Arterial Network Research Articles

Anatomical study of the pial arterial network in human spinal cords.

Multiple collaterals originate from three main longitudinal vessels to perfuse the human spinal cord. Only a few classic studies published in the last century have investigated these collaterals. The current work proposes a possible classification of these vessels and analyzes their relative abundance along spinal cord segments. Human spinal cords (n = 30) from male and female cadavers were injected with colored latex through the vertebral, ascending cervical, costocervical trunk and segmental arteries and then fixed in formaldehyde solution. Afterwards, spinal vessels were dissected and the relative abundances of each type of collateral were quantified and compared between different spinal cord segments. Collaterals of the anterior longitudinal pathway can be classified as central arteries and arteries for the anterior and lateral columns. Collaterals for the anterior column can be classified into two types: anteromedial and anterolateral. Arteries for the lateral column can be classified, according to their relationship with the dentate ligament, as either preligamentous or post-ligamentous. The collaterals of posterior longitudinal pathways can be divided between those for the posterior and those for the lateral column. In turn, the arteries for the posterior column can be classified into three types: median posterior, posteromedial and posterolateral. The collaterals for the lateral column were also classified as either pre- or post-ligamentous. The relative abundance of the various types of collateral and anastomoses between longitudinal pathways was inhomogeneous along the spinal cord, with several statistically significant differences observed between spinal segments.

Vascular Casting of Adult and Early Postnatal Mouse Lungs for Micro-CT Imaging.

Blood vessels form intricate networks in 3-dimensional space. Consequently, it is difficult to visually appreciate how vascular networks interact and behave by observing the surface of a tissue. This method provides a means to visualize the complex 3-dimensional vascular architecture of the lung. To accomplish this, a catheter is inserted into the pulmonary artery and the vasculature is simultaneously flushed of blood and chemically dilated to limit resistance. Lungs are then inflated through the trachea at a standard pressure and the polymer compound is infused into the vascular bed at a standard flow rate. Once the entire arterial network is filled and allowed to cure, the lung vasculature may be visualized directly or imaged on a micro-CT (µCT) scanner. When performed successfully, one can appreciate the pulmonary arterial network in mice ranging from early postnatal ages to adults. Additionally, while demonstrated in the pulmonary arterial bed, this method can be applied to any vascular bed with optimized catheter placement and endpoints.

Consideration of Pannexin 1 channels in COVID-19 pathology and treatment.

Pannexin1 (PANX1) is a ubiquitously expressed, channel-forming protein found in a number of tissues thoughout the body (e.g. lung, vasculature, liver, central nervous system, immune system) that is important in many key physiological and immune responses. PANX1 channels passively flux ATP (predominantly), multiple metabolites, and likely other small anions. PANX1 channels regulate inflammation and host responses to several pathogens, including viruses. While there is currently no evidence suggesting novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and PANX1 directly interact, there is an urgent need for therapeutic strategies, especially those targeting the hyper-inflammation and cytokine storm that occurs in severe cases of COVID-19. Here we argue that PANX1, and drugs known to target PANX1 (including the FDA-approved drug probenecid), should be the focus of further investigation in the context of SARS-CoV-2 infection and its associated pathology in COVID-19 patients.

Papillary Trunk Bifurcation Angles as Major Determinants of Ocular Perfusion: A Cross-Sectional Study

