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

Validation of Objective Structured Clinical Examination (OSCE) based on the Occupational Therapy Practice Framework (OTPF): A pilot study

Fieldwork education is an integral part of the educational process in occupational therapy and assessing student competency at the end of fieldwork is important. The aim of this study was to design and conduct an Objective Structured Clinical Examination (OSCE) based on the Occupational Therapy Practice Framework (OTPF) for occupational therapy students on Level II fieldwork in Iran. A seven-station OSCE was designed and conducted with 13 students. Face and content validity of the exam scenarios and grading checklists was assessed via faculty review. The correlation between scores from each station and total OSCE scores were obtained to assess construct validity. Inter-rater reliability between two independent examiners at each OSCE station was determined. The participants’ (including both students and examiners) reactions to and learning from the exam was assessed using a self-report questionnaire that included participants\u27 attitudes, satisfaction, and emotional response to the OSCE. Finally, a focus group of 12 examiners was conducted to examine the strengths and weaknesses of the exam. It was ascertained that the OSCE had good and acceptable face, content, and construct validity as well as inter-examiner reliability. All students reported that the exam was stressful, and most students (n=8, 61%) and examiners (n=5, 42%) reported there was not enough time for each station. Strength and weaknesses of the exam as related to the exam condition, exam content, students, and examiners were reported. Based on the qualitative and quantitative analysis of the results, in order to use OSCE as a method of evaluating occupational therapy students, some changes should be applied

The study of the relationship between unicuspid aortic valve insufficiency and heart disease by fluid-structure interaction modeling

Unicuspid aortic valve (UAV) is a rare congenital malformation that affects 5% of patients undergoing aortic stenosis surgery. It has two subtypes, acommissural and unicommissural. By computational modeling with the fluid-structure interaction (FSI) method, it is possible to predict diseases related to the unicuspid aortic valve and treat them before they progress. Without it, the cost and time of treatment and the risk of failure increase. Previously, only statistical studies on unicuspid valve patients and diseases caused by it had been conducted. Modeling was performed using information from articles on patients with unicuspid aortic valves. The acommissural type, without lateral slits, had the highest grade of stenosis and the highest potential for aortic dilation compared to unicommissural. In both models, an unusually high-pressure gradient occurred, which caused peak strain on the raphes and edges of the leaflets. The presence of the vortex upstream led to the acceleration and increase of calcification. The findings of this study suggest specific differences in hemodynamic characteristics and valve mechanics for different UAV phenotypes, including the severity of stenosis and leaflet strain, which may be critical for predicting subsequent aortic diseases and differential treatment strategies