Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system

<p>Abstract</p> <p>Background</p> <p>The aortic aneurysm is a dilatation of the aortic wall which occurs in the saccular and fusiform types. The aortic aneurysms can rupture, if left untreated. The renal stenosis occurs when the flow of blood from the arteries leading to the kidneys is constricted by atherosclerotic plaque. This narrowing may lead to the renal failure. Previous works have shown that, modelling is a useful tool for understanding of cardiovascular system functioning and pathophysiology of the system. The present study is concerned with the modelling of aortic aneurysms and renal artery stenosis using the cardiovascular electronic system.</p> <p>Methods</p> <p>The geometrical models of the aortic aneurysms and renal artery stenosis, with different rates, were constructed based on the original anatomical data. The pressure drop of each section due to the aneurysms or stenosis was computed by means of computational fluid dynamics method. The compliance of each section with the aneurysms or stenosis is also calculated using the mathematical method. An electrical system representing the cardiovascular circulation was used to study the effects of these pressure drops and the compliance variations on this system.</p> <p>Results</p> <p>The results showed the decreasing of pressure along the aorta and renal arteries lengths, due to the aneurysms and stenosis, at the peak systole. The mathematical method demonstrated that compliances of the aorta sections and renal increased with the expansion rate of the aneurysms and stenosis. The results of the modelling, such as electrical pressure graphs, exhibited the features of the pathologies such as hypertension and were compared with the relevant experimental data.</p> <p>Conclusion</p> <p>We conclude from the study that the aortic aneurysms as well as renal artery stenosis may be the most important determinant of the arteries rupture and failure. Furthermore, these pathologies play important rules in increase of the cardiovascular pulse pressure which leads to the hypertension.</p

Combining numerical and clinical methods to assess aortic valve hemodynamics during exercise

Computational simulations have the potential to aid understanding of cardiovascular hemodynamics under physiological conditions, including exercise. Therefore, blood hemodynamic parameters during different heart rates, rest and exercise have been investigated, using a numerical method. A model was developed for a healthy subject. Using geometrical data acquired by echo-Doppler, a two-dimensional model of the chamber of aortic sinus valsalva and aortic root was created. Systolic ventricular and aortic pressures were applied as boundary conditions computationally. These pressures were the initial physical conditions applied to the model to predict valve deformation and changes in hemodynamics. They were the clinically measured brachial pressures plus differences between brachial, central and left ventricular pressures. Echocardiographic imaging was also used to acquire different ejection times, necessary for pressure waveform equations of blood flow during exercise. A fluid-structure interaction simulation was performed, using an arbitrary Lagrangian-Eulerian mesh. During exercise, peak vorticity increased by 14.8%, peak shear rate by 15.8%, peak cell Reynolds number by 20%, peak leaflet tip velocity increased by 47% and the blood velocity increased by 3% through the leaflets, whereas full opening time decreased by 11%. Our results show that numerical methods can be combined with clinical measurements to provide good estimates of patient-specific hemodynamics at different heart rates. </jats:p

Digital Subtraction Phonocardiography (DSP) applied to the detection and characterization of heart murmurs

<p>Abstract</p> <p>Background</p> <p>During the cardiac cycle, the heart normally produces repeatable physiological sounds. However, under pathologic conditions, such as with heart valve stenosis or a ventricular septal defect, blood flow turbulence leads to the production of additional sounds, called murmurs. Murmurs are random in nature, while the underlying heart sounds are not (being deterministic).</p> <p>Innovation</p> <p>We show that a new analytical technique, which we call Digital Subtraction Phonocardiography (DSP), can be used to separate the random murmur component of the phonocardiogram from the underlying deterministic heart sounds.</p> <p>Methods</p> <p>We digitally recorded the phonocardiogram from the anterior chest wall in 60 infants and adults using a high-speed USB interface and the program Gold Wave <url>http://www.goldwave.com</url>. The recordings included individuals with cardiac structural disease as well as recordings from normal individuals and from individuals with innocent heart murmurs. Digital Subtraction Analysis of the signal was performed using a custom computer program called <b>Murmurgram</b>. In essence, this program subtracts the recorded sound from two adjacent cardiac cycles to produce a difference signal, herein called a "murmurgram". Other software used included Spectrogram (Version 16), GoldWave (Version 5.55) as well as custom MATLAB code.</p> <p>Results</p> <p>Our preliminary data is presented as a series of eight cases. These cases show how advanced signal processing techniques can be used to separate heart sounds from murmurs. Note that these results are preliminary in that normal ranges for obtained test results have not yet been established.</p> <p>Conclusions</p> <p>Cardiac murmurs can be separated from underlying deterministic heart sounds using DSP. DSP has the potential to become a reliable and economical new diagnostic approach to screening for structural heart disease. However, DSP must be further evaluated in a large series of patients with well-characterized pathology to determine its clinical potential.</p

Comparison between mechanical properties of human saphenous vein and umbilical vein