Background: Notable work has been done by Cecile and Murray in as early as 1926, on the structural and topological aspects of vasculature based on the concept that blood vessel size and arrangement is such that it provides blood flow with minimum energy loss. In the theoretical analysis of arterial networks, the existence of geometric optimisation for enabling functional adequacy has long been suggested, but observational studies have not yet fully corroborated these theories. Data on branching or bifurcation angles of retinal microvasculature is not only insufficient but also inconclusive. Aim: Attending to this gap in information, we compared the central retinal artery (CRA) branching angles of known diabetics with healthy subjects and explored their possible role in determining the circulatory adequacy of human retina. Methods: This study was done on North Indian subjects attending retina clinics of prominent tertiary centers of north India during 2019 through 2020. Fundus images were acquired through convenience sampling from 860 consecutive eyes of 430 subjects. Fluorescein fundus angiography was followed up for diabetics. CRA branching angles from digitalized fundus photographs of known diabetics and healthy subjects was analyzed through semi-automated digital image management tool and the readings were clinically correlated to note the occurrence and severity of retinopathic perfusion defects was Results: We found marked differences between CRA branching angles among diabetics and healthy subjects and a significant correlation between branching anless and the occurrence and severity of retinopathic perfusion defects. Discussion and Conclusion: The orientation of retinal blood vessels on the fundus plane is not merely ‘a matter of chance’ in the anatomic chronicle of the human body; rather, it has biological heralds and functional consequences. Direction, branching, angles; all determine the efficacy and abundance of blood flow in the human retina that hold indispensible relevance for optimal vision and might be subtle indicators of micro vascular damage in disease states. This study has elucidated retinal vascular geometrics of healthy and diseased Indians, a knowledge that can improve our understanding of ‘abnormal features’ and ‘natural variants’ in retinal vascular architecture. In this study, we quantified the ‘structural factors’ behind perfusion defects of the Diabetic retina.

Vulnerability Assessment of Urban Intersections apropos of Incident Impact on Road Network and Identification of Critical Intersections

One of the major challenges in a transportation network management program is responding to traffic incidents such as traffic crashes, disabled vehicles, spilled cargo, road debris, and so forth, at or near intersections. Intersections are vulnerable with respect to their susceptibility to incidents, therefore, it is important to assess their vulnerability to identify critical intersections for preparing traffic incident management strategies. In the present work, vulnerability of an intersection was measured in relation to the incident impact on surrounding road network using average aggregate network delay. Taking the case study of an urban arterial road network in Kolkata city, a methodology was demonstrated to assess the vulnerability of intersections using traffic microsimulation during peak and off-peak periods. A traffic microsimulation model was developed for this purpose and different incident scenarios were simulated to assess the vulnerability of various intersections. The intersections were then ranked in order of their vulnerability. Some key factors governing vulnerability of intersections were identified and an expert opinion survey was also conducted to assess the location-specific relevance of those factors for both peak and off-peak hour conditions using fuzzy analysis. Based on the analysis of expert opinion data, intersections were also ranked as per their vulnerability for comparative purposes. The rankings of intersections as obtained from traffic microsimulation and expert opinion analyses were found to be in agreement in the present context. However, traffic microsimulation as an approach is preferred over expert opinion because of its inherent strengths for vulnerability assessment and identification of critical intersections.

Visualization techniques of the facial arteries.

BackgroundAs the face is known for its extreme variation in vascular anatomy and the number of filler‐associated complications due to intra‐arterial injection is increasing, we are in need of a method to visualize anyone’s individual arterial anatomy of the face in a completely harmless way.AimsThe different medical imaging methods and a recently developed MRA protocol are reviewed.MethodsThe literature of the last twenty years—with special attention for the last five years—concerning the different medical imaging modalities of the facial arteries was reviewed.ResultsA harmless visualisation of the facial arteries is currently only possible with US or MRA. US may identify single vessels but never the complete arterial network. A combination of IR “heat enhancement” and a MRA 3D‐TOF sequence might make it feasible to visualize a large number of facial arteries in a risk‐free, radiation‐free, contrast‐free and non‐invasive way.ConclusionCurrently, a new combination of IR “heat enhancement” and a MRA 3D‐TOF sequence might be the only method to visualize a large number of facial arteries.

