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

      , 1 , 2 , 3

      BioMedical Engineering OnLine

      BioMed Central

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          Abstract

          Background

          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.

          Methods

          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.

          Results

          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.

          Conclusion

          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.

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          Most cited references 22

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          Wave propagation in a model of the arterial circulation.

          The propagation of the arterial pulse wave in the large systemic arteries has been calculated using a linearised method of characteristics analysis to follow the waves generated by the heart. The model includes anatomical and physiological data for the 55 largest arteries adjusted so that the bifurcating tree of arteries is well matched for forward travelling waves. The peripheral arteries in the model are terminated by resistance elements which are adjusted to produce a physiologically reasonable distribution of mean blood flow. In the model, the pressure and velocity wave generated by the contraction of the left ventricle propagates to the periphery where it is reflected. These reflected waves are re-reflected by each of the bifurcations that they encounter and a very complex pattern of waves is generated. The results of the calculations exhibit many of the features of the systemic arteries, including the increase of the pulse pressure with distance away from the heart as well as the initial decrease and then the large increase in the magnitude of back flow during late systole going from the ascending aorta to the abdominal aorta to the arteries of the leg. The model is then used to study the effects of the reflection or absorption of waves by the heart and the mechanisms leading to the incisura are investigated. Calculations are carried out with the total occlusion of different arterial segments in order to model experiments in which the effects of the occlusion of different arteries on pressure and flow in the ascending aorta were measured. Finally, the effects of changes in peripheral resistance on pressure and velocity waveforms are also studied. We conclude from these calculations that the complex pattern of wave propagation in the large arteries may be the most important determinant of arterial haemodynamics.
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            Stress analysis in a layered aortic arch model under pulsatile blood flow

            Background Many cardiovascular diseases, such as aortic dissection, frequently occur on the aortic arch and fluid-structure interactions play an important role in the cardiovascular system. Mechanical stress is crucial in the functioning of the cardiovascular system; therefore, stress analysis is a useful tool for understanding vascular pathophysiology. The present study is concerned with the stress distribution in a layered aortic arch model with interaction between pulsatile flow and the wall of the blood vessel. Methods A three-dimensional (3D) layered aortic arch model was constructed based on the aortic wall structure and arch shape. The complex mechanical interaction between pulsatile blood flow and wall dynamics in the aortic arch model was simulated by means of computational loose coupling fluid-structure interaction analyses. Results The results showed the variations of mechanical stress along the outer wall of the arch during the cardiac cycle. Variations of circumferential stress are very similar to variations of pressure. Composite stress in the aortic wall plane is high at the ascending portion of the arch and along the top of the arch, and is higher in the media than in the intima and adventitia across the wall thickness. Conclusion Our analysis indicates that circumferential stress in the aortic wall is directly associated with blood pressure, supporting the clinical importance of blood pressure control. High stress in the aortic wall could be a risk factor in aortic dissections. Our numerical layered aortic model may prove useful for biomechanical analyses and for studying the pathogeneses of aortic dissection.
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              Renal artery stenosis and unilateral focal and segmental glomerulosclerosis.

              Focal and segmental sclerosed lesions in the glomeruli are found in several pathological entities and more often are found in the corticomedullary junction where renal blood flow and filtration pressure is maximal. Experimental data suggest that hyperfiltration injury results in focal and segmental glomerulosclerosis (FSGS). In keeping with this concept, malignant hypertension is a known cause of nephrotic-range proteinuria and nephrotic syndrome pathalobically represented by FSGS. We report a case of unilateral renal artery stenosis associated with nephrotic syndrome and FSGS in the contralateral kidney only. The kidney with the stenosed renal artery showed normal glomeruli with juxtaglomerular hyperplasia, suggesting that protection from hyperfiltration injury was provided by the presence of high-grade stenosis. Serum creatinine concentration, blood pressure, and proteinuria normalized after aorto-renal bypass surgery. This case shows the importance of hemodynamic factors on the pathogenesis of secondary FSGS and the progression of renal disease.
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                Author and article information

                Journal
                Biomed Eng Online
                BioMedical Engineering OnLine
                BioMed Central (London )
                1475-925X
                2007
                9 June 2007
                : 6
                : 22
                Affiliations
                [1 ]Biomedical Engineering Department, Amirkabir University, Tehran, Iran
                [2 ]Mechanical Department, Iran University of Science and Technology, Tehran, Iran
                [3 ]Biomedical Engineering Department, Amirkabir University, Tehran, Iran
                Article
                1475-925X-6-22
                10.1186/1475-925X-6-22
                1906784
                17559685
                Copyright © 2007 Hassani et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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                Research

                Biomedical engineering

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