<p>Abstract</p> <p>Background</p> <p>As a main cause of mortality in developed countries, Coronary Artery Disease (CAD) is known as silent killer with a considerable cost to be dedicated for its treatment. Coronary Artery Bypass Graft (CABG) is a common remedy for CAD for which different blood vessels are used as a detour. There is a lack of knowledge about mechanical properties of human blood vessels used for CABG, and while these properties have a great impact on long-term patency of a CABG. Thus, studying these properties, especially those of human umbilical veins which have not been considered yet, looks utterly necessary.</p> <p>Methods</p> <p>Umbilical vein, as well as human Saphenous vein, are respectively obtained after cesarean and CABG. First, histological tests were performed to investigate different fiber contents of the samples. Having prepared samples carefully, force-displacement results of samples were rendered to real stress–strain measurements and then a fourth-order polynomial was used to prove the non-linear behavior of these two vessels.</p> <p>Results</p> <p>Results were analyzed in two directions, i.e. circumferentially and longitudinally, which then were compared with each other. The comparison between stiffness and elasticity of these veins showed that Saphenous vein’s stiffness is much higher than that of umbilical vein and also, it is less stretchable. Furthermore, for both vessels, longitudinal stiffness was higher than that of circumferential and in stark contrast, stretch ratio in circumferential direction came much higher than longitudinal orientation.</p> <p>Conclusion</p> <p>Blood pressure is very high in the region of aorta, so there should be a stiff blood vessel in this area and previous investigations showed that stiffer vessels would have a better influence on the flow of bypass. To this end, the current study has made an attempt to compare these two blood vessels’ stiffness, finding that Saphenous vein is stiffer than umbilical vein which is somehow as stiff as rat aortic vessels. As blood vessel’s stiffness is directly related to elastin and mainly collagen content, results showed the lower amount of these two contents in umbilical vein regarding Saphenous vein.</p

Food System Dynamics and Food Insecurity in Humla, Nepal Himalaya

This study examines the challenges underlying food security of the Himalayan smallholder farmers focusing on three interrelated dimensions: the impact of multiple environmental and socio-economic stressors on food system, access to and role of nonfarm income sources, and the role of humanitarian and development interventions on food security and livelihoods. The results suggested that the food systems are driven by synergistic impacts of climate change and changes in forest governance through community forestry (CF) program. The CF regulated the use of forest directly affecting the livestock population. Since livestock is the sole source of soil fertility and the backbone of the traditional salt-grain trade, its population decrease has had direct impact on food production and household income. In addition, decreasing winter precipitation and increasing dry spell synergized the impacts of the CF resulting in negative food production. Adoption of off-farm income activities and utilization of food support from food assistance programs (FAPs) were the main factors that cushioned the farmers&rsquo; food deprivation to some extent. A locally disaggregated analysis revealed that there were high caste/ethnic disparities in food insecurity prevalence as well as the capacity to excel strategies to reduce it. Having too little productive land the low caste Dalits were the most food insecure group of all. Due to their little human, financial and social capital, they also failed to diversify livelihoods into high return sectors to reduce food insecurity as did their high caste counterparts. Moreover, food assistance programs being highly influenced by local politics and power failed to benefit this most food insecure group while the high caste households and those powerful in local politics reaped disproportionately higher amount of food aid. In this context, the Dalits ended up with low return activities, such as providing wage labor to the farms of high castes or serving them with their caste based skills such as smithing or tailoring in a patron-client exchange system. Since the exchange system is controlled by high caste clients, Dalits are kept in dependency, which gets intensified when environmental and socio-economic changes stress their livelihoods. Arguably, caste relation discriminated against some group and resulted into the evolution and persistence of their marginalization and food insecurity and therefore food insecurity is inherently a political problem. The insights provided by this study do not downplay the significance of critical challenges such as climate change impacts on food systems and therefore the need of agricultural production approach to enhance food system resilience. However, the focus only on technical interventions to increase production and the capacity of the production systems to adapt to change do not alter the social and political drivers that make some groups vulnerable to food insecurity. Since local social, political and economic inequities are the primary factors underlying the vulnerability of some groups, social equity should be one of the primary goals of targeted interventions so that they can ensure their ability to enhance food security through farming or through the access to profitable non-farm activities as well as from accessing humanitarian support. Conceptually, this insight corresponds to a recent call made by social scientists to invigorate social-ecological system (SES) approach by giving a stronger emphasis on social factors of system vulnerability, which the conventional SES studies largely lack.</p

Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system-4

<p><b>Copyright information:</b></p><p>Taken from "Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system"</p><p>http://www.biomedical-engineering-online.com/content/6/1/22</p><p>BioMedical Engineering OnLine 2007;6():22-22.</p><p>Published online 9 Jun 2007</p><p>PMCID:PMC1906784.</p><p></p>ned by CFD method. The high pressure (pascal) regions along the artery sections are at the inlet to the middle portion

Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system-7

<p><b>Copyright information:</b></p><p>Taken from "Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system"</p><p>http://www.biomedical-engineering-online.com/content/6/1/22</p><p>BioMedical Engineering OnLine 2007;6():22-22.</p><p>Published online 9 Jun 2007</p><p>PMCID:PMC1906784.</p><p></p>ure(pascal) decreases along the artery length