INPUT IMPEDANCE OF AN ARTERIAL TREE MODEL

Computational models are used to represent blood flow in large and small arteries and to simulate cardiovascular diseases. Through these models, it is possible to estimate the pressure and blood flow in arterial vessels. However, to reduce the complexity of the model simulation, it is necessary to truncate small arterial domains representing the networks of small arteries and arterioles. At truncation points, the input impedance is used as a boundary condition. This work describes a method based on fractal laws to generate models of arterial trees that represent the truncated arterial districts, and how to calculate the input impedance of these models. The influence of the parameters used in the generation of the arterial tree model on the input impedance is investigated. The results show that the bifurcation exponent and asymmetry ratio most influence the input impedance response of the models.

4D Flat Panel Conebeam CTA for In Vivo Imaging of the Microvasculature of the Human Cortex with a Novel Software Prototype.

It was the aim of our pilot study to investigate whether time-resolved flat panel conebeam CTA is able to demonstrate small cortical vessels in vivo. In 8 patients with small AVMs, time-resolved coronal MPRs of the vasculature of the frontal cortex were recalculated from 3D rotational angiography datasets with the use of a novel software prototype. 4D flat panel conebeam CTA demonstrated the course of the cortical arteries with small perpendicular side branches to the underlying cortex. Pial arterial and venous networks could also be identified, corresponding to findings in injection specimens. Reasonable image quality was achieved in 6 of 8 cases. In this small study, in vivo display of the cortical microvasculature with 4D flat panel conebeam CTA was feasible and superior to other angiographic imaging modalities.

Identification and quantitative analysis of branching networks of the posterior intercostal arteries.

Morphological and anatomical characteristics of the posterior intercostal arteries have revived interest in their branching networks. Collateral supply between intercostal spaces is extensive due to anastomoses, although the data about the quantitative description of the branching networks in the existing literature are rather limited. The presence of collateral network between branches of the posterior intercostal arteries has been studied on forty-three Thiel-embalmed human cadavers. A network-based approach has been used to quantify the measured vascular branching patterns. Connections between branches of the same or adjacent posterior intercostal artery were identified. The non-anastomosing branches coursing in the intercostal spaces were also observed and their abundance was higher in comparison to anastomosing vessels. A quantitative analysis of collateral branching networks has revealed the highest density of vessels located close to the costal angle and most of the anastomosing branches were found between the fourth and tenth intercostal space. Anastomoses within the same posterior intercostal artery were more frequent in higher intercostal spaces, whereas in the lower intercostal spaces more connections were established between neighboring intercostal arteries. Our results indicate that due to abundant collateral contribution the possibility to cause an ischemic injury is rather low unless there is considerable damage to the blood supply of the trunk or surgical complication leading to ischemia or necrosis. Analyzing the proper course of collateral contributions of the posterior intercostal arteries may support further directions regarding the safest place for percutaneous transthoracic interventions, thoracocentesis, and lung biopsy.

Artériopathie oblitérante des membres inférieurs

Peripheral arterial disease is a result of atheroma. This disease is frequent in subjects with vascular risk factors. This disease is also frequent in low income countries. The detection and the diagnosis of peripheral arterial disease is obtained by calculating the ankle brachial index. Patients with peripheral arterial disease are not always symptomatic thus explaining how this disease is under diagnosed. The symptoms can be absent, and especially in case of diabetes or in women. In case of peripheral arterial disease, atheroma often involves other arterial vascular networks especially the coronaries. An adapted treatment reduces the morbi-mortality linked to this disease. This treatment is based on the correction of the vascular risk factors and especially tobacco cessation, walking rehabilitation and drugs (antiplatelet agent, statin, renin angiotensin system blocker). In case of rest or critic ischemia, the first-line treatment is a revascularisation. In peripheral arterial disease, management of patients is often non optimal and therapeutic targets fairly often obtained.

