídea (PAC) es mandatorio a la hora de aumentar nuestros conocimientos en torno a los mecanismos que favorecerían la fatiga mecánica del material de la placa y su complicación. Objetivos: analizar la distensibilidad carotídea en sujetos sanos y con PAC según su composición estructural. Métodos: se estudiaron 100 sujetos asintomáticos con PAC (n=36) y sin PAC (n=64). Se clasificaron las PAC según la mediana de niveles de grises y mapeo por color en lipídicas (L), fibrolipídicas (FL) y fibrosas/calcificadas (FC). Se combinó ultrasonido modo-B con tonometría de aplanamiento y se cuantificó la distensibilidad a lo largo del eje longitudinal en cinco sectores a nivel de la PAC y de la arteria carótida normal. Resultados: se clasificaron 71 PAC (35 L, 16 FL y 20 FC), todas se encontraron en segmentos arteriales con menores niveles de distensibilidad comparado con las arterias sanas. Las PAC FC mostraron mayor rigidez a nivel del hombro proximal en comparación con las L y FL que se comportan de manera más homogénea en todos sus sectores. Conclusión: las PAC L y FL (consideradas de mayor riesgo) no presentaron el cambio significativo de rigidez parietal observado en las PAC FC, consideradas de menor riesgo de complicación. Estas diferencias biomecánicas relacionadas con la composición global de la PAC podrían tener una implicancia en la patogenia de la complicación de placa.

Introduction: the aterosclerotic disease and its complications are the most frequent cause of death in the world. An analysis of the relationship between structural and mechanic parameters of the carotid aterome plaque (CAP) is mandatory in the need of improving our knowledge concerning the mechanisms that would favor the mechanic fatigue of the plaque material and its complication. Objectives: analize the carotid distensibility in healthy persons and with patients with CAP according to their structural composition. Methods: 100 asymptomatic individuals were studied, with CAP (n=36) and without CAP (n=64). CAP persons were classified according to the standard levels of greys and color mapping in lipidic (L), fibrolipidic (FL) and fibrous/calcified (FC). B-mode Ultrasound with applanation tonometry were combined and the distensibility was quantified along the longitudinal axis in five sectors to the level of the CAP and in the normal carotid artery. Results: 71 CAP (35 L, 16 FL y 20 FC) were classified all in low-level distensibility arterial segments compared to healthy arteries. The FC CAP showed more rigidity in the proximal shoulder compared to the L and FL that behave more homogeneously in all their sectors. Conclusion: the L and FL CAPs (considered of major risk) did not present the parietal rigidity significant change observed in the FC CAP, considered of low complication risk. These biomechanic differences related to the global composition of the CAP could have an implication in the pathogenesis of the plaque complication.

Similarities of arterial collagen pressure-diameter relationship in ovine femoral arteries and PLLA vascular grafts.

INTRODUCTION: In-vivo implanted vascular grafts fail due to the mechanical mismatch between the native vessel and the implant. The biomechanical characterization of native vessels provides valuable information towards the development of synthetic grafts. MATERIALS AND METHODS: Five samples of electrospun nanofibrous poly(L-lactic acid)(PLLA) tubular structures were subjected to physiological pulsating pressure using an experimental setup. Four ovine femoral arteries were also tested in the experimental setup under the same conditions. Instantaneous diameter and pressure signals were obtained using gold standard techniques, in order to estimate the dynamic pressure-strain elastic modulus (E(Pε)) of both native vessels and grafts. RESULTS: Synthetic grafts showed a significant increase of E(Pε) (10.57±0.97 to 17.63±2.61 10(6) dyn/cm(2)) when pressure was increased from a range of 50-90 mmHg (elastin-response range) to a range of 100-130 mmHg (collagen-response range). Furthermore, femoral arteries also exhibited a significant increase of EPε (1.66±0.30 to 15.76±4.78 10(6) dyn/cm(2)) with the same pressure variation, showing that both native vessels and synthetic grafts have a similar behavior in the collagen-acting range. CONCLUSION: The mechanical behavior of PLLA vascular grafts was characterized In vitro. However, the procedure can be easily extrapolated to In vivo experiences in conscious and chronically instrumented animals.