Development and Testing of a Novel Game Theoretic De-Centralized Traffic Signal Controller

The paper presents a novel de-centralized traffic signal controller, achieved using a Nash bargaining game-theoretic framework, that operates a flexible phasing sequence to adapt to dynamic changes in traffic demand levels. The Nash bargaining algorithm is used to optimize the traffic signal timings at each signalized intersection by modeling each phase as a player in a game, where players cooperate to reach a mutually agreeable outcome. The algorithm was implemented in the INTEGRATION microscopic traffic assignment and simulation software and tested on two sample networks. The proposed control approach was compared to the operation of an optimum fixed-time coordinated plan, an actuated controller, a centralized adaptive phase split controller, a decentralized phase split and cycle length controller, and a fully coordinated adaptive phase split, cycle length, and offset optimization controller to evaluate its performance. Testing was initially conducted on an isolated intersection, showing a 77% reduction in queue length, a a 64% reduction in vehicle delay, and a 17% reduction in vehicle emission levels. In addition, the algorithm was tested on an arterial network producing statistically significant reductions in total delay ranging between 36% and 67% and vehicle emission reductions ranging between 6% and 13%.

Walled vessel-mimicking phantom for ultrasound imaging using 3D printing with a water-soluble filament: design principle, fluid-structure interaction (FSI) simulation, and experimental validation

The geometry and stiffness of a vessel are pertinent to blood dynamics and vessel wall mechanical behavior and may alter in diseased conditions. Ultrasound-based ultrafast Doppler (uDoppler) imaging and shear wave imaging (SWI) techniques have been extensively exploited for the assessment of vascular hemodynamics and mechanics. Their performance is conventionally validated on vessel-mimicking phantoms (VMPs) prior to their clinical use. Compared with commercial ones, customized VMPs are favored for research use because of their wider range of material properties, more complex lumen geometries, or wall structures. Fused deposition modeling (FDM) 3D printing technique with plastic filaments is a promising method for making VMPs with a complex vessel lumen. However, it may require a toxic solvent or a long dissolution time currently. In this paper, we present a safe, efficient and geometrically flexible method where FDM 3D printing with a water-soluble polyvinyl alcohol (PVA) filament is exploited to fabricate a walled three-branch VMP (VMP-I). As a key step in fabrication, to avoid dissolution of the PVA-printed vessel core by the solution of the tissue-mimicking material, paraffin wax was used for isolation. Paraffin wax is easy to coat (i.e. without any special equipment), of satisfactory thickness (∼0.1 mm), chemically stable, and easy to remove after fabrication, thus making the proposed method practicable for ultrasound imaging studies. VMP-I was examined by B-mode imaging and power Doppler imaging (PDI) to verify complete dissolution of PVA-printed vessel core in its lumen, confirming good fabrication quality. The flow velocities in VMP-I were estimated by uDoppler imaging with a −0.8% difference, and the shear wave propagation speeds for the same phantom were estimated by SWI with a −6.03% difference when compared with fluid-structure interaction (FSI) simulation results. A wall-less VMP of a scaled and simplified coronary arterial network (VMP-II) was additionally fabricated and examined to test the capability of the proposed method for a complex lumen geometry. The proposed fabrication method for customized VMPs is foreseen to facilitate the development of ultrasound imaging techniques for blood vessels.

Bone blood flow regulation in humans

Bone is a highly vascularized organ with an extensive network of arteries, arterioles, and capillaries that is critical for bone development, maintenance, and repair. Despite the importance of bone circulation to bone health, the regulation of blood flow to bone is not well understood in humans. One of the potential factors controlling bone blood flow is the sympathetic nervous system, bone vasculature being innervated by a rich network of sympathetic nerves. While no human studies have been conducted, animal data suggests that sympathetic activation reduces bone blood flow. If this were not the case, bone vasculature would respond simply as a passive pressure system. Therefore, we characterized bone blood flow regulation in health young individuals (N=12 (8M; 4F), 23±0.7 years) in response to isometric handgrip to fatigue (IHE). Sustained IHE is a profound pressor stimulus, resulting in active vasoconstriction in the nonactive leg and progressive increases in blood pressure. During IHE at 30% of maximal voluntary contraction, we measured blood pressure, whole leg blood flow (via Doppler ultrasound), and tibial blood perfusion (via near infrared spectroscopy). Tibial blood perfusion was determined as changes from resting baseline in oxygenated and deoxygenated hemoglobin content. Data is presented as mean change from resting baseline ± standard error. To account for different IHE time courses, all variables were normalized to 100% duration and averaged across individuals. Blood pressure increased progressively to end of IHE (at 10%: 5.46 ± 1.30 mmHg; at 100%: 48.0 ± 4.32 mmHg). Whole leg blood flow decreased progressively throughout IHE, suggesting active sympathetic vasoconstriction in the leg (at 10%: −0.70 ± 0.28 cm/s; at 100%: −2.26 ± 0.50 cm/s). Similarly, tibial oxygenated hemoglobin decreased progressively throughout the test (at 10%: −0.21 ± 0.31 μM; at 100%: −1.19 ± 1.12 μM) whereas tibial deoxygenated hemoglobin did not change significantly throughout IHE (at 10%: 0.06 ± 0.07 μM; at 100%: −0.4 ± 0.32 μM). This indicates that arterial flow (oxygenated hemoglobin) declined while bone metabolism (deoxygenated hemoglobin) remained unchanged in response to IHE. It should be noted that the decline in oxygenated hemoglobin was slower and lesser than that in whole leg blood flow. This data suggests that sympathetic activity is involved in controlling bone circulation, but vasoconstrictor responses is not as fast or as robust in bone as it is in the whole leg.Support or Funding InformationParalyzed Veterans of America (AED)

Morphological remodeling of the intramural coronary resistance artery network geometry in chronically Angiotensin II infused hypertensive female rats

Segmental remodeling of resistance arteries, inhibition of angiogenetic processes, their rarefaction by AngiotensinII and hypertension are accepted facts. Less is known about alterations in resistance artery network geometry potentially induced by them. Female rats were infused with 100 ng/kg/min AngiotensinII with osmotic minipumps for four weeks that raised mean arterial blood pressure from 98 ± 3 to 125 ± 7 mmHg. Geometry of the left coronary artery system was studied on plastic casts and on in situ microsurgically prepared, saline infused video-microscoped networks (n = 13 and 11 controls and hypertensives, respectively). Parallel running branches, broken course of larger branches, multiple branchings and branch crossings have been identified (13 and 74 such deformities, in control and hypertensive networks, respectively, p < 0.01). Bifurcation angles increased with increasing asymmetry of daughter branches but not in hypertensives. Dividing the whole network (theoretically) into several hundreds of 50μm long ring units, ring frequency peaked at 200μm diameter in normal networks. This peak diminished and was replaced by a peak at 300μm in hypertensives (p < 0.01). In controls, diameter of vascular units decreased at a fairly even rate with flow distance from the orifice. The 350, 200, 150μm diameter units were found with highest frequencies at flow distances around 2.5, 5.5 and 7.5mm, respectively. This regular pattern disintegrated in hypertensives. Higher blood flow routes were needed to cover the same distance from the orifice (p < 0.01). Shrinkage and diminishment of many parallel connected 200μm segments, concomitant enlargement of many larger segments accompanied with morphological deformities can be expected to contribute to elevated vascular resistance.

Paediatric haemodynamic modelling: development and experimental validation using quantitative flow MRI

BackgroundCongenital vascular disease is one of the leading causes of death in paediatric age. Despite the importance of paediatric haemodynamics, large investigations have been devoted to the evaluation of circulation in adults. The novelty of this study consists in the development of a well calibrated mathematical model of cardiovascular circulation in paediatric subjects. To reach the purpose, a model for adult circulation was modified and recalibrated with experimental data and literature from children to be able to calculate the flow rates and pressures in the brain and neck.MethodsThe haemodynamic model simulates the 76 main arteries, together with the main veins in brain and neck. A proper magnetic resonance imaging (MRI) dataset of 29 volunteers aged 12 ± 5 years (mean ± standard deviation) was used to extract age-dependent physiological and clinical parameters such as heart rate, flow rate, vessel cross section area, and blood pressure. The computational model was calibrated using such experimental data. The paediatric and adult model results were compared.ResultsIncrease of the vessels stiffness due to aging contributes to a flow rate decrease while blood pressure increases. In accordance, our simulation results show about 16% decrease in mean pressure of internal jugular vein in paediatric rather than adult subjects. The model outcomes indicated about 88% correlation with MRI data.ConclusionsThe mathematical model simulates the paediatric head and neck blood circulation. The model provides detailed information of human haemodynamics including arterial and venous network to study both paediatric and adult blood circulation.

Augmented patient‐specific functional medical imaging by implicit manifold learning

This paper uses machine learning to enrich magnetic resonance angiography and magnetic resonance imaging acquisitions. A convolutional neural network is built and trained over a synthetic database linking geometrical parameters and mechanical characteristics of the arteries to blood flow rates and pressures in an arterial network. Once properly trained, the resulting neural network can be used in order to predict blood pressure in cerebral arteries noninvasively in nearly real-time. One challenge here is that not all input variables present in the synthetic database are known from patient-specific medical data. To overcome this challenge, a learning technique, which we refer to as implicit manifold learning, is employed: in this view, the input and output data of the neural network are selected based on their availability from medical measurements rather than being defined from the mechanical description of the arterial system. The results show the potential of the method and that machine learning is an alternative to costly ensemble based inversion involving sophisticated fluid structure models.

Exploring the Effects of the Built Environment on Two Transfer Modes for Metros: Dockless Bike Sharing and Taxis

The success of metro systems depends on effective multimodal solutions that bridge the first-and-last-mile gaps. Both dockless bike sharing (DBS) and taxis are important feeder modes for metros, which provide on-demand travel options with high flexibility and accessibility. Based on one-week trip data of DBS and taxis during a concurrent period in Beijing, China, the paper aims to compare the temporal-spatial distribution of two modes as first-and-last-mile connectors and find out the socio-demographic and built-environment factors that impact their usage. K-means clustering is implemented to visualize the spatial distribution of DBS and taxis around metro stations, and the spatial lag model incorporating spatial autocorrelations of variables is developed. The results show that people prefer to use DBS as a substitutable mode for bus services to serve first-mile interchange in the morning. Also, less economically developed areas with a high density of branches and fewer signalized intersections are more favored by DBS users, whereas people in the central areas with high housing price and developed arterial road network tend to take a taxi, especially during evening peak period. The study can offer the policy guidance to improve DBS services, and several recommendations are suggested to ensure the sustainable development of DBS.

Artificial intelligence based commuter behaviour profiling framework using Internet of things for real-time decision-making

Road traffic environments are highly dynamic and volatile with a multitude of roadside and external environmental factors contributing to its dynamicity. Apart from infrastructure-related means such as traffic lights, planned and unplanned road events and different road networks, a core component which contributes towards the traffic environment is the human factor which is heavily overlooked in the current studies. Due to diverse travel patterns of day-to-day activities, the commuter behaviour is directly depicted in traffic patterns providing an opportunity to further explore human behaviours using road traffic. Conducting such analysis would reveal different commuter behavioural patterns that can be used for optimization and timely management of operations. However, to conduct such real-time behaviour analysis, large volumes of high-frequency data are required with high granularity, as well as, a suitable technology to manage such data. Addressing these needs, we propose an environment-driven commuter behavioural model that can be used to elucidate diverse behaviours in road traffic environments. We conceptualized, designed and developed an artificial intelligence based commuter behaviour profiling framework to detect diverse commuter behavioural profiles, fluctuating and routine patterns among commuters using traffic flow profiling and travel trajectory analysis. We evaluated the framework using 190 million data points captured from the Bluetooth sensor network of the Melbourne arterial road network, in the state of Victoria in Australia. The results demonstrate that traffic flow profiling of the proposed framework can provide insights on recurrent commuter behaviours that are distinct to a selected area with a high granularity. Moreover, traffic trajectory analysis provides insights on non-recurrent behaviours such as accidents with regard to how such incidents impact the dynamics of the network and how the impact is propagated through the network. Besides road traffic management, the proposed framework will enable real-time decision-making when planning road infrastructure and support decision-making of government and business entities to optimize operations.

Anterior Communicating Artery Complex Aneurysms Are Caused by the Asymmetric Anterior Cerebral Arteries

Background: Rupture of anterior communicating artery complex (AcomAC) aneurysms is a common cause of haemorrhagic brain strokes. Ability to predict development of aneurysms in advance would allow stroke prevention. Asymmetry of the components of cerebral basal arterial network (CBAN) could alter hemodynamics and may contribute to formation of aneurysms. The asymmetric diameter ratio of first segments of anterior cerebral arteries (A1s), correlates with the occurrence of the AcomAC aneurysms. Materials and Methods: Cerebral Computed Tomography Angiography (CTA) scans of 166 adult patients of both sexes were studied. The internal diameters of the right and left A1 segments of anterior cerebral arteries, perpendicular to the long axis of the vessels were measured. Positions and presence or absence of aneurysms in AcomAC were recorded in each individual case. The ratio of the larger to the smaller A1 diameters was determined as a measure of the asymmetry of A1 segments of anterior cerebral arteries (ACAs). Findings: The risk of development of aneurysms in AcomAC was much greater (risk 80%, odds ratio = 47·3) when one A1 segment's radius was at least 50% larger (i.e. 2·25 times greater cross-sectional area) than the other. The risk of development of aneurysms was just 7·8%, if the A1 asymmetric ratio was less than 1·5 (odds ratio = 0·02). Conclusion: The asymmetry ratio of the A1 segments of anterior cerebral arteries is a good predictor for the development of aneurysms in the AcomAC region. Funding Statement: The authors stated: None. Declaration of Interests: The authors declare that there is no conflict of interests. Ethics Approval Statement: The use of images and accompanying information was approved for research purposes by the University of Adelaide Human Research Ethics Board (approval number: H2014-176). Patients’ personal details, have not been copied, documented, or included in this research.

Arterial Stiffness in Hypertension and Function of Large Arteries.

Arterial stiffness-typically assessed from non-invasive measurement of pulse wave velocity along a straight portion of the vascular tree between the right common carotid and femoral arteries-is a reliable predictor of cardiovascular risk in patients with essential hypertension. We reviewed how carotid-femoral pulse wave velocity increases with age and is significantly higher in hypertension (than in age- and gender-matched individuals without hypertension), particularly when hypertension is associated with diabetes mellitus. From the elastic aorta to the muscular peripheral arteries of young healthy individuals, there is a gradual but significant increase in stiffness, with a specific gradient. This moderates the transmission of pulsatile pressure towards the periphery, thus protecting the microcirculatory network. The heterogeneity of stiffness between the elastic and muscular arteries causes the gradient to disappear or be inversed with aging, particularly in long-standing hypertension. In hypertension therefore, pulsatile pressure transmission to the microcirculation is augmented, increasing the potential risk of damage to the brain, the heart, and the kidney. Furthermore, elevated pulse pressure exacerbates end-stage renal disease, particularly in older hypertensive individuals. With increasing age, the elastin content of vessel walls declines throughout the arterial network, and arterial stiffening increases further due to the presence of rigid wall material such as collagen, but also fibronectin, proteoglycans, and vascular calcification. Certain genes, mainly related to angiotensin and/or aldosterone, affect this aging process and contribute to the extent of arterial stiffness, which can independently affect both forward and reflected pressure waves.